A Unified Common Inductor and Common Capacitor Current Sharing Method for Multiphase LLC Converter

Abstract

The common inductor and common capacitor current sharing technologies with excellent current sharing capabilities and low-cost have attracted a lot of attention in recent years. However, these methods have certain limitations. To solve this problem, this paper proposes a unified common inductor common capacitor scheme. Firstly, the existing common inductor and common capacitor methods are reviewed. Based on the first harmonic approximation (FHA) analysis method, the limitations of these schemes are analyzed, and we find that the current sharing performance is not well when the multi-resonant parameters are mismatched, which will cause the one-phase to bear more power, even over-powered and damaged. To realize a better current sharing of multi-phase LLC modules, a unified common inductor common capacitor method is proposed in this article, where the series resonant inductors and resonant capacitors in each LLC converter are connected in parallel. The current sharing performance of the proposed method is analyzed by the FHA analysis method, and the proof-of-concept prototype with a 480W 24V two-phase LLC converter was built to verify the effectiveness of the proposed method. Simulation and experimental results show that the current sharing error of the proposed method is 2.1% under half load and 0.9% under full load.