| 摘要 |
PURPOSE:To obtain the detection signal when the input AC supply voltage is OFF surely and with good isolation, by using a photo coupler. CONSTITUTION:When the switch 2 is closed and the power input is applied, since the photo coupler 33 is driven and the transistor 36 is conducted during a half cycle period, although the cpacitor 39 is discharged through the short circuit for the both ends, but in another half cycle, since the transistor 36 is not conductive, the capacitor 39 is charged up. The charging potential during this half cycle is set less than the potential conducting the transistor 44, then the transistor 44 is not conductive while the AC power input is applied. When the AC power input is disconnected, since the transistor 36 is OFF, the charging potential of the capacitor 39 is increased to make conductive the transistor 44 and to detect the interruption of the AC power input. |
