A Unified Common Inductor and Common Capacitor Current Sharing Method for Multiphase <i>LLC</i> Converter
Zhifeng Sun, Qin Wang, Qunfang Wu, Lan Xiao, Jinbo Li, Zhitian Liu, Junlin Zhu
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 when dealing with multiple resonate parameters mismatches of multiphase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converters. To solve this problem, this article proposes a unified common inductor and common capacitor scheme. First, 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 multiresonant parameters are mismatched, which will cause the one-phase to bear more power, even overpowered and damaged. To realize a better current sharing of multiphase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> modules, a unified common inductor and common capacitor method is proposed in this article, where the series resonant inductors and resonant capacitors in each <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> 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 480 W 24 V two-phase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> 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.