U.S. patent number 9,270,342 [Application Number 13/612,633] was granted by the patent office on 2016-02-23 for system and method for low loss wireless power transmission.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is Ashish Gupta, Sreenivas Kasturi, Michael K. McFarland. Invention is credited to Ashish Gupta, Sreenivas Kasturi, Michael K. McFarland.
United States Patent |
9,270,342 |
Kasturi , et al. |
February 23, 2016 |
System and method for low loss wireless power transmission
Abstract
Systems and methods for low loss wireless power transmission are
described herein. In one aspect, a transmission coil for
transmitting wireless power comprises a first and second spiral
coil. Each spiral coil comprises a plurality of turns. A center of
the first spiral coil to an outermost turn of the first spiral coil
defines a first cross section, and a center of the second spiral
coil to an outermost turn of the second spiral coil defines a
second cross section. Portions of the first spiral coil along the
first cross section and the second spiral coil along the second
cross section have a mutual inductance with respect to a receive
coil greater than 65% of a maximum mutual inductance along the
first and second cross sections. The second spiral coil is
counter-wound relative to the first spiral coil.
Inventors: |
Kasturi; Sreenivas (San Diego,
CA), Gupta; Ashish (San Diego, CA), McFarland; Michael
K. (San Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kasturi; Sreenivas
Gupta; Ashish
McFarland; Michael K. |
San Diego
San Diego
San Diego |
CA
CA
CA |
US
US
US |
|
|
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
48609403 |
Appl.
No.: |
13/612,633 |
Filed: |
September 12, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130154383 A1 |
Jun 20, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61576885 |
Dec 16, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J
50/70 (20160201); H02J 50/60 (20160201); H04B
5/0087 (20130101); H02J 50/20 (20160201); H02J
50/12 (20160201); H02J 50/90 (20160201); H04B
5/0037 (20130101); Y04S 40/121 (20130101); H02J
7/00 (20130101); Y04S 40/126 (20130101); H02J
50/40 (20160201); Y02E 60/00 (20130101) |
Current International
Class: |
H04B
5/00 (20060101); H02J 7/02 (20060101); H02J
5/00 (20060101); H01F 27/42 (20060101) |
Field of
Search: |
;307/104 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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DE |
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2005191217 |
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Jul 2005 |
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JP |
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2005525705 |
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Aug 2005 |
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JP |
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2009164293 |
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Jul 2009 |
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JP |
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WO-9316444 |
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Aug 1993 |
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WO |
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2009050625 |
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Apr 2009 |
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WO |
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WO2009149464 |
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Dec 2009 |
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WO |
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WO-2011143539 |
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WO |
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WO-2011148291 |
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Dec 2011 |
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WO |
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2012138949 |
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Oct 2012 |
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WO |
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Other References
Casanova et al., "Transmitting Coil Achieving Uniform Magnetic
Field Distribution for Planar Wireless Power Transfer System," IEEE
Radio and Wireless Symposium, 2009. RWS '09, pp. 530-533. cited by
applicant .
International Search Report and Written
Opinion--PCT/US2012/069574--ISA/EPO--Apr. 5, 2013. cited by
applicant.
|
Primary Examiner: Deberadinis; Robert
Attorney, Agent or Firm: Knobbe, Martens, Olson and Bear
LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority benefit under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/576,885
entitled "SYSTEMS FOR LOW LOSS WIRELESS POWER TRANSMISSION" filed
on Dec. 16, 2011, the disclosure of which is hereby incorporated by
reference in its entirety.
Claims
What is claimed is:
1. A transmission coil for transmitting wireless power to a receive
coil, the transmission coil comprising: a first spiral coil
comprising a plurality of turns, a center of the first spiral coil
to an outermost turn of the first spiral coil defining a first
cross section; and a second spiral coil comprising a plurality of
turns, a center of the second spiral coil to an outermost turn of
the second spiral coil defining a second cross section, portions of
the first spiral coil along the first cross section and the second
spiral coil along the second cross section having a mutual
inductance with respect to the receive coil greater than 65% of a
maximum mutual inductance along the first and second cross
sections, the second spiral coil counter-wound relative to the
first spiral coil.
2. The transmission coil of claim 1, wherein the second spiral coil
is located above or below the first spiral coil.
3. The transmission coil of claim 1, wherein the second spiral coil
is interwoven with the first spiral coil.
4. The transmission coil of claim 1, wherein a total length of the
second spiral coil is a same length as a total length of the first
spiral coil, and the second spiral coil is substantially shaped as
a reflection of the first spiral coil.
5. The transmission coil of claim 1, wherein the receive coil
comprises a first receive coil and a second receive coil.
6. The transmission coil of claim 1, wherein the second spiral coil
is located substantially on a common plane with the first spiral
coil and has a common center with first spiral coil, the first and
second cross sections are located substantially on the common
plane, and a turn distance from the common center to a center of a
particular turn along the first or second cross section of the
first or second spiral coil is a function of a distance from the
common center to the outermost turn of the first or second spiral
coil, a first value corresponding to spacings between turns of the
first or second spiral coil, a sum of a total number of turns of
the first and second spiral coils, and a first number corresponding
to the particular turn.
7. The transmission coil of claim 1, wherein the first and second
spiral coil are electrically coupled to a driver circuit and
configured to wirelessly transmit power at a level sufficient to
charge or power a receiver device.
8. The transmission coil of claim 1, wherein input signals for
first and second spiral coil are configured to be within a
frequency range of 6.5 Megahertz to 7 Megahertz.
9. The transmission coil of claim 1, wherein each turn of the first
and second spiral coil is configured to have a turn radius greater
than a minimum turn radius of 5 millimeters.
10. A method for transmitting wireless power to a receive coil, the
method comprising: driving with electrical current a first spiral
coil comprising a plurality of turns, a center of the first spiral
coil to an outermost turn of the first spiral coil defining a first
cross section; and driving with electrical current a second spiral
coil comprising a plurality of turns, a center of the second spiral
coil to an outermost turn of the second spiral coil defining a
second cross section, portions of the first spiral coil along the
first cross section and the second spiral coil along the second
cross section having a mutual inductance with respect to the
receive coil greater than 65% of a maximum mutual inductance along
the first and second cross sections, the second spiral coil
counter-wound relative to the first spiral coil.
11. The method of claim 10, wherein the second spiral coil is
located above or below the first spiral coil.
12. The method of claim 10, wherein the second spiral coil is
interwoven with the first spiral coil.
13. The method of claim 10, wherein a total length of the second
spiral coil is a same length as a total length of the first spiral
coil, and the second spiral coil is substantially shaped as a
reflection of the first spiral coil.
14. The method of claim 10, wherein the receive coil comprises a
first receive coil and a second receive coil.
15. The method of claim 10, wherein the second spiral coil is
located substantially on a common plane with the first spiral coil
and has a common center with first spiral coil, the first and
second cross sections are located substantially on the common
plane, and a turn distance from the common center to a center of a
particular turn along the first or second cross section of the
first or second spiral coil is a function of a distance from the
common center to the outermost turn of the first or second spiral
coil, a first value corresponding to spacings between turns of the
first or second spiral coil, a sum of a total number of turns of
the first and second spiral coils, and a first number corresponding
to the particular turn.
16. The method of claim 10, wherein the first and second spiral
coil are electrically coupled to a driver circuit and configured to
wirelessly transmit power at a level sufficient to charge or power
a receiver device.
17. The method of claim 10, wherein input signals for first and
second spiral coil are configured to be within a frequency range of
6.5 Megahertz to 7 Megahertz.
18. The method of claim 10, wherein each turn of the first and
second spiral coil is configured to have a turn radius greater than
a minimum turn radius of 5 millimeters.
Description
FIELD
The present invention relates generally to wireless power. More
specifically, the disclosure is directed to a transmitting coil for
low loss wireless power transmission.
BACKGROUND
An increasing number and variety of electronic devices are powered
via rechargeable batteries. Such devices include mobile phones,
portable music players, laptop computers, tablet computers,
computer peripheral devices, communication devices (e.g., Bluetooth
devices), digital cameras, hearing aids, and the like. While
battery technology has improved, battery-powered electronic devices
increasingly require and consume greater amounts of power. As such,
these devices constantly require recharging.
Rechargeable devices are often charged via wired connections
through cables or other similar connectors that are physically
connected to a power supply. Cables and similar connectors may
sometimes be inconvenient or cumbersome and have other drawbacks.
Wireless charging systems that are capable of transferring power in
free space to be used to charge rechargeable electronic devices or
provide power to electronic devices may overcome some of the
deficiencies of wired charging solutions. As such, wireless power
transfer systems and methods that efficiently and safely transfer
power to electronic devices are desirable.
SUMMARY
Various implementations of systems, methods and devices within the
scope of the appended claims each have several aspects, no single
one of which is solely responsible for the desirable attributes
described herein. Without limiting the scope of the appended
claims, some prominent features are described herein.
Details of one or more implementations of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Other features, aspects, and
advantages will become apparent from the description, the drawings,
and the claims. Note that the relative dimensions of the following
figures may not be drawn to scale.
One aspect of the disclosure provides a transmission coil for
transmitting wireless power, comprising a first spiral coil and a
second spiral coil. The first spiral coil includes a plurality of
turns. A center of the first spiral coil to an outermost turn of
the first spiral coil defines a first cross section. The second
spiral coil includes a plurality of turns. A center of the second
spiral coil to an outermost turn of the second spiral coil defines
a second cross section. Portions of the first spiral coil along the
first cross section and the second spiral coil along the second
cross section have a mutual inductance with respect to a receive
coil greater than 65% of a maximum mutual inductance along the
first and second cross sections. The second spiral coil
counter-wound relative to the first spiral coil.
Another aspect of the disclosure provides a method for transmitting
wireless power. The method includes driving with electrical current
a first spiral coil that includes a plurality of turns. A center of
the first spiral coil to an outermost turn of the first spiral coil
defines a first cross section. The method further includes driving
with electrical current a second spiral coil that includes a
plurality of turns. A center of the second spiral coil to an
outermost turn of the second spiral coil defines a second cross
section. Portions of the first spiral coil along the first cross
section and the second spiral coil along the second cross section
have a mutual inductance with respect to a receive coil greater
than 65% of a maximum mutual inductance along the first and second
cross sections. The second spiral coil is counter-wound relative to
the first spiral coil.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a functional block diagram of an exemplary wireless power
transfer system, in accordance with exemplary embodiments.
FIG. 2 is a functional block diagram of exemplary components that
may be used in the wireless power transfer system of FIG. 1, in
accordance with various exemplary embodiments.
FIG. 3 is a schematic diagram of a portion of transmit circuitry or
receive circuitry of FIG. 2 including a transmit or receive coil,
in accordance with exemplary embodiments.
FIG. 4 is a functional block diagram of a transmitter that may be
used in the wireless power transfer system of FIG. 1, in accordance
with exemplary embodiments.
FIG. 5 is a functional block diagram of a receiver that may be used
in the wireless power transfer system of FIG. 1, in accordance with
exemplary embodiments.
FIG. 6 is a schematic diagram of single switching device
differential drive amplifier in accordance with various
aspects.
FIG. 7 illustrates an exemplary drive circuit in accordance with
various aspects.
FIG. 8 illustrates an exemplary wireless power system including a
wireless transmitter and a wireless receiver.
FIGS. 9 and 10 illustrate exemplary two coil arrangements for
planar voltage co-location according to various aspects.
FIG. 11 illustrates an exemplary coil layout according to various
aspects.
FIG. 12 illustrates another exemplary coil layout according to
various aspects.
FIG. 13 illustrates a cross section of an exemplary coil
arrangement.
FIG. 14 is a plot of normalized mutual inductance versus position
for an exemplary coil arrangement.
FIG. 15 is a plot of normalized mutual inductance versus position
for another exemplary coil arrangement.
The various features illustrated in the drawings may not be drawn
to scale. Accordingly, the dimensions of the various features may
be arbitrarily expanded or reduced for clarity. In addition, some
of the drawings may not depict all of the components of a given
system, method or device. Finally, like reference numerals may be
used to denote like features throughout the specification and
figures.
DETAILED DESCRIPTION
The detailed description set forth below in connection with the
appended drawings is intended as a description of exemplary
embodiments of the invention and is not intended to represent the
only embodiments in which the invention may be practiced. The term
"exemplary" used throughout this description means "serving as an
example, instance, or illustration," and should not necessarily be
construed as preferred or advantageous over other exemplary
embodiments. The detailed description includes specific details for
the purpose of providing a thorough understanding of the exemplary
embodiments of the invention. The exemplary embodiments of the
invention may be practiced without these specific details. In some
instances, well-known structures and devices are shown in block
diagram form in order to avoid obscuring the novelty of the
exemplary embodiments presented herein.
Wirelessly transferring power may refer to transferring any form of
energy associated with electric fields, magnetic fields,
electromagnetic fields, or otherwise from a transmitter to a
receiver without the use of physical electrical conductors (e.g.,
power may be transferred through free space). The power output into
a wireless field (e.g., a magnetic field) may be received, captured
by, or coupled by a "receiving coil" to achieve power transfer.
FIG. 1 is a functional block diagram of an exemplary wireless power
transfer system 100, in accordance with exemplary embodiments of
the invention. Input power 102 may be provided to a transmitter 104
from a power source (not shown) for generating a field 105 for
providing energy transfer at a power level sufficient to charge or
power a device (not shown). A receiver 108 may couple to the field
105 and generate output power 110 for storing or consumption by the
device coupled to the output power 110. Both the transmitter 104
and the receiver 108 are separated by a distance 112. In one
exemplary embodiment, transmitter 104 and receiver 108 are
configured according to a mutual resonant relationship. When the
resonant frequency of receiver 108 and the resonant frequency of
transmitter 104 are substantially the same or very close,
transmission losses between the transmitter 104 and the receiver
108 are minimal. As such, wireless power transfer may be provided
over larger distance in contrast to purely inductive solutions that
may require large coils that require coils to be very close (e.g.,
millimeters). Resonant inductive coupling techniques may thus allow
for improved efficiency and power transfer over various distances
and with a variety of inductive coil configurations.
The receiver 108 may receive power when the receiver 108 is located
in an energy field 105 produced by the transmitter 104. The field
105 corresponds to a region where energy output by the transmitter
104 may be captured by a receiver 105. In some cases, the field 105
may correspond to the "near-field" of the transmitter 104 as will
be further described below. The transmitter 104 may include a
transmit coil 114 for outputting an energy transmission. The
receiver 108 further includes a receive coil 118 for receiving or
capturing energy from the energy transmission. The near-field may
correspond to a region in which there are strong reactive fields
resulting from the currents and charges in the transmit coil 114
that minimally radiate power away from the transmit coil 114. In
some cases the near-field may correspond to a region that is within
about one wavelength (or a fraction thereof) of the transmit coil
114. The transmit and receive coils 114 and 118 are sized according
to applications and devices to be associated therewith. As
described above, efficient energy transfer may occur by coupling a
large portion of the energy in a field 105 of the transmit coil 114
to a receive coil 118 rather than propagating most of the energy in
an electromagnetic wave to the far field. When positioned within
the field 105, a "coupling mode" may be developed between the
transmit coil 114 and the receive coil 118. The area around the
transmit and receive coils 114 and 118 where this coupling may
occur is referred to herein as a coupling-mode region.
FIG. 2 is a functional block diagram of exemplary components that
may be used in the wireless power transfer system 100 of FIG. 1, in
accordance with various exemplary embodiments of the invention. The
transmitter 204 may include transmit circuitry 206 that may include
an oscillator 222, a driver circuit 224, and a filter and matching
circuit 226. The oscillator 222 may be configured to generate a
signal at a desired frequency, such as 468.75 KHz, 6.78 MHz or
13.56 MHz, that may be adjusted in response to a frequency control
signal 223. The oscillator signal may be provided to a driver
circuit 224 configured to drive the transmit coil 214 at, for
example, a resonant frequency of the transmit coil 214. The driver
circuit 224 may be a switching amplifier configured to receive a
square wave from the oscillator 222 and output a sine wave. For
example, the driver circuit 224 may be a class E amplifier. A
filter and matching circuit 226 may be also included to filter out
harmonics or other unwanted frequencies and match the impedance of
the transmitter 204 to the transmit coil 214.
The receiver 208 may include receive circuitry 210 that may include
a matching circuit 232 and a rectifier and switching circuit 234 to
generate a DC power output from an AC power input to charge a
battery 236 as shown in FIG. 2 or to power a device (not shown)
coupled to the receiver 108. The matching circuit 232 may be
included to match the impedance of the receive circuitry 210 to the
receive coil 218. The receiver 208 and transmitter 204 may
additionally communicate on a separate communication channel 219
(e.g., Bluetooth, zigbee, cellular, etc). The receiver 208 and
transmitter 204 may alternatively communicate via in-band signaling
using characteristics of the wireless field 206.
As described more fully below, receiver 208, that may initially
have a selectively disablable associated load (e.g., battery 236),
may be configured to determine whether an amount of power
transmitted by transmitter 204 and receiver by receiver 208 is
appropriate for charging a battery 236. Further, receiver 208 may
be configured to enable a load (e.g., battery 236) upon determining
that the amount of power is appropriate. In some embodiments, a
receiver 208 may be configured to directly utilize power received
from a wireless power transfer field without charging of a battery
236. For example, a communication device, such as a near-field
communication (NFC) or radio-frequency identification device (RFID
may be configured to receive power from a wireless power transfer
field and communicate by interacting with the wireless power
transfer field and/or utilize the received power to communicate
with a transmitter 204 or other devices.
FIG. 3 is a schematic diagram of a portion of transmit circuitry
206 or receive circuitry 210 of FIG. 2 including a transmit or
receive coil 352, in accordance with exemplary embodiments of the
invention. As illustrated in FIG. 3, transmit or receive circuitry
350 used in exemplary embodiments may include a coil 352. The coil
may also be referred to or be configured as a "loop" antenna 352.
The coil 352 may also be referred to herein or be configured as a
"magnetic" antenna or an induction coil. The term "coil" is
intended to refer to a component that may wirelessly output or
receive energy for coupling to another "coil." The coil may also be
referred to as an "antenna" of a type that is configured to
wirelessly output or receive power. The coil 352 may be configured
to include an air core or a physical core such as a ferrite core
(not shown). Air core loop coils may be more tolerable to
extraneous physical devices placed in the vicinity of the core.
Furthermore, an air core loop coil 352 allows the placement of
other components within the core area. In addition, an air core
loop may more readily enable placement of the receive coil 218
(FIG. 2) within a plane of the transmit coil 214 (FIG. 2) where the
coupled-mode region of the transmit coil 214 (FIG. 2) may be more
powerful.
As stated, efficient transfer of energy between the transmitter 104
and receiver 108 may occur during matched or nearly matched
resonance between the transmitter 104 and the receiver 108.
However, even when resonance between the transmitter 104 and
receiver 108 are not matched, energy may be transferred, although
the efficiency may be affected. Transfer of energy occurs by
coupling energy from the field 105 of the transmitting coil to the
receiving coil residing in the neighborhood where this field 105 is
established rather than propagating the energy from the
transmitting coil into free space.
The resonant frequency of the loop or magnetic coils is based on
the inductance and capacitance. Inductance may be simply the
inductance created by the coil 352, whereas, capacitance may be
added to the coil's inductance to create a resonant structure at a
desired resonant frequency. As a non-limiting example, capacitor
352 and capacitor 354 may be added to the transmit or receive
circuitry 350 to create a resonant circuit that selects a signal
356 at a resonant frequency. Accordingly, for larger diameter
coils, the size of capacitance needed to sustain resonance may
decrease as the diameter or inductance of the loop increases.
Furthermore, as the diameter of the coil increases, the efficient
energy transfer area of the near-field may increase. Other resonant
circuits formed using other components are also possible. As
another non-limiting example, a capacitor may be placed in parallel
between the two terminals of the coil 350. For transmit coils, a
signal 358 with a frequency that substantially corresponds to the
resonant frequency of the coil 352 may be an input to the coil
352.
In one embodiment, the transmitter 104 may be configured to output
a time varying magnetic field with a frequency corresponding to the
resonant frequency of the transmit coil 114. When the receiver is
within the field 105, the time varying magnetic field may induce a
current in the receive coil 118. As described above, if the receive
coil 118 is configured to be resonant at the frequency of the
transmit coil 118, energy may be efficiently transferred. The AC
signal induced in the receive coil 118 may be rectified as
described above to produce a DC signal that may be provided to
charge or to power a load.
FIG. 4 is a functional block diagram of a transmitter 404 that may
be used in the wireless power transfer system of FIG. 1, in
accordance with exemplary embodiments of the invention. The
transmitter 404 may include transmit circuitry 406 and a transmit
coil 414. The transmit coil 414 may be the coil 352 as shown in
FIG. 3. Transmit circuitry 406 may provide RF power to the transmit
coil 414 by providing an oscillating signal resulting in generation
of energy (e.g., magnetic flux) about the transmit coil 414.
Transmitter 404 may operate at any suitable frequency. By way of
example, transmitter 404 may operate at the 13.56 MHz ISM band.
Transmit circuitry 406 may include a fixed impedance matching
circuit 409 for matching the impedance of the transmit circuitry
406 (e.g., 50 ohms) to the transmit coil 414 and a low pass filter
(LPF) 408 configured to reduce harmonic emissions to levels to
prevent self-jamming of devices coupled to receivers 108 (FIG. 1).
Other exemplary embodiments may include different filter
topologies, including but not limited to, notch filters that
attenuate specific frequencies while passing others and may include
an adaptive impedance match, that may be varied based on measurable
transmit metrics, such as output power to the coil 414 or DC
current drawn by the driver circuit 424. Transmit circuitry 406
further includes a driver circuit 424 configured to drive an RF
signal as determined by an oscillator 423. The transmit circuitry
406 may be comprised of discrete devices or circuits, or
alternately, may be comprised of an integrated assembly. An
exemplary RF power output from transmit coil 414 may be on the
order of 2.5 Watts.
Transmit circuitry 406 may further include a controller 415 for
selectively enabling the oscillator 423 during transmit phases (or
duty cycles) for specific receivers, for adjusting the frequency or
phase of the oscillator 423, and for adjusting the output power
level for implementing a communication protocol for interacting
with neighboring devices through their attached receivers. It is
noted that the controller 415 may also be referred to herein as
processor 415. Adjustment of oscillator phase and related circuitry
in the transmission path may allow for reduction of out of band
emissions, especially when transitioning from one frequency to
another.
The transmit circuitry 406 may further include a load sensing
circuit 416 for detecting the presence or absence of active
receivers in the vicinity of the near-field generated by transmit
coil 414. By way of example, a load sensing circuit 416 monitors
the current flowing to the driver circuit 424, that may be affected
by the presence or absence of active receivers in the vicinity of
the field generated by transmit coil 414 as will be further
described below. Detection of changes to the loading on the driver
circuit 424 are monitored by controller 415 for use in determining
whether to enable the oscillator 423 for transmitting energy and to
communicate with an active receiver. As described more fully below,
a current measured at the driver circuit 424 may be used to
determine whether an invalid device is positioned within a wireless
power transfer region of the transmitter 404.
The transmit coil 414 may be implemented with a Litz wire or as an
antenna strip with the thickness, width and metal type selected to
keep resistive losses low. In a one implementation, the transmit
coil 414 may generally be configured for association with a larger
structure such as a table, mat, lamp or other less portable
configuration. Accordingly, the transmit coil 414 generally may not
need "turns" in order to be of a practical dimension. An exemplary
implementation of a transmit coil 414 may be "electrically small"
(i.e., fraction of the wavelength) and tuned to resonate at lower
usable frequencies by using capacitors to define the resonant
frequency.
The transmitter 404 may gather and track information about the
whereabouts and status of receiver devices that may be associated
with the transmitter 404. Thus, the transmit circuitry 406 may
include a presence detector 480, an enclosed detector 460, or a
combination thereof, connected to the controller 415 (also referred
to as a processor herein). The controller 415 may adjust an amount
of power delivered by the driver circuit 424 in response to
presence signals from the presence detector 480 and the enclosed
detector 460. The transmitter 404 may receive power through a
number of power sources, such as, for example, an AC-DC converter
(not shown) to convert conventional AC power present in a building,
a DC-DC converter (not shown) to convert a conventional DC power
source to a voltage suitable for the transmitter 404, or directly
from a conventional DC power source (not shown).
As a non-limiting example, the presence detector 480 may be a
motion detector utilized to sense the initial presence of a device
to be charged that is inserted into the coverage area of the
transmitter 404. After detection, the transmitter 404 may be turned
on and the RF power received by the device may be used to toggle a
switch on the Rx device in a pre-determined manner, which in turn
results in changes to the driving point impedance of the
transmitter 404.
As another non-limiting example, the presence detector 480 may be a
detector capable of detecting a human, for example, by infrared
detection, motion detection, or other suitable means. In some
exemplary embodiments, there may be regulations limiting the amount
of power that a transmit coil 414 may transmit at a specific
frequency. In some cases, these regulations are meant to protect
humans from electromagnetic radiation. However, there may be
environments where a transmit coil 414 is placed in areas not
occupied by humans, or occupied infrequently by humans, such as,
for example, garages, factory floors, shops, and the like. If these
environments are free from humans, it may be permissible to
increase the power output of the transmit coil 414 above the normal
power restrictions regulations. In other words, the controller 415
may adjust the power output of the transmit coil 414 to a
regulatory level or lower in response to human presence and adjust
the power output of the transmit coil 414 to a level above the
regulatory level when a human is outside a regulatory distance from
the electromagnetic field of the transmit coil 414.
As a non-limiting example, the enclosed detector 460 (may also be
referred to herein as an enclosed compartment detector or an
enclosed space detector) may be a device such as a sense switch for
determining when an enclosure is in a closed or open state. When a
transmitter is in an enclosure that is in an enclosed state, a
power level of the transmitter may be increased.
In exemplary embodiments, a method by which the transmitter 404
does not remain on indefinitely may be used. In this case, the
transmitter 404 may be programmed to shut off after a
user-determined amount of time. This feature prevents the
transmitter 404, notably the driver circuit 424, from running long
after the wireless devices in its perimeter are fully charged. This
event may be due to the failure of the circuit to detect the signal
sent from either the repeater or the receive coil that a device is
fully charged. To prevent the transmitter 404 from automatically
shutting down if another device is placed in its perimeter, the
transmitter 404 automatic shut off feature may be activated only
after a set period of lack of motion detected in its perimeter. The
user may be able to determine the inactivity time interval, and
change it as desired. As a non-limiting example, the time interval
may be longer than that needed to fully charge a specific type of
wireless device under the assumption of the device being initially
fully discharged.
FIG. 5 is a functional block diagram of a receiver 508 that may be
used in the wireless power transfer system of FIG. 1, in accordance
with exemplary embodiments of the invention. The receiver 508
includes receive circuitry 510 that may include a receive coil 518.
Receiver 508 further couples to device 550 for providing received
power thereto. It should be noted that receiver 508 is illustrated
as being external to device 550 but may be integrated into device
550. Energy may be propagated wirelessly to receive coil 518 and
then coupled through the rest of the receive circuitry 510 to
device 550. By way of example, the charging device may include
devices such as mobile phones, portable music players, laptop
computers, tablet computers, computer peripheral devices,
communication devices (e.g., Bluetooth devices), digital cameras,
hearing aids (an other medical devices), and the like.
Receive coil 518 may be tuned to resonate at the same frequency, or
within a specified range of frequencies, as transmit coil 414 (FIG.
4). Receive coil 518 may be similarly dimensioned with transmit
coil 414 or may be differently sized based upon the dimensions of
the associated device 550. By way of example, device 550 may be a
portable electronic device having diametric or length dimension
smaller that the diameter of length of transmit coil 414. In such
an example, receive coil 518 may be implemented as a multi-turn
coil in order to reduce the capacitance value of a tuning capacitor
(not shown) and increase the receive coil's impedance. By way of
example, receive coil 518 may be placed around the substantial
circumference of device 550 in order to maximize the coil diameter
and reduce the number of loop turns (i.e., windings) of the receive
coil 518 and the inter-winding capacitance.
Receive circuitry 510 may provide an impedance match to the receive
coil 518. Receive circuitry 510 includes power conversion circuitry
506 for converting a received RF energy source into charging power
for use by the device 550. Power conversion circuitry 506 includes
an RF-to-DC converter 520 and may also in include a DC-to-DC
converter 522. RF-to-DC converter 520 rectifies the RF energy
signal received at receive coil 518 into a non-alternating power
with an output voltage represented by V.sub.rect. The DC-to-DC
converter 522 (or other power regulator) converts the rectified RF
energy signal into an energy potential (e.g., voltage) that is
compatible with device 550 with an output voltage and output
current represented by V.sub.out and I.sub.out. Various RF-to-DC
converters are contemplated, including partial and full rectifiers,
regulators, bridges, doublers, as well as linear and switching
converters.
Receive circuitry 510 may further include switching circuitry 512
for connecting receive coil 518 to the power conversion circuitry
506 or alternatively for disconnecting the power conversion
circuitry 506. Disconnecting receive coil 518 from power conversion
circuitry 506 not only suspends charging of device 550, but also
changes the "load" as "seen" by the transmitter 404 (FIG. 2).
As disclosed above, transmitter 404 includes load sensing circuit
416 that may detect fluctuations in the bias current provided to
transmitter driver circuit 424. Accordingly, transmitter 404 has a
mechanism for determining when receivers are present in the
transmitter's near-field.
When multiple receivers 508 are present in a transmitter's
near-field, it may be desirable to time-multiplex the loading and
unloading of one or more receivers to enable other receivers to
more efficiently couple to the transmitter. A receiver 508 may also
be cloaked in order to eliminate coupling to other nearby receivers
or to reduce loading on nearby transmitters. This "unloading" of a
receiver is also known herein as a "cloaking" Furthermore, this
switching between unloading and loading controlled by receiver 508
and detected by transmitter 404 may provide a communication
mechanism from receiver 508 to transmitter 404 as is explained more
fully below. Additionally, a protocol may be associated with the
switching that enables the sending of a message from receiver 508
to transmitter 404. By way of example, a switching speed may be on
the order of 100 .mu.sec.
In an exemplary embodiment, communication between the transmitter
404 and the receiver 508 refers to a device sensing and charging
control mechanism, rather than conventional two-way communication
(i.e., in band signaling using the coupling field). In other words,
the transmitter 404 may use on/off keying of the transmitted signal
to adjust whether energy is available in the near-field. The
receiver may interpret these changes in energy as a message from
the transmitter 404. From the receiver side, the receiver 508 may
use tuning and de-tuning of the receive coil 518 to adjust how much
power is being accepted from the field. In some cases, the tuning
and de-tuning may be accomplished via the switching circuitry 512.
The transmitter 404 may detect this difference in power used from
the field and interpret these changes as a message from the
receiver 508. It is noted that other forms of modulation of the
transmit power and the load behavior may be utilized.
Receive circuitry 510 may further include signaling detector and
beacon circuitry 514 used to identify received energy fluctuations,
that may correspond to informational signaling from the transmitter
to the receiver. Furthermore, signaling and beacon circuitry 514
may also be used to detect the transmission of a reduced RF signal
energy (i.e., a beacon signal) and to rectify the reduced RF signal
energy into a nominal power for awakening either un-powered or
power-depleted circuits within receive circuitry 510 in order to
configure receive circuitry 510 for wireless charging.
Receive circuitry 510 further includes processor 516 for
coordinating the processes of receiver 508 described herein
including the control of switching circuitry 512 described herein.
Cloaking of receiver 508 may also occur upon the occurrence of
other events including detection of an external wired charging
source (e.g., wall/USB power) providing charging power to device
550. Processor 516, in addition to controlling the cloaking of the
receiver, may also monitor beacon circuitry 514 to determine a
beacon state and extract messages sent from the transmitter 404.
Processor 516 may also adjust the DC-to-DC converter 522 for
improved performance.
FIG. 6 depicts a schematic diagram of an exemplary single switching
device differential drive amplifier 624 according to some aspects.
In certain aspects, the differential drive amplifier 624 can
correspond to the driver circuit 224 of FIG. 2. The amplifier 624
includes an upper RLC (resistor/inductor/capacitor) network 670
connected to a supply voltage (+Vcc), and a lower RLC network 672
connected to ground. The upper network 670 and the lower network
672 share a switching device 671, which floats between the two
networks. The switching device 671 may receive a control or drive
signal that may control the switching operations of the switching
device 671. The switching device 671 may also define two output
nodes n1 and n2, where differential output signals are respectively
present. The control or drive signal may cause the switching device
to alter its conductive state. In this manner, differential output
signals may be produced at node n1 and node n2 that are
substantially equal and opposite with respect to each other.
The upper RLC network 670 may be matched with the lower RLC network
672, such that the characteristics (e.g., resistances,
capacitances, inductances, and the like) of the components of the
networks are substantially identical. According to some example
embodiments, the switching device 671 may be connected between
inductors (also referred to as windings or coils) L1 and L2, which
may be matched and tightly coupled. The inductors L3 and L4 may
also be matched and tightly coupled.
As used herein, the term "float" may be used to indicate that a
device is not connected to a fixed potential (e.g., +Vcc or
ground). For example, a device may be floating if it is connected
through non-zero impedance components, such as inductors or
capacitors to a fixed potential. As such, the potential at a
terminal of a floating component may tend to wander or float with
respect to a fixed potential.
The switching device 671, which may be embodied as a transistor
(e.g., a field effect transistor or the like), may switch open or
closed in response to a control or drive signal, such as the square
wave depicted in FIG. 6. According to various example embodiments,
the currents I1 and I2 in the upper and lower networks are in
opposite directions in the respective networks. As result of the
switching operations performed by the switching device 671 and
currents I1 and I2, differential output signals may be generated at
nodes n1 and n2. Due to the coupling effect of the L3 inductor with
the L4 inductor, the differential output signals generated at nodes
n1 and n2 may interact to eliminate noise present in the input
signal. As such, the load RL may receive a signal having an
associated reduction in both conducted and radiated noise.
As stated above, the coupling between inductors L3 and L4, may
facilitate the reduction in noise provided by the amplifier. To
maximize noise cancellation, inductors L3 and L4 may be positioned
as close together as possible so that the inductors are strongly
coupled. In practice, a designer may desire to come as close to the
hypothetical case of complete noise cancellation, while still
avoiding the perfect cancellation of signals. According to some
example embodiments, a pair of strongly coupled inductors may be
used that are combined in a single package, such as the Coiltronix
DRQ127-470-R, which results in the inductors being as closely
coupled as possible. As a result of the strong coupling, the
current in each of the inductors may be forced to be almost
equivalent in value, facilitating the generation of the inversely
oriented signals. According to example embodiments where the
inductors are not included in the same package (e.g., a wireless
power system), the inductors L3 and L4 may be inter-wounded coils
used for transmitting wireless power to one or more secondary coils
and may utilize strong coupling by maintaining the inductors in
close proximity.
FIG. 7 illustrates a drive circuit 722 in accordance with some
example embodiments. In certain aspects, the driver circuit 722 can
correspond to the oscillator 222 of FIG. 2. The drive circuit 722
may receive an input signal at 781 and provide a drive signal at
784 to the gate of the switching device 771. The drive signal at
784 may be generated via a gate drive transformer 782 and an
h-bridge network 783. According to some example embodiments, to
generate the drive signal at 784 for a switching device, an
isolated drive scheme may be implemented using the transformer 782.
According to some example embodiments, the transformer 782 may be a
pulse transformer. The transformer 782 may sense the voltage
difference across its input terminals and apply the same voltage
across its output terminals. By connecting the output terminals of
the transformer 782 across the gate and source of the switching
device 771, switching may be performed even though the source and
the drain are floating between n1 and n2.
In some example embodiments, the switching device 771 may be
designed to switch at a rapid speed, which may require a rapidly
changing drive signal at the gate of the switching device. To
achieve the rapidly changing drive signal, the h-bridge circuit 783
may be utilized. Referring to FIG. 6, the h-bridge circuit 783 may
include diodes, D1 and D2, and bipolar junction transistors (BJTs),
B1 and B2. The diodes and the capacitors, C1 and C2, may form a
voltage doubler circuit, which may be used to generate a direct
current (DC) voltage across nodes n4 and n2. The BJTs may be set in
a push-pull configuration to drive the gate of switching device 771
using this DC voltage. A push-pull configuration may rely on
several inherent characteristics of BJTs. B1 may be a PNP
transistor and act as a closed switch between the collector
(connected to node n4) and emitter (connected to node ng), while
the BJTs base voltage (connected to node n3) may be higher than the
voltage at the emitter. On the other hand, B2 may be an NPN
transistor and act as a closed switch between its collector
(connected to node n2) and emitter (connected to node ng) while its
base voltage (connected to node n3) may be lower than the voltage
at the emitter. When not operating as a closed switch both B1 and
B2 may act as open switches.
When the transformer forces node n3's voltage higher than the
voltage at node n2, B1 may sense a positive voltage between its
base and emitter terminals resulting in current flowing from the
capacitor C1 to the gate of switching device 771. Likewise, B2 may
sense the lower voltage between its base and its emitter causing
the gate of switching device 71 to discharge to node n2. As a
result, the h-bridge 783 provides for fast ramp up and ramp down of
the voltage of the signal at the gate of switching device 771 (with
respect to the source) thereby allowing for rapid switching.
FIG. 8 depicts an example wireless power system 800 in accordance
with various aspects. The wireless power system of FIG. 8 may
include a wireless power transmitter 804 and a wireless power
receiver 808. The wireless power transmitter 804 may include a
differential drive amplifier 824, which, in turn, may include a
single switching device 871 and a drive circuit 822. In certain
aspects, the drive circuit 822 and the differential drive amplifier
824 may correspond to the driver circuit 722 and the differential
drive amplifier 624 of FIGS. 6 and 7, respectively. The drive
circuit 822 may receive an input signal 802. The wireless power
transmitter 804 may also include a supply network 825 and primary
coils 814. The wireless power receiver 808 may include secondary
coils 818, a rectifier 834, and a load 850, which may be a dynamic
load. In some example embodiments, the load 850 may be rechargeable
battery for an electronic device.
According to various aspects, the wireless power system of FIG. 8
implements switching operations to convert a DC voltage provided by
the supply network 825 into a high frequency signal. The
differential drive amplifier 824 may operate, as described above,
to generate two high frequency output signals that are differential
and substantially equal and opposite. The differential output
signals may be delivered to respective primary coils that are
positioned to provide for noise cancellation through a coupling of
the primary coils 814. The primary coils 814 may be oriented such
that the currents in the coils flow in the same direction, thereby
providing for noise cancellation while also having a minimal effect
on the magnetic field generation of the primary coils 814. Due to
the direction of the current, magnetic fields may be generated that
have the same polarity. The magnetic field may induce a current in
the one or more secondary coils of the wireless power receiver 818.
The one or more secondary coils 818 may receive an induced
alternating current (AC) signal, which may then be rectified, via
the rectifier 834, and fed to a load 850.
According to some aspects, the primary coils 814 may be configured
to facilitate noise cancellation by co-locating substantially equal
and opposite voltages at any location on a planar surface defined
by the primary coils 814. According to some example embodiments,
the primary coils 814 may be configured to co-locate substantially
equal and opposite voltages at any location in a three-dimensional
space surrounding the primary coil network. According to various
example embodiments the primary coils 814 may be driven by
differential output signals as described above. However, according
to some example embodiments, the primary coil arrangements and
configurations described herein may be utilized in conjunction with
any type of differential drive amplifier, including but not limited
to a single switching device differential drive amplifier as
described herein. For example, the primary coil arrangements and
configurations may be used with a differential drive amplifier that
includes multiple switching devices and/or transistors.
With respect to the positional configuration of the primary coils
814, each primary coil may be wound as a spiral on a geometric
plane. To facilitate co-location of voltages, the distance between
each turn of a coil may be increased as the spiral configuration
moves towards the center of an area. The first coil and the second
coil may therefore have a spiral configuration substantially within
a common plane that provides for co-location of substantially equal
and opposite voltages within the first and second coils,
respectively, at any location on the common plane. According to
some example embodiments, a single coil may be utilized that
spirals into a center point or area, and then spirals back out. As
such, a coil arrangement may be constructed of two coils that are
connected at a central location to achieve a single coil
embodiment.
FIG. 9 illustrates a perspective view of an exemplary two coil
arrangement according to various aspects. FIG. 10 illustrates a top
view of an exemplary two coil arrangement according to various
example aspects. FIG. 11 illustrates a top view of the aspect of
FIG. 10 with only a first coil depicted, and FIG. 12 illustrates a
top view of the aspect of FIG. 10 with only a second coil
depicted.
In some aspects, the primary coils 814 of FIG. 8 may be formed as
the two coil structures of FIGS. 9 and 10. Each coil may be driven
by a signal that is substantially equal and opposite relative to a
signal driving the other coil. One coil may be wound
counterclockwise while the other coil may be wound clockwise. One
coil may be substantially a reflection of the other coil and have a
same total length as the other coil. The two coils may be
configured together to create a single coil structure by placing
one coil above, below, or interwove the other coil. The two coil
arrangements of FIGS. 9 and 10, for instance, may form a single
coil structure where the coils are located substantially on a
common plane and have a common center. In some aspects, a single
coil structure may instead include one coil or three or more coils.
In certain aspects, the single coil structure may further be used
as a receiver coil such as secondary coils 818 of FIG. 8.
A single coil structure may be non-planar in some aspects and
planar with a flexible plane in other aspects. The single coil
structure may be any symmetric shape, including rectangle or
circle, for example. The single coil structure may be oriented in
various orientations including vertical, horizontal, and
diagonally, among other possibilities. Further, the single coil
structure may be located on or in a variety of items including
surfaces, walls, tape, and portable electronics, among other
possibilities.
In some aspects, the portion of a single coil structure used to
input in the signal to each coil may feed in from a location other
than a corner along the edge of the single coil structure. For
example, the signal may be input perpendicular to the top side of
the single coil structure along a top-center edge as illustrated in
FIG. 10.
Each corner of a single coil structure may have a minimum turn
radius. In particular aspects, the minimum turn radius may be
approximately 5 millimeters. The minimum turn radius may be greater
or less in other aspects.
A receive coil, such as secondary coils 818 of FIG. 8, may be
placed above or below a perimeter or inside area of the single coil
structure. The receive coil may be a first distance from one coil
of the single coil structure and a second distance from another
coil of the single coil structure. In some aspects, the first and
second distances may each be between a range of between 3
millimeters to 40 millimeters. In other aspects, the first and
second distances may be less than 3 millimeters or greater than 40
millimeters. In addition, in some aspects, the first distance may
equal the second distance so that the first and second coils of the
single coil structure may be closely located and substantially
located on a common plane.
FIG. 13 illustrates a side view of an example cross section 1300 of
a single coil structure from a center 1302 to an outermost turn
1312 (i.e., the fifth turn) of the single coil structure. The
spacings between consecutive turns of the single coil structure may
be represented as variables and determined as a function of
distance along the cross section of the single coil structure from
the center 1302 to the outermost turn 1312. The illustrated single
coil structure includes N turns (i.e., five turns), including a
first turn 1304, second turn 1306, third turn 1308, fourth turn
1310, and outermost turn 1312. The distance from the center 1302 to
an i-th turn (e.g., the third turn) is denoted as d.sub.i, and the
distance from the center 1302 to the center of the outermost turn
1312 is denoted as D/2.
In some aspects, the distance d.sub.i along a cross section from
the center of a single coil structure to an i-th turn is given by
the function of Equation 1.
.times..times..times..times..times..times. ##EQU00001## is a
distance from the center to the outermost turn, r is a value
corresponding to spacings between turns of the single spiral
structure, N is a sum of a total number of turns of the single
spiral structure, and i is a number corresponding to the particular
turn. In some aspects, Equation 1 additionally or alternatively
describes a distance along a cross section from the center of one
turn of a single coil structure to an i-th turn. Further, in some
aspects, a distance along a cross section from the center of a
single coil structure or the center of one turn of the single coil
structure to an i-th turn is additionally or alternatively given by
a function where the distance is proportional to D and i and
inversely proportional to N.
As an example cross section line, FIG. 10 illustrates a top view of
a cross section line drawn on a single coil structure. As
illustrated, each coil of the single coil structure may share a
common cross section line that is substantially located on a common
plane. The cross section line alternately crosses six turns of the
two-coil single coil structure, crossing three turns of each of the
two coils. The spacings, such as spacings S.sub.1, S.sub.2,
S.sub.3, between consecutive turns generally increase from an
outermost turn to the center of the single coil structure.
FIG. 14 is a plot 1400 of normalized mutual inductance versus
position for an example single coil structure. The mutual
inductance values 1402 in plot 1400 show the mutual inductance for
a cross section 1404 of a single coil structure relative to a
receive coil at positions 10 millimeters above the cross section.
The mutual inductance values 1402 are normalized by a maximum
mutual inductance of the positions along the cross section. The
receive coil used to construct the plot 1400 was a one turn coil
having finite width of 44 millimeters where the field across the
receive coil was averaged to determine a mutual inductance
distribution. In addition, along the position axis, an illustrative
side view of the cross section 1404 for each turn of the single
coil structure is shown as multiple Os, providing a sense of the
turns and spacings that resulted in the illustrated mutual
inductance distribution.
Similarly, FIG. 15 is a plot 1500 of normalized mutual inductance
versus position for an example single coil structure. The mutual
inductance values 1502 in plot 1500 show the mutual inductance for
a cross section 1504 of a single coil structure relative to a
receive coil at positions 10 millimeters above the cross section.
The mutual inductance values 1502 are normalized by a maximum
mutual inductance of the positions along the cross section. The
receive coil used to construct the plot 1500 was a one turn coil
having finite width of 44 millimeters where the field across the
receive coil was averaged to determine a mutual inductance
distribution. In addition, along the position axis, an illustrative
side view of the cross section 1504 for each turn of the single
coil structure is shown as multiple Os, providing a sense of the
turns and spacings that resulted in the illustrated mutual
inductance distribution.
By comparing the distributions of FIGS. 14 and 15, it can be noted
that varying spacings between turns of a single coil structure
results in variation between a maximum and minimum normalized
mutual inductance of the distribution. Advantageously, less
variation between the maximum and minimum normalized mutual
inductance corresponds to increased uniformity in the magnetic
field generated by the cross section of the single coil structure.
As a result, spacings between turns of a single coil structure may
be designed so that the minimum normalized mutual inductance
exceeds a percentage of the maximum normalized mutual inductance
along some or all cross sections of a primary coil structure. For
instance, the spacings between turns may be selected so that a
minimum normalized mutual inductance exceeds 50% or 65% of a
maximum normalized mutual inductance along some or all cross
sections of a single coil structure. Other minimum mutual
inductance thresholds may be used in some aspects. Further,
advantageously, in certain aspects, by applying minimum mutual
inductance thresholds to various cross sections of a single coil
structure, the single coil structure is formed to create a
substantially uniform three-dimensional magnetic field at a
distance above or below the single coil structure.
In some aspects, spacings between turns may be designed so that
variation between the maximum and minimum normalized mutual
inductance is substantially minimized. For example, the value of r
in Equation 1 may be solved or selected so that portions of the
single coil structure along a cross section have a difference
between a maximum and minimum normalized mutual inductance that
varies less than for other values of r. In one aspect, the value of
r may be in the range of around 0.65 to 0.68 since a value of
approximately 0.67 may result in a minimum difference between the
maximum and minimum normalized mutual inductance. When the value of
r is approximately 0.67, a percentage difference between the
maximum and minimum normalized mutual inductance along the cross
section may be as low as approximately 21%.
The spacings between turns of a single coil structure may generally
increase from an outermost turn to the center of the single coil
structure. Such an increase in the spacings may enable generation
of a substantially uniform magnetic field distribution above or
below the single coil structure. Advantageously, in certain
aspects, the substantially uniform magnetic field may be
constructed without use of a parasitic loop, reducing losses due to
added resistance from the parasitic loop. The distance from the
single coil structure to where the substantially uniform magnetic
field is strongest may be approximately 3 millimeters to 40
millimeters above or below the single coil structure in some
aspects. Further, the single coil structure may be sized to produce
a magnetic field sufficiently large to simultaneously charge more
than one mobile phone. Given the exemplary aspects discussed in
this disclosure, the uniform magnetic field may also permit devices
to wirelessly receive power even above the outer edges of the
primary coil structure.
The spacings between consecutive turns of a single coil structure
may be designed to increase from an outermost turn to the center of
the single coil structure, in part, so that alternating current
resistances at high frequencies may be diminished. In certain
aspects, such a design may be effective for decreasing resistance
and corresponding energy losses at operating frequencies of about
6.78 MHz.
Information and signals may be represented using any of a variety
of different technologies and techniques. For example, data,
instructions, commands, information, signals, bits, symbols, and
chips that may be referenced throughout the above description may
be represented by voltages, currents, electromagnetic waves,
magnetic fields or particles, optical fields or particles, or any
combination thereof.
The various illustrative logical blocks, modules, circuits, and
algorithm steps described in connection with the embodiments
disclosed herein may be implemented as electronic hardware,
computer software, or combinations of both. To clearly illustrate
this interchangeability of hardware and software, various
illustrative components, blocks, modules, circuits, and steps have
been described above generally in terms of their functionality.
Whether such functionality is implemented as hardware or software
depends upon the particular application and design constraints
imposed on the overall system. The described functionality may be
implemented in varying ways for each particular application, but
such implementation decisions should not be interpreted as causing
a departure from the scope of the embodiments of the invention.
The various illustrative blocks, modules, and circuits described in
connection with the embodiments disclosed herein may be implemented
or performed with a general purpose processor, a Digital Signal
Processor (DSP), an Application Specific Integrated Circuit (ASIC),
a Field Programmable Gate Array (FPGA) or other programmable logic
device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the
functions described herein. A general purpose processor may be a
microprocessor, but in the alternative, the processor may be any
conventional processor, controller, microcontroller, or state
machine. A processor may also be implemented as a combination of
computing devices, e.g., a combination of a DSP and a
microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration.
The steps of a method or algorithm and functions described in
connection with the embodiments disclosed herein may be embodied
directly in hardware, in a software module executed by a processor,
or in a combination of the two. If implemented in software, the
functions may be stored on or transmitted over as one or more
instructions or code on a tangible, non-transitory
computer-readable medium. A software module may reside in Random
Access Memory (RAM), flash memory, Read Only Memory (ROM),
Electrically Programmable ROM (EPROM), Electrically Erasable
Programmable ROM (EEPROM), registers, hard disk, a removable disk,
a CD ROM, or any other form of storage medium known in the art. A
storage medium is coupled to the processor such that the processor
can read information from, and write information to, the storage
medium. In the alternative, the storage medium may be integral to
the processor. Disk and disc, as used herein, includes compact disc
(CD), laser disc, optical disc, digital versatile disc (DVD),
floppy disk and blu ray disc where disks usually reproduce data
magnetically, while discs reproduce data optically with lasers.
Combinations of the above should also be included within the scope
of computer readable media. The processor and the storage medium
may reside in an ASIC. The ASIC may reside in a user terminal. In
the alternative, the processor and the storage medium may reside as
discrete components in a user terminal.
For purposes of summarizing the disclosure, certain aspects,
advantages and novel features of the inventions have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the invention may be embodied or
carried out in a manner that achieves or optimizes one advantage or
group of advantages as taught herein without necessarily achieving
other advantages as may be taught or suggested herein.
Various modifications of the above described embodiments will be
readily apparent, and the generic principles defined herein may be
applied to other embodiments without departing from the spirit or
scope of the invention. Thus, the present invention is not intended
to be limited to the embodiments shown herein but is to be accorded
the widest scope consistent with the principles and novel features
disclosed herein.
* * * * *