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Load control device for high-efficiency loads

  • US 8,957,662 B2
  • Filed: 04/27/2012
  • Issued: 02/17/2015
  • Est. Priority Date: 11/25/2009
  • Status: Active Grant
First Claim
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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:

  • 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 coupled to conduct the gate current through the gate of the thyristor;

    a controllable switching circuit coupled between the gate coupling circuit and the gate of the thyristor for conducting the gate current when the controllable switching circuit is conductive; and

    a control circuit operable to render the controllable switching circuit conductive and to control the gate coupling circuit to conduct the gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, the control circuit continuing to control the gate coupling circuit, such that the gate coupling circuit is able to conduct the gate current again after the firing time, the control circuit rendering the controllable switching circuit non-conductive before the end of the half-cycle, such that the gate coupling circuit is not able to conduct the gate current through the gate of the thyristor after the controllable switching circuit becomes non-conductive.

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