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Load control device for high-efficiency loads

  • US 10,128,772 B2
  • Filed: 04/06/2018
  • Issued: 11/13/2018
  • Est. Priority Date: 11/25/2009
  • Status: Active Grant
First Claim
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1. A load control device for controlling power delivered from an AC power source to an electrical load, the load control device comprising:

  • a thyristor adapted to be electrically coupled between the AC power source and the electrical load, the thyristor having first and second main terminals through which current can be conducted to energize the electrical load and a gate terminal through which current can be conducted to render the thyristor conductive;

    a gate coupling circuit electrically coupled between the first main terminal and the gate terminal of the thyristor to conduct current through the gate terminal of the thyristor;

    a controllable switching circuit, separate from and independently controllable in relation to the gate coupling circuit, and electrically coupled between the first and second main terminals of the thyristor; and

    a control circuit configured to render the gate coupling circuit conductive to conduct a pulse of current through the gate terminal of the thyristor to render the thyristor conductive at a firing time during a present half-cycle of the AC power source, the control circuit configured to control the gate coupling circuit to allow the gate coupling circuit to conduct at least one other pulse of current through the gate terminal of the thyristor again after the firing time until a transition time before an end of the present half-cycle;

    wherein the control circuit is configured to render the gate coupling circuit non-conductive between approximately the transition time and the end of the present half-cycle to prevent the gate coupling circuit from conducting pulses of current through the gate terminal of the thyristor between approximately the transition time and the end of the present half-cycle, the control circuit configured to render the controllable switching circuit conductive to conduct current through the electrical load between approximately the transition time and the end of the present half-cycle.

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