A novel approach to design EV battery chargers using SEPIC PFC stage and optimal operating point tracking technique for LLC converter

In this paper, a plug-in electric vehicle battery charger is proposed based on SEPIC PFC and LLC topologies. In addition, a new approach in introduced to actively control the dc link voltage and track the maximum efficiency point of a LLC converter over the wide voltage range of the high voltage battery pack. Comprehensive circuit modeling and loss analysis at maximum efficiency point of LLC converter are carried out. A 3.3 kW charger, charging the Li-ion battery with an output voltage range of 100 V to 420 V from variable dc link voltage, is designed and simulated. In comparison to conventional approaches, the LLC stage demonstrates 4.4% efficiency improvement at the heaviest load condition and 16.5% efficiency improvement in the lightest load condition.