Patent ID: 7542313
Filing Date: 2009-06-02
Classification: H05B

Abstract:
1. An induction heating apparatus comprising a power source; an inverter circuit having at least one switching element for converting power from said power source into a high frequency AC power; a heating coil connected to output terminals of said inverter circuit; and a control circuit having a drive circuit for producing a drive signal to turn said switching element on and off and thereby supplying the high frequency AC power to said heating coil; wherein said control circuit comprises a resonance waveform detector for detecting a high frequency AC waveform supplied from said inverter to said heating coil to produce a detection signal corresponding to said high frequency AC power waveform; a phase comparator for producing an adjusting signal corresponding to a phase difference between said detection signal from said resonance waveform detector and drive signal from said drive circuit; and an addition circuit for superimposing the drive signal from said drive circuit on the detection signal from said resonance waveform detector to supply the superimposed signal to said phase comparator; said detection signal from said resonance waveform detector is varied with generally the same frequency relative to the drive signal; and said drive circuit determines the oscillation frequency of drive signal to said switching element in response to said adjusting signal from said phase comparator.