Efficiency analysis of a new lossless passive snubber for electric vehicle applications

Abstract

Power converters are used as Power Factor Correction (PFC) circuits for Electric Vehicle (EV) battery chargers. Snubber circuits are inevitable to increase power conversion efficiency, reduce switching losses and Electro Magnetic Interference (EMI) and offer safe operating range for a switch. Amid diverse kinds of snubber circuits, passive snubbers are ideal because of their simplicity and robustness. They can provide soft switching conditions without using extra switch. Consequently, the requirement of complicated gate drive and control circuit is eliminated. In this paper, a front end AC-DC PFC converter with a simple lossless passive snubber circuit is presented. The proposed lossless passive snubber helps the main switch to attain Zero Current Switching (ZCS) condition at turn on and Zero Voltage Switching (ZVS) condition at turn off instants, respectively. The proposed converter is analyzed theoretically with the equivalent circuits explaining the modes of operation. The simulation results at an output power of 1.5 kW load are presented to validate the feasibility of the proposed passive snubber. Even though the switch current stress is reduced to a greater extent some voltage stress is still present. The proposed PFC converter can achieve a Power Factor (PF) of 0.97 with Total Harmonic Distortion (THD) of 4.5%. The efficiency of the proposed circuit is calculated as 94% over wide operating range.