Research on Current Sharing Characteristics of 2-Phase 90° Interleaved Parallel LLC Resonant Converter Based on Variable Resonant Capacitor

This paper proposes a novel approach. To address the issues of imbalanced 2-phase resonant currents and output currents in traditional 2-phase parallel LLC resonant converters, as well as the excessive output current ripple caused by the conventional 2-phase 180° interleaved current-sharing method. Specifically, a small variable resonant capacitor was parallel across each of the two resonant capacitors in the 2-phase LLC resonant converter, and a 2-phase 90° interleaved current sharing strategy is adopted. This method integrates the advantages of the adjustable resonant capacitor and 90° interleaved current sharing. Variable resonant capacitors are utilized to adjust the slightly mismatched 2-phase resonant tanks to a symmetrical state, thereby achieving current sharing in the converter and enhancing its efficiency. On the other hand, the 2-phase 90° interleaved current sharing enables the 2-phase output current ripples to be temporally offset and mutually cancelled, effectively reducing the total output current ripple. This, in turn, decreases the required output filter capacitance for the 2-phase LLC resonant converter and increases the power density of the system. To thoroughly investigate the working principles and current sharing characteristics of this novel converter, detailed theoretical analyses, circuit simulations, and experimental prototype testing were conducted. The results demonstrated the rationality, effectiveness, and practicality of the proposed scheme.