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.

A dimming control method and a dimming circuit are used to control the brightness of a LED. The dimming circuit includes a power conversion unit having an input end, an output end, an inductor, and a switch. When the dimming current signal is higher than or equal to a first current threshold, the switch is controlled such that the power conversion unit operates in a continuous Conduction mode or a boundary Conduction mode; when the dimming current signal is lower than the first current threshold, the switch is controlled such that the power conversion unit operates in a discontinuous Conduction mode; and when the dimming current signal is lower than a second current threshold, the switch is controlled such that the power conversion unit operates in a chopping control mode.

A dimming control method and a dimming circuit are used to control the brightness of a LED. The dimming circuit includes a power conversion unit having an input end, an output end, an inductor, and a switch. When the dimming current signal is higher than or equal to a first current threshold, the switch is controlled such that the power conversion unit operates in a continuous Conduction mode or a boundary Conduction mode; when the dimming current signal is lower than the first current threshold, the switch is controlled such that the power conversion unit operates in a discontinuous Conduction mode; and when the dimming current signal is lower than a second current threshold, the switch is controlled such that the power conversion unit operates in a chopping control mode.

In an example, a system includes a single-output flyback/LLC converter adapted to be coupled to an alternating current (AC) power supply. The system also includes a buck regulator coupled to the single-output flyback/LLC converter. The system includes a first LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to the buck regulator. The system also includes a second LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to a ground terminal.

In an example, a system includes a single-output flyback/LLC converter adapted to be coupled to an alternating current (AC) power supply. The system also includes a buck regulator coupled to the single-output flyback/LLC converter. The system includes a first LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to the buck regulator. The system also includes a second LED including an anode coupled to the single-output flyback/LLC converter and a cathode coupled to a ground terminal.

A light emitting load driving device includes a first constant current source structured to be serially connected to a first light emitting load group; a second constant current source structured to be serially connected to a second light emitting load group; a first load connection terminal structured to be connected to the first light emitting load group; a second load connection terminal structured to be connected to the second light emitting load group; and a control circuit structured to be supplied a first voltage applied to the first load connection terminal, a second voltage applied to the second load connection terminal, and a reference voltage applied to the control circuit, wherein the control circuit is structured to select a minimum voltage between the first voltage and the second voltage, and the control circuit is structured to equalize the minimum voltage and the reference voltage.

A light-emitting diode (LED) tube lamp and an electric leakage protection circuit are provided. The LED tube lamp. The LED tube lamp includes a leakage detecting module and a driving module comprising a Type A+B driving circuit. The leakage detecting module is connected with a power supply. The driving module is electrically connected with the leakage detecting module. The leakage detecting module detects a signal related to the output current of the power supply, and when the signal related to the output current of the power supply exceeds a reference signal, the leakage detecting module limits the current on a power loop connected to the power supply by periodically turning off a switch electrically connected to the power loop in series.

A light-emitting diode (LED) tube lamp and an electric leakage protection circuit are provided. The LED tube lamp. The LED tube lamp includes a leakage detecting module and a driving module comprising a Type A+B driving circuit. The leakage detecting module is connected with a power supply. The driving module is electrically connected with the leakage detecting module. The leakage detecting module detects a signal related to the output current of the power supply, and when the signal related to the output current of the power supply exceeds a reference signal, the leakage detecting module limits the current on a power loop connected to the power supply by periodically turning off a switch electrically connected to the power loop in series.

A switch control circuit and a switch control method are provided. In this circuit, compositions that sense a drain voltage of a switch device are added in a QR Buck Converter switch control circuit. A first resistor, a second switch, a second resistor are electrically connected to a drain terminal of a switch device to sense the 0A state of an inductor current. On the basis of a detection result, the switch control circuit turns on the switch device when an inductor current is 0A, and a drain sensing voltage (ZCD) is less than a predetermined reference voltage (REF).

An apparatus for efficiently driving visual displays via light-emitting devices may include (1) at least one light-emitting device, (2) a buck driver circuit electrically coupled to the light-emitting device, wherein the buck driver circuit includes an inductor, and (3) a boost circuit electrically coupled between the buck driver circuit and a power source, wherein the boost circuit includes an additional inductor. Various other apparatuses, systems, and methods are also disclosed.