| 摘要 |
The invention relates to a high frequency heating apparatus and provides a tracking method of a frequency modulation in order to prevent an extension of the harmonic current component of an oscillation threshold ebm which varies from moment to moment in accordance with a change in the temperature of a magnetron. A driving signal for driving a first semiconductor switching element ( 3 ) and a second semiconductor switching element ( 4 ) is transmitted to a driving control IC unit ( 14 ), and an input reference signal Ref is used to perform an input current fixed control. In this case, a variation amount of the input current of the input reference signal Ref is understood as an accumulation information POW and a constant is optimally configured in a resistor network in an ebm-tracking bias circuit ( 20 ). Sequentially, a portion in which an operating frequency ascends is provided by giving a bias to a frequency modulation waveform, and then a frequency modulation tracking is performed. In this manner, by easily dealing with the change in an oscillation threshold ebm resulting from the change in a temperature, the extension of the harmonic current component has been prevented.
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