Patent ID: 7230219

Claim:
An inverter power source control circuit for a high frequency heating apparatus, which is provided in an inverter power source circuit for supplying an electric power to a magnetron of the high frequency heating apparatus and operable to generate an oscillation control signal by full wave rectifying and converting an alternating current output from an alternating current power source to a direct current output and applying the oscillation control signal, based on a PWM control signal through an inverter to a switching element to thereby convert the direct current output to a desired alternating current output, which circuit comprises; a control reference voltage setting circuit for outputting a reference voltage setting signal useable as a benchmark for generation of the oscillation control signal of a voltage set in correspondence with fluctuation of the PWM control signal, wherein by means of the oscillation control signal having the voltage so set, a current waveform of the alternating current output can be approximated to a sinusoidal wave by generating an electric current at both sides of the current waveform of the alternating current output; an input waveform adjusting circuit for adjusting a peak portion of an input waveform, applied to the inverter to generate a peak adjustment signal required to generate the oscillation control signal, to a sinusoidal wave, wherein by means of the oscillation control signal having this peak adjustment signal, the current waveform of the alternating current output can be approximated to the sinusoidal wave through subtraction of the peak portion of the waveform using the peak adjustment signal of the sinusoidal wave; and an oscillation control signal generating circuit for generating the oscillation control signal based on a waveform shaping signal, comprised of the reference voltage setting signal and the peak adjustment signal, and a triangular wave signal from an oscillator, wherein by means of the oscillation control signal containing the reference voltage setting signal and the peak adjustment signal, even though the PWM control signal fluctuates, the current waveform of the alternating current output from the alternating current power source can be approximated to a sinusoidal wave to thereby improve a power factor of an electric power source circuit.