Si and GaN Devices in Quasi Resonant Flyback converters for Wall Charger Applications

The Gallium Nitride (GaN) power switches may offer significant improvement in quasi resonant (QR) Flyback converters, e.g. an enhanced conversion efficiency and reduced volume. This work investigates the performance of Silicon superjunction (SJ) MOSFET and GaN devices exploited in a QR Flyback topology. Firstly, the QR converter design has been performed by considering the characteristics of a SJ MOSFET device as well as the passive elements and the related PWM controller. After that, a level shifter has been adopted to carry out the analysis with a GaN device. The level shifter provides the proper gate voltage supply, thus avoiding damage and device failure due to unadapt driving conditions of the device. The experimental results have shown a performance improvement in comparison to the power SJ MOSFET, with an increase in the efficiency (0.8%) due to the reduction of the switching power losses, despite the converter has not been optimized for the GaN power switch. The converter has not been optimized for the GaN in order to dispel any doubt about the fact that any efficiency improvement is obtained only thanks to the GaN.