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LOAD CONTROL DEVICE FOR USE WITH LIGHTING CIRCUITS HAVING THREE-WAY SWITCHES

  • US 20070262654A1
  • Filed: 06/22/2007
  • Published: 11/15/2007
  • Est. Priority Date: 06/06/2005
  • Status: Active Grant
First Claim
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1. A load control device adapted to be coupled to a circuit including an AC power source, a load, and a single-pole double-throw three-way switch, the AC power source generating an AC line voltage for powering the load, the load control device comprising:

  • first, second, and third electrical load terminals;

    a first controllably conductive device having a conductive state in which the first controllably conductive device is controlled so as to deliver a desired amount of power to the load such that the load is in an on state, and a non-conductive state in which the first controllably conductive device is controlled so as to deliver substantially no power to the load such that the load is in an off state, the first controllably conductive device electrically coupled between the first load terminal and the second load terminal such that when the first controllably conductive device is in the conductive state and the load control device is coupled to the circuit, a current to the load flows between the first load terminal and the second load terminal;

    a second controllably conductive device having a conductive state in which the second controllably conductive device is controlled so as to deliver a desired amount of power to the load such that the load is in the on state, and a non-conductive state in which the second controllably conductive device is controlled so as to deliver substantially no power to the load such that the load is in the off state, the second controllably conductive device electrically coupled between the first load terminal and the third load terminal such that when the second controllably conductive device is in the conductive state and the load control device is coupled to the circuit, the current to the load flows between the first load terminal and the third load terminal;

    a first sensing circuit electrically coupled to the second load terminal and operable to sense a first voltage at the second load terminal, the first sensing circuit characterized by a first impedance substantially larger than an impedance of the load;

    a second sensing circuit electrically coupled to the third load terminal and operable to sense a second voltage at the third load terminal, the second sensing circuit characterized by a second impedance substantially larger than the impedance of the load;

    a resistor coupled between the second and third electrical load terminals, the impedance of the resistor substantially larger than the impedance of the load; and

    a controller operable to cause a respective one of the first and second controllably conductive devices to be in the conductive state, the controller operatively coupled to the first and second sense circuits to determine the state of the load in response to the first and second sensing circuits.

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