Patent ID: 7847440
Filing Date: 2010-12-07
Classification: H05B,Y02B

Abstract:
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 (SPDT) three-way switch, the AC power source generating an AC line voltage for powering the load, the SPDT three-way switch comprising a first fixed contact, a second fixed contact, and a moveable contact adapted to be coupled to either the power source or the load, the SPDT three-way switch having a first state in which the moveable contact is contacting the first fixed contact and a second state in which the moveable contact is contacting the second fixed contact, the load control device comprising: a first load terminal adapted to be coupled to one of the power source or the load to which the SPDT three-way switch is not coupled; a second load terminal adapted to be coupled to the first fixed contact of the SPDT three-way switch; a third load terminal adapted to be coupled to the second fixed contact of the SPDT three-way switch; a first controllably conductive device having a conductive state and a non-conductive 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, the first controllably conductive device is operable to allow a load current to flow between the first load terminal and the second load terminal for at least a portion of each half-cycle of the AC line voltage, the first controllably conductive device having a first control input and operable to enter the conductive state in response to a first gate current conducted through the first control input; a second controllably conductive device having a conductive state and a non-conductive 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 second controllably conductive device is operable to allow the load current to flow between the first load terminal and the third load terminal for at least a portion of each half-cycle of the AC line voltage, the second controllably conductive device having a second control input and operable to enter the conductive state in response to a second gate current conducted through the second control input; and a controller operable to control the first and second controllably conductive devices to control the load between an on state and an off state, the controller operable to drive the first controllably conductive device to change the first controllably conductive device from the non-conductive state to the conductive state each half-cycle of the AC line voltage, the controller operable to determine, in response to the magnitude of the first gate current through the first control input of the first controllably conductive device, whether the first controllably conductive device is presently conducting current to the load.