An RF controlled lighting unit is provided, suitable for connection to at least one of a dimmer for adjusting a phase cut angle of input mains voltage in accordance with an adjustable dimming level or an electronic switch for selecting between on- and off-states. The lighting unit includes a solid state light source; a radio circuit for receiving a wireless control signal; a rectifier circuit for rectifying the input mains voltage received from the electronic switch or the dimmer; a first power converter for driving the solid state light source in response to the rectified input mains voltage and delivering power to the radio circuit; and a second power convertor for delivering power to the radio circuit when the rectified input mains voltage becomes inadequate for the first power converter due to the phase-cut angle of the rectified input mains voltage or the off-state of the electronic switch.

Disclosed is a LED DC control circuit that comprises an AC to DC circuit, a voltage division circuit, a controller and a logic circuit. The AC to DC circuit receives an AC reference voltage and generates a sine wave reference voltage and a DC reference voltage. The voltage division circuit receives the DC reference voltage and generates a threshold voltage. The controller compares the threshold voltage with the DC reference voltage to generate an inner reference voltage. The controller receives a first PWM voltage signal to accordingly sample the inner reference voltage and then output a second PWM voltage signal. The logic circuit receives the second PWM voltage signal to generate a driving voltage and a load current for driving a power switch circuit. Within each period of the sine wave reference voltage, at least one of the driving signals of the load current is a relative maximum.

The present disclosure provides a dummy load control circuit and a lighting device. The dummy load control circuit and a dummy load module are connected in parallel with a power supply input end and the dummy load control circuit includes a first switch circuit having a first switch control module so the first switch is controlled to be turned off when the power supply input end is connected to a triac dimmer, and turned on when the power supply input end is not connected to the triac dimmer, a second switch circuit having a second switch control module controlling on/off of the second switch, and a constant voltage source providing a constant voltage so the dummy load module is turned on when the first switch and the second switch are turned off, and turned off when the first switch and/or the second switch are turned on.

The present disclosure provides a dummy load control circuit and a lighting device. The dummy load control circuit and a dummy load module are connected in parallel with a power supply input end and the dummy load control circuit includes a first switch circuit having a first switch control module so the first switch is controlled to be turned off when the power supply input end is connected to a triac dimmer, and turned on when the power supply input end is not connected to the triac dimmer, a second switch circuit having a second switch control module controlling on/off of the second switch, and a constant voltage source providing a constant voltage so the dummy load module is turned on when the first switch and the second switch are turned off, and turned off when the first switch and/or the second switch are turned on.

A bleeder current control method. The bleeder current control method includes the following steps: The rectifier bridge transmits a post-bridge input signal to the power system. The shaping circuit obtains the post-bridge input signal and shapes it into a bleeder current reference signal, the bleeder current reference signal is inversely correlated with the initial post-bridge input signal. Acquiring a current sampling signal representing the bleeder current, and comparing the error of the current sampling signal with the bleeder current reference signal to obtain an error signal. The current sampling signal is controlled according to the error signal, so that the current sampling signal is output based on the waveform of the bleeder current reference signal. Thus, a reliable and full-time sine wave envelope signal is provided to the power system, so as to reduce the loss caused by the bleeder current to the power system.

A bleeder current control method. The bleeder current control method includes the following steps: The rectifier bridge transmits a post-bridge input signal to the power system. The shaping circuit obtains the post-bridge input signal and shapes it into a bleeder current reference signal, the bleeder current reference signal is inversely correlated with the initial post-bridge input signal. Acquiring a current sampling signal representing the bleeder current, and comparing the error of the current sampling signal with the bleeder current reference signal to obtain an error signal. The current sampling signal is controlled according to the error signal, so that the current sampling signal is output based on the waveform of the bleeder current reference signal. Thus, a reliable and full-time sine wave envelope signal is provided to the power system, so as to reduce the loss caused by the bleeder current to the power system.

System and method for controlling one or more light emitting diodes. For example, the system for controlling one or more light emitting diodes includes a current generator configured to generate a first current flowing through one or more light emitting diodes. The one or more light emitting diodes are configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer. Additionally, the system includes a bleeder configured to receive the rectified voltage, and a controller configured to receive a sensing voltage from the current generator and output a control signal to the bleeder. The sensing voltage indicates a magnitude of the first current.

System and method for controlling one or more light emitting diodes. For example, the system for controlling one or more light emitting diodes includes a current generator configured to generate a first current flowing through one or more light emitting diodes. The one or more light emitting diodes are configured to receive a rectified voltage generated by a rectifying bridge coupled to a TRIAC dimmer. Additionally, the system includes a bleeder configured to receive the rectified voltage, and a controller configured to receive a sensing voltage from the current generator and output a control signal to the bleeder. The sensing voltage indicates a magnitude of the first current.

Multiple current sources are coupled in series to corresponding light-emitting elements. Switching converter supplies driving voltage to the multiple light-emitting elements and current sources. Pulse modulator generates pulse signal that transits to on level when the smallest from among voltages across both ends of the multiple current sources falls to bottom limit voltage, and subsequently transits to off level. Frequency stabilization circuit controls pulse modulator such that the frequency of pulse signal approaches its target. Dummy load circuit is configured to lower driving voltage in the enable state, to be set to the enable state when switching transistor continues to be off for a predetermined time, and to be set to the disable state in response to the next turn-on of the switching transistor.

Multiple current sources are coupled in series to corresponding light-emitting elements. Switching converter supplies driving voltage to the multiple light-emitting elements and current sources. Pulse modulator generates pulse signal that transits to on level when the smallest from among voltages across both ends of the multiple current sources falls to bottom limit voltage, and subsequently transits to off level. Frequency stabilization circuit controls pulse modulator such that the frequency of pulse signal approaches its target. Dummy load circuit is configured to lower driving voltage in the enable state, to be set to the enable state when switching transistor continues to be off for a predetermined time, and to be set to the disable state in response to the next turn-on of the switching transistor.