A Bidirectional Symmetrical C4LC-DCX Resonant Converter With Power Limitation Capability

Abstract

To achieve the maximum efficiency of resonant converter under wide voltage conversion gain range, two stage conversion, which adopts the resonant converter operating at resonant frequency to work as a dc–dc transformer (DCX) in isolation stage, is a preferred solution. This article proposes a bidirectional C4LC resonant converter to work as a DCX. The structure of the topology is totally symmetrical, and two auxiliary inductors are used to achieve full load range zero-voltage-switching (ZVS) for all the power switches under bidirectional power flow. Unlike conventional ZVS analysis, the ZVS of the proposed converter is analyzed with considerations of all the switch junction capacitors and load. The clamping diodes are also combined in the topology which can help achieve natural power limitation in case of overload and limit the startup current. Even though four inductors and one transformer are illustrated in the topology, all these magnetic components can be simplified and manufactured with one external inductor and one conventional transformer. Meanwhile, the converter operates at a fixed frequency and adopts the synchronous pulsewidth modulation (PWM) modulation, which can achieve constant voltage gain and automatically change the power direction without synchronous rectifier (SR) current detection. Finally, the experimental results from a 1-kW prototype verify the effectiveness of the proposed converter.