| 摘要 |
PURPOSE:To permit instantaneous return to the initial potential at the noninputting by dropping the output of a time delay circuit to ground potential when the continuous AC leakage current exceeding a prescribed threshold value lowers below the threshold value before a prescribed time. CONSTITUTION:Input current (leakage current of a constant frequency) from an AC electric power source 1 is applied to a differential amplifier 2 having prescribed offset voltage. This output is supplied via a buffer circuit 3 to a time delay circuit 4. On the other hand, a control circuti 6 detects the output pulses of the amplifier 2, and controls a reset bias circuit 7. When the AC input lowers below the offset voltage before the prescribed time, a pulling down circuit 8 is operated by the output of the bias circuit 7, and the output of a time delay circuit 4 is dropped to ground potential. In this way, it is returned instantaneously to the initial potential at the noninputting. Hence, the inconvenience by the residual potential of the circuit 4 is prevented. |
