Autopiloting and measuring the resonant frequency of series resonant converter for induction heating

This article shows the work done to put into action the regulation of frequencies adapted to high resonant frequency power converters destined for induction heating applications. The principle of autopiloting proposed allows the inverter to follow any resonant frequency variations which are due to a variation of the load or to an abrupt change in the resonant circuit. This study also looks at starting problems and gives numerical solutions. The hardware and software control circuit implementation built around an Intel microcontroller is discussed, and experimental results obtained at 5 kW for a frequency between 24 kHz to 40 kHz are given