Power transmitter unit

Abstract

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-detection-mode 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 is short-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 further processes the measured-signalling in order to provide an indication of whether or not a foreign object has been detected.