| 摘要 |
PROBLEM TO BE SOLVED: To add control of preventing the overheat breakage of a semiconductor device for current limitation at the occurrence of an overcurrent, and prevent the voltage loss inside a circuit, in the stationary current range which is not more than the set current, in a protective circuit against overcurrent of a two-point connection type, such that it is merely inserted in series into the electrical path which protects from overcurrent. SOLUTION: An overcurrent state is detected with a current detection resistor, and the gate voltage of a power MOS FET 1 is lowered by the operation of a transistor 2. Using the voltage between a source and a drain which rose risen thereby as the voltage and detected voltage, causes a Schmitt trigger circuit 8 to be operated to instantaneously lower the gate voltage and a power MOS FET 1 to shift into 'OFF' condition. Next, a Schmitt trigger circuit 10 detects the 'OFF' condition and generates the reset signal of 'OFF' condition of the power MOS FET 1 after a preset time. In a stationary current region set with the current smaller than an overcurrent, the gate drive voltage of the power MOS FET generates the voltage under 1 V between A and B which become the voltage loss of this protective circuit against overvoltage, utilizing an astable multivibrator and a transformer. |
