A Simplified Onboard Charger Designed for Compact Size Electric Vehicles

This paper presents a simplified design aimed to reducing the cost of on-board chargers for small-size electric vehicles. The proposed charger includes two stages. A front-end converter is utilized, in the first stage, to convert grid AC voltage to DC voltage while receiving a sinusoidal current at nearly unity power factor from the utility grid. In the second stage, a back-end converter which consists of a single active bridge DC-DC converter, is employed to provide galvanic isolation between the utility grid and the battery bank. In addition, the back-end converter is controlled to regulate the charger output voltage to meet the battery bank requirements. The dynamic performance of the proposed charger is verified using the PSCAD/EMTDC software package, demonstrating the successful transition from constant current charging mode to constant voltage charging mode. Furthermore, an experimental scaled-down prototype is implemented to verify the overall performance of the proposed charger.