Design and implementation of a digitally-controlled LLC resonant converter for battery charging applications

In this paper, a digitally-controlled LLC resonant converter is developed for LEV battery charging applications. LLC resonant converter boasts the advantages of high efficiency and wide input voltage range; therefore is a suitable candidate for medium power battery charger. To enhance the performance of the developed battery charger, five-step constant current (CC) charging method is implemented in the proposed digital controller. Experimental results show that the proposed charger can successfully realize the five-step CC charging algorithm, and the measured conversion efficiencies of the designed LLC resonant converter are all higher than 88% under all output voltage and load conditions.