An isolated DC/DC converter with reduced number of switches and voltage stresses for electric and hybrid electric vehicles

This paper proposes an isolated DC/DC converter to serve as an auxiliary power supply in electric and hybrid electric vehicles (EVs/HEVs), delivering power from high voltage (HV) dc bus to 12 V loads. A DC/AC circuit with a 3:1 voltage step-down ratio is proposed to serve as the front-stage circuit of the converter. Based on the proposed DC/AC circuit, an isolated DC/DC converter is proposed with a post-stage synchronous rectifying current doubler circuit. Compared with full-bridge, half-bridge, push-pull and flyback converters, the advantages of the proposed converter include: 1) the voltage stresses on HV-side switches are reduced to 2/3 of the input voltage; 2) the voltage stress on transformer is reduced to 1/3 of the input voltage; 3) reduced transformer turns ratio; 4) soft-switching capability, high efficiency and simple control. The operation principles, soft-switching analysis, simulation verifications, and experiment results of a 1 kW hard-switching prototype based on silicon carbide (SiC) MOSFETs on the HV side are provided.