Differentiated-Gain-Regulation-Based Current Balancing Control for Multi-Phase Interleaved LLC Resonant Converters

Abstract

In multiphase LLC resonant converters, the component parameter tolerance of the resonant tanks will lead to discrepancies in voltage gain, resulting in imbalanced output current. In this paper, the principle and mechanism of current imbalance among multiphase LLC resonant converters are discussed through the state plane analysis. Based on the limitation analysis for the switch-controlled capacitor and phase shift modulation, an improved differentiated-gain-regulation (DGR)-based current balancing strategy is proposed by adding external circuits to compensate for parameter differences, assisted by the voltage regulating method. The essential principle is to initially increase the gains of light-load phases with the switch-controlled capacitor. And for phases with heavy loads, the phase shift modulation is used for suppressing gains to avoid control instability caused by the introduction of switch-controlled capacitor. It would not affect the soft switching characteristics of LLC resonant converters. Finally, the hardware-in-the-loop based experiment results verify the correctness and effectiveness of the proposed method and analysis.