Development of a WBG-based Transformerless Electric Vehicle Charger with Semiconductor Isolation

This paper presents discussions on the design of Semiconductor-based galvanic isolation (SGI)-based vehicle on-board battery chargers. SGI is a paradigm shift compared to traditional transformer-based solutions by using switched capacitor circuits to realize galvanic isolation. Two major SGI-based battery charger topologies are compared, and a two-stage Totem-pole + SGI dc/dc solution is selected due to higher efficiency. Based on the topology, the touch current (TC) issue is modelled and analyzed, and a buck-boost-based active compensation circuit is proposed with local sensing and control. At last, a 2-kW SGI charger is prototyped and tested, and the efficiency of the dc/dc stage maintains above 98%. With the proposed touch current compensation circuit, the charger meets the safety standards by passing the TC test.