PATENT DOCUMENT

Publication Number: US-10811913-B2
Application Number: US-201816196975-A
Country: US
Kind Code: B2

Title: Wireless charging system with multiple communications modes

Abstract:
A wireless power transmission system has a wireless power receiving device that can be charged using multiple different types of wireless power transmitting devices. The different types of wireless power transmitting devices have power transmitting coils that exhibit different levels of magnetic coupling with the power receiving coil of the wireless power receiving device. The wireless power receiving device may include capacitors, resistors, and/or other loading circuits that can be independently switched into use depending on the level of magnetic coupling that is detected, on a rectified voltage level, on the size of the output load, and/or on information conveyed during handshaking operations to present a desired impedance adjustment at the power receiving coil so that data signal can be properly conveyed between the power receiving device and the power transmitting device.

Claims:
What is claimed is: 
     
       1. A wireless power receiving device configured to receive wireless power signals from a first wireless power transmitting device or a second wireless power transmitting device, the wireless power receiving device comprising:
 a coil; 
 wireless power receiving circuitry coupled to the coil and configured to receive the wireless power signals from the coil; and 
 control circuitry operable to:
 configure the wireless power receiving device in a first data communications mode when a first level of magnetic coupling is present between the coil and a wireless power transmitting coil of the first wireless power transmitting device; and 
 configure the wireless power receiving device in a second data communications mode that is different than the first data communications mode when a second level of magnetic coupling is present between the coil and a wireless power transmitting coil of the second wireless power transmitting device. 
 
 
     
     
       2. The wireless power receiving device of  claim 1 , further comprising:
 a first switching capacitor coupled to a first end of the coil, wherein the first switching capacitor is selectively activated during the first data communications mode but not during the second data communications mode, and wherein the first and second wireless power transmitting devices are different types of wireless power transmitting devices. 
 
     
     
       3. The wireless power receiving device of  claim 2 , further comprising:
 a second switching capacitor coupled to the first end of the coil, wherein the second switching capacitor is selectively activated during the second data communications mode but not during the first data communications mode. 
 
     
     
       4. The wireless power receiving device of  claim 3 , wherein no switching capacitor is coupled to the second end of the coil. 
     
     
       5. The wireless power receiving device of  claim 3 , wherein the first switching capacitor has a first capacitance value, and wherein the second switching capacitor has a second capacitance value that is different than the first capacitance value. 
     
     
       6. The wireless power receiving device of  claim 5 , wherein the first level of magnetic coupling s greater than the second level of magnetic coupling, and wherein the first capacitance value is less than the second capacitance value. 
     
     
       7. The wireless power receiving device of  claim 3 , further comprising:
 a first switch that selectively activates the first switching capacitor, wherein the first switch is configured to receive a first data communications control signal from the control circuitry during the first data communications mode; and 
 a second switch that selectively activates the second switching capacitor, wherein the second switch is configured to receive a second data communications control signal from the control circuitry during the second data communications mode. 
 
     
     
       8. The wireless power receiving device of  claim 7 , wherein the control circuitry is configured to simultaneously modulate the first and second data communications control signals during a third data communications mode that is different than the first and second data communications mode. 
     
     
       9. The wireless power receiving device of  claim 3 , further comprising:
 rectifier circuitry coupled to the wireless power receiving circuitry, wherein the rectifier circuitry is operable in at least two different modes. 
 
     
     
       10. The wireless power receiving device of  claim 9 , wherein the rectifier circuitry is operable in a full-bridge rectifier mode during the first data communications mode and in a half-bridge rectifier mode during the second data communications mode. 
     
     
       11. A method of operating a wireless power receiving device having a wireless power receiving coil, the method comprising:
 during a first charging mode, receiving wireless power signals from a first wireless power transmitting device at the wireless power receiving coil, wherein a first level of coupling exists between the wireless power receiving coil and a wireless power transmitting coil of the first wireless power transmitting device; 
 during a second charging mode, receiving wireless power signals from a second wireless power transmitting device at the wireless power receiving coil, wherein a second level of coupling exists between the wireless power receiving coil and a wireless power transmitting coil of the second wireless power transmitting device, and wherein the second level of coupling is different than the first level of coupling; 
 configuring the wireless power receiving device in a first data communications mode during the first charging mode; and 
 configuring the wireless power receiving device in a second data communications mode during the second charging mode. 
 
     
     
       12. The method of  claim 11 , further comprising:
 with control circuitry within the wireless power receiving device, determining whether to configure the wireless power receiving device in the first data communications mode or the second data communications mode during handshaking operations. 
 
     
     
       13. The method of  claim 12 , further comprising:
 during the handshaking operations, initially configuring the wireless power receiving device in the first data communications mode; and 
 in response to performing a successful handshake, causing the wireless power receiving device to continue operating in the first data communications mode; and 
 in response to performing an unsuccessful handshake, causing the wireless power receiving device in the second data communications mode. 
 
     
     
       14. The method of  claim 11 , further comprising:
 during the first data communications mode, selectively activating a first capacitor coupled to a first end of the wireless power receiving coil; and 
 during the second data communications mode, selectively activating a second capacitor coupled to the first end of the wireless power receiving coil, wherein the first and second capacitors have different capacitance values. 
 
     
     
       15. The method of  claim 14 , further comprising:
 with rectifier circuitry in the wireless power receiving device, receiving the wireless power signals from the wireless power receiving coil; 
 configuring the rectifier circuitry as a full- bridge rectifier during the first data communications mode; and 
 configuring the rectifier circuitry as a half- bridge rectifier during the second data communications mode. 
 
     
     
       16. A wireless power receiving device comprising:
 a coil with a first terminal and a second terminal; 
 rectifier circuitry coupled to the first and second terminals of the coil; 
 a first passive component coupled to the first terminal of the coil, wherein the first passive component is selectively activated during a first data transmission mode, and wherein the first passive component is configured to provide a first amount of impedance change at the coil; and 
 a second passive component coupled to the first terminal of the coil, wherein the second passive component is selectively activated during a second data transmission mode, and wherein the second passive component is configured to provide a second amount of impedance change at the coil that is different than the first amount of impedance change. 
 
     
     
       17. The wireless power receiving device of  claim 16 , wherein the first and second passive components comprise electrical components selected from the group consisting of: capacitors and resistors. 
     
     
       18. The wireless power receiving device of  claim 16 , wherein the rectifier circuitry is configured as a full-bridge rectifier in the first data transmission mode and is configured as a half-bridge rectifier in the second data transmission mode. 
     
     
       19. The wireless power receiving device of  claim 18 , wherein the rectifier circuitry comprises:
 first and second diodes coupled to the first terminal of the coil; 
 third and fourth diodes coupled to the second terminal of the coil, wherein the fourth diode is shorted out during the second data transmission mode. 
 
     
     
       20. The wireless power receiving device of  claim 16 , further comprising:
 a first switch coupled in series with the first passive component; 
 a second switch coupled in series with the second passive component; and 
 control circuitry configured to generate a first control signal for modulating the first switch during the first data transmission mode and to generate a second control signal for modulating the second switch during the second data transmission mode. 
 
     
     
       21. A wireless power receiving device configured to receive wireless power signals from a wireless power transmitting device, the wireless power receiving device comprising:
 a coil; 
 wireless power receiving circuitry coupled to the coil and configured to receive the wireless power signals from the coil; 
 an adjustable load bank coupled to the coil; and 
 control circuitry operable to:
 configure the wireless power receiving device in a first data communications mode by activating at least a first portion of the adjustable load bank; and 
 configure the wireless power receiving device in a second data communications mode that is different than the first data communications mode by activating at least a second portion of the adjustable load bank. 
 
 
     
     
       22. The wireless power receiving device of  claim 21 , wherein the control circuitry is configured to dynamically adjust the adjustable load bank to ensure that adequate signal strength is maintained between the wireless power receiving device and the wireless power transmitting device. 
     
     
       23. The wireless power receiving device of  claim 21 , wherein the power receiving device further comprises rectifier circuitry connected to the coil, and wherein the control circuitry is further configured to adjust the adjustable load bank at least partially based on a rectified voltage output from the rectifier circuitry. 
     
     
       24. The wireless power receiving device of  claim 23 , wherein the rectifier circuitry is operable in a full-bridge rectifier mode and in a half-bridge rectifier mode. 
     
     
       25. The wireless power receiving device of  claim 23 , wherein the rectifier circuitry is coupled between the coil and the adjustable load bank. 
     
     
       26. The wireless power receiving device of  claim 21 , wherein the power receiving device further comprises an output load coupled to the coil, and wherein the control circuitry is further configured to adjust the adjustable load bank at least partially based on the size of the output load. 
     
     
       27. The wireless power receiving device of  claim 21 , wherein the wireless power transmitting device is of a given transmitter type and operates using a given communications protocol, wherein information about the given transmitter type or the given communications protocol is conveyed from the wireless power transmitting device to the control circuitry during handshaking operations, and wherein the control circuitry is further configured to adjust the adjustable load bank at least partially based on the information conveyed during the handshaking operations. 
     
     
       28. The wireless power receiving device of  claim 21 , wherein the adjustable load bank comprises an array of individually selectable components selected from the group consisting of: capacitors, resistors, constant current loads, and ballast loads.

Description:
This application claims the benefit of provisional patent application No. 62/715,167, filed Aug. 6, 2018, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to wireless systems, and, more particularly, to systems in which devices are wirelessly charged. 
     BACKGROUND 
     In a wireless charging system, a wireless power transmitting device such as a device with a charging surface wirelessly transmits power to wireless power receiving device such as a portable electronic device. The portable electronic device receives the wirelessly transmitted power and uses this power to charge an internal battery or to power the device. 
     It may sometimes be desirable to transmit data from the wireless power receiving device to the wireless power transmitting device. So-called “in-band” communications schemes have been developed that allow wireless power receiving devices to communicate with wireless power transmitting devices. In a typical in-band communications scheme, a switching circuit that is coupled to a coil in the wireless power receiving device is used to modulate the load across the coil. The wireless power transmitting device will attempt to detect the modulated signal using a sensing circuit coupled to a coil in the wireless power transmitting device. 
     Sometimes, however, changing the load across the coil at the wireless power receiving device does not necessarily translate to a sufficiently detectable amplitude or phase change at the sensing circuit of the wireless power transmitting device. 
     SUMMARY 
     A wireless power transmission system has a wireless power receiving device that can be charged either using a first wireless power transmitting device having a first coil configuration or a second wireless power transmitting device having a second coil configuration that is different than the first coil configuration. The wireless power receiving device may include a wireless power receiving coil, wireless power receiving circuitry coupled to the wireless power receiving coil, and control circuitry operable to: (1) configure the wireless power receiving device in a first data communications (or transmission) mode when a first magnetic coupling coefficient is present between the wireless power receiving coil and the first coil configuration of the first wireless power transmitting device and (2) configure the wireless power receiving device in a second data communications (or transmission) mode when a second magnetic coupling coefficient is present between the wireless power receiving coil and the second coil configuration of the second wireless power transmitting device. 
     The wireless power receiving device may further include a first switching capacitor (or resistor) that is coupled to a first end of the wireless power receiving coil and a second switching capacitor (or resistor) that is also coupled to the first end of the coil. The first switching capacitor is selectively activated only during the first data communications mode but not during the second data communications mode. The second switching capacitor is selectively activated only during the second data communications mode but not during the first data communications mode. There is no switching capacitor is coupled to the second end of the wireless power receiving coil. The first and second switching capacitors have substantially different capacitance values. The wireless power receiving device may further include rectifier circuitry coupled to the wireless power receiving circuitry. The rectifier circuitry is operable in a full-bridge rectifier mode during the first data communications mode and in a half-bridge rectifier mode during the second data communications mode. 
     The control circuitry may determine whether to configure the wireless power receiving device in the first data communications mode or the second data communications mode during handshaking operations. During handshaking, the control circuitry may initially configure the wireless power receiving device in the first data communications mode. Responsive to performing a successful handshake, the control circuitry may then allow the wireless power receiving device to continue operating in the first data communications mode. Response to performing an unsuccessful handshake, however, the control circuitry may reconfigure the wireless power receiving device in the second data communications mode and reattempt the handshake. 
     In accordance with another suitable arrangement, the wireless power receiving device may include an adjustable capacitive bank (e.g., a capacitive array) coupled to the coil and control circuitry operable to configure the wireless power receiving device in a first data communications mode by activating at least a first portion of capacitors in the adjustable capacitive bank and to configure the wireless power receiving device in a second data communications mode by activating at least a second portion of capacitors in the adjustable capacitive bank. The control circuitry may dynamically adjust the adjustable capacitive bank to ensure that adequate signal strength is maintained between the wireless power receiving device and the wireless power transmitting device. The control circuitry may be configured to adjust the capacitive bank at least partially based on a rectified voltage output from the rectifier circuitry, on the size of the load driven by the rectifier circuitry, on the type of the wireless power transmitting device, and/or on the communications protocol specified by the power transmitting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system in accordance with embodiments. 
         FIG. 2  is a circuit diagram of an illustrative wireless charging system in accordance with an embodiment. 
         FIG. 3  is a circuit diagram of an illustrative wireless power receiving device having identical capacitors selectively coupled to both terminals of a wireless power receiving coil when transmitting data to a wireless power transmitting device in accordance with an embodiment. 
         FIG. 4  is a circuit diagram of an illustrative wireless power receiving device having capacitors of varying values that are selectively coupled to only one terminal of a wireless power receiving coil when transmitting data to a wireless power transmitting device in accordance with an embodiment. 
         FIG. 5  is a diagram of various wireless in-band communications modes in which a wireless power receiving device of the type shown in  FIG. 4  may be operated in accordance with an embodiment. 
         FIG. 6  is a flow chart of illustrative steps for configuring a wireless power receiving device of the type shown in  FIG. 4  for proper data transmission in accordance with an embodiment. 
         FIG. 7  is a circuit diagram of an illustrative wireless power receiving device having a capacitive bank configurable to support different types of wireless power transmitting devices in accordance with an embodiment. 
         FIGS. 8A-8D  are diagrams of different illustrative receiver tuning topologies that can be implemented at the wireless power receiving device in accordance with some embodiments. 
         FIG. 9  is a diagram of various wireless in-band communications modes in which a wireless power receiving device of the type shown in  FIG. 7  may be operated in accordance with an embodiment. 
         FIG. 10  is a flow chart of illustrative steps for configuring a wireless power receiving device of the type shown in  FIG. 7  for proper data transmission in accordance with an embodiment. 
         FIG. 11  is a diagram of an illustrative resistive bank that can be used in the wireless power receiving device of the type shown in  FIG. 7  in accordance with an embodiment. 
         FIG. 12  is a diagram of an illustrative load bank having both capacitors and resistors in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system has a wireless power transmitting device that transmits power wirelessly to a wireless power receiving device. The wireless power transmitting device has one or more coils that are used in transmitting wireless power to one or more wireless power receiving coils in the wireless power receiving device. During operation, the wireless power transmitting device supplies alternating-current signals to one or more wireless power transmitting coils. This causes the coils to transmit alternating-current electromagnetic signals (sometimes referred to as wireless power signals) to one or more corresponding coils in the wireless power receiving device. Rectifier circuitry in the wireless power receiving device converts received wireless power signals into direct-current (DC) power for powering the wireless power receiving device. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  8  includes wireless power transmitting device  12  and one or more wireless power receiving devices such as wireless power receiving device  10 . Device  10  is a portable electronic device such as a wristwatch, a cellular telephone, a media player, a pair of earbuds, a remote control, a tablet computer, a laptop computer, an electronic stylus, pen, or pencil, or other electronic equipment. Device  12  may be a stand-alone device such as a wireless charging mat, wireless charging puck, wireless charging stand, wireless charging table, a desktop computer, a laptop computer, a tablet, or other suitable wireless charging equipment. 
     Devices  12  and  10  include control circuitry  42  and  20 , respectively. Control circuitry  42  and  20  includes storage and processing circuitry such as microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. Control circuitry  42  and  20  is configured to execute instructions for implementing desired control and communications features in system  8 . For example, control circuitry  42  and/or  20  may be used in determining power transmission levels, processing sensor data, processing user input, processing other information such as information on wireless coupling efficiency from transmitting circuitry  34 , processing information from receiving circuitry  46 , using information from circuitry  34  and/or  46  such as signal measurements on output circuitry in circuitry  34  and other information from circuitry  34  and/or  46  to determine when to start and stop wireless charging operations, adjusting charging parameters such as charging frequencies, coil assignments in a multi-coil array, and wireless power transmission levels, and performing other control functions. 
     Control circuitry  42  and/or  20  may be configured to perform these operations using hardware (e.g., dedicated hardware or circuitry) and/or software (e.g., code that runs on the hardware of system  8 ). Software code for performing these operations is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media). The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid-state drives), one or more removable flash drives or other removable media, other computer readable media, or combinations of these computer readable media or other storage. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry  42  and/or  20 . The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, or other processing circuitry. 
     During operation of system  8 , a user places one or more devices  10  on the charging surface of device  12 . Device  10  may also be otherwise attached or mounted to device  12  during wireless charging operations. Power transmitting device  12  is optionally coupled to a source of alternating-current voltage such as an alternating-current power source (e.g., a wall outlet that supplies line power or other source of mains electricity), has a battery such as battery  38  for supplying power, and/or is coupled to another source of power. A power converter such as AC-DC power converter  40  can convert power from a main power source or other AC power source into DC power that is used to power control circuitry  42  and other circuitry in device  12 . During operation, control circuitry  42  uses wireless power transmitting circuitry  34  and one or more coils  36  coupled to circuitry  34  to transmit alternating-current electromagnetic signals  48  to device  10  and thereby convey wireless power to wireless power receiving circuitry  46  of device  10 . Coils  36  are therefore sometimes referred to as wireless power transmitting coils or wireless power transfer coils. In general, device  12  may have any suitable number of coils  36  (e.g., 1-100 coils, 5-25 coils, more than 100 coils, more than 5 coils, more than 10 coils, fewer than 40 coils, fewer than 30 coils, etc.), and device  10  may have any suitable number of coils  14 . 
     Wireless power transmitting circuitry  34  has switching circuitry (e.g., transistors in an inverter circuit) that are turned on and off based on control signals provided by control circuitry  42  to create AC current signals through appropriate coils  36 . As the AC currents pass through a coil  36  that is being driven by the inverter circuit, alternating-current electromagnetic fields (wireless power signals  48 ) are produced that are received by one or more corresponding coils  14  coupled to wireless power receiving circuitry  46  in receiving device  10 . When the alternating-current electromagnetic fields are received by coil  14 , corresponding alternating-current currents and voltages are induced in coil  14 . 
     Rectifier circuit  80 , which is sometimes considered to be part of circuitry  46 , converts the received AC signals (e.g., received alternating-current currents and voltages associated with wireless power signals  48 ) from one or more coils  14  into DC voltage signals for powering device  10 . The DC voltages are used in powering components in device  10  such as sensors  54  (e.g., accelerometers, force sensors, temperature sensors, light sensors, pressure sensors, gas sensors, moisture sensors, magnetic sensors, etc.), wireless communications circuitry  56  for communicating wirelessly with control circuitry  42  of device  12  and/or other equipment, audio components, and other components (e.g., input-output devices  22  and/or control circuitry  20 ) and are used in charging an internal battery in device  10  such as battery  18 . 
     Device  12  and/or device  10  may communicate wirelessly. Devices  10  and  12  may, for example, have wireless transceiver circuitry in control circuitry  42  and  20  (and/or wireless communications circuitry such as circuitry  56 ) that allows wireless transmission of signals between devices  10  and  12  (e.g., using antennas that are separate from coils  36  and  14  to transmit and receive unidirectional or bidirectional wireless signals, using coils  36  and  14  to transmit and receive unidirectional or bidirectional wireless signals, etc.). 
     When it is desired to transmit data from device  12  to device  10 , data transmitter circuitry  100  in control circuitry  42  may be used in modulating the signals that are supplied to coil  36 . Control circuitry  20  of power receiving device  10  may use a data receiver circuit such as data receiver  104  to demodulate the modulated signal pulses from transmitter  100 . Conversely, data transmitter circuit  106  of device  10  may be used in producing signals that are transmitted by coil  14  to coil  36  of device  12  and that are demodulated by data receiver  102  in control circuitry  42  of device  12 . 
     When it is desired to transmit data from device  10  to device  12 , device  12  may optionally cease transmission of power. While device  12  is not transmitting wireless power to device  10 , data transmitter circuit  106  of device  10  may modulate one or more transistors in wireless power receiving circuitry  46  or control circuitry  20 , thereby creating wireless signals that are transmitted from coil  14  to coil  36  of device  12 . Because data signals are conveyed wirelessly from device  10  to device  12  using coils  14  and  36 , this type of data communications between device  10  and device  12  may sometimes be referred to as “in-band” communications. Device  12  may use data receiver  102  to demodulate the wireless signals from device  10  and thereby receive the data transmitted from device  10 . The transmitted data may be used to enable communication between device  10  to device  12 , for example to supply feedback or other control signals to device  12 , or may be used to convey other information. This example in which transmission of power is temporarily suspended during data transmission is merely illustrative. If desired, wireless power transmission and data reception may occur simultaneously (without ceasing the transmission of power). 
     When device  12  is in power transmission mode, control circuitry  42  may use pulse-width modulation (PWM) to modulate the AC drive signals that are being supplied to output inverter transistors coupled to coil  36  and thereby adjust how much power is being supplied to device  10 . For instance, the duty cycle of the PWM pulse train may be adjusted dynamically to adjust the amount of power being wirelessly transmitted from device  12  to device  10 . The duty cycle of the PWM pulses may, if desired, be adjusted based on power transmission feedback information that is conveyed in-band from data transmitter  106  to data receiver  102 . For example, device  12  can use information that has been transmitted back from device  10  to device  12  to increase or decrease the amount of transmitted power that device  12  is providing to device  10 . 
     The output inverter transistors in wireless power transmitting circuitry  34  are modulated to create an AC output waveform signal suitable for driving coil  36  for wireless power transfer. In some examples this signal has a frequency in the kilo-Hertz range, such as between 100 to 400 kHz, including frequencies particularly in the 125 to 130 kHz range. In some examples this signal is in the mega-Hertz range, such as about 6.78 MHz or more generally between 1 to 100 MHz. In some examples this signal is in the giga-Hertz range, such as about 60 GHz and more generally between 1 to 100 GHz. As this AC signal passes through coil  36 , a corresponding wireless power signal (electromagnetic signal  48 ) is created and conveyed to coil  14  of device  10 . This AC frequency at which power transmitting circuitry  34  is modulated is sometimes referred to as the power carrier frequency. Data signals received at receiver  102  may be modulated at a lower frequency. The frequency at which data being transmitted from device  10  to device  12  is modulated is sometimes referred to as the “data rate.” For example, when transferring power in the 100 kHz range, the data rate may be 2 kHz, 1-10 kHz, 10-50 kHz, less than 100 kHz, less than 80 kHz, less than 50 kHz, or other suitable frequency above or below 2 kHz. 
     A circuit diagram of illustrative circuitry for wireless power transfer (wireless power charging) system  8  is shown in  FIG. 2 . As shown in  FIG. 2 , wireless power receiving device  10  may be charged using either a first power transmitting device  12 - 1  or a second power transmitting device  12 - 2 . Each of the first and second wireless power transmitting devices  12 - 1  and  12 - 2  includes wireless power transmitting circuitry  34  having an inverter such as inverter  70  or other drive circuit that produces alternating-current drive signals such as variable-duty-cycle square waves or other drive signals. These signals are driven through an output circuit such as output circuit  68  that includes coil(s)  36  and capacitor(s)  72  to produce wireless power signals that are transmitted wirelessly to device  10 . 
     Control circuitry  42  in each of devices  12 - 1  and  12 - 2  may also contain wireless transceiver circuits (e.g., data transmitter  100  and data receiver  102  of  FIG. 1 ) for supporting wireless data transmission between devices  10  and  12  (i.e., device  12 - 1  or  12 - 2 ). In device  10 , wireless transceiver circuits in control circuitry  20  (e.g., data receiver  104  and data transmitter  106  of  FIG. 1 ) can use path  88  and coil  14  to transmit data to either device  12 - 1  or device  12 - 2 . In each of devices  12 - 1  and  12 - 2 , paths such as path  74  may be used to supply incoming data signals that have been received from device  10  using coil  36  to demodulating (receiver) circuitry in the data receiver of control circuitry  42 . If desired, path  74  may also be used in transmitting wireless data to device  10  using coil(s)  36  that is received by the data receiver of circuitry  20  using coil  14  and path  88 . 
     During wireless power transmission operations, transistors in inverter  70  are controlled using AC control signals generated by control circuitry  42 . Control circuitry  42  uses control path  76  to supply control signals to the gates of the transistors in inverter  70 . The duty cycle and/or other attributes of these control signals and therefore the corresponding characteristics of the drive signals applied by inverter  70  to coil  36  and the corresponding wireless power signals produced by coil  36  can be adjusted dynamically. Using switching circuitry, control circuitry  42  selects which coil or coils to supply with drive signals. Using duty cycle adjustments and/or other adjustments (e.g., drive frequency adjustments, etc.), control circuitry  42  can adjust the strength of the drive signals applied to each coil. 
     Wireless power receiving device  10  has wireless power receiving circuitry  46 . Circuitry  46  includes rectifier circuitry such as rectifier  80  (e.g., a synchronous rectifier controlled by signals from control circuitry  20 ) that converts received alternating-current signals from coil  14  (e.g., wireless power signals received by coil  14 ) into direct-current (DC) power signals for powering circuitry in device  10  such as load  82  (sometimes referred to as an output load). Load circuitry such as load  82  may include battery  18 , a power circuit such as a battery charging integrated circuit or other power management integrated circuit(s) that receives power from rectifier circuitry  80  and regulates the flow of this power to battery  18 , and/or other input-output devices  22  ( FIG. 1 ). As shown in  FIG. 2 , one or more capacitors Crx and Crx′ are used to couple coil  14  in input circuit  90  of device  10  to input terminals of rectifier circuitry  80 . Coupling capacitor Crx′ is optional. Rectifier circuitry  80  produces corresponding output power at output terminals that are coupled to load  82 . If desired, load  82  may include sensor circuitry (e.g., current and voltage sensors) for monitoring the flow of power from rectifier  80  to load  82 . 
     The ability of device  10  to communicate with or to be charged by device  12  may depend on the inductive (or magnetic) coupling between the coils  14  and  36 . The amount of magnetic coupling between coils  14  and  36  may depend on the number of coils  36 , the number of active coils  36  (e.g., control circuitry  42  might use multiplexing circuitry to switch a portion of coils  36  into use while deactivating another portion of coils  36 ), the amount of overlapping among coils  36 , the orientation of coils  36  relative to coil  14 , the winding of coils  14  and  36 , or other physical attribute associated with coils  14  and  36 . 
     In the example of  FIG. 2 , power transmitting device  12 - 1  has coil(s)  36 - 1  of a first configuration, whereas power transmitting device  12 - 2  has coil(s)  36 - 2  of a second configuration that is different than the first coil configuration. In other words, the physical arrangement and/or the number of coils may be different between devices  12 - 1  and  12 - 2 . As a result, a first amount of magnetic coupling may exist between device  12 - 1  and device  10  when device  10  is charged using device  12 - 1  (as indicated by a first coupling coefficient k 1 ), whereas a second amount of magnetic coupling may exist between device  12 - 2  and device  10  when device  10  is charged using device  12 - 2  (as indicated by a second coupling coefficient k 2 ). Coefficients k 1  and k 2  are sometimes referred to as magnetic coupling coefficients, electromagnetic coupling coefficients, or inductive coupling coefficients. 
     As described above, a data transmitter circuit such as data transmitter  106  in control circuitry  20  of device  10  may be configured to modulate one or more transistors in wireless power receiving circuitry  46  to transmit “in-band” data signals from coil  14  to coil  36  of device  12  (e.g., device  10  modulates the data to be transmitted by changing the impedance at coil  14 ). Device  12  may be configured to decode the corresponding data by sensing the perturbation in the waveform based on the impedance changes at coil  14 . In general, any suitable modulation scheme may be used to support transmission of data signals from device  10  to device  12 . As an example, transmitter  106  may modulate transmitted data using a modulation scheme such as amplitude-shift keying (ASK) modulation. 
     Conventionally, the data transmitter at device  10  is capable of generating only one step load current change. For instance, the data transmitter includes only a pair of capacitors with equal capacitance for adjusting the impedance at coil  14 . Modulating data by switching the pair of capacitors in and out of use might produce a satisfactory response at device  12 - 1 , assuming coupling coefficient k 1  is large enough to induce a sufficiently detectable perturbation at coil  36 - 1 . Device  10  configured in this way might also be capable of properly transmitting data signals to device  12 - 2  if coupling coefficient k 2  is substantially similar to coupling coefficient k 1  (e.g., if k 2  deviates from k 1  by less than 1% of k 1 , by less than 5% of k 1 , by less than 10% of k 1 , by less than 20% of k 1 , etc.). In situations where coupling coefficient k 2  is substantially different than coupling coefficient k 1  (e.g., if k 2  deviates from k 1  by more than 20% of k 1 , by more than 30% of k 1 , by more than 50% of k 1 , by more than 100% of k 1 , etc.), modulating data by switching the same pair of identical capacitors in and out of use would risk not producing a satisfactory response at device  12 - 2  if coupling coefficient k 2  is too small to induce a sufficiently detectable perturbation at coil  36 - 2 . 
     To enable device  10  to communicate effectively with two or more power transmitting devices exhibiting different coupling coefficients or different levels of magnetic coupling with coil  14 , device  10  may be provided with at least two different sets of capacitors, where a first set of capacitors generates a first step load (or impedance) change that is suitable for communicating with device  12 - 1  during a first charging mode and where a second set of capacitors generates a second step load (or impedance) change that is suitable for communicating with device  12 - 2  during second charging mode. 
       FIG. 3  is a circuit diagram of an illustrative wireless power receiving device  10  that is provided with at least two sets of capacitors for modulating the impedance at coil  14  for transmitting data signals back to the wireless power transmitting device. As shown in  FIG. 3 , a first capacitor Cx 1  has a first terminal that is coupled to node  302 , which connects capacitor Crx to rectifier circuitry  80 , and a second terminal that is coupled to switch Q 1 . A second capacitor Cx 2  has a first terminal that is coupled to node  304 , which connects capacitor Crx′ to rectifier circuitry  80 , and a second terminal that is coupled to switch Q 2 . Capacitor Crx′ may be optional. If capacitor Crx′ is omitted, node  304  would be directly connected to coil  14 . Capacitors Cx 1  and Cx 2  and switches Q 1  and Q 2  may be considered as part of data transmitter  106  ( FIG. 1 ), as separate from data transmitter  106  but also part of control circuitry  20 , or as part of wireless power receiving circuitry  46 . 
     Switches Q 1  and Q 2  may be implemented as complementary metal-oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), micro-electro-mechanical systems (MEMS) switches, or other suitable types of electrical switches. Transistors Q 1  and Q 2  may have source terminals that are connected to a ground power supply line and gate terminals that receive a first control signal Vcom 1  from control circuitry  20 . Configured in this way, control circuitry  20  may toggle Vcom 1  to modulate transistors Q 1  and Q 2  to simultaneously switch capacitors Cx 1  and Cx 2  into use to effect a first amount of impedance change at coil  14 . Since capacitors Cx 1  and Cx 2  are switched on and off at the same time across both terminals of coil  14 , the capacitance value of Cx 1  and Cx 2  should be equal (e.g., capacitors Cx 1  and Cx 2  are equally sized and should be symmetrically coupled to both ends of coil  14 ). 
     Modulating data communications signal Vcom 1  to switch the first set of capacitors Cx 1  and Cx 2  into use may be suitable for transmitting data signals to device  12 - 1  (e.g., capacitors Cx 1  and Cx 2  are designed to operate effectively with coupling coefficient k 1 ). In general, if the magnetic coupling coefficient is small, a larger switching capacitance is needed at coil  14  to effectuate the desired amount of response at coil  36 . On the other hand, if the magnetic coupling coefficient is large, a smaller switching capacitance is needed at coil  14  to produce a detectable response at coil  36 . 
     Still referring to  FIG. 3 , a third capacitor Cy 1  has a first terminal that is coupled to node  302  and a second terminal that is coupled to switch Q 3 . A fourth capacitor Cy 2  has a first terminal that is coupled to node  304  and a second terminal that is coupled to switch Q 4 . Capacitors Cy 1  and Cy 2  and switches Q 3  and Q 4  may be considered as part of data transmitter  106  ( FIG. 1 ), as separate from data transmitter  106  but also part of control circuitry  20 , or as part of wireless power receiving circuitry  46 . Switches Q 3  and Q 4  may be implemented as complementary metal-oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), micro-electro-mechanical systems (MEMS) switches, or other suitable types of electrical switches. 
     Transistors Q 3  and Q 4  may have source terminals that are connected to ground and gate terminals that receive a second control signal Vcom 2  from control circuitry  20 . Configured in this way, control circuitry  20  may toggle signal Vcom 2  to modulate transistors Q 3  and Q 4  to simultaneously switch capacitors Cy 1  and Cy 2  into use to effect a second amount of impedance change at coil  14 . Since capacitors Cy 1  and Cy 2  are switched on and off at the same time across nodes  302  and  304 , the capacitance value of Cy 1  and Cy 2  should be equal (e.g., capacitors Cy 1  and Cy 2  have identical dimensions and should be symmetrically coupled to both ends of coil  14 ). 
     Modulating data communications signal Vcom 2  to switch the second set of capacitors Cy 1  and Cy 2  into use may be suitable for transmitting data signals to device  12 - 2  (e.g., capacitors Cy 1  and Cy 2  are designed to operate effectively with coupling coefficient k 2 ). Assuming coefficients k 1  and k 2  are substantially different, the capacitance of Cx 1  and Cx 2  should also be different from the capacitance of Cy 1  and Cy 2 . As an example, if coupling coefficient k 1  is larger than coefficient k 2 , then the capacitance of Cx 1  and Cx 2  should be less than the capacitance of Cy 1  and Cy 2 . As another example, if coupling coefficient k 1  is smaller than coefficient k 2 , then the capacitance of Cx 1  and Cx 2  should be greater than the capacitance of Cy 1  and Cy 2 . 
     If desired, the capacitors (e.g., Cx 1 , Cx 2 , Cy 1 , and Cy 2 ) may be replaced with resistors, a combination of resistive and capacitive circuits connected in any series or parallel configuration, or other passive electrical components suitable for effectuating the desired amount of impedance change at wireless power receiving coil  14 . Rectifier circuitry  80  may be configured as a full-bridge or half-bridge rectifier, depending on the output voltage requirements at load  82 . The example of  FIG. 3  in which two different sets of capacitors can be independently modulated depending on the perceived coupling coefficient is merely illustrative. If desired, additional sets or pairs of capacitors may be included to enable device  10  to communicate with any number of wireless power transmitting devices with different coupling coefficients. 
     In the example of  FIG. 3 , four switching capacitors Cx 1 , Cx 2 , Cy 1 , and Cy 2  are needed for device  10  to communicate under two different modes: (1) a first mode for transmitting data to device  12 - 1  via a first coupling coefficient k 1  and (2) a second mode for transmitting data to device  12 - 2  via a second substantially different coupling coefficient k 2 . Using four switching capacitors in this way, however, takes up valuable circuit area and increases the cost of device  10 . To save cost, space, and energy, switching capacitors can be coupled to only one end of coil  14  (see, e.g.,  FIG. 4 ). 
     As shown in  FIG. 4 , a first capacitor C 1  has a first terminal coupled to node  402 , which connects capacitor Crx to rectifier circuitry  80 , and a second terminal coupled to switch  410 . A second capacitor C 2  has a first terminal coupled to node  402  and a second terminal coupled to switch  412 . Switches  410  and  412  may be implemented as complementary metal-oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), micro-electro-mechanical systems (MEMS) switches, or other suitable types of electrical switches. Capacitors C 1  and C 2  and switches  410  and  412  may be considered as part of data transmitter  106  ( FIG. 1 ), as separate from data transmitter  106  but also part of control circuitry  20 , or as part of wireless power receiving circuitry  46 . 
     Switch  410  has a gate terminal that receives first communications control signal Vcom 1  from control circuitry  20 , whereas switch  412  has a gate terminal that receives second communications control signal Vcom 2  from control circuitry  20 . Control circuitry  20  may either modulate signal Vcom 1  when communicating with power transmitting device  12 - 1  or modulate signal Vcom 2  when communicating with power transmitting device  12 - 2 . Modulating data communications signal Vcom 1  to switch capacitor C 1  into use may be suitable for transmitting data signals to device  12 - 1  (e.g., capacitor C 1  is designed to operate effectively with coupling coefficient k 1 ). Alternatively, modulating data communications signal Vcom 2  to switch capacitor C 2  into use may be suitable for transmitting data signals to device  12 - 2  (e.g., capacitor C 2  is designed to operate effectively with coupling coefficient k 2 ). 
     Assuming coefficients k 1  and k 2  are substantially different, the capacitance of C 1  should also be different from the capacitance of C 2 . As an example, if coupling coefficient k 1  is larger than coefficient k 2 , then the capacitance of C 1  should be less than the capacitance of C 2 . As another example, if coupling coefficient k 1  is smaller than coefficient k 2 , then the capacitance of C 1  should be greater than the capacitance of C 2 . If desired, signals Vcom 1  and Vcom 2  can be modulated simultaneously (e.g., to switch both capacitors C 1  and C 2  into use) to effectuate a third step load or impedance change at coil  14  that is suitable for yet another coupling coefficient that is different than k 1  or k 2 . 
     The example of  FIG. 4  where only two switching capacitors C 1  and C 2  are needed for device  10  to operate in the two different data transmission modes (as opposed to using four capacitors and associated switches in  FIG. 3 ) can therefore help save area and reduce power consumption for device  10 . If desired, switching capacitors C 1  and C 2  may be replaced with resistors, a combination of resistive and capacitive circuits connected in any series or parallel configuration, or other passive electrical components suitable for effectuating the desired amount of impedance change at wireless power receiving coil  14 . If desired, one or more additional switching capacitors may be connected to node  402  (as indicated by path  450 ) to enable device  10  to communicate with any number of wireless power transmitting devices with different coupling coefficients, where each additional switching capacitor has a different or equal capacitance as capacitor C 1  or capacitor C 2 . 
     Rectifier circuitry  80  may be operable as either a full-bridge or half-bridge rectifier, depending on the output voltage requirements at load  82 . As shown in  FIG. 4 , rectifier circuitry  80  may include a first diode D 1  having a first (p-type) terminal connected to node  402  and a second (n-type) terminal connected to load  82 , a second diode D 2  having a first (p-type) terminal connected to the ground line and a second (n-type) terminal connected to node  402 , a third diode D 3  having a first (p-type) terminal connected to node  404  (which is connected to coil  14  via optional coupling capacitor Crx′) and a second (n-type) terminal connected to load  82 , and a fourth diode D 4  having first (p-type) terminal connected to the ground line and a second (n-type) terminal connected to node  404 . Note that no switching capacitor is coupled to node  404  (i.e., switching capacitors such as C 1  and C 2  are only coupled to node  402 ). 
     The mode is which rectifier circuitry  80  is operated should also depend on the coupling coefficient. When device  10  is being charged by device  12  via a relatively low coupling coefficient k_low, a smaller AC signal will be induced at wireless power receiving circuitry  46 , which is more suitable for half-bridge rectification. In such scenarios, switch  420  may be turned on to short out diode D 4  (i.e., by connecting node  404  directly to ground). Enabling switch  420  also effectively disables diode D 3  since the p-type terminal of diode D 3  is fixed at ground. On the other hand, when device  10  is being charged by device  12  via a relatively high coupling coefficient k_high, a larger AC signal will be induced at wireless power receiving circuitry  46 , which is more suitable for full-bridge rectification. In such scenarios, switch  420  is turned off, thus enabling all diodes D 1 -D 4  for normal full-bridge rectifying operations. 
       FIG. 5  is a diagram showing various wireless in-band communications modes in which device  10  of the type shown in  FIG. 4  may be operated. As shown in  FIG. 5 , device  10  may be operated in a first data communications mode  500 . Mode  500  may be suitable for transmitting data to a corresponding wireless power transmitting device where the coupling coefficient k is large. During mode  500 , capacitor C 1  may be enabled by modulating switch  410  while capacitor C 2  is idle by keeping switch  412  off (assuming capacitor C 1  is smaller than C 2 ). When the coupling coefficient is large, rectifier circuitry  80  may be configured as a full-bridge rectifier (e.g., by deactivating switch  420 ). 
     Device  10  may also be operable in a second data communications mode  502 . Mode  502  may be suitable for transmitting data to a corresponding wireless power transmitting device where the coupling coefficient k is small. During mode  502 , capacitor C 2  may be switched into use by modulating switch  412  while capacitor C 1  is switched out of us by keeping switch  410  idle (again assuming capacitor C 1  is smaller than C 2 ). When the coupling coefficient is small, rectifier circuitry  80  may be configured as a half-bridge rectifier (e.g., by activating switch  420 ). 
     Device  10  may optionally be operable in one or more additional data communications mode(s)  504 . Mode  504  may be suitable for transmitting data to a corresponding wireless power transmitting device where the coupling coefficient k has some other value different than those covered by modes  500  and  502 . During mode  504 , some other combination of capacitors (or resistors) may be switched into use using one or more additional switches, and rectifier circuitry  80  may be configured in either the full-bridge or half-bridge mode depending on the voltage requirements at load  82 . 
       FIG. 6  is a flow chart of illustrative steps for configuring wireless power receiving device  10  of the type shown in  FIG. 4  for proper data transmission. A user may first bring a power receiving device  10  into proximity of a power transmitting device  12 . For example, the user may place device  10  on a charging surface of device  12  or may otherwise attach or mount device  10  onto device  12 . 
     At step  600 , power transmitting device  12  may detect the power receiving device  10  and may attempt to perform handshaking with power receiving device  10 . Example handshaking operations that may be performed between devices  10  and  12  may include performing device authentication (e.g., to authenticate device  10  to device  12 ), to detect supported power capabilities of receiving device  10  (e.g., so that power transmitting device  12  can transmit power to device  10  using the right power settings), to negotiate appropriate power transmission levels, and other handshaking protocols that might be needed to establish a link for proper wireless power transfer from device  12  to device  10  and proper wireless data transfer between devices  10  and  12 . 
     At step  602 , power receiving device  10  may attempt to perform handshaking with power transmitting device  12  using a first (default) communications mode (e.g., mode  500  of  FIG. 5 ). At step  604 , power receiving device  10  may determine whether a successful handshake has occurred. For example, a successful handshake operation might occur when power receiving device  10  receives a handshake acknowledgement packet from device  12 . If handshaking is successful, then no further mode change is needed at power receiving device  10  (e.g., power receiving device  10  may continue to operate and transmit in-band data signals to device  12  using default communications mode  500 ), and power transmitting device  12  may being transmitting power to power receiving device  10  (step  610 ). 
     If handshaking is unsuccessful, power receiving device  10  may be reconfigured in another data communications mode (e.g., mode  502  or  504  of  FIG. 5 ). At step  606 , device  10  may reattempt to perform handshaking with power transmitting device  12  using the new communications mode. Processing may loop back to step  604 , as indicated by path  608 . If the handshaking is now successful between devices  10  and  12 , then the new data communications mode now modulates a capacitor with a value that is more suitable the current coupling coefficient that exists between devices  10  and  12 . 
     The steps of  FIG. 6  for detecting the coupling coefficient and for selecting the desired communications mode suitable for the detected/perceived coupling coefficient between devices  10  and  12  is merely illustrative and are not intended to limit the scope of the present embodiments. If desired, device  12  may directly or actively transmit this information to device  10  or may otherwise direct device  10  to select the correct switching capacitor, device  10  may have sensing or monitoring circuitry to measure the coupling coefficient or mutual inductance between the coils of devices  10  and  12 , or other suitable ways for determining the optimal data transmission mode may be implemented. 
     The example of  FIG. 4  in which wireless power receiving circuitry  46  includes at least capacitors C 1  and C 2  for supporting modes  500 ,  502 , and  504  of  FIG. 5  is merely illustrative and is not intended to limit the scope of the present embodiments. In accordance with another suitable embodiment,  FIG. 7  illustrates wireless power receiving circuitry  46  that is provided with a bank of individually selectable capacitors such as capacitive bank  450 . Components within wireless power receiving circuitry  46  marked with the same reference numerals as those already shown in  FIG. 4  have the same structure and function and need not be described again in detail in order to avoid obscuring the present embodiments. 
     As shown in  FIG. 7 , capacitor bank  450  is coupled to node  42  sitting between capacitor Crx and rectifier circuitry  80 . Bank  450  may include an array of capacitors C 1 , C 2 , C 3 , . . . , Cn, each of which can be individually switched into use. In general, “n” may represent any integer greater than or equal to two. A small number of capacitors in bank  450  provides coarse adjustment capability, whereas a large number of capacitors in bank  450  provides finer adjustment capability. Capacitor C 1  can be selectively activated by turning on a first switch using first control signal V 1 ; capacitor C 2  can be selectively activated by turning on a second switch using second control signal V 2 ; capacitor C 3  can be selectively activated by turning on a third switch using third control signal V 3 ; . . . ; and capacitor Cn can be selectively activated by turning on an n th  switch using control signal Vn. Control signals V 1 -Vn may be generated using control circuitry  20 . Control circuitry  20  can asserted one or more of control signals V 1 -Vn (e.g., any subset or even all of the n capacitors may be enabled). Bank  450  configured in this way is therefore sometimes referred to as a capacitor array. 
     In one suitable arrangement, the n capacitors in capacitive bank  450  may be scaled linearly. As an example, consider a scenario in which capacitive bank includes three capacitors: a first capacitor C 1  that exhibits a low capacitance suitable for a first mode of operation, a second capacitor C 2  that exhibits an intermediate capacitance suitable for a second mode of operation, and a third capacitor C 3  that exhibits a high capacitance suitable for a third mode of operation. In this example, a selected one of the three capacitors C 1 , C 2 , or C 3  may be enabled depending on the desired mode of operation. This example in which the capacitors in bank  450  are sized using a linear scale is merely illustrative. If desired, the n capacitors in bank  450  may be sized according to a binary scale, exponential scale, or may have suitable other weighting schemes optimized for certain modes of operation. 
     In general, controller  20  may selectively activate any number of capacitors in bank  450  to adjust the signal strength for data signals transmitted from inductor  14  to a corresponding wireless power transmitting device. The determination of which capacitors in bank  450  to activate may depend on the rectified voltage output from rectifier circuitry  80  (e.g., a full-bridge rectifier circuit or a half-bridge rectifier circuit), may depend on the output load  82 , and/or may depend on one or more system parameters received at control circuitry  20  at input  464 . 
     Control circuitry  20  may receive information about the rectified voltage generated by rectifier circuitry  80 , which is schematically represented by feedback path  460 . If the rectified voltage is low, control circuitry  20  may direct bank  450  to increase its overall capacitance. If the rectified voltage is high (i.e., if there is too much voltage rippling), control circuitry  20  may direct bank to decrease its overall capacitance. 
     Control circuitry  20  may also receive information about load  82 , which is schematically represented by feedback path  462 . If the load is small, control circuitry  20  may direct bank  450  to augment its overall capacitance to help increase the signal-to-noise ratio. If the load is large, control circuitry  20  may direct bank  450  to reduce its overall capacitance to help reduce the risk of excessive voltage rippling at the output. 
     Control circuitry  20  may also receive one or more system parameters associated with device  12  and/or device  10 . As an example, the received system parameter may indicate the transmitter type (i.e., the type of wireless power transmitting device  12  that is currently communicating with wireless power receiving circuitry  46 ). As another example, the received system parameter may indicate the type of communications protocol that is currently being used to support messaging between circuitry  46  and the corresponding transmitter device  12  (regardless of the coupling coefficient that is currently present between devices  10  and  12 ). For instance, a first communications protocol may operate at a first frequency and have a first bit error rate (BER) criteria, whereas a second communications protocol may operate at a second frequency and have a second BER criteria. 
     Regardless of the type of information that is received at control circuitry  20 , controller  20  may dynamically adjust bank  450  to ensure that adequate signal strength is maintained between device  10  and device  12  throughout the communications process. 
     The examples of  FIGS. 4 and 7  in which wireless power receiver circuitry  46  has a series LC tuning topology (i.e., inductor  14  and capacitor Crx connected in series as the resonant circuit) are merely illustrative. In general, the wireless power receiver circuitry  46  of  FIGS. 4 and 7  may be extended to support any receiver tuning architecture (see, e.g.,  FIGS. 8A-8D ).  FIG. 8A  shows an illustrative parallel LC tuning topology, where inductor  14  and capacitor Crx are coupled in parallel.  FIG. 8B  shows a first illustrative LCC tuning topology, where inductor  14  and capacitor Crx 1  are connected in series and where another capacitor Crx 2  is coupled in parallel with the series combination of inductor  14  and Crx 1 .  FIG. 8C  shows a second illustrative LCC tuning topology, where inductor  14  and capacitor Crx 1  are connected in parallel and where another capacitor Crx 2  is coupled in series with the parallel combination of inductor  14  and Crx 1 .  FIG. 8D  shows an illustrative LCL tuning topology, where inductor  14  and capacitor Crx are connected in parallel and where another inductor Lrx is coupled in series with the parallel combination of inductor  14  and Crx. If desired, other receiver tuning/resonant circuit topologies can also be implemented. 
     The example of  FIG. 7  where any number of capacitors within bank  450  can be activated provides improved flexibility to support communications with a wide variety of transmitter and protocol types while maintaining an adequate signal level during data communications. 
       FIG. 9  is a diagram showing various wireless in-band communications modes in which device  10  of the type shown in  FIG. 7  may be operated. As shown in  FIG. 9 , device  10  may be operated in a first data communications mode  900 . Mode  900  may be suitable for communicating with a first transmitter type or for supporting a first communications protocol. During mode  900 , a first group of capacitors in bank  450  may be activated (e.g., a first subset or portion of capacitors in the array can be turned on) to ensure that the signal strength is maintained at an acceptable level when wireless power receiving circuitry  46  is communicating with the first transmitter type or when supporting the first communications protocol. 
     Device  10  may also be operable in a second data communications mode  902 . Mode  902  may be suitable for communicating with a second transmitter type that is different than the first transmitter type or for supporting a second communications protocol that is different than the first communications protocol. During mode  902 , a second group of capacitors in bank  450  may be activated (e.g., a second subset or portion of capacitors that is different than the first subset in the array can be turned on) to ensure that the signal strength is maintained at an acceptable level when wireless power receiving circuitry  46  is communicating with the second transmitter type or when supporting the second communications protocol. 
     Device  10  may optionally be operable in one or more additional data communications mode(s)  904 . Mode  904  may be suitable for communicating with yet other transmitter types that are different than the first/second transmitter type or for supporting additional communications protocols that are different than the first/second communications protocol. During mode  904 , another group of capacitors in bank  450  may be activated (e.g., a third subset or portion of capacitors that is different than the first/second subset in the array can be turned on) to ensure that the signal strength is maintained at an acceptable level when wireless power receiving circuitry  46  is communicating with the other transmitter types or when supporting the additional communications protocols. 
       FIG. 10  is a flow chart of illustrative steps for operating wireless power receiving device  42  of the type shown in  FIG. 7 . A user may first bring a power receiving device  10  into proximity of a power transmitting device  12 . For example, the user may place device  10  on a charging surface of device  12  or may otherwise attach or mount device  10  onto device  12 . 
     At step  1000 , power transmitting device  12  may detect the power receiving device  10  and may attempt to perform handshaking with power receiving device  10 . During handshaking operations, transmitting device  12  may transmit an outgoing packet that includes transmitter type information (e.g., control data indicative of the type of device  12 ) and/or required communications protocol information (e.g., control data reflective of the required data rate, BER, or other signaling criteria). Other exemplary handshaking operations that may be performed at this time may include device authentication, negotiation of appropriate power transmission levels, etc. 
     At step  1002 , power receiving device  10  may receive the packet transmitted from device  12  and may decode the received packet to identify the transmitter type and/or the required protocol. In response to determining the transmitter type and/or the requisite protocol, receiving device  10  may place wireless receiving circuitry  46  in a selected one of the available communications mode (see, e.g., the various modes of  FIG. 9 ) by switching into use one or more capacitors in the capacitive array  450  (at step  1004 ). The selection of which capacitors in the array to enable may also be based on rectified voltage level at the output of rectifier circuitry  80  and/or the size of output load  82  (see  FIG. 7 ). 
     Once the selected capacitors have been activated, device  10  may communicate properly with device  12  while maintaining sufficient signal strength. While devices  10  and  12  exchange data, operating conditions could potentially change. If so, controller  20  may optionally reconfigure the capacitive bank  450  as necessary to optimize data communications between devices  10  and  12  (step  1006 ). 
     The embodiments described in connection with  FIGS. 7, 9, and 10  having an adjustable capacitive bank  450  for providing reactance (or imaginary impedance) modulation is merely illustrative and are not intended to limit the scope of the present embodiments. In accordance with another suitable embodiment, wireless power receiving circuitry  46  may instead be modulated using an adjustable resistive bank such resistive bank  451  of  FIG. 11 . A resistive bank  451  may be configured to provide resistive (or real impedance) modulation at circuitry  46 . As shown in  FIG. 11 , resistive bank  451  may include an array of resistors R 1 , R 2 , R 3 , . . . , Rm, each of which can be individually switched into use. In general, “m” may represent any integer greater than or equal to two. A small number of resistors within bank  451  provides coarse adjustment capability, whereas a large number of resistors within bank  451  provides finer adjustment capability. 
     Resistor R 1  can be selectively activated by turning on a first switch using first control signal V 1 ; resistor R 2  can be selectively activated by turning on a second switch using second control signal V 2 ; resistor R 3  can be selectively activated by turning on a third switch using third control signal V 3 ; . . . ; and resistor Rm can be selectively activated by turning on an n th  switch using control signal Vn. Control signals V 1 -Vn may be generated using control circuitry  20  (see  FIG. 7 ). Control circuitry  20  can asserted one or more of control signals V 1 -Vn (e.g., any subset or even all of the m resistors may be enabled). Bank  450  configured in this way is therefore sometimes referred to as a resistive array. Similar to the capacitive example, the m resistors in bank  451  may be sized according to a linear scale, binary scale, exponential scale, or may have suitable other weighting schemes optimized for certain modes of operation. 
     In general, controller  20  may selectively activate any number of resistors in bank  451  to adjust the signal strength for data signals transmitted from inductor  14  to a corresponding wireless power transmitting device. The determination of which resistors in bank  451  to activate may depend on the rectified voltage output from rectifier circuitry  80  (e.g., a full-bridge rectifier circuit or a half-bridge rectifier circuit), may depend on the size of output load  82 , and/or may depend on one or more system parameters described above. 
     If desired, resistive bank  451  may also be coupled to the rectified DC voltage rail after rectifier circuitry  80  (e.g., at node  81  in  FIG. 7 ). Coupling resistive bank  451  to node  81  can help reduce power loss for the receiver tuning components. Connecting bank  451  to node  81  effectively mimics an adjustable load at node  402  (i.e., bank  451  connected at node  81  can still provide load impedance modulation from the perspective of the receiver&#39;s resonant network, when viewed in the direction of arrows  490  in  FIG. 7 ). 
     The example of  FIG. 11  in which a purely resistive bank  451  is coupled to node  402  is also merely illustrative. In general, any type of adjustable load bank that include real and/or imaginary impedance components may be coupled to node  402  (see, e.g.,  FIG. 12 ).  FIG. 12  shows a generic adjustable load bank  452  that may be provided as part of power receiving circuitry  46 . As shown in  FIG. 12 , load bank  451  may include both capacitors C 1 -Cn and resistors R 1 -Rm. Integers “n” and “m” may have the same value or different values. Control circuitry  20  may activate only capacitors (e.g., by switching into use one or more of capacitors C 1 -Cn), may activate only resistors (e.g., by switching into use one or more of resistors R 1 -Rm), or may activate both capacitors and resistors (e.g., by switching into use at least some of capacitors C 1 -Cn and at least some of resistors R 1 -Rm in parallel). Simultaneous activation of both capacitors and resistors in bank  452  is proper so long as the real impedance modulation provided by the activated resistors does not cancel out the imaginary impedance modulation provided by the activated capacitors. The determination of which capacitors and/or resistors in bank  452  to activate may depend on the rectified voltage output from rectifier circuitry  80  (e.g., a full-bridge rectifier circuit or a half-bridge rectifier circuit), may depend on the size of output load  82 , and/or may depend on one or more system parameters described above. 
     If desired, bank  452  may further include other types of passive electrical components (e.g., any combination and number of capacitive, resistance, and/or inductive elements connected in a parallel and/or series configuration) for modulating the impedance at node  402 . In yet other suitable embodiments, bank  452  may include constant current loads or ballast loads. Similar to bank  451 , adjustable load bank  452  may also be coupled to the rectified DC voltage rail after rectifier circuitry  80  (e.g., at node  81  in  FIG. 7 ). Coupling resistive bank  452  to node  81  can help reduce power loss for the receiver resonant network. Connecting bank  452  to node  81  effectively mimics an adjustable load at node  402  (i.e., bank  452  connected at node  81  can still provide the desired impedance modulation from the perspective of the receiver&#39;s resonant network, when viewed in the direction of arrows  490  in  FIG. 7 ). 
     The foregoing describes a technology that enables robust data transmission in the context of wireless power transfer. The present disclosure contemplates that it may be desirable for a power transmitter and a power receiver device to communicate information such as states of charge, charging speeds, so forth, to control wireless power transfer between devices. 
     It is possible, however, to transfer other kinds of data, such as data that are more personal in nature. Entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. Such policies should be easily accessible by users and should be updated as the collection and/or use of data changes. Personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection/sharing should occur after receiving the informed consent of the users. Additionally, such entities should consider taking any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. In addition, policies and practices should be adapted for the particular types of personal information data being collected and/or accessed and adapted to applicable laws and standards, including jurisdiction-specific considerations. For instance, in the US, collection of or access to certain health data may be governed by federal and/or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); whereas health data in other countries may be subject to other regulations and policies and should be handled accordingly. Hence different privacy practices should be maintained for different personal data types in each country. 
     To the extent that the present technology is leveraged to transmit personal information data, hardware and/or software elements can be provided for users to selectively block the use of, or access to, personal information data. For example, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the collection of personal information data during registration for services or anytime thereafter. In addition to providing “opt in” and “opt out” options, the present disclosure contemplates providing notifications relating to the access or use of personal information. For instance, a user may be notified upon downloading an app that their personal information data will be accessed and then reminded again just before personal information data is accessed by the app. 
     It is the intent of the present disclosure to describe a robust system for data transmission in a wireless power system. In implementations of this technology were personal information data is transmitted, that personal information data should be managed and handled in a way to minimize risks of unintentional or unauthorized access or use. Risk can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, data de-identification can be used to protect a user&#39;s privacy. De-identification may be facilitated, when appropriate, by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of data stored (e.g., collecting location data a city level rather than at an address level), controlling how data is stored (e.g., aggregating data across users), and/or other methods. 
     The foregoing is illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20181120
Publication Date: 20201020
Grant Date: 20201020
Priority Date: 20180806
Inventors: QIU, WEIHONG
LIU, NAN
BERDNIKOV, DMITRY
MOUSSAOUI, ZAKI
HUANG, Rex
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/263", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/263", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/263", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/126", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M7/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M7/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/126", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/126", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/0037", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69229786