Overvoltage Crowbar Circuit

A simple circuit but very effective to protect a main circuit which is sensitive to overvoltages. The circuit uses a zener diode in parallel to the power line of the protected circuit or device. Once the output of the power supply increases due to a malfunction, the excess voltage will be routed to ground by the zener diode. If the voltage will increase further, the total current consumption will exceed the capacity of the fuse. The fuse will blow at this moment and the current supply is broken.

The schematic diagram can be download here!