A zero-voltage and zero-current switching three-level DC-DC converter with secondary-assisted regenerative passive snubber

An energy-recovery snubber, developed previously for full-bridge PWM phase-shift converters, is inserted in the secondary side of the transformer of a three-level converter. As a result, ZVS is obtained for the outer power switches and ZCS for the inner switches. The voltage on the rectifier diodes is clamped at a reasonable voltage, parasitic secondary ringing being avoided. The energy of the snubber is fully transferred to the load. Using a three-level converter, the voltage stresses on both power switches and rectifier diodes are reduced at half of that on their counterparts in full-bridge converters. Experimental results prove the expected high-efficiency of the proposed converter.