ELECTROMAGNETIC COOKING DEVICE WITH SWITCHING TRANSISTOR

摘要

An electromagnetic cooking device has a resonance circuit composed of a heating coil and a capacitor; an inverter circuit including a switching transistor and a diode connected across the collector and the emitter of the switching transistor in the reverse direction. The resonance circuit and inverter circuit are connected in series across a DC power source. A start-signal generating circuit periodically develops a start pulse signal. A stop-signal generating circuit receives the value of the current flowing through the heating coil as an input signal and develops a stop pulse signal when this value becomes zero. A driving circuit is coupled to the inverter circuit. The start-signal generating circuit and the stop-signal generating circuit receive the start pulse signal and the stop pulse signal as inputs and develop a signal for rendering the switching transistor conductive after the appearance of the start pulse signal and until appearance of the stop pulse signal. As a result the maximum voltage impressed on the switching transistor can be kept to a desirably low level, while the operation is stable and reliable.