Patent ID: 7804697

Claim:
A circuit, comprising: a switching power stage for producing a switched power output at a switching rate and having at least one power switching transistor; a switching control circuit for determining a turn-on time and a turn-off time of the at least one power switching transistor at the switching rate, and having an output for providing a modulated control signal having a modulated rate that is greater than the switching rate, wherein the modulated control signal encodes events according to codes specified by relative timing of transitions of the modulated control signal in multiple periods of the modulated control signal, the events including a turn-on event corresponding to the turn-on time of the at least one power switching transistor; a transformer for coupling the output of the switching control circuit to the at least one power switching transistor, whereby the at least one power switching transistor has a gate that is DC isolated from the switching control circuit, wherein a first winding of the transformer is connected to the switching control circuit; and a demodulator circuit connected to at least one second winding of the transformer and having an output coupled to the gate of the at least one power switching transistor, wherein the output of the demodulator is a gate control signal generated at the switching rate from a control signal received from the at least one second winding at the modulated rate, and wherein the demodulator asserts the gate control signal upon detection of the turn-on event and de-asserts the gate control signal upon detection of another code.