Abstract: A load control device may control power delivered to an electrical load from an AC power source. The load control device may include a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load, a zero-cross detect circuit configured to generate a zero-cross signal representative of the zero-crossings of an AC voltage. The zero-cross signal may be characterized by pulses occurring in time with the zero-crossings of the AC voltage. The load control device may include a control circuit operatively coupled to the controllably conductive device and the zero cross detect circuit. The control circuit may be configured to identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal, and may control a conductive state of the controllably conductive device based on the rising-edge time and the falling-edge time of the pulse.

Abstract: 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.

Abstract: 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.

Abstract: A load control device may control power delivered to an electrical load from an AC power source. The load control device may include a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load, a zero-cross detect circuit configured to generate a zero-cross signal representative of the zero-crossings of an AC voltage. The zero-cross signal may be characterized by pulses occurring in time with the zero-crossings of the AC voltage. The load control device may include a control circuit operatively coupled to the controllably conductive device and the zero cross detect circuit. The control circuit may be configured to identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal, and may control a conductive state of the controllably conductive device based on the rising-edge time and the falling-edge time of the pulse.

Abstract: A load control circuit having an overload circuit capable of protecting a switching element from overload conditions over a wide range of operating conditions. The overload circuit limits the maximum average power dissipation of the switching element in accordance with a comparison of an average voltage across the switching element over a half-cycle and a variable threshold. The variable threshold is determined based on an ON-state resistance of the switching element and the environment in which the switching elements are operating. The variable threshold accounts for the squared term (V2 or I2) in determining power dissipation and allows power to be determined based on average voltage.