US Patent 8228027 Wireless power transmitter with multilayer printed circuit

A wireless transmission system having a transmitter and receiver is described. In one embodiment, the transmitter includes an electronically-controlled switch controlled by a first pulse width modulation control circuit, the switch configured to pull current through a first inductor when the switch is closed, the first pulse width modulation control circuit outputting a PWM output signal to control the switch. A first feedback signal obtained from a control input of the switch. A second feedback signal obtained from a terminal of the inductor, wherein a control feedback signal is computed, at least in part, as a difference between the first feedback signal and the second feedback signal is provided to the first pulse width modulation control circuit. In one embodiment, the receiver includes a second pulse with modulation controller, the second pulse width modulation controller controlling the receiver switch to deliver a desired power from the receiving coil to a load.