| 摘要 |
PROBLEM TO BE SOLVED: To improve the degrees of freedom in the design of the fusing current of a fuse, by using such a fuse which fuses and turns off a switch circuit, when a fuse fusing circuit which is started by means of an overvoltage signal is started. SOLUTION: An overvoltage protective circuit 5 is provided with a fusing circuit 4 which supplies a fusing current 4a to a fuse 3, in response to the detecting output of the circuit 5, and when an overcurrent occurs in a power line 7, the circuit 5 outputs an overcurrent signal. Since the circuit 4 makes the current 4a to flow, upon receiving an overvoltage signal, the fuse 3 is fused, and a switch signal 6a is interrupted. consequently, a MOSFET Q1 is turned off, and the power line is disconnected, resulting in the prevention of an overvoltage from being applied across a load circuit 2. Therefore, no power supply current flows to the circuit 2, and the current which normally flows to the fuse 3 becomes the gate current of the MOSFET Q1 only. Since it becomes unnecessary to take into account the rush current which occurs when power supply is made to the load circuit, the fusing current of the fuse 3 can be made to flow readily. |
