Capacitor charging circuit

Claim 1

A capacitor charging circuit comprising, a. a capacitor, b. a power transformer having a primary and a secondary winding, c. a rectifier bridge having input junctions connected across the said secondary winding and output junctions connected across the capacitor, d. a pair of silicon controlled rectifiers connected in parallel but opposite sense between one end of the power transformer primary winding and one side of an a.c. line, the other end of said primary winding being connected to the other side of the a.c. line, e. a pulse transformer having a primary winding and a pair of secondary windings, f. leads connecting each of the pulse transformer secondary windings across the gate and cathode electrodes of an associated one of said silicon controlled rectifiers, g. an oscillator circuit comprising a unijunction transistor having a second capacitor and the pulse transformer primary winding connected in series across its emitter and base-one electrodes, h. means normally energizing the oscillator circuit for oscillation at the frequency of the said a.c. line, i. a normally non-conducting clamping transistor having its output circuit connected to the emitter and base-two electrodes of the unijunction transistor, j. a potentiometer connected across the output junctions of said rectifier bridge, k. a Schmidt trigger actuated upon the application thereto of a d.c. voltage of predetermined magnitude, l. means applying the output voltage of said potentiometer to the Schmidt trigger, and m. means changing said clamping transistor to the conducting state when the Schmidt trigger is actuated.