THREE-WAY SWITCHING CIRCUIT HAVING DELAY FOR INRUSH CURRENT PROTECTION

摘要

A three-way load control device may be coupled to a circuit including an AC power source, an electrical load, and an external single-pole double-throw (SPDT) three-way switch. The load control device may include a three-way switching circuit comprising an internal SPDT switch, a relay coupled to the internal SPDT switch, a turn-on delay circuit responsive to a voltage at a movable contact of the internal SPDT switch, and a turn-off delay circuit responsive to voltages at fixed contacts of the internal SPDT switch. The turn-on delay circuit renders the relay conductive after a turn-on delay from when either the internal SPDT switch or the external three-way switch is actuated to turn the electrical load on. The turn-off delay circuit renders the relay non-conductive after a turn-off delay from when either the internal SPDT switch or the external three-way switch is actuated to turn off the electrical load.

主权项

1. A load control device adapted to be coupled to a circuit comprising an AC power source, an electrical load, and an external single-pole double-throw (SPDT) three-way switch, the external three-way switch comprising a first fixed contact, a second fixed contact, and a movable contact adapted to be coupled to either the AC power source or the electrical load, and the external three-way switch comprising 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 load control device comprising:
a first terminal adapted to be coupled to the other of the AC power source or the electrical load to which the three-way switch is not coupled so as to complete the circuit; a second terminal adapted to be coupled to the first fixed contact of the external three-way switch; a third terminal adapted to be coupled to the second fixed contact of the external three-way switch; and a switching circuit comprising:
an internal SPDT switch comprising a movable contact and two fixed contacts coupled to the respective second and third terminals;a relay comprising a first mechanical switch coupled in series between the first terminal and the movable contact of the internal SPDT switch;a turn-on delay circuit responsive to a voltage at the movable contact of the internal SPDT switch, the turn-on delay circuit adapted to render the relay conductive after a turn-on delay from when either the internal SPDT switch is actuated to turn on the electrical load or the external three-way switch is actuated to turn on the electrical load; anda turn-off delay circuit responsive to voltages at both of the fixed contacts of the internal SPDT switch, the turn-off delay circuit adapted to render the relay non-conductive after a turn-off delay from when either the internal SPDT switch is actuated to turn off the electrical load or the external three-way switch is actuated to turn off the electrical load.