Zero swithching network for a triac swithcing circuit

Claim 2

A switching circuit for switching an alternating voltage source across a load comprising: switch means having a first, second, and control electrode, said switch means exhibiting the characteristic of presenting a low impedance to current flow from said voltage source to said load when a forward biasing signal is applied to said control electrode; circuit means for applying a forward biasing signal to said control electrode including: a transformer having a primary and a secondary winding, said secondary winding connected between said first and said control electrodes; first and second actuatable switching means for, when both are actuated, completing a circuit between said primary winding and a power supply source for energizing said primary winding; means for periodically and at a given frequency, actuating said first actuatable switching means; and means for monitoring the voltage developed by said alternating voltage source and actuating said second switching means when said alternating voltage attains a predetermined voltage level.

Claim 3

A switching circuit as defined in claim 1 wherein said monitoring means includes a second switch means; and a bistable circuit means having a first and a second condition, an input circuit means, and an output circuit connected to said second actuatable switching means, said input circuit means of said bistable circuit being coupled to said second switch means and said alternating source so that upon closure of said second switch means said bistable circuit will change from said first condition to said second condition when said alternating voltage passes through said predetermined voltage level.

Claim 4

A switching circuit as defined in claim 2 wherein said bistable circuit means includes a first and a second electronic control means eacH having an input circuit means and an output circuit, said output circuit of each control means being coupled to the input circuit means of the other control means so that upon actuation of either of said control means the other of said control means is thereby actuated; said input circuit means of said first and said second control means being coupled in common to said alternating voltage source, and said input circuit means of said first and second control means being coupled to said second switch means.

Claim 5

A switching circuit as defined in claim 3 including a variable circuit means coupled between said first and said second control means, and said alternating voltage source for altering said predetermined voltage level at which said bistable circuit means is actuated from said first to said second condition.

Claim 6

In a load switching circuit having a triac for switching an alternating voltage source across a load, a voltage synchronizing network for providing an output signal for gating a said triac into conduction when the voltage developed by said alternating voltage source is at a predetermined voltage level comprising: switch means for actuating said synchronizing network; a first electronic control means having an input circuit adapted to be coupled to said alternating voltage source, and an output circuit; a second electronic control means having an input circuit coupled to said switch means, and an output circuit; a bistable circuit means having a first and a second condition, and a first and a second actuatable switching means; and said output circuit of said first control means being coupled to said first and said second actuatable switching means, said output circuit of said second control means being coupled to said first actuatable switching means, and said switch means being coupled to said second actuatable switching means so that upon closure of said switch means said bistable circuit will change from said first condition to said second condition when the voltage developed by said alternating voltage source passes through a predetermined voltage level.

Claim 7

In a load switching circuit having a triac for switching an alternating voltage source across a load, a voltage synchronizing network for providing an output signal for gating a said triac into conduction when the voltage developed by said alternating voltage source is at a predetermined voltage level comprising: switch means for actuating said synchronizing network; a first electronic control means having an input circuit adapted to be coupled to said alternating voltage source, and an output circuit; a second electronic control means having an input circuit coupled to said switch means, and an output circuit; a bistable circuit means having a first and a second condition, and a first and a second actuatable switching means; and said output circuit of said first control means being coupled to said first and said second actuatable switching means, said output circuit of said second control means being coupled to said first actuatable switching means, and said switch means being coupled to said second actuatable switching means so that upon closure of said switch means said bistable circuit will change from said first condition to said second condition when the voltage developed by said alternating voltage source passes through a predetermined voltage level.

Claim 8

In a triac switching circuit for switching an alternating voltage source across a load, a voltage synchronizing network for providing an output signal when the voltage developed by said alternating voltage source is at a predetermined voltage level comprising: switch means for actuating said synchronizing network; a bistable multivibrator having a first and a second input circuit and an output circuit, a said multivibrator having a first and a second condition; a first electronic control means having an input circuit adapted to be coupled to said alternating voltage source, an output circuit; a second electronic control means having an input circuit coupled to said switch means, and an output circuit; and said output circuit of said first control means being connected to said first and second input circuits of said bistable multivibrator, said output circuit of said second control means being connected to said second input circuit of said bistable multivibrator, and said switch means connected to said first input circuit of said bistable multivibrator so that upon closure of said switch means said bistable circuit will change from said first condition to said second condition when the voltage developed by said alternating voltage source passes through a predetermined voltage level.

Claim 9

In a triac switching circuit for switching an alternating voltage source across a load, a voltage synchronizing network for providing an output signal when the voltage developed by said alternating voltage source is at a predetermined voltage level comprising: switch means for actuating said synchronizing network; a bistable multivibrator having a first and a second input circuit and an output circuit, a said multivibrator having a first and a second condition; a first electronic control means having an input circuit adapted to be coupled to said alternating voltage source, an output circuit; a second electronic control means having an input circuit coupled to said switch means, and an output circuit; and said output circuit of said first control means being connected to said first and second input circuits of said bistable multivibrator, said output circuit of said second control means being connected to said second input circuit of said bistable multivibrator, and said switch means connected to said first input circuit of said bistable multivibrator so that upon closure of said switch means said bistable circuit will change from said first condition to said second condition when the voltage developed by said alternating voltage source passes through a predetermined voltage level.

Claim 10

A network as defined in claim 6 wherein said first electronic control means is coupled to a variable circuit means for altering said predetermined voltage at which said bistable multivibrator is actuated from said first to said second condition.