Interleaved LCLC Resonant Converter With Precise Current Balancing Over a Wide Input Voltage Range

An interleaved LCLC resonant converter with accurate current balancing performance over a wide input voltage range is proposed. Resonant tank components have slight tolerances that can unbalance load sharing between paralleled phases. Because of the steep voltage gain curve of the LCLC resonant tank, most conventional current sharing approaches might not be effective. In the proposed converter, the impedances of the resonant tanks are matched by a switch-controlled capacitor (SCC) that is in series with the resonant capacitor resulting in precise load current balancing between phases. The impact of various unbalanced situations on the interleaved LCLC resonant converter is investigated, a minimum operating angle for the SCC circuit is identified, the basic accuracy of SCC current balancing via digital control is investigated, and a control strategy is proposed to perform the current sharing. Computer simulation results and experimental results from a GaN-based prototype validate the performance of the proposed interleaved LCLC converter with precise current sharing over a wide input voltage range from 250 to 400 V. Using enhancement mode GaN and benefiting from the interleaving feature, a high conversion efficiency is achieved on a two-phase 1 kW LCLC converter with peak efficiency of 96.7%.