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Electronic fuse with transistors

Using electronic diagram below, can be made very simple electronic circuit that acts as an electronic fuse.
This electronic fuse is connected between output power supply and load. After „burn" current fuse and return to its nominal value, fuse can be rebooted with the switch S1.

Transistor Q1 and resistor R1 form a 6 mA current source which, together with zener diode D1, produces a voltage of 5.6 V relative to positive supply line. This provides a negative gate voltage of T3 sufficient to maintain the p-channel MOSFET in conduction.
When the load current increases to about 1A, voltage drop in Q3, D2 and part of P1, reach a level when T2 enter in conduction, so that the gate-source junction of T3 will be short circuited. Diode D3 will light, indicating burn fuse
The values given in the scheme, the maximum load current is about 300 mA. T3 voltage drop is only 100mV. You can get high current load using a p-channel MOSFETs with superior parameters of T3 position, or by connecting two or more type IRF9530 FET's in parallel.

Circuit Diagram: 
Electronic fuse with transistors circuit diagram

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