High-Efficiency Wide Range AC/DC Converter using Mode Transition of Six-Arm LLC

Abstract

This paper proposes an LLC type AC/DC converter to achieve high efficiency for wide input voltage range. The proposed converter has four operating modes with different voltage gain characteristics depending on the ON/OFF state of the six switches. The proposed system achieves a wide range of voltage gain by switching between different operating modes. Consequently, the proposed system reduces the magnetizing current by designing a narrow voltage gain in each operating mode. Moreover, the proposed control method achieves power factor correction control of the input current and smooth transition between different operating modes. This paper analyzes the operation and voltage gain characteristics of the proposed converter. A design method to reduce the magnetizing current and the mode transition method is also explained. Based on the experimental results on a 200 W prototype, the basic operation of the proposed system is confirmed in the input voltage range of 100 V to 240 V. Furthermore, the total harmonic distortion (THD) of the input current up to the 40th order of the fundamental frequency is less than 5% across the entire input voltage range. The efficiency of the proposed system is more than 92.5% across the entire input voltage range.