Analysis of a resonant converter with two transformers and voltage doubler rectifier

This study presents a resonant converter with two transformers and a voltage doubler rectifier to achieve zero-voltage switching (ZVS) turn-on for power switches, zero-current switching (ZCS) turn-off for rectifier diodes at full load, less transformer secondary winding and less voltage stress of the rectifier diodes. Based on the resonant behaviour of the resonant inductor and resonant capacitor, power switches and diodes can be turned on or off at ZVS or ZCS. Thus, the switching losses of MOSFETs and reverse recovery losses for the diodes are reduced. For high-power applications, the primary sides of two transformers are connected in series to reduce the voltage stress on the primary windings. The voltage doubler rectifier is adopted in the secondary side. Only one secondary winding set per transformer is needed and the voltage stress of rectifier diodes is clamped to the output voltage. Thus, the schottky diodes can be adopted in the output side to reduce the conduction losses. The proposed converter is suitable for high-efficiency applications such as industrial power supply unit, LCD-TV power unit and power supply unit of server and data storage systems. Laboratory experiments with an 840 W (24 V/35 A) prototype, verifying the effectiveness of the proposed converter, are described.