| 摘要 |
<p>The present invention is related to a high frequency heating apparatus for driving a magnetron such as a microwave oven, and has an object to provide a frequency modulating system capable of reducing power supply higher harmonic distortion of higher orders which are produced at phases in the vicinity of 0 degree and 180 degrees where an instantaneous voltage of a commercial power supply becomes the lowest voltage. In a high frequency heating apparatus of the present invention, when a signal for driving a first semiconductor switching element (3) and a second semiconductor switching element (4) is supplied, an occurrence of the power supply higher harmonic distortion of the higher orders is suppressed in such a manner that a switching frequency is smoothly changed which is located in the vicinity of a boundary between a time period during which a minimum switching frequency is limited to "f1" and a time period during which the limitation of the minimum switching frequency is released at the phases near 0 degree and 180 degrees where the instantaneous voltage of the commercial power supply becomes the lowest voltage, namely, a sudden change of a switching frequency is deleted.</p> |
