Zero voltage and zero current switching full bridge PWM converter using secondary active clamp

A new zero voltage and zero current switching (ZVZCS) full bridge (FB) PWM converter is proposed to improve the performance of the previously presented ZVZCS-FB-PWM converters. By adding a secondary active clamp and controlling the clamp switch moderately, ZVS (for leading leg switches) and ZCS (for lagging leg switches) are achieved without any lossy components, the reverse avalanche break down of leading-leg IGBTs or the saturable reactor in the primary. Many advantages including simple circuit topology, high efficiency, and low cost make the new converter attractive for high voltage and high power (>10 kW) applications. The principle of operation is explained and analyzed. The features and design considerations of the new converter are also illustrated and verified on a 1.8 kW, 100 kHz IGBT based experimental circuit.