A Current-Fed LCL Resonant Converter for Wide Output-Voltage Applications

This article proposed a novel current-fed LCL resonant converter with a simple structure by multiplexing inductors and switches for wide output voltage applications. With three different pulsewidth modulation methods, the proposed converter can work at three voltage gain modes, namely high gain (HG), medium gain (MG), and low gain (LG). In HG mode, it has a higher voltage gain than the conventional LCL converter by an extra boost energy storage stage. In MG mode, it operates similarly as a conventional LCL converter. In LG mode, it is equivalent to a flyback converter in discontinuous conduction mode (DCM), which achieves higher efficiency and is easier to be controlled than an LCL converter. In these three modes, all power switches and rectifier diodes can obtain soft-switching performance, increasing the power conversion efficiency. The operating principle, design methodology, and control scheme are explained and verified by a laboratory prototype with 520 W output power, 30-150 V output voltage.