Induction heating apparatus with protection against power interruption

Claim 1

An induction heating apparatus, which operates using power from an AC power source comprising: an AC power supply line having one end connected to the AC power source; rectifying means, connected to the other end of said AC power supply line, for rectifying a supplied AC voltage applied from the AC power source to a DC voltage output; inverter means for converting the DC voltage output from said rectifying means into a high-frequency output; heating coil means coupled to said inverter means for receiving said high-frequency output and for generating a high-frequency alternating magnetic field therefrom, induction heating of a load being performed by said alternating magnetic field; voltage converting means coupled to said other end of said AC power supply line for converting the AC voltage supplied from the AC power source to a converted AC voltage; voltage fluctuation detecting means, coupled to said voltage converting means, for receiving the converted AC voltage and for detecting variations in the level of the supplied AC voltage in accordance with the converted AC voltage, and providing a detection signal based on the converted AC voltage which assumes one state when the supplied AC voltage falls below a first predetermined threshold and assumes a second state upon lapse of a predetermined period after the supplied AC voltage rises above a second predetermined threshold; and control means, coupled to said voltage fluctuation detecting means, for receiving the detection signal and providing a control signal which stops said inverter means for a period equal to the duration of said detection signal in said one state thereby protecting the induction heating apparatus against power interruption.