A battery charger with 3-phase 3-level T-type PFC

This paper presents a newly developed 24 V / 3.5 kW output two-stage ac-dc power supply for battery charge application. In this developed two-stage structure, 400 V three-phase three-level T-type PFC ac-dc input stage is followed by an isolated dc-dc buck converter as an output stage. The combination of SiC Schottky Barrier Diodes (SBDs) and Super Junction (SJ) MOSFETs are employed for input stage in order to achieve high switching frequency of operation at lower total semiconductor losses. Employing three-level topology at high switching frequency of 58 kHz contributes considerable volume reduction of magnetic components in the input stage. Two different switching schemes, soft switching (ZVS) with phase-shift control at high operating point and hard switching with on duty control at lower operating point are adaptively employed in the dc-dc output stage in order to maintain high efficiency over wide range of operating point. The operating switching frequency of 65 kHz is chosen for the output stage. As a result, developed two-stage ac-dc power supply achieves the total efficiency of 93.6 % at nominal output power.