High-efficiency on-board battery charger with transformer isolation, sinusoidal input current and maximum power factor

The paper concerns a battery charger that has been developed for use in a battery powered electric road vehicle. The object is to charge the 144 V traction battery directly from the 220 V supply by drawing sinusoidal current at the input, to obtain, a high efficiency and to have transformer isolation from the supply. To achieve this, the rectified 220 V supply is chopped up to 500 V by a DC to DC convertor and transformed to the necessary voltage for battery charging by using a high-frequency self-oscillating inverter with magnetic feedback. The rectified output of the inverter charges the battery. The step-up chopper controls the transmitted power to the battery and ensures a sinusoidal line current. A detailed description of the power circuit is given and the capabilities of the complete system are proved by extensive measurements.