A Novel LLC Converter With Ultrawide Gain Range

To meet the charging requirements of the next-generation powertrain architecture (1200V) and current electric vehicles (400V and 800V), a novel LLC resonant converter is proposed in this paper. By adopting a stacked switch structure on the inverter side and configurable output capacitors on the rectifier side, the voltage stress on the inverter side switches is reduced, and an ultra-wide voltage regulation range is achieved. Unlike the traditional PFM control strategy, the resonant tank works at a fixed-frequency within two operating modes and the output switch uses PWM control(FF-PWM) to ensure that the proposed topology maintains high efficiency throughout the output range. The operating principle, capacitors balance and ZVS performances are analyzed in this paper. Finally, a prototype with 400V input and 400V~1600V output is verified by simulation. The highest working efficiency reaches 98.75% when the load is 400W and the output voltage is 750V. The control strategy proposed in this paper shows superior working efficiency than PFM+PWM control strategy.