Abstract: A lighting unit includes a power supply that provides a maximum voltage and multiple LED lighting circuits. Each of the LED lighting circuits includes an LED string, multiple switches, a switching sequencer and a switch controller. The LED string includes multiple series-connected emitters having a total forward voltage that exceeds the maximum voltage of the power supply. Each of the switches is coupled in parallel with a respective LED of the LED string. The switching sequencer provides a sequence of switching patterns such that a total forward voltage of simultaneously active LEDs in each switching pattern does not exceed the maximum voltage of the power supply. The switch controller actuates switches according to each of the switching patterns in the sequence. The LED string of each of the plurality of LED lighting circuits is arranged in a two-dimensional array.

Abstract: An LED driver implements a first constant-current drive scheme for a first range of sensed voltages up to a threshold voltage. After this, a second drive scheme is implemented with a current lower than the constant current of the first drive scheme.

Abstract: 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 Vmax of the voltage or current magnitude over time. The monitoring circuit is disposed to monitor the maximum or minimum value Vmax to detect the electrical hazard condition. A monitoring circuit is connected to activate the disabling element 24 if an electrical hazard condition is detected.

Abstract: A short detection circuit is provided for detecting a short circuit condition of an LED. A voltage threshold is set which is dependent on the LED operating current, such that there are at least two different voltage thresholds at two different LED operating currents. This means false detections can be reduced and the LED current operating range can be increased over which the short detection functions.

Abstract: An LED driver implements a first constant-current drive scheme for a first range of sensed voltages up to a threshold voltage. After this, a second drive scheme is implemented with a current lower than the constant current of the first drive scheme.

Abstract: An LED driver uses a current setting passive component to set an operating current, and also uses a voltage setting passive component to derive an acceptable voltage range. A current driver is then controlled to deliver the current setting and monitor that a voltage being provided is within the acceptable voltage range.

Abstract: A short detection circuit is provided for detecting a short circuit condition of an LED. A voltage threshold is set which is dependent on the LED operating current, such that there are at least two different voltage thresholds at two different LED operating currents. This means false detections can be reduced and the LED current operating range can be increased over which the short detection functions.

Abstract: 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 Vmax of the voltage or current magnitude over time. The monitoring circuit is disposed to monitor the maximum or minimum value Vmax to detect the electrical hazard condition. A monitoring circuit is connected to activate the disabling element 24 if an electrical hazard condition is detected.

Abstract: The invention relates to a current determination apparatus for determining an operational driving current for driving a light source of a group of light sources. A same color shift function defining a light color shift depending on a driving current can be provided for all light sources of the group. An operational driving current is determined based on the color shift function such that the light color (43) of the light source of the group of light sources is shifted from a nominal color, which may be specific for each light source, to a light color (45) within a target color window (41). Since for the different light sources the same color shift function can be used, a determination of individual operational driving currents such that the light sources of the group emit light having substantially the same color can be simplified.

Abstract: The present invention relates to a method for adjusting a color point (507, 509, 511) of light emitted (111) from an organic light emitting diode OLED (107) by using current (115) with a modulated waveform for driving the OLED (107), wherein the waveform is characterized by at least three different parameters, and wherein the color point (507, 509, 511) is located in a color space, the method comprising: —defining a color point target (501); —adjusting simultaneously the at least three parameters to tune the waveform such that the resulting light output of the OLED (107) is lying within a predefined area around the color point target and for which the brightness of the OLED (107) remains at a predefined level; and —employing the tuned waveform to provide the current (115) with the modulated waveform to the OLED (107).

Abstract: The present invention relates to a method for adjusting a color point (507, 509, 511) of light emitted (111) from an organic light emitting diode OLED (107) by using current (115) with a modulated waveform for driving the OLED (107), wherein the waveform is characterized by at least three different parameters, and wherein the color point (507, 509, 511) is located in a color space, the method comprising: - defining a color point target (501);-adjusting simultaneously the at least three parameters to tune the waveform such that the resulting light output of the OLED (107) is lying within a predefined area around the color point target and for which the brightness of the OLED (107) remains at a predefined level; and-employing the tuned waveform to provide the current (115) with the modulated waveform to the OLED (107).

Abstract: The invention relates to a current determination apparatus for determining an operational driving current for driving a light source of a group of light sources. A same color shift function defining a light color shift depending on a driving current can be provided for all light sources of the group. An operational driving current is determined based on the color shift function such that the light color (43) of the light source of the group of light sources is shifted from a nominal color, which may be specific for each light source, to a light color (45) within a target color window (41). Since for the different light sources the same color shift function can be used, a determination of individual operational driving currents such that the light sources of the group emit light having substantially the same color can be simplified.

Abstract: The invention relates to an electroluminescent device for emitting light having an adjustable color point. An electroluminescent region (1) emits light in response to a lighting current and a heating element (7) applies heat to the electroluminescent region A heating control unit (9) controls the heating element (7) in applying the heat in order to adjust the color point of the emitted light. The color point of the light emitted by the electroluminescent device is dependent on the temperature of the electroluminescent region (1). Since the electroluminescent device comprises a heating element (7) for applying heat to the electroluminescent region (1) and a heating control unit (9) for controlling the heating element (7) in applying the heat, the color point can be adjusted in a simple way by using the heating control unit (9).