A high-efficiency on-board charger utilitzing a hybrid LLC and phase-shift DC-DC converter

Abstract

A new class of hybrid soft-switching dc-dc converters combining a half-bridge LLC converter and a full-bridge phase-shift modulated converter is proposed for electric vehicle (EV) on-board charger applications. The hybridization allows the converter operating under soft-switching condition in a wide input and output voltage range and from true zero to full load condition. It not only eliminates possible MOSFET damage due to hard-switching under high-voltage low-current condition, but also minimizes the duty cycle loss and circulating current induced conduction loss. The entire on-board charger consists of a power factor correction (PFC) stage and a hybrid dc-dc converter. Both conventional boost and bridgeless PFC converters were implemented to incorporate the proposed hybrid dc-dc converter for a 6.6 kW on-board charger. Hardware prototypes have been designed, fabricated and tested to verify the validity and performance of the proposed circuit. Experimental results show that the proposed topology is attractive for EV onboard charger applications as the design has demonstrated a peak efficiency of 98.4% for the dc-dc stage and 96.1% for the entire on-board charger. The prototype on-board charger has been installed in an EV for field testing.