In order to reduce energy loss of a tapped linear driver, it is proposed an LED lighting circuit, comprising an input (Vbus, GND) adapted to receive an input voltage, a plurality of LED segments (LED1, LED2, LED3, LED) connected in series and to the input, a buffer component (C9) connected to an anode and a cathode of a series string of at least two of the plurality of LED segments with respective switches, a current source circuit (B1) in series connection with a parallel connection of the buffer component and the at least two LED segments, across the input; further comprising a further buffer component (C5) across the current source circuit (B1), wherein said buffer component (C9) and the further buffer component (C5) is in series connection.

A series-wired LED light string formed of a plurality of LEDs connected in series with a current limiting resistor. A resistive component is electrically connected across each LED and serves as a shunt to electrically bypass a failed LED to keep the remaining LEDs in the light string fully illuminated. The LED light string has only two wires and is powered by a full wave rectified voltage, generated external to the light string.

A light-emitting diode (LED) driving device and a short protection method for a driving device are provided. The driving device includes an LED module, a driving circuit, a reference voltage setting circuit, a voltage comparison circuit, and a power supply. A first node of the LED module receives a lighting voltage, and a second node of the LED module has a first voltage. The reference voltage setting circuit receives the lighting voltage to generate a reference voltage. The voltage comparison circuit determines whether the first voltage is greater than the reference voltage when the LED module is turned off. When the first voltage is greater than the reference voltage, the voltage comparison circuit generates a short signal. The power supply supplies power to the LED module and determines whether to shut down the power of the LED driving device according to the short signal.

An electrical circuit is described for detection of an electrical hazard condition of a load 20, in particular of an OLED lighting element comprising driving terminals A, C. An electrical hazard condition, such as an overvoltage or short circuit is to be detected between terminals 22a, 22b of the circuit. A disabling element 24 is connected to one of the terminals 22a, 22b to disable the load. A monitoring circuit is connected to monitor a voltage V or current magnitude at at least one of the terminals 22a, 22b. The monitoring circuit comprises a maximum or minimum value detector 26 to deliver a maximum or minimum value V.sub.max of the voltage or current magnitude over time. The monitoring circuit is disposed to monitor the maximum or minimum value V.sub.max to detect the electrical hazard condition. A monitoring circuit is connected to activate the disabling element 24 if an electrical hazard condition is detected. The electrical circuit, a lighting arrangement including an LED or OLED lighting element and the electrical circuit, and a detection method allows to operate a load with different types of power supply, in particular also by PWM.

A decorative light string is provided that includes a plurality of light emitting diode (LED) illumination assemblies electrically connected in series and a stabilizing current or voltage circuit. Each of the plurality of LED illumination assemblies includes an LED. The stabilizing current or voltage circuit is electrically connected in series with the plurality of LED illumination assemblies. The stabilizing current or voltage circuit is configured to receive input power from an input power source and configured to supply a stabilized current or voltage to the plurality of LED illumination assemblies that provides a stable supply even with input power source fluctuations. Power fluctuations from an input power source can prevent the decorative light string from maintaining a desired brightness and desired LED life unless the voltage or current to the LED illumination assemblies is stabilized.

A decorative light string is provided that includes a plurality of light emitting diode (LED) illumination assemblies electrically connected in series and a stabilizing current or voltage circuit. Each of the plurality of LED illumination assemblies includes an LED. The stabilizing current or voltage circuit is electrically connected in series with the plurality of LED illumination assemblies. The stabilizing current or voltage circuit is configured to receive input power from an input power source and configured to supply a stabilized current or voltage to the plurality of LED illumination assemblies that provides a stable supply even with input power source fluctuations. Power fluctuations from an input power source can prevent the decorative light string from maintaining a desired brightness and desired LED life unless the voltage or current to the LED illumination assemblies is stabilized.

An optoelectronic circuit includes at least one first and second light emitting diodes; a switch arrangement connected between the first and second diodes and configured to switch over the first and second diodes between series and parallel circuits depending on a predefined ambient parameter; and a current matching circuit for matching the currents through the first and second diodes in case of parallel connection. The current matching circuit includes a current mirror circuit, including first and second current mirror transistors connected via its collector terminal to the first/second diodes, respectively. The arrangement includes a diode/a switch for connecting the first diode in series with the second diode and is configured to form the series circuit including the first and second diodes whilst bypassing the current matching circuit so that, in case of series connection, the first transistor is switched in a high-resistance fashion and the second transistor is short-circuited.

The invention discloses an electric power supply device for a plurality of light sources on a motor vehicle. The device comprises a plurality of means for the control of the electric power supply of at least one of said light sources respectively. The control means each comprise diagnostic means which are configured to deliver a diagnostic signal for said light source. According to the invention, the device is designed to deliver two binary signals for the identification of a partial failure and/or a total failure of light sources.

A light tube apparatus includes a tubular housing, a LED module, an EMI circuit, a rectifier circuit, a filter circuit, a conversion circuit, a safety circuit and a PWM modulation circuit. The safety circuit is connected to a dimming signal from a dimmer for preventing an incorrect connection when the dimmer is connected in wrong direction causing loop breakage. The PWM modulation circuit is connected to the conversion circuit and the safety circuit for performing a pulse width modulation for the dimming signal supplied to the conversion circuit for adjusting a luminance level of the LED module.

A light tube apparatus includes a tubular housing, a LED module, an EMI circuit, a rectifier circuit, a filter circuit, a conversion circuit, a safety circuit and a PWM modulation circuit. The safety circuit is connected to a dimming signal from a dimmer for preventing an incorrect connection when the dimmer is connected in wrong direction causing loop breakage. The PWM modulation circuit is connected to the conversion circuit and the safety circuit for performing a pulse width modulation for the dimming signal supplied to the conversion circuit for adjusting a luminance level of the LED module.