Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters

Cheng Gu; Qinsong Qian; Dalin Xu; Tianhao Tan

Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters

Vol. 23, No. 9, pp. 1298-1306, Sep. 2023

10.1007/s43236-023-00633-z

Central-tapped planar transformer

Current-sharing

LLC resonant converter

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 °C, which means the current-sharing in the secondary windings works well.

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Cite this article

[IEEE Style]

C. Gu, Q. Qian, D. Xu, T. Tan, "Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters," Journal of Power Electronics, vol. 23, no. 9, pp. 1298-1306, 2023. DOI: 10.1007/s43236-023-00633-z.

[ACM Style]

Cheng Gu, Qinsong Qian, Dalin Xu, and Tianhao Tan. 2023. Novel central‑tapped planar transformer structure with natural current‑sharing for LLC resonant converters. Journal of Power Electronics, 23, 9, (2023), 1298-1306. DOI: 10.1007/s43236-023-00633-z.