Induction heating method and unit

Abstract

It is an object of the present invention to prevent temperature decrease in a border portion of each of heating coils and to enable to eliminate an influence given by the change in a load state. In order to attain this object, an induction heating unit according to the present invention is provided with control units respectively corresponding to a plurality of heating units. A phase detector of the control unit obtains a phase difference between an output current (heating coil current) of an inverter detected by a current transformer reference signal outputted by a reference signal generating section, and inputs it to a drive control section. The drive control section adjusts an output timing (phase) of a gate pulse to be given to the inverter so as to make a phase of the heating coil current of the inverter coincide with a phase of the reference signal outputted by the reference signal generating section. A phase control section controls a variable reactor so as to make the phases of an output voltage and the output current (heating coil current) of the inverter coincide with each other, and improves a power factor of the inverter. Each of the other control units also performs the same control operation.