Improved gate driver for a 13.56 MHz resonant inverter

The subject of this paper is the operation of a half-bridge resonant inverter at 13.56 MHz, using the sinusoidal driver technique. It has been shown that such a class-D inverter can achieve efficiencies of over 90% at medium power levels (100-500 W). However, it has been known that standard package (TO-220) switching devices cannot operate at this frequency and that severe ringing,can cause the efficiency to drop to below 50% at a limited output power. This paper discusses the issue of using standard package devices at such high frequencies and proposed an alternative solution for driving the switching devices. A prototype inverter was built according to this solution, using MOSFETs in TO-220 package, and an efficiency of 81% was recorded at an input power of 320 W.