This paper presents superior performance of 8 kW LLC resonant full bridge dc-dc converter which uses a high frequency transformer for auxiliary power supply in traction applications. The comparison of hard switching and zero voltage switching (ZVS) of a Full bridge dc-dc converter with switching frequency of 100 kHz is provided. Zero voltage switching was achieved by employing the appropriate LLC resonant network. Operating principles are verified by simulations analysis which is supported by experiments on 8 kW laboratory prototype. The converter efficiency curves under both switching conditions are presented as well

Keywords: Zero voltage switching (ZVS), Zero current switching (ZCS), Auxiliary power supply, Soft switching