Journal of Power Electronics

The Korean Institute of Power Electronics (전력전자학회)
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Novel central-tapped planar transformer structure with natural current-sharing for LLC resonant converters

  • Cheng Gu (Nation ASIC System Engineering and Research Center, Southeast University) ;
  • Qinsong Qian (Nation ASIC System Engineering and Research Center, Southeast University) ;
  • Dalin Xu (Jiangsu Automation Research Institute) ;
  • Tianhao Tan (Nation ASIC System Engineering and Research Center, Southeast University)
  • Received : 2022.11.16
  • Accepted : 2023.03.30
  • Published : 2023.09.20
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Abstract

Planar transformers have been widely used in isolated power supplies. However, with a large current density, the parallel windings usually cannot share the current evenly. This uneven current-sharing may cause additional winding losses, and damage the performance of the power converter. In this paper, a novel central-tapped planar transformer structure is proposed. Regardless of whether it is in the first half cycle or the second half cycle, the proposed twelve-layer transformer can be simplified as four three-layer transformers connected in parallel. Moreover, there is a "shielding layer" between adjacent three-layer transformers. In addition, the proposed transformer structure is optimized with a symmetrical layer arrangement, and the skin effect and proximity effect can be further reduced. Simulation and experimental tests indicate that the optimized planar transformer can stably provide 476.1 W of output power at a frequency of 1.25 MHz. The peak efficiency of the optimized transformer is up to 99.2%, and there is no obvious hot spot on the PCB board. It is noteworthy that the temperature difference in the secondary windings is less than 5 ℃, which means the current-sharing in the secondary windings works well.

Keywords

Acknowledgement

This study was supported by National Natural Science Foundation of China, 52177172.

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