Introduction

Power supply designers face many challenges in designing more efficient and cost-effective power supplies. Efficiency is a major consideration in designing switching power supplies. Many factors in the design process such as the input filter capacitance, transformer core geometry and construction, output rectifier, and switching device etc., affect the efficiency of switching power supplies. Among the losses all components generate, switching device losses occupy about 30. Hence, selecting MOSFETs with optimum efficiency and high reliability is very crucial in power supply design. This application note compares the key characteristics, power losses, and efficiency of the new QFET and a conventional MOSFET in a 60 watt flyback converter operated at 180 to 265 VAC.