Zero crossing point switching circuit

Claim 2

A switching network comprising: load means, source means supplying an alternating voltage; switch means for selectively connecting said source means to said load means, said switch means becoming an open circuit when the current flowing therethrough decreases to zero amplitude; zero-cross detector means coupled across said switch means for initially detecting the zero-crossover points of the alternating voltage supplied by said source means when the switch means is opened, and thereafter detecting a voltage transition occuring when said switch means opens as the result of the zero-crossover of the alternating current flowing through said switch means; and signal generating means connected to supply signals to initially close said switch means in response to the detection of zerocrossover points of the alternating voltage by said zero-cross detector means and thereafter to supply signals to close said switch in response to the detection of the voltage transition occuring as a result of the zero-crossover of the alternating current flowing through said switch means.

Claim 3

The switching network recited in claim 1 including control means for selectively disabling said signal generating means.

Claim 4

The switching network recited in claim 1 wherein said zero-cross detector means includes rectifier means for initially producing a full-wave rectified signal from the alternating voltage established across said switch means by said source means when said switch means is open, and thereafter receiving the voltage transition occuring when said switch means opens as a result of the zero-crossover of the alternating current flowing through said switch means, pulse generating means, an current steering means for selectively supplying current to said pulse generating means as a function of the amplitude of the rectified signal produced by said rectifier means such that said pulse generating means selectively generates a pulse.

Claim 5

The switching network recited in claim 1 wherein said switch means includes a thyristor.

Claim 6

The switching network recited in claim 4 wherein said thyristor is a trigger operated device capable of bidirectional current conduction when triggered by a suitable signal.

Claim 7

The switching network recited in claim 3 including means for clamping the pulses supplied by said pulse generating means.

Claim 8

The switching network recited in claim 4 wherein said thyristor is connected to receive a trigger signal from said signal generating means, said signal generating means comprises one-shot multivibrator circuit means, said one-shot multivibrator circuit means supplies a signal of sufficient time duration to assure that said thyristor achieves a self-sustaining latching current therethrough.

Claim 9

A switching network comprising triggerable switch means for conducting bidirectional current in the presence of a triggering signal, said switch means becoming an open circuit when the current flowing therethrough decreases to zero amplitude, a.c. voltage source means, load means connected to said source means and to said switch means in order to receive said a.c. voltage from said source means when said switch means is triggered, rectifier means coupled across said switch means in order initially to receive the a.c. voltage established across said switch means by said source means when said switch means is opened and to produce a full-wave rectified signal from the a.c. voltage received by said rectifier means, and thereafter to receive a voltage transition occuring when said switch means opens as a result of the zero-crossover of the alternating current flowing throUgh said switch means, pulse producing means connected to said rectifier means in order to initially produce pulses in substantial synchronism with the zero amplitude points of said full-wave rectified signal from said rectifier means when said switch means is open, and thereafter to produce pulses in substantial synchronism with the voltage transition occuring when said switch means opens as a result of the zero-crossover of the alternating current flowing through said switch means, one-shot multivibrator means connected to receive said pulses from said pulse producing means and to produce the trigger signal in substantial synchronism with said pulses, and circuit means for supplying said trigger signal from said one-shot multivibrator means to said triggerable switch means.

Claim 10

A switching network comprising triggerable switch means for conducting bidirectional current in the presence of a triggering signal, said switch means becoming an open circuit when the current flowing therethrough decreases to zero amplitude, a.c. voltage source means, load means connected to said source means and to said switch means in order to receive said a.c. voltage from said source means when said switch means is triggered, rectifier means coupled across said switch means in order initially to receive the a.c. voltage established across said switch means by said source means when said switch means is opened and to produce a full-wave rectified signal from the a.c. voltage received by said rectifier means, and thereafter to receive a voltage transition occuring when said switch means opens as a result of the zero-crossover of the alternating current flowing throUgh said switch means, pulse producing means connected to said rectifier means in order to initially produce pulses in substantial synchronism with the zero amplitude points of said full-wave rectified signal from said rectifier means when said switch means is open, and thereafter to produce pulses in substantial synchronism with the voltage transition occuring when said switch means opens as a result of the zero-crossover of the alternating current flowing through said switch means, one-shot multivibrator means connected to receive said pulses from said pulse producing means and to produce the trigger signal in substantial synchronism with said pulses, and circuit means for supplying said trigger signal from said one-shot multivibrator means to said triggerable switch means.

Claim 11

The switching network recited in claim 8 including first transformer means connected across said switch means to receive the a.c. voltage established across said switch means, said first transformer means further connected to said rectifier means to couple the a.c. voltage thereto, and said circuit means includes second transformer means for coupling said trigger signal from said one-shot multivibrator means to said triggerable switch means said first and second transformer means providing isolation between said a.c. voltage source means and said switching network.

Claim 12

The switching network recited in claim 8 wherein said pulse producing means includes differentiating means such that the pulses are connected to spike-like signals of opposite polarity, and clamping means for clamping spike-like signals of one polarity.