Variable CLLC Topology Structure Technique for a Bidirectional on Board Charger of Electric Vehicle

The bidirectional onboard charger (OBC) in electric vehicles enables energy transfer between the grid and battery. CLLC resonant converters have the advantage of high efficiency, often acting as a DC/DC converter for the OBC. In this work, the forward and reverse output power capability of the CLLC topology is analyzed. It is found that the forward and reverse output power capability of the CLLC converter is asymmetric, which makes it difficult to fully meet the application requirements in OBCs. Therefore, this paper proposes a CLLC resonant converter with a modified half-bridge and full-bridge structure that can achieve forward 6.6-kW and reverse 3.3-kW power conversion. The simulation and prototype results confirm the proposed solution.