Boost-integrated LCL resonant converter with high voltage gain

A boost-integrated LCL resonant DC–DC converter is proposed, which is constituted by a full-bridge inverter module, the main transformer and a flyback transformer, resonant unit, and a rectifier module. The primary winding of the flyback transformer is also used as a resonant inductor and a boost inductor to improve the power density and the voltage gain. In order to meet different output environments, the converter can operate in low voltage-gain mode or high voltage gain mode. In low voltage-gain mode, the converter operates in PWM with LCL resonance. In high voltage-gain mode, the converter operates in PWM with boost and LCL resonance, in which boost modulation plays a role before the LCL resonance to increase the output voltage. Compared with the conventional LCL resonant converter, the new converter has higher voltage gain and is more suitable for a wide output range with the same resonant parameters. The operation principles of the proposed converter are clarified. A prototype with 80–140 V output and maximum output current 2.9 A is built, and experimental data shows that the maximum efficiency of the prototype can be 94.5%, verifying the correctness of the theoretical analysis.