Wide Range Voltage Gain and High Efficiency Operation of LLC Converter using Two Asymmetric Transformers

This paper proposes a circuit configuration of LLC converter that achieves both wide output voltage gain and high efficiency operation. The primary side of the proposed circuit is composed of six switches to form a bridge circuit and has two transformers with different parameters. Thus, the proposed circuit has six operation modes, those modes realize a wide output voltage gain range. In addition, two different resonant tanks allow a large magnetizing inductor and a small resonant inductor, so that it is possible to design reducing for the circulating current. The validity of the proposed system is verified by built a 1.0 kW prototype with an input voltage of 360V. The proposed circuit shows that an output voltage gain of over 2 can be obtained. In addition, the proposed circuit also exhibits high efficiency characteristics with a maximum efficiency of 96.6%.