Phase controlled power supply

Claim 1

A phase controlled power supply circuit comprising a source for supplying an alternating current signal having a desired magnitude to a pair of input terminals, a load device and a silicon controlled rectifier connected in series with said pair of terminals, a gate-signal generating circuit for said silicon controlled rectifier coupled to said terminals and to the gate electrode of said silicon controlled rectifier, said gate-signal generating circuit comprising a unijunction transistor, a resistor, a zener diode coupled across the base electrodes of said unijunction transistor and a firing circuit for said unijunction transistor coupled to the emitter electrode of said unijunction transistor; the base-one electrode of said unijunction transistor is connected directly to said gate electrode of said silicon controlled rectifier and is connected through said resistor to a terminal of said silicon controlled rectifier, a capacitor having a value between 0.1 and 0.5 microfarads connected directly between the base-two electrode of said unijunction transistor and said terminal of said silicon controlled rectifier for varying the firing angle of said silicon controlled rectifier when the magnitude of said alternating current signal varies from said desired magnitude such that substantially the same power is dissipated by said load device even though there are variations in the magnitude of said alternating current signal.