Resonant Capacitor Design with Small Leakage Current in Non-Isolated SRC for High Power Density in On-Board Charger of Electric Vehicles

An isolated LLC resonant converter is generally adopted as the DC/DC topology in on-board battery charger (OBC). However, since it has the transformer that occupies the largest volume in wide-range output voltage, there is a limit to reducing its volume of DC/DC stage in OBC. To overcome it, non-isolated series-resonant converter (SRC) without the transformer is proposed in this paper. However, in non-isolated SRC, since Y-capacitors in AC input and DC battery output in order to reduce electromagnetic interference (EMI) are integrated in parallel, they appear to be a large value. It may cause large common mode (CM) leakage current. Therefore, CM voltage is analyzed, and the design to reduce the CM leakage current in DC/DC topology is researched based on analyzed CM voltage in this paper.