Turn-Off Delay-Controlled Bidirectional DC–DC Resonant Converter With Wide Gain Range and High Efficiency

Abstract

Series resonant converter can only operate efficiently within a narrow voltage gain range, which limits the use for battery charging applications. Thus, this article proposes a turn-off delay-controlled bidirectional series resonant (TFD-BSR) converter to extend the voltage gain range and enhance the efficiency. Instead of frequency modulation, the turn-off delay of the corresponding bottom switches is adopted to regulate the direction and amplitude of power flow. First, high peak and low valley voltage gain is obtained at fixed switching frequency. As a result, wide voltage range is extended. Second, the voltage gain is independent of auxiliary and magnetizing inductors, and hence, a large value for the two inductors, which depresses the circulating losses significantly, can be designed just considering zero-voltage switching (ZVS) conditions. In addition, all the active switches can operate with ZVS, which further enhances the efficiency. Operation principles, voltage gain characteristics, ZVS analysis, and design method of the proposed TFD-BSR converter are analyzed in detail. Finally, the feasibility and performance of the proposed converter are validated by simulations and experimental results from a 3.5-kW prototype.