High efficiency isolated DC-DC converter combining resonant and phase-shifted topologies for electrical vehicle chargers

A novel soft-switching converter combining resonant half-bridge and phase shifted full-bridge configuration is proposed not only to eliminate the issue of the possible MOSFET device damage due to hard-switching under high voltage because the zero-voltage-switching (ZVS) of MOSFETs is ensured even at true zero load, but also to minimize the duty cycle loss and circulating conduction loss since that the current resetting speed of IGBTs in the lagging leg is similar to that of the hard-switching converters. A 6.6 kW hardware prototype has been designed, fabricated and tested to verify the validity and improved performance of the proposed circuit. Experimental results show that the proposed topology is attractive for electrical vehicle on-board charger applications as the unit has demonstrated a maximum efficiency of 98.4% and achieved soft switching for the entire range of output battery charging voltage and current conditions.