The circuit shown in figure 1 is a "Crow Bar" type protection in which the ultra fast firing of an SCR when the reference voltage Vz is exceeded causes the fuse to open.
This fast circuit interruption action can be important in cases where we have a slow increase in current in case of problems, which can lead to the most fragile components being burned. Vz is a zener of 400 mW or more and the SCR TIC106 does not need a heat radiator since the driving time of this component is very small. Capacitor C1 prevents tripping of the transient circuit. The idea holds for currents above 1 A, in which case higher current SCRs are to be used.
In figure 2 we have the suggestion of printed circuit board in which this simple practical solution can be implemented.
Material list
SCR - TIC106 or equivalent - silicon controlled diode
Vz - Zener diode from 1.9 to 12 V x 400 mW
R1 - 220 ohm x 1/8 W - resistor
R2 - 47 ohm x 1/8 W - resistor
C1 - 220 nF - polyester or ceramic capacitor
F1 - 1 A fuse
Several:
Printed circuit board, fuse holder, wires, solder, etc.
