Advantages of Gallium Nitride over Silicon transistors in softswitched Resonant Switched Capacitor Converters

Abstract:
The performance improvements of Gallium Nitride (GaN) over Silicon (Si) devices are analyzed in this paper for softswitched Resonant Switched Capacitor Converters (RSCCs). RSCCs feature high efficiencies and power densities at low voltages. To maintain low losses in high voltage designs, Zero-Voltage Switching (ZVS) is required. There has to be enough energy in the inductor to discharge the parasitic capacitance of the MOSFET to obtain ZVS. However, in these converters, low values of inductance are typically used, therefore, soft-switching is difficult to achieve. The relation between the inductor, its current and the drain-source capacitance will be explained in detail, as it plays an important role in the converter design. GaN devices are a great alternative to Si because of their low parasitic capacitance. To illustrate the advantages of GaN over Si transistors, two step-up RSCC have been implemented for 700 V output and 4.5 kW, one with each technology, reaching efficiencies up to 99.8% with a volume of 56 cm (Exp 3) as the sum of its components.