OFF DELAY TIMER AND INTERNALLY GENERATED AUXILIARY DIRECT CURRENT VOLTAGE SOURCE FOR A CONTROLLED RECTIFIER ALTERNATING CURRENT SWITCH FOR USE THEREIN

• US 3,711,761 A
• Filed: 08/13/1970
• Issued: 01/16/1973
• Est. Priority Date: 08/13/1970
• Status: Expired due to Term

• Current Assignee: Guido Watson
• Original Assignee: Guido Watson
• Inventors: Watson, Guido
• Primary Examiner(s): Goldberg, Gerald
• Application Number:
  US05/063,655
• Time in Patent Office: 887 Days
• Field of Search: 321/18 323/22SC,22Z,DIG.1,38,39 307/252J,252W,252N,318,24 317/36TD
• US Class Current: 327/463
• CPC Class Codes: H03K 17/292 in thyristor, unijunction transistor or programmable unijunction transistor switches

Abstract

An alternating current switch includes a full-wave rectifier with one input terminal thereof connected to an alternating current line, and the other input terminal connected by way of a load impedance to the alternating current line, with a controlled rectifier connected across the output of the full wave rectifier and while conducting providing for the flow of current through the load impedance and while nonconducting preventing the flow of current through the load impedance, with a Zener diode connecting the control element of the controlled rectifier to the anode thereof whereby a gate drive for gating the controlled rectifier on is obtained only when the voltage across the Zener diode is sufficient to cause the Zener diode to become conductive.

Claims

1. In a circuit of the type in which a full-wave rectifier is connected to an alternating current source and a controlled rectifier having a control element, an anode and a cathode is connected across the output terminals of the full-wave rectifier to provide an alternating current switch, said circuit including a load means, a direct current supply voltage, the improvement which comprises means for providing a substantially continuous direct current supply voltage notwithstanding a gated-on condition of the controlled rectifier, said means including delay means for causing said controlled rectifier to be non-conductive for a portion of each half-cycle, including a storage capacitor, a diode having an anode and cathode and a resistor the combination of all three being connected in series circuit relationship across the output terminals of the full-wave rectifier with the load means connected in parallel with the storage capacitor, a resistor connected from the control element of the controlled rectifier to the cathode thereof, and a Zener diode connected from said control element to the junction between said first-named resistor and said first-named diode, said controlled rectifier switching off each half-cycle when the anode current falls to zero, current for a time thereafter flowing through said first-named resistor and said first-named diode to charge said storage capacitor, said storage capacitor maintaining the voltage drop across the Zener diode at a value at which the Zener diode is non-conductive until the storage capacitor has been charged to at least a predetermined voltage value whereupon said Zener diode becomes conductive and supplies gate current to the control element of said controlled rectifier whereafter anode current again flows in said controlled rectifier, said firstnamed diode being reverse biased when the controlled rectifier fires thereby isolating the storage capacitor from the controlled rectifier, and a transistor having the collector-emitter path thereof connected between the control element of the controlled rectifier and the cathode thereof, said transistor while saturated rendering said controlled rectifier non-conductive, said transistor while unsaturated allowing said controlled rectifier to become conductive.

2. In a circuit of the type in which a full-wave rectifier is connected to an alternating current source and a controlled rectifier having a control element, an anode and a cathode is connected across the output terminals of the full-wave rectifier to provide an alternating current switch, said circuit including a load means, a direct current supply voltage, the improvement which comprises means for providing a substantially continuous direct current supply voltage notwithstanding a gated-on condition of the controlled rectifier, said means including delay means for causing said controlled rectifier to be non-conductive for a portion of each half-cycle, including a storage capacitor, and a resistor connected in series across the output terminals of the full-wave rectifier with the load means connected in parallel with the storage capacitor, a resistor connected from the control element of the controlled rectifier to the cathode thereof, a Zener diode connected from said control element to the junction between said first-named resistor and said storage capacitor, said controlled rectifier switching off each half-cycle when the anode current falls to zero, current for a time thereafter flowing through said first-named resistor to charge said storage capacitor, said storage capacitor maintaining the voltage drop across the Zener diode at a value at which the Zener diode is non-conductive until the storage capacitor has been charged to at least a predetermined voltage whereupon said Zener diode becomes conductive and supplies gate current to the control element of said controlled rectifier whereafter anode current again flows in said controlled rectifier, a transistor having a base, a collector and an emitter with the collector-emitter path thereof connected between the control element of the controlled rectifier and the cathode thereof, said transistor while saturated rendering said controlled rectifier non-conductive, said transistor while unsaturated allowing said controlled rectifier to become conductive.

3. A circuit according to claim 2 including in addition means including timing circuit means under the control of contacts adapted to be opened and closed connecting the timing circuit means to the alternating current line for controlling the conductivity of said transistor and thereby controlling the operation of the controlled rectifier.

4. A circuit according to claim 3 in which the timing circuit means includes a timing capacitor and the circuit means includes diode means connecting said timing capacitor across the alternating current line while the contacts are closed whereby the timing capacitor is charged by half-wave direct current obtained from the alternating current line.

5. Apparatus according to claim 4 including in addition a Zener diode operatively connected across the timing capacitor for maintaining the voltage across the timing capacitor after charging at substantially a predetermined value.

6. Apparatus according to claim 5 including an additional transistor interposed between the timing capacitor and the first-named transistor which controls the controlled rectifier, said additional transistor while conductive causing the first-named transistor to conduct, said additional transistor being rendered non-conductive when the timing capacitor is charged to said predetermined voltage value thereby rendering the first-named transistor non-conductive and permitting the controlled rectifier to be fired.

7. An alTernating current switch comprising, in combination, a full-wave rectifier, one input terminal of the full-wave rectifier being adapted to be connected to one side of an alternating current line, the other input terminal of the full-wave rectifier being adapted to be connected by way of a load impedance to the other side of the alternating current line, a controlled rectifier connected across the output of the full-wave rectifier and while conducting providing for the flow of current through the load impedance and while non-conducting preventing the flow of current through the load impedance, and a Zener diode connecting the control element of the controlled rectifier to the anode thereof, gate drive for gating the controlled rectifier on being obtained only when the voltage across the Zener diode is sufficient to cause the Zener diode to become conductive, and a transistor having the collector-emitter path thereof operatively connected between the control element of the controlled rectifier and the cathode thereof, the transistor while conductive preventing the controlled rectifier from conducting, the transistor while non-conductive permitting the controlled rectifier to be gated on.