Wireless power transfer system

Abstract

A wireless power receiver, method, and corresponding processing circuitry for the same are disclosed. The wireless power receiver includes a receiver coil configured to receive a wireless power transfer signal transmitted by a wireless power transmitter and a load coupled to the receiver coil. The wireless power receiver further includes communication circuitry configured to communicate a synchronization message to the wireless power transmitter which indicates time durations for repeating time intervals of foreign object detection and wireless power transfer. The foreign objection detection time periods correspond to periods of reduced power transfer to improve detection of foreign objects. The communication circuitry is configured to communicate a measured parameter, such as power received from an electromagnetic test signal, to the wireless power transmitter during the synchronized foreign object detection time periods, such that the wireless power transmitter can detect the presence or absence of a foreign object.

1 . A wireless power receiver comprising:
 a receiver coil,   wherein the receiver coil is configured to receive a wireless power transfer signal transmitted by a wireless power transmitter;   a load coupled to the receiver coil,   wherein the load is configured to receive power from the receiver coil;   communication circuitry, wherein the communication circuitry is configured to send a synchronization message to the wireless power transmitter,   wherein the synchronization message indicates a first time duration of a first time period and a second time duration of a second time period,   wherein the first time period corresponds to a period of foreign object detection and the second time period corresponds to a period of wireless power transfer,   wherein the first time period and the second time period are part of a repeating time interval; and   a load controller circuit, wherein the load controller circuit is configured to adapt loading of the wireless power transfer signal such that the load is reduced during the first time period,   wherein, during the first time period:
 the wireless power receiver is configured to receive an electromagnetic test signal from the wireless power transmitter, and 
 the communication circuitry is configured to communicate a measured parameter to the wireless power transmitter, wherein the measured parameter comprises an indication of power received by the wireless power receiver during the first time period. 
   
     
     
         2 . The wireless power receiver of  claim 1 , wherein the measured parameter is used by the wireless power transmitter to detect the presence of a foreign object. 
     
     
         3 . The wireless power receiver of  claim 1 , wherein, during the second time period, the wireless power receiver is configured to continuously measure power provided to the load, and
 wherein if the measured power is below a preset power level, the communication circuitry is configured to request a longer time duration for the first time period.   
     
     
         4 . The wireless power receiver of  claim 1 , wherein, during the second time period, the wireless power receiver is configured to continuously measure power provided to the load, and
 wherein if the measured power is greater than a preset power level, the communication circuitry is configured to request a shorter time duration for the first time period.   
     
     
         5 . The wireless power receiver of  claim 1 , wherein the load controller circuit comprises a switching circuit, and
 wherein the switching circuit is configured to disconnect the load during the first time period such that a received power level is reduced during the first time period.   
     
     
         6 . The wireless power receiver of  claim 1 ,
 wherein the communicator circuitry is configured to communicate a request for the first time duration and the second time duration, and   wherein the communication circuitry is configured to receive a response indicating the first time duration and the second time duration as determined by the wireless power transmitter.   
     
     
         7 . The wireless power receiver of  claim 1 , wherein the wireless power transfer signal comprises an electromagnetic field, and wherein a strength of the electromagnetic field during the first time period is greater than or equal to a strength of the electromagnetic field during the second time period. 
     
     
         8 . A method of receiving power via a wireless power receiver comprising:
 receiving, via a receiver coil, a wireless power transfer signal transmitted by a wireless power transmitter,   receiving, in a load coupled to the receiver coil, wireless power from the wireless power transfer signal;   sending a synchronization message to the wireless power transmitter,   wherein the synchronization message indicates a first time duration of a first time period and a second time duration of a second time period,   wherein the first time period corresponds to a period of foreign object detection and the second time period corresponds to a period of wireless power transfer   wherein the first time period and the second time period are part of a repeating time interval; and   adapting loading of the wireless power transfer signal such that the load is reduced during the first time period; and   during the first time period:
 receiving an electromagnetic test signal from the wireless power transmitter, and 
 communicating a measured parameter to the wireless power transmitter, wherein the measured parameter comprises an indication of power received by the wireless power receiver during the first time period. 
   
     
     
         9 . The method of  claim 8 , wherein the measured parameter is used by the wireless power transmitter to detect the presence of a foreign object. 
     
     
         10 . The method of  claim 8 , wherein, during the second time period, the method further comprises:
 continuously measuring power provided to the load, and   if the measured power is below a preset power level, requesting a longer time duration for the first time period.   
     
     
         11 . The method of  claim 8 , wherein, during the second time period, the method further comprises:
 continuously measuring power provided to the load, and   if the measured power is above a preset power level, requesting a shorter time duration for the first time period.   
     
     
         12 . The method of  claim 8 , comprising disconnecting the load during the first time period such that a received power level is reduced during the first time period. 
     
     
         13 . The method of  claim 8 , further comprising
 communicating a request for the first time duration and the second time duration, and   receiving a response indicating the first time duration and the second time duration as determined by the wireless power transmitter.   
     
     
         14 . The method of  claim 8 , wherein the wireless power transfer signal comprises an electromagnetic field, and wherein a strength of the electromagnetic field during the first time period is greater than or equal to a strength of the electromagnetic field during the second time period. 
     
     
         15 . A non-transitory computer readable medium having stored thereon instructions that when executed by processing circuitry of a wireless power receiver cause the processing circuitry to:
 receive, via a receiver coil, a wireless power transfer signal transmitted by a wireless power transmitter,   receive, in a load coupled to the receiver coil, wireless power from the wireless power transfer signal;   send a synchronization message to the wireless power transmitter,   wherein the synchronization message indicates a first time duration of a first time period and a second time duration of a second time period,   wherein the first time period corresponds to a period of foreign object detection and the second time period corresponds to a period of wireless power transfer   wherein the first time period and the second time period are part of a repeating time interval; and   adapt loading of the wireless power transfer signal such that the load is reduced during the first time period,   and, during the first time period:
 receive an electromagnetic test signal from the wireless power transmitter, and 
 communicate a measured parameter to the wireless power transmitter, wherein the measured parameter comprises an indication of power received by the wireless power receiver during the first time period. 
   
     
     
         16 . The non-transitory computer readable medium of  claim 15 , wherein the measured parameter is used by the wireless power transmitter to detect the presence of a foreign object. 
     
     
         17 . The non-transitory computer readable medium of  claim 15 , wherein the non-transitory computer readable medium further comprises instructions which cause the processing circuitry to, during the first time period:
 continuously measure power provided to the load, and   if the measured power is below a preset power level, request a longer time duration for the first time period.   
     
     
         18 . The non-transitory computer readable medium of  claim 15 , wherein the non-transitory computer readable medium further comprises instructions which cause the processing circuitry to, during the second time period:
 continuously measure power provided to the load, and   if the measured power is above a preset power level, request a shorter time duration for the first time period.   
     
     
         19 . The non-transitory computer readable medium of  claim 15 , wherein the non-transitory computer readable medium further comprises instructions which cause the processing circuitry to disconnect the load during the first time period such that a received power level is reduced during the first time period. 
     
     
         20 . The non-transitory computer readable medium of  claim 15 , wherein the non-transitory computer readable medium further comprises instructions which cause the processing circuitry to:
 communicate a request for first time duration and the second time duration, and   receive a response indicating the first time duration and the second time duration as determined by the wireless power transmitter.