A novel hybrid soft switching full-bridge PWM and full-bridge LLC converter for on-board battery charger applications

Abstract

This paper introduces a novel hybrid converter utilizing a full-bridge soft switching and full-bridge LLC converter. In the proposed topology an additional switch and a diode are adopted in the secondary side of the full bridge converter to achieve the ZVZCS of all the primary switches and rectifier diodes, and to eliminate the circulating current. In addition, the duty cycle loss can be minimized by minimizing the leakage inductance value of the transformer since the soft switching can be achieved regardless of it. The hybrid structure makes it possible to deliver the power to the secondary during the whole switching period, to reduce the size of the output filter and to improve the efficiency. The proposed topology is suitable for the applications such as on-board chargers for electric vehicles and high power dc-dc converters. A 6.6-kW prototype converter was implemented and a maximum of 97.5% efficiency was obtained.