A dimmable ballast circuit for a compact fluorescent lamp controls the intensity of a lamp tube in response to a phase-control voltage received from a dimmer switch. The ballast circuit comprises a phase-control-to-DC converter circuit that receives the phase-control voltage, which is characterized by a duty cycle defining a target intensity of the lamp tube, and generates a DC voltage representative of the duty cycle of the phase-control voltage. Changes in the duty cycle of the phase-control voltage that are below a threshold amount are filtered out by the converter circuit, while intentional changes in the duty cycle of the phase-control voltage are reflected in changes in the target intensity level and thereby the intensity level of the lamp tube.

A light-emitting diode driving module includes an LED driving circuit to activate light-emitting diodes driven by a rectified voltage, and to adjust driving current conducted through driving nodes to the light-emitting diodes depending on a voltage of a driving current setting node; and a driving current controller to control the voltage of the driving current setting node by outputting a driving current control signal. The driving current controller includes a control signal output circuit connected to a dimming node to receive a dimming signal when the rectified voltage is modulated, and to adjust the driving current control signal depending on the dimming signal; a mode detector to detect whether the rectified voltage is modulated by receiving a source voltage depending on the rectified voltage, and to enable a selection signal depending on a detection result; and a power compensator to adjust the driving current control signal when the selection signal is enabled.

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 power drawing device using a single live wire includes a first and second mechanical switches, and a power drawing circuit, wherein the first mechanical switch includes a first contact connected to a live wire, a third contact connected to a first light adjusting circuit, and a fifth contact connected to the first light adjusting circuit; the second mechanical switch includes a first contact connected to the live wire, a third contact connected to a second light adjusting circuit, a fifth contact connected to the second light adjusting circuit, and a sixth contact connected to the first mechanical switch; and the power drawing circuit includes a first terminal connected to the live wire, a second terminal connected to the second mechanical switch, a third terminal connected to the first light adjusting circuit, and a fourth terminal connected to the second light adjusting circuit.

A light-emitting diode driving module includes an LED driving circuit to activate light-emitting diodes driven by a rectified voltage, and to adjust driving current conducted through driving nodes to the light-emitting diodes depending on a voltage of a driving current setting node; and a driving current controller to control the voltage of the driving current setting node by outputting a driving current control signal. The driving current controller includes a control signal output circuit connected to a dimming node to receive a dimming signal when the rectified voltage is modulated, and to adjust the driving current control signal depending on the dimming signal; a mode detector to detect whether the rectified voltage is modulated by receiving a source voltage depending on the rectified voltage, and to enable a selection signal depending on a detection result; and a power compensator to adjust the driving current control signal when the selection signal is enabled.

A symmetry control circuit for a trailing edge phase control dimmer circuit for controlling alternating current (AC) power to a load, the symmetry control circuit including: a bias signal generator circuit configured to monitor non-conduction periods of each half cycle of said AC power for an elapsed duration of the non-conduction periods, and generate a bias signal voltage based on the elapsed duration, whereby an amplitude of the bias signal voltage is proportional to the elapsed duration of the non-conduction periods; and a bias signal converter circuit configured to convert the bias signal voltage to a bias signal current, wherein the bias signal current is added to a reference current of a conduction period timing circuit configured to determine said conduction periods, and wherein the conduction period timing circuit is configured to alter one of the conduction periods immediately following one of the non-conduction periods based on the bias signal current when added to the reference current to compensate for a phase shift of a zero-crossing of said one of the non-conduction periods corresponding to an elapsed duration of said one of the non-conduction periods so as to restore symmetry of the non-conduction periods of each half cycle of AC power.

A dimmable ballast circuit for a compact fluorescent lamp controls the intensity of a lamp tube in response to a phase-control voltage received from a dimmer switch. The ballast circuit comprises a phase-control-to-DC converter circuit that receives the phase-control voltage, which is characterized by a duty cycle defining a target intensity of the lamp tube, and generates a DC voltage representative of the duty cycle of the phase-control voltage. Changes in the duty cycle of the phase-control voltage that are below a threshold amount are filtered out by the converter circuit, while intentional changes in the duty cycle of the phase-control voltage are reflected in changes in the target intensity level and thereby the intensity level of the lamp tube.

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.

A control apparatus using variations in conduction angle as control command, wherein a conduction angle modulation module of a traditional leading edge cutoff dimmer is arranged in parallel with a resistance module, so as to enlarge the minimum conduction angle of the leading edge dimmer. The modulation range of the conduction angle of the conduction angle modulation module may be set to a smaller range, so that the modulation range of the resistance module will not be uncertain due to different setting values of the variable resistance, whereby the circuit at load end can be identified readily and function mode switching facilitated to achieve the effect of multiplexing control.

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.