Dimmer switch for use with lighting circuits having three-way switches

A dimmer switch adapted to be coupled to a circuit including an AC power source having a hot connection and a neutral connection, a load, 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 dimmer switch comprising:

• a first load terminal adapted to be coupled to either the power source or the load to which the three-way switch is not coupled;
• a second load terminal adapted to be coupled to the first fixed contact of the three-way switch;
• a third load terminal adapted to be coupled to the second fixed contact of the three-way switch;
• a controllably conductive device electrically coupled to the first, second, and third load terminals, the controllably conductive device having a conductive state in which the controllably conductive device is controlled so as to be operable to deliver a desired amount of power to the load and a non-conductive state in which the controllably conductive device is controlled so as to be operable to deliver substantially no power to the load, the controllably conductive device arranged such that when the controllably conductive device is in the conductive state and the dimmer switch is coupled to the circuit, the controllably conductive device is operable to allow a current to the load to flow between the first load terminal and the second load terminal or between the first load terminal and the third load terminal for at least a portion of each half-cycle of the AC power source;
• a sensing device electrically coupled to at least one of the second load terminal and the third load terminal, such that when the at least one of the second load terminal and the third load terminal is coupled to the three-way switch, the sensing device is operable to sense electrical continuity between the hot connection and the neutral connection of the power source through the controllably conductive device and the load;
• a controller operably coupled to the controllably conductive device and to the sensing device, the controller operable to control the controllably conductive device in response to an output of the sensing device;
• and
• a power supply electrically coupled in shunt electrical connection with the controllably conductive device and operable to provide power to the controller.

A method for controlling a load in a circuit comprising an AC power source, the load, a dimmer switch, 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:

• providing a first load terminal on the dimmer switch, 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 dimmer switch, 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 dimmer switch, the third load terminal adapted to be coupled to the second fixed contact of the three-way switch;
• electrically coupling a controllably conductive device to the first, second, and third load terminals, the controllably conductive device having a conductive state in which the controllably conductive device is controlled so as to be operable to deliver a desired amount of power to the load and a non-conductive state in which the controllably conductive device is controlled so as to be operable to deliver substantially no power to the load;
• sensing an electrical characteristic associated with at least one of the second load terminal and the third load terminal when the at least one of the second load terminal and the third load terminal is coupled to the three-way switch;
• and
• controlling the controllably conductive device in accordance with the sensed electrical characteristic, such that the controllably conductive device is operable to allow a current through the load to flow between the first load terminal and the second load terminal, or between the first load terminal and the third load terminal for at least a portion of each half-cycle of the AC power source.

A system for supplying power to a load from an AC power source comprising:

• 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 dimmer switch 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 electrically coupled such that when the first controllably conductive device is in a conductive state, a desired amount of power is capable of being delivered to the load, and when the first controllably conductive device is in a non-conductive state, substantially no power is capable of being delivered to the load;
• a controller electrically coupled to the first controllably conductive device and operable to control the first controllably conductive device;
• and
• a power supply electrically coupled in shunt electrical connection with the first controllably conductive device and operable to provide power to the controller;
• 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 the first controllably conductive device is operable to allow a current to the load to flow through the second load terminal for at least a portion of each half-cycle of the AC power source when the first controllably conductive device is in the conductive state;
• and
• wherein 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 first controllably conductive device is operable to allow the current to the load to flow through the third load terminal for at least a portion of each half-cycle of the AC power source when the first controllably conductive device is in the conductive state.