Foreign object detection circuit for wireless charger

Abstract

In a wireless charging system, a power-transmitting node (TX), has a processor, a memory, a power transmitter for transmitting power wirelessly to a power-receiving node (RX), and a signal receiver for receiving signals from the RX. After the processor detects the presence of a foreign object (FO) during a power-transfer session, the processor places the TX in a protection state. The processor detects whether the FO has been removed using quality factor (QF) values for the TX that the processor measures before and after detecting the presence of the FO, and without requiring any QF values calibrated off-line. The QF values include a QF value measured before the FO is present, a QF value measured just after the TX enters the protection state, and a current QF value that is repeatedly updated as long as the TX remains in the protection state.

Dependencies are inferred from the claim text.