PATENT DOCUMENT

Publication Number: US-11070088-B2
Application Number: US-201816213915-A
Country: US
Kind Code: B2

Title: Wireless power transfer

Abstract:
An inductive power transmitter and an inductive power receiver include communication circuitry to communicate using modulation of the power transfer field. The inductive power transmitter or the inductive power receiver includes monitoring circuitry to determine a communication fault condition. If a communication fault condition is determined, a converter of the inductive power transmitter or inductive power receiver can adjust a control parameter.

Claims:
What is claimed is: 
     
       1. An inductive power transmitter comprising:
 a power transmitting coil configured to produce an inductive power transfer field; 
 communication circuitry configured to communicate with an inductive power receiver using modulation of the inductive power transfer field; 
 monitoring circuitry operatively connected to the communication circuitry and configured to determine a communication fault condition that includes one or more of a corrupt, unreadable, incomplete, invalid, or missing communication; and 
 a converter configured to provide an alternating current voltage to the power transmitting coil and adjust a control parameter upon a determination of a communication fault condition, wherein the converter is configured to adjust an additional control parameter if the communication fault condition is not removed after adjustment of the control parameter. 
 
     
     
       2. An inductive power transmitter according to  claim 1 , wherein the converter is configured to progressively adjust the control parameter upon determination of the communication fault condition until the communication fault condition is removed. 
     
     
       3. An inductive power transmitter according to  claim 2 , wherein after the communication fault condition is removed the control parameter is kept at the last adjusted state or returned to the pre adjustment state. 
     
     
       4. An inductive power transmitter according to  claim 1 , wherein the control parameter is a characteristic of the alternating current voltage provided to the power transmitting coil. 
     
     
       5. An inductive power transmitter according to  claim 4 , wherein the control parameter is amplitude, duty cycle, phase delay or frequency of the alternating current voltage provided to the power transmitting coil. 
     
     
       6. An inductive power transmitter according to  claim 5 , wherein the converter is configured to progressively increase the amplitude, duty cycle, phase delay or frequency of the alternating current voltage provided to the power transmitting coil. 
     
     
       7. An inductive power transmitter according to  claim 1 , wherein the communication circuitry is configured to receive amplitude shift keying signals from the inductive power receiver. 
     
     
       8. An inductive power transmitter according to  claim 7 , wherein the communication circuitry is configured to transmit frequency shift keying or amplitude shift keying signals to the inductive power receiver. 
     
     
       9. An inductive power transmitter according to  claim 1 , wherein the converter includes a DC-DC converter and an inverter. 
     
     
       10. An inductive power transmitter according to  claim 9 , wherein the control parameter is a phase shift between switches of the inverter. 
     
     
       11. An inductive power transmitter according to  claim 1 , wherein:
 the converter includes a DC-DC converter and an inverter; 
 the control parameter is a phase shift between switches of the inverter; and 
 the additional control parameter is output voltage level of the DC-DC converter. 
 
     
     
       12. An inductive power transmitter according to  claim 11 , wherein the converter is configured to increase the phase shift between switches of the inverter until an adjustment limit is reached and increase the output voltage level of the DC-DC converter if the adjustment limit of the switches is reached. 
     
     
       13. An inductive power receiver comprising:
 a power receiving coil configured to couple to an inductive power transfer field; 
 communication circuitry configured to communicate with an inductive power transmitter using modulation of the inductive power transfer field; 
 monitoring circuitry operatively connected to the communication circuitry and configured to determine a communication fault condition that includes one or more of a corrupt, unreadable, incomplete, invalid, or missing communication; and 
 a converter configured to receive an alternating current voltage from the power receiving coil and adjust a control parameter upon a determination of a communication fault condition, wherein the converter is configured to adjust a second control parameter if the communication fault condition is not removed after adjustment of the control parameter. 
 
     
     
       14. An inductive power receiver according to  claim 13 , wherein the converter is configured to progressively adjust the control parameter upon determination of the communication fault condition until the communication fault condition is removed. 
     
     
       15. An inductive power receiver according to  claim 13 , wherein the control parameter is a characteristic of a voltage output by the converter. 
     
     
       16. An inductive power receiver according to  claim 15 , wherein the control parameter is amplitude of the voltage output by the converter. 
     
     
       17. An inductive power receiver according to  claim 16 , wherein the converter is configured to increase the amplitude of the voltage output by the converter upon determination of a communication fault condition. 
     
     
       18. An inductive power receiver according to  claim 13 , wherein the converter includes a regulator and/or a rectifier. 
     
     
       19. An inductive power receiver according to  claim 13 , wherein the communication circuitry is configured to receive frequency shift keying or amplitude shift keying signals from an inductive power transmitter. 
     
     
       20. An inductive power receiver according to  claim 13 , wherein the communication circuitry is configured to transmit amplitude shift keying signals to the transmitter. 
     
     
       21. A method comprising:
 producing an inductive power transfer field using an inductive power transmitter; 
 coupling to the inductive power transfer field using an inductive power receiver; 
 modulating the inductive power transfer field to attempt to communicate between an inductive power transmitter and an inductive power receiver; 
 determining if a communication fault condition exists with the modulated field, wherein the communication fault condition includes one or more of a corrupt, unreadable, incomplete, invalid, or missing communication; 
 adjusting a control parameter of the transmitter or the inductive power receiver upon determination of the communication fault condition; and 
 adjusting a second control parameter if the communication fault condition is not removed after adjustment of the control parameter. 
 
     
     
       22. An inductive power transmitter comprising:
 a power transmitting coil configured to produce an inductive power transfer field; 
 communication circuitry configured to communicate with an inductive power receiver using modulation of the inductive power transfer field, wherein the communication circuitry is configured to receive amplitude shift keying signals from the inductive power receiver; 
 monitoring circuitry operatively connected to the communication circuitry and configured to determine a communication fault condition that includes one or more of a corrupt, unreadable, incomplete, invalid, or missing communication; and 
 a converter configured to provide an alternating current voltage to the power transmitting coil and adjust a control parameter upon a determination of a communication fault condition. 
 
     
     
       23. An inductive power transmitter according to  claim 22 , wherein the converter is configured to progressively adjust the control parameter upon determination of the communication fault condition until the communication fault condition is removed. 
     
     
       24. An inductive power transmitter according to  claim 23 , wherein after the communication fault condition is removed the control parameter is kept at the last adjusted state or returned to the pre adjustment state. 
     
     
       25. An inductive power transmitter according to  claim 22 , wherein the control parameter is a characteristic of the alternating current voltage provided to the power transmitting coil. 
     
     
       26. An inductive power transmitter according to  claim 25 , wherein the control parameter is amplitude, duty cycle, phase delay or frequency of the alternating current voltage provided to the power transmitting coil. 
     
     
       27. An inductive power transmitter according to  claim 26 , wherein the converter is configured to progressively increase the amplitude, duty cycle, phase delay or frequency of the alternating current voltage provided to the power transmitting coil. 
     
     
       28. An inductive power transmitter according to  claim 22 , wherein the communication circuitry is configured to transmit frequency shift keying or amplitude shift keying signals to the inductive power receiver. 
     
     
       29. An inductive power transmitter according to  claim 22 , wherein the converter includes a DC-DC converter and an inverter. 
     
     
       30. An inductive power transmitter according to  claim 29 , wherein the control parameter is a phase shift between switches of the inverter. 
     
     
       31. An inductive power transmitter according to  claim 22 , wherein:
 the converter includes a DC-DC converter and an inverter; 
 the control parameter is a phase shift between switches of the inverter; and 
 the additional control parameter is output voltage level of the DC-DC converter. 
 
     
     
       32. An inductive power transmitter according to  claim 31 , wherein the converter is configured to increase the phase shift between switches of the inverter until an adjustment limit is reached and increase the output voltage level of the DC-DC converter if the adjustment limit of the switches is reached. 
     
     
       33. An inductive power receiver comprising:
 a power receiving coil configured to couple to an inductive power transfer field; 
 communication circuitry configured to communicate with an inductive power transmitter using modulation of the inductive power transfer field including at least one of:
 transmitting amplitude shift keying signals to the inductive power transmitter, 
 receiving frequency shift keying signals from the inductive power transmitter, and 
 receiving amplitude shift keying signals from the inductive power transmitter; 
 
 monitoring circuitry operatively connected to the communication circuitry and configured to determine a communication fault condition that includes one or more of a corrupt, unreadable, incomplete, invalid, or missing communication; and 
 a converter configured to receive an alternating current voltage from the power receiving coil and adjust a control parameter upon a determination of a communication fault condition. 
 
     
     
       34. An inductive power receiver according to  claim 33 , wherein the converter is configured to progressively adjust the control parameter upon determination of the communication fault condition until the communication fault condition is removed. 
     
     
       35. An inductive power receiver according to  claim 33 , wherein the control parameter is a characteristic of a voltage output by the converter. 
     
     
       36. An inductive power receiver according to  claim 35 , wherein the control parameter is amplitude of the voltage output by the converter. 
     
     
       37. An inductive power receiver according to  claim 36 , wherein the converter is configured to increase the amplitude of the voltage output by the converter upon determination of a communication fault condition. 
     
     
       38. An inductive power receiver according to  claim 33 , wherein the converter includes a regulator or a rectifier.

Description:
FIELD 
     This relates generally to wireless power transfer systems. 
     BACKGROUND 
     In a wireless charging system, a wireless power transmitting device such as a device with a charging surface or zone wirelessly transmits power to 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. 
     SUMMARY 
     In some situations, achieving reliable in-band communications between inductive power transmitters and receivers can be difficult. Transient events during communications can cause data transmissions to not be modulated, transmitted or demodulated correctly. Communication failures can also occur when the operating state of the power transmission system is unsuitable for communications. While the power transmission is in an unsuitable operating state, communications may continue to fail. 
     Failed communications may interfere with or prevent dynamic control of the power transfer system, which may employ feedback or other communications to adapt power transfer parameters based on information reported from one device to another. When a communication failure persists, the communication interface between the transmitter and receiver may be reset. An attempt may then be made to re-establish communications. This may be time consuming and increase the amount of time taken to charge a receiver device. It also may be ineffective if the power transmission remains in the unsuitable operating state after the communications interface is reset. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system in accordance with some embodiments. 
         FIG. 2  is a schematic diagram of an illustrative inductive power transmitter in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of an illustrative inductive power transmitter in accordance with another embodiment. 
         FIG. 4  is a schematic diagram of an illustrative inductive power receiver in accordance with an embodiment. 
         FIG. 5  is a schematic diagram of an illustrative inductive power receiver in accordance with another embodiment. 
         FIG. 6  is a flow chart of an illustrative method in accordance with an embodiment. 
         FIG. 7  is a flow chart of an illustrative method in accordance with another 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 is a device such as a wireless charging mat, wireless charging puck, wireless charging stand, wireless charging table, or other wireless power transmitting equipment. The wireless power transmitting device may be a stand-alone device or built into other electronic devices such as a laptop or tablet computer, cellular telephone or other electronic 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. The wireless power receiving device is a device such as a cellular telephone, watch, media player, tablet computer, pair of earbuds, remote control, laptop computer, electronic pencil or stylus, other portable electronic device, or other wireless power receiving equipment. 
     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. 
     Wireless power transmitting and receiving devices can be designed to cooperate specifically with each other. For example, the size, shape, number, dimensions and configuration of coils of one or both of the devices may be selected based on the other device. Magnetic elements may also be included in the transmitting and/or receiving device, and the size, shape, number, dimensions and configuration of the magnetic elements may be selected based on the other device. 
     In some cases, wireless power transmitting and receiving devices can be designed to be closely coupled to each other. This may be achieved by arranging the coils of the transmitting and receiving devices such that they are aligned with and close to each other in use. Systems in which the transmitting and receiving devices can be closely coupled to each other in use are sometimes referred to as inductive power transfer systems. Transmitting and receiving devices that can be closely coupled to receiving devices can be referred to as inductive power transfer devices. 
     Wireless power transmitting and receiving devices and transmitters can also be designed to communicate with each other using the power transfer field or using a separate communication channel. These communications can be used to authenticate devices, negotiate power transfer parameters, and as a feedback mechanism to request higher or lower power during charging, for example. Communication through the wireless power transfer field may be referred to as “in-band” communication. In in-band communication systems, devices modulate the power transfer field to encode information and demodulate the field to decode information. There are various parameters of the power transfer field that can be modulated to communicate information, such as amplitude, frequency and phase. There are various ways in which each of these parameters could be modulated, including various analog and digital encoding schemes. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , a wireless power system  8  includes a wireless power transmitting device  12  and one or more wireless power receiving devices such as wireless power receiving device  10 . Device  12  may be a stand-alone device such as a wireless charging mat, may be built into furniture, laptop or tablet computers, cellular telephones or other electronic devices, or may be other wireless charging equipment. Device  10  is a portable electronic device such as a wristwatch, a cellular telephone, a tablet computer, an electronic pencil or stylus, or other electronic equipment. Illustrative configurations in which device  12  is a tablet computer or similar electronic device and in which device  10  is an electronic accessory that couples with the tablet computer or similar electronic device during wireless power transfer operations may sometimes be described herein as examples. Illustrative configurations in which device  12  is a mat or other equipment that forms a wireless charging surface and in which device  10  is a portable electronic device or electronic accessory that rests on the wireless charging surface during wireless power transfer operations may also sometimes be described herein as examples. 
     During operation of system  8 , a user places one or more devices  10  on or near the charging region of device  12 . Power transmitting device  12  is coupled to a source of alternating-current voltage such as alternating-current power source  50  (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  may be included to convert power from a mains 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 . 
     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 switching circuitry, a time varying electromagnetic field (wireless power signals  48 ) is produced, that is received by one or more corresponding coils  14  electrically connected to wireless power receiving circuitry  46  in receiving device  10 . If the time varying electromagnetic field is magnetically coupled to coil  14 , an AC voltage is induced and a corresponding AC currents flows in coil  14 . Rectifier circuitry in circuitry  46  can convert the induced AC voltage in the one or more coils  14  into a DC voltage signals for powering device  10 . The DC voltages are used in powering components in device  10  such as display  52 , touch sensor components and other sensors  54  (e.g., accelerometers, force sensors, temperature sensors, light sensors, pressure sensors, gas sensors, moisture sensors, magnetic sensors, etc.), wireless communications circuits  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/or are used in charging an internal battery in device  10  such as battery  18 , or to charge subsequent devices, either wired or wirelessly. 
     Devices  12  and  10  include control circuitry  42  and  20 . Control circuitry  42  and  20  may include storage and processing circuitry such as analogue circuitry, microprocessors, power management units, baseband processors, digital signal processors, field-programmable gate arrays, microcontrollers, application-specific integrated circuits with processing circuits and/or any combination thereof. 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. 
     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 circuits  56  of  FIG. 1 ) 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.). For example device  12  and/or device  10  may communicate using in-band communications injected or combined into the wireless power signals  48  in accordance with any suitable scheme, for example as proposed in the Wireless Power Consortium Qi specification 1.1, which is incorporated herein by reference. In addition to the in-band communications system, a separate Bluetooth®, RFID, NFC, Zigbee, Wifi RF or other communication system may be employed. 
     An illustrative inductive power transmitter  100  is shown in  FIG. 2 . The transmitter  100  includes a power transmitting coil  110 , communication circuitry  120 , monitoring circuitry  130  and a converter  140 . 
     Various types of power transmitting coils may be used in the transmitter  100  to produce the inductive power field. For example, the transmitting coil  110  may be planar or elongate depending on the application. The coil may also be provided with a magnetic core to guide and focus the magnetic field produced by the coil. 
     The transmitter  100  may have a plurality of power transmitting coils that may be connected in parallel or series or energized independently. For example, the transmitter  100  may be a charging mat with an array of transmitter coils configured to provide inductive power signals to one or more receivers placed on a charging surface of the mat. 
     In some examples, the transmitter  100  may have two or more coils wound about respective limbs of a magnetic core to form a coil assembly. 
     It will be appreciated that the coil or coils may be wound from a single-strand conductor, a multiple strand conductor having multiple wires connected in parallel, braided wire, Litz wire, a conductive ink or conductive trace such as multilayer tracks on a printed circuit board, or other conductive elements suitable for forming coils. 
     The power transmitting coil  110  may be electrically connected to or more capacitances to form a resonant circuit. The transmitting coil may be connected to the capacitance(s) in series, parallel or a combination of series and parallel connections. In one example, the power transmitting coil  110  is connected to a tuning capacitor in series to form a series-tuned resonant circuit. 
     The communication circuitry  120  enables the transmitter  100  to communicate with other devices coupled to the power transfer field such as inductive power receivers. The communication circuitry  120  performs in-band communication using modulation of the inductive power transfer field produced using the power transmitting coil(s)  110 . Various types of in-band communication circuitry  120  may be employed in the transmitter  100 . For example, the transmitter communication circuitry  120  may use amplitude modulation, frequency modulation, phase modulation, or a combination of these. The communication circuitry  120  may transmit signals of one modulation type and receive and demodulate signals of the same modulation type or a different modulation type. In one example, the transmitter communication circuitry  120  is configured to transmit frequency-shift keying (FSK) signals or amplitude-shift keying (ASK) signals. In one example, the transmitter communication circuitry  120  is configured to receive amplitude-shift keying (ASK) signals. The communication circuit may communicate using packets or a continuous bit stream. In one example, the communication circuit transmits and receives packets. The packets may include at least a header and a payload. 
     The monitoring circuitry  130  is operatively connected to the communication circuitry  120  and configured to determine a communication fault condition. The monitoring circuitry  130  may be implemented using hardware components, software components or a combination of hardware and software. There are various ways the monitoring circuit may determine a communication fault condition. For example, if a communication is received that is corrupt, unreadable, incomplete or otherwise invalid, this may be taken as an indication of a fault condition. If the transmitter  100  transmits a message, to which it expects a response, the absence of a response within some timeframe (i.e. a “missed” packet) may be taken as an indication of a fault condition. The monitoring circuitry  130  may determine a communication fault condition based on physical parameters of a received signal being outside of a range. For example, in an ASK system if the difference between high and low voltages that correspond to binary bits is less than a predetermined or dynamic value, this may indicate a communication fault condition. In another example, if a signal to noise ratio (SNR) or received signal strength indicator (RSSI) related to the communication channel is below a predetermined to dynamic value, this may indicate a communication fault condition. In a system that uses acknowledgements (or non-acknowledgements) of receipt of messages, these could be used to determine a communication fault condition. For example, if the communication circuitry  120  does not receive an expected acknowledgement, or does receive a non-acknowledgement, this may indicate a communication fault condition. The acknowledgements and non-acknowledgements may be ACK and NACK packets, in one example. In some examples, the monitoring circuitry  130  may determine a communication fault condition based on current system parameters such as transmitter-receiver coupling coefficient, received voltage at the receiver, power drawn by a load of receiver etc. One or more of these parameters may be compared to a look-up table or input to a formula to determine whether the current system operating state is likely to be unsuitable for communications. The look-up table or formula in this case may be produced from empirical data of communication quality for different operating states or from a mathematical model of a power transfer system and its behavior in different operating states. In one example, the monitoring circuit will determine a communication fault based on a missed or corrupt packet. 
     Various conditions of the operating state may lead to poor communications quality. In some cases, low voltage received at the receiver may correlate with poor communications conditions. This may be measured at the output of a rectifier of the receiver. In some cases, low coupling coefficient between the transmitter and receiver may correlate with poor communications condition. Of course, many other situations may lead to poor communications quality, including combinations of conditions like received voltage, coupling coefficient, and other variables. The adjustment of the control parameter(s) may address the poor communications conditions by altering one or more of these conditions. 
     The transmitter  100  includes a converter  140  to provide an alternating current (AC) voltage to the transmitting coil  110 . This drives the coil to produce the power transfer field. The converter  140  is configured to adjust a control parameter upon determination of a communication fault condition. By adjusting a control parameter, the converter  140  may remove or alleviate the communication fault condition. This may be particularly useful when the communication fault condition is a non-transitory one based on the operating parameters of the power transfer system. Adjusting the control parameter may shift the operating parameters from a state which is unsuitable for communications to a state that is suitable for communications. 
     The converter  140  may include one or more DC-DC converters, AC-DC converters (rectifiers), AC-AC converters, DC-AC converters (inverters), transformers, regulators or the like. Suitable DC-DC converters include buck converters, boost converters, buck-boost converters and flyback converters. Suitable AC-DC converters include diode bridge rectifiers, synchronous rectifiers and voltage multipliers. Suitable DC-AC converters include push-pull inverters and full-bridge inverters. In one example, the converter includes a DC-DC boost converter. In one example, the converter  140  includes a full-bridge inverter. 
     There are many converter control parameters that may affect the operating state of the power transfer system. Adjusting any of these may improve the operating state with respect to its suitability for communication. 
     The control parameters may be power transfer parameters. The power transfer parameters may be any parameters of the power transfer link between the power supply to the transmitter  100  and the receiver load. The control parameter may be, or may affect, level of power provided to the transmitting coil  110 . The control parameters may be characteristics of a voltage provided to the transmitting coil  110 . For example, the converter  140  may adjust the amplitude, duty cycle, phase delay and/or frequency of the voltage provided to the transmitting coil  110 . 
     The converter  140  may adjust the amplitude of the voltage provided to the transmitting coil  110  by adjusting the output of an AC-AC converter, a DC-DC converter or an AC-DC converter. In one example, the amplitude of AC voltage output by the inverter to the coil depends on the level of the DC voltage provided to the inverter such that increasing the output of the DC-DC converter may increase the amplitude of the AC voltage provided to the coil by the inverter, and vice-versa. In one example, the converter  140  includes a boost converter and the converter  140  is configured to adjust the output voltage of the boost converter. 
     The converter  140  may adjust the voltage provided to the transmitting coil  110  by adjusting operation of an inverter. In one example, the inverter is a full-bridge inverter with phase shift control such that voltage provided to the transmitting coil  110  depends on the phase shift between switches of the inverter bridge. For example, the inverter may be in the form of a full H-bridge with power being supplied to the transmitting coil  110  via switches in each limb of the H bridge. Switches on the same side of the transmitting coil  110  may be switched complementarily with each other such that when one switch is off, the other is on. The phase between the switches on one side of the transmitting coil  110  and the switches on the other side of the transmitting coil  110  may be controlled to control the voltage provided to the transmitting coil  110 . With a 180° phase shift between switches on one side of the coil  110  and switches on the other side of the coil  110 , diagonally opposite switches are switched on and off at the same time. When the phase shift is less than 180°, diagonally opposite switches will be in opposite states for some portion of the cycle and either of the “upper” pair or “lower” pair of switches will be simultaneously on for that portion of the cycle, meaning the two side of the coil  110  are at approximately the same potential for this portion. In this example, maximum duty cycle may be obtained at 180° phase shift. The duty cycle may be increased as the phase shift is adjusted towards 180° and vice versa. 
     The converter  140  may adjust the frequency of the voltage provided to the transmitting coil  110  by adjusting the frequency of voltage output by the inverter. In one example, the inverter is a full-bridge inverter and the frequency output by the inverter may be adjusted by adjusting the frequency of switching of switches of the inverter. 
     It will be appreciated that the transmitter  100  may include control circuitry such as analogue circuitry, one or more microprocessors, baseband processors, digital signal processors, field-programmable gate arrays, microcontrollers, and/or application-specific integrated circuits with processing circuits. The control circuitry may be used in performing communication, monitoring and determination of a fault condition and control of the converter  140  such that it forms at least part of one or more of the communication circuitry  120 , monitoring circuitry  130  and converter  140 . 
     An illustrative inductive power transmitter  100  is shown in  FIG. 3  in accordance with one embodiment. In this example, the transmitter  100  is provided with one or more power transmitting coil(s)  110 , communication circuitry  120 , monitoring circuitry  130 , a converter  140 , and control circuitry  150 . The communication circuitry in the example includes an FSK modulator  122 . The communication circuitry in this example includes an ASK modulator and/or an ASK demodulator  124 . The converter in this example includes a boost converter  142  and a full-bridge inverter  144 . 
     An illustrative inductive power receiver  200  is shown in  FIG. 4 . The receiver  200  includes a power receiving coil  210 , communication circuitry  220 , monitoring circuitry  230  and a converter  240 . 
     Various types of power receiving coils may be used in the receiver  200  to couple to the inductive power field. For example, the receiver coil may be planar or elongate depending on the application. The coil may also be provided with a magnetic core to guide and focus the magnetic field to which the coil may couple. 
     The receiver  200  may have a plurality of power receiving coils that may be connected in parallel or series or energized independently. In some examples, the receiver  200  may have two or more coils wound about respective limbs of a magnetic core to form a coil assembly. 
     It will be appreciated that the coil or coils may be wound from a single-strand conductor, a multiple strand conductor having multiple wires connected in parallel, braided wire, Litz wire, a conductive ink or conductive trace such as multilayer tracks on a printed circuit board, or other conductive elements suitable for forming coils. 
     The power receiving coil  210  may be electrically connected to or more capacitances to form a resonant circuit. The receiving coil may be connected to the capacitance(s) in series, parallel or a combination of series and parallel connections. In one example, the power receiving coil  210  is connected to a tuning capacitor in series to form a series-tuned resonant circuit. 
     The communication circuitry  220  enables the receiver  200  to communicate with other devices coupled to the power transfer field such as inductive power transmitters. The communication circuitry  220  communicates using modulation of the inductive power transfer field coupled to by the power receiving coil(s)  210 . Various types of in-band communication circuitry  220  may be employed in the receiver  200 . For example, the receiver communication circuitry  220  may use amplitude modulation, frequency modulation, phase modulation, or a combination of these. The communication circuitry  220  may transmit signals of one modulation type and receive and demodulate signals of the same modulation type or a different modulation type. In one example, the receiver communication circuitry  220  is configured to transmit amplitude-shift keying (ASK) signals. In one example, the receiver communication circuitry  220  is configured to receive amplitude-shift keying (ASK) signals or frequency-shift keying (FSK) signals. The communication circuit may communicate using packets or a continuous bit stream. In one example, the communication circuit transmits and receives packets. The packets may include at least a header and a payload. 
     The monitoring circuitry  230  is operatively connected to the communication circuitry  220  and configured to determine a communication fault condition. The monitoring circuitry  230  may be implemented using hardware components, software components or a combination of hardware and software. There are various ways the monitoring circuit may determine a communication fault condition. For example, if a communication is received that is corrupt, unreadable, incomplete or otherwise invalid, this may be taken as an indication of a fault condition. If the receiver  200  transmits a message, to which it expects a response, the absence of a response within some timeframe (i.e. a “missed” packet) may be taken as an indication of a fault condition. The monitoring circuitry  230  may determine a communication fault condition based on physical parameters of a received signal being outside of a range. For example, in an ASK system if the difference between high and low voltages that correspond to binary bits is less than a predetermined or dynamic value, this may indicate a communication fault condition. In another example, if a signal to noise ratio (SNR) or received signal strength indicator (RSSI) related to the communication channel is below a predetermined or dynamic value, this may indicate a communication fault condition. In a system that uses acknowledgements (or non-acknowledgements) of receipt of messages, these could be used to determine a communication fault condition. For example, if the communication circuitry  220  does not receive an expected acknowledgement, or does receive a non-acknowledgement, this may indicate a communication fault condition. The acknowledgements and non-acknowledgements may be ACK and NACK packets, in one example. In some examples, the monitoring circuitry  230  may determine a communication fault condition based on current system parameters such as transmitter-receiver coupling coefficient, received voltage at the receiver  200 , power drawn by a load of the receiver  200  etc. One or more of these parameters could be compared to a look-up table or input to a formula to determine whether the current system operating state is likely to be unsuitable for communications. The look-up table or formula in this case may be produced from empirical data of communication quality for different operating states or from a mathematical model of a power transfer system and its behavior in different operating states. In one example, the monitoring circuit will determine a communication fault based on a missed or corrupt packet. 
     The receiver  200  includes a converter  240  to convert an alternating current (AC) voltage received using the receiving coil  210  into a form suitable to be provided to a load. The converter  240  is configured to adjust a control parameter upon determination of a communication fault condition. By adjusting a control parameter, the converter  240  may remove or alleviate the communication fault condition. This may be particularly useful when the communication fault condition is a non-transitory one based on the operating parameters of the power transfer system. Adjusting the control parameter may shift the operating parameters from a state which is unsuitable for communications to a state that is suitable for communications. 
     The converter  240  may include one or more DC-DC converters, AC-DC converters (rectifiers), AC-AC converters, DC-AC converters (inverters), transformers, regulators or the like. Suitable DC-DC converters include buck converters, boost converters, buck-boost converters and flyback converters. Suitable AC-DC converters include diode bridge rectifiers, synchronous rectifiers and voltage multipliers. In one example, the converter  240  includes a DC-DC buck converter. In one example, the converter  240  includes a full-bridge synchronous rectifier. 
     There are many converter control parameters that may affect the operating state of the power transfer system. Adjusting any of these may improve the operating state with respect to its suitability for communication. 
     The control parameters may be power transfer parameters. The power transfer parameters may be any parameters of the power transfer link between the power supply to the transmitter  100  and the receiver load. The control parameters may include characteristics of a voltage produced by the converter  240 . For example, the converter  240  may be configured to adjust the amplitude of voltage produced by the converter  240 . In one example, the converter  240  includes a DC-DC buck converter that is configured to adjust the amplitude of voltage provided to the load. In one example, the converter  240  includes a synchronous rectifier that may be configured to control the rectified voltage at the output of the rectifier. 
     It will be appreciated that the receiver  200  may include control circuitry such as analogue circuitry, one or more microprocessors, baseband processors, digital signal processors, field-programmable gate arrays, microcontrollers, and/or application-specific integrated circuits with processing circuits. The control circuitry may be used in performing communication, monitoring and determination of a fault condition and control of the converter  240  such that it forms at least part of one or more of the communication circuitry  220 , monitoring circuitry  230  and converter  240 . 
     An illustrative inductive power receiver  200  is shown in  FIG. 5  in accordance with one embodiment. In this example, the receiver  200  includes one or more power receiving coil(s)  210 , communication circuitry  220 , monitoring circuitry  230 , a converter  240  and control circuitry  250 . In this example, the communication circuitry  220  includes an FSK demodulator  222 . In this example, the communication circuitry  220  includes an ASK modulator  224 , and may also include an ASK demodulator. In this example, the converter  240  includes a full-bridge synchronous rectifier  242  and a DC-DC buck converter  244 . 
     An illustrative method is shown in  FIG. 6 . The method  300  includes, in step  310 , producing an inductive power transfer field using an inductive power transmitter  100 . In step  320 , an inductive power receiver  200  couples to the inductive power transfer field. In step  330 , one or both of the transmitter  100  and receiver  200  modulates the inductive power transfer field to attempt to communicate with the other device. In step  340 , a determination is made whether a communication fault condition exists with the modulated field. Upon determination of the fault condition, in step  350  a control parameter of the transmitter  100  or receiver  200  is adjusted. 
     After a control parameter is adjusted, the power transfer field may be modulated again to attempt to communicate under the adjusted conditions. This may be referred to as a “re-try”. For example, in a packet-based system, a control parameter may be adjusted before the packet is retransmitted. If a communication fault condition is determined with respect to the re-try, the method  300  may adjust a control parameter again. This may be repeated up to a limited maximum number of times, up to a limited maximum time limit, or indefinitely until a fault condition is no longer determined. This may form a loop between the modulation  330 , determination  340  and adjustment  350  steps. The loop may be broken by a non-determination of a fault condition, a maximum number of re-tries being reached, or a maximum time limit being reached. A fault condition may no longer be determined by way of a positive determination of removal or alleviation of the fault condition or by absence of a determination of a fault condition. 
     The control parameter that is adjusted in a particular adjustment step may be the same control parameter as adjusted in another adjustment step or a different parameter. The direction in which a control parameter is adjusted in a particular adjustment step may be the same as in another adjustment step or a different direction. For example, if a control parameter is increased in one adjustment step, it may be decreased in another step. The amount by which a control parameter is adjusted in a particular adjustment step may be the same as in another adjustment step or a different amount. For example, a control parameter may be adjusted by a greater amount in each successive adjustment step. The control parameters may be adjusted according to a predetermined or dynamic strategy or rule. The control parameters may be adjusted randomly or according to a strategy or rule that incorporates some randomness. For example, a random choice of which control parameter to adjust may be made, but the adjustment may be by a fixed or limited amount. 
     If a fault condition is no longer determined, the loop between the modulation/re-try step  330 , determination  340  and adjustment  350  steps may be exited. After exiting this loop, the one or more adjusted control parameters may remain at the last adjusted state(s) or may return to the pre-adjustment state(s). The power transfer system may self-regulate back to a nominal operating state after exiting the loop. 
     If a maximum number of re-tries is reached, or if a time limit is reached or exceeded, the communication interface between the transmitter  100  and receiver  200  may be reset. In one example, the maximum number of retries is less than 20, less than 10, or less than 6. In one example, the maximum number of re-tries is 3. In one example the time limit is less than about 2 seconds, less than about 1 second, or less than about 600 ms. In one example, the maximum time is about 300 ms. 
     In one example, a control parameter may be progressively adjusted at each adjustment step until a fault condition is removed, a time limit is reached, or an adjustment limit of that control parameter is reached. If an adjustment limit of a control parameter is reached, a different control parameter may be adjusted in any subsequent adjustment step(s). For example, if a first parameter is increased in one or more adjustment steps until it reaches its maximum value or a dynamic or predetermined limit, the first parameter may be maintained in its last adjusted state and in a subsequent adjustment step a second parameter may be adjusted. 
     The method  300  may include, when a communication fault condition is determined, modulating the power transfer field to attempt to communicate one or more times (re-tries) without adjustment of the control parameters. This may be performed for a number of times or for a limited time. If a communication fault condition is determined after the one or more re-tries using the un-adjusted control parameters, the step of adjusting the control parameter(s) may then be performed. The number of re-tries at the unadjusted control parameters may be less than 10, less than 5, or less than 3. In one example, the number of re-tries at the unadjusted control parameters is 1. 
     As discussed previously, there are various suitable ways in which the transmitter  100  and receiver  200  may communicate via modulation of the power transfer field, various suitable ways in which a determination of a communication fault condition may be made, and various suitable control parameters that may be adjusted. The method  300  is not limited to any particular examples of performing these steps. 
     An illustrative example of the method  400  is shown in  FIG. 7  in accordance with one embodiment. The method begins with an inductive power transfer field being produced in step  310  and coupled to in step  320 . In step  330 , the power transfer field is modulated to attempt communication between an inductive power transmitter  100  and an inductive power receiver  200 . In step  340 , a determination is made whether there is a communication fault condition. If no fault is determined, the re-try loop is exited in step  342  without a re-try or control parameter adjustment being made. 
     If a communication fault condition is determined in step  340 , a timer may be started in step  342 . The timer is started in step  344  if it is currently at 0, i.e. it has not been started during this re-try loop because the re-try loop has just been entered. In this embodiment, there is a 300 ms time limit from the determination of a communication fault condition in step  340  before the communication interface will reset in step  346 , which allows for 3 re-tries. In this embodiment, the first re-try after a communication fault condition is determined is performed without adjustment of the control parameters. In step  346 , it is determined if this is the first re-try after determination of the communication fault condition and, if so, the method returns to step  330  to perform the first re-try without adjustment of the control parameters. If a communication fault condition is determined after this re-try, a control parameter of the transmitter converter  140  is adjusted. If the determination at step  346  is that this is not the first re-try, the method moves to step  350  to adjust a control parameter. 
     The adjusted control parameter is either inverter phase or DC-DC boost converter output voltage level. If the inverter phase is less than 180°, the phase will be increase towards 180°. If the phase is 180°, the boost converter output voltage will be increased. In this example, phase may be increased by 5° increments per step and boost converter output voltage may be increased by 0.1V increments per step. In step  352 , the current phase of the inverter is determined. If the phase is less than 180°, the method moves to step  354  in which the inverter phase is increased. If the determination in step  352  is that the inverter phase is already at 180°, the method moves to step  356  in which the output voltage of the boost converter is increased. After each of steps  354  and  356 , the method returns to step  330  to perform a re-try at the adjusted control parameters. 
     If, in step  348 , the timer reaches the time limit, which is 300 ms in this example, before it is determined in step  340  that the communication fault condition no longer exists, the communication interface will be reset. 
     In each of steps  342  and  348 , the timer will be reset (if necessary) in order to allow the time limit to start again from 0 upon further determination of a communication fault condition. 
     An illustrative example of a change from an unsuitable operating state to a suitable operating state is shown in FIG. X in accordance with one embodiment. The x axis of this plot corresponds to different use cases (need more), the y axis 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination, and elements from one embodiment may be combined with others.

Metadata:
Filing Date: 20181207
Publication Date: 20210720
Grant Date: 20210720
Priority Date: 20180907
Inventors: Huang, Rex Pius
ECKERT, MICHAEL SCOTT
DE JESUS, Mikhal
KUMAR, Arunim
SALVEKAR, ATUL
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0029", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J5/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 69720136