A High Gain Quasi Single Stage LLC Resonant DC/DC Converter with Coupled Inductor and Partial Active Clamp

For low DC input applications such as PV converters, low input voltage causes large conduction losses of the primary side of the isolated front stage DC/DC converter due to the high primary current, which makes the efficiency is difficult to improve. In order to improve the conversion efficiency and optimize the topological structure, a quasi single stage LLC converter with coupled inductor and partial active clamp has been proposed in this paper. This new DC/DC converter can achieve soft switching of all switches and secondary rectifiers. In addition, taking advantage of the coupling of the inductor, the DC voltage gain of the proposed converter has been doubled compared to the conventional full bridge LLC resonant converter voltage. A 250W experimental prototype with 24V-36VDC input and 400VDC output was designed and tested.