D.c.-fed two stage regulated direct-current supply system

Claim 1

A regulated DC supply system wherein a switching type regulator is controllable both in response to a constant frequency variable pulse width first stage and to a variable frequency minimum pulse width second stage for very light loads comprising, a semiconductor controlled rectifier switch and a control circuit therefore, two stage regulator means for intermittently activating said switch by way of said control circuit to effect conducting and nonconducting thereof, said control circuit comprising a monostable multivibrator, said regulator means comprising a constant frequency pulse generator first stage for controlling said multivibrator and making said switch conductive at the beginning of periods and for stopping the conducting of said switch at varying points in said periods to provide conducting intervals of varying lengths between a maximum length and a minimum length, said regulator means further comprising frequency modifying control means connected to said constant frequency pulse generator to form a variable frequency pulse generator second stage for making said switch conductive for intervals of constant lengths substantially equal to said minimum length, and regulating switching means for activating said second generator when said conducting intervals of said first stage reduce to the length of said minimum length, said regulator means being operable to maintain a predetermined voltage subject to the prevention of the exceeding of a predetermined maximum current, and filter means at the outlet side of said switch.