| 摘要 |
<p>PURPOSE:To reduce the packing space by securing the serial connection between a photocoupler having a photodetector which transmits a power supply cut-off command and a photodetector which a power supply cut-off signal to form a power supply cut-off circuit which is set in a power supply system for a logical device. CONSTITUTION:The power supply cut-off signal which is supplied to an input terminal D of a power supply cut-off circuit 1 to an output terminal C of a logical device 3 rises in a steady state where the AC voltage is continuously applied to a rectifying circuit REC from an input terminal AC. Thus a photodiode of a photocoupler PT is energized and emits the light, and a photothyristor is energized to supply a current. Then, the photodiode of the photocoupler is energized and emits the light, and a phototransistor which receives the light of the photodiode is energized. As a result, a low impedance state is secured between input terminals A and B of a DC stabilized power circuit 2. At the same time, the control voltage of a switching control part 2b is reduced to a low level and the supply of power is stopped to the device 3. A Zener diode ZD functions to promote the release of the cut-off state of the power supply which is caused by the cut of the AC voltage.</p> |
