This Fast response power supply protection circuit is used to protect regulated power supply from the risks of undervoltage and overvoltage condition.
When working with a regulated power supply to reduce a supply voltage, there’s always the risk that component failure in the power supply may cause a severe overvoltage condition through the load. To deal with overvoltage conditions, the Fast response power supply protection circuit is designed to protect the load underovervoltage conditions. Component values given are for a 20 V supply with regulated output at 12V. The zener diode can be changed-according to any voltage is to be the maximum. When the voltage at the regulator output goes up to 13 V or higher, the zener diode breaks down-and triggers-the thyristor which will shorts out the supply line and blows the main fuse.