This is a circuit that I built in 1994, I think it’s very simple, but very effective. See the schematic on next figure.

This power supply can control up to 22VDC, depending on the transformer’s secondary voltage. This voltage can be adjusted by the 500 Ohms potentiometer.

WARNING: The relay coil’s voltage must be around the rectified voltage which will energize it, not above or below.

When the protective circuit notices a rise of current, the SCR will operate, energizing the relay coil leaving the circuit in standby mode. When the current is set back to normal, S1 must be pressed in order to disarm the SCR. The sensitivity of this protective circuit is adjusted by the 1Megohm variable resistor, you can experiment with other values for this device.

The 2SC111 transistor is the voltage regulator, however you may use an IC voltage regulator instead (Like the LM317).