Optimal trade-off between hard and soft-switching to achieve energy saving in industrial electric vehicles

DC/DC battery chargers used in industrial electric vehicle applications are designed to be size, weight and power efficient. Wide bandgap (WBG) devices which enable high frequency operations help reduce size of magnetics as well as the converter volume achieving better efficiencies compared to Si based solutions. It has not been often discussed in literature but in case of battery chargers the overall saved energy becomes a better performance indicator than the efficiency at rated power alone. This is due to their peculiar charge/discharge characteristics. In this paper, the design of a GaN (Gallium nitride) converter for an industrial battery charger application is studied. An optimal design procedure aiming at optimizing the converter energy utilization efficiency (EUE) over the complete state of charge (SoC) as well as minimizing BOM (Bill of Material) costs due to magnetics is presented in order to highlight the energy perspective. The results show considerable energy savings compared to conventional design methods. Nomenclature - SoC (state of charge), I-ocr (critical battery current), L-r (series inductance), C-oss (device output capacitance), t(r) (rise time) t(f) (fall time),