A Bidirectional Switch Based Half-Bridge Series-Resonant Converter Operating in DCM and CCM

Abstract

Conventional asymmetric half-bridge LLC converters have been attractive in on-board battery charger applications because of their simple control and structure. However, their usage with asymmetric PWM is limited due to the large dc-offset current and increased conduction loss. In this paper, we propose a bidirectional switch based half-bridge series-resonant converter. Proposed converter features a small number of power components, inherent zero voltage switching capability, and a zero dc-offset current. The combination of the half-bridge circuit and the bidirectional switch generates symmetric resonant current with the zero dc-offset current regardless of the duty cycle variation. When the output voltage is high, it operates in discontinuous conduction mode (DCM). When the output voltage becomes low and under heavy load condition, it naturally enters in continuous conduction mode (CCM), and so it provides low conduction loss. A 1.65-kW prototype of the proposed converter has been built and tested to demonstrate its circuit design.