A novel secondary PWM-controlled interleaved LLC resonant converter for load current sharing

The interleaved LLC series resonant converter (LLC-SRC) is required to fulfill the demand for high power capacity, high power density and high efficiency. However, when interleaved LLC-SRCs in each module are operated at the same switching frequency, load unbalance problem occurs due to the component tolerances of the resonant ranks. In consequence, the reliability of the converter is decreased due to increased secondary current ripple. In order to solve this problem, this paper proposes a novel load current sharing method for the resonant tank gain mismatches in each phase. The proposed load current sharing method can be implemented by controlling the turn-on timing of the secondary synchronous switches. The load current can be shared equally in each module, even if the converters in each phase are operated at the same switching frequency. In order to verify proposed method, the experiments are executed on a 500W prototype.