| 摘要 |
PURPOSE:To form a power source for pulse width control of a simple circuit by connecting a series circuit of a diode and a photocoupler which varies in resistance with the intensity of photodetected light in parallel to the resistance of a CR oscillator. CONSTITUTION:When the DC output voltage between terminals 13 and 14 rises above a specific value, the photodiode 10 illuminates more brightly by the voltage rise. Its light is photodetected by a photocoupler transistor TR11 and a photodetection current (i) flows as shown by an arrow, so that the resistance Rx of the TR11 decreases. The resistance Rx is connected in parallel to the resistance 25 of the CR oscillator, whose oscillation frequency is therefore increased. Consequently, a pulse with narrowed-down width from the CR oscillator is applied to an FET29 through an inverter 28, so a specific output voltage is developed between the terminals 13 and 14. Thus, the power source for pulse width control is formed of the simple circuit.
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