A load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.

A multiple location load control system may comprise a main load control device and an accessory load control device. The main load control device may control an amount of power delivered to an electrical load from an AC power source using a control circuit and a controllably conductive device. The accessory load control device may be coupled to the main load control device via an accessory terminal. The accessory load control device may detect a user input for changing a characteristic of the electrical load and may send a signal to the main load control device indicating the user input. The main load control device may detect a pattern of the signal based on a threshold and further determine the user input in response to the detected pattern. The main load control device may adjust the threshold based on line/load conditions of the multiple location load control system.

A single fire-wire bi-directional power fetching and dimmer control system, comprising: a dimmer circuit, that includes at least a dimmer driver and two connected bi-directional power electronic components; a single fire-wire bi-directional power fetching module, connected in series between the two bi-directional power electronic components, to perform single fire-wire power fetching when the dimmer circuit is conducting; a high side buck, connected in parallel to the dimmer circuit; and a DC to DC converter, with input end of the converter used for fetching power connected to the single fire-wire bi-directional power fetching module, and the high side buck; and with output end of the converter used for supplying power connected to the dimmer driver of the dimmer circuit. As such, single fire-wire bi-directional dimming can be performed, to raise significantly its range of control, while fetching enough power to drive Wi-Fi and 5G communication.

A bidirectional switch switched to conduct and interrupt a bidirectional current between a pair of input terminals. An input device receives a dimming level representing a value of light output of the load. A controller controls the bidirectional switch according to the dimming level. The controller controls the bidirectional switch to keep the bidirectional switch in an off-state from a start point of a half cycle of the AC voltage of the AC power supply to a first time point when a first time period therefrom elapses, and to turn the bidirectional switch to an on-state at the first time point. The controller turns the bidirectional switch to the off-state at a second time point when a second time period elapses from the first time point. The controller keeps the bidirectional switch in the off-state from the second time point to an end point of the half cycle.

A lighting device, such as a two-wire lighting control device, may include a controllably conductive device and a control circuit. The controllably conductive device may supply an AC line voltage to a load in response to a dive signal such that the controllable conductive device is non-conductive for a first duration of time and conductive for a second duration of time within a half-cycle of the AC line voltage. The control circuit may receive a signal from the controllably conductive device that represents a voltage developed across the controllable conductive device during the first duration of time. The control circuit may generate a sine-wave-shaped signal that complements the voltage developed across the controllably conductive device during the second duration of time. The control circuit may also filter the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time.

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 multiple location load control system may comprise a main load control device and an accessory load control device. The main load control device may control an amount of power delivered to an electrical load from an AC power source using a control circuit and a controllably conductive device. The accessory load control device may be coupled to the main load control device via an accessory terminal. The accessory load control device may detect a user input for changing a characteristic of the electrical load and may send a signal to the main load control device indicating the user input. The main load control device may detect a pattern of the signal based on a threshold and further determine the user input in response to the detected pattern. The main load control device may adjust the threshold based on line/load conditions of the multiple location load control system.

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 load control device for controlling the power delivered from an AC power source to an electrical load includes a thyristor, a gate coupling circuit for conducting a gate current through a gate of the thyristor, and a control circuit for controlling the gate coupling circuit to conduct the gate current through a first current path to render the thyristor conductive at a firing time during a half cycle. The gate coupling circuit is able to conduct the gate current through the first current path again after the firing time, but the gate current is not able to be conducted through the gate from a transition time before the end of the half-cycle until approximately the end of the half-cycle. The load current is able to be conducted through a second current path to the electrical load after the transition time until approximately the end of the half-cycle.

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 a first time period elapses. The controller causes the bidirectional switch to be in an on-state from the first time point to a second time point when a second time period 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.