| 摘要 |
PURPOSE:To limit the overcurrent to a proper current corresponding to the temperature of a MOS FET by always supervising a voltage between a drain and a source of the MOS FET and operating an overcurrent protection device when the voltage drop exceeds a predetermined value at current conduction. CONSTITUTION:When an on-signal is outputted from a gate control circuit 11 to a gate G of the MOS FET 12 and a current flows from a drain D to a source S, the voltage drop by the passing current is detected by a voltage detector 21. The on-signal is given also to an on-signal detector 22 to close a switch 23, then the detection voltage from a voltage detector 21 is given to a comparator 24 via the switch 23 and when it is larger than the set value decided by a setting resistor 25, a signal is fed to the gate control circuit 11 and an off-signal is given to the gate G. The overload protection device is operated even with a small current at a high temperature of the MOS FET having a positive resistance temperature coefficient, a large current is allowed at a low temperature so as to contribute to the improvement of the efficiency of the device. |
