A new quasi-resonant inverter with two-way short-circuit switch across a resonant capacitor

Two frequencies are often used in induction heating, that is, a lower frequency f_L is for preheating and a higher frequency f _H is for main heating in order to decrease thermal stress. In this case, each of f_H and f_L is generated by the different inverter, and f_H approximately equals several times to ten times of f_L. The authors propose a new quasi-resonant inverter that has a two-way short-circuit switch across the resonant capacitor. The proposed inverter has features that its operating frequency is adjustable and the frequency range is so wide that the higher frequency can be ten times as much as the lower frequency. It is considered that the output current has only a fundamental wave by properly manipulating the shorting time of the resonant capacitor even though the output current is not a sinusoidal wave