基于多谐波阻抗模型的CLLC谐振变换器轻载多移相控制分析与设计

CLLC resonant converters have the advantages of bidirectional power transmission, natural soft switching, and wide output voltage range. However, CLLC resonant converters still suffer from the light-load problems of unsatisfying voltage regulation and low efficiency. This paper analyzed the multiple phase-shift control of CLLC converters based on a multi-harmonic impedance model, and designed a dual phase-shift control for light-load operation, which can effectively regulate the output voltage and improve the light-load efficiency. A multi-harmonic impedance model of full-bridge CLLC resonant converter was first established. Based on this model, the light-load voltage gain and root-mean-square (rms) values of resonant currents under multiple phase-shift control were solved, and the effects of different phase-shifts on the light-load output voltage and resonant currents were analyzed. Then, a dual phase-shift control method was designed, achieving reliable voltage gain adjustment and lowering the light-load power loss. Finally, a 21.5V/400V, 200W full-bridge CLLC resonant converter experimental prototype was built. The experimental results demonstrated the accuracy of proposed multi-harmonic impedance model and the effectiveness of designed dual phase-shift control under light-load conditions.