A three-phase current-fed push-pull DC-DC converter with active clamp for fuel cell applications

In this paper a new active-clamped three-phase current-fed push-pull DC-DC converter is proposed for high power applications where low voltage high current input sources such as fuel cells are used. The proposed converter has the following features; active clamping of the transient surge voltage caused by transformer leakage inductances, natural ZVS turn-on of main switches using energy stored in transformer leakage inductor, small current rating and ZVZCS of clamp switches, no additional start-up circuitry for soft starting due to the operating duty cycle range between 0 and 1, ZCS turn-off of rectifier diodes leading to negligible voltage surge associated with the diode reverse recovery. Experimental results on a 5kW laboratory prototype are provided to validate the proposed concept.