Patent ID: 10879744

Abstract:
A wireless power transfer system includes a power receiver (105) comprising a coil (107) for extracting power from an electromagnetic signal generated by a power transmitter (101). A load controller (305, 309) disconnects a load (303) during a foreign object detection interval and a power controller (307, 311) transmits power control messages reflecting a difference between an induced signal level and a reference level. A message transmitter (307, 313) transmits a predetermined loading indication for the reference level to the power transmitter (101) indicating a predetermined amount of power being extracted from the electromagnetic signal by the power receiver (105) when the load is disconnected and the induced signal is at the reference level. The power transmitter adapts the power level of the electromagnetic signal in response to the power control messages and a foreign object detector (207) performs a foreign object detection in response to a comparison of the power level of the electromagnetic signal and the predetermined loading indication.