Momentary power supply shutdown system

Claim 1

A momentary shutdown circuit for a regulated power supply, said power supply including at least one SCR connected as a rectifier between an a-c input source and a smoothing filter, a pulse generator synchronized by said a-c input source and connected to fire said SCR, a reference supply source connected for comparison with said power supply output, a variable pulse delay circuit connected into said pulse generator so as to vary the timing of firing said SCR, said pulse delay connected to sense the difference between the potentials of said power supply and said reference supply and to reduce said delay as said difference decreases, said shutdown circuit comprising: a storage capacitor having two terminals, one terminal of said capacitor being connected to the output of said power supply and the second terminal being connected through a series resistor to a shutdown source of potential independent from said power supply and having a potential value substantially lower than the nominal potential of said power supply, and a unidirectional switch connected between said second terminal of said capacitor and a control element of said pulse generator, said switch being connected in a polarity such that said shutdown source biases sAid switch to be normally nonconductive but conductive when a sudden drop in power supply voltage is coupled by way of said capacitor to said switch, said switch when conductive acting upon said control element to render said pulse generator inactive thereby shutting down the operation of said power supply for a period of time determined by the time constant of said resistor-capacitor conbination.