A High Efficiency On-Board Battery Charger with Unity Input Power Factor

This paper presents several valuable techniques in the development of on-board type battery chargers for electric vehicle (EV) applications. Selection guidelines for power stage topologies for the charger power converters are given. One such converter system has been designed, constructed and tested, which employs a ZCS boost converter with power factor correction (PFC) followed by an asymmetrically controlled ZVS-HB dc-dc converter. Optimisation of the charge profile is discussed. The steady-state duty cycle of the dc-dc converter is controlled to stay at its possible maximum value to improve the performance of the dc-dc converter. A minimum-power-level active preload circuit has been designed for circuit protection, improving reliability of the charger significantly. Measurements on the prototype have shown that the charger features high efficiency, unity power factor, small size and high reliability.