| 摘要 |
PURPOSE:To prevent waste of power, by using a switch circuit controlling power supply to a zero voltage detection circuit. CONSTITUTION:The power supply to a zero voltage detection circuit 6 is controlled with a switch circuit 9. If no input signal is present, a light emitting diode 9a is not illuminated and a photothyristor 9c is nonconductive. In this case, no current flows to the circuit 6, then the waste of power can be prevented. If the input signal is present, the thyristor 9c is conductive and thyristors 5, 3 are conductive near the zero voltages of an AC power supply 1. |
