Power converters having reduced body diode conduction loss, reduced
reverse recovery loss and lower switching noise, among other benefits,
have a resonant capacitor Cr connected across an unfiltered output. The
resonant capacitor Cr resonates with the leakage inductance Lk of the
transformer. The resonant capacitor and leakage inductance are selected
such that 1/2 a LC resonance period is equal to an ON time of each
secondary switch S1 S2. The resonance provides zero current switching for
secondary switches S1 S2, eliminates zero body diode conduction during
dead times, and eliminates reverse recovery losses in the secondary
switches. The present invention is applicable to many different circuit
topologies such as full bridge, active clamp forward, push-pull forward,
and center-tap secondary. The present converters provide high energy
conversion efficiency and high frequency operation.