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 unitaccording to the present invention is provided with control units(to) respectively corresponding to a plurality of heating units(to). A phase detectorof the control unitobtains a phase difference between an output current (heating coil current IL4) of an inverterdetected by a current transformerand a reference signal outputted by a reference signal generating sectionand inputs it to a drive control sectionThe drive control sectionadjusts an output timing (phase) of a gate pulse to be given to the inverterso as to make a phase of the heating coil current IL4 of the invertercoincide with a phase of the reference signal outputted by the reference signal generating sectionA phase control sectioncontrols a variable reactorso as to make the phases of an output voltage and the output current (heating coil current IL4) of the invertercoincide with each other, and improves a power factor of the inverter. Each of the other control unitstoalso performs the same control operation.