Power controller

Abstract

A power controller for transmitting alternating current from a power input circuit to a load, the controller being a master silicon controlled rectifier, hereinafter the 'master rectifier,' and a slave silicon controlled rectifier, hereinafter the 'slave rectifier,' connectible in parallel with the load across the input circuit, a capacitor chargeable during positive half cycles for discharging at the zero voltage crossover between half cycles of positive and negative input voltage to render the master capacitor conductive and a second capacitor chargeable When the master controlled rectifier is conductive whose discharge renders the slave rectifier conductive at the instant of zero voltage crossover between half cycles of negative and positive input voltage. The controller may also include a light sensitive diode connected in series between the control gate of the master rectifier and the first capacitor which is conductive only as long as a light emissive diode is energized and an overload responsive circuit for deenergizing the light emissive diode upon the occurrence of an overload. The controller may also additionally include a shunting transistor for shunting the discharge from the first capacitor from the light sensitive diode during half cycles of negative input voltage to prevent initiation of conduction of the master rectifier at times other than at the instant of zero voltage crossover between half cycles of positive and negative input voltage. Another form of the power controller may include a DC to DC converter for supplying the power for turning on the master rectifier and for supplying substantially a large proportion of the current for turning on the slave rectifier. In this second form of controller a single capacitor is charged during the periods of conduction of the master rectifier and discharged through an amplifying transistor to the gate of the master rectifier.