| 摘要 |
PURPOSE:To obtain a power source synchronizing signal having time width with high accuracy, by constituting a device to be provided with a diode inserted between the comparison input terminal and the reference input terminal of a voltage comparison means or an operating power source. CONSTITUTION:The pulsating voltage A of a power source rectifying means 12 is impressed on the comparison input terminal 15a of the voltage comparison means 15, and on the reference input terminal 15b, a reference voltage C with high accuracy generated by a Zener diode 17 is impressed. When the voltage is less than the reference voltage C, a power source synchronizing signal voltage waveform D appears at the output terminal 15c of the comparison means 15. When the voltage A begins to rise over the voltage C, the diode 18 is energized, thereby, it follows only that a voltage B is set at a value higher than the voltage C by VF (the voltage drop of the diode in a forward direction), and the comparison means 15 can be prevented from being damaged, and also, the power source synchronizing signal disappears. Since the voltage B represents the pulsating voltage A itself and the voltage C is provided with high accuracy, the time width of an obtained synchronizing signal can be formed accurately.
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