| 摘要 |
PURPOSE:To make it possible to suppress generation of surge current remarkably and restrict generation of noise to the utmost by detecting zero crossing time of pulsating current and starting a power amplifier from this point of time. CONSTITUTION:On receiving AC, a constant voltage circuit 20 functions to operate a monostable multivibrator 40 of variable duty ratio. On the other hand, a zero-crossing detecting means 30 detects zero-crossing time of pulsating current from a rectifier circuit 10, and trigger pulse is impressed to the monostable multivibrator 40. Accordingly, the monostable multivibrator 40 supplies square pulse of set duty ratio to a power amplifier 50, and the power amplifier 50 amplifies and supplies AC or pulsating current to a load only for a phase period determined by the duty ratio from zero-crossing time of AC or pulsating current acting only in one level period basing on the square pulse.
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