PATENT DOCUMENT

Publication Number: US-11996707-B2
Application Number: US-202217816081-A
Country: US
Kind Code: B2

Title: Wireless power transfer power control techniques

Abstract:
A wireless power transfer system can include an electronic device including a first wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil. The wireless power transfer circuitry can be capable of receiving power and transmitting power wirelessly via the first wireless power transfer coil. The system can further include an accessory device including a second wireless power transfer coil, a rectifier coupled to the second wireless power transfer coil, and an energy storage device coupled to the rectifier by a regulator circuit. The wireless power transfer circuitry can operate in a pulsed or burst wireless power transfer mode to deliver power to the accessory device.

Claims:
The invention claimed is: 
     
       1. A wireless power transfer system comprising:
 an electronic device including a first wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil, wherein the wireless power transfer circuitry is configured to receive power and transmit power wirelessly via the first wireless power transfer coil; and 
 an accessory device including a second wireless power transfer coil, a rectifier coupled to the second wireless power transfer coil, and an energy storage device coupled to the rectifier by a regulator circuit; 
 wherein the wireless power transfer circuitry operates in a pulsed or burst wireless power transfer mode to deliver power to the accessory device, the pulsed or burst wireless power transfer mode having an on time during which power is delivered to the accessory device and an off time during which power is not delivered to the accessory device. 
 
     
     
       2. The wireless power transfer system of  claim 1  wherein the wireless power transfer circuitry employs a variable on time, wherein the on time is terminated in response to the wireless power transfer circuitry detecting that the energy storage device is fully charged. 
     
     
       3. The wireless power transfer system of  claim 2  wherein the wireless power transfer circuitry detects that the energy storage device is fully charged by monitoring an amount of wireless power delivered to the accessory device. 
     
     
       4. The wireless power transfer system of  claim 2  wherein the wireless power transfer circuitry operates in the pulsed or burst wireless power transfer mode using a constant off time. 
     
     
       5. The wireless power transfer system of  claim 4  wherein the constant off time is determined by the electronic device responsive to information received from the accessory device relating to power consumption of the accessory device. 
     
     
       6. The wireless power transfer system of  claim 5  wherein the information received from the accessory device is received via a communication channel separate from the wireless power transfer channel. 
     
     
       7. The wireless power transfer system of  claim 2  wherein the wireless power transfer circuitry operates in the pulsed or burst wireless power transfer mode using a variable off time. 
     
     
       8. The wireless power transfer system of  claim 7  wherein the variable off time is terminated by a burst mode request pulse from the accessory device. 
     
     
       9. The wireless power transfer system of  claim 1  further comprising a power accessory having a third wireless power transfer coil, the power accessory also receiving power from the electronic device, with the second wireless power transfer coil of the accessory device being positioned between the first wireless power transfer coil of the electronic device and the third wireless power transfer coil of the power accessory. 
     
     
       10. The wireless power transfer system of  claim 9  wherein the power accessory is capable of delivering power to the electronic device and the accessory device via the third wireless power transfer coil. 
     
     
       11. An electronic device comprising:
 a wireless power transfer coil; and 
 wireless power transfer circuitry coupled to the wireless power transfer coil, wherein the wireless power transfer circuitry is configured to receive power and transmit power wirelessly via the first wireless power transfer coil, 
 wherein the wireless power transfer circuitry operates in a pulsed or burst wireless power transfer mode to deliver power wirelessly to an accessory device, the pulsed or burst wireless power transfer mode having an on time during which power is delivered to the accessory device and an off time during which power is not delivered to the accessory device. 
 
     
     
       12. The electronic device of  claim 11  wherein the wireless power transfer circuitry employs a variable on time, wherein the on time is terminated in response to the wireless power transfer circuitry detecting a decrease in power delivered to the accessory device. 
     
     
       13. The electronic device of  claim 12  wherein the decrease in power delivered to the accessory devices is associated with an energy storage device of the accessory device reaching a full charge state. 
     
     
       14. The electronic device of  claim 11  wherein the wireless power transfer circuitry operates in the pulsed or burst wireless power transfer mode using a constant off time. 
     
     
       15. The electronic device of  claim 14  wherein the constant off time is determined by the electronic device responsive to information received from the accessory device relating to power consumption of the accessory device. 
     
     
       16. The electronic device of  claim 15  wherein the information received from the accessory device is received via a communication channel separate from the wireless power transfer channel. 
     
     
       17. The electronic device of  claim 11  wherein the wireless power transfer circuitry operates in the pulsed or burst wireless power transfer mode using a variable off time. 
     
     
       18. The electronic device of  claim 17  wherein the variable off time is terminated by a burst mode request pulse from the accessory device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 63/261,485, filed Sep. 22, 2021, entitled “WIRELESS POWER TRANSFER POWER CONTROL TECHNIQUES,” the disclosure of which is incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     Wireless power transfer, in which power is delivered via inductive coupling between a power transmitter (PTx) and a power receiver (PRx), is useful for powering battery powered electronic devices. In some applications, intermittent wireless power transfer (e.g., “burst mode” wireless power transfer) may be used to enhance operating efficiency. 
     SUMMARY 
     To optimize intermittent wireless power transmission while also ensuring adequate power delivery to all relevant devices, control techniques may be adapted to account for powered accessories. 
     A wireless power transfer system can include an electronic device including a first wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil. The wireless power transfer circuitry can be capable of receiving power and transmitting power wirelessly via the first wireless power transfer coil. The system can further include an accessory device including a second wireless power transfer coil, a rectifier coupled to the second wireless power transfer coil, and an energy storage device coupled to the rectifier by a regulator circuit. The wireless power transfer circuitry can operate in a pulsed or burst wireless power transfer mode to deliver power to the accessory device. 
     The pulsed or burst wireless power transfer mode can have an on time during which power is delivered to the accessory device and an off time during which power is not delivered to the accessory device. The wireless power transfer circuitry can employ a variable on time, wherein the on time is terminated in response to the wireless power transfer circuitry detecting that the energy storage device is fully charged. The wireless power transfer circuitry can detect that the energy storage device is fully charged by monitoring an amount of wireless power delivered to the accessory device. The wireless power transfer circuitry can operate in the pulsed or burst wireless power transfer mode using a constant off time. The constant off time can be determined by the electronic device responsive to information received from the accessory device relating to power consumption of the accessory device. The information received from the accessory device can be received via a communication channel separate from the wireless power transfer channel. The wireless power transfer circuitry can operate in the pulsed or burst wireless power transfer mode using a variable off time. The variable off time can be terminated by a burst mode request pulse from the accessory device. 
     The wireless power transfer system can further include a power accessory having a third wireless power transfer coil, the power accessory also receiving power from the electronic device, with the second wireless power transfer coil of the accessory device being positioned between the first wireless power transfer coil of the electronic device and the third wireless power transfer coil of the power accessory. The power accessory can be capable of delivering power to the electronic device and the accessory device via the third wireless power transfer coil. 
     An electronic device can include a wireless power transfer coil and wireless power transfer circuitry coupled to the wireless power transfer coil. The wireless power transfer circuitry can be capable of receiving power and transmitting power wirelessly via the first wireless power transfer coil. The wireless power transfer circuitry can operate in a pulsed or burst wireless power transfer mode to deliver power wirelessly to an accessory device. The pulsed or burst wireless power transfer mode can have an on time during which power is delivered to the accessory device and an off time during which power is not delivered to the accessory device. 
     The wireless power transfer circuitry can employ a variable on time. The on time can be terminated in response to the wireless power transfer circuitry detecting a decrease in power delivered to the accessory device. The decrease in power delivered to the accessory devices can be associated with an energy storage device of the accessory device reaching a full charge state. The wireless power transfer circuitry can operate in the pulsed or burst wireless power transfer mode using a constant off time. The constant off time can be determined by the electronic device responsive to information received from the accessory device relating to power consumption of the accessory device. The information received from the accessory device can be received via a communication channel separate from the wireless power transfer channel. The wireless power transfer circuitry can operate in the pulsed or burst wireless power transfer mode using a variable off time. The variable off time can be terminated by a burst mode request pulse from the accessory device. 
     A method of operating a wireless power transmitter to provide pulsed or burst mode power to an accessory device can include initiating a power transfer interval during which wireless power transfer circuitry of the wireless power transmitter is operated to deliver power to the accessory device. The method can further include, upon expiration of an on time, terminating the power transfer interval by ceasing operation of the wireless power transfer circuitry, thereby initiating a sleep mode having an off time during which the wireless power transfer circuitry is not operated. The method can further include upon expiration of an off time, terminating the sleep mode by initiating a subsequent power transfer interval. 
     The on time can be variable and can be terminated in response to the wireless power transmitter detecting a decrease in power delivered to the accessory device. The decrease in power delivered to the accessory devices can be associated with an energy storage device of the accessory device reaching a full charge state. The off time can be constant. The constant off time can be determined by the wireless power transmitter responsive to information received from the accessory device relating to power consumption of the accessory device. The off time can be variable. The variable off time is terminated by a burst mode request pulse from the accessory device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a high-level schematic of a wireless power transfer system. 
         FIG.  2    illustrates burst mode operation of a WPT system, showing the rectifier output voltage. 
         FIGS.  3 A and  3 B  illustrate a personal electronic device, in the form of a mobile phone, together with a wirelessly powered accessory, in the form of a case, together with a wireless charger. 
         FIG.  4    illustrates a cross-section of a personal electronic device, in the form of a mobile phone, together with a wirelessly powered accessory, in the form of a case. 
         FIGS.  5 A- 5 C  are block diagrams illustrating various use cases of a personal electronic device, a wirelessly powered accessory, and a power accessory that can wirelessly charge or be charged by the personal electronic device. 
         FIG.  6    illustrates simplified timing diagrams corresponding to a pulsed or burst mode wireless power transfer operation. 
         FIG.  7    illustrates power versus time curves for an example pulse charging mode with adaptive T_on control. 
         FIG.  8    illustrates plots of burst or pulsed wireless power transfer with corresponding plots of receiver ripple voltage and load power delivered. 
         FIG.  9    illustrates a simplified schematic of a burst mode request pulse wireless power receiving accessory. 
         FIG.  10    illustrates simplified state diagrams corresponding to various wireless power transfer control techniques. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosed concepts. As part of this description, some of this disclosure&#39;s drawings represent structures and devices in block diagram form for sake of simplicity. In the interest of clarity, not all features of an actual implementation are described in this disclosure. Moreover, the language used in this disclosure has been selected for readability and instructional purposes, has not been selected to delineate or circumscribe the disclosed subject matter. Rather the appended claims are intended for such purpose. 
     Various embodiments of the disclosed concepts are illustrated by way of example and not by way of limitation in the accompanying drawings in which like references indicate similar elements. For simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant function being described. References to “an,” “one,” or “another” embodiment in this disclosure are not necessarily to the same or different embodiment, and they mean at least one. A given figure may be used to illustrate the features of more than one embodiment, or more than one species of the disclosure, and not all elements in the figure may be required for a given embodiment or species. A reference number, when provided in a given drawing, refers to the same element throughout the several drawings, though it may not be repeated in every drawing. The drawings are not to scale unless otherwise indicated, and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
       FIG.  1    illustrates a high-level schematic of a wireless power transfer system  100 . The left side of the figure illustrates a power transmitter (PTx)  103 , which receives an input voltage Vin and transmits energy to a receiver via magnetic induction, i.e., by coupling between transmit and receive coils represented by inductors L 1  and L 2 , respectively. (Each coil/inductor also has a corresponding intrinsic/parasitic resistance: R 1 /R 2 . These are illustrated in the schematic of  FIG.  1    but are not separate physical components.) The right side of the figure depicts a power receiver (PRx)  105  that receives power via the inductive coupling and delivers power to a load depicted by current source Iload. An input voltage Vin is supplied to inverter  102 . Inverter  102  generates an AC output having a predetermined frequency and a magnitude that is determined by input voltage Vin, which may be regulated by a separate regulator (not shown). This AC output voltage of inverter  102  is provided the transmit coil, represented by inductor L 1 , which is magnetically coupled a corresponding receive coil, represented by inductor L 2 . This results in energy transfer to the PRx  105 . PRx  105  includes a receive coil, represented by inductor L 2 , which has a voltage induced therein by magnetic induction via transmit coil L 1 . This AC voltage may be provided to a rectifier  106 , discussed in greater detail below, that converts the received AC voltage to an output DC voltage (Vrect) that may be supplied to a load. The wireless power transfer system  100  may include additional components, such as transmitter tuning capacitor Cpri and receiver tuning capacitor C 2  that may be used to tune the resonant frequency of the transmit and receive circuits to improve operating efficiency of the system. 
     In the illustrated embodiment, inverter  102  is a full bridge inverter made up of four switching devices Q 1 -Q 4 , although other inverter topologies could be used as appropriate for a given application. Also depicted at a high level is PWM controller  108 , which provides pulse width modulation signals to the switching devices Q 1 -Q 4  to generate a desired output voltage and/or current. These switching devices are illustrated as MOSFETs (metal-oxide-semiconductor field effect transistors), though other types switching devices (including, for example, IGBTs (insulated gate bipolar transistors), junction field effect transistors (JFETs), etc. could be used as appropriate for a given embodiment. Likewise, any suitable semiconductor technology, such as silicon, silicon carbide (SiC), gallium nitride (GaN), could be used depending on the specific application. The same applies to all other switching devices (including diodes) discussed in the present application. Switching devices Q 1 -Q 4  may be alternately switched to connect an input DC voltage (e.g., from boost regulator  108 ) to the transmit winding L 1 , producing an AC voltage that may be coupled to the PRx as described above. 
     Operation of inverter  102  will induce an AC voltage in inductively coupled PRx receiver coil L 2 . This AC voltage may be coupled to a rectifier  106 . In the illustrated embodiment, rectifier  106  is a full bridge active rectifier made up of four switches Q 5 -Q 7 . Although illustrated as MOSFET switches, other rectifier types, constructed using any suitable semiconductor technology, could also be used. These alternative configurations can provide for increased operating efficiency in some applications. 
     Operating a wireless power transfer system intermittently, e.g., in a burst mode, can address inefficiencies associated with at the system under certain loading conditions. In burst mode, power is transmitted in short bursts instead of continuously. Thus, a burst can include one or more AC pulses from the inverter. Following the one or more burst pulses, there may be an intervening time period during which no AC power is transmitted. This intervening time period may then be followed by another burst of one or more AC pulses. This can mitigate light load inefficiencies by decreasing switching losses and quiescent current losses. Additionally, carefully controlled use of burst mode can allow the system to effectively be loaded at its optimum output resistance, thus allowing the AC/AC system to be operated at or near its peak efficiency, regardless of actual output power. Finally, the use of burst mode can be used to control the voltage gain of the system, i.e., the ratio of the output voltage Vrect to the input voltage Vin. 
       FIG.  2    shows burst mode operation, with the switching on and off times and showing the rectifier output voltage  210 . Beginning, for example, at time t1, an on time of the inverter may begin. In some applications, this operation may be triggered by a burst mode request pulse from the receiver. In other applications, the operation may be initiated by other triggers, some examples of which are described herein. During this on time, switching on the inverter side may transfer power to the receiver side, causing the rectifier voltage Vrect to increase to a peak value at time t2, corresponding to when the burst is terminated, i.e., the inverter stops switching. Then, during the off time (from t2 to t3), when the inverter is not switching, the rectifier voltage Vrect may decrease to a valley threshold (Vth_valley). In some applications, this can cause the receiver to send another burst mode request pulse at time t3, repeating the cycle. In other applications, the duration of the off time may be determined by other mechanisms. 
     In an exemplary implementation of burst mode wireless power transfer, the power receiving device can communicate to the power transmitting device that power is required by initiating a burst mode request pulse. This pulse may be created by the receiver by using the rectifier switches to apply a predetermined switching pattern, sequence, or state to the receiver coil. This predetermined switching pattern, sequence, or state alters the reflected impedance magnetically coupled via the transmitter and receiver windings to the power transmitter/inverter. Upon detection of this pulse, the transmitter/inverter initiates a burst of pulses as described above. Exemplary implementations of burst mode control circuitry are disclosed in Applicant&#39;s co-pending U.S. patent application Ser. No. 17/386,542, entitled “Efficient Wireless Power Transfer Control,” filed Jul. 28, 2021 and 63/216,831, entitled “Wireless Power Transfer with Integrated Communications,” filed Jun. 30, 2021, which are incorporated by reference in their entirety. 
       FIGS.  3 A and  3 B  illustrate a personal electronic device  320 , in the form of a mobile phone, together with a wirelessly powered accessory  321 , in the form of a case, together with a wireless charger  327 . Although the given example includes a mobile phone and a case, personal electronic device, and wirelessly powered accessory  321  could be any of a variety of devices, and the example of a phone and case is provided as one example context and should not be construed as the only context in which the teachings herein are applicable. Personal electronic device  320  can be configured to allow for wireless power transfer, including charging of an internal battery of personal electronic device  320  and also optionally including wireless delivery of power to accessory device  321 . To facilitate such wireless power transfer, personal electronic device  320  may include a wireless power transfer coil  322 . Personal electronic device  320  may also include a magnet array  324 , which may include a plurality of magnets arranged in a suitable configuration to aid in positioning an accessory and/or charger. Although illustrated in a ring configuration, the locating magnets may be disposed in any desired configuration and may include any number of magnets. Alternatively, other positioning aids or no positioning aids could be provided as appropriate for a particular application. 
     Wirelessly powered accessory  321  may include a wireless power transfer coil  323  (corresponding to wireless power transfer coil  322 ) and magnet array  325  (corresponding to magnet array  324 ). Wireless power transfer coil  321  can facilitate wireless power transfer  331  with personal electronic device  320  in either direction (i.e., transferring power either to or from personal electronic device  320 ). Likewise, magnet array  325  can cooperate with magnet array  324  to suitably position personal electronic device  320  relative to accessory  321  as desired. Or, as noted above, other positioning aids or no positioning aids could also be used. Accessory device  321  may also include other components necessary for the accessory to function. For example, wirelessly powered accessory  321  could be a battery case, in which additional battery capacity for personal electronic device  320  can be provided via wireless power transfer, or the battery case can be charged by personal electronic device  320 . 
       FIG.  3 B  illustrates the above-described personal electronic device  320  and wirelessly powered accessory  321  with an additional wireless charger  327 . Wireless charger  327  may also have a wireless power transfer coil  328  corresponding to wireless power transfer coils  322  and  323 , allowing for charger  327  to deliver power  332   a  and  332   b  to wirelessly powered accessory  321  and personal electronic device  320 , respectively. In this configuration, wireless power transfer may be thought of as occurring between charger  327  and personal electronic device  320 , with wirelessly powered accessory  321  acting to intercept a portion of the power delivered. Further details of such configurations are described below with respect to  FIGS.  5 A- 5 C . 
       FIG.  4    illustrates a simplified cross-section of a personal electronic device  320 , in the form of a mobile phone, together with a wirelessly powered accessory  321 , in the form of a case. Also depicted in  FIG.  4    are wireless power transfer coil  322  and magnet  324  of personal electronic device  320 , together with wireless power transfer coil  323  and magnet  325  of wirelessly powered accessory  321 . The cross-sectional view of  FIG.  4    illustrates the relative positioning of such components in a typical usage configuration. 
       FIGS.  5 A- 5 C  are block diagrams illustrating various use cases of a personal electronic device  540 , an accessory  550 , and a power accessory  560  that can wirelessly charge or be charged by the personal electronic device. As described above, personal electronic device  540  may be a mobile phone, but could also be any other device, such as a tablet, laptop, or notebook computer, Accessory  550  could be any device intended to be: (a) powered by personal electronic device  540  (as described below with reference to  FIG.  5 A ) or; (b) to receive power from power accessory  560  when power accessory  560  is powering personal electronic device  540  (as described below with reference to  FIG.  5 B ) or; (c) to receive power from personal electronic device  540  when electronic device  540  is powering power accessory  560  (as described below with reference to  FIG.  5 C ). 
       FIG.  5 A  illustrates an example configuration in which a personal electronic device  540  acts in a power transmitter mode to wirelessly power an accessory  550 . Personal electronic device  540  can include a battery  544 , that may be used to power both personal electronic device  540  itself and accessory  550  via wireless power transfer. Personal electronic device  540  can further include a system  545  powered by battery  544  (via an intermediate power management unit and/or regulator, not shown). System  545  can include any of a variety of multiple subsystems, such as processing subsystems, input/output subsystems, communications subsystems, storage subsystems, and the like. In some embodiments, system  545  can include communications subsystems, for example a NFC/Bluetooth communications system that can be used to communicate with an accessory  550 . Battery  544  may also supply power to a wireless power transfer module  542 . This may occur via an optional intermediate regulator  543 , which can be, for example, a boost converter. This presupposes that, as is commonly the case, the voltage needed by wireless power transfer module  542  is greater than the minimum battery voltage. However, in some applications, boost converter  543  could be replaced with any suitable switching or linear regulator. Wireless power transfer module  542  can drive a wireless power transfer coil  541  to deliver power wirelessly to accessory  550 . 
     Accessory  550  can include wireless power transfer coil  541  that can receive power from personal electronic device  540  (or any other compatible wireless power transfer device). The AC voltage induced by such wireless power transfer may be converted to DC by a rectifier  552 , which can be a diode rectifier or an active rectifier made up of suitable switching devices. The DC voltage resulting from such rectification can be provided to a charger circuit  553  that can deliver power to an energy storage device  554 , such as a supercapacitor or battery. In some applications, charger circuit  553  can be a buck charger or low dropout regulator. In other applications, any suitable switching or linear regulator could be used, including regulators that increase the rectified DC voltage to a higher level, if appropriate for a given application. Finally, energy storage device  554  can be used to power a system load  555  of accessory  550 , which may include any of a variety of subsystems, including processing subsystems, input/output subsystems, communications subsystems, storage subsystems, and the like. In some embodiments, system  555  can include communications subsystems, for example an NFC/Bluetooth communications system that can be used to communicate with an personal electronic device  540 . 
     As noted above, in the configuration of  FIG.  5 A , personal electronic device  540  can act as a wireless power transmitter to power accessory  550 , which acts as a wireless power receiver. To improve operating efficiency, accessory  550  may employ a pulsed or burst mode charging operation, as described in greater detail below. To briefly summarize, in the pulsed or burst mode charging, accessory  550  periodically draws pulses or bursts of power from personal electronic device  540  to charge energy storage device  554  and power system load  555 . In between these pulses or bursts, system load  555  discharges energy storage device  554 . 
       FIG.  5 B  illustrates an example configuration in which a power accessory  560  acts in a power transmitter mode to wirelessly power a personal electronic device  540  that acts in a power receiver mode. Additionally illustrated in  FIG.  5 B  is an accessory  550  that is arranged to take power from the transfer between power accessory  560  and personal electronic device  540 . Power accessory  560  can include a power source  564 , which may be an AC adapter (for receiving mains power) or a battery (a source of DC power). This power source may be coupled to wireless power transfer circuitry  562  via an optional intermediate regulator  563 . Regulator  563  may, in some applications, be a boost converter that increases the voltage from power source  564  to a level needed by wireless power transfer circuitry  562 . However, in other applications, regulator  563  could be any suitable form of switching or linear regulator. The regulated voltage output of regulator  563  may be delivered to wireless power transfer circuitry  562 , which can drive wireless power transfer coil  561  to deliver power wirelessly to personal electronic device  540 , which includes wireless power transfer coil  541 , and accessory  550 , which includes wireless power transfer coil  551 . 
     Wireless power transfer circuitry  562  may also include in-band communications circuitry configured to allow for communications with corresponding circuitry in personal electronic device  540 , e.g., in wireless power transfer circuitry  542 , using modulation of the voltage, current, and/or power wirelessly transferred. For example, the in-band communications circuitry may be configured to employ frequency shift keyed communications, amplitude shift keyed communications, or any other suitable in-band communications technique. 
     Personal electronic device  540  includes the various components described above with respect to  FIG.  5 A . In the configuration of  FIG.  5 B , wireless power transfer circuitry  542  acts as a wireless power receiver. Likewise, regulator  543  may operate as a buck regulator to charge battery  544  rather than as a boost regulator as described above with respect to  FIG.  5 A . Regulator  543  may thus be a bidirectional buck/boost regulator (or any other suitable regulator configuration). In the receiver mode, an AC voltage is induced in wireless power transfer coil  541  by operation of wireless power transfer circuitry  562  and wireless power transfer coil  561  of power accessory  560 . This induced voltage is rectified by wireless power transfer circuitry  542  and provided to regulator  543  which can charge battery  544  that in turn powers system load  545  as described above. Wireless power transfer circuitry  542  may also include in-band communications circuitry configured to allow for communications with corresponding circuitry in power accessory  560 , e.g., in wireless power transfer circuitry  562 , using modulation of the voltage, current, and/or power wirelessly transferred. For example, the in-band communications circuitry may be configured to employ frequency shift keyed communications, amplitude shift keyed communications, or any other suitable in-band communications technique. 
     Additionally, accessory  553  includes the various components described above with respect to  FIG.  5 A . Additionally, these components operate as described above, including a pulsed or burst mode operation described in greater detail below. Wireless charging coil  551  of accessory  553  may be positioned with respect to wireless power transfer coil  561  of power accessory  560  and wireless power transfer coil  541  of personal electronic device  540  to take power from the power transfer stream between power accessory  560  and personal electronic device  540 . As an example, accessory  550  may be positioned with respect to power accessory  560  and personal electronic device  540  so that its wireless power transfer coil  551  is disposed between the wireless power transfer coils  561  and  541  of power accessory  560  and personal electronic device  540 , respectively. 
       FIG.  5 C  illustrates an example configuration in which a power accessory  560  acts in a power receiver mode to wirelessly receive power from a personal electronic device  540  that acts in a power transmitter mode. Additionally illustrated in  FIG.  5 C  is an accessory  550  that is arranged to take power from the transfer between power accessory  560  and personal electronic device  540 . Power accessory  560  includes the same components described above with respect to  FIG.  5 B , but is operated to receive power from, rather than deliver power to, personal electronic device  540 . Thus, wireless power transfer circuitry  562  acts as a rectifier to rectify a voltage induced across wireless power transfer coil  561  by operation of personal electronic device  540  and wireless power transfer coil  541  as described above with respect to  FIG.  5 A . The rectified voltage is provided to regulator  563 , which, in some applications, may operate as a buck charger to charge energy storage device/battery  564 . Thus, in some embodiments, regulator  563  can be a bidirectional buck boost converter, although any suitable regulator type may be used in a given application. Additionally, as described above, WPT circuitry  562  can include in band communications circuitry that facilitates communication with corresponding circuitry in personal electronic device  540 /wireless power transfer circuitry  542  as described above. 
     Personal electronic device  540  includes the components described above with respect to  FIGS.  5 A and  5 B  and operates as described with respect to  FIG.  5 A  to deliver power to power accessory  560 . Likewise, WPT circuitry  542  can include in band communications circuitry that facilitates communication with corresponding circuitry in power accessory  560  (e.g., wireless power transfer circuitry  562 ) as described above. Additionally, accessory  553  includes the various components described above with respect to  FIGS.  5 A and  5 B . These components can operate as described above, including a pulsed or burst mode operation described in greater detail below. Wireless charging coil  551  of accessory  553  may be positioned with respect to wireless power transfer coil  561  of power accessory  560  and wireless power transfer coil  541  of personal electronic device  540  to take power from the power transfer stream between power accessory  560  and personal electronic device  540 . As an example, accessory  550  may be positioned with respect to power accessory  560  and personal electronic device  540  so that its wireless power transfer coil  551  is disposed between the wireless power transfer coils  561  and  541  of power accessory  560  and personal electronic device  540 , respectively. 
       FIG.  6    illustrates simplified timing diagrams corresponding to a pulsed or burst mode wireless power transfer operation. Such a pulsed or burst mode wireless power transfer operation may be employed, for example, by accessory  550 , which can intermittently charge energy storage device  554  (e.g., a battery or super capacitor) and intermittently allow system load  555  to discharge energy storage device  554 . In  FIG.  6   , power transfer intervals  664  correspond to power transfer windows, during which rectifier  552  and regulator/charger/LDO  553  are operating to draw power via wireless power transfer coil  551  and store energy in energy storage device  554 . Timing diagram  661  corresponds to a full load or high load condition for accessory  550 . In this condition, power transfer intervals  664   a ,  664   b , and  664   c  occur relatively frequently over time. In between these power transfer intervals  664  is a sleep mode, during which energy is not transferred to accessory  550  via the inductive link. The time between the beginning of a first power transfer interval  664   a  and the beginning of the subsequent power transfer interval is the cycle time T_cycle. The duration of a power transfer interval is the on time T_on, i.e., the time during which rectifier  552  is switching and/or the time during which regulator  553  is drawing power from wireless power transfer coil  551 . The off time T_off, corresponding to the duration of the sleep mode, is the difference between the cycle time T_cycle and the on time T_on. 
     Timing diagram  662  corresponds to a moderate load condition of accessory  550 . In this condition power transfer intervals  664   d  and  664   e  are further apart, corresponding to a longer cycle time. Timing diagram  663  corresponds to a light load condition of accessory  550 . In this condition power transfer interval  664   f  occurs, and the cycle time T_cycle is much longer, such that the subsequent power transfer interval is not visible on the scale of the diagram. In the illustrated examples, T_on for power transfer intervals  664   d ,  664   e , and  664   f  is the same as in timing diagram  661 , and the off times, or durations of the sleep modes are longer to provide the increased cycle time T_cycle. However, in some embodiments described below, on time T_on could be of variable length, i.e., adaptive. Additionally or alternatively, the off time T_off could be controlled by alternative techniques. In a first technique, the off time may be held constant. In a second technique, accessory  550  may send a burst mode request pulse to trigger the powering device as needed. These control techniques are described in greater detail below. 
     To provide adaptive control of the on time T_on, various system operating objectives may considered. For example, it may be desirable during the power transfer interval  664 , it may be desired that energy storage device  554  be fully charged. When energy storage device  554  reaches a fully charged, its charging current will drop relatively quickly, which also corresponds to a decrease in power required by the wireless power transfer circuitry providing the power (e.g., WPT circuitry  542  in the configuration of  FIGS.  5 A and  5 C  or WPT circuitry  562  in the configuration of  FIG.  5 B ). This allows for the power transmitting device, either personal electronic device  540  in the configuration of  FIGS.  5 A and  5 C  or the power accessory  560  in the configuration of  FIG.  5 B , to monitor the power delivered by its wireless power transfer circuitry  542 / 562  to detect when energy storage device  554  of accessory  550  has been fully charged. The power transmitting device to terminate wireless power transfer when energy storage device  554 /accessory  550  has been fully charged. 
       FIG.  7    illustrates exemplary power versus time curves for various components of a wireless power transfer system as described above employing adaptive T_on control. Curve  771  depicts the power versus time for the wireless power transfer circuitry  542 / 562  of the power transmitting device. Curve  772  depicts the power of the regulator supplying the wireless power transfer circuitry  542 / 562 , e.g., boost converter/regulator  543 / 563 . Curve  773  depicts the power delivered by buck charger/LDO  553  of accessory  550 . During power transfer interval  664 , the wireless power transfer circuitry  542 / 562  of the power transmitting device  540 / 560  is active. The beginning of this state may be triggered at time t0 upon expiration of the time out interval for the preceding sleep mode. Thus, at time to, the power transmitting device&#39;s wireless power transfer circuitry  542 / 562  begins to run, and the output of the regulator that powers such circuitry, e.g., boost converter  543 / 563 , will begin to increase. At time t1, the inverter of WPT circuitry  542 / 562  can begin to run, and the output of buck charger/LDO  553  can begin to ramp up. At time t2, buck charger/LDO  553  reaches maximum power for the highest rate of charging of energy storage device  554 . At time t3, energy storage device  554  reaches its maximum charge state, and the charging current (and correspondingly the power) begin to ramp down, reflected in both curves  772  and  773 . At time t4, the power transmitting device can stop its wireless power transfer circuitry when the power drops below a predetermined level, triggering the beginning of the sleep mode. This cycle can repeat upon expiration of the off time, which may be determined according to one of the techniques described below. 
     A first technique for determining the off time T_off, i.e., the duration of the sleep mode between power transfer intervals  664  is to use a constant off time. The constant off time may be selected so that the minimum state of charge/voltage of accessory energy storage device  554  remains above a critical value (e.g., brownout value) that would disable system  555 . This may be achieved in a variety of ways. For example, accessory  550  may provide pertinent parameters of its design to personal electronic device  540  via a communications channel, such as the illustrated NFC/Bluetooth communication channel. Such parameters could relate to power consumption of the accessory device, including, for example, full load power level, a default off time during full load, operating mode, etc. From this information, personal electronic device  540  may select or set a suitable fixed off time that will provide the guarantees described above. This way of determining the off time is only one example, and various other techniques could also be used. In any case, once the fixed off time is determined, the power transmitting device can power up and charge energy storage device  554  as described above with respect to  FIG.  7   . Further, the power transmitting device may stop transferring power when the power drops below the predetermined threshold, corresponding to energy storage device  554  reaching a full state of charge.  FIG.  8    illustrates load power and receiver ripple voltage for such a system. The power transmitting device can then wait for the determined fixed off time T_off to initiate the next charging cycle. 
       FIG.  8    illustrates the constant T_off operating mode for two exemplary load levels of accessory  550 . With reference to load power plot  875 , the average accessory load is at a relatively higher level from time t0 until time t3, and which point the average load decreases to a relatively lower level until time t6, at which point it again increases. Corresponding power transfer intervals  864   a  and  864   b  are also illustrated. During the higher average power periods, the duration of power transfer intervals  864   a  is relatively longer, corresponding to the adaptive T_on control technique described above. During the lower average power periods, the duration of power transfer intervals  864   b  is relatively shorter, again corresponding to the adaptive T_on control technique described above. In all cases, the power transfer intervals are separated by sleep modes having a fixed duration T_off, selected as described above. 
     Plot  874  of  FIG.  8    depicts the ripple voltage experienced by accessory  550  as a result of this operation. For example, this may be the voltage of energy storage device  554 , which also corresponds to its state of charge. Beginning at time t0, when the accessory is experiencing the higher average load, energy storage device  554  is in a relatively lower state of charge, corresponding to a relatively lower voltage V 3 . Operation of power transfer window  864   a  serves to charge energy storage device  554 , increasing its state of charge until it reaches a full charge state, which corresponds to voltage V 3  at time t1. At this time, the power transmitting device enters a sleep mode for the fixed duration T_off. As a result, the state of charge and corresponding voltage decrease. At time t2, determined by the fixed T_off duration, a subsequent power transfer interval begins, bringing the state of charge of energy storage device  554  back up to a fully charged state, corresponding to voltage V 1 , at which point a subsequent fixed duration sleep state is entered. 
     At time t3, which happens to but need not occur at the beginning of a sleep state, the average load of accessory  550  decreases. The fixed off time (T_off) of this sleep state remains the same, but at time t4, when the next power transfer interval  864   b  begins, it takes relatively less time (until t5) to fully charge energy storage device  554  because it entered power transfer interval  864   b  in a relatively higher state of charge corresponding to a voltage V 2 . This corresponds to a shorter on time, as described above. Nonetheless, the off time T_off remains fixed during this relatively lower load interval. At time t6, when the average load of accessory  550  again increases, the system adapts by increasing the on time of the power transfer intervals, while holding the off time constant. 
     The above-described constant off time has the advantage of simplicity, as it requires no express feedback path between accessory  550  and the powering device, although in some embodiments and initialization communication channel may be provided to allow the power transmitting device to select a suitable fixed off time. However, one potential disadvantage of the constant off time control technique can be the increased ripple voltage experienced by accessory  550  during relatively higher load conditions. This can be alleviated by employing of a burst request pulse control technique between accessory  550  and the power transmitting device, in which the accessory device can send a request for the power transmitting device to initiate a power transfer interval when needed, although this requires a feedback channel to receive the pulses, which can be the power transfer channel, as illustrated in  FIG.  9   . 
       FIG.  9    illustrates a simplified schematic of a burst mode request pulse wireless power receiving accessory  550 , together with power transmitting device  540 . Power transmitting device  540  may be a personal electronic device  540  or, in some embodiments, could be a power accessory  560 .  FIG.  9    illustrates the power transmitting device in a conceptually similar way, but simplified way, as PTx  103  was depicted above in  FIG.  1   . More specifically, the depiction of the wireless power transfer circuitry is slightly expanded to show inverter  102  made up of switching devices Q 1 -Q 4 , with control circuitry  108 , wireless power transfer coil  541 , tuning capacitor CTX, and burst mode detection circuitry  981 , described in greater detail below. Similarly, accessory  550  is depicted in a way conceptually similar, but simplified, as PRx  105  was depicted in  FIG.  1   . More specifically, diode rectifier  552  is expanded to show rectifier diodes  552   a  and  552   b , energy storage device  554  is shown as a (super-) capacitor, and burst mode request circuitry including switches Qr 1 , Qr 2 , and state machine  982  are added. 
     Burst request mode pulses and various apparatus and methods of their use are described in greater detail in Applicant&#39;s co-pending U.S. patent application Ser. No. 17/386,542, entitled “Efficient Wireless Power Transfer Control,” filed Jul. 28, 2021 and 63/216,831, entitled “Wireless Power Transfer with Integrated Communications,” filed Jun. 30, 2021, which are incorporated by reference in their entirety. For purposes of the present disclosure, such circuitry may be distilled down to burst request mode pulse generation circuitry  982  located in accessory  550  and burst request mode pulse detection circuitry  981 , located in wireless power transmitting device  540 . Burst request mode pulse generation circuitry  982  may include any suitable circuitry that monitors Vout/the voltage of energy storage device  554 , which corresponds to its state of charge. When this voltage is above a threshold corresponding to a brownout threshold, the system can be in a wait state. When this voltage reaches the threshold/critical level, circuitry  982  can transition to a state in which the receiver LC tank is short circuited to discharge capacitor CRX, for example, using switch Qr 2 . Subsequently, circuitry  982  can transition to a state in which the receiver LC tank is connected directly to Vout/energy storage device  554 . This sequence can be repeated until the output voltage Vout rises above the critical threshold, resulting in a series of burst request mode pulses being sent over the power transfer channel via the magnetic coupling between accessory wireless power transfer coil  551  and power transmitting device wireless power transfer coil  541 . 
     On the transmitter side, burst request mode pulse detection circuitry  981  may be configured to monitor the voltage across capacitor CTX of the transmitter side LC tank (as shown) or to monitor the voltage across wireless power transfer coil  541 . In either case, the switching operations of switches Qr 1  and Qr 2  result in a series of characteristic pulses that may be detected by circuitry  981  and provided to wireless power transmitter control circuitry  108  to cause wireless power transfer circuitry  542  to initiate a power transfer interval  664 , which can be done repeatedly so long as burst request mode pulses are being received, i.e., until energy storage device  554  and the corresponding voltage Vout are above the brownout threshold. 
       FIG.  10    illustrates a series of simplified state diagrams  1091 - 94  corresponding to various wireless power transfer control techniques for powering an accessory  550  from a wireless power transfer device  540 / 560 , including a configuration in which the accessory is taking from an otherwise established wireless power transfer channel. These various techniques incorporate various combinations of the on time and off time control techniques described above with reference to  FIGS.  6 - 9   . State diagram  1091  corresponds to an “ideal” situation in which the power transmitter “knows” when the Vout ( FIG.  9   ) reaches the critical threshold (Vmin) and based on this transitions from the off state  1091   b  (corresponding to the off time/sleep mode described above) to the on state  1091   a  (corresponding to the on time/power transfer interval  664 ). Then when Vout reaches Vmax (which, again, the power transmitter “knows”), the power transmitter transitions from on state  1091   a  back to off state  1091   b . The transmitter knowledge in this case may be achieved through some sort of feedback channel based on either in-band communication or a separate communications channel, examples of which were described above. 
     State diagram  1092  corresponds to a first control technique based on a burst request mode pulse and power cliff detection technique. The “power cliff” in this case is the decrease in power through the wireless power transfer channel caused by energy storage device  554  reaching its full state of charge. Detecting this Pin (power in) cliff can cause a transition from on state  1092   a  to an ‘update Toff’ state  1092   c  in which the off time may be updated. In one update technique, the average load current can be determined, e.g., using the duty cycle of on time versus sleep mode, and this load current may be used to derive a maximum off time, e.g., from a lookup table. These operations may be performed by either the accessory itself or by the power transmitting device. If performed by the accessory, it can communicate the maximum off time to power transmitting device using an available communication channel. If the determination is made by the wireless power transmitting device, it can update its own control circuitry as appropriate. In either case, after Toff is updated (if necessary), the system can transition to off state  1092   b . Then when the determined Toff is reached or if a burst mode request pulse is received, the power transmitting device can transition back to on state  1092   a.    
     State diagram  1093  corresponds to a second control technique based on a burst request mode pulse and an input power estimation. Beginning with on state  1093   a , when the predetermined on time Ton is reached, the power transmitting device can transition to the off state  1093   b . Then when either a predetermined off time Toff is reached or a burst mode request pulse is received, the power transmitting device can transition to the update Ton, Toff state  1093   c . In this state, the “instantaneous” load power can be determined from any suitable estimation mechanism employed by power transmitting device  540  or accessory  550 . The determined power level can then be used to derive a suitable on time Ton and off time Toff from a lookup table. These values can then be provided to the wireless power transmitter device, which also transitions to the on state  1093   a.    
     State diagram  1094  correspond to the adaptive T_on technique described with respect to  FIG.  7    and the fixed T_off technique described above with reference to  FIG.  8   . Beginning with the on state  1094   a , the power transmitting device can detect the input power (Pin) “cliff” associated with energy storage device  554  reaching a full charge state. This can trigger a transition to the off state  1094   b  corresponding to the sleep mode between power transfer intervals  664 . Then, after a fixed off time Toff, corresponding to the duration of the sleep state and which may be determined based on the maximum load of accessory  550 , the power transmitting device can transition back to the on state  1094   a.    
     The foregoing describes exemplary embodiments of pulsed or burst mode wireless power transfer. Such systems may be used in a variety of applications but may be particularly advantageous when used in conjunction with wireless power transfer systems personal electronic devices such as a mobile phones, smart watches, and/or tablet computers and accessories for such devices such as wireless earphones, styluses, charging cases, and the like. However, a wide variety of wireless power transfer systems may advantageously employ the techniques described herein. Although numerous specific features and various embodiments have been described, it is to be understood that, unless otherwise noted as being mutually exclusive, the various features and embodiments may be combined in various permutations in a particular implementation. Thus, the various embodiments described above are provided by way of illustration only and should not be constructed to limit the scope of the disclosure. Various modifications and changes can be made to the principles and embodiments herein without departing from the scope of the disclosure and without departing from the scope of the claims.

Metadata:
Filing Date: 20220729
Publication Date: 20240528
Grant Date: 20240528
Priority Date: 20210922
Inventors: SHI, LIXIN
MOUSSAOUI, ZAKI
QIU, WEIHONG
XU, Zelin
CHABALKO, MATTHEW J
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00034", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00711", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0049", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 85383504