| 摘要 |
<p>PURPOSE:To detect a fault of line where a transistor (TR) circuit is shut off by providing a current detection means so as to detect a current flowing through a constant voltage diode. CONSTITUTION:When a ground fault takes place to a line and a potential difference between a TR circuit 131 connected in series with the line and a resistor 133 excees a breakdown voltage of the constant voltage diode 137 connected in parallel, the feeding system by the operation of the constant voltage diode 137 is switched from the TR circuit 131 to a photocoupler 139 and the TR circuit 131 is protected from overcurrent. Thus, when the feeder system is switched from the TR circuit 131 to the photocoupler 139, a current detection means 140 connected in series with the constant voltage diode 137 detects the state. Thus, the operation of the current limit circuit is detected to inform it to a control circuit or the like.</p> |
