A high power-factor lithium-ion battery charger with series-input parallel-output dual bridgeless single-stage resonant conversion circuit

This study realizes a high power-factor lithium battery charger which integrates a bridgeless boost-type power-factor-correction converter and a full bridge LLC resonant circuit to constitute a single-stage topology. The developed lithium battery charger is featured with high power-factor, current and voltage stresses reduction on components by introducing a pair of converters using series-input and parallel-output mechanism. The developed battery charger has the following advantages: (a) bridgeless structure reducing circuit losses; (b) resonant technique usage furnishing power switches with soft-switching; (c) constant current (CC) and constant voltage (CV) charging power regulation with frequency modulation scheme simplifying the trigger circuit complexity; (d) series-input and parallel-output dual converters topology sharing current, voltage stresses, and reducing the component rating; and (e) paired interleaved PFC (power-factor-correction) operation sharing current loading and thus increasing charging battery size. Finally, a prototype 2 kW battery charger with 220 V input voltage is implemented and realized. The experimental measurements reveal that the full load efficiency can reach 88% while the power factor exceeds 0.99. In the modulating charging power range, the maximum conversion efficiency can reach to 92%.