Switching circuit for controlling alternating circuit flow

Claim 1

In a circuit for controlling bi-directional current flow through a load, wherein the current is supplied by an AC source, the improvement comprising: automatically controlled switching means having a control electrode, and having a pair of principal conducting electrodes for connection in series with a load and an AC source; and trigger circuit means having an input coupled to one of said principal conducting electrodes, and having an output coupled to said control electrode of said switching means for triggering said switching means between conducting and nonconducting states at equal intervals during both positive and negative phases of voltage supplied by said source, said trigger circuit further including a resistor and a first capacitor coupled together to provide a timing circuit, first and second rectifying means coupled together in an opposedpolarity parallel relationship to control charging and discharging with said capacitor, biasing means including a second capacitor connected in series with one of said diodes and connected to one of said rectifying means to control its conduction point, current source means connected to said second capacitor for controlling the voltage thereacross to bias said one diode, and means connected to said trigger circuit means output for sensing the said charging and discharging of said first capacitor to produce trigger signals and to apply said trigger signals to said control electrode of said switching means.