Apparatus for heating an electrically conductive cooking utensil by magnetic induction

摘要

An induction heating apparatus having a heating unit with a plurality of parallel heater coils. A low-frequency a.c. power source provides the power which is converted by a static power converter into a high-frequency power applied to the heater coils to produce time-varying magnetic fields. The converter has a switching circuit connected in parallel with the heating unit and said power source for developing the high-frequency power with a frequency substantially equal to a frequency with which the switching circuit is triggered. Control circuitry provides a reference voltage generator and current detector for developing a voltage representative of the current flowing through the heater coils. A single comparator is connected to the reference voltage regulator and the current detector for producing an ON signal when the voltage from the current detector is lower than the reference voltage of the reference voltage generator and for producing an OFF signal when the voltage from the current detector exceeds the reference voltage. A pulse generator is connected to the comparator for producing pulses when receiving the ON signal and ceases to produce pulses when receiving the OFF signal. A pulse supply circuit applies the pulses from the pulse generator to the switching circuit to trigger it in response to the pulses.