Soft switching active snubbers for dc/ac converters

A soft switching active snubber is proposed to reduce the switching losses of the IGBT in a DC-AC power converter. The active snubber provides zero-voltage switching for the IGBTs, thereby reducing the high turn-off losses due to current tailing. The proposed active snubber uses two auxiliary switches in order to recover the switching energy during turn-off. The snubber is itself an inverter leg, and is comprised of two snubber capacitors for zero-voltage switching, two switches with anti-parallel diodes and a common snubber inductor. The auxiliary switches are operating at zero-current at turn-on and zero-voltage at turn-off. The topology presented here bears some resemblance to the resonant snubbers proposed in the literature. However, this topology is more general and encompasses the resonant topology. The paper provides operating principles analysis and sample waveforms for the active snubber