Optimal Operation Region of LLC Resonant Converter for On-Board EV Battery Charger Applications

In this study, optimal operation region of a LLC resonant converter is discussed for on-board electrical vehicle (EV) battery charger applications. In the operation mode optimization, wide range output voltage regulation and wide range load condition, which are required lithium-ion battery cells are taken into consideration. The basic operation fundamentals of LLC resonant converter is presented and an analytical comparison for the operations above resonance, below resonance and above-below resonance is presented to evaluate output voltage regulation under very wide range load conditions. In addition, an analytical efficiency comparison is also presented to evaluate operation region effects. The operation and validity of obtained optimization region is tested by a simulation study which has 250-450 V/6 A output rates.