The Transactions of the Korean Institute of Power Electronics (전력전자학회논문지)

The Korean Institute of Power Electronics (전력전자학회)
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High-Efficiency and High-Power-Density 3-Level LLC Resonant Converter

고효율 및 고전력밀도 3-레벨 LLC 공진형 컨버터

  • Gu, Hyun-Su (School of Electrical Eng., Kookmin University) ;
  • Kim, Hyo-Hoon (Network Access Business Unit, Technical support, FAE, Pulse Electronics) ;
  • Han, Sang-Kyoo (POESLA, School of Electrical Eng., Kookmin University)
  • Received : 2018.02.01
  • Accepted : 2018.03.14
  • Published : 2018.06.20
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Abstract

Recent trends in high-power-density applications have highlighted the importance of designing power converters with high-frequency operation. However, conventional LLC resonant converters present limitations in terms of high-frequency driving due to switching losses during the turn-off period. Switching losses are caused by the overlap of the voltage and current during this period, and can be decreased by reducing the switch voltage. In turn, the switch voltage can be reduced through a series connection of four switches, and additional circuitry is essential for balancing the voltage of each switch. In this work, a three-level LLC resonant converter that can operate at high frequency is proposed by reducing switch losses and balancing the voltages of all switches with only one capacitor. The voltage-balancing principle of the proposed circuit can be extended to n-level converters, which further reduces the switch voltage stress. As a result, the proposed circuit is applicable to high-input applications. To confirm the validity of the proposed circuit, theoretical analysis and experimental verification results from a 350 W-rated prototype are presented.

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References

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