A load control device may control the amount of power provided to an electrical load utilizing a phase control signal that operates in a reverse phase control mode, a center phase control mode, and a forward phase control mode. A load control device may be configured to determine that the electrical load should be operated via a phase control signal operating in a forward phase-control mode. After determining to operate the electrical load via the phase control signal in the forward phase-control mode, the load control device may provide the phase control signal in a reverse phase-control mode for a predetermined period of time to the electrical load, for example, to charge a bus capacitor of the electrical load. Subsequently, the load control device may be configured to switch the phase control signal to the forward phase-control mode and provide the phase control signal in the forward phase-control mode to the electrical load.

A bidirectional switch is switched so as to conduct and interrupt a bidirectional current between a pair of input terminals. A power supply is electrically connected between the pair of input terminals and produces control power by electric power from an AC power supply. A controller receives the control power from the power supply to be activated. The controller causes the bidirectional switch to be in an off-state from a start point of a half cycle of AC voltage to a first time point when first time elapses. The controller causes the bidirectional switch to be in an on-state from the first time point to a second time point when second time according to the dimming level elapses. The controller causes the bidirectional switch to be in an off-state from the second time point to an end point of the half cycle.

Light-dimming device includes: first and second terminals; switch including switching device connected between terminals; adjuster for varying conduction angle of switch; controller for controlling switch and power supply module for supplying power to controller. Controller includes zero-cross detection circuit for detecting zero-cross of AC voltage, control circuit for generating PWM signal of on-duty ratio corresponding to conduction angle from adjuster, and driver circuit for turning device on and off by PWM signal. Controller allows device to conduct and then turn off within variable period of time, from start of half cycle of AC voltage, shorter than half cycle. Circuit starts generation of pulse in PWM signal when prescribed period of time, shorter than variable period of time, from zero-cross of voltage elapses.

A two-wire load control device (such as, a dimmer switch) for controlling the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) includes a thyristor coupled between the source and the load, a gate coupling circuit coupled between a first main load terminal and the gate of the thyristor, and a control circuit coupled to a control input of the gate coupling circuit. The control circuit generates a drive voltage for causing the gate coupling circuit to conduct a gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, and to allow the gate coupling circuit to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle, where the gate coupling circuit conducts approximately no net average current to render and maintain the thyristor conductive.

A load control device for controlling power delivered from an AC power source to an electrical load includes a thyristor, a first current path for conducting current through a gate terminal of the thyristor, and a control circuit for controlling the first current path to conduct a pulse of current through the gate terminal to render the thyristor conductive at a firing time during a present half cycle. The first current path is able to conduct at least one other pulse of current through the gate terminal between the firing time, and a second time that occurs before an end of the present half-cycle, but is prevented from conducting pulses of current between the second time and the end of the present half-cycle. The load control device includes a second current path for conducting current through the electrical load if the thyristor becomes and remains non-conductive during the present half-cycle.

A load control device coupled between an AC power source and an electrical load may operate in a three-wire mode or a two-wire mode based on whether the load control device is connected to a neutral side of the AC power source. The load control device may further comprise first and second zero-cross detect circuits to be respectively used in the two-wire mode or the three-wire mode, and a neutral wire detect circuit configured to generate a neutral-wire detect signal indicating whether the load control device is connected to the neutral side of the AC power source. A control circuit of the load control device may determine whether the load control device should operate in the two-wire mode or in the three-wire mode in response to the neutral-wire detect signal.

A load control device may control the amount of power provided to an electrical load utilizing a phase control signal that operates in a reverse phase control mode, a center phase control mode, and a forward phase control mode. A load control device may be configured to determine that the electrical load should be operated via a phase control signal operating in a forward phase-control mode. After determining to operate the electrical load via the phase control signal in the forward phase-control mode, the load control device may provide the phase control signal in a reverse phase-control mode for a predetermined period of time to the electrical load, for example, to charge a bus capacitor of the electrical load. Subsequently, the load control device may be configured to switch the phase control signal to the forward phase-control mode and provide the phase control signal in the forward phase-control mode to the electrical load.

A microcontroller receives a LINE SYNC signal and a dimmer control voltage input and controls output switch timing of an output FET switch to generate a reverse phase PWM dimming signal for supply to associated LED driver apparatus.

A two-wire lighting control device, may include a controllably conductive device, a signal generation circuit, and a filter circuit. The controllably conductive device may apply an AC line voltage to a load, being conductive for a first duration of time and non-conductive for a second duration of time within a half-cycle of the AC line voltage. The signal generation circuit may generate a non-zero-magnitude signal. And, the filter circuit may receive a signal from the controllably conductive device during the first duration of time and the non-zero-magnitude signal from the signal generation circuit during the second duration of time. The non-zero-magnitude signal may, in effect, fill-in or complement the signal from the controllably conductive device, and any delay variation as a function of the firing angle of the controllably conductive device through the filter circuit may be mitigated by the presence of the non-zero-magnitude signal.

A light-dimming device includes a switch including a switching device, a controller, and a power supply module. The power supply module includes a capacitor to be charged by a constant voltage circuit. The controller includes a driver circuit, a zero-cross detection circuit, a detecting circuit, and a control circuit, and receive electric power from the capacitor. The driver circuit drives the switching device in accordance with a PWM signal. The control circuit starts generation of a pulse, to be contained in the PWM signal, for turning on the switching device after the zero-cross detection circuit detects zero-cross and also a voltage across the capacitor is threshold or more.