A Standard Two Stage On-Board Charger with Single Controlled PWM and Minimum Switch Count

Abstract

A novel two-stage standard battery charger having minimum switch count using a single controlled PWM signal is presented in this article for Electric Vehicle (EV) charging application. The first stage is responsible for AC to DC conversion with power factor correction (PFC) operation that consists of two switches and two diodes. The second stage is a DC-DC converter having a half bridge LLC resonant configuration along with an isolation transformer. The complete charger consists of only four switches and four diodes, which is minimum among the reported literatures. Moreover, unlike a conventional control strategy that requires multiple separate controlled PWM signals for different switches, the new control scheme manages both the PFC operation as well as constant current-constant voltage (CC-CV) optimal battery charging with a single controlled PWM signal. The detailed operation and its modeling are presented in this article. A 470 W scaled down laboratory prototype is built to validate the proof of concept. The proposed charger is tested to charge a battery set of 24 V, 30 Ah using CC-CV logic with a maximum efficiency of 97.6%. The prototype is also tested with resistive load at its rated power and dynamics results are captured. A TMS320F28335 DSP board from Texas Instrument is used for implementing the control technique. © 1972-2012 IEEE.