POWER TRANSMITTER UNIT

A power transmitter unit comprises a power transmitting coil and a resonant capacitor that define an LC circuit. A controller defines a power transmission mode of operation and a foreign object detection mode of operation. In the power transmission mode of operation: a power stage provides a potential difference across a first end and a second-end of the LC circuit. In the foreign object detectionmode of operation: for a recuperation time interval, the power stage provides a potential-difference across the first end and the second-end of the LC circuit that has the opposite polarity to the current through the power-transmitting coil; after expiry of the recuperation-time-interval, the first end of the LC circuit is connected to the second-end of the LC circuit such that the LC circuit isshort-circuited and defines a closed LC circuit; and the controller receives measured-signalling that is representative of an operating parameter of the power transmitter unit. The controller furtherprocesses the measured sign