U.S. patent application number 13/830161 was filed with the patent office on 2014-07-10 for system and method for powering or charging multiple receivers wirelessly with a power transmitter.
This patent application is currently assigned to MOJO MOBILITY, INC.. The applicant listed for this patent is MOJO MOBILITY, INC.. Invention is credited to Afshin Partovi.
Application Number | 20140191568 13/830161 |
Document ID | / |
Family ID | 51060443 |
Filed Date | 2014-07-10 |
United States Patent
Application |
20140191568 |
Kind Code |
A1 |
Partovi; Afshin |
July 10, 2014 |
SYSTEM AND METHOD FOR POWERING OR CHARGING MULTIPLE RECEIVERS
WIRELESSLY WITH A POWER TRANSMITTER
Abstract
A system and method for powering or charging multiple receivers
wirelessly with a power transmitter. In accordance with an
embodiment, to enable ease of use, it is desirable that the
receiver can be placed on a larger surface area charger without the
need for specific alignment of the position of the receiver; that
the system can be used to charge or power multiple devices of
similar or different power and voltage requirements or operating
with different wireless charging protocols on or near the same
surface; and that a degree of freedom is provided with respect to
vertical distance (away from the surface of the charger) between
the charger and the receivers. Such features enable improved
functionality with devices, vehicles, or other products, including,
for example, charging of electric vehicles (EV), and trains.
Inventors: |
Partovi; Afshin; (Sunnyvale,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MOJO MOBILITY, INC.; |
|
|
US |
|
|
Assignee: |
MOJO MOBILITY, INC.
Sunnyvale
CA
|
Family ID: |
51060443 |
Appl. No.: |
13/830161 |
Filed: |
March 14, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61749108 |
Jan 4, 2013 |
|
|
|
Current U.S.
Class: |
307/9.1 ; 307/11;
307/31 |
Current CPC
Class: |
H02J 50/12 20160201;
H02M 3/33576 20130101; Y02T 90/12 20130101; H02J 50/70 20160201;
H02J 50/90 20160201; H02M 2001/0058 20130101; H02J 7/02 20130101;
H02J 50/40 20160201; H02J 7/00712 20200101; H02M 2001/0064
20130101; H02M 3/33515 20130101; H02M 2001/007 20130101; H02J 50/80
20160201; H02M 3/337 20130101; H02J 7/025 20130101; H02J 50/60
20160201; H01F 38/14 20130101 |
Class at
Publication: |
307/9.1 ; 307/11;
307/31 |
International
Class: |
H02J 7/02 20060101
H02J007/02; H01F 38/14 20060101 H01F038/14 |
Claims
1. A system for powering or charging multiple receivers wirelessly
with a power transmitter comprising: a base unit having one or more
transmitter coils; and one or more components within the base unit
and/or a mobile device to be charged by the base unit, including a
degree of positioning freedom, and support for different voltages,
wireless power protocols, and/or power levels, for powering or
charging multiple receivers wirelessly.
2. The system of claim 1, wherein the components for use in
powering the multiple receivers from the same charger include a
coil and/or magnetic material and/or structure system that allows
position free multi-charging, including one or more magnetic
resonance or loosely coupled systems, flux guide structures,
Magnetic Coupling, Magnetic Aperture coil and/or other coil and/or
magnetic material and structures.
3. The system of claim 1, wherein the components for use in
powering the multiple receivers from the same charger include a
receiver having an output regulator stage with a large acceptable
operating input voltage range.
4. The system of claim 1, wherein the components for use in
powering the multiple receivers from the same charger operate a
communication method that allows multiple receivers to communicate
with a single charger and avoid message collision.
5. The system of claim 4, wherein, to avoid message collisions,
each receiver is configured to send messages at time intervals
which are random or different from other receivers, such that if a
collision occurs with a particular message, the charger can ignore
that particular message, or reset the communication.
6. The system of claim 1, wherein the system uses a control
algorithm for power transfer to the multiple receivers, which
attempts to keep all of the receivers operating simultaneously such
that the range of each particular receiver's voltage at its output
stage regulator input is within the acceptable operating range for
that particular receiver.
7. The system of claim 1, wherein the system includes components
for use in powering the multiple receivers from the same charger,
including support for one or more of the following features:
standby and initial set up/ping or identification of receivers;
changes to number of receivers due to introduction or removal of a
receiver during operation; handling of changes to power requirement
of one or more receivers due to movement of the receiver in an X,
Y, or Z direction or change in their load; end of charge at one or
more receivers; foreign object or metal detection; and/or over
temperature and/or other fault handling in the system.
8. The system of claim 1, wherein the system includes a combination
of physical power layer (PPL), physical communication and control
layer (PCCL), command and control layer (CCL), and user application
layer (UAL) components, for use in powering or charging the
multiple receivers wirelessly.
9. The system of claim 8, wherein the PPL comprises the mobile
device, coil, magnetic and other hardware components, systems and
specifications in the base unit transmitter, or chargers and
receivers that allow power to be transmitted from one or more
transmitters to one or more receivers.
10. The system of claim 8, wherein the PCCL comprises components,
hardware, systems and specifications that allow device
identification, communication and control of the WPT, and
components used to detect and interrupt power flow, such as
interlock switches, temperature or magnetic field detectors, and
charging flags.
11. The system of claim 8, wherein the CCL comprises a firmware
and/or software and associated protocols and specifications in
transmitters and/or chargers and receivers that control the charger
and receiver operations and allow detection and/or identification
of the receivers, control of power transmission, power regulation,
end of charge actions and/or handling of any extraordinary or fault
conditions.
12. The system of claim 8, wherein the UAL comprises physical,
software and hardware connections, communications, control,
protocols and specifications for connectivity and display or
execution of additional functionality between transmitters or
chargers and/or receivers and devices, systems, environments or
vehicles where they are integrated or attached to.
13. The system of claim 1, wherein the base unit uses a saturable
magnetic layer placed above the charger coil area to shield the
charger magnetic layer from the surrounding area for use with a
Magnetic Aperture (MA) or Magnetic Coupling (MC) receiver.
14. The system of claim 1, wherein the base unit uses a magnetic
layer that extends beyond the physical dimensions of the base unit
coil or coils on the side opposing the receiver or receivers and
provides a flux return path to allow better guiding of the
electromagnetic power flux and some degree of positioning freedom
and efficient power transfer to one or more receivers.
15. The system of claim 1, wherein the receiver or receivers use
magnetic layer(s) that extends beyond the physical dimensions of
the receiver coil or coils on the side opposing the base unit and
provide a flux return path to allow some degree of positioning
freedom and efficient power transfer from the base unit to one or
more receivers.
16. The system of claim 1, wherein the base unit is provided within
an automobile, train, bus or other vehicle, for use in charging or
powering one or more mobile devices each having receivers, within
the vehicle.
17. The system of claim 1, wherein the receiver is incorporated
within or otherwise coupled to an electric train, bus, automobile
or other vehicle, and the base unit is used to charge the electric
train, bus, automobile or other vehicle.
18. A method for powering or charging multiple receivers wirelessly
with a power transmitter comprising: providing a system including a
base unit having one or more transmitter coils; and providing one
or more components within the base unit and/or a mobile device to
be charged by the base unit, including a degree of positioning
freedom, and support for different voltages, wireless power
protocols, and/or power levels, for powering or charging multiple
receivers wirelessly.
19. The method of claim 18, wherein the components for use in
powering the multiple receivers from the same charger include a
coil and appropriate magnetic material and structure system that
allows position free multi-charging, including one or more magnetic
resonance or loosely coupled systems, flux guide structures,
Magnetic Coupling, Magnetic Aperture coil and/or other magnetic
material and structures.
20. The method of claim 18, wherein the components for use in
powering the multiple receivers from the same charger includes a
receiver having an output regulator stage with a large acceptable
operating input voltage range.
21. The method of claim 18, wherein the components for use in
powering the multiple receivers from the same charger operate a
communication method that allows multiple receivers to communicate
with a single charger and avoid message collision.
22. The method of claim 21, wherein, to avoid message collisions,
each receiver is configured to send messages at time intervals
which are random or different from other receivers, such that if a
collision occurs with a particular message, the charger can ignore
that particular message, or reset the communication.
23. The method of claim 18, wherein the system uses a control
algorithm for power transfer to the multiple receivers, which
attempts to keep all of the receivers operating simultaneously such
that the range of each particular receiver's voltage at its output
stage regulator input is within the acceptable operating range for
that particular receiver.
24. The method of claim 18, wherein the system includes components
for use in powering the multiple receivers from the same charger,
including support for one or more of the following features:
standby and initial set up/ping or identification of receivers;
changes to number of receivers due to introduction or removal of a
receiver during operation; handling of changes to power requirement
of one or more receivers due to movement of the receiver in an X,
Y, or Z direction or change in their load; end of charge at one or
more receivers; foreign object or metal detection; and/or over
temperature and/or other fault handling in the system.
25. The method of claim 18, wherein the system includes a
combination of physical power layer (PPL), physical communication
and control layer (PCCL), command and control layer (CCL), and user
application layer (UAL) components, for use in powering or charging
the multiple receivers wirelessly.
26. The method of claim 25, wherein the PPL comprises the mobile
device, coil, magnetic and other hardware components, systems and
specifications in the base unit transmitter, or chargers and
receivers that allow power to be transmitted from one or more
transmitters to one or more receivers.
27. The method of claim 25, wherein the PCCL comprises components,
hardware, systems and specifications that allow device
identification, communication and control of the WPT, and
components used to detect and interrupt power flow, such as
interlock switches, temperature or magnetic field detectors, and
charging flags.
28. The method of claim 25, wherein the CCL comprises a firmware
and/or software and associated protocols and specifications in
transmitters and/or chargers and receivers that control the charger
and receiver operations and allow detection and/or identification
of the receivers, control of power transmission, power regulation,
end of charge actions and/or handling of any extraordinary or fault
conditions.
29. The method of claim 25, wherein the UAL comprises physical,
software and hardware connections, communications, control,
protocols and specifications for connectivity and display or
execution of additional functionality between transmitters or
chargers and/or receivers and devices, systems, environments or
vehicles where they are integrated or attached to.
30. The method of claim 25, wherein the base unit uses a saturable
magnetic layer placed above the charger coil area to shield the
charger magnetic layer from the surrounding area for use with a
Magnetic Aperture (MA) or Magnetic Coupling (MC) receiver.
31. The method of claim 18, wherein the base unit uses a magnetic
layer that extends beyond the physical dimensions of the base unit
coil or coils on the side opposing the receiver or receivers and
provides a flux return path to allow better guiding of the
electromagnetic power flux and some degree of positioning freedom
and efficient power transfer to one or more receivers.
32. The method of claim 18, wherein the receiver or receivers use
magnetic layer(s) that extends beyond the physical dimensions of
the receiver coil or coils on the side opposing the base unit and
provide a flux return path to allow some degree of positioning
freedom and efficient power transfer from the base unit to one or
more receivers.
33. The method of claim 18, wherein the base unit is provided
within an automobile, train, bus or other vehicle, for use in
charging or powering one or more mobile devices each having
receivers, within the vehicle.
34. The method of claim 18, wherein the receiver is incorporated
within or otherwise coupled to an electric train, bus, automobile
or other vehicle, and the base unit is used to charge the electric
train, bus, automobile or other vehicle.
Description
CLAIM OF PRIORITY
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application titled "SYSTEM AND METHOD FOR
POWERING OR CHARGING MULTIPLE RECEIVERS WIRELESSLY WITH A POWER
TRANSMITTER", Application No. 61/749,108, filed Jan. 4, 2013, which
application is herein incorporated by reference.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application is related to U.S. Patent Publication No.
20120235636 (U.S. patent application Ser. No. 13/352,096) titled
"SYSTEMS AND METHODS FOR PROVIDING POSITIONING FREEDOM, AND SUPPORT
OF DIFFERENT VOLTAGES, PROTOCOLS, AND POWER LEVELS IN A WIRELESS
POWER SYSTEM", filed Jan. 17, 2012, which claims the benefit of
priority to U.S. Provisional Patent Application No. 61/433,883,
titled "SYSTEM AND METHOD FOR MODULATING THE PHASE AND AMPLITUDE OF
AN ELECTROMAGNETIC WAVE 1N MULTIPLE DIMENSIONS", filed Jan. 18,
2011; U.S. Provisional Patent Application No. 61/478,020, titled
"SYSTEM AND METHOD FOR MODULATING THE PHASE AND AMPLITUDE OF AN
ELECTROMAGNETIC WAVE IN MULTIPLE DIMENSIONS", filed Apr. 21, 2011;
and U.S. Provisional Patent Application No. 61/546,316, titled
"SYSTEMS AND METHODS FOR PROVIDING POSITIONING FREEDOM, AND SUPPORT
OF DIFFERENT VOLTAGES, PROTOCOLS, AND POWER LEVELS IN A WIRELESS
POWER SYSTEM", filed Oct. 12, 2011; and is also related to U.S.
patent application Ser. No. 13/828,789, titled "SYSTEMS AND METHODS
FOR WIRELESS POWER TRANSFER", Attorney Docket No. AFPA-01035US1,
filed Mar. 14, 2013, which claims the benefit of priority to U.S.
Provisional Patent Application titled "SYSTEMS AND METHODS FOR
PROVIDING POSITIONING FREEDOM IN THREE DIMENSIONS FOR WIRELESS
POWER TRANSFER", Application No. 61/613,792, filed Mar. 21, 2012;
each of which above applications are herein incorporated by
reference.
COPYRIGHT NOTICE
[0003] A portion of the disclosure of this patent document contains
material which is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent file or records, but otherwise
reserves all copyright rights whatsoever.
FIELD OF INVENTION
[0004] Embodiments of the invention are generally related to
systems and methods for enabling transfer of power, from a wireless
charger or power supply, to one or more receivers placed on or near
the wireless charger or power supply.
BACKGROUND
[0005] Wireless technologies for powering and charging mobile and
other electronic or electric devices, batteries and vehicles have
been developed. Such systems generally use a wireless power charger
or transmitter, and a wireless power receiver in combination, to
provide a means for transfer of power. In some systems, the charger
and receiver coil parts of the system are aligned and of comparable
or similar size. However, such operation typically requires the
user to place the device or battery to be charged in a specific
location with respect to the charger. These are the general areas
that embodiments of the invention are intended to address.
SUMMARY
[0006] In accordance with an embodiment, to enable ease of use, it
is desirable that the receiver can be placed on a larger surface
area charger without the need for specific alignment of the
position of the receiver; that the system can be used to charge or
power multiple devices of similar or different power and voltage
requirements or operating with different wireless charging
protocols on or near the same surface; and that a degree of freedom
is provided with respect to vertical distance (away from the
surface of the charger) between the charger and the receivers.
[0007] Such features enable improved functionality with devices,
vehicles, or other products, including, for example, charging of
electric vehicles (EV), and trains. Other examples include use
cases wherein the charger may need to be physically separated from
the device or battery to be charged, such as when a charger is
incorporated beneath a surface such as the center console of a car,
or under the surface of a table or desk.
[0008] In accordance with various embodiments, described herein are
systems and methods of enabling efficient wireless power transfer
and charging of devices and batteries with freedom of placement of
the devices and batteries in one or multiple (e.g., one, two or
three) dimensions. Applications include inductive or magnetic
charging and power, and particularly usage in mobile, electronic,
electric, lighting, or other devices, batteries, power tools,
kitchen, industrial, medical or dental, or military applications,
vehicles, robots, trains, and other usages. Embodiments can also be
applied generally to power supplies and other power sources and
chargers, including systems and methods for improved ease of use
and compatibility and transfer of wireless power to mobile,
electronic, electric, lighting, or other devices, batteries, power
tools, kitchen, military, medical, industrial applications and/or
vehicles.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 illustrates a wireless charger or power system that
comprises a first charger or transmitter part and a receiver
connected to a mobile or stationary device, vehicle or battery or
its charging circuit, in accordance with an embodiment.
[0010] FIG. 2 illustrates an abstraction layer model for wireless
power transfer systems, in accordance with an embodiment.
[0011] FIG. 3 illustrates a more detailed view of a wireless
charger system, in accordance with an embodiment.
[0012] FIG. 4 illustrates how charger and receiver coils can be
represented by their respective inductances, in accordance with an
embodiment.
[0013] FIG. 5 illustrates on the left configurations of a
tightly-coupled power transfer system with two individual
transmitter coils of different size, and on the right
configurations of a loosely-coupled (magnetic resonance) power
transfer system with a single individual transmitter coil, in
accordance with an embodiment.
[0014] FIG. 6 illustrates an additional geometry whereby a charger
coil is placed on a magnetic flux guide/shielding layer that
extends beyond the edges of the coil, in accordance with an
embodiment.
[0015] FIG. 7 illustrates a return magnetic flux from the charger,
in accordance with an embodiment.
[0016] FIG. 8 illustrates a homogeneous broadcast wireless power
transfer system (on the left) and an inhomogeneous broadcast
wireless power transfer system (on the right), in accordance with
an embodiment.
[0017] FIG. 9 illustrates a system using a dedicated RF
communication channel, in accordance with an embodiment.
[0018] FIG. 10 illustrates the communication between a single
charger and receiver, in accordance with an embodiment.
[0019] FIG. 11 further illustrates the interaction of a single
charger and receiver, in accordance with an embodiment.
[0020] FIG. 12 illustrates use of a single coil in the charger to
power or charge multiple receivers, in accordance with an
embodiment.
[0021] FIG. 13 illustrates transmission of data packets by the
receiver at random intervals, in accordance with an embodiment.
[0022] FIG. 14 illustrates timing of receiver data packets, in
accordance with an embodiment
[0023] FIG. 15 illustrates how a charger may periodically transmit
a sync, beacon, or query pattern, in accordance with an
embodiment.
[0024] FIG. 16 illustrates data packets transmitted by multiple
receivers and a collision, in accordance with an embodiment
[0025] FIG. 17 illustrates where three receivers respond to a ping
and begin communication transmission and a potential collision of
data packets, in accordance with an embodiment.
[0026] FIG. 18 illustrates use of a switch with a regulator in a
receiver, in accordance with an embodiment.
[0027] FIG. 19 illustrates a wirelessly powered battery pack and
receiver, in accordance with an embodiment.
[0028] FIG. 20 illustrates a battery cell circuit, in accordance
with an embodiment
[0029] FIG. 21 illustrates the high level block diagram of a
wireless power transfer system and integration of a UAL layer into
a charger and receiver, in accordance with an embodiment.
DETAILED DESCRIPTION
[0030] With the proliferation of electrical and electronic devices
and vehicles (which are considered examples of devices herein),
simple and universal methods of providing power and or charging of
these devices is becoming increasingly important.
[0031] In accordance with various embodiments, the term device,
product, or battery is used herein to include any electrical,
electronic, mobile, lighting, or other product, batteries, power
tools, cleaning, industrial, kitchen, lighting, military, medical,
dental or specialized products and vehicles, automobiles, personal
mobility (e.g., Segway) devices, buses or movable machines such as
robots or other mobile machines or other devices whereby the
product, part, or component is powered by electricity or an
internal or external battery and/or can be powered or charged
externally or internally by a generator or solar cell, fuel cell,
hand or other mechanical crank or alike.
[0032] In accordance with an embodiment, a product or device can
also include an attachable or integral skin, case, battery door or
attachable or add-on or dongle type of receiver component to enable
the user to power or charge the product, battery, or device.
[0033] Induction is defined as generation of electromotive force
(EMF) or voltage across a closed electrical path in response to a
changing magnetic flux through any surface bounded by that path.
Magnetic induction has sometimes been described in the context of
tightly-coupled cases, whereby the charger and receiver coils are
of similar sizes or the gap between them is small. Magnetic
resonance is a term that has been used recently for inductive power
transfer where the charger and receiver may be far apart or the
transmitter and receiver coils of different size. The term loosely
coupled wireless charging has also been used for these systems.
Since magnetic resonance or loosely coupled wireless charging is in
general a form of induction, in the remainder of this document the
terms induction is used for any of these systems (including
inductive or tightly coupled wireless power transfer, magnetic
resonant or loosely coupled wireless power transfer and hybrid
systems) and induction and magnetic resonance are sometimes used
interchangeably to indicate that the method of power transfer may
be in either domain or a combination thereof.
[0034] In accordance with various embodiments, an inductive power
transmitter employs a magnetic induction coil(s) transmitting
energy to a receiving coil(s) in or on a device or product, case,
battery door, or attachable or add-on component including
attachments such as a dongle or a battery inside or outside of
device or attached to device through a connector and/or a wire, or
stand-alone placed near the power transmitter platform. The
receiver can be an otherwise incomplete device that receives power
wirelessly and is intended for installation or attachment in or on
the final product, battery or device to be powered or charged, or
the receiver can be a complete device intended for connection to a
device, product or battery directly by a wire or wirelessly. As
used herein, the term wireless power, charger, transmitter or
inductive or magnetic resonance power and charger are used
interchangeably.
[0035] In accordance with an embodiment, the wireless charger can
be a flat or curved surface or part that can provide energy
wirelessly to a receiver. It can also be constructed of flexible
materials and/or coils or even plastic electronics to enable
mechanical flexibility and bending or folding to save space or for
conformity to non-flat surfaces.
[0036] In accordance with an embodiment, the wireless charger may
be directly powered by an AC power input, DC power, or other power
source such as a car, motorcycle, truck or other vehicle or
airplane or boat or ship power outlet, or vehicle, boat, ship or
airplane itself, primary (non-rechargeable) or rechargeable
battery, solar cell, fuel cell, mechanical (hand crank, wind, water
source, etc.), nuclear source or other or another wireless charger
or power supply or a combination thereof. In addition, the wireless
charger may be powered by a part such as a rechargeable battery
which is itself in turn recharged by another source such as an AC
or DC power source, vehicle, boat or ship or airplane outlet or
vehicle, boat or ship or airplane itself, solar cell, fuel cell, or
mechanical (hand crank, wind, water, etc.) or nuclear source, etc.
or a combination thereof.
[0037] In accordance with various embodiments, in cases where the
wireless charger is powered by a rechargeable source such as a
battery, the battery can also be itself in turn inductively charged
by another wireless charger. The wireless charger can be a
stand-alone part, device, or product, or may be incorporated into
another electric or electronics device, table, desk chair, armrest,
TV stand or mount or furniture or vehicle or airplane or marine
vehicle or boat or objects such as a table, desk, chair,
counter-top, shelving or check out or cashier counters, kiosk, car
seat, armrest, car console, car door, netting, cup holder,
dashboard, glovebox, etc., airplane tray, computer, laptop,
netbook, tablet, phone, display, TV, magnetic, optical or
semiconductor storage or playback device such as hard drive, solid
state storage drive, optical players, etc., cable or game console,
computer pads, toys, clothing, bags, case or backpack, belt or
holster, etc., industrial, medical, dental, military or kitchen
counter, area, devices and appliances, phones, cameras, radios,
stereo systems, speakers, etc. The wireless charger may also have
other functions built in, or be constructed such that it is modular
and additional capabilities/functions can be added as needed.
[0038] In accordance with various embodiments, some of these
capabilities/functions include an ability to provide higher power,
charge more devices, exchange the top surface or exterior box or
cosmetics, operate by internal power as described above through use
of a battery and/or renewable source such as solar cells,
communicate and/or store data from a device, provide communication
between the device and other devices or the charger and/or a
network, etc. An example is a basic wireless charger that has the
ability to be extended to include a rechargeable battery pack to
enable operation without external power. Examples of products or
devices powered or charged by the induction transmitter and
receiver include but are not limited to batteries, cell phones,
smart phones, cordless phones, communication devices, heads-up
Displays, 3-d TV glasses, display or communication glasses such as
Google Glass, pagers, personal data assistants, portable media
players, global positioning (GPS) devices, powered headphones or
noise cancelling headphones, Bluetooth headsets and other devices,
shavers, watches, tooth brushes, calculators, cameras, optical
scopes, infrared viewers, computers, laptops, tablets, netbooks,
keyboards, computer mice, book readers or email devices, pagers,
computer monitors, televisions, music or movie players and
recorders, storage devices, radios, clocks, speakers, gaming
devices, game controllers, toys, remote controllers, power tools,
cash register, delivery or other type of scanners, construction
tools, office equipment, robots including vacuum cleaning robots,
floor washing robots, pool cleaning robots, gutter cleaning robots
or robots used in hospital, clean room, military or industrial
environments, industrial tools, mobile vacuum cleaners, medical or
dental tools, medical stretcher batteries, military equipment or
tools, kitchen appliances, mixers, cookers, can openers, food or
beverage heaters or coolers such as electrically powered beverage
mugs, massagers, adult toys, lights or light fixtures, signs or
displays, or advertising applications, electronic magazines or news
papers or magazines or newspapers containing an electronic and/or
display part, printers, fax machines, scanners, electric vehicles,
electric golf carts, buses, motorcycles or bicycles, Segway type of
devices, trains or other vehicles or mobile transportation
machines, and other battery or electrically powered devices or
products or a product that is a combination of the products listed
above.
[0039] In accordance with an embodiment, the receiver and/or the
charger can be incorporated into a bag, carrier, skin, clothing,
case, packaging, product packaging or box, crate, box, display case
or rack, table, bottle or device etc. to enable some function
inside the bag, carrier, skin, clothing, case, packaging, product
packaging or box, crate, box, display case or rack, table, bottle
(such as, e.g., causing a display case or packaging to display
promotional information or instructions, or to illuminate) and/or
to use the bag, carrier, skin, clothing, case, packaging, product
packaging or box, crate, box, stand or connector, display case or
rack, table, bottle, etc., to power or charge another device or
component somewhere on or nearby.
[0040] In accordance with various embodiments, the product or
device does not necessarily have to be portable and/or contain a
battery to take advantage of induction or wireless power transfer.
For example, a lighting fixture or a computer monitor that is
typically powered by an AC outlet or a DC power supply may be
placed on a table top and receive power wirelessly. The wireless
receiver may be a flat or curved surface or part that can receive
energy wirelessly from a charger. The receiver and/or the charger
can also be constructed of flexible materials and/or coils or even
plastic electronics to enable mechanical flexibility and bending or
folding to save space or for conformity to non-flat surfaces.
[0041] In accordance with various embodiments, many of these
devices contain internal batteries, and the device may or may not
be operating during receipt of power. Depending on the degree of
charge status of the battery or its presence and the system design,
the applied power may provide power to the device, charge its
battery or a combination of the above. The terms charging and/or
power are used interchangeably herein to indicate that the received
power can be used for either of these cases or a combination
thereof. In accordance with various embodiments, unless
specifically described, these terms are therefore used
interchangeably. Also, unless specifically described herein, in
accordance with various embodiments, the terms charger power supply
and transmitter are used interchangeably.
[0042] As shown in FIG. 1, in accordance with an embodiment 100, a
wireless charger or power system 100 comprises a first charger or
transmitter part, and a receiver connected to a mobile or
stationary device, vehicle or battery or its charging circuit to
provide electric power to power or charge the mobile or stationary
device, vehicle or its battery.
[0043] FIG. 1 shows a case where one charger or power transmitter
is charging or powering one receiver. However, in a more general
case, the transmitter may comprise one or more transmitters or
chargers operating at different power levels and/or using different
protocols to power one or more receivers operating at different
power levels, voltages and/or protocols.
[0044] In accordance with an embodiment, using an analogy to the
abstraction layer model used for Open Systems Interconnection (OSI)
model for communication systems, a high level, generalized Wireless
Power System (WPT) such as shown 120 in FIG. 2 can comprise the
following layers:
Physical Layer (PL/PPL, PCCL)
[0045] In accordance with an embodiment, this layer comprises a
plurality of sub layers, as described in further detail below.
[0046] Physical Layer (PL)/Physical Power Layer (PPL): In
accordance with an embodiment, this layer comprises the device,
coil, magnetic and other hardware components, systems and
specifications in the transmitters or chargers and receivers that
allow power to be transmitted from one or more transmitters to one
or more receivers. The components and the power transmitted or
distributed to the receivers are shown in solid lines and blocks in
FIG. 2. In cases where the receiver includes a battery charging
circuit, the PPL may extend to include the battery charging and any
possible protection circuit, and provide an output power to the
battery to charge it.
[0047] Physical Communication and Control Layer (PCCL): In
accordance with an embodiment, this layer provides the components,
hardware, systems and specifications that allow device
identification, communication and control of the WPT, and any
systems used to detect and interrupt power flow, such as interlock
switches or alignment detectors, temperature or magnetic field
detectors, charging flags, etc. For example, this layer may
comprise the components and systems to allow in-band, load
modulation, or out-of-band RF. optical, or other communication
systems.
Command and Control Layer (CCL)
[0048] In accordance with an embodiment, this layer is the firmware
and/or software and associated protocols and specifications in
transmitters and/or chargers and receivers that control the charger
and receiver operations and allow detection and/or identification
of the receivers, control of power transmission, power regulation,
end of charge actions and handling of any extraordinary or fault
conditions. This layer can operate in a bi-directional or
uni-directional manner between one or more chargers and receivers.
In accordance with an embodiment, as shown in FIG. 2, the
communication is shown as the dotted line between the PCCLs.
User Application Layer (UAL)
[0049] In accordance with an embodiment, this layer provides
physical, software and hardware connections, communications,
control, protocols and specifications for connectivity and display
or execution of additional functionality between
transmitters/chargers and/or receivers and devices, systems,
environments or vehicles where they are integrated or attached to.
Examples may include implementations where the transmitter/charger
is integrated into an electronic device (e.g., laptop or computer)
and during charging may show additional information such as
charging state of the receiver battery or allow the receiver to
control the process. In accordance with an embodiment, as shown in
FIG. 2, the communication in this layer is shown as double dotted
lines between the charger/receiver or device, and the charger or
receiver or external communication wired or wireless networks. In
accordance with an embodiment, this layer may also include any
application or apps that may run on the charger, its host device
(if the charger is built into or is part of or attached to another
device or vehicle), the receiver or the device being charged or
powered. These applications bring extra functionality and
convenience to the user.
[0050] The following section describes components of a wireless
charging/power system according to the layers described above, in
accordance with an embodiment.
Physical Layer (PL)/Physical Power Layer (PPL):
[0051] In accordance with an embodiment, the charger/transmitter
Physical Power Layer (PPL) can generate a repetitive power signal
pattern (such as a sinusoid or square wave from 10's of Hz to
several MHz or even higher, but typically in the 100 kHz to several
MHz range) with its coil drive circuit and a coil or antenna for
transmission of the power.
[0052] The charger or transmitter typically also includes a
communication and regulation/control system (Physical Communication
and Control Layer, PCCL) that detects a receiver and/or turns the
applied power on or off and/or modify the amount of applied power
by mechanisms such as changing the amplitude, frequency or duty
cycle, etc., or a change in the resonant condition by varying the
impedance (capacitance or inductance) of the charger, or a
combination thereof of the applied power signal to the coil or
antenna.
[0053] In accordance with an embodiment, the power section (coil
drive circuit and receiver power section) can be a resonant
converter, resonant, full bridge, half bridge, E-class, zero
voltage or current switching, flyback, or any other appropriate
power supply topology.
[0054] FIG. 3 shows a more detailed view of the wireless charger
system 130 in accordance with an embodiment, with a resonant
converter geometry, wherein a pair of transistors Q1 and Q2 (such
as FETs, MOSFETs, or other types of switch) are driven by a
half-bridge driver IC and the voltage is applied to the coil L1
through one or more capacitors shown as C1. In accordance with an
embodiment, the charger can also be the whole or part of the
electronics, coil, shield, or other part of the system required for
transmitting power wirelessly. The electronics may comprise
discrete components or microelectronics that when used together
provide the wireless charger functionality, or comprise an
Application Specific Integrated Circuit (ASIC) chip or chipset that
is specifically designed to function as the whole or a substantial
part of the electronics for wireless charger system. It may also
comprise Multi-Chip Modules (MCM) that comprise bare ICs that are
combined and connected onto a single larger integrated package to
decrease the footprint and cost of the overall circuit and/or
increase its reliability.
[0055] In accordance with an embodiment, as shown in FIG. 3, the
second part of the PPL system is a receiver that includes a coil or
antenna to receive power, a method for change of the received AC
voltage to DC voltage, such as rectification and smoothing with one
or more rectifiers or a bridge or synchronous rectifier, etc. and
one or more capacitors.
[0056] In cases where the voltage at the load does not need to be
kept within a tight tolerance or can vary regardless of the load
resistance or the resistance of the load is always constant, the
rectified and smoothed output of the receiver can be directly
connected to a load.
[0057] Examples of this embodiment may be in lighting applications,
applications where the load is a constant resistance such as a
heater or resistor or thermoelectric or Peltier element, etc. In
these cases, the receiver system can be quite simple and
inexpensive.
[0058] In many other cases, the resistance or impedance of the load
changes during operation. This includes cases where the receiver is
connected to a device whose power needs may change during operation
or when the receiver is used to charge a battery. In these cases,
the output voltage may need to be regulated so that it stays within
a range or tolerance during the variety of operating conditions. In
these cases, the receiver may optionally include a DC to DC
converter or regulator such as a linear, switching, buck, boost or
buck/boost, etc. regulator and/or switch for the output power. The
receiver may also include a switch between the DC output of the
receiver coil and the rectification and smoothing stage V.sub.1 and
its output or a switch between the output of the regulator stage to
a device or battery or a device case or skin or a device to be
charged or battery.
[0059] In cases where the receiver is used to charge a battery or
device, the receiver may also include a regulator, battery charger
IC or circuitry and/or battery protection circuit and associated
transistors, etc. In addition, the receiver may include a switch to
allow switching between a wired and wireless method of charging or
powering a device or its battery.
[0060] In accordance with an embodiment, the receiver may
optionally include a reactive component (inductor or capacitor) in
parallel or in series with the receiver coil to increase the
resonance of the system. Effect of such a resonance becomes more
important as the coils are operated farther from each other or a
mismatched size for the receiver and the charger/transmitter coil
is used. In such conditions where low coupling coefficient is used,
the importance of the resonance in the receiver is more
significant. An example of a low coupling coefficient system may be
when a larger size charger coil and smaller receiver coils are
used. Such an optional capacitor is shown as C2 in FIG. 3 and may
be in series or in parallel with the receiver coil L2. The charger
and/or receiver coils may also include impedance matching circuits
and/or appropriate magnetic material layers behind (on the side
opposite to the coil surfaces facing each other) them to increase
their inductance and/or to shield the magnetic field leakage to
surrounding area or to guide the magnetic field appropriately.
[0061] In many of the embodiments and figures described herein, the
resonant capacitor C2 in the receiver is shown in a series
architecture. This is intended only as a representative
illustration, and in accordance with various embodiments this
capacitor may be used in series or parallel with the receiver coil.
Similarly, the charger is generally shown in an architecture where
the resonant capacitor is in series with the coil. System
architectures where the capacitor C1 is in parallel with the
charger coil are also possible.
[0062] In accordance with an embodiment, one method of controlling
the amount of received power in the receiver in such low coupling
coefficients is to include variable or switchable reactive
components (capacitors and/or inductors) in parallel or series with
the receiver coil whereby tuning these elements would allow the
receiver to change its resonant condition to affect the amount of
power delivered to the device, load or battery.
[0063] In accordance with an embodiment, the charger or transmitter
coil and the receiver coil can have any shape desired and may be
constructed of PCB, wire, Litz wire, or a combination thereof.
[0064] To reduce resistance, the coils can be constructed of
multiple parallel tracks or wires in multiple layers of the PCB
and/or wire construction. For PCB construction, the multiple layers
can be in different sides of a PCB and/or different layers and
layered/designed appropriately to provide optimum field pattern,
uniformity, inductance, and/or resistance or Quality factor (Q) for
the coil. Various materials can be used for the coil conductor such
as different metals and/or magnetic material or plastic conductors,
etc. Typically, copper with low resistivity may be used but other
conductive materials usage is also possible. The design should also
take into account the skin effect of the material used at the
frequency of operation to preferably provide low resistance.
[0065] In accordance with an embodiment, the receiver can be an
integral part of a device or battery as described above, or can be
an otherwise incomplete device that receives power wirelessly and
is intended for installation or attachment in or on the final
product, battery or device to be powered or charged, or the
receiver can be a complete device intended for connection to a
device, product or battery directly by a wire or wirelessly.
Examples include replaceable covers, skins, cases, doors, jackets,
surfaces, etc for devices or batteries that would incorporate the
receiver or part of the receiver and the received power would be
directed to the device through connectors in or on the device or
battery or the normal wired connector (or power jack) of the device
or battery. The receiver may also be a part or device similar to a
dongle or insert etc. that can receive power on or near the
vicinity of a charger and direct the power to a device or battery
to be charged or powered through a wire and/or appropriate
connector. Such a receiver may also have a form factor that would
allow it to be attached in an inconspicuous manner to the device
such as a part that is attached to the outer surface at the bottom,
front, side, or back side of a laptop, netbook, tablet, phone, game
player, camera, headset or other electronic device and route the
received power to the input power connector, battery connector or
jack of the device.
[0066] In accordance with an embodiment, the connector of such a
receiver may be designed such that it has a pass through or a
separate connector integrated into it so that a wire cable for
providing wired charging/power or communication can be connected to
the connector without removal of the connector thus allowing the
receiver and its connector to be permanently or semi-permanently be
attached to the device throughout its operation and use.
[0067] In a more integrated approach, the coil, shield and/or the
receiver circuit may be integrated into the construction of the
electric or electronic device and be an integral part of the
operation of the device which is powered or charged primarily or as
an option (in addition to wired charging) through the wireless
power received from the receiver. Many other variations of the
receiver implementation are possible and these examples are not
meant to be exhaustive.
[0068] In accordance with an embodiment, the receiver can also be
the whole or part of the electronics, coil, shield, or other part
of the system required for receiving power wirelessly. The
electronics may comprise discrete components or microcontrollers
that when used together provide the wireless receiver
functionality, or comprise an Application Specific Integrated
Circuit (ASIC) chip or chipset or MCM that is specifically designed
to function as the whole or a substantial part of the electronics
for wireless receiver system.
[0069] In accordance with an embodiment, in any of the systems
described above, as shown 140 in FIG. 4, the charger and receiver
coils can be represented by their respective inductances by
themselves (L1 and L2) and the mutual inductance between them M
which is dependent on the material between the two coils and their
position with respect to each other in x, y, and z dimensions. The
coupling coefficient between the coils k is given by:
k=M/(L1*L2).sup.1/2
[0070] The coupling coefficient is a measure of how closely the two
coils are coupled and may range from 0 (no coupling) to 1 (very
tight coupling). In coils with small overlap, large gap between
coils or dissimilar coils (in size, number of turns, coil winding
or pattern overlap, etc.), this value can be smaller than 1.
[0071] In many cases, for the systems described above, the
transmitter and receiver coils may be of similar, although not
necessarily same sizes and are generally aligned laterally to be
able to transfer power efficiently. For coils of similar size, this
would typically require the user to place the device and/or
receiver close to alignment with respect to the transmitter
coil.
[0072] For example, for a transmitter/receiver coil of 30 mm
diameter, this would require lateral (x,y) positioning within 30 mm
or less so there is some degree of overlap between the coils. In
practice, a considerable degree of overlap is necessary to achieve
high output powers and efficiencies. This may be achieved by
providing mechanical or other mechanisms such as indentations,
protrusions, walls, holders, fasteners, etc. to align the
parts.
[0073] However for a universal charger/power supply to be useful
for charging or powering a range of devices, a design able to
accept any device and receiver is desirable. For this reason, in
accordance with an embodiment, a flat or somewhat curved
charger/power supply surface that can be used with any type of
receiver may be used. To achieve alignment in this case, markings,
small protrusions or indentations and/or audio and/or visual aids
or similar methods can be used. Another method includes using
magnets, or magnet(s) and magnetic or ferrite magnetic attractor
material(s) that can be attracted to a magnet in the
transmitter/charger and receiver. In these methods, typically a
single charger/transmitter and receiver are in close proximity and
aligned to each other.
[0074] For even greater ease of use, it may be desirable to be able
to place the device to be charged/powered over a larger area,
without requiring precise alignment of coils.
[0075] Several other methods that address the topic of position
independence have been described previously. For example, as
described in U.S. Patent Publication No. 20070182367 and U.S.
Patent Publication No. 20090096413, both of which applications are
herein incorporated by reference, an embodiment comprising multiple
transmitter coils arranged in a two-dimensional array to cover and
fill the transmitter surface is described. When a receiver is
placed on the surface of such a coil array, the transmitter coil
with the largest degree of overlap with the receiver is detected
and activated to allow optimum power transmission and position
independent operation.
[0076] In another architecture, each transmitter (or charger) coil
center includes a sensor inductor (for example, E. Waffenschmidt,
and Toine Staring, 13th European Conference on Power Electronics
and Applications, Barcelona, 2009. EPE '09. pp. 1-10). The receiver
coil includes a soft magnetic shield material that shifts the
resonance frequency response of the system and can be sensed by a
sensor in the transmitter to switch the appropriate coil on. The
drawback of this system is that three layers of overlapping coils
with a sensor and detection circuit at the center of each is
required, adding to the complexity and cost of the system.
[0077] Other variations of the above or a combination of techniques
can be used to detect the appropriate transmitter coil.
[0078] In accordance with other embodiments, described in U.S.
Patent Publication No. 20070182367 and U.S. Patent Publication No.
20090096413, the charger/power supply may contain one or more
transmitter coils that are suspended and free to move laterally in
the X-Y plane behind the top surface of the charger/power supply.
When a receiver coil is placed on the charger/power supply, the
closest transmitter coil would move laterally to position itself to
be under and aligned with the receiver coil. In general the systems
above describe the use of coils that are of similar size/shape and
in relatively close proximity to create a wireless power
system.
[0079] As described above, the coupling coefficient k is an
important factor in design of the wireless power system. In
general, wireless power systems can be categorized into two types.
One category which is called tightly coupled operates in a
parameter space where the k value is typically 0.5 or larger. This
type of system is characterized by coils that are typically similar
in size and/or spatially close together in distance (z axis) and
with good lateral (x,y) overlap. This so-called tightly coupled
system is typically associated with high power transfer
efficiencies defined here as the ratio of output power from the
receiver coil to input power to transmitter coil. The methods
described above for position independent operation (array of
transmitter coils and moving coils), typically may use tightly
coupled coils.
[0080] In contrast, for coils of dissimilar size or design or
larger transmitter to receiver distance or smaller lateral coil
overlap, the system coupling coefficient is lower. Another
important parameter, the quality factor of a transmitter (tx) and
receiver (rx) coil is defined as:
Q.sub.tx=2.pi.fL.sub.tx/R.sub.tx
Q.sub.tx=2.pi.fL.sub.rx/R.sub.rx
where f is the frequency of operation, L.sub.tx, and L.sub.rx the
inductances of the transmitter and receiver coils and R.sub.tx and
R.sub.rx their respective resistances. The system quality factor
can be calculated as follows:
Q=(Q.sub.txQ.sub.rx).sup.1/2
[0081] In general, the loosely coupled systems may have smaller
power transfer efficiencies. However, it can be shown (see for
example, E. Waffenschmidt, and Toine Staring, 13th European
Conference on Power Electronics and Applications, Barcelona, 2009.
EPE '09. pp. 1-10) that an increase of Q can compensate for smaller
k values, and reasonable or similar power transfer efficiencies can
be obtained. Such systems with dissimilar coil sizes and higher Q
values are sometimes referred to as Resonant Coupled or Resonant
systems. However, resonance is also often used in the case of
similar-size coil systems. Others, (such as Andre Kurs, Aristeidis
Karalis, Robert Moffatt, J. D. Joannopoulos, Peter Fisher, and
Marin Soljac, Science, 317, P. 83-86, 2007; and
http://newsroom.intel.com/docs/DOC-1119) have shown that with
systems with k of <0.2 due to large distance between coils (up
to 225 cm), sizeable reported power transfer efficiencies of
40%-70% can be obtained. Other types of loosely coupled system
appear to use mis-matched coils where the transmitter coil is much
larger than the receiver coil (see for example, J. J. Casanova, Z.
N. Low, J. Lin, and Ryan Tseng, in Proceedings of Radio Wireless
Symposium, 2009, pp. 530-533 and J. J. Casanova, Z. N. Low, and J.
Lin, IEEE Transactions on Circuits and Systems--II: Express Briefs,
Vol. 56, No. 11, November 2009, pp. 830-834 and a Fujitsu System
described at
http://www.fujitsu.com/global/news/pr/archives/month/2010/20100913-02.htm-
l).
[0082] Some references (e.g., U.S. Pat. Nos. 6,906,495, 7,239,110,
7,248,017, and 7,042,196) describe a loosely coupled system for
charging multiple devices whereby a magnetic field parallel to the
plane of the charger is used. In this case, the receiver contains a
coil that is typically wrapped around a magnetic material such as a
rectangular thin sheet and has an axis parallel to the plane of the
charger. To allow the charger to operate with the receiver rotated
to any angle, two sets of coils creating magnetic fields parallel
to the plane of the charger at 90 degrees to each other and driven
out of phase are used.
[0083] Such systems may have a larger transmitter coil and a
smaller receiver coil and operate with a small k value (possibly
between 0 and 0.5 depending on coil size mismatch and gap between
coils/offset of coils). The opposite case of a small transmitter
coil and larger receiver coil is also possible.
[0084] FIG. 5 shows configurations 150 for a tightly coupled power
transfer system, in accordance with an embodiment, with two
individual transmitter coils of different size powering a laptop
and a phone (left) and a loosely coupled wireless power system with
a large transmitter coil powering two smaller receiver coils in
mobile phones (right).
[0085] An ideal system with largely mis-matched (i.e. dissimilar in
size/shape) coils can potentially have several advantages: Power
can be transferred to the receiver coils placed anywhere on the
transmitter coil. Several receivers can be placed and powered on
one transmitter allowing for simpler and lower cost of transmitter.
The system with higher Q can be designed so the gap between the
transmitter and receiver coil can be larger than a tightly coupled
system leading to design of systems with more design freedom. In
practice, power transfer in distances of several cm or even higher
have been demonstrated. Power can be transferred to multiple
receivers simultaneously. In addition, the receivers can
potentially be of differing power rating or be in different stages
of charging or require different power levels and/or voltages.
[0086] In order to achieve the above characteristics and to achieve
high power transfer efficiency, the lower k value is compensated by
using a higher Q through design of lower resistance coils, etc. The
power transfer characteristics of these systems may differ from
tightly coupled systems and other power drive geometries such as
class E amplifier or Zero Voltage Switching (ZVS) or Zero Current
Switching (ZCS) or other power transfer systems may operate more
efficiently in these situations. In additions, impedance matching
circuits at the charger/transmitter and/or receiver may be required
to enable these systems to provide power over a range of load
values and output current conditions. General operation of the
systems can, however be quite similar to the tightly coupled
systems and one or more capacitors in series or parallel with the
transmitter and/or receiver coil is used to create a tuned circuit
that may have a resonance for power transfer. Operating near this
resonance point, efficient power transfer across from the
transmitter to the receiver coil can be achieved. Depending on the
size difference between the coils and operating points,
efficiencies of over 50% up to near 80% have been reported.
[0087] To provide more uniform power transfer across a coil,
methods to provide a more uniform magnetic field across a coil can
be used. One method for achieving this uses a hybrid coil
comprising a combination of a wire and PCB coils (see, for example,
X. Liu and S. Y. R. Hui, "Optimal design of a hybrid winding
structure for planar contactless battery charging platform," IEEE
Transactions on Power Electronics, vol. 23, no. 1, pp. 455-463,
2008). In another method, the transmitter coil is constructed of
Litz wire and has a pattern that is very wide between successive
turns at the center and is more tightly wound as one gets closer to
the edges (see, for example, J. J. Casanova, Z. N. Low, J. Lin, and
R. Tseng, "Transmitting coil achieving uniform magnetic field
distribution for planar wireless power transfer system," in
Proceedings of the IEEE Radio and Wireless Symposium, pp. 530-533,
January 2009). In a geometry described in U.S. Patent Publication
No. 20080067874, which application is herein incorporated by
reference, a planar spiral inductor coil is demonstrated, wherein
the width of the inductor's trace becomes wider as the trace
spirals toward the center of the coil to achieve a more uniform
magnetic field allowing more positioning flexibility for a receiver
across a transmitter surface. In yet other embodiments (F. Sato, et
al., IEEE Digest of Intermag 1999, PP. GR09, 1999), the coil can be
a meandering type of coil wherein the wire is stretched along X
direction and then folds back and makes a back and forth pattern to
cover the surface.
[0088] In accordance with an embodiment, the charger can operate
continuously, and any receiver placed on or near its surface will
bring it to resonance and will begin receiving power. The
regulation of power to the output can be performed through a
regulation stage at the receiver. Advantages of such a system
include that multiple receivers with different power needs can be
simultaneously powered in this way. The receivers may also have
different output voltage characteristics. To achieve this, the
number of turns on the receiver coil can be changed to achieve
different receiver output voltages. Without any receivers nearby,
such a charger would not be in resonance and would draw minimal
power. At end of charge, the receiver can include a switch that
will detect the minimal current draw by a device connected to the
receiver, and disconnect the output altogether and/or disconnect
the receiver coil so that the receiver is no longer drawing power.
This will bring the charger out of resonance and minimal input
current is drawn at this stage.
[0089] In accordance with an embodiment, in a practical system, in
addition to the power transfer and communication system,
appropriate electromagnetic shielding of the transmitter and
receiver is necessary and may be similar or different to the
tightly coupled systems.
[0090] The ratio of the size of the transmitter coil to the
receiver coil may be decided depending on design considerations
such as the desired number of receivers to be powered/charged at
any given time, the degree of positioning freedom needed, the
physical size of device being charged/powered, etc. In the case
that the transmitter coil is designed to be of a size to
accommodate one receiver at a time, the transmitter and receiver
coils may be of similar size thereby bringing the loosely coupled
system to the tightly coupled limit in this case.
[0091] While the loosely coupled system may have distinct
advantages and in some ways may overcome the complexities of the
multiple coil/moving coil systems employed in tightly coupled
systems to achieve position independence, traditional systems
suffer from 2 significant problems: Since a large area transmitter
coil and smaller receiver coil may be used, Electromagnetic
emission in areas of the transmitter coil not covered by the
receiver coil is present. This emission is in the near field and
drops rapidly away from the coil. Nevertheless, it can have adverse
effects on devices and/or people in the vicinity of the
transmitter. A substantial amount of power from the transmitter may
be lost from the area that is not physically covered by the
receiver coil leading to lower efficiencies and wastage of power.
It is therefore desired to benefit from the advantages of a loosely
coupled system while minimizing or avoiding problems related to
it.
[0092] In accordance with embodiments described in U.S. patent
application Ser. No. 13/352,096, published as U.S. Patent
Publication No. US20120235636, which application is herein
incorporated by reference, two techniques have been described
whereby through appropriate design of the system, a
position-independent power transfer system with reduced or no
undesirable radiation and high efficiency can be achieved. These
geometries use a saturable magnetic layer placed above the charger
coil area to shield the charger magnetic layer from the surrounding
area. For example, in accordance with an embodiment, a Magnetic
Aperture (MA) receiver includes an appropriate magnet in the
receiver that can saturate the shield layer nearby the receiver and
allow coupling of power only in that area of the charger resulting
in efficient power coupling with minimal residual electromagnetic
emission from nearby areas. In accordance with an embodiment, a
Magnetic Coupling (MC) system employs a similar geometry but uses
the increase in the resonant Electromagnetic filed between the
charger and receiver coils to self-saturate the layer and does not
require a receiver magnet to operate and achieve similar results.
These two techniques are further described in the previously filed
and incorporated herein patent applications referenced above.
[0093] FIG. 6 shows an additional geometry 160 whereby a charger
coil is placed on a magnetic flux guide/shielding layer that
extends beyond the edges of the coil. The receiver similarly has a
magnetic flux/shielding layer that extends beyond the size of the
coil allowing an overlap area between these flux layers on the top
and bottom sides of the receiver. FIG. 7 shows the return magnetic
flux from the charger that passes the receiver coil and is guided
efficiently to close on itself. Such an efficient Flux Guide (FG)
geometry results in confinement of power transfer to the area of
overlap of a receiver and charger coil and significant increase in
power transfer efficiency and reduction of undesirable
electromagnetic emission compared to Magnetic Resonance (MR)
systems. It is also possible to further decrease any potential
emissions from non-covered areas of the charger coil by covering
the charger coil with a magnetic shield layer and combining the FG
geometry with the earlier described MC or MA modes of
operation.
[0094] In accordance with an embodiment to further facilitate
coupling of the magnetic field to the receiver coil(s), the
receiver system may incorporate an additional magnetic material in
the center of the receiver coil such as shown 170 in FIG. 7. This
component may comprise the same or different material that is used
behind the receiver coil and its properties may be optimized for
its particular use. As an example, solid or flexible Ferrite
material with a desirable permeability can be incorporated. The
core may only have the thickness of the PCB or Litz wire receiver
coil, and as such may have thickness of several tenths of
millimeter and be of minimal thickness and weight. However
incorporation of this core to the receiver coil may affect the
receiver coil inductance, and considerably affect the efficiency
and power handling capability of the system.
[0095] FIG. 7 shows the incorporation of a magnetic core to the
central area of a Flux Guide system, in accordance with an
embodiment. In accordance with other embodiments, the magnetic core
can be added to the MR, MC, and MA receiver systems described
earlier to similarly enhance their performance.
[0096] In accordance with an embodiment, described herein are
systems and methods for enabling charging or powering multiple
receivers as shown on the right in FIG. 5, where the communication
between receivers and a single charger circuit occurs in a protocol
and method similar to the single charger described above.
[0097] Examples of such a system include where a single charger
coil is used to deliver power to multiple receivers in all or part
of a charger. For example, a system such as a loosely coupled or
magnetic resonant, Magnetic Aperture (MA) or Magnetic Coupling
(MC), Flux guiding (FG), or any combination of the above can be
designed such that a single charger coil and/or circuit powers all
or a part of the charger and designed to power multiple receivers.
In general, such a system can be considered a broadcast system, as
shown 180 in FIG. 8 on the left, where one charger sends power to
one or several similar receivers and includes appropriate
communication and control mechanism to provide the appropriate
power to all the receivers and be able to respond to end of charge
or metal detection, over-temperature or any other fault commands
from any receivers. In a variation, shown on the right of FIG. 8,
the receivers may require different power levels, voltages and/or
use different protocols.
Physical Communication & Control Layer (PCCL)/Command &
Control Layer (CCL):
[0098] To provide Communication and Control between the charger and
receiver or receivers, in accordance with an embodiment, a hardware
Physical Communication and Control Layer (Layer 1b: PCCL) and a
software/firmware Command and Control Layer (Layer 2:CCL) can be
implemented. Optional methods of communication between the charger
and receiver(s) can be provided through the same coils as used for
transfer of power, through a separate coil, through an RF or
optical link, through RFID, Bluetooth, Wi-Fi, Wireless USB, NFC,
Felica, Zigbee, Wireless Gigabit (WiGig), 3G, 4G, etc. or through
such protocols as defined by the Wireless Power Consortium (WPC) or
Alliance for Wireless Power (A4WP) or other protocols such as
Dedicated Short Range Communication (DSRC) used for automotive
applications or other standards, developed for wireless power, or
other communication protocol, or combination thereof.
[0099] In simpler architectures, there may be minimal or no
communication between the charger and receiver. For example, a
charger can be designed to be in a standby power transmitting
state, and any receiver in close proximity to it can receive power
from the charger. The voltage, power, or current requirements of
the device or battery connected to the receiver circuit can be
unregulated, or regulated or controlled completely at the receiver
or by the device attached to it. In this instance, no regulation or
communication between the charger and receiver may be necessary. In
a variation of this, the charger may be designed to be in a state
where a receiver in close proximity would bring it into a state of
power transmission. Examples of this would be a resonant system
where inductive and/or capacitive components are used, so that when
a receiver of appropriate design is in proximity to a charger,
power is transmitted from the charger to a receiver; but without
the presence of a receiver, minimal or no power is transmitted from
the charger.
[0100] In the case that communication is provided through the power
transfer coils, one method for communication from receiver or
receivers to the charger is to modulate a load or impedance in the
receiver to affect the voltage and/or current in the receiver coils
and therefore create a modulation in the charger coil voltage or
current parameters that can be detected through monitoring of its
voltage or current. Other methods can include frequency modulation
by combining the received frequency with a local oscillator signal
or inductive, capacitive, or resistive modulation of the output of
the receiver coil. In addition to communication from receivers to a
charger/transmitter, it is also possible to modulate the charger
voltage at a pre-determined frequency and communication protocol
and detect at each receiver to provide communication from the
charger to the receivers. Such bi-directional communication may be
advantageous in cases where the charger is used to power multiple
receivers as will be explained later.
[0101] In accordance with an embodiment, the communicated
information from a receiver to the charger/transmitter can be the
output voltage, current, power, device or battery status,
validation ID for receiver, end of charge or various charge status
information, receiver battery, device, or coil temperature, and/or
user data such as music, email, voice, photos or video, or other
form of digital or analog data used in a device. It can also be
patterns or signals or changes in the circuit conditions that are
transmitted or occur to simply notify the presence of the receiver
nearby.
[0102] In accordance with an embodiment, the data communicated can
be any one or more of the information detailed herein, or the
difference between these values and the desired value or simple
commands to increase or decrease power or simply one or more
signals that would confirm presence of a receiver or a combination
of the above. The receiver and/or charger and/or their coils can
also include elements such as thermistors, magnetic shields or
magnetic cores, magnetic sensors, and input voltage filters, etc.
for safety and/or emission compliance reasons. The receiver may
also be combined with other communication or storage functions such
as NFC, Wi-Fi, Bluetooth, etc. In addition, the charger and or
receiver can include means to provide more precise alignment
between the charger and receiver coils or antennas. These can
include visual, physical, or magnetic means to assist the user in
alignment of parts. To implement more positioning freedom of the
receiver on the charger, the size of the coils can also be
mismatched. For example, the charger can comprise a larger coil
size and the receiver a smaller one or vice versa, so that the
coils do not have to be precisely aligned for power transfer.
[0103] In accordance with an embodiment, to minimize stand-by power
use, the charger can periodically be turned on to be driven with a
periodic pattern (a ping process) and if a receiver in proximity
begins to draw power from it, the charger can detect power being
drawn from it and would stay in a transmitting state. If no power
is drawn during the ping process, the charger can be turned off or
placed in a stand-by or hibernation mode to conserve power and
turned on and off again periodically to continue seeking a
receiver.
[0104] In accordance with an embodiment, the charger also includes
a circuit that measures the current through and/or voltage across
the charger coil (in this case a current sensor is shown in FIGS. 3
& 9 by way of example). Various demodulation methods for
detection of the communication signal on the charger current or
voltage are available. This demodulation mechanism can be, for
example, an AM or FM receiver (depending on whether amplitude or
frequency modulation is employed in the receiver modulator) similar
to a radio receiver tuned to the frequency of the communication or
a heterodyne detector, etc.
[0105] While a system for communication between the charger and
receiver through the power transfer coils or antennas is described
above, in accordance with an embodiment the communication can also
be implemented through separate coil or coils, a radio frequency
link (am or fm or other communication method), an optical
communication system or a combination of the above. The
communication in any of these methods can also be bi-directional
rather than uni-directional as described above.
[0106] As an example, FIG. 9 shows a system 190 in accordance with
an embodiment, wherein a dedicated RF channel for uni-directional
or bi-directional communication between the charger and receiver is
implemented for validation and/or regulation purposes. This system
is similar to the system shown in FIG. 3, except rather than load
modulation being the method of communication, the Microcontroller
(MCU) in the receiver transmits the required information over an RF
communication path. A similar system with LED or laser transceivers
or detectors and light sources can be implemented. Advantages of
such a system include that the power received is not modulated and
therefore not wasted during communication and/or that no noise due
to the modulation is added to the system.
[0107] In accordance with an embodiment, the microcontroller unit
(MCU) in the charger (MCU1) is responsible for recognizing and
understanding the communication signal from the
detection/demodulation circuit and, depending on the algorithm
used, making appropriate adjustments to the charger coil drive
circuitry to achieve the desired output voltage, current or power
from the receiver output. In addition, MCU1 is responsible for
processes such as periodic start of the charger to seek a receiver
at the start of charge, keeping the charger on when a receiver is
found and accepted as a valid receiver, continuing to apply power
and making appropriate adjustments, and/or monitoring temperature
or other environmental factors, providing audio or visual
indications to the user on the status of charging or power process,
etc. or terminating charging or application of power due to end of
charge or customer preference or over temperature, over current,
over voltage, or some other fault condition or to launch or start
another program or process.
[0108] In accordance with an embodiment, once the charger MCU1 has
received a signal and decoded it, it can take action to provide
more or less power to the charger coil. This can be accomplished
through known methods of adjusting the frequency, duty cycle or
input voltage to the charger coil or a combination of these
approaches. Depending on the system and the circuit used, the MCU1
can directly adjust the bridge driver, or an additional circuit
such as a frequency oscillator may be used to drive the bridge
driver or the FETs.
[0109] A typical circuit for the receiver, in accordance with a
load modulation communication system embodiment, is shown in FIG.
3.
[0110] In accordance with an embodiment, the receiver circuit can
include an optional capacitor C2 in parallel or series with the
receiver coil to produce a tuned receiver circuit. This circuit is
known to increase the efficiency of a wireless power system. The
rectified and smoothed (through rectifiers and capacitors) output
of the receiver coil and optional capacitor is either directly or
through a switch or regulator applied to the output. A
microcontroller MC2 is used to measure various values such as
voltage V.sub.1, current, temperature, state of charge, battery
full status, end of charge, etc. and to report back to the charger
to provide a closed loop system with the charger as described
above. In the circuit shown in FIG. 3, the receiver MCU2
communicates back to the charger by modulating the receiver load by
rapidly closing and opening a switch in series with a modulation
load or impedance at a pre-determined speed and coding pattern.
This rapid load modulation technique at a frequency distinct from
the power transfer frequency can be easily detected by the charger.
A capacitor and/or inductor can also be used as the modulation
load.
[0111] As an example, if one assumes that the maximum current
output of the receiver is 1000 mA and the output voltage is 5 V for
a maximum output of 5 W; in this case, the minimum load resistance
is 5 ohms. A modulation load resistor of several ohms (20, or 10
ohms or smaller) would be able to provide a large modulation depth
signal on the receiver coil voltage. Such a large modulation can be
easily detected at the charger coil current or voltage as described
above. Other methods of communication through varying the reactive
component of the impedance can also be used. The modulation scheme
shown in FIG. 3 is shown only as a representative method and is not
meant to be exhaustive. As an example, the modulation can be
achieved capacitively, by replacing the resistor with a capacitor.
In this instance, the modulation by the switch in the receiver
provides the advantage that by choosing the modulation frequency
appropriately, it is possible to achieve modulation and signal
communication with the charger coil and circuitry, with minimal
power loss (compared to the resistive load modulation).
[0112] The receiver in FIG. 3 also shows an optional DC regulator
that is used to provide constant stable voltage to the receiver
MCU2. This voltage supply may be necessary to avoid drop out of the
receiver MCU2 during startup conditions where the power is varying
largely or during changes in output current and also to enable the
MCU2 to have a stable voltage reference source so it can measure
the V.sub.1 voltage accurately. Alternatively, a switch to connect
or disconnect the load can be used or combined with the regulator.
To avoid voltage overshoots during placement of a receiver on a
charger or rapid changes in load condition, a voltage limiter
circuit or elements like Transit Voltage Suppressor (TVS), Zener
diodes or regulators or other voltage limiters can also be included
in the receiver.
[0113] In the above description, a uni-directional communication
(from the receiver to the charger) is described. However, this
communication can also be bi-directional, and data can be
transferred from the charger to the receiver through modulation of
the voltage or current in the charger coil and read back by the
microcontroller in the receiver detecting a change in the voltage
or current, etc.
[0114] In accordance with an embodiment, the communication between
the receiver and charger needs to follow a pre-determined protocol,
baud rate, modulation depth, etc. and a pre-determined method for
hand-shake, establishment of communication, and signaling, etc. as
well as optionally methods for providing closed loop control and
regulation of power, voltage, etc. in the receiver.
[0115] In accordance with an embodiment, a typical wireless power
system operation 200 as further shown in FIG. 10 can be as follows:
the charger periodically activates the charger coil driver and
powers the charger coil with a drive signal of appropriate
frequency. During this `ping` process, if a receiver coil is placed
on or close to the charger coil, power is received through the
receiver coil and the receiver circuit is energized. The receiver
microcontroller is activated by the received power and begins to
perform an initiation process whereby the receiver ID, its
presence, power or voltage requirements, receiver or battery
temperature or state of charge, manufacturer or serial number
and/or other information is sent back to the charger. If this
information is verified and found to be valid, then the charger
proceeds to provide continuous power to the receiver. The receiver
can alternately send an end of charge, over-temperature, battery
full, or other messages that will be handled appropriately by the
charger and actions performed. The length of the ping process
should be configured to be of sufficient length for the receiver to
power up its microcontroller and to respond back and for the
response to be received and understood and acted upon. The length
of time between the pings can be determined by the implementation
designer. If the ping process is performed often, the stand-by
power use of the charger is higher. Alternately, if the ping is
performed infrequently, the system will have a delay before the
charger discovers a receiver nearby; so in practice, a balance
should be strived for.
[0116] Alternately, the ping operation can be initiated upon
discovery of a nearby receiver by other means. This provides a very
low stand-by power use by the charger and may be performed by
including a magnet in the receiver and a magnet sensor in the
charger or through optical, capacitive, weight, NFC or Bluetooth,
RFID or other RF communication or other methods for detection.
[0117] Alternatively, the system can be designed or implemented to
be always ON (i.e. the charger coil is powered at an appropriate
drive frequency) or pinged periodically and presence of the
receiver coil brings the coil to resonance with the receiver coil
and power transfer occurs. The receiver in this case may not even
contain a microcontroller and act autonomously and may simply have
a regulator in the receiver to provide regulated output power to a
device, its skin, case, or battery. In those embodiments in which
periodic pinging is performed, the presence of a receiver can be
detected by measuring a higher degree of current flow or power
transfer or other means and the charger can simply be kept on to
continue transfer of power until either the power drawn falls below
a certain level or an end of charge and/or no device present is
detected.
[0118] In another embodiment, the charger may be in an OFF or
standby, or low or no power condition, until a receiver is detected
by means of its presence through a magnetic, RF, optical,
capacitive or other methods. For example, in accordance with an
embodiment the receiver can contain an RFID chip and once it is
present on or nearby the charger, the charger would turn on or
begin pinging to detect a receiver.
[0119] In accordance with an embodiment, the protocol used for
communication can be any of, e.g., common RZ, NRZ, Manchester code,
etc. used for communication. An example of the communication
process and regulation of power and/or other functions is shown in
FIG. 10. As described above, the charger can periodically start and
apply a ping voltage of pre-determined frequency and length to the
charger coil (as shown in the lower illustration in FIG. 10). The
receiver is then activated, and may begin to send back
communication signals as shown in top of FIG. 10. The communication
signal can include an optional preamble that is used to synchronize
the detection circuit in the charger and prepare it for detection
of communication. A communication containing a data packet may then
follow, optionally followed by checksum and parity bits, etc.
Similar processes are used in communication systems and similar
techniques can be followed. In accordance with an embodiment, the
actual data packet can include information such as an ID code for
the receiver, a manufacturer's code, received voltage, power, or
current values, status of the battery, amount of power in the
battery, battery or circuit temperature, end of charge or battery
full signals, presence of external wired charger, or a number of
the above. Also this packet may include the actual voltage, power,
current, etc. value or the difference between the actual value and
the desired value or some encoded value that will be useful for the
charger to determine how best to regulate the output.
[0120] Alternatively, the communication signal can be a
pre-determined pattern that is repetitive and simply lets the
charger know that a receiver is present and/or that the receiver is
a valid device within the power range of the charger, etc. Any
combination of systems can be designed to provide the required
performance.
[0121] In accordance with an embodiment, in response to the
receiver providing information regarding output power or voltage,
etc. the charger can modify voltage, frequency, duty cycle of the
charger coil signal or a combination of the above. The charger can
also use other techniques to modify the power out of the charger
coil and to adjust the received power. Alternatively the charger
can simply continue to provide power to the receiver if an approved
receiver is detected and continues to be present. The charger may
also monitor the current into the charger coil and/or its
temperature to ensure that no extra-ordinary fault conditions
exist. One example of this type of fault may be if instead of a
receiver, a metal object is placed on the charger.
[0122] In accordance with an embodiment, the charger can adjust one
or more parameters to increase or decrease the power or voltage in
the receiver, and then wait for the receiver to provide further
information before changing a parameter again, or it can use more
sophisticated Proportional Integral Derivative (PID) or other
control mechanism for closing the loop with the receiver and
achieving output power control. Alternatively, as described above,
the charger can provide a constant output power, and the receiver
can regulate the power through a regulator or a charger IC or a
combination of these to provide the required power to a device or
battery.
[0123] Various manufacturers may use different encodings, and also
bit rates and protocols. The control process used by different
manufacturers or protocols may also differ, further causing
interoperability problems between various chargers and receivers. A
source of interoperability differences may be the size, shape, and
number of turns used for the power transfer coils. Furthermore,
depending on the input voltage used, the design of a wireless power
system may step up or down the voltage in the receiver depending on
the voltage required by a device by having appropriate number of
turns in the charger and receiver coils. However, a receiver from
one manufacturer may then not be able to operate on another
manufacturer charger due to these differences in designs
employed.
[0124] In accordance with an embodiment, it is therefore beneficial
to provide a system that can operate with different receivers or
chargers and can be universal. Recently, there has been some
movement to standardize the frequency of operation, the coil and
electronics characteristics, the identification and communication
method, messaging and protocol and other aspects of the systems to
allow interoperability between systems from different
manufacturers. Several interoperability Standards and
Specifications in this area have been established or under
consideration. These include the WPC interoperability
specification, the Consumer Electronics Association Standard for
wireless power, the Alliance for Wireless Power (A4WP), the
Consumer Electronics Association (CEA) Wireless Power Standards
working group and Wireless Power Standards for Electric Vehicle
charging, and other international efforts for Specification and
Standards development.
[0125] The resonant frequency, F of any LC circuit is given by:
F=1/2.pi. LC
[0126] Where L is the Inductance of the circuit or coil in Henry
and C is the Capacitance in Farads.
[0127] For example, in the system shown in FIG. 3, one may use the
values of C1 and L1 in the above calculation for a free running
charger and as a Receiver is brought close to this circuit, this
value is changed by the mutual coupling of the coils involved. In
the case a ferrite shield layer is used behind a coil in the
charger and/or receiver, the inductance of the coil is affected by
the permeability of the shield and this modified permeability
should be used in the above calculation.
[0128] In accordance with an embodiment, to be able to detect and
power/charge various receivers, the charger can be designed such
that the initial ping signal is at such a frequency range to
initially be able to power and activate the receiver circuitry in
any receiver during the ping process. After this initial power up
of the receiver, the charger communication circuit should be able
to detect and decode the communication signal from the receiver.
Many microcontrollers are able to communicate in multiple formats
and/or may have different input A/D converter pins that can be
configured differently to simultaneously receive the communication
signal and synchronize and understand the communication at
different baud rates and protocols. In accordance with an
embodiment, the charger firmware can then decide on which type of
receiver is present and proceed to regulate or implement what is
required (end of charge, shut-off, fault condition, etc.).
Depending on the message received, the charger can then decide to
change the charger driver voltage amplitude, frequency, or duty
cycle, or a combination of these or other parameters to provide the
appropriate regulated output at the receiver output.
[0129] In accordance with an embodiment, the charger's behavior can
also take into account the difference in the coil geometry, turns
ratio, etc. For example, a charger and receiver pair from one or
more manufacturers may require operation of the charger drive
voltage at 150 kHz. However, if the same receiver is placed on a
charger from another manufacturer or driven with different
coil/input voltage combination, to achieve the same output power,
the charger frequency may need to be 200 kHz. The charger program
may detect the type of receiver placed on it and shift the
frequency appropriately to achieve a baseline output power and
continue regulating from there. In accordance with an embodiment,
the charger can be implemented so that it is able to decode and
implement multiple communication and regulation protocols and
respond to them appropriately. This enables the charger to be
provided as part of a multi-protocol system, and to operate with
different types of receivers, technologies and manufacturers.
[0130] In accordance with another embodiment, similar techniques
can be used to allow a receiver to be chargeable on chargers
utilizing different protocols for communication and control. For
example, the receiver may recognize the type of charger being used
by deciphering the frequency of the charger operation or its ping
(through frequency filtering or other techniques) and communicate
using different protocols and communication signals
accordingly.
[0131] For receivers that contain an onboard output stage regulator
before the output power, stability of the input voltage to the
regulator is not as critical since the regulator performs a
smoothing function and keeps the output voltage at the desired
level with any output load changes (such as during battery
charging). The output of the regulator is then directed to
circuitry such as power management IC (PMIC) or to a battery for
charging or directly connected to the device for use (in cases
where the receiver acts as a power supply to a device without
internal batteries) or a combination of the above. Where an output
regulator stage is used in a receiver it is critical for the
wireless receiver not to exceed the maximum rated input voltage of
the output stage regulator or to drop below a level required so
that the output voltage from the regulator could no longer be
maintained at the required value. Various types of output stage
regulator such as buck, boost, buck-boost, linear etc. can be used
as this output stage. However, in general, inclusion of a regulator
and/or a charger IC or PMIC chip (for batteries) relaxes the
power/voltage regulation requirements of the wireless power
receiver portion of the circuit at the expense of the additional
size and cost of this component. In accordance with some
embodiments, simpler voltage limiting output stages such as Zener
diodes, TVS or other voltage limiting or clamping ICs or circuits,
can be used.
[0132] In accordance with another embodiment, the receiver can also
include variable or switchable reactive components (capacitors
and/or inductors) that allow the receiver to change its resonant
condition to affect the amount of power delivered to the device,
load or battery. The receiver and/or charger and/or their coils can
also include elements such as thermistors, magnetic shields or
magnetic cores, magnetic sensors, and input voltage filters, for
safety and/or emission compliance reasons.
[0133] In accordance with an embodiment, the systems described here
may use discrete electronics components or some or all of the
functions described above may be integrated into an Application
Specific Integrated Circuit (ASIC) or MCMs to achieve smaller
footprint, better performance/noise, etc. and/or cost advantages.
Such integration is common in the Electronics industry and can
provide additional advantages here.
[0134] While the system above describes a system wherein the
communication is primarily through the coil, as described earlier,
communication can also be implemented through a separate coil, RF,
optical system or a combination of the above. In such
circumstances, a multi-protocol system can also be used to
interoperate between systems with different communication and/or
control protocols or even means of communication.
Methods for Charging Multiple Receivers from One Charger
[0135] FIG. 10 and FIG. 11 provide more detailed views of the
interaction of a single charger and receiver. The charger applies
power to the receiver by generating an AC voltage across the
charger coil. A receiver that is powered by this
transmitter/charger coil will respond by periodically sending data
packets to the charger by load modulation techniques described
earlier. The data packets may have various forms and lengths. The
packet length may be within some minimum (t.sub.packet(min)) and
maximum values (t.sub.packet(max))
t.sub.packet(min)<t.sub.packet<t.sub.packet(max)
[0136] This data packet is repeated periodically with interval
t.sub.interval which similarly may have a minimum and maximum
allowable range of values:
t.sub.interval(min)<t.sub.interval<t.sub.interval(max)
[0137] In response to this communication, as described earlier, the
charger will change one or more parameter of operation to change
the received power (or voltage V.sub.1) and to bring it in within a
range V.sub.range of the set voltage V.sub.set:
V.sub.set-V.sub.range<V.sub.1<V.sub.set+V.sub.range
[0138] Some of the parameters to change to achieve the desired
voltage include the charger operating frequency, the amplitude of
the voltage applied to the charger circuit, and the duty cycle of
the signals applied to the switching circuitry (Pulse Width
Modulation: PWM).
[0139] As shown in FIG. 10, for example, the frequency of operation
of operation may be modified to bring the receiver voltage or power
closer to the desired or set value desired by the receiver circuit,
the device connected to the receiver or the battery being charged
or the system being powered.
[0140] FIG. 11 is a simplified representation 210 of the
communication process between the charger and the receiver, in
accordance with an embodiment. When a receiver is powered by a
charger, it proceeds to send data packets of t.sub.packet length
every t.sub.interval period. In general, such a system is designed
for a single receiver to act as a master to provide commands to the
charger to optimize power transfer to the receiver according to its
needs and requirements that change over time. The output voltage
V.sub.1 is either the direct output to the load or in case an
output voltage regulator stage is implemented the input voltage to
this regulator stage (see FIGS. 3 and 9). FIG. 11 shows the
variation of V.sub.1 over time and its control over a range of
V.sub.range around V.sub.set in accordance with an embodiment.
[0141] In accordance with some embodiments, such as shown 220 in
FIG. 12, where a single coil is used in the charger to power or
charge multiple receivers (shown as phones in this figure, by way
of example), it may be necessary to establish a method whereby
simultaneous control and transfer of power to multiple receivers
can be achieved.
[0142] In some instances it would be beneficial to implement
systems such as shown in FIGS. 8 and 12 to provide power to
multiple receivers from one charger circuit and/or coil. Advantages
of such systems include lower cost and complexity. As discussed
previously, use of larger size charger coils and smaller receiver
coils, highly resonant, Magnetic Resonance (MR), Magnetic Aperture
(MA), Magnetic Aperture (MA) or Magnetic Coupling (MC), flux
guiding or a combination of the above techniques can provide PPL
architectures for transfer of power from one or several charger
coils to one or several receiver coils. In the Physical
Communication & Control Layer (PCCL), as described above, in
band, load modulation or out of band communication through separate
RF channel or optical or other methods of communication can be
used. The receiver may communicate with the wireless charger or
power supply system through the same coil the power is transferred,
through a different coil, through a wireless communication protocol
at a different frequency, established protocols such as Wi-Fi,
Bluetooth, Zigbee, Wireless USB, etc. or a custom protocol such as
WPC, A4WP, DSRC, etc. and the communication can be uni-directional
(from receivers to the charger) or bi-directional.
[0143] Several issues that have to be considered in communication
and control of charging to several receivers from one charger are
as follows: [0144] A PCCL and CCL system and communication protocol
should be established to avoid message collision when multiple
receivers are communicating with one charger. [0145] For a
charger/power supply comprising a coil that is powering multiple
receivers, individual adjustment of power to different receivers by
the charger is not possible. Therefore, with variation of a
receiver load or during a charging cycle, received power at each
individual receiver may not be adjustable. or. To provide regulated
output from the receivers to multiple loads, regulation at the
receivers is often necessary. [0146] Pinging, detection of multiple
receivers, fault condition, over-temperature, foreign object
detection (FOD) for metal, etc. can be handled for multiple
receivers.
[0147] In accordance with an embodiment, described herein are
several embodiments of implementing a PCCL and CCL where multiple
receivers communicate with a charger/power supply using load (or
impedance) modulation at the receiver. The basic operating
principles of load modulation and its Physical Communication and
Control Layer (PCCL) implementations for wireless power transfer
(WPT) systems were described previously. Also described herein, in
accordance with various embodiments, are several methods to use the
PCCL described previously, or enhance it and to use more advanced
Command and Control Layer (CCL) software or firmware to achieve
communication and control between multiple receivers and one or
more charger circuits.
[0148] In accordance with an embodiment, described here and shown
230 in FIG. 13, each receiver that receives power from the charger
begins sending out data packets (of length
t.sub.packet(min)<t.sub.packet<t.sub.packet(max)) at random
communication intervals
(t.sub.interval(min)<t.sub.interval<t.sub.interval(max):
t.sub.packet(max)<t.sub.interval<t.sub.interval(max)
[0149] In accordance with an embodiment, the charger detection
circuit receives the communication packets from the receivers and
decodes them as they arrive. However, as shown 240 in FIG. 14,
there is a chance for two or more receiver packets to arrive at
similar times and overlap resulting in a corrupt message as a
result of such collision. The charger CCL is designed to ignore
such corrupted messages and await further messages. In accordance
with an embodiment, the receivers are designed to include a
regulator stage at their outputs as shown in FIGS. 1, 3, and 9.
These regulators and/or switches would have an input voltage
operating range:
Vreg.sub.min<V.sub.1<Vreg.sub.max
[0150] Various types of output stage regulators such as buck,
boost, buck-boost, linear, hysteretic, etc. can be used as this
output stage. However, in general, inclusion of a regulator and/or
a charger IC or PMIC chip (for batteries) relaxes the power/voltage
regulation requirements of the wireless power receiver portion of
the circuit (i.e. regulation of the voltage V.sub.1 in FIGS. 3
& 9) at the potential expense of the additional size and cost
of this output regulation component.
[0151] In accordance with some embodiments, simpler voltage
limiting output stages such as Zener diodes, TVS or other voltage
limiting or clamping ICs or circuits can be used. In general, to
provide a wider voltage range of operation at higher efficiency, a
buck regulator output stage can be used. For example for a system
with a regulated 5 V output voltage, the input voltage operating
range for commonly available buck Integrated Circuits (ICs) may be
6 V<V.sub.1<20 V or more. Output to input power efficiencies
of in excess of 90% can be obtained from available ICs.
[0152] Unlike the single charger/receiver shown in FIG. 11, in
accordance with some embodiments the goal of the CCL system for a
multi receiver system is not to keep the voltage level V.sub.1 of
the receivers within a tight limit of a set voltage. As shown in
FIG. 13, in accordance with an embodiment, the charger Physical
Communication and Control Layer (PCCL) system will detect and
decode the received data packets and will attempt to keep all the
receivers output voltages V.sub.1 within their allowed operating
range. This can be achieved by ensuring that the highest and lowest
V.sub.1 values reported by all receivers are within the allowable
range. The charger can modify the input voltage to the charger
coil, the operating frequency and/or the duty cycle (pulse width
modulation, PWM) of the drive signal to the charger circuit to
change the overall output power to the multiple receivers. The
regulation stages at the output of each receiver will then convert
this V.sub.1 voltage to the required output voltage to the load
efficiently and provide the secondary regulation necessary to
achieve a constant (or variable in case of direct battery charging
or programmed voltage variation) output voltage due to changing
loads or receiver position conditions.
[0153] In accordance with an embodiment, such as shown in the right
side of FIG. 8, each receiver may be operating to provide a
different output power level or voltage. It may be therefore
beneficial for each receiver to report its associated voltage
V.sub.1 as a relative value of its total range. For example rather
than reporting the voltage value V.sub.1, the receiver may report
this normalized V.sub.report as a percentage over and under the
Vreg.sub.min such that:
V report = ( V 1 - V reg min ) ( V reg max - V reg min ) * 100
##EQU00001##
[0154] In this way, the charger can receive an overview of status
of each receiver normalized to its operating conditions and/or
hardware requirements. The charger can then attempt to keep all of
the reported normalized voltages within 0 to 100%.
[0155] In a further embodiment, if all of the receivers can operate
within this range, the charger can then attempt to lower the
overall transmitted power so that the lowest value of V.sub.report
is close to 0 without any of the values of V.sub.report falling
under zero. The reason for this is that the highest output
regulator efficiencies are achieved with the regulator operating at
the lowest input (V.sub.1) operating voltage. So lowering the
V.sub.report values to the extent possible without disrupting
operation of any receivers provides an overall optimum efficiency
operating condition.
[0156] In accordance with another embodiment, during ping, startup
of the charger or periodically during the operation, each receiver
reports its output power, voltage requirements, manufacturer and/or
a unique or receiver type ID that can be converted by a look up
table in the charger to recognize the receiver type and its
Hardware and or Software requirements for the charger. Once the
charger knows the types and numbers of the receivers present, any
additional data packet would include a header that would identify
to the charger which receiver is communicating at each instance and
the charger would make appropriate adjustments to the overall power
or take other actions depending on this data packet and knowledge
of the requirements of the associated receiver.
[0157] In accordance with another embodiment, as shown in FIG. 14,
a fixed t le will t.sub.packet be used by each receiver and each
receiver will send its communication packet at a random delay from
the last packet transmission that is a multiple N of the
t.sub.packet. In this way, there will be some more order to how
often the packets arrive. However, this system will not alleviate
the issue of packet collision from different receivers. Furthermore
since each receiver may start communicating at a different time
depending on when a receiver is placed on or near a charger, the
packets can still arrive at any time with respect to each
other.
[0158] In a further embodiment, as shown 250 in FIG. 15, the
charger may periodically send a sync, beacon, or query pattern that
would be recognized by each receiver and used to sync their data
transmission. This sync signal may also include a maximum receiver
number N.sub.max. and/or a value for a timeslot to be used. Once
the sync signal has been sent, each receiver will randomly choose a
number N between 1 and N.sub.max and begin transmission at a time
window of N*timeslot and every N.sub.max*timeslot thereafter.
Alternatively the value N and timeslot may be hard coded into the
charger and/or receiver systems.
[0159] In accordance with an embodiment, if as shown 260 in FIG.
16, a collision occurs because two or more receivers choose the
same number N, then the charger would receive a corrupted
communication and would resend a sync signal to reset all receiver
communication and for the receivers to pick new timeslots randomly.
Additionally, to keep packet timings to keep from drifting, the
charger may send periodic sync signals to the receivers whereby
they adjust their timing or choose new N values. In another
embodiment, the charger signal to the receivers may comprise more
complex messages instructing them to reset the N values or to
continue with the same N values but synchronize their timing or
other commands.
[0160] Any time a new receiver is introduced to the system, it
would begin drawing power and this may bring one or more receiver
V.sub.1 voltages rapidly below the allowed value. This may be seen
as an indication to the charger of presence of a new receiver and
trigger a sync signal transmission to sync all active receivers. In
the above discussion several methods of powering multiple receivers
from the same charger have been described but a complete wireless
power transfer system should include hardware and software
provisions to handle: standby and initial set up/ping or
identification of receivers; changes to number of receivers due to
introduction or removal of a receiver during operation; handling of
changes to power requirement of one or more receivers due to
movement of the receiver in X, Y, or Z direction or change in their
load; end of charge at one or more receivers; foreign object
(metal) detection; over temperature and/or other fault handling in
the system.
[0161] Several of the above conditions are described in further
detail below.
Standby and Initial Set Up/Ping or Identification of Receivers
[0162] In accordance with an embodiment, the charger periodically
applies a continuous ac power to the charger coil for a period of
t.sub.ping to seek nearby receivers. In response to this ping the
nearby receivers are powered up and begin sending initialization,
power apply or other messages (end of charge, fault condition,
etc.). Each receiver may report its output power limit, voltage
requirements, manufacturer and/or a unique or receiver type ID that
can be converted by a look up table in the charger to recognize the
receiver type and its Hardware and or Software requirements for the
charger. Once the charger knows the types and numbers of the
receivers present, any additional data packet would include a
header that would identify to the charger which charger is
communicating at each instance and the charger would make
appropriate adjustments to the overall power or take other actions
depending on this data packet and knowledge of the requirements of
the associated receiver. In addition the transmitted packet would
include the generated receiver power or voltage V.sub.1 at that
instance.
[0163] FIG. 17 shows a situation in accordance with an embodiment
270, where three receivers respond to a ping and begin
communication transmission. As shown here, it may be possible for
three or more packets from different receivers to have a collision
and corrupt the message received by the charger. Methods for
handling collisions and to sync the transmitted messages have been
described above. During the ping process the beginning of ping or a
sync charger signal during ping can be used to sync the
communication from the receivers present. The charger program will
gather all the responses from the receivers present and determine
based on the info received to progress to continuous power
application or to terminate and go back to standby or ping status.
Any error or fault message would terminate power application and
return to standby or ping. In case of receipt of corrupted messages
due to collision, the charger may terminate the ping process and
reset to stand by and another ping to allow receivers to send
packets again or it can proceed to send another sync signal to
force the receivers to reset their message timing and send messages
again or it can proceed to continuous power application based on
the limited available good messages it has received and wait for
further packets to determine whether to increase or decrease
applied power or terminate or take other action.
[0164] In accordance with an embodiment, to deal with receivers
that have different power requirements, coil types, and/or are at
different X, Y, and/or Z locations and therefore different required
power levels and/or frequencies to achieve required voltage levels
or use different protocols or operating frequencies to respond to a
ping, the frequency of the applied frequency during the ping can be
varied continuously or discretely to scan and probe all possible
nearby receivers. One method used may be to begin the ping at a
higher frequency and move to lower frequencies in cases where the
system is designed to operate at the higher frequency slope of the
resonance. By moving to lower frequencies as the ping progresses,
the applied power to nearby receivers is increased and any receiver
that requires higher power levels is enabled eventually and would
respond.
[0165] In accordance with an embodiment, to avoid damage to the
output regulator stages of the receivers by exceeding Vreg.sub.max,
a switch S1 may be included before the regulator, as shown 280 in
FIG. 18. The switch is under receiver MCU2 control and is designed
to be normally off to disconnect the rectified receiver power from
the output regulator. Once a receiver is activated by a ping and
communication is established, the voltage V.sub.1 is regulated
through charger side regulation as described earlier. Once this
voltage is regulated to a safe range within the output regulator
minimum and max voltage values, MCU2 can close the switch S1 and
allow the output regulator to regulate the voltage to the desired
output voltage level. In another embodiment or in addition to the
switch discussed above, as shown in FIG. 18, a voltage limiting
component such as a Transit Voltage Suppressor (TVS), Zener diode
or other voltage limiter or clamp for voltage V.sub.1 can also be
added to quickly clamp the voltage to within safe levels.
Changes to Number of Receivers Due to Introduction/Removal During
Operation
[0166] In accordance with an embodiment, during operation of the
system, a user may add or remove one or more receivers operating at
different output power and/or voltage levels. If the charger is in
operation and transferring power to one or more receivers, addition
or removal of additional receivers can result in rapid decrease or
increase of receiver V.sub.1 voltages due to a sudden change in the
total output loading. In most circumstances, with the receivers
notifying the charger about the sudden voltage change, the charger
can adjust the output power level and bring the receiver V.sub.1
values to within the safe range but if these values exceed safe
limits, the receiver microcontroller MCU2 and a switch S1 as shown
in FIG. 18 can limit damage to the output regulator. In another
embodiment or in addition to the switch, as discussed earlier, a
voltage limiting component such as a Transit Voltage Suppressor
(TVS), Zener diode or other voltage limiter or clamp for voltage
V.sub.1 can be used.
Handling Changes to Power Requirements Due to Movements Ors Changes
in Load
[0167] In accordance with an embodiment, the efficiency of the
power transfer to a receiver may be affected by its location on a
charger. During operation, a user may move one or more receivers in
any direction. However, application of the above techniques should
be sufficient to re-adjust the system to efficient operation.
End of Charge at One or More Receivers
[0168] In accordance with an embodiment, in a single
charger/receiver system where the receiver output is used to charge
a battery, at the completion of the charge, the output current
drawn is decreased to a low limit. In this case, the charger may be
instructed to shut off or enter a standby state. In addition, the
user may be informed by a visual, audio or other means of
notification of the end of charge by the charger and/or the
receiver or the device or vehicle, etc, being charged or powered.
In a multiple receiver system, when one or more of the receivers
issue such an end of charge instruction, the charger may still
continue to operate to power the remaining operating receivers
within their required power levels. Since the devices with
completed charging draw low or no power, the receiver voltage
V.sub.1 may increase as the current drawn is decreased. To avoid
damage to the receivers some of the techniques discussed above may
be implemented by integration of Switch S1 and/or voltage limiting
or clamping components in the receiver.
Metal or Foreign Object Detection
[0169] In accordance with an embodiment, it may be useful in
addition to the communication signal to detect the DC value of the
current through the charger coil. For example, faults may be caused
by insertion or presence of foreign objects such as metallic
materials between the charger and receiver. These materials may be
heated by the application of the power and can be detected through
detection of the charger and/or receiver current or temperature or
comparison of charger voltage, current, or power and receiver
output voltage, current, or power and ascertaining whether the
ratio is out of normal range and extra power loss due to unknown
reasons is occurring. In these conditions or other situations such
as abnormal charger and/or receiver heating, the charger and/or
receivers may be programmed to declare a fault condition and shut
down and/or alert the user or take other actions.
Over Temperature and/or Other Fault Handling
[0170] In accordance with an embodiment, in case of fault messages
such as over temp, over or under voltage or power or messages due
to circuit operation faults, etc. from one or more receivers, the
flow of power to that receiver or the device or battery connected
to it or all receivers will need to be interrupted. The PCCL and
CCL implemented can support such contingency handling. For example,
the charger and/or receiver may be configured to take immediate
action by shutting off the charging and/or notifying the user.
Other Methods of Power Communication & Control
[0171] In accordance with another embodiment of regulation, the
receivers may communicate with the charger/transmitter and/or with
other receivers through wireless RF communication, RFID or Near
Field Communication (NFC), Bluetooth, Wi-Fi, or other proprietary
communication through separate antennas or separate coils or
through optical or other methods.
[0172] Several methods of collision avoidance for wireless
communication between many devices have been devised and can be
applied to WPT systems. As an example, the details of the RFID
specification ISO/IEC 14443-3:2011: Identification
cards--Contactless integrated circuit cards--Proximity cards--Part
3: Initialization and anti-collision describes techniques to avoid
collision between many devices and a reader (charger in a WPT
system). Bluetooth Core Specification Ver. 4 and earlier versions
refer to methods for anti-collision that can be applied to WPT PCCL
as well.
[0173] In several of the embodiments described above, the charger
systems are designed to provide power continuously to each receiver
during operation. In accordance with another embodiment of the WPT
multi receiver system described here, each receiver may time-share
the transmitter power. Each receiver placed on or near a charger or
transmitter may synchronize and communicate with it first. The
transmitter may then power each receiver sequentially and deliver
the appropriate power level through adjustment of the transmitter
frequency, pulse width modulation, or adjustment of input voltage,
or a combination of above methods. In order for this system to
operate, it may be necessary for all or some of the receivers to
disconnect from receipt of power during the time period when one
receiver is receiving power. This can be accomplished by
implementing and opening a switch in the path of the receiver coil
circuit or disabling the receiver's output or its associated
optional regulator or alike. In this way, only one receiver coil
(or more depending on design and architecture) is at any given time
magnetically coupled to the transmitter and receives power. After
some period of time, that receiver may be disconnected by opening
its appropriate switch and the next receiver powered, etc. The
disadvantage of this system is that by applying power to multiple
receivers in a round-robin fashion, the charge time for each device
being charged is lengthened depending on the number of devices or
receivers on a charger.
[0174] In accordance with an embodiment, the receivers may be
communicating at any time depending on when they start their
communication initially (i.e. when a receiver is placed on or near
the charger surface). Thus with several receivers communicating
with the charger, there is opportunity for 2 or more receivers
communicating back at the same time or in a manner that their
messages collide. In this case the charger may not detect and/or
decipher the communicated message due to collision and corruption
of the received signal. Thus the charger will not be able to
react.
[0175] In the geometry described here, the charger can only act
globally (transfer power to all receivers present) so that it is
not possible to individually modify and manage the received power.
Thus a method to regulate the power received by the device or
battery to be powered or charged can be provided.
Handling of Multiple Protocols
[0176] In accordance with an embodiment, a receiver or receivers
placed on or near a charger can communicate with the charger in a
variety of communication protocols according to different wireless
charging standards, protocols or different proprietary methods. To
distinguish them and provide for efficient operation, the charger
can be programmed to recognize different messages received, and
operate differently.
[0177] For example, different protocols exist for communication and
control for charging a single receiver placed on a charger. Some
systems may require the charger to control the voltage output from
the receiver coil (that is rectified and sent to an output of the
system or to a regulator) within a tight tolerance, and can not
tolerate a large range. An example of such a protocol or Standard
is the Wireless Power Consortium (WPC) or Chi Standard which is
designed to provide tight receiver coil output voltage tolerances
and also requires charger frequency range of 110 to 205 kHz. In
accordance with an embodiment a charger system may be designed that
recognizes such a receiver and controls the output to within its
target range. However, in other instances receivers may be designed
as described above that can tolerate a larger V.sub.1 range by
using an output receiver regulator stage i to allow multi-receiver
charging.
[0178] In accordance with an embodiment, to address these use
cases, the charger firmware or software can be configured to
recognize the presence of such receivers and operate using a
different algorithm to keep one or several receiver voltage ranges
to within a larger acceptable range, and provide multi-receiver
charging capability. This allows one charger to be interoperable
with two or more protocols and systems.
[0179] In accordance with an embodiment, the charger systems or
protocols can employ different power transfer and/or communication
frequencies, or different communication methods (e.g., in-band
through coil, and out of band through Wi-Fi or Bluetooth or
proprietary systems) to communicate and also transfer power to
receivers utilizing different protocols. The approaches described
herein enables interoperability between such systems.
[0180] In accordance with an embodiment, the charger may use one or
more driving circuits, communication methods or protocols and/or
charger power or communication coils or antennas to simultaneously
power different receiver coils utilizing different protocols,
standards and/or power levels or voltages.
Wirelessly Charged Battery Implementation
[0181] FIG. 19 shows a wirelessly powered battery pack and receiver
290, in accordance with an embodiment. The components of a typical
common battery pack (battery cell and protection circuit, etc.)
used in a battery device used in applications such as mobile phone,
etc. are shown inside the dashed lines. The components outside the
dashed lines are additional components that are included to enable
safe wireless and wired charging of a battery pack. A battery pack
may have four or more external connector points that interface with
a mobile device pins in a battery housing or with an external
typical wired charger.
[0182] In accordance with an embodiment, the battery cell is
connected as shown 300 in FIG. 20 to two of these connectors (shown
in the figure as BATT+ and BATT+) through a protection circuit
comprising a battery protection IC that protects a battery from
over-current and under or over voltage. A typical IC can be Seiko
8241 IC that uses 2 external Field Effect Transistors (FETs) as
shown in FIG. 7 to prevent current going from or to the battery
cell (on the left) from the external battery pack connectors if a
fault condition based on over current, or battery cell over or
under voltage is detected. This provides safety during charging or
discharging of the battery. In addition, a battery pack can include
a PTC conductive polymer passive fuse. These devices can sense and
shut off current by heating a layer inside the PTC if the amount of
current passing exceeds a threshold. The PTC device is reset once
this current falls and the device cools.
[0183] In addition, in accordance with an embodiment, the battery
pack can contain a thermistor, which the mobile device checks
through one other connector on the battery pack to monitor the
health of the pack, and in some embodiments an ID chip or
microcontroller that the mobile device interrogates through another
connector to confirm an original battery manufacturer or other
information about the battery. Other connectors and functions can
be included in a battery pack to provide accurate battery status
and/or charging information to a device being powered by a battery
pack or a charger charging the battery pack.
[0184] In addition to the components described above, in accordance
with an embodiment, the receiver circuit comprises a receiver coil
that can be a wound wire and/or PCB coil as described above,
optional electromagnetic shielding between the coil and the metal
body of the battery, optional alignment assisting parts such as
magnets, etc., a receiver communication circuit (such as the
resistor and FET for load modulation shown in FIGS. 3 and 9), a
wireless power receiver (such as rectifiers and capacitors as
described above), and an optional Battery charger IC that has a
pre-programmed battery charging algorithm. Each type of battery and
chemistry requires a pre-determined optimized profile for charging
of that battery type. During a typical charge cycle for a Lithium
Ion (Li-Ion) battery, it can be charged up to a value of 4.2 V at
full capacity. The battery should be charged according to the
guidelines of the manufacturer. For a battery of capacity C, the
cell can typically be charged at the rate 1 C. In Stage 1, the
maximum available current is applied and the cell voltage increases
until the cell voltage reaches the final value (4.2 V). In that
case, the charger IC switches to Stage 2 where the charger IC
switches to Constant Voltage charging where the cell voltage does
not change but current is drawn from the source to further fill up
the battery. This second Stage may take 1 or more hours and is
necessary to fully charge the battery. Eventually, the battery will
draw little (below a threshold) or no current. At this stage, the
battery is full and the charger may discontinue charging. The
charger IC can periodically seek the condition of the battery and
top it off further if the battery has drained due to stand-by,
etc.
[0185] In accordance with an embodiment, such multiple stages of
battery charging can be implemented in firmware with the wireless
power charger and receiver microcontrollers monitoring the battery
cell voltage, current, etc. and working in tandem and to provide
appropriate voltage, current, etc. for safe charging for any type
of battery.
[0186] In another approach as shown in FIG. 19, a battery charger
IC chip or power management unit (PMU) or Power Management
Integrated Circuit (PMIC) that has specialized battery charging
circuitry and algorithm for a particular type of battery can be
employed. These charger ICs (with or without fuel gauge capability
to accurately measure battery status, etc.) are available for
different battery chemistries and are included in most mobile
devices with mobile batteries such as mobile phones. They can
include such safety features as a temperature sensor, open circuit
shut off, etc. and can provide other circuits or microcontrollers
such useful information as end of charge signal, signaling for
being in constant current or voltage (stage 1 or 2 above, etc.). In
addition, some of these ICs allow the user to program and set the
maximum output current to the battery cell with an external
resistor across 2 pins of the IC.
[0187] In accordance with an embodiment, the wirelessly charged
battery pack, in addition includes a micro-controller that
coordinates and monitors various points and may also include
thermal sensors on the wireless power coil, battery cell and/or
other points in the battery pack. The microcontroller also may
communicate to the charger and can also monitor communication from
the charger (in case of bi-directional communication). Typical
communication through load modulation is described above.
[0188] In accordance with an embodiment, another aspect of a
wirelessly charged battery pack can be an optional
external/internal switch. A battery pack can receive power and be
charged wirelessly or through the connectors of a battery pack. For
example, when such a battery pack is used in a mobile phone, the
user may wish to place the phone on a wireless charger or plug the
device in to a wired charger for charging or charge the device as
well as synchronize or upload and/or download data or other
information. In the second case, it may be important for the
battery pack to recognize current incoming to the battery pack and
to take some sort of action. This action can include, e.g.,
notifying the user, shutting off the wired charger by a switch or
simply shutting down the charger IC and sending a signal back
through the microcontroller and modulating the current back to the
charger that a wired charger is present (in case priority is to be
given to the wired charger) or conversely to provide priority to
the wireless charger and shut off wired charger access to battery
when the wireless charger is charging the battery. In either case,
a protocol for dealing with presence of two chargers simultaneously
should be pre-established and implemented in hardware and
firmware.
[0189] As shown in FIG. 19, the wireless charging of battery occurs
with current flowing into the battery through the battery contacts
from the mobile device. Typically, such current is provided by an
external DC supply to the mobile device (such as an AC/DC adaptor
for a mobile phone) and the actual charging is handled by a charger
IC chip or power management IC inside the mobile device that in
addition to charging the battery, measures the battery's state of
charge, health, verifies battery authenticity, and displays charge
status through LEDs, display, etc. to a user. It may therefore be
advantageous to include a current sense circuit at one of the
battery pack contacts to measure and sense the direction of current
flow into or out of the battery. In situations where the current is
flowing inwards (i.e. the battery is being externally charged
through a wired charging connection, and/or through a mobile
device), the micro-controller can take the actions described above
and shut off wireless charging or conversely, provide priority to
wireless charging and if it is present, allow or disallow wired
charging as the implementation requires.
[0190] In many applications, it is important to include a feature
that can inform a mobile device user about the state of charge of a
battery pack in the device. To enable an accurate measurement of
the remaining battery charge, several gas gauging techniques can be
implemented, in general by incorporating a remaining charge IC or
circuitry in the battery or in the device. In accordance with an
embodiment, the mobile device can also include a Power PMU or PMIC
or a fuel or battery gauge that communicates with the wirelessly
chargeable battery and measures its degree of charge and display
this status on the mobile device display or inform the user in
other ways. In another embodiment, this information is transmitted
to the charger and also displayed on the charger. In typical
circumstances, a typical fuel gauge or PMU or PMIC may use battery
voltage/impedance, etc. as well as measurement of the current and
time for the current entering the mobile device (Coulomb counting)
to determine the status of the battery charge. However in a
wirelessly charged system, this Coulomb counting may have to be
carried out in the battery rather than in the mobile device, and
then communicated to the mobile device or the charger, since the
charge is entering the battery directly through the onboard
wireless power receiver and circuitry. The communication between
the mobile device and the battery is through the connectors of the
battery and may involve communication with an on-board
microcontroller in the battery pack. In accordance with an
embodiment, the wirelessly chargeable battery pack can include
appropriate microcontroller and/or circuitry to communicate with
the mobile device or wireless charger circuitry and update its
state of charge, even though no current may be externally applied
(through a wired power supply or charger) to the mobile device and
the battery is charged wirelessly. In simpler fuel gauge
techniques, the battery voltage, impedance, etc. can be used to
determine battery charge status, and that in turn can be
accomplished by performing appropriate measurements by the mobile
device circuitry through battery connector points or by appropriate
circuitry that may be incorporated in the wirelessly chargeable
battery pack and/or in the mobile device or its PMU, PMIC or
circuitry. FIG. 6 shows an embodiment where a microcontroller or
circuit inside the battery pack is included to accomplish the fuel
gauge task and report the state of charge to the device. This
circuitry can be the same, or different, from an ID chip used to
identify the battery and can communicate through a common battery
connector or a separate one.
[0191] In accordance with an embodiment, the firmware in the
receiver micro-controller plays an important role in the operation
of this battery pack. The micro-controller can measure voltages and
currents, flags, and temperatures at appropriate locations for
proper operation. In accordance with one embodiment, by way of
example, the micro-controller can measure the value of V.sub.out
from the rectifier circuit and attempt to keep this constant
throughout the charging cycle thereby providing a stable regulated
DC supply to the charger IC chip. The microcontroller can report
the value of this voltage or error from a desired voltage (for
example 5V) or simply a code for more or less power back to the
charger in a binary or multi-level coding scheme through a load
modulation or other scheme (for example RF communication, NFC,
Bluetooth, etc. as described earlier) back to the charger. The
charger can then take action through adjustment of input voltage to
the charger coil, adjustment of the frequency or duty cycle of the
AC voltage applied to the charger coil to bring the V.sub.out to
within required voltage range or a combination of these actions or
similar methods. The micro-controller throughout the charging
process, in addition, may monitor the end of charge and/or other
signals from charger and/or protection circuit and the current
sense circuit (used to sense battery pack current direction and
value) to take appropriate action. Li-Ion batteries for example
need to be charged below a certain temperature for safety reasons.
In accordance with an embodiment, it is therefore desirable to
monitor the cell, wireless power receiver coil or other temperature
and to take appropriate action, such as to terminate charging or
lower charging current, etc. if a certain maximum temperature is
exceeded.
[0192] In the example shown in FIG. 8, the battery cell voltage
increases from 3 V or lower, to 4.2 V, as it is charged. The
V.sub.out of the wireless power receiver is input to a charger IC
and if this V.sub.out is kept constant (for example 5V), a large
voltage drop (up to 2 V or more) can occur across this IC
especially during Stage 1 where maximum current is applied. With
charging currents of up to 1 A, this may translate to up to 2 Watts
of wasted power/heat across this IC that may contribute to battery
heating. In accordance with an embodiment, it is therefore
desirable to implement a strategy whereby the V.sub.out into the
charger IC tracks the battery voltage thereby creating a smaller
voltage drop and therefore loss across the charger IC. This can
provide a significant improvement in performance, since thermal
performance of the battery pack can be important.
User Application Layer (UAL):
[0193] In addition to the subsystems discussed earlier, a wireless
power transfer system can be designed to perform additional useful
functions or trigger further actions. The User Application Layer
(UAL) includes the hardware, firmware and software to provide such
communication and control functionalities that add such additional
functionalities and usefulness.
[0194] FIG. 21 shows a high level representation 310 of integration
of such a UAL layer into the charger and receiver, in accordance
with an embodiment. For example, the charger can be built into a
car, and when a valid receiver and/or an NFC, RFID or other ID
mechanism or the communication protocol in the receiver integrated
into or on a mobile device, its case or skin, dongle or battery is
found, the charger may activate some other functions such as
Bluetooth connectivity to the device, displaying the device
identity or its status or state of charge on a display or audibly,
etc. More advanced functions can also be activated or enabled by
placing a wireless receiver or mobile device with a wireless power
receiver on a wireless charger in a car. Examples include using the
device as an identification mechanism for the user and setting the
temperature of the car or the driver or passenger side to the
user's optimum pre-programmed temperature, setting the mirrors and
seats to the preferred setting, starting a radio station or music
preferred by user, etc., as described in U.S. Patent Publication
No. 20110050164, which application is herein incorporated by
reference.
[0195] In accordance with an embodiment, the charger/transmitter
may also include an RF signal amplifier/repeater and appropriate
antennas so that placement of a mobile device such as a mobile
phone, tablet, etc. would provide close coupling and/or turning on
of the amplifier and its antenna so that a better signal reception
for communication such as cell phone calls (GSM, 3G, 4G, etc.)
and/or the GPS signal can be obtained. Another example may be
integration of Bluetooth, Wi-Fi, NFC or other functionality into
the charger so that placement of a phone on or near a charger would
trigger identification or verification of a user and launch of an
application on the phone and/or the charger/automobile to perform
additional functionality. An example of the receiver UAL functions
may be that when a mobile device or phone is being charged or
powered in a car, the mobile device and/or the charger or the car
recognizes the mobile device or phone's location and automatically
switches to a mode where its display and or control functions are
mirrored to an in vehicle system (e.g., MirrorLink.TM.).
[0196] Other examples include when wireless charging of a mobile
device is initiated, an application in the mobile device is
launched and a visual and/or audio message is shown/played back to
indicate wireless charging or state of charge to the user. An
example may be to connect the phone to an onboard system and
antenna that would boost a signal from the phone or identify the
phone and its user so that the car can travel through toll booths
and a toll charged to the user's account as a car is traveling in
roadways/highways. Additionally, a similar system may pay for
parking in parking meters or parking structures or pay for power
charging of Electric vehicle in charging stations whether these
charging facilities provide wired or wireless charging. Another
example may be when the charger is an EV charger and in the UAL, it
is connected to a home Wi-Fi, Bluetooth, 2G, 3G, 4G, etc. wireless
network, it would allow remote monitoring or control of the
charging process by the user or a utility through a computer
program on a computer or an application running on a mobile device
such as tablet, phone, etc. Other novel uses of combination of the
charging station inside the car and integration/use of advanced
features can be implemented and the above descriptions are only
examples. Signal Boosters that include an antenna mounted on the
outside of a car, a bi-directional signal amplifier and a repeater
antenna inside a car are increasingly common.
[0197] In accordance with an embodiment, the actions launched or
started by setting a device on a charger can also be different in
different environments. Examples can include routing a mobile phone
call or music or video from a smart phone to the speakers and
microphones or video monitors or TV, computer, laptop, tablet, etc.
in a car, home, office, etc. Other similar actions or different
actions can be provided in other environments. In yet another
example, a combination speaker/Bluetooth system or a monitor or
television or a combination of such can also include a wireless
charger and when a mobile device such as a phone or tablet with
built-in or auxiliary wireless charging receiver (such as
integrated into a case or battery) is placed on the charger, it
would initiate charging but would also launch applications in the
charger/speaker and/or the mobile device to wireless connect or
pair the two parts so that other functions may start. Examples can
include playing the music on the mobile device through speakers or
pictures on the mobile device played through the television,
etc.
[0198] It is clear that the above discussions are as a way of
describing the possibilities available through the UAL and other
functionalities are possible. In general, the UAL greatly enhances
the features and usefulness possible with the wireless charging and
enables contextually aware charging.
[0199] In accordance with an embodiment, the firmware or the
software on the charger and/or the receiver can also be updated by
downloading and installation of a file or application over a
wireless connection (Wi-Fi, wired connection, 3G, 4G, Bluetooth,
etc.) or wired connection or installation through transfer of a
file from a storage device such as an memory device (USB, HD card,
etc.) or optical storage device, etc.
[0200] It can be readily appreciated that in the above descriptions
many geometries and systems have been described. In practice, one
or several of these systems can be used in combination in a charger
and/or receivers to provide the desired performance and
benefits.
[0201] In summary, the above approaches provide several important
attributes that enable a multi-receiver, position-free, wireless
power transfer (WPT) system to operate efficiently and safely,
including: [0202] A magnetic coil system that allows position free
multi-charging: Such performance can be achieved by taking
advantage of the magnetic resonance or loosely coupled systems,
flux guide (FG) structures, Magnetic Coupling (MC) or Magnetic
Aperture (MA) coil and/or magnetic structures as described above.
[0203] Design of receivers such that they include an output
regulator stage that allows operation of the receiver with a larger
rectified receiver coil output (V.sub.1 voltage in FIGS. 3, 9 and
18 and V.sub.out in FIG. 19) range of voltages. This can be
achieved, e.g., with output buck, boost or buck/boost regulator
stages or similar geometries. [0204] A communication method that
allows multiple receivers to communicate with a single or multiple
charger circuits and avoid message collision. The above approaches
generally focus on the in-band communication and/or through the
coil mostly, but this can be accomplished out of band and with
separate RF channel as well. [0205] To avoid collision in a WPT
system with in-band communication or through the coil, the messages
from each receiver can be sent at time intervals that are either
random or different from other receivers. If a collision occurs,
the charger can either ignore that message and wait for the next
one, or return to ping or reset state to resynchronize the
communication. [0206] A control algorithm for power transfer that
attempts to keep all the receivers operating such that the range of
the receiver voltage at its output stage regulator input is within
its acceptable operating range thus allowing simultaneous operation
and powering of multiple receivers.
[0207] In accordance with an embodiment, each of the attributes
described above can be provided within an appropriate WPT OSI model
layer described earlier. Within each layer, different aspects of
the technologies may be used, depending on the particular
implementation, with various elements of each of the above
attributes being provided within the overall system, to provide an
overall position-free efficient wireless charging system.
[0208] The above description and embodiments are not intended to be
exhaustive, and are instead intended to only show some examples of
the rich and varied products and technologies that can be
envisioned and realized by various embodiments of the invention. It
will be evident to persons skilled in the art that these and other
embodiments can be combined to produce combinations of above
techniques, to provide useful effects and products.
[0209] Some aspects of embodiments of the present invention can be
conveniently implemented using a conventional general purpose or a
specialized digital computer, microprocessor, or electronic
circuitry programmed according to the teachings of the present
disclosure. Appropriate software coding can readily be prepared by
skilled programmers and circuit designers based on the teachings of
the present disclosure, as will be apparent to those skilled in the
art.
[0210] In some embodiments, the present invention includes a
computer program product which is a storage medium (media) having
instructions stored thereon/in which can be used to program a
computer to perform any of the processes of the present invention.
The storage medium can include, but is not limited to, any type of
disk including floppy disks, optical discs, DVD, CD-ROMs,
microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs,
DRAMs, VRAMs, flash memory devices, magnetic or optical cards,
nanosystems (including molecular memory ICs), or any type of media
or device suitable for storing instructions and/or data.
[0211] The foregoing description of the present invention has been
provided for the purposes of illustration and description. It is
not intended to be exhaustive or to limit the invention to the
precise forms disclosed. Many modifications and variations will be
apparent to the practitioner skilled in the art. The embodiments
were chosen and described in order to best explain the principles
of the invention and its practical application, thereby enabling
others skilled in the art to understand the invention for various
embodiments and with various modifications that are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the following claims and their
equivalence.
* * * * *
References