A Wide Gain Range LLC Resonant Converter Based on Reconfigurable Bridge and Asymmetric Resonant Tanks

In wide voltage gain range applications, it is demanding to optimize the design of the conventional frequency modulated LLC resonant converter. In this paper, a novel reconfigurable LLC resonant topology is customized to mitigate this design challenge. On the primary side, six MOSFETs are utilized to formulate a reconfigurable inverter bridge. This bridge exhibits six different operation modes. Those operation modes enable a wide voltage gain range with a narrow switching frequency span. Furthermore, two asymmetric LLC resonant tanks with different turns ratios are deployed to further squeeze the switching frequency range. Zero-voltage switching is realized on all MOSFETs during all six modes. The conduction loss is reduced due to the reduced circulating current in each resonant tank. High efficiency and narrow frequency range over a wide voltage gain range are well achieved. The operating principles, design considerations, voltage gain analysis, and key experimental results are presented. A 1 kW laboratory prototype is built to verify the effectiveness of the proposed concept. The prototype converts a 390V input to an 80-420V output. A 97.42% peak efficiency is reported.