| 摘要 |
PURPOSE:To perform the protection assuredly against overcurrent or malfunction by checking the current flowing to a load and by interrupting the current supply to the load when the conduction is kept for not less than a predetermined time where the voltage corresponding to this current exceeds the specified reference voltage. CONSTITUTION:In a comparator 12 specified reference voltage Vr is given to an input (-) and this reference voltage Vr is compared with the detected voltage given to a (t) input. As a result, if the detected voltage Vd exceeds the reference voltage Vr, an output signal SG will be '1'. This output signal SG is given to a timer circuit 13. The timer circuit 13 measures the time when the output signal SG of the comparator 12 keeps '1' to the timer circuit 13. When this measured time gets to the predetermined timer operating time preset to the timer circuit 13, an output signal '1' is outputted. A power relay 14 is thereby energized to open a contact RB and the current supplied to the collector of a transistor Tr2 is interrupted. |
