Frequency controlled induction cooking apparatus

摘要

The invention relates to induction heating for cooking. Solid state reciprocal power switches are used to excite a resonant power output circuit including an induction coil to be inductively coupled to a cooking utensil. A first control signal which is a function of the Q of the coil, the direct current voltage applied to the power switches and the frequency of operation of the power switches is used to offset the power circuit from oscillating at resonance in order to control the power output. A solid state differential circuit is used responsive to a second control signal establishing the level of power desired and to the first control signal for regulation about the selected power level. The same differential circuit is responsive to a third control signal to insure low starting power or in case of a failure of the power line. Minimum power output is provided at the lower end of the ultrasonic frequency spectrum without entering the audible frequency range.