Load control device for use with lighting circuits having three-way switches
First Claim
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.
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Accused Products
Abstract
A smart dimmer for control of a lighting load from an AC power source can replace any switch in a three-way or four-way lighting control system. The smart dimmer can be connected on the line-side or the load-side of a three-way system with a standard three-way switch in the other location. According to one embodiment of the present invention, the dimmer includes two triacs to control the intensity of the connected lighting load. The dimmer preferably includes two gate drive circuits coupled to the gates of the triacs for rendering the triacs conductive each half-cycle of the AC power source. The gate drive circuits include sensing circuits for detect whether the gates currents are flowing after the triacs are rendered conductive. A controller is operable to determine the state of the lighting load in response to whether the gate current is flowing or not flowing.
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Citations
39 Claims
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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 (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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for controlling a load in a circuit comprising an AC power source, the load, a load control device, and a single-pole double-throw three-way switch, the three-way switch comprising a first fixed contact, a second fixed contact, and a movable contact adapted to be coupled to either the power source or the load, the three-way switch having a first state in which the movable contact is contacting the first fixed contact and a second state in which the movable contact is contacting the second fixed contact, the method comprising the steps of:
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providing a first load terminal on the load control device, the first load terminal adapted to be coupled to either the power source or the load to which the three-way switch is not coupled; providing a second load terminal on the load control device, the second load terminal adapted to be coupled to the first fixed contact of the three-way switch; providing a third load terminal on the load control device, the third load terminal adapted to be coupled to the second fixed contact of the three-way switch; electrically coupling a first controllably conductive device between the first load terminal and the second load terminal, the first controllably conductive device having a conductive state and a non-conductive, the first controllably conductive device arranged such that when the first controllably conductive device is in the conductive state, 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 power source, the first controllably conductive device having a first control input; conducting a first gate current through the first control input to cause the first controllably conductive device to enter the conductive state; electrically coupling a second controllably conductive device between the first load terminal and the third load terminal, the second controllably conductive device having a conductive state and a non-conductive state, the second controllably conductive device arranged such that when the second controllably conductive device is in the conductive state, the second controllably conductive device is operable to allow the load current is operable to flow between the first load terminal and the third load terminal for at least a portion of each half-cycle of the AC power source, the second controllably conductive device having a second control input; conducting a second gate current through the second control input to cause the second controllably conductive device to enter the conductive state; monitoring the first and second gate currents; and determining, in response to the step of monitoring the first and second gate currents, whether the respective controllably conductive device is presently conducting the current to the load. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A load control system for controlling the amount of power delivered to an electrical load from an AC power source generating an AC line voltage, the load control system comprising:
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a single-pole double-throw (SPDT) three-way switch comprising a first fixed contact, a second fixed contact, and a movable 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 movable contact is contacting the first fixed contact and a second state in which the movable contact is contacting the second fixed contact; and a load control device comprising; a first load terminal adapted to be coupled to either the power source or the load to which the SPDT three-way switch is not coupled to; a second load terminal coupled to the first fixed contact of the SPDT three-way switch; a third load terminal 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 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 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, the controller operable to determine if the first controllably conductive device is presently conducting current to the load in response to the magnitude of the first gate current through the first control input of the first controllably conductive device; wherein when the SPDT three-way switch is in the first state, the controller is operable to control the first controllably conductive device such that a load current is operable to flow through the second load terminal when the first controllably conductive device is in the conductive state, and when the SPDT three-way switch is in the second state, the controller is operable to control the first controllably conductive device such that the load current is operable to flow through the third load terminal when the controllably conductive device is in the conductive state; and wherein the controller is 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, the controller further operable to determine, in response to the magnitude of the second gate current through the second control input of the second controllably conductive device, whether the second controllably conductive device is presently conducting current to the load.
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Specification