An apparatus comprises a bridge coupled between a bias voltage and ground, wherein the bridge comprises a first switch and a second switch connected in series and coupled between the bias voltage and ground and a third switch and a fourth switch connected in series and coupled between the bias voltage and ground, a resonant device coupled to the bridge, wherein the resonant device comprises a fixed capacitance, a gate capacitance and a magnetizing inductance, a transformer coupled to the resonant device, wherein the transformer comprises a primary winding and a plurality of secondary windings.