A novel active-current-sharing method for interleaved resonant converters

This paper presents a novel active load-current-sharing control of paralleled or interleaved isolated series-resonant converters. In the proposed control method, the output voltage is regulated by variable-frequency control of the converters' primary switches, while a delay-time control is used to control secondary-side switches provided in place of diode rectifiers to correct load-current imbalance between the converters that is caused by their mismatched components. By independently controlling the turn-off delay time of the secondary switches of each individual converter with respect to the zero-crossing instants of the corresponding resonant-tank current, excellent current balancing can be achieved. The evaluation of the proposed control method was performed on a 1.8-kW prototype that was implemented by two interleaved 900-W series-resonant LLC converters operating from a 240-450-V input-voltage range and providing a 13.8-V output.