Controlling apparatus for high frequency high voltage power source for corona discharge processing

摘要

A controlling apparatus for a high frequency high voltage power source is disclosed which eliminates a switching loss of a high frequency invertor and allows adjustment of the output power to be performed continuously and accurately over a wide range. A resonance current of a resonance circuit of the high frequency high voltage power source is detected by current detection means, and a phase locked loop circuit locks itself with a frequency with which it coincides in phase with the resonance current to produce a synchronized pulse signal. From the pulse signal, a signal having a zero voltage outputting period of a preset duration is formed by a pulse density modulation circuit to change the pattern of a gate signal for switching semiconductor elements of a high frequency invertor to adjust the output power. An input voltage before a zero voltage outputting period is entered is stored into voltage storage means such as a sample and hold circuit so that the phase locked loop circuit may continue to lock with the same frequency also during the zero voltage outputting period.