Performance Characteristics of High Power Density Battery Charger for Plug-In Micro EV

Micro EVs are attracting attention as a personal mobility for short distance travel such as shopping and delivery service in areas such as isolated islands and depopulated areas without rapid charging facilities and are expected to be widely used in the future. In general, the micro EV has a battery charger mounted on the vehicle so as not to require a special charging spot. In order to reduce the weight of the micro EV, it is also required for the on-board charger that the charging time is short and being compact and lightweight as well as being able to charge from a household AC outlet. The conventional charger is a two-stage converter system combining a power factor correction circuit (PFC) and a dc-dc converter, which has problem that makes the size of the charger larger and the efficiency lower. Therefore, a method to control the input current and charging power to the battery with a single dc-dc converter for use as a charger of micro EV battery has been proposed and published in our previous study and it has been demonstrated that this method makes it possible to dramatically improve the power density and improve the power conversion efficiency which are important for miniaturization of the micro EV. At that time, the primary side of the single-stage converter charger is a full-bridge circuit, however, in order to further miniaturize the charger, it is conceivable to adopt a half-bridge circuit which is popular in the dc-dc converter into the ac-dc converter. This paper presents the comparison of performance characteristics and power density of chargers for each case of the single-stage converter using the full-bridge circuit on the primary side, the single-stage converter using the half-bridge circuit and the conventional two-stage converter. As the results, it is evaluated whether the half-bridge circuit can be applied for the single-stage ac-dc converter.