U.S. patent application number 15/087101 was filed with the patent office on 2016-11-17 for wireless energy transfer with reduced fields.
The applicant listed for this patent is WiTricity Corporation. Invention is credited to Volkan Efe, Katherine L. Hall, Maria Empar Rollano Hijarrubia, Aristeidis Karalis, Morris P. Kesler, Andre B. Kurs, Alexander P. McCauley, Marin Soljacic, Simon Verghese.
Application Number | 20160336803 15/087101 |
Document ID | / |
Family ID | 48874002 |
Filed Date | 2016-11-17 |
United States Patent
Application |
20160336803 |
Kind Code |
A1 |
Kurs; Andre B. ; et
al. |
November 17, 2016 |
WIRELESS ENERGY TRANSFER WITH REDUCED FIELDS
Abstract
A magnetic resonator includes an inductor comprising a
conductive first loop having a first dipole moment and a conductive
second loop having a second dipole moment wherein a direction of
the first dipole moment is substantially opposite to a direction of
the second dipole moment and at least one capacitor in series with
at least one of the first loop and the second loop.
Inventors: |
Kurs; Andre B.; (Chestnut
Hill, MA) ; Kesler; Morris P.; (Bedford, MA) ;
Hall; Katherine L.; (Arlington, MA) ; Karalis;
Aristeidis; (Boston, MA) ; Verghese; Simon;
(Arlington, MA) ; Efe; Volkan; (Watertown, MA)
; Soljacic; Marin; (Belmont, MA) ; McCauley;
Alexander P.; (Sunnyvale, CA) ; Hijarrubia; Maria
Empar Rollano; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WiTricity Corporation |
Watertown |
MA |
US |
|
|
Family ID: |
48874002 |
Appl. No.: |
15/087101 |
Filed: |
March 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13752169 |
Jan 28, 2013 |
9306635 |
|
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15087101 |
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61590856 |
Jan 26, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 90/14 20130101;
Y02T 10/7072 20130101; H02J 7/342 20200101; H04B 5/0037 20130101;
H04B 5/0075 20130101; B60L 53/12 20190201; H02J 50/90 20160201;
H02J 7/35 20130101; H02J 5/005 20130101; H02J 7/345 20130101; H02J
7/0044 20130101; Y02T 10/70 20130101; H02J 7/025 20130101; H02J
50/20 20160201; H02J 50/12 20160201 |
International
Class: |
H02J 50/12 20060101
H02J050/12; B60L 11/18 20060101 B60L011/18; H02J 7/02 20060101
H02J007/02; H04B 5/00 20060101 H04B005/00 |
Claims
1. A magnetic resonator comprising: an inductor comprising a
conductive first loop having a first dipole moment and a conductive
second loop having a second dipole moment wherein a direction of
the first dipole moment is substantially opposite to a direction of
the second dipole moment; and at least one capacitor in series with
at least one of the first loop and the second loop.
2-20. (canceled)
Description
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 61/590,856 filed Jan. 26, 2012, which
is hereby incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] This disclosure relates to wireless energy transfer,
methods, systems and apparati to accomplish such transfer, and
applications.
[0004] 2. Description of the Related Art
[0005] A need exists for methods and designs for energy
distribution that is wire free but easy to deploy and configurable
while may deliver sufficient power to be practical to power many
household, industrial devices, and commercial devices.
SUMMARY
[0006] Resonators and resonator assemblies may be positioned to
distribute wireless energy over a larger area in packaging
applications. The wireless energy transfer resonators and
components that may be used have been described in, for example, in
commonly owned U.S. patent application Ser. No. 12/789,611
published on Sep. 23, 2010 as U.S. Pat. Pub. No. 2010/0237709 and
entitled "RESONATOR ARRAYS FOR WIRELESS ENERGY TRANSFER," and U.S.
patent application Ser. No. 12/722,050 published on Jul. 22, 2010
as U.S. Pat. Pub. No. 2010/0181843 and entitled "WIRELESS ENERGY
TRANSFER FOR REFRIGERATOR APPLICATION" the contents of which are
incorporated in their entirety as if fully set forth herein.
[0007] Unless otherwise indicated, this disclosure uses the terms
wireless energy transfer, wireless power transfer, wireless power
transmission, and the like, interchangeably. Those skilled in the
art will understand that a variety of system architectures may be
supported by the wide range of wireless system designs and
functionalities described in this application.
[0008] This disclosure references certain individual circuit
components and elements such as capacitors, inductors, resistors,
diodes, transformers, switches and the like; combinations of these
elements as networks, topologies, circuits, and the like; and
objects that have inherent characteristics such as "self-resonant"
objects with capacitance or inductance distributed (or partially
distributed, as opposed to solely lumped) throughout the entire
object. It would be understood by one of ordinary skill in the art
that adjusting and controlling variable components within a circuit
or network may adjust the performance of that circuit or network
and that those adjustments may be described generally as tuning,
adjusting, matching, correcting, and the like. Other methods to
tune or adjust the operating point of the wireless power transfer
system may be used alone, or in addition to adjusting tunable
components such as inductors and capacitors, or banks of inductors
and capacitors. Those skilled in the art will recognize that a
particular topology discussed in this disclosure can be implemented
in a variety of other ways.
[0009] In accordance with an exemplary and non-limiting embodiment,
a magnetic resonator comprises an inductor comprising a conductive
first loop having a first dipole moment and a conductive second
loop having a second dipole moment wherein a direction of the first
dipole moment is substantially opposite to a direction of the
second dipole moment and at least one capacitor in series with at
least one of the first loop and the second loop.
[0010] In accordance with another exemplary and non-limiting
embodiment, a method comprises providing a plurality of conductive
loops each having a dipole moment comprising a magnitude and a
direction and selectively altering at least one dipole moment of at
least one of the plurality of loops to produce a predetermined far
field radiation level.
[0011] In accordance with another exemplary and non-limiting
embodiment, a magnetic resonator comprises a plurality of
conductive loops each having a dipole moment comprising a magnitude
and a direction and a control system for adjusting the dipole
moment of at least one of the plurality of loops to produce a
predetermined far field radiation level.
[0012] In accordance with another exemplary and non-limiting
embodiment, a wireless power source comprises at least one high-Q
magnetic resonator for generating an oscillating magnetic field and
at least one conducting plate positioned substantially
perpendicular to the dipole moment of the resonator.
[0013] In accordance with another exemplary and non-limiting
embodiment, a wireless power device comprises at least one high-Q
magnetic resonator for generating a current in the presence of an
oscillating magnetic field, and at least one conducting plate
positioned substantially perpendicular to the dipole moment of the
resonator.
[0014] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this disclosure belongs. In case
of conflict with publications, patent applications, patents, and
other references mentioned or incorporated herein by reference, the
present specification, including definitions, will control.
[0015] Any of the features described above may be used, alone or in
combination, without departing from the scope of this disclosure.
Other features, objects, and advantages of the systems and methods
disclosed herein will be apparent from the following detailed
description and figures.
BRIEF DESCRIPTION OF FIGURES
[0016] FIG. 1 is a system block diagram of wireless energy transfer
configurations.
[0017] FIGS. 2A-2F are exemplary structures and schematics of
simple resonator structures.
[0018] FIG. 3 is a block diagram of a wireless source with a
single-ended amplifier.
[0019] FIG. 4 is a block diagram of a wireless source with a
differential amplifier.
[0020] FIGS. 5A and 5B are block diagrams of sensing circuits.
[0021] FIGS. 6A, 6B, and 6C are block diagrams of a wireless
source.
[0022] FIG. 7 is a plot showing the effects of a duty cycle on the
parameters of an amplifier.
[0023] FIG. 8 is a simplified circuit diagram of a wireless power
source with a switching amplifier.
[0024] FIG. 9 shows plots of the effects of changes of parameters
of a wireless power source.
[0025] FIG. 10 shows plots of the effects of changes of parameters
of a wireless power source.
[0026] FIGS. 11A, 11B, and 11C are plots showing the effects of
changes of parameters of a wireless power source.
[0027] FIG. 12 shows plots of the effects of changes of parameters
of a wireless power source.
[0028] FIG. 13 is a simplified circuit diagram of a wireless energy
transfer system comprising a wireless power source with a switching
amplifier and a wireless power device.
[0029] FIG. 14 shows plots of the effects of changes of parameters
of a wireless power source.
[0030] FIG. 15A is a plot of wireless power transfer efficiency
between a fixed size device resonator and different sized source
resonators as a function of separation distance and FIG. 15B is a
diagram of the resonator configuration used for generating the
plot.
[0031] FIG. 16A is a plot of wireless power transfer efficiency
between a fixed size device resonator and different sized source
resonators as a function of lateral offset and FIG. 16B is a
diagram of the resonator configuration used for generating the
plot.
[0032] FIG. 17 is a diagram of a conductor arrangement of an
exemplary system embodiment.
[0033] FIG. 18 is a diagram of another conductor arrangement of an
exemplary system embodiment.
[0034] FIG. 19 is a diagram of an exemplary system embodiment of a
source comprising an array of equally sized resonators.
[0035] FIG. 20 is a diagram of an exemplary system embodiment of a
source comprising an array of multi-sized resonators.
[0036] FIG. 21A-21C are diagrams of exemplary embodiments of
adjustable size sources comprising planar resonator structures.
[0037] FIGS. 22A-22D are diagrams showing usage scenarios for an
adjustable source size.
[0038] FIGS. 23A and 23B are diagrams showing two resonator
configurations with repeater resonators.
[0039] FIGS. 24A and 24B are diagrams showing two resonator
configurations with repeater resonators.
[0040] FIG. 25A is a diagram showing a configuration with two
repeater resonators, and
[0041] FIG. 25B is a diagram showing a resonator configuration with
a device resonator acting as a repeater resonator.
[0042] FIG. 26 is a diagram of a system utilizing a repeater
resonator with a desk environment.
[0043] FIG. 27 is a diagram of a system utilizing a resonator that
may be operated in multiple modes.
[0044] FIG. 28 is a circuit block diagram of the power and control
circuitry of a resonator configured to have multiple modes of
operation.
[0045] FIG. 29A is a block diagram of a configuration of a system
utilizing a wireless power converter, and FIG. 29B is a block
diagram of a configuration of a system utilizing a wireless power
converter that may also function as a repeater.
[0046] FIG. 30 is a block diagram showing different configurations
and uses of a wireless power converter.
[0047] FIG. 31A is a block diagram of a wireless power converter
that uses two separate resonators and a AC to DC converter, and
FIG. 31B is a block diagram of a wireless power converter that uses
two separate resonators and an AC to AC converter.
[0048] FIG. 32 is a circuit block diagram of a wireless power
converter utilizing one resonator.
[0049] FIGS. 33A and 33B are circuit diagrams of system
configurations utilizing a wireless power converter with
differently sized resonators.
[0050] FIG. 34A and FIG. 34B are diagrams of embodiments of a
wireless power enabled floor tile.
[0051] FIG. 35 is a block diagram of an embodiment of a wireless
power enabled floor tile.
[0052] FIG. 36 is a diagram of a wireless power enables floor
system.
[0053] FIG. 37 is a diagram of a cuttable sheet of resonators.
[0054] FIG. 38 is a diagram of a quadrupole resonator loop.
[0055] FIG. 39 is a diagram of a quadrupole resonator loop.
[0056] FIG. 40 is a diagram of a system with dipole cancellation
using an additional source resonator.
[0057] FIG. 41 is a diagram of a system with dipole cancellation
using an additional source and device resonator.
[0058] FIG. 42 is a diagram of a resonator with dipole cancellation
using a conductor shield.
[0059] FIG. 43 is a diagram of a system with dipole cancellation
using a repeater resonator.
[0060] FIG. 44 is a diagram of a system with dipole cancellation
using a conducting loop.
[0061] FIG. 45 is a diagram of a system with dipole cancellation
using a conducting loop.
[0062] FIG. 46 is a diagram of a system with dipole
cancellation.
[0063] FIG. 47 is a diagram of a system with dipole
cancellation.
[0064] FIG. 48 is a diagram of a system with dipole
cancellation.
[0065] FIG. 49 is a diagram of a system with dipole
cancellation.
DETAILED DESCRIPTION
[0066] As described above, this disclosure relates to wireless
energy transfer using coupled electromagnetic resonators. However,
such energy transfer is not restricted to electromagnetic
resonators, and the wireless energy transfer systems described
herein are more general and may be implemented using a wide variety
of resonators and resonant objects.
[0067] As those skilled in the art will recognize, important
considerations for resonator-based power transfer include resonator
efficiency and resonator coupling. Extensive discussion of such
issues, e.g., coupled mode theory (CMT), coupling coefficients and
factors, quality factors (also referred to as Q-factors), and
impedance matching is provided, for example, in U.S. patent
application Ser. No. 12/789,611 published on Sep. 23, 2010 as US
20100237709 and entitled "RESONATOR ARRAYS FOR WIRELESS ENERGY
TRANSFER," and U.S. patent application Ser. No. 12/722,050
published on Jul. 22, 2010 as US 20100181843 and entitled "WIRELESS
ENERGY TRANSFER FOR REFRIGERATOR APPLICATION" and incorporated
herein by reference in its entirety as if fully set forth
herein.
[0068] A resonator may be defined as a resonant structure that can
store energy in at least two different forms, and where the stored
energy oscillates between the two forms. The resonant structure
will have a specific oscillation mode with a resonant (modal)
frequency, f, and a resonant (modal) field. The angular resonant
frequency, .omega., may be defined as .omega.=2.pi.f, the resonant
period, T, may be defined as T=1/f=2.pi./.omega., and the resonant
wavelength, .lamda., may be defined as .lamda.=c/f, where c is the
speed of the associated field waves (light, for electromagnetic
resonators). In the absence of loss mechanisms, coupling mechanisms
or external energy supplying or draining mechanisms, the total
amount of energy stored by the resonator, W, would stay fixed, but
the form of the energy would oscillate between the two forms
supported by the resonator, wherein one form would be maximum when
the other is minimum and vice versa.
[0069] For example, a resonator may be constructed such that the
two forms of stored energy are magnetic energy and electric energy.
Further, the resonator may be constructed such that the electric
energy stored by the electric field is primarily confined within
the structure while the magnetic energy stored by the magnetic
field is primarily in the region surrounding the resonator. In
other words, the total electric and magnetic energies would be
equal, but their localization would be different. Using such
structures, energy exchange between at least two structures may be
mediated by the resonant magnetic near-field of the at least two
resonators. These types of resonators may be referred to as
magnetic resonators.
[0070] An important parameter of resonators used in wireless power
transmission systems is the Quality Factor, or Q-factor, or Q, of
the resonator, which characterizes the energy decay and is
inversely proportional to energy losses of the resonator. It may be
defined as Q=.omega.*W/P, where P is the time-averaged power lost
at steady state. That is, a resonator with a high-Q has relatively
low intrinsic losses and can store energy for a relatively long
time. Since the resonator loses energy at its intrinsic decay rate,
2.GAMMA., its Q, also referred to as its intrinsic Q, is given by
Q=.omega./2.GAMMA.. The quality factor also represents the number
of oscillation periods, T, it takes for the energy in the resonator
to decay by a factor of Note that the quality factor or intrinsic
quality factor or Q of the resonator is that due only to intrinsic
loss mechanisms. The Q of a resonator connected to, or coupled to a
power generator, g, or load, l, may be called the "loaded quality
factor" or the "loaded Q". The Q of a resonator in the presence of
an extraneous object that is not intended to be part of the energy
transfer system may be called the "perturbed quality factor" or the
"perturbed Q".
[0071] Resonators, coupled through any portion of their near-fields
may interact and exchange energy. The efficiency of this energy
transfer can be significantly enhanced if the resonators operate at
substantially the same resonant frequency. By way of example, but
not limitation, imagine a source resonator with Q.sub.s and a
device resonator with Q.sub.d. High-Q wireless energy transfer
systems may utilize resonators that are high-Q. The Q of each
resonator may be high. The geometric mean of the resonator Q's,
{square root over (Q.sub.sQ.sub.d)} may also or instead be
high.
[0072] The coupling factor, k, is a number between
0.ltoreq.|k|.ltoreq.1, and it may be independent (or nearly
independent) of the resonant frequencies of the source and device
resonators, when those are placed at sub-wavelength distances.
Rather the coupling factor k may be determined mostly by the
relative geometry and the distance between the source and device
resonators where the physical decay-law of the field mediating
their coupling is taken into account. The coupling coefficient used
in CMT, k=k {square root over (.omega..sub.s.omega..sub.d)}/2, may
be a strong function of the resonant frequencies, as well as other
properties of the resonator structures. In applications for
wireless energy transfer utilizing the near-fields of the
resonators, it is desirable to have the size of the resonator be
much smaller than the resonant wavelength, so that power lost by
radiation is reduced. In some embodiments, high-Q resonators are
sub-wavelength structures. In some electromagnetic embodiments,
high-Q resonator structures are designed to have resonant
frequencies higher than 100 kHz. In other embodiments, the resonant
frequencies may be less than 1 GHz.
[0073] In exemplary embodiments, the power radiated into the
far-field by these sub wavelength resonators may be further reduced
by lowering the resonant frequency of the resonators and the
operating frequency of the system. In other embodiments, the far
field radiation may be reduced by arranging for the far fields of
two or more resonators to interfere destructively in the far
field.
[0074] In a wireless energy transfer system a resonator may be used
as a wireless energy source, a wireless energy capture device, a
repeater or a combination thereof. In embodiments a resonator may
alternate between transferring energy, receiving energy or relaying
energy. In a wireless energy transfer system one or more magnetic
resonators may be coupled to an energy source and be energized to
produce an oscillating magnetic near-field. Other resonators that
are within the oscillating magnetic near-fields may capture these
fields and convert the energy into electrical energy that may be
used to power or charge a load thereby enabling wireless transfer
of useful energy.
[0075] The so-called "useful" energy in a useful energy exchange is
the energy or power that must be delivered to a device in order to
power or charge it at an acceptable rate. The transfer efficiency
that corresponds to a useful energy exchange may be system or
application-dependent. For example, high power vehicle charging
applications that transfer kilowatts of power may need to be at
least 80% efficient in order to supply useful amounts of power
resulting in a useful energy exchange sufficient to recharge a
vehicle battery without significantly heating up various components
of the transfer system. In some consumer electronics applications,
a useful energy exchange may include any energy transfer
efficiencies greater than 10%, or any other amount acceptable to
keep rechargeable batteries "topped off" and running for long
periods of time. In implanted medical device applications, a useful
energy exchange may be any exchange that does not harm the patient
but that extends the life of a battery or wakes up a sensor or
monitor or stimulator. In such applications, 100 mW of power or
less may be useful. In distributed sensing applications, power
transfer of microwatts may be useful, and transfer efficiencies may
be well below 1%.
[0076] A useful energy exchange for wireless energy transfer in a
powering or recharging application may be efficient, highly
efficient, or efficient enough, as long as the wasted energy
levels, heat dissipation, and associated field strengths are within
tolerable limits and are balanced appropriately with related
factors such as cost, weight, size, and the like.
[0077] The resonators may be referred to as source resonators,
device resonators, first resonators, second resonators, repeater
resonators, and the like. Implementations may include three (3) or
more resonators. For example, a single source resonator may
transfer energy to multiple device resonators or multiple devices.
Energy may be transferred from a first device to a second, and then
from the second device to the third, and so forth. Multiple sources
may transfer energy to a single device or to multiple devices
connected to a single device resonator or to multiple devices
connected to multiple device resonators. Resonators may serve
alternately or simultaneously as sources, devices, and/or they may
be used to relay power from a source in one location to a device in
another location. Intermediate electromagnetic resonators may be
used to extend the distance range of wireless energy transfer
systems and/or to generate areas of concentrated magnetic
near-fields. Multiple resonators may be daisy-chained together,
exchanging energy over extended distances and with a wide range of
sources and devices. For example, a source resonator may transfer
power to a device resonator via several repeater resonators. Energy
from a source may be transferred to a first repeater resonator, the
first repeater resonator may transfer the power to a second
repeater resonator and the second to a third and so on until the
final repeater resonator transfers its energy to a device
resonator. In this respect the range or distance of wireless energy
transfer may be extended and/or tailored by adding repeater
resonators. High power levels may be split between multiple
sources, transferred to multiple devices and recombined at a
distant location.
[0078] The resonators may be designed using coupled mode theory
models, circuit models, electromagnetic field models, and the like.
The resonators may be designed to have tunable characteristic
sizes. The resonators may be designed to handle different power
levels. In exemplary embodiments, high power resonators may require
larger conductors and higher current or voltage rated components
than lower power resonators.
[0079] FIG. 1 shows a diagram of exemplary configurations and
arrangements of a wireless energy transfer system. A wireless
energy transfer system may include at least one source resonator
(R1)104 (optionally R6, 112) coupled to an energy source 102 and
optionally a sensor and control unit 108. The energy source may be
a source of any type of energy capable of being converted into
electrical energy that may be used to drive the source resonator
104. The energy source may be a battery, a solar panel, the
electrical mains, a wind or water turbine, an electromagnetic
resonator, a generator, and the like. The electrical energy used to
drive the magnetic resonator is converted into oscillating magnetic
fields by the resonator. The oscillating magnetic fields may be
captured by other resonators which may be device resonators (R2)
106, (R3) 116 that are optionally coupled to an energy drain 110.
The oscillating fields may be optionally coupled to repeater
resonators (R4, R5) that are configured to extend or tailor the
wireless energy transfer region. Device resonators may capture the
magnetic fields in the vicinity of source resonator(s), repeater
resonators and other device resonators and convert them into
electrical energy that may be used by an energy drain. The energy
drain 110 may be an electrical, electronic, mechanical or chemical
device and the like configured to receive electrical energy.
Repeater resonators may capture magnetic fields in the vicinity of
source, device and repeater resonator(s) and may pass the energy on
to other resonators.
[0080] A wireless energy transfer system may comprise a single
source resonator 104 coupled to an energy source 102 and a single
device resonator 106 coupled to an energy drain 110. In embodiments
a wireless energy transfer system may comprise multiple source
resonators coupled to one or more energy sources and may comprise
multiple device resonators coupled to one or more energy
drains.
[0081] In embodiments the energy may be transferred directly
between a source resonator 104 and a device resonator 106. In other
embodiments the energy may be transferred from one or more source
resonators 104, 112 to one or more device resonators 106, 116 via
any number of intermediate resonators which may be device
resonators, source resonators, repeater resonators, and the like.
Energy may be transferred via a network or arrangement of
resonators 114 that may include subnetworks 118, 120 arranged in
any combination of topologies such as token ring, mesh, ad hoc, and
the like.
[0082] In embodiments the wireless energy transfer system may
comprise a centralized sensing and control system 108. In
embodiments parameters of the resonators, energy sources, energy
drains, network topologies, operating parameters, etc. may be
monitored and adjusted from a control processor to meet specific
operating parameters of the system. A central control processor may
adjust parameters of individual components of the system to
optimize global energy transfer efficiency, to optimize the amount
of power transferred, and the like. Other embodiments may be
designed to have a substantially distributed sensing and control
system. Sensing and control may be incorporated into each resonator
or group of resonators, energy sources, energy drains, and the like
and may be configured to adjust the parameters of the individual
components in the group to maximize or minimize the power
delivered, to maximize energy transfer efficiency in that group and
the like.
[0083] In embodiments, components of the wireless energy transfer
system may have wireless or wired data communication links to other
components such as devices, sources, repeaters, power sources,
resonators, and the like and may transmit or receive data that can
be used to enable the distributed or centralized sensing and
control. A wireless communication channel may be separate from the
wireless energy transfer channel, or it may be the same. In one
embodiment the resonators used for power exchange may also be used
to exchange information. In some cases, information may be
exchanged by modulating a component in a source or device circuit
and sensing that change with port parameter or other monitoring
equipment. Resonators may signal each other by tuning, changing,
varying, dithering, and the like, the resonator parameters such as
the impedance of the resonators which may affect the reflected
impedance of other resonators in the system. The systems and
methods described herein may enable the simultaneous transmission
of power and communication signals between resonators in wireless
power transmission systems, or it may enable the transmission of
power and communication signals during different time periods or at
different frequencies using the same magnetic fields that are used
during the wireless energy transfer. In other embodiments wireless
communication may be enabled with a separate wireless communication
channel such as WiFi, Bluetooth, Infrared, NFC, and the like.
[0084] In embodiments, a wireless energy transfer system may
include multiple resonators and overall system performance may be
improved by control of various elements in the system. For example,
devices with lower power requirements may tune their resonant
frequency away from the resonant frequency of a high-power source
that supplies power to devices with higher power requirements. For
another example, devices needing less power may adjust their
rectifier circuits so that they draw less power from the source. In
these ways, low and high power devices may safely operate or charge
from a single high power source. In addition, multiple devices in a
charging zone may find the power available to them regulated
according to any of a variety of consumption control algorithms
such as First-Come-First-Serve, Best Effort, Guaranteed Power, etc.
The power consumption algorithms may be hierarchical in nature,
giving priority to certain users or types of devices, or it may
support any number of users by equally sharing the power that is
available in the source. Power may be shared by any of the
multiplexing techniques described in this disclosure.
[0085] In embodiments electromagnetic resonators may be realized or
implemented using a combination of shapes, structures, and
configurations. Electromagnetic resonators may include an inductive
element, a distributed inductance, or a combination of inductances
with a total inductance, L, and a capacitive element, a distributed
capacitance, or a combination of capacitances, with a total
capacitance, C. A minimal circuit model of an electromagnetic
resonator comprising capacitance, inductance and resistance, is
shown in FIG. 2F. The resonator may include an inductive element
238 and a capacitive element 240. Provided with initial energy,
such as electric field energy stored in the capacitor 240, the
system will oscillate as the capacitor discharges transferring
energy into magnetic field energy stored in the inductor 238 which
in turn transfers energy back into electric field energy stored in
the capacitor 240. Intrinsic losses in these electromagnetic
resonators include losses due to resistance in the inductive and
capacitive elements and to radiation losses, and are represented by
the resistor, R, 242 in FIG. 2F.
[0086] FIG. 2A shows a simplified drawing of an exemplary magnetic
resonator structure. The magnetic resonator may include a loop of
conductor acting as an inductive element 202 and a capacitive
element 204 at the ends of the conductor loop. The inductor 202 and
capacitor 204 of an electromagnetic resonator may be bulk circuit
elements, or the inductance and capacitance may be distributed and
may result from the way the conductors are formed, shaped, or
positioned, in the structure.
[0087] For example, the inductor 202 may be realized by shaping a
conductor to enclose a surface area, as shown in FIG. 2A. This type
of resonator may be referred to as a capacitively-loaded loop
inductor. Note that we may use the terms "loop" or "coil" to
indicate generally a conducting structure (wire, tube, strip,
etc.), enclosing a surface of any shape and dimension, with any
number of turns. In FIG. 2A, the enclosed surface area is circular,
but the surface may be any of a wide variety of other shapes and
sizes and may be designed to achieve certain system performance
specifications. In embodiments the inductance may be realized using
inductor elements, distributed inductance, networks, arrays, series
and parallel combinations of inductors and inductances, and the
like. The inductance may be fixed or variable and may be used to
vary impedance matching as well as resonant frequency operating
conditions.
[0088] There are a variety of ways to realize the capacitance
required to achieve the desired resonant frequency for a resonator
structure. Capacitor plates 204 may be formed and utilized as shown
in FIG. 2A, or the capacitance may be distributed and be realized
between adjacent windings of a multi-loop conductor. The
capacitance may be realized using capacitor elements, distributed
capacitance, networks, arrays, series and parallel combinations of
capacitances, and the like. The capacitance may be fixed or
variable and may be used to vary impedance matching as well as
resonant frequency operating conditions.
[0089] The inductive elements used in magnetic resonators may
contain more than one loop and may spiral inward or outward or up
or down or in some combination of directions. In general, the
magnetic resonators may have a variety of shapes, sizes and number
of turns and they may be composed of a variety of conducing
materials. The conductor 210, for example, may be a wire, a Litz
wire, a ribbon, a pipe, a trace formed from conducting ink, paint,
gels, and the like or from single or multiple traces printed on a
circuit board. An exemplary embodiment of a trace pattern on a
substrate 208 forming inductive loops is depicted in FIG. 2B.
[0090] In embodiments the inductive elements may be formed using
magnetic materials of any size, shape thickness, and the like, and
of materials with a wide range of permeability and loss values.
These magnetic materials may be solid blocks, they may enclose
hollow volumes, they may be formed from many smaller pieces of
magnetic material tiled and or stacked together, and they may be
integrated with conducting sheets or enclosures made from highly
conducting materials. Conductors may be wrapped around the magnetic
materials to generate the magnetic field. These conductors may be
wrapped around one or more than one axis of the structure. Multiple
conductors may be wrapped around the magnetic materials and
combined in parallel, or in series, or via a switch to form
customized near-field patterns and/or to orient the dipole moment
of the structure. Examples of resonators comprising magnetic
material are depicted in FIGS. 2C, 2D, 2E. In FIG. 2D the resonator
comprises loops of conductor 224 wrapped around a core of magnetic
material 222 creating a structure that has a magnetic dipole moment
228 that is parallel to the axis of the loops of the conductor 224.
The resonator may comprise multiple loops of conductor 216, 212
wrapped in orthogonal directions around the magnetic material 214
forming a resonator with a magnetic dipole moment 218, 220 that may
be oriented in more than one direction as depicted in FIG. 2C,
depending on how the conductors are driven.
[0091] An electromagnetic resonator may have a characteristic,
natural, or resonant frequency determined by its physical
properties. This resonant frequency is the frequency at which the
energy stored by the resonator oscillates between that stored by
the electric field, W.sub.E, (W.sub.E=q.sup.2/2 C, where q is the
charge on the capacitor, C) and that stored by the magnetic field,
W.sub.B, (W.sub.B=Li.sup.2/2, where i is the current through the
inductor, L) of the resonator. The frequency at which this energy
is exchanged may be called the characteristic frequency, the
natural frequency, or the resonant frequency of the resonator, and
is given by .omega.,
.omega. = 2 .pi. f = 1 LC . ##EQU00001##
The resonant frequency of the resonator may be changed by tuning
the inductance, L, and/or the capacitance, C, of the resonator. In
one embodiment system parameters are dynamically adjustable or
tunable to achieve as close as possible to optimal operating
conditions. However, based on the discussion above, efficient
enough energy exchange may be realized even if some system
parameters are not variable or components are not capable of
dynamic adjustment.
[0092] In embodiments a resonator may comprise an inductive element
coupled to more than one capacitor arranged in a network of
capacitors and circuit elements. In embodiments the coupled network
of capacitors and circuit elements may be used to define more than
one resonant frequency of the resonator. In embodiments a resonator
may be resonant, or partially resonant, at more than one
frequency.
[0093] In embodiments, a wireless power source may comprise of at
least one resonator coil coupled to a power supply, which may be a
switching amplifier, such as a class-D amplifier or a class-E
amplifier or a combination thereof. In this case, the resonator
coil is effectively a power load to the power supply. In
embodiments, a wireless power device may comprise of at least one
resonator coil coupled to a power load, which may be a switching
rectifier, such as a class-D rectifier or a class-E rectifier or a
combination thereof. In this case, the resonator coil is
effectively a power supply for the power load, and the impedance of
the load directly relates also to the work-drainage rate of the
load from the resonator coil. The efficiency of power transmission
between a power supply and a power load may be impacted by how
closely matched the output impedance of the power source is to the
input impedance of the load. Power may be delivered to the load at
a maximum possible efficiency, when the input impedance of the load
is equal to the complex conjugate of the internal impedance of the
power supply. Designing the power supply or power load impedance to
obtain a maximum power transmission efficiency is often called
"impedance matching", and may also referred to as optimizing the
ratio of useful-to-lost powers in the system. Impedance matching
may be performed by adding networks or sets of elements such as
capacitors, inductors, transformers, switches, resistors, and the
like, to form impedance matching networks between a power supply
and a power load. In embodiments, mechanical adjustments and
changes in element positioning may be used to achieve impedance
matching. For varying loads, the impedance matching network may
include variable components that are dynamically adjusted to ensure
that the impedance at the power supply terminals looking towards
the load and the characteristic impedance of the power supply
remain substantially complex conjugates of each other, even in
dynamic environments and operating scenarios.
[0094] In embodiments, impedance matching may be accomplished by
tuning the duty cycle, and/or the phase, and/or the frequency of
the driving signal of the power supply or by tuning a physical
component within the power supply, such as a capacitor. Such a
tuning mechanism may be advantageous because it may allow impedance
matching between a power supply and a load without the use of a
tunable impedance matching network, or with a simplified tunable
impedance matching network, such as one that has fewer tunable
components for example. In embodiments, tuning the duty cycle,
and/or frequency, and/or phase of the driving signal to a power
supply may yield a dynamic impedance matching system with an
extended tuning range or precision, with higher power, voltage
and/or current capabilities, with faster electronic control, with
fewer external components, and the like.
[0095] In some wireless energy transfer systems the parameters of
the resonator such as the inductance may be affected by
environmental conditions such as surrounding objects, temperature,
orientation, number and position of other resonators and the like.
Changes in operating parameters of the resonators may change
certain system parameters, such as the efficiency of transferred
power in the wireless energy transfer. For example,
high-conductivity materials located near a resonator may shift the
resonant frequency of a resonator and detune it from other resonant
objects. In some embodiments, a resonator feedback mechanism is
employed that corrects its frequency by changing a reactive element
(e.g., an inductive element or capacitive element). In order to
achieve acceptable matching conditions, at least some of the system
parameters may need to be dynamically adjustable or tunable. All
the system parameters may be dynamically adjustable or tunable to
achieve approximately the optimal operating conditions. However,
efficient enough energy exchange may be realized even if all or
some system parameters are not variable. In some examples, at least
some of the devices may not be dynamically adjusted. In some
examples, at least some of the sources may not be dynamically
adjusted. In some examples, at least some of the intermediate
resonators may not be dynamically adjusted. In some examples, none
of the system parameters may be dynamically adjusted.
[0096] In some embodiments changes in parameters of components may
be mitigated by selecting components with characteristics that
change in a complimentary or opposite way or direction when
subjected to differences in operating environment or operating
point. In embodiments, a system may be designed with components,
such as capacitors, that have an opposite dependence or parameter
fluctuation due to temperature, power levels, frequency, and the
like. In some embodiments, the component values as a function of
temperature may be stored in a look-up table in a system
microcontroller and the reading from a temperature sensor may be
used in the system control feedback loop to adjust other parameters
to compensate for the temperature induced component value
changes.
[0097] In some embodiments the changes in parameter values of
components may be compensated with active tuning circuits
comprising tunable components. Circuits that monitor the operating
environment and operating point of components and system may be
integrated in the design. The monitoring circuits may provide the
signals necessary to actively compensate for changes in parameters
of components. For example, a temperature reading may be used to
calculate expected changes in, or to indicate previously measured
values of, capacitance of the system allowing compensation by
switching in other capacitors or tuning capacitors to maintain the
desired capacitance over a range of temperatures. In embodiments,
the RF amplifier switching waveforms may be adjusted to compensate
for component value or load changes in the system. In some
embodiments the changes in parameters of components may be
compensated with active cooling, heating, active environment
conditioning, and the like.
[0098] The parameter measurement circuitry may measure or monitor
certain power, voltage, and current, signals in the system, and
processors or control circuits may adjust certain settings or
operating parameters based on those measurements. In addition the
magnitude and phase of voltage and current signals, and the
magnitude of the power signals, throughout the system may be
accessed to measure or monitor the system performance. The measured
signals referred to throughout this disclosure may be any
combination of port parameter signals, as well as voltage signals,
current signals, power signals, temperatures signals and the like.
These parameters may be measured using analog or digital
techniques, they may be sampled and processed, and they may be
digitized or converted using a number of known analog and digital
processing techniques. In embodiments, preset values of certain
measured quantities are loaded in a system controller or memory
location and used in various feedback and control loops. In
embodiments, any combination of measured, monitored, and/or preset
signals may be used in feedback circuits or systems to control the
operation of the resonators and/or the system.
[0099] Adjustment algorithms may be used to adjust the frequency,
Q, and/or impedance of the magnetic resonators. The algorithms may
take as inputs reference signals related to the degree of deviation
from a desired operating point for the system and may output
correction or control signals related to that deviation that
control variable or tunable elements of the system to bring the
system back towards the desired operating point or points. The
reference signals for the magnetic resonators may be acquired while
the resonators are exchanging power in a wireless power
transmission system, or they may be switched out of the circuit
during system operation. Corrections to the system may be applied
or performed continuously, periodically, upon a threshold crossing,
digitally, using analog methods, and the like.
[0100] In embodiments, lossy extraneous materials and objects may
introduce potential reductions in efficiencies by absorbing the
magnetic and/or electric energy of the resonators of the wireless
power transmission system. Those impacts may be mitigated in
various embodiments by positioning resonators to minimize the
effects of the lossy extraneous materials and objects and by
placing structural field shaping elements (e.g., conductive
structures, plates and sheets, magnetic material structures, plates
and sheets, and combinations thereof) to minimize their effect.
[0101] One way to reduce the impact of lossy materials on a
resonator is to use high-conductivity materials, magnetic
materials, or combinations thereof to shape the resonator fields
such that they avoid the lossy objects. In an exemplary embodiment,
a layered structure of high-conductivity material and magnetic
material may tailor, shape, direct, reorient, etc. the resonator's
electromagnetic fields so that they avoid lossy objects in their
vicinity by deflecting the fields. FIG. 2D shows a top view of a
resonator with a sheet of conductor 226 below the magnetic material
that may used to tailor the fields of the resonator so that they
avoid lossy objects that may be below the sheet of conductor 226.
The layer or sheet of good 226 conductor may comprise any high
conductivity materials such as copper, silver, aluminum, as may be
most appropriate for a given application. In certain embodiments,
the layer or sheet of good conductor is thicker than the skin depth
of the conductor at the resonator operating frequency. The
conductor sheet may be preferably larger than the size of the
resonator, extending beyond the physical extent of the
resonator.
[0102] In environments and systems where the amount of power being
transmitted could present a safety hazard to a person or animal
that may intrude into the active field volume, safety measures may
be included in the system. In embodiments where power levels
require particularized safety measures, the packaging, structure,
materials, and the like of the resonators may be designed to
provide a spacing or "keep away" zone from the conducting loops in
the magnetic resonator. To provide further protection, high-Q
resonators and power and control circuitry may be located in
enclosures that confine high voltages or currents to within the
enclosure, that protect the resonators and electrical components
from weather, moisture, sand, dust, and other external elements, as
well as from impacts, vibrations, scrapes, explosions, and other
types of mechanical shock. Such enclosures call for attention to
various factors such as thermal dissipation to maintain an
acceptable operating temperature range for the electrical
components and the resonator. In embodiments, enclosure may be
constructed of non-lossy materials such as composites, plastics,
wood, concrete, and the like and may be used to provide a minimum
distance from lossy objects to the resonator components. A minimum
separation distance from lossy objects or environments which may
include metal objects, salt water, oil and the like, may improve
the efficiency of wireless energy transfer. In embodiments, a "keep
away" zone may be used to increase the perturbed Q of a resonator
or system of resonators. In embodiments a minimum separation
distance may provide for a more reliable or more constant operating
parameters of the resonators.
[0103] In embodiments, resonators and their respective sensor and
control circuitry may have various levels of integration with other
electronic and control systems and subsystems. In some embodiments
the power and control circuitry and the device resonators are
completely separate modules or enclosures with minimal integration
to existing systems, providing a power output and a control and
diagnostics interface. In some embodiments a device is configured
to house a resonator and circuit assembly in a cavity inside the
enclosure, or integrated into the housing or enclosure of the
device.
[0104] Example Resonator Circuitry
[0105] FIGS. 3 and 4 show high level block diagrams depicting power
generation, monitoring, and control components for exemplary
sources of a wireless energy transfer system. FIG. 3 is a block
diagram of a source comprising a half-bridge switching power
amplifier and some of the associated measurement, tuning, and
control circuitry. FIG. 4 is a block diagram of a source comprising
a full-bridge switching amplifier and some of the associated
measurement, tuning, and control circuitry.
[0106] The half bridge system topology depicted in FIG. 3 may
comprise a processing unit that executes a control algorithm 328.
The processing unit executing a control algorithm 328 may be a
microcontroller, an application specific circuit, a field
programmable gate array, a processor, a digital signal processor,
and the like. The processing unit may be a single device or it may
be a network of devices. The control algorithm may run on any
portion of the processing unit. The algorithm may be customized for
certain applications and may comprise a combination of analog and
digital circuits and signals. The master algorithm may measure and
adjust voltage signals and levels, current signals and levels,
signal phases, digital count settings, and the like.
[0107] The system may comprise an optional source/device and/or
source/other resonator communication controller 332 coupled to
wireless communication circuitry 312. The optional source/device
and/or source/other resonator communication controller 332 may be
part of the same processing unit that executes the master control
algorithm, it may a part or a circuit within a microcontroller 302,
it may be external to the wireless power transmission modules, it
may be substantially similar to communication controllers used in
wire powered or battery powered applications but adapted to include
some new or different functionality to enhance or support wireless
power transmission.
[0108] The system may comprise a PWM generator 306 coupled to at
least two transistor gate drivers 334 and may be controlled by the
control algorithm. The two transistor gate drivers 334 may be
coupled directly or via gate drive transformers to two power
transistors 336 that drive the source resonator coil 344 through
impedance matching network components 342. The power transistors
336 may be coupled and powered with an adjustable DC supply 304 and
the adjustable DC supply 304 may be controlled by a variable bus
voltage, Vbus. The Vbus controller may be controlled by the control
algorithm 328 and may be part of, or integrated into, a
microcontroller 302 or other integrated circuits. The Vbus
controller 326 may control the voltage output of an adjustable DC
supply 304 which may be used to control power output of the
amplifier and power delivered to the resonator coil 344.
[0109] The system may comprise sensing and measurement circuitry
including signal filtering and buffering circuits 318, 320 that may
shape, modify, filter, process, buffer, and the like, signals prior
to their input to processors and/or converters such as analog to
digital converters (ADC) 314, 316, for example. The processors and
converters such as ADCs 314, 316 may be integrated into a
microcontroller 302 or may be separate circuits that may be coupled
to a processing core 330. Based on measured signals, the control
algorithm 328 may generate, limit, initiate, extinguish, control,
adjust, or modify the operation of any of the PWM generator 306,
the communication controller 332, the Vbus control 326, the source
impedance matching controller 338, the filter/buffering elements,
318, 320, the converters, 314, 316, the resonator coil 344, and may
be part of, or integrated into, a microcontroller 302 or a separate
circuit. The impedance matching networks 342 and resonator coils
344 may include electrically controllable, variable, or tunable
components such as capacitors, switches, inductors, and the like,
as described herein, and these components may have their component
values or operating points adjusted according to signals received
from the source impedance matching controller 338. Components may
be tuned to adjust the operation and characteristics of the
resonator including the power delivered to and by the resonator,
the resonant frequency of the resonator, the impedance of the
resonator, the Q of the resonator, and any other coupled systems,
and the like. The resonator may be any type or structure resonator
described herein including a capacitively loaded loop resonator, a
planer resonator comprising a magnetic material or any combination
thereof.
[0110] The full bridge system topology depicted in FIG. 4 may
comprise a processing unit that executes a master control algorithm
328. The processing unit executing the control algorithm 328 may be
a microcontroller, an application specific circuit, a field
programmable gate array, a processor, a digital signal processor,
and the like. The system may comprise a source/device and/or
source/other resonator communication controller 332 coupled to
wireless communication circuitry 312. The source/device and/or
source/other resonator communication controller 332 may be part of
the same processing unit that executes that master control
algorithm, it may a part or a circuit within a microcontroller 302,
it may be external to the wireless power transmission modules, it
may be substantially similar to communication controllers used in
wire powered or battery powered applications but adapted to include
some new or different functionality to enhance or support wireless
power transmission.
[0111] The system may comprise a PWM generator 410 with at least
two outputs coupled to at least four transistor gate drivers 334
that may be controlled by signals generated in a master control
algorithm. The four transistor gate drivers 334 may be coupled to
four power transistors 336 directly or via gate drive transformers
that may drive the source resonator coil 344 through impedance
matching networks 342. The power transistors 336 may be coupled and
powered with an adjustable DC supply 304 and the adjustable DC
supply 304 may be controlled by a Vbus controller 326 which may be
controlled by a master control algorithm. The Vbus controller 326
may control the voltage output of the adjustable DC supply 304
which may be used to control power output of the amplifier and
power delivered to the resonator coil 344.
[0112] The system may comprise sensing and measurement circuitry
including signal filtering and buffering circuits 318, 320 and
differential/single ended conversion circuitry 402, 404 that may
shape, modify, filter, process, buffer, and the like, signals prior
to being input to processors and/or converters such as analog to
digital converters (ADC) 314, 316. The processors and/or converters
such as ADC 314, 316 may be integrated into a microcontroller 302
or may be separate circuits that may be coupled to a processing
core 330. Based on measured signals, the master control algorithm
may generate, limit, initiate, extinguish, control, adjust, or
modify the operation of any of the PWM generator 410, the
communication controller 332, the Vbus controller 326, the source
impedance matching controller 338, the filter/buffering elements,
318, 320, differential/single ended conversion circuitry 402, 404,
the converters, 314, 316, the resonator coil 344, and may be part
of or integrated into a microcontroller 302 or a separate
circuit.
[0113] Impedance matching networks 342 and resonator coils 344 may
comprise electrically controllable, variable, or tunable components
such as capacitors, switches, inductors, and the like, as described
herein, and these components may have their component values or
operating points adjusted according to signals received from the
source impedance matching controller 338. Components may be tuned
to enable tuning of the operation and characteristics of the
resonator including the power delivered to and by the resonator,
the resonant frequency of the resonator, the impedance of the
resonator, the Q of the resonator, and any other coupled systems,
and the like. The resonator may be any type or structure resonator
described herein including a capacitively loaded loop resonator, a
planar resonator comprising a magnetic material or any combination
thereof.
[0114] Impedance matching networks may comprise fixed value
components such as capacitors, inductors, and networks of
components as described herein. Parts of the impedance matching
networks, A, B and C, may comprise inductors, capacitors,
transformers, and series and parallel combinations of such
components, as described herein. In some embodiments, parts of the
impedance matching networks A, B, and C, may be empty
(short-circuited). In some embodiments, part B comprises a series
combination of an inductor and a capacitor, and part C is
empty.
[0115] The full bridge topology may allow operation at higher
output power levels using the same DC bus voltage as an equivalent
half bridge amplifier. The half bridge exemplary topology of FIG. 3
may provide a single-ended drive signal, while the exemplary full
bridge topology of FIG. 4 may provide a differential drive to the
source resonator 308. The impedance matching topologies and
components and the resonator structure may be different for the two
systems, as discussed herein.
[0116] The exemplary systems depicted in FIGS. 3 and 4 may further
include fault detection circuitry 340 that may be used to trigger
the shutdown of the microcontroller in the source amplifier or to
change or interrupt the operation of the amplifier. This protection
circuitry may comprise a high speed comparator or comparators to
monitor the amplifier return current, the amplifier bus voltage
(Vbus) from the DC supply 304, the voltage across the source
resonator 308 and/or the optional tuning board, or any other
voltage or current signals that may cause damage to components in
the system or may yield undesirable operating conditions. Preferred
embodiments may depend on the potentially undesirable operating
modes associated with different applications. In some embodiments,
protection circuitry may not be implemented or circuits may not be
populated. In some embodiments, system and component protection may
be implemented as part of a master control algorithm and other
system monitoring and control circuits. In embodiments, dedicated
fault circuitry 340 may include an output (not shown) coupled to a
master control algorithm 328 that may trigger a system shutdown, a
reduction of the output power (e.g. reduction of Vbus), a change to
the PWM generator, a change in the operating frequency, a change to
a tuning element, or any other reasonable action that may be
implemented by the control algorithm 328 to adjust the operating
point mode, improve system performance, and/or provide
protection.
[0117] As described herein, sources in wireless power transfer
systems may use a measurement of the input impedance of the
impedance matching network 342 driving source resonator coil 344 as
an error or control signal for a system control loop that may be
part of the master control algorithm. In exemplary embodiments,
variations in any combination of three parameters may be used to
tune the wireless power source to compensate for changes in
environmental conditions, for changes in coupling, for changes in
device power demand, for changes in module, circuit, component or
subsystem performance, for an increase or decrease in the number or
sources, devices, or repeaters in the system, for user initiated
changes, and the like. In exemplary embodiments, changes to the
amplifier duty cycle, to the component values of the variable
electrical components such as variable capacitors and inductors,
and to the DC bus voltage may be used to change the operating point
or operating range of the wireless source and improve some system
operating value. The specifics of the control algorithms employed
for different applications may vary depending on the desired system
performance and behavior.
[0118] Impedance measurement circuitry such as described herein,
and shown in FIGS. 3 and 4, may be implemented using two-channel
simultaneous sampling ADCs and these ADCs may be integrated into a
microcontroller chip or may be part of a separate circuit.
Simultaneously sampling of the voltage and current signals at the
input to a source resonator's impedance matching network and/or the
source resonator, may yield the phase and magnitude information of
the current and voltage signals and may be processed using known
signal processing techniques to yield complex impedance parameters.
In some embodiments, monitoring only the voltage signals or only
the current signals may be sufficient.
[0119] The impedance measurements described herein may use direct
sampling methods which may be relatively simpler than some other
known sampling methods. In embodiments, measured voltage and
current signals may be conditioned, filtered and scaled by
filtering/buffering circuitry before being input to ADCs. In
embodiments, the filter/buffering circuitry may be adjustable to
work at a variety of signal levels and frequencies, and circuit
parameters such as filter shapes and widths may be adjusted
manually, electronically, automatically, in response to a control
signal, by the master control algorithm, and the like. Exemplary
embodiments of filter/buffering circuits are shown in FIGS. 3, 4,
and 5.
[0120] FIG. 5 shows more detailed views of exemplary circuit
components that may be used in filter/buffering circuitry. In
embodiments, and depending on the types of ADCs used in the system
designs, single-ended amplifier topologies may reduce the
complexity of the analog signal measurement paths used to
characterize system, subsystem, module and/or component performance
by eliminating the need for hardware to convert from differential
to single-ended signal formats. In other implementations,
differential signal formats may be preferable. The implementations
shown in FIG. 5 are exemplary, and should not be construed to be
the only possible way to implement the functionality described
herein. Rather it should be understood that the analog signal path
may employ components with different input requirements and hence
may have different signal path architectures.
[0121] In both the single ended and differential amplifier
topologies, the input current to the impedance matching networks
342 driving the resonator coils 344 may be obtained by measuring
the voltage across a capacitor 324, or via a current sensor of some
type. For the exemplary single-ended amplifier topology in FIG. 3,
the current may be sensed on the ground return path from the
impedance matching network 342. For the exemplary differential
power amplifier depicted in FIG. 4, the input current to the
impedance matching networks 342 driving the resonator coils 344 may
be measured using a differential amplifier across the terminals of
a capacitor 324 or via a current sensor of some type. In the
differential topology of FIG. 4, the capacitor 324 may be
duplicated at the negative output terminal of the source power
amplifier.
[0122] In both topologies, after single ended signals representing
the input voltage and current to the source resonator and impedance
matching network are obtained, the signals may be filtered 502 to
obtain the desired portions of the signal waveforms. In
embodiments, the signals may be filtered to obtain the fundamental
component of the signals. In embodiments, the type of filtering
performed, such as low pass, bandpass, notch, and the like, as well
as the filter topology used, such as elliptical, Chebyshev,
Butterworth, and the like, may depend on the specific requirements
of the system. In some embodiments, no filtering will be
required.
[0123] The voltage and current signals may be amplified by an
optional amplifier 504. The gain of the optional amplifier 504 may
be fixed or variable. The gain of the amplifier may be controlled
manually, electronically, automatically, in response to a control
signal, and the like. The gain of the amplifier may be adjusted in
a feedback loop, in response to a control algorithm, by the master
control algorithm, and the like. In embodiments, required
performance specifications for the amplifier may depend on signal
strength and desired measurement accuracy, and may be different for
different application scenarios and control algorithms.
[0124] The measured analog signals may have a DC offset added to
them, 506, which may be required to bring the signals into the
input voltage range of the ADC which for some systems may be 0 to
3.3V. In some systems this stage may not be required, depending on
the specifications of the particular ADC used.
[0125] As described above, the efficiency of power transmission
between a power generator and a power load may be impacted by how
closely matched the output impedance of the generator is to the
input impedance of the load. In an exemplary system as shown in
FIG. 6A, power may be delivered to the load at a maximum possible
efficiency, when the input impedance of the load 604 is equal to
the complex conjugate of the internal impedance of the power
generator or the power amplifier 602. Designing the generator or
load impedance to obtain a high and/or maximum power transmission
efficiency may be called "impedance matching". Impedance matching
may be performed by inserting appropriate networks or sets of
elements such as capacitors, resistors, inductors, transformers,
switches and the like, to form an impedance matching network 606,
between a power generator 602 and a power load 604 as shown in FIG.
6B. In other embodiments, mechanical adjustments and changes in
element positioning may be used to achieve impedance matching. As
described above for varying loads, the impedance matching network
606 may include variable components that are dynamically adjusted
to ensure that the impedance at the generator terminals looking
towards the load and the characteristic impedance of the generator
remain substantially complex conjugates of each other, even in
dynamic environments and operating scenarios. In embodiments,
dynamic impedance matching may be accomplished by tuning the duty
cycle, and/or the phase, and/or the frequency of the driving signal
of the power generator or by tuning a physical component within the
power generator, such as a capacitor, as depicted in FIG. 6C. Such
a tuning mechanism may be advantageous because it may allow
impedance matching between a power generator 608 and a load without
the use of a tunable impedance matching network, or with a
simplified tunable impedance matching network 606, such as one that
has fewer tunable components for example. In embodiments, tuning
the duty cycle, and/or frequency, and/or phase of the driving
signal to a power generator may yield a dynamic impedance matching
system with an extended tuning range or precision, with higher
power, voltage and/or current capabilities, with faster electronic
control, with fewer external components, and the like. The
impedance matching methods, architectures, algorithms, protocols,
circuits, measurements, controls, and the like, described below,
may be useful in systems where power generators drive high-Q
magnetic resonators and in high-Q wireless power transmission
systems as described herein. In wireless power transfer systems a
power generator may be a power amplifier driving a resonator,
sometimes referred to as a source resonator, which may be a load to
the power amplifier. In wireless power applications, it may be
preferable to control the impedance matching between a power
amplifier and a resonator load to control the efficiency of the
power delivery from the power amplifier to the resonator. The
impedance matching may be accomplished, or accomplished in part, by
tuning or adjusting the duty cycle, and/or the phase, and/or the
frequency of the driving signal of the power amplifier that drives
the resonator.
[0126] Efficiency of Switching Amplifiers
[0127] Switching amplifiers, such as class D, E, F amplifiers, and
the like or any combinations thereof, deliver power to a load at a
maximum efficiency when almost no power is dissipated on the
switching elements of the amplifier. This operating condition may
be accomplished by designing the system so that the switching
operations which are most critical (namely those that are most
likely to lead to switching losses) are done when either or both of
the voltage across the switching element and the current through
the switching element are nearly zero. These conditions may be
referred to as Zero Voltage Switching (ZVS) and Zero Current
Switching (ZCS) conditions respectively. When an amplifier operates
at ZVS and/or ZCS either the voltage across the switching element
or the current through the switching element is zero and thus no
power can be dissipated in the switch. Since a switching amplifier
may convert DC (or very low frequency AC) power to AC power at a
specific frequency or range of frequencies, a filter may be
introduced before the load to prevent unwanted harmonics that may
be generated by the switching process from reaching the load and
being dissipated there. In embodiments, a switching amplifier may
be designed to operate at maximum efficiency of power conversion,
when connected to a resonant load, with a quality factor (say
Q>5), and of a specific impedance Z.sub.o*=R.sub.o+jX.sub.o,
which leads to simultaneous ZVS and ZCS. We define
Z.sub.o=R.sub.o-jX.sub.o as the characteristic impedance of the
amplifier, so that achieving maximum power transmission efficiency
is equivalent to impedance matching the resonant load to the
characteristic impedance of the amplifier.
[0128] In a switching amplifier, the switching frequency of the
switching elements, f.sub.switch, wherein
f.sub.switch=.omega./2.pi. and the duty cycle, dc, of the ON
switch-state duration of the switching elements may be the same for
all switching elements of the amplifier. In this specification, we
will use the term "class D" to denote both class D and class DE
amplifiers, that is, switching amplifiers with dc<=50%.
[0129] The value of the characteristic impedance of the amplifier
may depend on the operating frequency, the amplifier topology, and
the switching sequence of the switching elements. In some
embodiments, the switching amplifier may be a half-bridge topology
and, in some embodiments, a full-bridge topology. In some
embodiments, the switching amplifier may be class D and, in some
embodiments, class E. In any of the above embodiments, assuming the
elements of the bridge are symmetric, the characteristic impedance
of the switching amplifier has the form
R.sub.o=F.sub.R(dc)/.omega.C.sub.a,X.sub.o=F.sub.X(dc)/.omega.C.sub.a,
(1)
where dc is the duty cycle of ON switch-state of the switching
elements, the functions F.sub.R(dc) and F.sub.X(dc) are plotted in
FIG. 7 (both for class D and E), .omega. is the frequency at which
the switching elements are switched, and
C.sub.a=n.sub.aC.sub.switch where C.sub.switch is the capacitance
across each switch, including both the transistor output
capacitance and also possible external capacitors placed in
parallel with the switch, while n.sub.a=1 for a full bridge and
n.sub.a=2 for a half bridge. For class D, one can also write the
analytical expressions
F.sub.R(dc)=sin.sup.2u/.pi.,F.sub.X(dc)=(u-sin u*cos u)/.pi.,
(2)
where u=.pi.(1-2*dc), indicating that the characteristic impedance
level of a class D amplifier decreases as the duty cycle, dc,
increases towards 50%. For a class D amplifier operation with
dc=50%, achieving ZVS and ZCS is possible only when the switching
elements have practically no output capacitance (C.sub.a=0) and the
load is exactly on resonance (X.sub.o=0), while R.sub.o can be
arbitrary.
[0130] Impedance Matching Networks
[0131] In applications, the driven load may have impedance that is
very different from the characteristic impedance of the external
driving circuit, to which it is connected. Furthermore, the driven
load may not be a resonant network. An Impedance Matching Network
(IMN) is a circuit network that may be connected before a load as
in FIG. 6B, in order to regulate the impedance that is seen at the
input of the network consisting of the IMN circuit and the load. An
IMN circuit may typically achieve this regulation by creating a
resonance close to the driving frequency. Since such an IMN circuit
accomplishes all conditions needed to maximize the power
transmission efficiency from the generator to the load (resonance
and impedance matching-ZVS and ZCS for a switching amplifier), in
embodiments, an IMN circuit may be used between the driving circuit
and the load.
[0132] For an arrangement shown in FIG. 6B, let the input impedance
of the network consisting of the Impedance Matching Network (IMN)
circuit and the load (denoted together from now on as IMN+load) be
Z.sub.l=R.sub.l(.omega.)+jX.sub.l(.omega.). The impedance matching
conditions of this network to the external circuit with
characteristic impedance Z.sub.o=R.sub.o-jX.sub.o are then
R.sub.l(.omega.)=R.sub.o, X.sub.l(.omega.)=X.sub.o.
[0133] Methods for Tunable Impedance Matching of a Variable
Load
[0134] In embodiments where the load may be variable, impedance
matching between the load and the external driving circuit, such as
a linear or switching power amplifier, may be achieved by using
adjustable/tunable components in the IMN circuit that may be
adjusted to match the varying load to the fixed characteristic
impedance Z.sub.o of the external circuit (FIG. 6B). To match both
the real and imaginary parts of the impedance two tunable/variable
elements in the IMN circuit may be needed.
[0135] In embodiments, the load may be inductive (such as a
resonator coil) with impedance R+jwL, so the two tunable elements
in the IMN circuit may be two tunable capacitance networks or one
tunable capacitance network and one tunable inductance network or
one tunable capacitance network and one tunable mutual inductance
network.
[0136] In embodiments where the load may be variable, the impedance
matching between the load and the driving circuit, such as a linear
or switching power amplifier, may be achieved by using
adjustable/tunable components or parameters in the amplifier
circuit that may be adjusted to match the characteristic impedance
Zo of the amplifier to the varying (due to load variations) input
impedance of the network consisting of the IMN circuit and the load
(IMN+load), where the IMN circuit may also be tunable (FIG. 6C). To
match both the real and imaginary parts of the impedance, a total
of two tunable/variable elements or parameters in the amplifier and
the IMN circuit may be needed. The disclosed impedance matching
method can reduce the required number of tunable/variable elements
in the IMN circuit or even completely eliminate the requirement for
tunable/variable elements in the IMN circuit. In some examples, one
tunable element in the power amplifier and one tunable element in
the IMN circuit may be used. In some examples, two tunable elements
in the power amplifier and no tunable element in the IMN circuit
may be used.
[0137] In embodiments, the tunable elements or parameters in the
power amplifier may be the frequency, amplitude, phase, waveform,
duty cycle and the like of the drive signals applied to
transistors, switches, diodes and the like.
[0138] In embodiments, the power amplifier with tunable
characteristic impedance may be a tunable switching amplifier of
class D, E, F or any combinations thereof. Combining Equations (1)
and (2), the impedance matching conditions for this network are
R.sub.l(.omega.)=F.sub.R(dc)/.omega.C.sub.a,X.sub.l(.omega.)F.sub.X(dc)/-
.omega.C.sub.a (3).
[0139] In some examples of a tunable switching amplifier, one
tunable element may be the capacitance C.sub.a, which may be tuned
by tuning the external capacitors placed in parallel with the
switching elements.
[0140] In some examples of a tunable switching amplifier, one
tunable element may be the duty cycle dc of the ON switch-state of
the switching elements of the amplifier. Adjusting the duty cycle,
dc, via Pulse Width Modulation (PWM) has been used in switching
amplifiers to achieve output power control. In this specification,
we disclose that PWM may also be used to achieve impedance
matching, namely to satisfy Eqs.(3), and thus maximize the
amplifier efficiency.
[0141] In some examples of a tunable switching amplifier one
tunable element may be the switching frequency, which is also the
driving frequency of the IMN+load network and may be designed to be
substantially close to the resonant frequency of the IMN+load
network. Tuning the switching frequency may change the
characteristic impedance of the amplifier and the impedance of the
IMN+load network. The switching frequency of the amplifier may be
tuned appropriately together with one more tunable parameters, so
that Eqs.(3) are satisfied.
[0142] A benefit of tuning the duty cycle and/or the driving
frequency of the amplifier for dynamic impedance matching is that
these parameters can be tuned electronically, quickly, and over a
broad range. In contrast, for example, a tunable capacitor that can
sustain a large voltage and has a large enough tunable range and
quality factor may be expensive, slow or unavailable for with the
necessary component specifications
[0143] Examples of Methods for Tunable Impedance Matching of a
Variable Load
[0144] A simplified circuit diagram showing the circuit level
structure of a class D power amplifier 802, impedance matching
network 804 and an inductive load 806 is shown in FIG. 8. The
diagram shows the basic components of the system with the switching
amplifier 804 comprising a power source 810, switching elements
808, and capacitors. The impedance matching network 804 comprising
inductors and capacitors, and the load 806 modeled as an inductor
and a resistor.
[0145] An exemplary embodiment of this inventive tuning scheme
comprises a half-bridge class-D amplifier operating at switching
frequency f and driving a low-loss inductive element R+j.omega.L
via an IMN, as shown in FIG. 8.
[0146] In some embodiments L' may be tunable. L' may be tuned by a
variable tapping point on the inductor or by connecting a tunable
capacitor in series or in parallel to the inductor. In some
embodiments C.sub.a may be tunable. For the half bridge topology,
C.sub.a may be tuned by varying either one or both capacitors
C.sub.switch, as only the parallel sum of these capacitors matters
for the amplifier operation. For the full bridge topology, C.sub.a
may be tuned by varying either one, two, three or all capacitors
C.sub.switch, as only their combination (series sum of the two
parallel sums associated with the two halves of the bridge) matters
for the amplifier operation.
[0147] In some embodiments of tunable impedance matching, two of
the components of the IMN may be tunable. In some embodiments, L'
and C.sub.2 may be tuned. Then, FIG. 9 shows the values of the two
tunable components needed to achieve impedance matching as
functions of the varying R and L of the inductive element, and the
associated variation of the output power (at given DC bus voltage)
of the amplifier, for f=250 kHz, dc=40%, C.sub.a=640 pF and
C.sub.1=10 nF. Since the IMN always adjusts to the fixed
characteristic impedance of the amplifier, the output power is
always constant as the inductive element is varying.
[0148] In some embodiments of tunable impedance matching, elements
in the switching amplifier may also be tunable. In some embodiments
the capacitance C.sub.a along with the IMN capacitor C.sub.2 may be
tuned. Then, FIG. 10 shows the values of the two tunable components
needed to achieve impedance matching as functions of the varying R
and L of the inductive element, and the associated variation of the
output power (at given DC bus voltage) of the amplifier for f=250
kHz, dc=40%, C.sub.1=10 nF and .omega.L'=1000.OMEGA.. It can be
inferred from FIG. 10 that C.sub.2 needs to be tuned mainly in
response to variations in L and that the output power decreases as
R increases.
[0149] In some embodiments of tunable impedance matching, the duty
cycle dc along with the IMN capacitor C.sub.2 may be tuned. Then,
FIG. 11 shows the values of the two tunable parameters needed to
achieve impedance matching as functions of the varying R and L of
the inductive element, and the associated variation of the output
power (at given DC bus voltage) of the amplifier for f=250 kHz,
C.sub.a=640 pF, C.sub.1=10 nF and .omega.L'=1000.OMEGA.. It can be
inferred from FIG. 11 that C.sub.2 needs to be tuned mainly in
response to variations in L and that the output power decreases as
R increases.
[0150] In some embodiments of tunable impedance matching, the
capacitance C.sub.a along with the IMN inductor L' may be tuned.
Then, FIG. 11A shows the values of the two tunable components
needed to achieve impedance matching as functions of the varying R
of the inductive element, and the associated variation of the
output power (at given DC bus voltage) of the amplifier for f=250
kHz, dc=40%, C.sub.1=10 nF and C.sub.2=7.5 nF. It can be inferred
from FIG. 11A that the output power decreases as R increases.
[0151] In some embodiments of tunable impedance matching, the duty
cycle dc along with the IMN inductor L' may be tuned. Then, FIG.
11B shows the values of the two tunable parameters needed to
achieve impedance matching as functions of the varying R of the
inductive element, and the associated variation of the output power
(at given DC bus voltage) of the amplifier for f=250 kHz,
C.sub.a=640 pF, C.sub.1=10 nF and C.sub.2=7.5 nF as functions of
the varying R of the inductive element. It can be inferred from
FIG. 11B that the output power decreases as R increases.
[0152] In some embodiments of tunable impedance matching, only
elements in the switching amplifier may be tunable with no tunable
elements in the IMN. In some embodiments the duty cycle dc along
with the capacitance C.sub.a may be tuned. Then, FIG. 11C, shows
the values of the two tunable parameters needed to achieve
impedance matching as functions of the varying R of the inductive
element, and the associated variation of the output power (at given
DC bus voltage) of the amplifier for f=250 kHz, C.sub.1=10 nF,
C.sub.2=7.5 nF and .omega.L'=1000.OMEGA.. It can be inferred from
FIG. 11C that the output power is a non-monotonic function of R.
These embodiments may be able to achieve dynamic impedance matching
when variations in L (and thus the resonant frequency) are
modest.
[0153] In some embodiments, dynamic impedance matching with fixed
elements inside the IMN, also when L is varying greatly as
explained earlier, may be achieved by varying the driving frequency
of the external frequency f (e.g. the switching frequency of a
switching amplifier) so that it follows the varying resonant
frequency of the resonator. Using the switching frequency f and the
switch duty cycle dc as the two variable parameters, full impedance
matching can be achieved as R and L are varying without the need of
any variable components. Then, FIG. 12 shows the values of the two
tunable parameters needed to achieve impedance matching as
functions of the varying R and L of the inductive element, and the
associated variation of the output power (at given DC bus voltage)
of the amplifier for C.sub.a=640 pF, C.sub.1=10 nF, C.sub.2=7.5 nF
and L'=637 .mu.H. It can be inferred from FIG. 12 that the
frequency f needs to be tuned mainly in response to variations in
L, as explained earlier.
[0154] Tunable Impedance Matching for Systems of Wireless Power
Transmission
[0155] In applications of wireless power transfer the low-loss
inductive element may be the coil of a source resonator coupled to
one or more device resonators or other resonators, such as repeater
resonators, for example. The impedance of the inductive element
R+jwL may include the reflected impedances of the other resonators
on the coil of the source resonator. Variations of R and L of the
inductive element may occur due to external perturbations in the
vicinity of the source resonator and/or the other resonators or
thermal drift of components. Variations of R and L of the inductive
element may also occur during normal use of the wireless power
transmission system due to relative motion of the devices and other
resonators with respect to the source. The relative motion of these
devices and other resonators with respect to the source, or
relative motion or position of other sources, may lead to varying
coupling (and thus varying reflected impedances) of the devices to
the source. Furthermore, variations of R and L of the inductive
element may also occur during normal use of the wireless power
transmission system due to changes within the other coupled
resonators, such as changes in the power draw of their loads. All
the methods and embodiments disclosed so far apply also to this
case in order to achieve dynamic impedance matching of this
inductive element to the external circuit driving it.
[0156] To demonstrate the presently disclosed dynamic impedance
matching methods for a wireless power transmission system, consider
a source resonator including a low-loss source coil, which is
inductively coupled to the device coil of a device resonator
driving a resistive load.
[0157] In some embodiments, dynamic impedance matching may be
achieved at the source circuit. In some embodiments, dynamic
impedance matching may also be achieved at the device circuit. When
full impedance matching is obtained (both at the source and the
device), the effective resistance of the source inductive element
(namely the resistance of the source coil R.sub.s plus the
reflected impedance from the device) is R=R.sub.s {square root over
(1+U.sub.sd.sup.2)}. (Similarly the effective resistance of the
device inductive element is R.sub.d {square root over
(1+U.sub.sd.sup.2)}, where R.sub.d is the resistance of the device
coil.) Dynamic variation of the mutual inductance between the coils
due to motion results in a dynamic variation of
U.sub.sd=.omega.M.sub.sd/ {square root over (R.sub.sR.sub.d)}.
Therefore, when both source and device are dynamically tuned, the
variation of mutual inductance is seen from the source circuit side
as a variation in the source inductive element resistance R. Note
that in this type of variation, the resonant frequencies of the
resonators may not change substantially, since L may not be
changing. Therefore, all the methods and examples presented for
dynamic impedance matching may be used for the source circuit of
the wireless power transmission system.
[0158] Note that, since the resistance R represents both the source
coil and the reflected impedances of the device coils to the source
coil, in FIGS. 9-12, as R increases due to the increasing U, the
associated wireless power transmission efficiency increases. In
some embodiments, an approximately constant power may be required
at the load driven by the device circuitry. To achieve a constant
level of power transmitted to the device, the required output power
of the source circuit may need to decrease as U increases. If
dynamic impedance matching is achieved via tuning some of the
amplifier parameters, the output power of the amplifier may vary
accordingly. In some embodiments, the automatic variation of the
output power is preferred to be monotonically decreasing with R, so
that it matches the constant device power requirement. In
embodiments where the output power level is accomplished by
adjusting the DC driving voltage of the power generator, using an
impedance matching set of tunable parameters which leads to
monotonically decreasing output power vs. R will imply that
constant power can be kept at the power load in the device with
only a moderate adjustment of the DC driving voltage. In
embodiments, where the "knob" to adjust the output power level is
the duty cycle dc or the phase of a switching amplifier or a
component inside an Impedance Matching Network, using an impedance
matching set of tunable parameters which leads to monotonically
decreasing output power vs. R will imply that constant power can be
kept at the power load in the device with only a moderate
adjustment of this power "knob".
[0159] In the examples of FIGS. 9-12, if R.sub.s=0.19.OMEGA., then
the range R=0.2-2.OMEGA. corresponds approximately to
U.sub.sd=0.3-10.5. For these values, in FIG. 14, we show with
dashed lines the output power (normalized to DC voltage squared)
required to keep a constant power level at the load, when both
source and device are dynamically impedance matched. The similar
trend between the solid and dashed lines explains why a set of
tunable parameters with such a variation of output power may be
preferable.
[0160] In some embodiments, dynamic impedance matching may be
achieved at the source circuit, but impedance matching may not be
achieved or may only partially be achieved at the device circuit.
As the mutual inductance between the source and device coils
varies, the varying reflected impedance of the device to the source
may result in a variation of both the effective resistance R and
the effective inductance L of the source inductive element. The
methods presented so far for dynamic impedance matching are
applicable and can be used for the tunable source circuit of the
wireless power transmission system.
[0161] As an example, consider the circuit of FIG. 14, where f=250
kHz, C.sub.a=640 pF, R.sub.s=0.19.OMEGA., L.sub.s=100 .mu.H,
C.sub.1s=10 nF, .omega.L.sub.s=1000.OMEGA., R.sub.d=0.3.OMEGA.,
L.sub.d=40 .mu.H, C.sub.1d=87.5 nF, C.sub.2d=13 nF,
.omega.L.sub.d=400.OMEGA. and Z.sub.1=50.OMEGA., where s and d
denote the source and device resonators respectively and the system
is matched at U.sub.sd=3. Tuning the duty cycle dc of the switching
amplifier and the capacitor C2s may be used to dynamically
impedance match the source, as the non-tunable device is moving
relatively to the source changing the mutual inductance M between
the source and the device. In FIG. 14, we show the required values
of the tunable parameters along with the output power per DC
voltage of the amplifier. The dashed line again indicates the
output power of the amplifier that would be needed so that the
power at the load is a constant value.
[0162] In some embodiments, tuning the driving frequency f of the
source driving circuit may still be used to achieve dynamic
impedance matching at the source for a system of wireless power
transmission between the source and one or more devices. As
explained earlier, this method enables full dynamic impedance
matching of the source, even when there are variations in the
source inductance L.sub.s and thus the source resonant frequency.
For efficient power transmission from the source to the devices,
the device resonant frequencies must be tuned to follow the
variations of the matched driving and source-resonant frequencies.
Tuning a device capacitance (for example, in the embodiment of FIG.
13 C.sub.1d or C.sub.2d) may be necessary, when there are
variations in the resonant frequency of either the source or the
device resonators. In fact, in a wireless power transfer system
with multiple sources and devices, tuning the driving frequency
alleviates the need to tune only one source-object resonant
frequency, however, all the rest of the objects may need a
mechanism (such as a tunable capacitance) to tune their resonant
frequencies to match the driving frequency.
[0163] Adjustable Source Size
[0164] The efficiency of wireless power transfer methods decreases
with the separation distance between a source and a device. The
efficiency of wireless power transfer at certain separations
between the source and device resonators may be improved with a
source that has an adjustable size. The inventors have discovered
that the efficiency of wireless power transfer at fixed separations
can be optimized by adjusting the relative size of the source and
device resonators. For a fixed size and geometry of a device
resonator, a source resonator may be sized to optimize the
efficiency of wireless power transfer at a certain separations,
positions, and/or orientations. When the source and device
resonators are close to each other, power transfer efficiency may
be optimized when the characteristic sizes or the effective sizes
of the resonators are similar. At larger separations, the power
transfer efficiency may be optimized by increasing the effective
size of the source resonator relative to the device resonator. The
source may be configured to change or adjust the source resonator
size as a device moves closer or further away from the source, so
as to optimize the power transfer efficiency or to achieve a
certain desired power transfer efficiency.
[0165] In examples in this section we may describe wireless power
transfer systems and methods for which only the source has an
adjustable size. It is to be understood that the device may also be
of an adjustable size and achieve many of the same benefits. In
some systems both the source and the device may be of an adjustable
size, or in other systems only the source, or only the device may
be of an adjustable size. Systems with only the source being of an
adjustable size may be more practical in certain situations. In
many practical designs the device size may be fixed or constrained,
such as by the physical dimensions of the device into which the
device resonator must be integrated, by cost, by weight, and the
like, making an adjustable size device resonator impractical or
more difficult to implement. It should be apparent to those skilled
in the art, however, that the techniques described herein can be
used in systems with an adjustable size device, an adjustable size
source, or both.
[0166] In this section we may refer to the "effective size" of the
resonator rather than the "physical size" of the resonator. The
physical size of the resonator may be quantified by the
characteristic size of the resonator (the radius of the smallest
circle than encompasses an effectively 2-D resonator, for example).
The effective size refers to the size or extent of the surface area
circumscribed by the current-carrying inductive element in the
resonator structure. If the inductive element comprises a series of
concentric loops with decreasing radii, connected to each other by
a collection of switches, for example, the physical size of the
resonator may be given by the radius of the largest loop in the
structure, while the effective size of the resonator will be
determined by the radius of the largest loop that is "switched
into" the inductor and is carrying current.
[0167] In some embodiments, the effective size of the resonator may
be smaller than the physical size of the resonator, for example,
when a small part of the conductor comprising the resonator is
energized. Likewise, the effective size of the resonator may be
larger than the physical size of the resonator. For example, as
described below in one of the embodiments of the invention, when
multiple individual resonators with given physical sizes are
arranged to create a resonator array, grid, multi-element pattern,
and the like, the effective size of the resonator array may be
larger than the physical size of any of the individual
resonators.
[0168] The relationship between wireless power transfer efficiency
and source-device resonator separation is shown in FIG. 15A. The
plot in FIG. 15A shows the wireless power transfer efficiency for
the configuration shown in FIG. 15B where the source 5902 and
device 5901 capacitively loaded conductor loop resonators are on
axis 5903 (centered) and parallel to each other. The plot is shown
for a fixed size 5 cm by 5 cm device resonator 5901 and three
different size source resonators 5902, 5 cm.times.5 cm, 10
cm.times.10 cm and 20 cm.times.20 cm for a range of separation
distances 5906. Note that the efficiency of wireless power transfer
at different separations may depend on the relative sizes of the
source and device resonators. That is, the size of the source
resonator that results in the most efficient wireless power
transfer may be different for different separations between the
source and the device resonators. For the configuration captured by
the plot in FIG. 15A, for example, at smaller separations the
efficiency is highest when the source and device resonators are
sized to be substantially equal. For larger separations, the
efficiency of wireless power transfer is highest when the source
resonator is substantially larger than the device resonator.
[0169] The inventors have discovered that for wireless power
transfer systems in which the separation between the source and
device resonators changes, there may be a benefit to a source that
can be configured to have various effective resonator sizes. As a
device is brought closer to or further away from the source, the
source resonator may change its effective resonator size to
optimize the power transfer efficiency or to operate in a range of
desired transfer efficiencies. Such adjustment of the effective
resonator size may be manual or automatic and may be part of the
overall system control, tracking, operating, stabilization and
optimization architectures.
[0170] A wireless power transfer system with an adjustable source
size may also be beneficial when all devices that are to be powered
by the source do not have similarly sized device resonators. At a
fixed separation between a source and a device, devices with two
different sizes of device resonators may realize maximum transfer
efficiency for different sized source resonators. Then, depending
on the charging protocols and the device power requirements and
hierarchies, the source may alter its size to preferentially charge
or power one of the devices, a class of devices, all of the
devices, and the like.
[0171] Furthermore, an additional benefit from an adjustable size
source may be obtained when a single source may be required to
simultaneously power multiple devices. As more devices require
power, the spatial location or the area circumscribed by the source
resonator or the active area of the source resonator may need to
change. For example, if multiple devices are positioned in an area
but are separated from each other, the source may need to be
enlarged in order to energize the larger area that includes all the
multiple devices. As the number of devices requiring power changes,
or their spatial distribution and locations change with respect to
the source, an adjustable size source may change its size to change
the characteristics and the spatial distribution of the magnetic
fields around the source. For example, when a source is required to
transfer power to a single device, a relatively smaller source size
with the appropriate spatial distribution of the magnetic field may
be used to achieve the desired wireless power transfer efficiency.
When the source is required to transfer power to multiple devices,
a larger source size or a source with a different spatial
distribution of the magnetic field may be beneficial since the
devices may be in multiple locations around the source. As the
number of devices that require power changes, or their
distributions or power requirements change, an adjustable size
source may change its size to adjust, maximize, optimize, exceed,
or meet its operating parameters and specifications.
[0172] Another possible benefit of an adjustable source size may be
in reducing power transfer inefficiencies associated with
uncertainty or variability of the location of a device with respect
to the source. For example, a device with a certain lateral
displacement relative to the source may experience reduced power
transfer efficiencies. The plot in FIG. 16A shows the wireless
power transfer efficiency for the configuration shown in FIG. 16B
where the source 6002 and device 6001 capacitively loaded conductor
loop resonators are parallel to each other but have a lateral
offset 6008 between their center axes 6006, 6005. The plot in FIG.
16A shows power transfer efficiency for a 5 cm.times.5 cm device
resonator 6001 separated from a parallel oriented 5 cm.times.5 cm
source resonator 6002 (bold line) or a 20 cm.times.20 cm source
resonator 6002 (dotted line) by 2 cm 6008. Note that at a lateral
offset 6007 of approximately 5 cm from the 5 cm.times.5 cm source
resonator (from the center of the device resonator to the center of
the source resonator), there is a "dead spot" in the power transfer
efficiency. That is, the transfer efficiency is minimized or
approaches zero at a particular source-device offset. The dashed
line in FIG. 16A shows that the wireless power transfer efficiency
for the same device at the same separation and same lateral offset
but with the source size adjusted to 20 cm by 20 cm may be greater
than 90%. The adjustment of the source size from 5 cm.times.5 cm to
20 cm.times.20 cm moves the location of the "dead spot" from a
lateral offset of approximately 5 cm to a lateral offset of greater
than 10 cm. In this example, adjusting the source size increases
the wireless power transfer efficiency from almost zero to greater
than 90%. Note that the 20 cm.times.20 cm source is less efficient
transferring power to the 5 cm.times.5 cm device resonator when the
two resonators are on axis, or centered, or are laterally offset by
less than approximately 2 to 3 cm. In embodiments, a change in
source size may be used to move the location of a charging or
powering dead spot, or transfer efficiency minimum, allowing
greater positioning flexibility for and/or higher coupling
efficiency to, a device.
[0173] In some embodiments, a source with an adjustable size may be
implemented as a bank of resonators of various sizes that are
selectively driven by a power source or by power and control
circuitry. Based on predetermined requirements, calculated
requirements, from information from a monitoring, sensing or
feedback signal, communication, and the like, an appropriately
sized source resonator may be driven by a power source and/or by
power and control circuitry and that size may be adjusted as the
requirements or distances between the source and the device
resonators change. A possible arrangement of a bank of differently
sized resonators is shown in FIG. 17 which depicts a bank of three
differently sized resonators. In the example of FIG. 17, the three
resonators 6101, 6102, 6103 are arranged concentrically and coupled
to power and control circuitry 6104. The bank of resonators may
have other configurations and arrangements. The different
resonators may be placed side by side as in FIG. 18, arranged in an
array, and the like.
[0174] Each resonator in a multi-size resonator bank may have its
own power and control circuitry, or they each may be switched in
and selectively connected to one or more power and control circuits
by switches, relays, transistors, and the like. In some systems,
each of the resonators may be coupled to power and control
circuitry inductively. In other systems, each of the resonators may
be coupled to power and control circuitry through additional
networks of electronic components. A three resonator configuration
with additional circuitry 6201, 6202, 6203 is shown in FIG. 18. In
some systems, the additional circuitry 6201, 6202, 6203 may be used
for impedance matching between each of the resonators 6101, 6102,
6103 and the power and control circuitry 6204. In some systems it
may be advantageous to make each of the resonators and its
respective additional circuitry have the same effective impedance
as seen from the power and control circuitry. It some embodiments
the effective impedance of each resonator and additional impedance
matching network may be matched to the characteristic impedance of
the power source or the power and control circuitry. The same
effective impedance for all of the resonators may make switching
between resonators in a resonator bank easier, more efficient, or
quicker and may require less tuning or tunable components in the
power and control circuitry.
[0175] In some embodiments of the system with a bank of multi-sized
resonators, the additional circuitry 6201, 6202, 6203 may also
include additional transistors, switches, relays, and the like,
which disable, deactivate, or detune a resonator when not driven or
powered by the power and control circuitry. In some embodiments of
the system, not all of the resonators in a resonator bank of a
source may be powered or driven simultaneously. It such embodiments
of the system, it may be desirable to disable, or detune the
non-active resonators to reduce energy losses in power transfer due
to energy absorption by the unpowered resonators of the source. The
unpowered resonators of the source may be deactivated or detuned
from the resonant frequency of the other resonators by open
circuiting, disrupting, grounding, or cutting the conductor of the
resonator. Transistors, switches, relays and the like may be used
to selectively open or close electrical paths in the conductor part
of a resonator. An unpowered resonator may be likewise detuned or
deactivated by removing or adding capacitance or inductance to the
resonator with switches, transistors, relays, and the like. In some
embodiments, the natural state of individual resonators may be to
be detuned from the system operating frequency and to use signals
or power from the drive signal to appropriately tune the resonator
as it is activated in the bank.
[0176] In some embodiments of a system of a source with a bank of
multi-sized resonators, multiple resonators may be driven by one or
more power and control circuits simultaneously. In some embodiments
of the system powered resonators may be driven out of phase to
extend or direct the wireless power transfer. Constructive and
destructive interference between the oscillating magnetic fields of
multiple resonators driven in-phase or out of phase or at any
relative phase or phases may be used to create specific "hotspots"
or areas of concentrated magnetic energy. In embodiments, the
position of these hotspots may be variable and may be moved around
to achieve the desired wireless power transfer efficiencies to
devices that are moving around or to address devices at different
locations, orientations, and the like. In embodiments, the
multi-sized source resonator may be adjusted to implement a power
distribution and/or sharing algorithm and/or protocol.
[0177] In some embodiments of a bank of multi-sized resonators, the
resonators may all have substantially similar parameters and
characteristics despite the differences in their size. For example,
the resonators may all have similar impedance, resonant frequency,
quality factor, wire gauge, winding spacing, number of turns, power
levels, and the like. The properties and characteristics of the
resonators may be within 20% of their values.
[0178] In other embodiments of a bank of multi-sized resonators,
the resonators may have non-identical parameters and
characteristics tailored or optimized for the size of each
resonator. For example, in some embodiments the number of turns of
a conductor for the larger resonator may be less than for the
smallest resonator. Likewise, since the larger resonator may be
intended for powering devices that are at a distance from the
resonator, the unloaded impedance of the large resonator may be
different than that of the small resonator that is intended for
powering devices that are closer to the resonator to compensate for
the differences in effective loading on the respective resonators
due to the differences in separation. In other embodiments, the
resonators may have different or variable Q's, they may have
different shapes and thicknesses, they may be composed of different
inductive and capacitive elements and different conducting
materials. In embodiments, the variable source may be custom
designed for a specific application.
[0179] In other embodiments, a source with an adjustable size may
be realized as an array or grid of similarly sized resonators.
Power and control circuitry of the array may selectively drive one
or more resonators to change the effective size of the resonator.
For example, a possible configuration of a grid of resonators is
shown in FIG. 19. A grid of similarly sized resonators 6301 may be
arranged in a grid and coupled to one or more power and control
circuits (not shown). Each of the resonators 6301 of the array can
be individually powered or any number of the resonators may be
powered simultaneously. In the array, the effective size of the
resonator may be changed by controlling the number, location, and
driving characteristics (e.g. drive signal phase, phase offset,
amplitude, and the like) of the powered resonators. For example,
for the array of resonators in FIG. 19, the effective size of the
resonator may be controlled by changing which individual resonators
of the array are powered. The resonator may power only one of the
resonators resulting in an effective resonator size 6304 which is
equal to the size of one of the individual resonators.
Alternatively, four of the individual resonators in the upper left
portion of the array may be energized simultaneously creating an
effective resonator size 6303 that may be approximately twice the
size of each of the individual resonators. All of the resonators
may also be energized simultaneously resulting in an effective
resonator size 6302 that may be approximately three (3) times
larger than the physical size each of the individual
resonators.
[0180] In embodiments, the size of the array of individual
resonators may be scaled to any size. In larger embodiments it may
be impractical to have power and control circuitry for every
individual resonator due to cost, wiring constraints, and the like.
A switching bar of a cross-switch may be used to connect any of the
individual resonators to as few power and control circuits as
needed.
[0181] In embodiments of the array of individual resonators, the
pattern of the individual energized resonators may be modified or
optimized. The shape of the effective resonator may be rectangular,
triangular, square, circular, or any arbitrary shape.
[0182] In embodiments of arrays of resonators, which resonators get
energized may depend on the separation or distance, the lateral
offset, the orientation, and the like, between the device resonator
and the source resonator. The number of resonators that may be
driven may, for example, depend on the distance and/or the
orientation between the device resonators and the source
resonators, the number of device resonators, their various power
requirements, and the like. The location of the energized
resonators in the array or grid may be determined according to the
lateral position of the device with respect to the source. For
example, in a large array of smaller individual resonators that may
cover a floor of a room or a surface of a desk, the number of
energized resonators may change as the distance between the device
and the floor or desk changes. Likewise, as the device is moved
around a room or a desk the location of the energized resonators in
the array may change.
[0183] In another embodiment, an adjustable size source resonator
may be realized with an array of multi-sized resonators. Several
small equally sized resonators may be arranged to make a small
assembly of small resonators. The small array may be surrounded by
a larger sized resonator to make a larger assembly. The larger
assembly may itself be arranged in an array forming a yet larger
array with an even larger resonator that may surround the larger
array which itself may be arranged in an array, and so on. In this
arrangement, the source resonator comprises resonators of various
physical sizes distributed throughout the array. An example diagram
of an arrangement of resonators is shown in FIG. 20. Smaller
resonators 6401 may be arranged in two by two arrays and surrounded
by another resonator with a larger physical size 6402, forming an
assembly of resonators. That assembly of resonators may be arranged
in a two by two array and surrounded by a resonator with an even
larger physical size 6403. The pattern can be repeated to make a
larger array. The number of times each resonator or assembly of
resonators is repeated may be configured and optimized and may or
may not be symmetric. In the example of FIG. 20, each resonator and
assembly may be repeated in a two by two array, but any other
dimension of array may be suitable. Note that the arrays may be
circular, square, rectangular, triangular, diamond shaped, and the
like, or any combination of shapes and sizes. The use of
multi-sized resonators in an array may have a benefit in that it
may not require that multiple resonators be energized to result in
a larger effective resonator. This feature may simplify the power
and control circuitry of the source.
[0184] In embodiments, an adjustable source size may also be
realized using planar or cored resonator structures that have a
core of magnetic material wrapped with a capacitively loaded
conductor, examples of which are shown in FIGS. 11, 12, and 13 and
described herein. In one embodiment, as depicted in FIG. 21A, an
adjustable source may be realized with a core of magnetic material
6501 and a plurality of conductors 6502, 6503, and 6504 wrapped
around the core such that the loops of the different conductors do
not overlap. The effective size of the resonator may be changed or
adjusted by energizing a different number of the conductors. A
larger effective resonator may be realized when several adjacent
conductors are driven or energized simultaneously.
[0185] Another embodiment of an adjustable size source with a cored
resonator is shown in FIG. 21B where a core of magnetic material
6505 is wrapped with a plurality of overlapping conductors 6506,
6507, 6508. The conductors may be wrapped such that each extends a
different distance across the magnetic core 6505. For example, for
the resonator in FIG. 21B, conductor 6508 covers the shortest
distance or part of the core 6505 while conductors 6507 and 6506
each cover a longer distance. The effective size of the resonator
may be adjusted by energizing a different conductor, with the
smallest effective size occurring when the conductor that covers
the smallest distance of the magnetic core is energized and the
largest effective size when the conductor covering the largest
distance of the core is energized. Each of the conductors may be
wrapped to achieve similar inductances, impedances, capacitances,
and the like. The conductors may all be the same length with the
covering distance modified by changing the density or spacing
between the multiple loops of a conductor. In some embodiments,
each conductor may be wrapped with equal spacing thereby requiring
conductors of different lengths for each winding. In other
embodiments the number of conductors and the wrapping of each
conductor may be further optimized with non constant or varying
wrapping spacing, gauge, size, and the like.
[0186] Another embodiment of an adjustable size source with a cored
resonator is shown in FIG. 21C where multiple magnetic cores 6509,
6510, 6511 are gapped, or not touching, and wrapped with a
plurality of conductors 6512, 6513, 6514. Each of the magnetic
cores 6509, 6510, 6511 is separated with a gap 6515, 6516 and a
conductor is wrapped around each magnetic core, extending past the
gap and around the adjacent magnetic core. Conductors that do not
span a gap between two magnetic cores, such as the conductor 6513
in FIG. 21C, may be used in some embodiments. The effective size of
the resonator may be adjusted by simultaneously energizing a
different number of the conductors wrapped around the core. The
conductors that are wrapped around the gaps between the magnetic
cores may be energized guiding the magnetic field from one core to
another extending the effective size of the resonator.
[0187] As those skilled in the art will appreciate, the methods and
designs depicted in FIGS. 21A-21C may be extended to planar
resonators and magnetic cores having various shapes and protrusions
which may enable adjustable size resonators with a variable size in
multiple dimensions. For example, multiple resonators may be
wrapped around the extensions of the core shaped as in FIG. 13,
enabling an adjustable size resonator that has a variable size in
two or more dimensions.
[0188] In embodiments an adjustable size source resonator may
comprise control and feedback systems, circuits, algorithms, and
architectures for determining the most effective source size for a
configuration of devices or objects in the environment. The control
and feedback systems may use a variety of sensors, communication
channels, measurements, and the like for determining the most
efficient source size. In embodiments data from sensors,
measurement circuitry, communication channels and the like may be
processed by a variety of algorithms that select the appropriate
source size.
[0189] In embodiments the source and device may comprise a wireless
communication channel such as Bluetooth, WiFi, near-field
communication, or modulation of the magnetic field which may be
used to communicate information allowing selection of the most
appropriate or most efficient source size. The device, for example,
may communicate received power, current, or voltage to the source,
which may be used by the source to determine the efficiency of
power transfer. The device may communicate its position or relative
position which may be used to calculate the separation distance
between the source and device and used to determine the appropriate
size of the source.
[0190] In embodiments the source may measure parameters of the
resonator or the characteristics of the power transfer to determine
the appropriate source size. The source may employ any number of
electric or electronic sensors to determine parameters of various
resonators or various configurations of source resonators of the
source. The source may monitor the impedance, resistance, resonant
frequency, the magnitude and phase of currents and voltages, and
the like, of each configuration, resonator, or size of the source.
These parameters, or changes in these parameters, may be used by
the source to determine the most effective source size. For
example, a configuration of the source which exhibits the largest
impedance difference between its unloaded state and present state
may be the most appropriate or the most efficient for the state of
the system.
[0191] The operating parameters and the size of the source may be
changed continuously, periodically, or on demand, such as in
response to a request by the device or by an operator of the
system. A device may request or prompt the source to seek the most
appropriate source size during specific time intervals, or when the
power or voltage at the device drops below a threshold value.
[0192] FIGS. 22A-22D depict a possible way a wireless power
transfer system may use an adjustable source size 6604 comprising
two different sized resonators 6601, 6605 during operation in
several configurations and orientations of the device resonator
6602 in one possible system embodiment. When a device with a small
resonator 6602 is aligned and in close proximity, the source 6604
may energize the smaller resonator 6605 as shown in FIG. 22A. When
a device with a small resonator 6602 is aligned and positioned
further away, the source 6604 may energize the larger resonator
6601 as shown in FIG. 22B. When a device with a small resonator
6602 is misaligned, the source 6604 may energize the larger
resonator 6602 as shown in FIG. 22C. Finally, when a device with a
large resonator 6602 is present, the source 6604 may energize the
larger resonator 6601 as shown in FIG. 22D to maximize the power
transfer efficiency.
[0193] In embodiments an algorithm for determining the appropriate
source size may be executed on a processor, gate array, or ASIC
that is part of the source, connected to the source, or is in
communication with the source. In embodiments, the algorithm may
sequentially energize all, or a subset of possible source
configurations or sizes, measure operating characteristics of the
configurations and choose the source size with the most desirable
characteristics.
[0194] Wireless Power Repeater Resonators
[0195] A wireless power transfer system may incorporate a repeater
resonator configured to exchange energy with one or more source
resonators, device resonators, or additional repeater resonators. A
repeater resonator may be used to extend the range of wireless
power transfer. A repeater resonator may be used to change,
distribute, concentrate, enhance, and the like, the magnetic field
generated by a source. A repeater resonator may be used to guide
magnetic fields of a source resonator around lossy and/or metallic
objects that might otherwise block the magnetic field. A repeater
resonator may be used to eliminate or reduce areas of low power
transfer, or areas of low magnetic field around a source. A
repeater resonator may be used to improve the coupling efficiency
between a source and a target device resonator or resonators, and
may be used to improve the coupling between resonators with
different orientations, or whose dipole moments are not favorably
aligned.
[0196] An oscillating magnetic field produced by a source magnetic
resonator can cause electrical currents in the conductor part of
the repeater resonator. These electrical currents may create their
own magnetic field as they oscillate in the resonator thereby
extending or changing the magnetic field area or the magnetic field
distribution of the source.
[0197] In embodiments, a repeater resonator may operate as a source
for one or more device resonators. In other embodiments, a device
resonator may simultaneously receive a magnetic field and repeat a
magnetic field. In still other embodiments, a resonator may
alternate between operating as a source resonator, device resonator
or repeater resonator. The alternation may be achieved through time
multiplexing, frequency multiplexing, self-tuning, or through a
centralized control algorithm. In embodiments, multiple repeater
resonators may be positioned in an area and tuned in and out of
resonance to achieve a spatially varying magnetic field. In
embodiments, a local area of strong magnetic field may be created
by an array of resonators, and the positioned of the strong field
area may be moved around by changing electrical components or
operating characteristics of the resonators in the array.
[0198] In embodiments a repeater resonator may be a capacitively
loaded loop magnetic resonator. In embodiments a repeater resonator
may be a capacitively loaded loop magnetic resonator wrapper around
magnetic material. In embodiments the repeater resonator may be
tuned to have a resonant frequency that is substantially equal to
that of the frequency of a source or device or at least one other
repeater resonator with which the repeater resonator is designed to
interact or couple. In other embodiments the repeater resonator may
be detuned to have a resonant frequency that is substantially
greater than, or substantially less than the frequency of a source
or device or at least one other repeater resonator with which the
repeater resonator is designed to interact or couple. Preferably,
the repeater resonator may be a high-Q magnetic resonator with an
intrisic quality factor, Q.sub.r, of 100 or more. In some
embodiments the repeater resonator may have quality factor of less
than 100. In some embodiments, {square root over
(Q.sub.sQ.sub.r>100)}. In other embodiments, {square root over
(Q.sub.dQ.sub.r>100)}. In still other embodiments, {square root
over (Q.sub.r1Q.sub.r2>100)}.
[0199] In embodiments, the repeater resonator may include only the
inductive and capacitive components that comprise the resonator
without any additional circuitry, for connecting to sources, loads,
controllers, monitors, control circuitry and the like. In some
embodiments the repeater resonator may include additional control
circuitry, tuning circuitry, measurement circuitry, or monitoring
circuitry. Additional circuitry may be used to monitor the
voltages, currents, phase, inductance, capacitance, and the like of
the repeater resonator. The measured parameters of the repeater
resonator may be used to adjust or tune the repeater resonator. A
controller or a microcontroller may be used by the repeater
resonator to actively adjust the capacitance, resonant frequency,
inductance, resistance, and the like of the repeater resonator. A
tunable repeater resonator may be necessary to prevent the repeater
resonator from exceeding its voltage, current, temperature, or
power limits. A repeater resonator may for example detune its
resonant frequency to reduce the amount of power transferred to the
repeater resonator, or to modulate or control how much power is
transferred to other devices or resonators that couple to the
repeater resonator.
[0200] In some embodiments the power and control circuitry of the
repeater resonators may be powered by the energy captured by the
repeater resonator. The repeater resonator may include AC to DC, AC
to AC, or DC to DC converters and regulators to provide power to
the control or monitoring circuitry. In some embodiments the
repeater resonator may include an additional energy storage
component such as a battery or a super capacitor to supply power to
the power and control circuitry during momentary or extended
periods of wireless power transfer interruptions. The battery,
super capacitor, or other power storage component may be
periodically or continuously recharged during normal operation when
the repeater resonator is within range of any wireless power
source.
[0201] In some embodiments the repeater resonator may include
communication or signaling capability such as WiFi, Bluetooth, near
field, and the like that may be used to coordinate power transfer
from a source or multiple sources to a specific location or device
or to multiple locations or devices. Repeater resonators spread
across a location may be signaled to selectively tune or detune
from a specific resonant frequency to extend the magnetic field
from a source to a specific location, area, or device. Multiple
repeater resonators may be used to selectively tune, or detune, or
relay power from a source to specific areas or devices.
[0202] The repeater resonators may include a device into which
some, most, or all of the energy transferred or captured from the
source to the repeater resonator may be available for use. The
repeater resonator may provide power to one or more electric or
electronic devices while relaying or extending the range of the
source. In some embodiments low power consumption devices such as
lights, LEDs, displays, sensors, and the like may be part of the
repeater resonator.
[0203] Several possible usage configurations are shown in FIGS.
23A-23B, 24A-24B, and 25A-25B, showing example arrangements of a
wireless power transfer system that includes a source 7404
resonator coupled to a power source 7400, a device resonator 7408
coupled to a device 7402, and a repeater resonator 7406. In some
embodiments, a repeater resonator may be used between the source
and the device resonator to extend the range of the source. In some
embodiments the repeater resonator may be positioned after, and
further away from the source than the device resonator as shown in
FIG. 23B. For the configuration shown in FIG. 23B more efficient
power transfer between the source and the device may be possible
compared to if no repeater resonator was used. In embodiments of
the configuration shown in FIG. 23B it may be preferable for the
repeater resonator to be larger than the device resonator.
[0204] In some embodiments a repeater resonator may be used to
improve coupling between non-coaxial resonators or resonators whose
dipole moments are not aligned for high coupling factors or energy
transfer efficiencies. For example, a repeater resonator may be
used to enhance coupling between a source and a device resonator
that are not coaxially aligned by placing the repeater resonator
between the source and device aligning it with the device resonator
as shown in FIG. 24A or aligning with the source resonator as shown
in FIG. 24B.
[0205] In some embodiments multiple repeater resonators may be used
to extend the wireless power transfer into multiple directions or
multiple repeater resonators may one after another to extend the
power transfer distance as shown in FIG. 25A. In some embodiments,
a device resonator that is connected to load or electronic device
may operate simultaneously, or alternately as a repeater resonator
for another device, repeater resonator, or device resonator as
shown in FIG. 25B. Note that there is no theoretical limit to the
number of resonators that may be used in a given system or
operating scenario, but there may be practical issues that make a
certain number of resonators a preferred embodiment. For example,
system cost considerations may constrain the number of resonators
that may be used in a certain application. System size or
integration considerations may constrain the size of resonators
used in certain applications.
[0206] In some embodiments the repeater resonator may have
dimensions, size, or configuration that is the same as the source
or device resonators. In some embodiments the repeater resonator
may have dimensions, size, or configuration that is different than
the source or device resonators. The repeater resonator may have a
characteristic size that is larger than the device resonator or
larger than the source resonator, or larger than both. A larger
repeater resonator may improve the coupling between the source and
the repeater resonator at a larger separation distance between the
source and the device.
[0207] In some embodiments two or more repeater resonators may be
used in a wireless power transfer system. In some embodiments two
or more repeater resonators with two or more sources or devices may
be used.
[0208] Repeater Resonator Modes of Operation
[0209] A repeater resonator may be used to enhance or improve
wireless power transfer from a source to one or more resonators
built into electronics that may be powered or charged on top of,
next to, or inside of tables, desks, shelves, cabinets, beds,
television stands, and other furniture, structures, and/or
containers. A repeater resonator may be used to generate an
energized surface, volume, or area on or next to furniture,
structures, and/or containers, without requiring any wired
electrical connections to a power source. A repeater resonator may
be used to improve the coupling and wireless power transfer between
a source that may be outside of the furniture, structures, and/or
containers, and one or more devices in the vicinity of the
furniture, structures, and/or containers.
[0210] In one exemplary embodiment depicted in FIG. 26, a repeater
resonator 8504 may be used with a table surface 8502 to energize
the top of the table for powering or recharging of electronic
devices 8510, 8516, 8514 that have integrated or attached device
resonators 8512. The repeater resonator 8504 may be used to improve
the wireless power transfer from the source 8506 to the device
resonators 8512.
[0211] In some embodiments the power source and source resonator
may be built into walls, floors, dividers, ceilings, partitions,
wall coverings, floor coverings, and the like. A piece of furniture
comprising a repeater resonator may be energized by positioning the
furniture and the repeater resonator close to the wall, floor,
ceiling, partition, wall covering, floor covering and the like that
includes the power source and source resonator. When close to the
source resonator, and configured to have substantially the same
resonant frequency as the source resonator, the repeater resonator
may couple to the source resonator via oscillating magnetic fields
generated by the source. The oscillating magnetic fields produce
oscillating currents in the conductor loops of the repeater
resonator generating an oscillating magnetic field, thereby
extending, expanding, reorienting, concentrating, or changing the
range or direction of the magnetic field generated by the power
source and source resonator alone. The furniture including the
repeater resonator may be effectively "plugged in" or energized and
capable of providing wireless power to devices on top, below, or
next to the furniture by placing the furniture next to the wall,
floor, ceiling, etc. housing the power source and source resonator
without requiring any physical wires or wired electrical
connections between the furniture and the power source and source
resonator. Wireless power from the repeater resonator may be
supplied to device resonators and electronic devices in the
vicinity of the repeater resonator. Power sources may include, but
are not limited to, electrical outlets, the electric grid,
generators, solar panels, fuel cells, wind turbines, batteries,
super-capacitors and the like.
[0212] In embodiments, a repeater resonator may enhance the
coupling and the efficiency of wireless power transfer to device
resonators of small characteristic size, non-optimal orientation,
and/or large separation from a source resonator. As described above
in this document, and as shown in FIGS. 15A-15B, 16A-16B and
23A-23B, the efficiency of wireless power transfer may be inversely
proportional to the separation distance between a source and device
resonator, and may be described relative to the characteristic size
of the smaller of the source or device resonators. For example, a
device resonator designed to be integrated into a mobile device
such as a smart phone 8512, with a characteristic size of
approximately 5 cm, may be much smaller than a source resonator
8506, designed to be mounted on a wall, with a characteristic size
of 50 cm, and the separation between these two resonators may be 60
cm or more, or approximately twelve or more characteristic sizes of
the device resonator, resulting in low power transfer efficiency.
However, if a 50 cm.times.100 cm repeater resonator is integrated
into a table, as shown in FIG. 26, the separation between the
source and the repeater may be approximately one characteristic
size of the source resonator, so that the efficiency of power
transfer from the source to the repeater may be high. Likewise, the
smart phone device resonator placed on top of the table or the
repeater resonator, may have a separation distance of less than one
characteristic size of the device resonator resulting in high
efficiency of power transfer between the repeater resonator and the
device resonator. While the total transfer efficiency between the
source and device must take into account both of these coupling
mechanisms, from the source to the repeater and from the repeater
to the device, the use of a repeater resonator may provide for
improved overall efficiency between the source and device
resonators.
[0213] In embodiments, the repeater resonator may enhance the
coupling and the efficiency of wireless power transfer between a
source and a device if the dipole moments of the source and device
resonators are not aligned or are positioned in non-favorable or
non-optimal orientations. In the exemplary system configuration
depicted in FIG. 26, a capacitively loaded loop source resonator
integrated into the wall may have a dipole moment that is normal to
the plane of the wall. Flat devices, such as mobile handsets,
computers, and the like, that normally rest on a flat surface may
comprise device resonators with dipole moments that are normal to
the plane of the table, such as when the capacitively loaded loop
resonators are integrated into one or more of the larger faces of
the devices such as the back of a mobile handset or the bottom of a
laptop. Such relative orientations may yield coupling and the power
transfer efficiencies that are lower than if the dipole moments of
the source and device resonators were in the same plane, for
example. A repeater resonator that has its dipole moment aligned
with that of the dipole moment of the device resonators, as shown
in FIG. 26, may increase the overall efficiency of wireless power
transfer between the source and device because the large size of
the repeater resonator may provide for strong coupling between the
source resonator even though the dipole moments of the two
resonators are orthogonal, while the orientation of the repeater
resonator is favorable for coupling to the device resonator.
[0214] In the exemplary embodiment shown in FIG. 26, the direct
power transfer efficiency between a 50 cm.times.50 cm source
resonator 8506 mounted on the wall and a smart-phone sized device
resonator 8512 lying on top of the table, and approximately 60 cm
away from the center of the source resonator, with no repeater
resonator present, was calculated to be approximately 19%. Adding a
50 cm.times.100 cm repeater resonator as shown, and maintaining the
relative position and orientation of the source and device
resonators improved the coupling efficiency from the source
resonator to the device resonator to approximately 60%. In this one
example, the coupling efficiency from the source resonator to the
repeater resonator was approximately 85% and the coupling
efficiency from the repeater resonator to the device resonator was
approximately 70%. Note that in this exemplary embodiment, the
improvement is due both to the size and the orientation of the
repeater resonator.
[0215] In embodiments of systems that use a repeater resonator such
as the exemplary system depicted in FIG. 26, the repeater resonator
may be integrated into the top surface of the table or furniture.
In other embodiments the repeater resonator may be attached or
configured to attach below the table surface. In other embodiments,
the repeater resonator may be integrated in the table legs, panels,
or structural supports. Repeater resonators may be integrated in
table shelves, drawers, leaves, supports, and the like. In yet
other embodiments the repeater resonator may be integrated into a
mat, pad, cloth, potholder, and the like, that can be placed on top
of a table surface. Repeater resonators may be integrated into
items such as bowls, lamps, dishes, picture frames, books,
tchotchkes, candle sticks, hot plates, flower arrangements,
baskets, and the like.
[0216] In embodiments the repeater resonator may use a core of
magnetic material or use a form of magnetic material and may use
conducting surfaces to shape the field of the repeater resonator to
improve coupling between the device and source resonators or to
shield the repeater resonators from lossy objects that may be part
of the furniture, structures, or containers.
[0217] In embodiments, in addition to the exemplary table described
above, repeater resonators may be built into chairs, couches,
bookshelves, carts, lamps, rugs, carpets, mats, throws, picture
frames, desks, counters, closets, doors, windows, stands, islands,
cabinets, hutches, fans, shades, shutters, curtains, footstools,
and the like.
[0218] In embodiments, the repeater resonator may have power and
control circuitry that may tune the resonator or may control and
monitor any number of voltages, currents, phases, temperature,
fields, and the like within the resonator and outside the
resonator. The repeater resonator and the power and control
circuitry may be configured to provide one or more modes of
operation. The mode of operation of the repeater resonator may be
configured to act only as repeater resonator. In other embodiments
the mode of operation of the repeater resonator may be configured
to act as a repeater resonator and/or as a source resonator. The
repeater resonator may have an optional power cable or connector
allowing connection to a power source such as an electrical outlet
providing an energy source for the amplifiers of the power and
control circuits for driving the repeater resonator turning it into
a source if, for example, a source resonator is not functioning or
is not in the vicinity of the furniture. In other embodiments the
repeater resonator may have a third mode of operation in which it
may also act as a device resonator providing a connection or a plug
for connecting electrical or electronic devices to receive DC or AC
power captured by the repeater resonator. In embodiments these
modes be selected by the user or may be automatically selected by
the power and control circuitry of the repeater resonator based on
the availability of a source magnetic field, electrical power
connection, or a device connection.
[0219] In embodiments the repeater resonator may be designed to
operate with any number of source resonators that are integrated
into walls, floors, other objects or structures. The repeater
resonators may be configured to operate with sources that are
retrofitted, hung, or suspended permanently or temporarily from
walls, furniture, ceilings and the like.
[0220] Although the use of a repeater resonator with furniture has
been described with the an exemplary embodiment depicting a table
and table top devices it should be clear to those skilled in the
art that the same configurations and designs may be used and
deployed in a number of similar configurations, furniture articles,
and devices. For example, a repeater resonator may be integrated
into a television or a media stand or a cabinet such that when the
cabinet or stand is placed close to a source the repeater resonator
is able to transfer enough energy to power or recharge electronic
devices on the stand or cabinet such as a television, movie
players, remote controls, speakers, and the like.
[0221] In embodiments the repeater resonator may be integrated into
a bucket or chest that can be used to store electronics, electronic
toys, remote controls, game controllers, and the like. When the
chest or bucket is positioned close to a source the repeater
resonator may enhance power transfer from the source to the devices
inside the chest or bucket with built in device resonators to allow
recharging of the batteries.
[0222] Another exemplary embodiment showing the use of a repeater
resonator is depicted in FIG. 27. In this embodiment the repeater
resonator may be used in three different modes of operation
depending on the usage and state of the power sources and consumers
in the arrangement. The figure shows a handbag 8602 that is
depicted as transparent to show internal components. In this
exemplary embodiment, there may be a separate bag, satchel, pocket,
or compartment 8606 inside the bag 8602 that may be used for
storage or carrying of electronic devices 8610 such as cell-phones,
MP3 players, cameras, computers, e-readers, iPads, netbooks, and
the like. The compartment may be fitted with a resonator 8608 that
may be operated in at least three modes of operation. In one mode,
the resonator 8608 may be coupled to power and control circuitry
that may include rechargeable or replaceable batteries or battery
packs or other types of portable power supplies 8604 and may
operate as a wireless power source for wirelessly recharging or
powering the electronic devices located in the handbag 8602 or the
handbag compartment 8606. In this configuration and setting, the
bag and the compartment may be used as a portable, wireless
recharging or power station for electronics.
[0223] The resonator 8608 may also be used as a repeater resonator
extending the wireless power transfer from an external source to
improve coupling and wireless power transfer efficiency between the
external source and source resonator (not shown) and the device
resonators 8612 of the device 8610 inside the bag or the
compartment. The repeater resonator may be larger than the device
resonators inside the bag or the compartment and may have improved
coupling to the source.
[0224] In another mode, the resonator may be used as a repeater
resonator that both supplies power to electronic devices and to a
portable power supply used in a wireless power source. When
positioned close to an external source or source resonator the
captured wireless energy may be used by a repeater resonator to
charge the battery 8604 or to recharge the portable energy source
of the compartment 8606 allowing its future use as a source
resonator. The whole bag with the devices may be placed near a
source resonator allowing both recharging of the compartment
battery 8604 and the batteries of the devices 8610 inside the
compartment 8606 or the bag 8602.
[0225] In embodiments the compartment may be built into a bag or
container or may be an additional or independent compartment that
may be placed into any bag or storage enclosure such as a backpack,
purse, shopping bag, luggage, device cases, and the like.
[0226] In embodiments, the resonator may comprise switches that
couple the power and control circuitry into and out of the
resonator circuit so that the resonator may be configured only as a
source resonator, only as a repeater resonator, or simultaneously
or intermittently as any combination of a source, device and
repeater resonator. An exemplary block diagram of a circuit
configuration capable of controlling and switching a resonator
between the three modes of operation is shown in FIG. 28. In this
configuration a capacitively loaded conducting loop 8608 is coupled
to a tuning network 8728 to form a resonator. The tuning network
8728 may be used to set, configure, or modify the resonant
frequency, impedance, resistance, and the like of the resonator.
The resonator may be coupled to a switching element 8702,
comprising any number of solid state switches, relays, and the
like, that may couple or connect the resonator to either one of at
least two circuitry branches, a device circuit branch 8704 or a
source circuit branch 8706, or may be used to disconnect from any
of the at least two circuit branches during an inactive state or
for certain repeater modes of operation. A device circuit branch
8704 may be used when the resonator is operating in a repeater or
device mode. A device circuit branch 8704 may convert electrical
energy of the resonator to specific DC or AC voltages required by a
device, load, battery, and the like and may comprise an impedance
matching network 8708, a rectifier 8710, DC to DC or DC to AC
converters 8710, and any devices, loads, or batteries requiring
power 8714. A device circuit branch may be active during a device
mode of operation and/or during a repeater mode of operation.
During a repeater mode of operation, a device circuit branch may be
configured to drain some power from the resonator to power or
charge a load while the resonator is simultaneously repeating the
oscillating magnetic fields from an external source to another
resonator.
[0227] A source circuit branch 8706 may be used during repeater
and/or source mode of operation of the resonator. A source circuit
branch 8706 may provide oscillating electrical energy to drive the
resonator to generate oscillating magnetic fields that may be used
to wirelessly transfer power to other resonators. A source circuit
branch may comprise a power source 8722, which may be the same
energy storage device such as a battery that is charged during a
device mode operation of the resonator. A source circuit branch may
comprise DC to AC or AC to AC converters 8720 to convert the
voltages of a power source to produce oscillating voltages that may
be used to drive the resonator through an impedance matching
network 8716. A source circuit branch may be active during a source
mode of operation and/or during a repeater mode of operation of the
resonator allowing wireless power transfer from the power source
8722 to other resonators. During a repeater mode of operation, a
source circuit branch may be used to amplify or supplement power to
the resonator. During a repeater mode of operation, the external
magnetic field may be too weak to allow the repeater resonator to
transfer or repeat a strong enough field to power or charge a
device. The power from the power source 8722 may be used to
supplement the oscillating voltages induced in the resonator 8608
from the external magnetic field to generate a stronger oscillating
magnetic field that may be sufficient to power or charge other
devices.
[0228] In some instances, both the device and source circuit
branches may be disconnected from the resonator. During a repeater
mode of operation the resonator may be tuned to an appropriate
fixed frequency and impedance and may operate in a passive manner.
That is, in a manner where the component values in the capacitively
loaded conducting loop and tuning network are not actively
controlled. In some embodiments, a device circuit branch may
require activation and connection during a repeater mode of
operation to power control and measurement circuitry used to
monitor, configure, and tune the resonator.
[0229] In embodiments, the power and control circuitry of a
resonator enabled to operate in multiple modes may include a
processor 8726 and measurement circuitry, such as analog to digital
converters and the like, in any of the components or sub-blocks of
the circuitry, to monitor the operating characteristics of the
resonator and circuitry. The operating characteristics of the
resonator may be interpreted and processed by the processor to tune
or control parameters of the circuits or to switch between modes of
operation. Voltage, current, and power sensors in the resonator,
for example, may be used to determine if the resonator is within a
range of an external magnetic field, or if a device is present, to
determine which mode of operation and which circuit branch to
activate.
[0230] It is to be understood that the exemplary embodiments
described and shown having a repeater resonator were limited to a
single repeater resonator in the discussions to simplify the
descriptions. All the examples may be extended to having multiple
devices or repeater resonators with different active modes of
operation.
[0231] Wireless Power Converter
[0232] In some wireless energy transfer systems and configurations
a wireless energy converter may be used to convert the parameters
or configurations of wireless power transfer. In some embodiments a
system may have one or more sources or one or more devices that are
capable or configured to operate and transfer wireless energy with
one or more different and possibly incompatible parameters. A
wireless energy converter may be used to translate or convert the
parameters or characteristics of wireless power transfer allowing
energy transfer between sources and devices that may be configured
to receive or capture wireless energy with incompatible or
different parameters. Note that throughout this disclosure we may
use the terms wireless power converter, wireless energy converter,
wireless converter, and wireless power conversion, wireless energy
conversion, and wireless conversion interchangeably.
[0233] In embodiments a wireless power converter may be used to
convert the characteristics of wireless power transfer and allow
power transfer between a source and a device that may be designed
or configured for wireless energy transfer with different
parameters or characteristics. For example, a source resonator may
be configured or designed to operate at a specific resonant
frequency and may transfer energy via oscillating magnetic fields
at that frequency. A device resonator may be configured or designed
to operate at a different resonant frequency and may be designed or
configured to receive energy wirelessly only if the oscillating
magnetic fields are at, or close to, the device resonant frequency.
If the resonant frequencies of the source and device are
substantially different, very little or no energy may be
transferred. A wireless power converter may be used to convert the
wireless energy transferred by the source to have characteristics
or parameters such that the wireless energy may be utilized by the
device. A wireless power converter may, for example, may receive
energy via oscillating magnetic fields at one frequency and use the
captured energy to generate oscillating magnetic fields at a
different frequency that may be utilized and received by the device
with a different resonant frequency than the source.
[0234] FIGS. 29A and 29B show exemplary functionality and uses of a
wireless power converter. In wireless energy transfer systems one
or more sources 8810 may generate oscillating magnetic fields 8814
at one or more frequencies. A wireless power converter 8808 may
couple to the source 8810 and capture the energy from the
oscillating magnetic field 8814 and transfer some or all of the
captured energy by generating an oscillating magnetic field 8816 at
one or more frequencies that may be different from the source
resonator frequencies and that may be utilized by the device 8812.
It is important to note that the wireless power converter 8808 may
not need to be located between the source 8810 and the device 8812,
but only in the general vicinity of both the source and device.
Note that if a device is configured to operate or receive energy
with different parameters or characteristics than what is generated
by a source, the device may not receive significant amounts of
power from the source, even if the source and device are close
together. In embodiments, a wireless power converter may be used to
adapt the parameters of the source to parameters that may be
received by the device and may increase the efficiency of the
wireless power transfer between what would be an incompatible
source and device, in the absence of the converter. In some
embodiments the wireless power converter may also serve as a
repeater resonator and may extend, enhance, or modify the range of
the wireless power transfer when it is placed between a source and
a device or in the vicinity of the device.
[0235] A wireless power converter may be beneficial for many
wireless power systems and applications. In some embodiments the
wireless power converter may be used to convert the characteristics
of wireless power transfer between normally incompatible resonators
or wireless power transfer systems.
[0236] In some embodiments the wireless power converters may be
utilized by the wireless power transfer system to manage, separate,
or enhance the wireless power distribution between sources and
devices of different power demands, power outputs, and the like. In
embodiments, some wireless power transfer systems and
configurations may employ devices with different power demands.
Some devices in a system may have power demands for several hundred
watts of power while other devices may require only a few watts of
power or less. In systems without a wireless power converter, such
differences in power demands and device power requirements may
impose additional design constraints and limitations on the
hardware and operation of the devices. For example, in a system
where all devices are configured to operate at the same frequency,
the devices with lower power demands of a few watts may need to be
designed to withstand the voltages, currents, and magnetic field
strengths equal to those of a device requiring several hundreds of
watts of power. In embodiments, circuit components comprised by
lower power device resonators may be required to dissipate large
amounts of power as heat. One way to reduce the high voltage,
current, power, and the like, requirements on lower power devices
may be to detune the lower power device resonant frequency from the
high power source resonant frequency, or to use frequency hopping
or time multiplexing techniques to periodically, or at adjustable
intervals, decouple the device from the source. These schemes may
reduce the average power received by the device, and may expand the
range of components that may be used in the device because
components capable of withstanding high voltages, currents, powers,
and the like, for short periods of time, may be smaller, less
expensive, and more capable than components that must sustain such
voltages, currents and powers, for extended periods of time, or for
continuous operation.
[0237] In embodiments, such as when the resonant frequency of a
device is not tunable, or when the resonant frequency can be tuned
to an operating point that supports wireless power transmission
between a high power source and a lower power device, a wireless
power converter may be used to support wireless power transfer.
[0238] In an exemplary embodiment, a wireless power configuration
may wirelessly transfer two hundred watts or more of power from a
source in a wall to a television. In such an embodiment, it may be
useful to also supply wireless power to television remote
controllers, game controllers, additional displays, DVD players,
music players, cable boxes, and the like, that may be placed in the
vicinity of the television. Each of these devices may require
different power levels and may require power levels much lower than
is available from the source. In such an embodiment, it may not be
possible to adjust the power available at the source without
disrupting the operation of the television, for example. In
addition, the television remote controllers, game controllers,
additional displays, DVD players, music players, cable boxes, and
the like, may also be able to receive power from other wireless
power sources, such as a lower power energized surface source,
situated on a shelf or a table, as shown in FIG. 15 for example.
Without a wireless power converter, it may be necessary to design
the wireless power transfer hardware of the lower power devices to
withstand the voltages, currents, and magnetic fields generated by
a source capable of supplying hundreds of watts to a television, as
well as to be efficient when the lower power devices receive power
from a lower power energized surface source, for example. Circuits
may be designed for the lower power devices that enable this type
of operation, but in some embodiments, it may be preferable to
optimize the lower power device circuits for operation with lower
power sources, and to use a power converter to convert the high
power levels available from a high power source to lower power
levels, in some region of operation. A wireless power converter may
capture some of the wireless energy generated by a high power
source, may condition that power according to a variety of system
requirements, and may resupply the conditioned power at different
frequencies, power levels, magnetic field strengths, intervals, and
the like, suitable for reception by the lower power devices
referred to in this exemplary embodiment.
[0239] In some embodiments, for example, it may be preferable to
operate high power devices requiring 50 watts of power or more at
the lower frequencies such as in the range of 100 kHz to 500 kHz.
Allowable magnetic field limits for safety considerations are
relatively higher, and radiated power levels may be lower at lower
operating frequencies. In some embodiments it may be preferable to
operate smaller, lower power devices requiring 50 watts of power or
less at higher frequencies of 500 kHz or more, to realize higher Q
resonators and/or to utilize electric and electronic components
such as capacitors, inductors, AC to DC converters, and the like,
that may be smaller or more efficient allowing for smaller and/or
tighter resonator and power and control circuitry integration.
[0240] In embodiments a wireless power converter may be used to
convert wireless power transferred from multiple sources with
different parameters to a single source and may be used to convert
wireless power parameters to be compatible with more than one
device. In embodiments a wireless power converter may be used to
amplify a specific wireless power source by converting wireless
power from other sources working with different parameters.
[0241] Exemplary embodiments of wireless power transfer system
configurations employing wireless power converters are depicted in
FIG. 30. As part of the configuration, a wireless power converter
8914 may capture energy from oscillating magnetic fields 8932, 8930
from one or more sources 8922, 8924 that may be configured or
designed to operate with different parameters. The wireless power
converter 8914 may capture the energy and generate a magnetic field
8934, 8936, 8938 with one or more different parameters than the
sources 8922, 8924 from which the energy was received and transfer
the energy to one or more devices 8916, 8918, 8920. In another
aspect of the configuration, a wireless power converter 8914 may be
used to capture energy from one or more sources 8922, 8924 that may
be designed to operate with different parameters and generate a
magnetic field 8934 with parameters that match the field 8928 of
another source 8926 providing "amplification" or a boost to a field
from sources 8922, 8924 and fields 8930, 8932 with different
parameters.
[0242] In embodiments a wireless power converter may comprise one
or more magnetic resonators configured or configurable to capture
wireless energy with one or more parameters and one or more
resonators configured or configurable to transfer wireless energy
with one or more parameters. For example, a wireless power
converter designed to convert the frequency parameter of a
oscillating magnetic field is depicted in FIG. 31A. The wireless
power converter 9012 may have one or more magnetic resonators 9014,
9016 that are tuned or tunable to one or more frequencies. The
oscillating voltages generated in the resonator 9014 by the
oscillating magnetic fields 9002 may be rectified and used by a DC
to AC converter 9008 to drive another resonator 9016 with
oscillating currents generating an oscillating magnetic field 9004
with one or more different frequencies. In embodiments the DC to AC
converter of the wireless power converter may be tuned or tunable
using a controller 9010 to generate a range of frequencies and
output power levels.
[0243] In embodiments the oscillating voltages of the receiving
resonators 9014 may be converted to oscillating voltages at a
different frequency using an AC to AC converter 9018 and used to
energize a resonator 9016 of a wireless power converter without
first converting the received voltages and currents to DC as
depicted in FIG. 31B. In embodiments it may be preferable to
configure and design a wireless power converter to convert the
frequency of magnetic fields such that the captured and transferred
magnetic fields are multiples of one another such that a diode, a
nonlinear element, a frequency multiplier, a frequency divider, and
the like, may be used to convert the frequency of the captured
energy to a different frequency without first converting to a DC
voltage.
[0244] In embodiments a wireless power converter may include one or
more resonators that are time multiplexed between capturing energy
at one frequency and transferring energy at a different frequency.
The block diagram of time multiplexed power converter is depicted
in FIG. 32. A time multiplexed wireless power converter 9102 may be
tuned to capture oscillating magnetic fields 9104, convert the
generated AC energy to DC energy using an AC to DC converter 9114,
and charge an energy storage element 9108 such as a super
capacitor, battery, and the like. After a period of time, the
resonator 9116 may be tuned to a different frequency and the energy
stored in the energy storage element 9108 may be used to power an
amplifier or an DC to AC converter 9112 to drive the tuned
resonator 9116 with an oscillating voltage at the new resonant
frequency thereby generating an oscillating magnetic field. In
embodiments the resonator 9116 may change from capturing to
transferring power every few milliseconds, seconds, or minutes. The
resonator may be configured to change from capturing to
transferring of power as soon as energy in the storage element
reaches a predetermined level and may switch back to capturing when
the energy in the storage element drops below a predetermined
level. In embodiments a wireless power converter that converts
power from a high power source to a device with low power
requirements may only need to capture power for a small fraction of
the time multiplexed cycle and slowly transmit power at the
required device power level for the remainder of the cycle.
[0245] In an embodiment system utilizing wireless power converters,
an area, room, or region may be flooded or energized with low power
magnetic fields by multiple sources that may be integrated into
walls, ceilings, partitions and the like. Different wireless power
converters may be distributed or strategically located at different
locations to capture and convert the low power magnetic fields to
different frequencies, parameters, and power levels to transfer
power to different classes or types of devices within the area. In
system embodiments utilizing wireless power converters, sources may
be configured or extended to function and operate with a large
number of various devices with specialized power demands or
configurations without requiring changes or reconfiguration of the
sources.
[0246] In embodiments a wireless power converter may not require
any additional energy input and may simply convert the parameters
and characteristics of wireless power transfer. In embodiments the
wireless power converters may have additional energy inputs from
batteries, solar panels, and the like that may be used to
supplement the energy transferred.
[0247] In embodiments the wireless power converter may be tunable
and configurable such that it may be tuned or configured to convert
from any number of frequencies or power levels or energy
multiplexing schemes to any number of frequencies or power levels
or energy multiplexing schemes. It may be adjusted automatically by
sensing power levels or frequencies of a source, or the source with
the strongest or appropriate magnetic field, for example. The
converter may include communication or signaling capability to
allow configuration by a source or sources, device or devices,
repeater or repeaters, master controller or controllers or other
converters, as to parameters of the conversion that may be desired
or required. The converter may communicate or signal to a source or
sources to turn on or off, or to increase or decrease power levels,
depending on the power requirements of the device or devices,
repeater or repeaters, to which the converter is transferring
energy or for which the converter is adapting, converting, or
translating, the characteristics of the wireless power
transfer.
[0248] Although many of the specific embodiments of a wireless
power converter have been described in terms of a converter that
changes the frequency of an oscillating magnetic field it is to be
understood that frequency is an exemplary parameter and other
parameters may be converted without departing from the spirit of
the invention. In embodiments a power converter may change any
number of parameters including phase, amplitude, and the like. In
some embodiments a wireless power converter may change the sequence
or timing of frequency hopping, or allow a single frequency source
to power devices that employ or expect a constant or periodic
frequency hopping mode of operation. In some embodiments, the
converter may use time multiplexing techniques to adjust power
levels, power distribution algorithms and sequences, and to
implement preferential or hierarchical charging or powering
services.
[0249] In embodiments a wireless power converter may convert the
parameters of wireless power transfer and may also, or instead,
change the distribution of the fields generated by a source field.
A wireless power converter may include multi-sized or variable size
resonators that may be configured to redistribute the magnetic
field of a source to allow or enhance operation with a device of a
different size or at different separations. In embodiments a small
source resonator may not be the most efficient at transferring
power to a large device resonator. Likewise, a large source
resonator may not be the most efficient at transferring power to a
small device resonator. A wireless power converter may include two
or more differently sized resonators that capture and redistribute
the magnetic field for improved efficiency of wireless power
transfer to device resonators without requiring changes or
reconfiguration of the source or device resonators.
[0250] For example, as depicted in FIG. 33A, a wireless power
converter 9214 with a large capture resonator 9216 and a small
transmitting resonator 9218 may be placed close to a small device
resonator 9212 and may improve the wireless power transfer
efficiency between a large distant source resonator 9208 and a
small device resonator 9212. Likewise, as depicted in FIG. 33B, a
wireless power converter 9214 with a small capture resonator 9218
and a large transmitting resonator 9216 may placed close to a small
source resonator 9208 and may improve the wireless power transfer
efficiency between a large distant device resonator 9212 and the
small source resonator 9208. The converter resonator may include
one or more capture resonators that are sized to maximize the
efficiency of wireless power transfer from the source resonator to
the converter resonator and one or more transfer resonators that
are sized to maximize the efficiency of wireless power transfer
from the converter resonator to the device resonator. In some
embodiments energy captured by the capture resonator may be used to
directly power the transmitting resonator. In embodiments the
energy captured by the capture resonator may be converted,
modified, metered or amplified before being used to energize the
transmitter resonator. A wireless power converter with differently
sized resonators may result in improved system efficiency.
[0251] Wireless Energy Distribution System
[0252] Wireless energy may be distributed over an area using
repeater resonators. In embodiments a whole area such as a floor,
ceiling, wall, table top, surface, shelf, body, area, and the like
may be wirelessly energized by positioning or tiling a series of
repeater resonators and source resonators over the area. In some
embodiments, a group of objects comprising resonators may share
power amongst themselves, and power may be wireless transmitted to
and/or through various objects in the group. In an exemplary
embodiment, a number of vehicles may be parked in an area and only
some of the vehicles may be positioned to receive wireless power
directly from a source resonator. In such embodiments, certain
vehicles may retransmit and/or repeat some of the wireless power to
vehicles that are not parked in positions to receive wireless power
directly from a source. In embodiments, power supplied by a vehicle
charging source may use repeaters to transmit power into the
vehicles to power devices such as cell phones, computers, displays,
navigation devices, communication devices, and the like. In some
embodiments, a vehicle parked over a wireless power source may vary
the ratio of the amount of power it receives and the amount of
power it retransmits or repeats to other nearby vehicles. In
embodiments, wireless power may be transmitted from one source to
device after device and so on, in a daisy chained fashion. In
embodiments, certain devices may be able to self determine how much
power that receive and how much they pass on. In embodiments, power
distribution amongst various devices and/or repeaters may be
controlled by a master node or a centralized controller.
[0253] Some repeater resonators may be positioned in proximity to
one or more source resonators. The energy from the source may be
transferred from the sources to the repeaters, and from those
repeaters to other repeaters, and to other repeaters, and so on.
Therefore energy may be wirelessly delivered to a relatively large
area with the use of small sized sources being the only components
that require physical or wired access to an external energy
source.
[0254] In embodiments the energy distribution over an area using a
plurality of repeater resonators and at least one source has many
potential advantages including in ease of installation,
configurability, control, efficiency, adaptability, cost, and the
like. For example, using a plurality of repeater resonators allows
easier installation since an area may be covered by the repeater
resonators in small increments, without requiring connections or
wiring between the repeaters or the source and repeaters. Likewise,
a plurality of smaller repeater coils allows a greater flexibility
of placement allowing the arrangement and coverage of an area with
an irregular shape. Furthermore, the repeater resonators may be
easily moved or repositioned to change the magnetic field
distribution within an area. In some embodiments the repeaters and
the sources may be tunable or adjustable allowing the repeater
resonators to be tuned or detuned from the source resonators and
allowing a dynamic reconfiguration of energy transfer or magnetic
field distribution within the area covered by the repeaters without
physically moving components of the system.
[0255] For example, in one embodiment, repeater resonators and
wireless energy sources may be incorporated or integrated into
flooring. In embodiments, resonator may be integrated into flooring
or flooring products such as carpet tiles to provide wireless power
to an area, room, specific location, multiple locations and the
like. Repeater resonators, source resonators, or device resonators
may be integrated into the flooring and distribute wireless power
from one or more sources to one more devices on the floor via a
series of repeater resonators that transfer the energy from the
source over an area of the floor.
[0256] It is to be understood that the techniques, system design,
and methods may be applied to many flooring types, shapes, and
materials including carpet, ceramic tiles, wood boards, wood panels
and the like. For each type of material those skilled in the art
will recognize that different techniques may be used to integrate
or attach the resonators to the flooring material. For example, for
carpet tiles the resonators may be sown in or glued on the
underside while for ceramic tiles integration of tiles may require
a slurry type material, epoxy, plaster, and the like. In some
embodiments the resonators may not be integrated into the flooring
material but placed under the flooring or on the flooring. The
resonators may, for example, come prepackaged in padding material
that is placed under the flooring. In some embodiments a series or
an array or pattern of resonators, which may include source,
device, and repeater resonators, may be integrated in to a large
piece of material or flooring which may be cut or trimmed to size.
The larger material may be trimmed in between the individual
resonators without disrupting or damaging the operation of the cut
piece.
[0257] Returning now to the example of the wireless floor
embodiment comprising individual carpet tiles, the individual
flooring tiles may be wireless power enabled by integrating or
inserting a magnetic resonator to the tile or under the tile. In
embodiments resonator may comprise a loop or loops of a good
conductor such as Litz wire and coupled to a capacitive element
providing a specific resonant frequency which may be in the range
of 10 KHz to 100 MHz. In embodiments the resonator may be a high-Q
resonator with a quality factor greater than 100. Those skilled in
the art will appreciate that the various designs, shaped, and
methods for resonators such as planar resonators, capacitively
loaded loop resonators, printed conductor loops, and the like
described herein may be integrated or combined within a flooring
tile or other flooring material.
[0258] Example embodiments of a wireless power enabled floor tile
are depicted in FIG. 34A and FIG. 34B. A floor tile 12902 may
include loops of an electrical conductor 12904 that are wound
within the perimeter of the tile. In embodiments the conductor
12904 of the resonator may be coupled to additional electric or
electronic components 12906 such as capacitors, power and control
circuitry, communication circuitry, and the like. In other
embodiments the tile may include more than one resonator and more
than one loop of conductors that may be arranged in an array or a
deliberate pattern as described herein such as for example a series
of multisized coils, a configurable size coil and the like.
[0259] In embodiments the coils and resonators integrated into the
tiles may include magnetic material. Magnetic material may be used
to construct planar resonator structures such those depicted in
FIGS. 34A and 34B. In embodiments the magnetic material may also be
used for shielding of the coil of the resonator from lossy objects
that may be under or around the flooring. In some embodiments the
structures may further include a layer or sheet of a good
electrical conductor under the magnetic material to increase the
shielding capability of the magnetic material as described
herein.
[0260] Tiles with a resonator may have various functionalities and
capabilities depending on the control circuitry, communication
circuitry, sensing circuitry, and the like that is coupled to the
coil or resonator structure. In embodiments of a wireless power
enabled flooring the system may include multiple types of wireless
enabled tiles with different capabilities. One type of floor tile
may comprise only a magnetic resonator and function as a fixed
tuned repeater resonator that wirelessly transfers power from one
resonator to another resonator without any direct or wired power
source or wired power drain.
[0261] Another type of floor tile may comprise a resonator coupled
to control electronics that may dynamically change or adjust the
resonant frequency of the resonator by, for example, adjusting the
capacitance, inductance, and the like of the resonator. The tile
may further include an in-band or out-of-band communication
capability such that it can exchange information with other
communication enabled tiles. The tile may be then able to adjust
its operating parameters such as resonant frequency in response to
the received signals from the communication channel.
[0262] Another type of floor tile may comprise a resonator coupled
to integrated sensors that may include temperature sensors,
pressure sensors, inductive sensors, magnetic sensors, and the
like. Some or all the power captured by the resonator may be used
to wirelessly power the sensors and the resonator may function as a
device or partially as a repeater.
[0263] Yet another type of wireless power enabled floor tile may
comprise a resonator with power and control circuitry that may
include an amplifier and a wired power connection for driving the
resonator and function like a wireless power source. The features,
functions, capabilities of each of the tiles may be chosen to
satisfy specific design constraints and may feature any number of
different combinations of resonators, power and control circuitry,
amplifiers, sensors, communication capabilities and the like.
[0264] A block diagram of the components comprising a resonator
tile are shown in FIG. 35. In a tile, a resonator 13002 may be
optionally coupled to power and control circuitry 13006 to receive
power and power devices or optional sensors 13004. Additional
optional communication circuitry 13008 may be connected to the
power and control circuitry and control the parameters of the
resonator based on received signals.
[0265] Tiles and resonators with different features and
capabilities may be used to construct a wireless energy transfer
systems with various features and capabilities. One embodiment of a
system may include sources and only fixed tuned repeater resonator
tiles. Another system may comprise a mixture of fixed and tunable
resonator tiles with communication capability. To illustrate some
of the differences in system capabilities that may be achieved with
different types of floor tiles we will describe example embodiments
of a wireless floor system.
[0266] The first example embodiment of the wireless floor system
may include a source and only fixed tuned repeater resonator tiles.
In this first embodiment a plurality of fixed tuned resonator tiles
may be arranged on a floor to transfer power from a source to an
area or location over or next to the tiles and deliver wireless
power to devices that may be placed on top of the tiles, below the
tiles, or next to the tiles. The repeater resonators may be fixed
tuned to a fixed frequency that may be close to the frequency of
the source. An arrangement of the first example embodiment is shown
in FIG. 36. The tiles 13102 are arranged in an array with at least
one source resonator that may be integrated into a tile 13110 or
attached to a wall 13106 and wired 13112 to a power source. Some
repeater tiles may be positioned next to the source resonator and
arranged to transfer the power from the source to a desired
location via one or more additional repeater resonators.
[0267] Energy may be transferred to other tiles and resonators that
are further away from the source resonators using tiles with
repeater resonators which may be used to deliver power to devices,
integrated or connected to its own device resonator and device
power and control electronics that are placed on top or near the
tiles. For example, power from the source resonator 13106 may be
transferred wirelessly from the source 13106 to an interior area or
interior tile 13122 via multiple repeater resonators 13114, 13116,
13118, 13120 that are between the interior tile 13122 and the
source 13106. The interior tile 13122 may than transfer the power
to a device such as a resonator built into the base of a lamp
13108. Tiles with repeater resonators may be positioned to extend
the wireless energy transfer to a whole area of the floor allowing
a device on top of the floor to be freely moved within the area.
For example additional repeater resonator tiles 13124, 13126, 13128
may be positioned around the lamp 13108 to create a defined area of
power (tiles 13114, 13116, 13118, 13120, 13122, 13124, 13126,
13128) over which the lamp may be placed to receive energy from the
source via the repeater tiles. The defined area over which power is
distributed may be changed by adding more repeater tiles in
proximity to at least one other repeater or source tile. The tiles
may be movable and configurable by the user to change the power
distribution as needed or as the room configuration changes. Except
a few tiles with source resonators which may need wired source or
energy, each tile may be completely wireless and may be configured
or moved by the user or consumer to adjust the wireless power
flooring system.
[0268] A second embodiment of the wireless floor system may include
a source and one or more tunable repeater resonator tiles. In
embodiments the resonators in each or some of the tiles may include
control circuitry allowing dynamic or periodic adjustment of the
operating parameters of the resonator. In embodiments the control
circuitry may change the resonant frequency of the resonator by
adjusting a variable capacitor or a changing a bank of
capacitors.
[0269] To obtain maximum efficiency of power transfer or to obtain
a specific distribution of power transfer in the system of multiple
wireless power enabled tiles it may be necessary to adjust the
operating point of each resonator and each resonator may be tuned
to a different operating point. For example, in some situations or
applications the required power distribution in an array of tiles
may be required to be non-uniform, with higher power required on
one end of the array and lower power on the opposite end of the
array. Such a distribution may be obtained, for example, by
slightly detuning the frequency of the resonators from the resonant
frequency of the system to distribute the wireless energy where it
is needed.
[0270] For example, consider the array of tiles depicted in FIG. 36
comprising 36 tunable repeater resonator tiles with a single source
resonator 13106. If only one device that requires power is placed
on the floor, such as the lamp 13108, it may be inefficient to
distribute the energy across every tile when the energy is needed
in only one section of the floor tile array. In embodiments the
tuning of individual tiles may be used to change the energy
transfer distribution in the array. In the example of the single
lamp device 13108, the repeater tiles that are not in direct path
from the source resonator 13106 to the tile closes to the device
13122 may be completely or partially detuned from the frequency of
the source. Detuning of the unused repeaters reduces the
interaction of the resonators with the oscillating magnetic fields
changing the distribution of the magnetic fields in the floor area.
With tunable repeater tiles, a second device may be placed within
the array of tiles or the lamp device 13108 is moved from its
current location 13122 to another tile, say 13130, the magnetic
field distribution in the area of the tiles may be changed by
retuning tiles that are in the path from the source 13106 to the
new location 13130.
[0271] In embodiments, to help coordinate the distribution of power
and tuning of the resonators the resonator may include a
communication capability. Each resonator may be capable of
wirelessly communicating with one or more of its neighboring tiles
or any one of the tiles to establish an appropriate magnetic field
distribution for a specific device arrangement.
[0272] In embodiments the tuning or adjustment of the operating
point of the individual resonators to generate a desired magnetic
field distribution over the area covered by the tiles may be
performed in a centralized manner from one source or one "command
tile". In such a configuration the central tile may gather the
power requirements and the state of each resonator and each tile
via wireless communication or in band communication of each tile
and calculate the most appropriate operating point of each
resonator for the desired power distribution or operating point of
the system. The information may be communicated to each individual
tile wirelessly by an additional wireless communication channel or
by modulating the magnetic field used for power transfer. The power
may be distributed or metered out using protocols similar to those
used in communication systems. For example, there may be devices
that get guaranteed power, while others get best effort power.
Power may be distributed according to a greedy algorithm, or using
a token system. Many protocols that have been adapted for sharing
information network resources may be adapted for sharing wireless
power resources.
[0273] In other embodiments the tuning or adjustment of the
operating point of the individual resonators may be performed in a
decentralized manner. Each tile may adjust the operating point of
its resonator on its own based on the power requirements or state
of the resonators of tiles in its near proximity.
[0274] In both centralized and decentralized arrangements any
number of network based centralized and distributed routing
protocols may be used. For example, each tile may be considered as
a node in network and shortest path, quickest path, redundant path,
and the like, algorithms may be used to determine the most
appropriate tuning of resonators to achieve power delivery to one
or more devices.
[0275] In embodiments various centralized and decentralized routing
algorithms may be used to tune and detune resonators of a system to
route power via repeater resonators around lossy objects. If an
object comprising lossy material is placed on some of the tiles it
may the tiles, it may unnecessarily draw power from the tiles or
may disrupt energy transmission if the tiles are in the path
between a source and the destination tile. In embodiments the
repeater tiles may be selectively tuned to bypass lossy objects
that may be on the tiles. Routing protocols may be used to tune the
repeater resonators such that power is routed around lossy
objects.
[0276] In embodiments the tiles may include sensors. The tiles may
include sensors that may be power wirelessly from the magnetic
energy captured by the resonator built into the tile to detect
objects, energy capture devices, people 13134, and the like on the
tiles. The tiles may include capacitive, inductive, temperature,
strain, weight sensors, and the like. The information from the
sensors may be used to calculate or determine the best or
satisfactory magnetic field distribution to deliver power to
devices and may be used to detune appropriate resonators. In
embodiments the tiles may comprise sensors to detect metal objects.
In embodiments the presence of a lossy object may be detected by
monitoring the parameters of the resonator. Lossy objects may
affect the parameters of the resonator such as resonant frequency,
inductance, and the like and may be used to detect the metal
object.
[0277] In embodiments the wireless powered flooring system may have
more than one source and source resonators that are part of the
tiles, that are located on the wall or in furniture that couple to
the resonators in the flooring. In embodiments with multiple
sources and source resonators the location of the sources may be
used to adjust or change the power distribution within in the
flooring. For example, one side of a room may have devices which
require more power and may require more sources closer to the
devices. In embodiments the power distribution in the floor
comprising multiple tiles may be adjusted by adjusting the output
power (the magnitude of the magnetic field) of each source, the
phase of each source (the relative phase of the oscillating
magnetic field) of each source, and the like.
[0278] In embodiments the resonator tiles may be configured to
transfer energy from more than one source via the repeater
resonators to a device. Resonators may be tuned or detuned to route
the energy from more than one source resonator to more than one
device or tile.
[0279] In embodiments with multiple sources it may be desirable to
ensure that the different sources and may be different amplifiers
driving the different sources are synchronized in frequency and/or
phase. Sources that are operating at slightly different frequencies
and/or phase may generate magnetic fields with dynamically changing
amplitudes and spatial distributions (due to beating effects
between the oscillating sources). In embodiments, multiple source
resonators may be synchronized with a wired or wireless
synchronization signal that may be generated by a source or
external control unit. In some embodiments one source resonator may
be designed as a master source resonator that dictates the
frequency and phase to other resonators. A master resonator may
operate at its nominal frequency while other source resonators
detect the frequency and phase of the magnetic fields generated by
the master source and synchronize their signals with that of the
master.
[0280] In embodiments the wireless power from the floor tiles may
be transferred to table surfaces, shelves, furniture and the like
by integrating additional repeater resonators into the furniture
and tables that may extend the range of the wireless energy
transfer in the vertical direction from the floor. For example, in
some embodiments of a wireless power enabled floor, the power
delivered by the tiles may not be enough to directly charge a phone
or an electronic device that may be placed on top of a table
surface that may be two or three feet above the wireless power
enabled tiles. The coupling between the small resonator of the
electronic device on the surface of the table and the resonator of
the tile may be improved by placing a large repeater resonator near
the surface of the table such as on the underside of the table. The
relatively large repeater resonator of the table may have good
coupling with the resonator of the tiles and, due to close
proximity, good coupling between the resonator of the electronic
device on the surface of the table resulting in improved coupling
and improved wireless power transfer between the resonator of the
tile and the resonator of the device on the table.
[0281] As those skilled in the art will recognize the features and
capabilities of the different embodiments described may be
rearranged or combined into other configurations. A system may
include any number of resonator types, source, devices, and may be
deployed on floors, ceilings, walls, desks, and the like. The
system described in terms of floor tiles may be deployed onto, for
example, a wall and distribute wireless power on a wall or ceiling
into which enabled devices may be attached or positioned to receive
power and enable various applications and configurations. The
system techniques may be applied to multiple resonators distributed
across table tops, surfaces, shelves, bodies, vehicles, machines,
clothing, furniture, and the like. Although the example embodiments
described tiles or separate repeater resonators that may be
arranged into different configurations based on the teachings of
this disclosure it should be clear to those skilled in the art that
multiple repeater or source resonator may not be attached or
positioned on separate physical tiles or sheets. Multiple repeater
resonators, sources, devices, and their associated power and
control circuitry may be attached, printed, etched, to one tile,
sheet, substrate, and the like. For example, as depicted in FIG.
37, an array of repeater resonators 13204 may be printed, attached,
or embedded onto one single sheet 13202. The single sheet 13202 may
be deployed similarly as the tiles described above. The sheet of
resonators may be placed near, on, or below a source resonator to
distribute the wireless energy through the sheet or parts of the
sheet. The sheet of resonators may be used as a configurable sized
repeater resonator in that the sheet may be cut or trimmed between
the different resonators such as for example along line 13206 shown
in FIG. 37.
[0282] In embodiments a sheet of repeater resonators may be used in
a desktop environment. Sheet of repeater resonators may be cut to
size to fit the top of a desk or part of the desk, to fit inside
drawers, and the like. A source resonator may be positioned next to
or on top of the sheet of repeater resonators and devices such as
computers, computer peripherals, portable electronics, phones, and
the like may be charged or powered via the repeaters.
[0283] In embodiments resonators embedded in floor tiles or carpets
can be used to capture energy for radiant floor heating. The
resonators of each tile may be directly connected to a highly
resistive heating element via unrectified AC, and with a local
thermal sensor to maintain certain floor temperature. Each tile may
be able to dissipate a few watts of power in the thermal element to
heat a room or to maintain the tiles at a specific temperature.
[0284] Wireless Energy Transfer with Reduced Fields
[0285] In some wireless power transfer applications, it may be
beneficial to minimize or reduce the electric and magnetic fields
at a distance away from the system, at distances substantially
larger than the system, and sometimes at a distance within several
centimeters away from the system. The fields that need to be
minimized or reduced can be either the far-field, or the near-field
(if the wavelength is much larger than the distance between the
wireless power transfer system to the point of interest). One would
like to accomplish this without a substantial decrease of the
performance of the system, and/or dramatic changes to the external
geometry of the system. An opportunity for accomplishing this
arises from the fact that the fields far from the system are
substantially different than the fields close to the system (whose
properties determine the performance of the power transfer system).
Thereby, to a large extent, it may be possible to tune these two
sets of fields fairly independently, ensuring that the fields far
from the system are weak, or reduced, without drastically reducing
the performance (efficiency, amount of power transferred) of the
power transfer. Far from the system, one can decompose the fields
into a multipole expansion. In this disclosure, we show how one can
design the systems so that the lowest (dipole) component of the
expansion is zero or nearly zero. This way, the fields far from the
system will be weak, because the higher order components decay
substantially faster (as a function of distance) than the dipole
component. In typical wireless power transfer systems, this can
often lead to reduction of the relevant fields far from the system
by orders of magnitude.
[0286] In one embodiment, both the device and the source can be
designed to be quadrupole magnetic resonators. With the quadrupole
design the field far from the system will identically have no
dipole component. In embodiments a quadrupole magnetic resonator
may comprise two or more loops of a conductor configured such that
the current flows in opposite direction through each loop or series
of loops. In embodiments the loops of the conductor may be
co-planar. In other embodiments the loops may be oriented such that
the axis of the loops are all substantially parallel. One example
of a quadrupole magnetic resonator is shown in FIG. 38. In that
figure, the conductor of the resonator is twisted to form two
coplanar loops. When the conductor is energized with an electric
current, the current will flow substantially in opposite directions
in each of the loops, clockwise in one and counterclockwise in the
other. Each of the two loops by itself has a magnetic dipole, but
since their dipoles are identical, and the currents are circulating
in them in the opposite directions, the dipole components far from
the object cancel, and we are left with only a quadrupole
field.
[0287] Another example of a resonator that has only a quadrupole
moment is shown in FIG. 39. In the figure, the conductor of the
resonator is twisted to form two coplanar and coaxial loops. The
arrows in each of the figures represent the direction of the flow
of the current in the corresponding part of the resonator. Like in
the example of FIG. 38, when the conductor is energized with an
electric current, the current will flow substantially in opposite
directions in each of the loops.
[0288] In embodiments each of the loops of the conductor shown in
FIGS. 38 and 39 may comprise of more than one loops of conductor. A
single conductor may be first shaped to form multiple loops or
turns such that the current flows in the same direction in each of
the loops or turns and then formed to make an additional set of
loops or turns with the current flowing in the same direction in
each of the second set of loops or turns but opposite direction
with respect to the first set of loops or turns.
[0289] In the embodiment of FIG. 39 it should be noted that since
the loops do not have identical sizes, one has to make sure that
the inner loop has more turns of wire than the outer loop to
compensate; roughly, the ratio of the areas of the loops should
correspond to the inverse of the ratio of the number of turns of
wire.
[0290] Another embodiment of cancelation of the dipole moment may
be achieved with an additional source or active resonator as
illustrated in FIG. 40. In the embodiment, in addition to a source
resonator (source 1) and a device resonator (device 1), an
additional resonator (source R) is used whose main purpose is to
cancel the dipole moment far from the system. In embodiments the
current of the additional resonator (source R) is adjusted to be
exactly or substantially out of phase with the source resonator
(source 1). In embodiments, to get the most cancellation it may be
preferable to ensure source 1 and source R are of identical or near
identical sizes and have an equal number of wires, that the
orientation of their dipoles are substantially the same, and that
they circulate substantially the same amount of current.
[0291] Since the device shown in FIG. 40 is smaller, its
contribution to the field is smaller and in some application may be
neglected. Nevertheless, for some applications one can easily take
the device's contribution into account. One adds the dipole moment
of the device (as a complex vector) P.sub.D to the dipole moment of
the source 1 (as a complex vector) P.sub.S1: they are often .pi./2
out of phase with respect to each other. Sometimes these vectors
are parallel to each other (if source 1 and device 1 are parallel),
but sometimes they are not: that is why it is crucial to add them
as vectors in this consideration. Next, one ensures that source R
has the complex dipole moment P.sub.SR=-(P.sub.S1+P.sub.D), which
will ensure that the dipole field is canceled far from the entire
system shown in FIG. 40. To ensure that this is the case, one will
(most generally) have to tune the orientation of the source R (to
make sure the vectors are parallel), the phase of the current (so
it exactly cancels the other dipole), and the current going thru it
(to make sure that the magnitude of the vectors are the same). Note
that if the source R is substantially larger than the source 1
and/or the device 1, even a very weak current in the source R will
be sufficient: the impact on the fields close to the system (and
the total power in the source R) will be very small, yet the impact
on the field far from the system can be large. This scheme works
better if the centers of the wireless power system and the source R
are not very far from each other. The source R can be positioned
fairly arbitrarily: in fact it can even be surrounding the wireless
power transfer system.
[0292] In yet another embodiment the dipole component may be
cancelled if one can ensure to have two (independent) wireless
power transfer systems, sufficiently close to each other, operating
at the same time. If the dipole moment vectors of the two systems
are the same in direction and in magnitude, and one ensures to
operate the systems .pi. out of phase, the dipole component will be
canceled far from the systems. Note that the intrinsic details of
the systems can be substantially different (different sizes,
powers, etc.): only the dipole components of the fields have to be
substantially similar. A possible configuration of the system is
shown in FIG. 41. The figure shows two power transfer systems, one
comprising source 1 and device 1 and the other source 2 and device
2. Source 1 transfers energy to device 1 and source 2 transfers
energy to device 2. The two sources and devices can transfer power
to the same object (e.g. both of these systems can be installed on
the same car, charging that particular single car), or they can be
completely independent systems (i.e. charging two separate cars).
For example, in a garage with 2N cars (where N is integer), one can
ensure that the dipole components of all the cars cancel pair-wise
far from the garage. In the case when there is an odd number of
cars in the garage (e.g. 3 cars), one ensures that they are 2.pi./3
out of phase with respect to each other, so when dipole moments of
the 3 cars are added, they cancel together:
1+e.sup.-i2.pi./3+e.sup.-i4.pi./3=0. If the dipole moment vectors
of the systems are not the same, one has to make sure the sum of
their complex vectors cancels far from the system, similarly as we
discussed in the previous paragraph.
[0293] In embodiments of the system depicted in FIG. 41, each of
the source coils may be driven and controlled by a separate
amplifier operating out of phase of one another. In embodiments
each of the device resonators may be connected to separate
rectifier and control circuits. In other embodiments the two or
more source coils may be driven by the same amplifier in series.
Likewise, in some embodiments the two device resonators may be
connected to the same rectifier and control circuitry.
[0294] In another embodiment a quadrupole magnetic resonator may be
implemented with the use of a conducting plane positioned
substantially perpendicular to the dipole moment of the resonator
as depicted in FIG. 42. If one places a conducting plane below the
dipole, there will be an image dipole generated below the plane. If
the original dipole is perpendicular to the plane, the image dipole
will be also perpendicular, but opposite. Hence, far from the
object, the field will look like a quadrupole. In fact, since the
Earth itself is partially conducting, it can often provide the same
purpose as a conducting plane.
[0295] In another embodiment the dipole term far from the system
may be reduced by adding one or more repeater resonators, as in
FIG. 43. In some wireless power transfer system, a single repeater
will be .pi./2 out of phase with respect to the source, and -.pi./2
out of phase with respect to the device. This means that the source
and the device are .pi. out of phase, and that their fields tend to
cancel the dipole term far from the system. If the repeater's
dipole moment is substantially smaller than the source, or the
device, the dipole term far from the system will be small. In
embodiments, two or more repeaters can be placed between the source
and device. In embodiments, an even number of repeaters placed
between the source and device can improve cancellation of the
far-field radiation. By tuning the phases, and geometries of the
system, one could potentially reduce the dipole term far from the
system even further: the fact that the system consists of 3
resonators (instead of the usual 2) provides further opportunities
for dipole cancellation far from the system.
[0296] Another way to reduce the far-field dipole radiation
involves configuring one or more conductors so that an electric
current flows through them in a direction that creates a magnetic
dipole moment that substantially opposes the magnetic dipole of the
wireless energy transfer system. In embodiments, the conductors are
distal from the near-field region of the wireless energy transfer
system. This allows the conductors to attenuate the far-field
radiation without substantially attenuating the near-field resonant
energy transfer.
[0297] FIG. 44 depicts an embodiment where a conducting loop is
configured so that the fringing magnetic fields from the resonators
induce an oscillating current that flows through the loop. The
induced current will produce a magnetic dipole M that opposes the
magnetic dipole of the resonator system. The circle with a
concentric dot represents magnetic field lines flowing out of the
page while the circle with a cross represents magnetic field lines
flowing into the page. The far-field dipole will therefore be
attenuated by the partial cancellation of the resonator system's
dipole by the induced dipole. FIG. 45 depicts an embodiment in
which a current is directly excited in the conducting loop. The
current in the loop can substantially cancel the far-field
radiation from the dipole of the resonator system. The magnetic
dipole magnitude is the product of three factors: the current, the
number of turns in the loop, and the effective area of the loop. In
embodiments, the effective area of the outer loop is substantially
larger than the effective area of the of the resonator system. This
allows use of an excitation current in the outer loop that is
substantially less than the currents flowing in the resonator
system.
[0298] FIG. 46 depicts an embodiment a two or more conductors are
configured as short monopole antennas that are capacitively loaded
at their tops. Each individual conductor is similar to a so-called
top-hat antenna. With sufficient capacitive loading at the top,
currents of opposite phase can be induced in the two conductors by
the magnetic-dipole field of the resonator system. These induced
currents create a dipole field that can partially cancel the
far-field radiation from the dipole of the resonator system. FIG.
47 depicts an embodiment in which currents of opposite direction
are directly excited in the two conductors. These opposing currents
can create a dipole field that can substantially cancel the
far-field radiation from the resonators.
[0299] In some embodiments, two or more resonators are exchanging
wireless energy in a configuration where larger conducting objects
are located above and below the resonators. Two or more conductors
can be placed outside of the resonators in a way that the
conductors are electrically connected to one object and
capacitively coupled to the second object as shown in FIG. 48. In
embodiments, a stiff wire with a conducting plate on top would
enhance the capacitive coupling to the second object. In
embodiments, two or more top-hat antennas would couple capacitively
to the second object. In embodiments, brushes or alignment aids or
conducting posts could be configured to act as capacitively-coupled
conductors. The currents induced in the outer conductors can
partially cancel the far-field dipole radiation of the resonator
system. FIG. 49 depicts an embodiment in which currents of opposite
sign are excited in the two antennas. These opposing currents can
create a dipole field that can substantially cancel the far-field
radiation from the resonators.
[0300] In the embodiments discussed above, the goal is to eliminate
or reduce the dipole contribution to the field far from a wireless
power system. There exists a natural measure (figure of merit) to
establish to what extent has the dipole term been successfully
suppressed. A magnetic resonator has a characteristic area A.
Typically, such a resonator will have magnetic dipole moment far
from the resonator proportional to IA, where I is the current
flowing in the resonator. If one measures the field far from the
system and concludes that the field has magnetic dipole
moment<<IA, that means that the scheme we propose has been
implemented successfully.
[0301] It is to be understood that the techniques and embodiments
described may be used with any number of different resonator types
and configurations. Although many figures and embodiment examples
were described and shown with a capacitively loaded loop resonator
other resonator types may also be used in the embodiments. For
example, planar resonators comprising a block of magnetic material
such as shown in FIG. 2D or 2E may be used. The techniques may be
used with resonator coil comprising solid conducting wire, Litz
wire, or printed conductor traces that may be etched on a printed
circuit board.
[0302] While the invention has been described in connection with
certain preferred embodiments, other embodiments will be understood
by one of ordinary skill in the art and are intended to fall within
the scope of this disclosure, which is to be interpreted in the
broadest sense allowable by law. For example, designs, methods,
configurations of components, etc. related to transmitting wireless
power have been described above along with various specific
applications and examples thereof. Those skilled in the art will
appreciate where the designs, components, configurations or
components described herein can be used in combination, or
interchangeably, and that the above description does not limit such
interchangeability or combination of components to only that which
is described herein.
[0303] All documents referenced herein are hereby incorporated by
reference.
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