Two-wire dimmer switch for low-power loads
First Claim
1. A load control device for controlling the amount of power delivered from an AC power source to an electrical load, the load control device comprising:
- a thyristor having first and second main load terminals adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the thyristor having a gate for conducting a gate current to render the thyristor conductive;
a gate coupling circuit comprising two MOS-gated transistors coupled in anti-series connection between the first main load terminal and the gate of the thyristor, the gate coupling circuit comprising a control input for receiving a drive voltage, the MOS-gated transistors operable to conduct the gate current through the gate of the thyristor in response to the drive voltage; and
a control circuit coupled to at least one of the main load terminals of the thyristor, the control circuit further coupled to the control input of the gate coupling circuit and operable to generate the drive voltage, the control circuit operable to control the drive voltage to cause the MOS-gated transistors to conduct the gate current to render the thyristor conductive at a firing time during a half cycle of the AC power source, the control circuit operable to control the drive voltage to allow the MOS-gated transistors to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle.
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Accused Products
Abstract
A two-wire load control device (such as, a dimmer switch) for controlling the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) includes a thyristor coupled between the source and the load, a gate coupling circuit coupled between a first main load terminal and the gate of the thyristor, and a control circuit coupled to a control input of the gate coupling circuit. The control circuit generates a drive voltage for causing the gate coupling circuit to conduct a gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, and to allow the gate coupling circuit to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle, where the gate coupling circuit conducts approximately no net average current to render and maintain the thyristor conductive.
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Citations
30 Claims
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1. A load control device for controlling the amount of power delivered from an AC power source to an electrical load, the load control device comprising:
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a thyristor having first and second main load terminals adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the thyristor having a gate for conducting a gate current to render the thyristor conductive; a gate coupling circuit comprising two MOS-gated transistors coupled in anti-series connection between the first main load terminal and the gate of the thyristor, the gate coupling circuit comprising a control input for receiving a drive voltage, the MOS-gated transistors operable to conduct the gate current through the gate of the thyristor in response to the drive voltage; and a control circuit coupled to at least one of the main load terminals of the thyristor, the control circuit further coupled to the control input of the gate coupling circuit and operable to generate the drive voltage, the control circuit operable to control the drive voltage to cause the MOS-gated transistors to conduct the gate current to render the thyristor conductive at a firing time during a half cycle of the AC power source, the control circuit operable to control the drive voltage to allow the MOS-gated transistors to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A load control circuit for controlling the amount of power delivered from an AC power source to an electrical load to a desired amount of power, the load control circuit comprising:
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a thyristor having first and second main load terminals adapted to be coupled in series electrical connection between the AC power source and the electrical load for conducting a load current from the AC power source to the electrical load, the thyristor having a gate for conducting a gate current to render the thyristor conductive; first and second MOS-gated transistors coupled in anti-series connection between the first main load terminal and the gate of thyristor, each of the MOS-gated transistors rendered conductive when a voltage at a gate of the MOS-gated transistor exceeds a gate threshold voltage; and first and second gate resistors coupled together at a junction, the first gate resistor coupled between the gate of the first MOS-gated transistor and the junction of the first and second gate resistors, the second gate resistor coupled between the gate of the second MOS-gated transistor and the junction of the first and second gate resistors, the junction of the first and second gate resistor operable to receive a drive voltage; wherein the MOS-gated transistors are rendered conductive to conduct the gate current through the gate of the thyristor when the magnitude of the drive voltage is driven above the gate threshold voltage at a firing time during a half cycle of the AC power source, and to continue to conduct the gate current while the magnitude of the drive voltage is maintained above the gate threshold voltage for approximately the remainder of the half cycle. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification