Modular battery charger for light electric vehicles

Abstract

Rapid developments in energy storage and conversion technologies have led to the proliferation of low- and medium-power electric vehicles. Their regular operation typically requires an on-board battery charger that features small dimensions, high efficiency and power quality. This paper analyses an interleaved step-down single-ended primary-inductor converter (SEPIC) operating in the discontinuous conduction mode (DCM) for charging of battery-powered light electric vehicles such as an electric wheelchair. The required characteristics are achieved thanks to favourable arrangement of the inductors in the circuit: the input inductor is used for power factor correction (PFC) without additional elements, while the other inductor is used to provide galvanic isolation and required voltage conversion ratio. A modular interleaved structure of the converter helps to implement low-profile converter design with standard components, distribute the power losses and improve the performance. An optimal number of converter cells was estimated. The converter uses a simple control algorithm for constant current and constant voltage charging modes. To reduce the energy losses, synchronous rectification along with a common regenerative snubber circuit was implemented. The proposed charger concept was verified with a developed 230 VAC to 29.4 VDC experimental prototype that has proved its effectiveness.