Research on Current Sharing Method of Two-phase Parallel Sigma Converter

Abstract

LLC resonant converter has been widely applicated due to its advantages over other converters. Multiphase parallel LLC resonant converter is necessary in low voltage and large current condition, however, there is a difficulty lying in current sharing. The small tolerance in the resonant tank may cause the larger current imbalance of the multi phases. This paper proposes a control strategy for parallel LLC resonant converter based on sigma converter regulated by PWM controller, which can solve load-sharing problem. The current sharing of each phase is achieved by balancing the output current of Buck. Moreover, LLC-DCX (DC Transformer) of each phase handles most of the energy, the high efficiency is guaranteed. A 200W two-phase parallel sigma converter is given, the simulation results show that the proposed control method can reduce the imbalance of output current significantly within the full load range, verifying the current sharing control strategy effective.