| 摘要 |
PURPOSE:To reduce a rush current at application of power to a device without consuming useless power with a resistor by detecting a pulsating current of a load current supplied from a power transformer so as to restrict the time when the power is applied. CONSTITUTION:A negative pulsating voltage is generated across a resistor R4 with a current resulting from rectifying a voltage between windings 3-4 of a power transformer T1 and fed to a base of a transistor(TR) Q2. When a base voltage of the TR Q2 is higher than the negative voltage of the emitter by a prescribed voltage or over, a collector current IC1 flows. A collector of the TR Q2 is connected to a voltage detection terminal 4 of a microcomputer IC 2 to detect the presence of the voltage. The microcomputer IC2 detects the voltage application period and outputs a drive voltage from a relay drive output terminal 3 so as to close a relay 1 for a period when a voltage is applied to the terminal 4 after a power switch SW1 is closed. That is, the relay 1 is closed for a period when the input AC voltage is low with the voltage detected synchronously with the input voltage. |
