High efficiency LLC DCX battery chargers with sinusoidal power decoupling control

With the sinusoidal charging scheme, the large dc link capacitance of the on-board battery charger can be reduced significantly. However, the variable charging current together with the wide battery voltage range imposes serious challenge to maintain high efficiency throughout the whole charging procedure. This paper proposes a LLC dc-dc transformer (DCX) battery charger solution to improve the efficiency over the full battery voltage range. Furthermore, on the basis of the topology, a sinusoidal power decoupling control scheme is proposed to realize the front-end PFC and sinusoidal output current at the battery side. A 1 kW battery charger prototype was built to verify the benefits. For a battery voltage range from 64 V to 84 V, the efficiency of the proposed charger maintains above 95.8% and the peak efficiency is 96%. The dc link voltage ripple is only 12 V with a 22 μF film bus capacitor, which is reduced by 97% compared with the conventional dc charging scheme.