DE102024108269A1 - LIGHTING DEVICE, METHOD FOR OPERATING A LIGHTING DEVICE AND OPTOELECTRONIC COMPONENT - Google Patents

Abstract

A lighting device (10) comprises an arrangement (15) of a plurality of light-emitting semiconductor components (100) and a uniform converter element (120) above the arrangement (15) of the plurality of light-emitting semiconductor components (100). The converter element (120) is configured to convert a first wavelength of electromagnetic radiation (18) emitted by the light-emitting semiconductor components (100) into a second wavelength. The lighting device (10) further comprises a memory device (125) configured to store measured values indicating a color locus shift as a function of a current supply. The lighting device (10) further comprises a control circuit (124) suitable for determining an operating current for each of the light-emitting semiconductor components (100) as a function of the stored color locus shift as a function of a current supply and for supplying the associated operating current to each of the light-emitting semiconductor components (100).

Description

Lighting devices comprising a large number of picture elements, or pixels, are widely used in a variety of applications, such as automotive headlights. In general, efforts are being made to provide lighting devices with a high degree of color homogeneity.

The present invention is based on the object of providing an improved lighting device and an improved method for operating a lighting device and an improved optoelectronic component.

According to embodiments, the object is achieved by the subject matter of the independent patent claims. Further developments are defined in the dependent patent claims.

According to embodiments, a lighting device comprises an arrangement of a plurality of light-emitting semiconductor components and a uniform converter element above the arrangement of the plurality of light-emitting semiconductor components. The converter element is configured to convert a first wavelength of electromagnetic radiation emitted by the light-emitting semiconductor components into a second wavelength. The lighting device further comprises a memory device and a control circuit. The memory device is configured to store measured values that indicate a color locus shift as a function of a current supply. The control circuit is configured to determine an operating current for each of the light-emitting semiconductor components as a function of the stored color locus shift as a function of a current supply and to supply the associated operating current to each of the light-emitting semiconductor components.

The control circuit can, for example, be configured to modulate the operating current by means of pulse width modulation.

For example, the control circuit may be configured to adjust an amplitude of the pulses individually according to a position of the associated light-emitting semiconductor component.

According to embodiments, the drive circuit may be configured to individually adjust a width of the pulses according to a position of the associated light-emitting semiconductor component.

For example, the control circuit can be configured to change the amplitude and/or the pulse width as a function of time.

According to embodiments, the control circuit can be configured to supply signals with different amplitudes and/or different pulse widths to different light-emitting semiconductor components.

According to further embodiments, a plurality of the light-emitting semiconductor components can also be operated in continuous-wave mode, i.e., with a current pulse with a long pulse duration. In this case, for example, the current intensity for the individual light-emitting semiconductor components can vary. According to further embodiments, the impressed current intensity can also be changed during the operating period.

According to further embodiments, the lighting device can additionally comprise a temperature measuring device. The temperature measuring device can be configured to determine an operating temperature for each of the light-emitting semiconductor components. Furthermore, the control circuit can be suitable for additionally determining the operating current as a function of the operating temperature of the associated light-emitting semiconductor component. In this way, a temperature-induced color locus shift can be compensated for. For example, the temperature measuring device can comprise a few temperature sensors, for example two temperature sensors, arranged at different locations on the lighting device. From the measured temperatures, the temperature distribution within the lighting device can be determined pixel-by-pixel using a suitable algorithm. According to further embodiments, the temperature at each light-emitting semiconductor component can be determined.

Further embodiments relate to a method for operating the lighting device, which comprises an arrangement of a plurality of light-emitting semiconductor components, a uniform converter element above the arrangement of the plurality of light-emitting semiconductor components, wherein the converter element is configured to convert a first wavelength of electromagnetic radiation emitted by the light-emitting semiconductor components into a second wavelength, and a drive circuit configured to supply each of the light-emitting semiconductor components with an associated operating current. The method comprises measuring an initial color location for each light-emitting semiconductor component. The method further comprises setting an operating current for each light-emitting semiconductor device based on measured values indicating a color locus shift as a function of current and/or operating temperature and supplying the operating current to each of the light-emitting semiconductor devices.

For example, the operating current can be supplied as a pulsed current. In this case, the method can further comprise adjusting the pulse width and/or the maximum value after a predetermined operating period.

The method may further comprise detecting an operating parameter after a predetermined operating period. For example, in this case, the operating current may be adjusted depending on the detected operating parameter. For example, the operating parameter may include an operating temperature of the light-emitting semiconductor component.

According to embodiments, a plurality of the light-emitting semiconductor devices can be operated in continuous wave mode.

Further embodiments relate to an optoelectronic component which has the lighting device as described above.

For example, the optoelectronic component can be designed as a vehicle headlight or lighting device.

According to embodiments, a lighting device comprises a light-emitting semiconductor component and a converter element above the light-emitting semiconductor component, wherein the converter element is configured to convert a first wavelength of electromagnetic radiation emitted by the light-emitting semiconductor component into a second wavelength. The lighting device further comprises a memory device configured to store measured values indicating a color locus shift as a function of a current supply, and a control circuit configured to determine an operating current as a function of the stored color locus shift and to supply the operating current to the light-emitting semiconductor component. For example, the lighting device has only a single light-emitting semiconductor component.

• 1 zeigt eine schematische Querschnittsansicht einer Leuchtvorrichtung gemäß Ausführungsformen.
• 2A veranschaulicht eine Verschiebung eines Wellenlängenpeaks in Abhängigkeit einer Stromstärke.
• 2B veranschaulicht eine Absorptionscharakteristik eines Leuchtstoffs.
• 2C zeigt Beispiele von Farbortverschiebungen in Abhängigkeit von einer Stromstärke bei verschiedenen Emissionswellenlängen.
• 3 zeigt eine schematische Draufsicht auf eine Leuchtvorrichtung gemäß Ausführungsformen.
• 4 fasst ein Verfahren gemäß Ausführungsformen zusammen.
• 5 zeigt ein optoelektronisches Bauteil gemäß Ausführungsformen.

The accompanying drawings provide an understanding of embodiments of the invention. The drawings illustrate embodiments and, together with the description, serve to explain the same. Further embodiments and many of the intended advantages will become apparent from the following detailed description. The elements and structures shown in the drawings are not necessarily drawn to scale. Like reference numerals refer to like or corresponding elements and structures.

• 1 shows a schematic cross-sectional view of a lighting device according to embodiments.
• 2A illustrates a shift of a wavelength peak as a function of current.
• 2B illustrates an absorption characteristic of a phosphor.
• 2C shows examples of color shifts depending on a current at different emission wavelengths.
• 3 shows a schematic plan view of a lighting device according to embodiments.
• 4 summarizes a method according to embodiments.
• 5 shows an optoelectronic component according to embodiments.

In the following detailed description, reference is made to the accompanying drawings, which form a part of the disclosure, and in which specific embodiments are shown for purposes of illustration. In this context, directional terminology such as "top," "bottom," "front," "back," "over," "on," "in front of," "behind," "fore," "rear," etc., refers to the orientation of the figures just described. Since the components of the embodiments can be positioned in different orientations, the directional terminology is for the purpose of explanation only and is not limiting in any way.

The description of the embodiments is not limiting, as other embodiments exist and structural or logical changes may be made without departing from the scope defined by the claims. In particular, elements of the embodiments described below may be combined with elements of other described embodiments, unless the context indicates otherwise.

The terms “wafer” or “semiconductor substrate” used in the following description may include any structure based on semiconductor materials that has a semiconductor surface Wafer and structure are understood to include doped and undoped semiconductor materials, epitaxial semiconductor layers, optionally supported by a base substrate, and further semiconductor structures. For example, a layer of a first semiconductor material may be grown on a growth substrate of a second semiconductor material, for example, a GaAs substrate, a GaN substrate, or a Si substrate, or of an insulating material, for example, on a sapphire substrate.

Depending on the intended use, the semiconductor can be based on a semiconductor material with a direct or indirect band gap. Examples of semiconductor materials particularly suitable for generating electromagnetic radiation, which can be used, for example, according to embodiments, include in particular nitride semiconductor compounds, by means of which, for example, ultraviolet, blue, or longer-wavelength light can be generated, such as GaN, InGaN, AlN, AlGaN, AlGaInN, AlGaInBN. Further examples of semiconductor materials include phosphide semiconductor compounds, by means of which, for example, green or longer-wavelength light can be generated, such as GaAsP, AlGaInP, GaP, AlGaP, as well as other semiconductor materials such as GaAs, AlGaAs, InGaAs, AlInGaAs, SiC, ZnSe, ZnO, _Ga2O3 , _diamond , hexagonal BN, and combinations of the aforementioned materials. The stoichiometric ratio of the compound semiconductor materials can vary. Further examples of semiconductor materials may include silicon, silicon-germanium, and germanium. In the context of this description, the term "semiconductor" also includes organic semiconductor materials.

The term “substrate” generally includes insulating, conductive or semiconductor substrates.

The term "vertical," as used in this description, is intended to describe an orientation that is substantially perpendicular to the first surface of a substrate or semiconductor body. The vertical direction may, for example, correspond to a growth direction during layer growth.

The terms "lateral" and "horizontal," as used in this description, are intended to describe an orientation or alignment that is substantially parallel to a first surface of a substrate or semiconductor body. This can be, for example, the surface of a wafer or a chip (die).

The horizontal direction can, for example, lie in a plane perpendicular to a growth direction when growing layers.

The memory device used in the context of this description may, in particular, be a non-volatile memory configured to permanently store stored information even without an external power supply. Examples include, for example, an EPROM ("erasable programmable read-only memory"), an EEPROM ("electrically erasable programmable read-only memory"), a Flash EEPROM, and others.

1 shows a schematic cross-sectional view of a lighting device 10 according to embodiments. The lighting device 10 comprises an arrangement 15 of a plurality of light-emitting semiconductor components 100 and a uniform converter element 120 arranged above the plurality of light-emitting semiconductor components 100. The converter element 120 is configured to convert a wavelength of the electromagnetic radiation emitted by the light-emitting semiconductor components. The lighting device 10 further comprises a drive circuit 124 adapted to individually supply an operating current to each of the light-emitting semiconductor components. Furthermore, the drive circuit 124 can be configured, for example, to modulate the operating current by means of pulse width modulation. According to further embodiments, the drive circuit 124 can also be configured to supply the operating current in continuous wave ("cw") operation.

The light-emitting semiconductor components can each be embodied as LEDs (light-emitting diodes), for example. However, according to further embodiments, the light-emitting semiconductor components can also be embodied as lasers. For example, each of the light-emitting semiconductor components has a first semiconductor layer 110 of a first conductivity type, for example, p-type, a second semiconductor layer 111 of a second conductivity type, for example, n-type, and an active zone 112.

For example, an active zone can be arranged between the first and second semiconductor layers. The active zone can, for example, have a pn junction, a double heterostructure, a single quantum well (SQW) structure, or a multi-quantum well (MQW) structure for radiation generation. The term "quantum well structure" has no significance with regard to the dimensionality of the quantization. It therefore includes, among other things, quantum wells, quantum wires, and quantum dots as well as any combination of these layers.

For example, the composition of the semiconductor layers can be In _x Ga _1-x N with 0≤x≤1. However, other compositions are also possible according to further embodiments. Furthermore, the structure of the individual light-emitting semiconductor components can also differ from the structure shown. Furthermore, the light-emitting semiconductor components can also be implemented as OLEDs, organic light-emitting diodes. The light-emitting semiconductor components 100 can each have an identical structure and can each be suitable for emitting a uniform wavelength(s).

The converter element 120 is a uniform converter element. This means that a composition of the associated phosphor or a structure, for example a layer thickness, is constant across the arrangement 15. However, process-related deviations, for example in the composition or the layer thickness, are also encompassed by the term "uniform converter element." For example, the converter element can be suitable for converting electromagnetic radiation 18 in a blue wavelength range, which has been emitted by the light-emitting semiconductor components 100, into yellow light. White light results from the superposition of yellow and blue light. For example, a composition of the phosphor can be Y ₃ (Al _1-x Ga _x ) ₅ O ₁₂ :Ce by a general molecular formula. For example, a wavelength range of the emitted electromagnetic radiation can be in a range from 400 to 500 nm, for example 420 to 460 nm.

For example, the arrangement 15 of light-emitting semiconductor components 100 can be arranged above a common carrier 102. Furthermore, the lighting device comprises a control circuit 124. As shown, the control circuit 124 can, for example, be configured to control and supply power to individual light-emitting semiconductor components 100 via associated contact elements 114, 115. For example, the control circuit 124 can comprise a so-called "companion ASIC," an application-specific integrated circuit, which is configured to control each individual pixel or light-emitting semiconductor component 100.

The lighting device further comprises a storage device 125, which is configured to store measured values indicating a color locus shift as a function of current supply. This is explained with reference to the 2A to 2C will be explained in more detail.

The control circuit 124 is configured to determine an operating current as a function of the current supply depending on the stored color locus shift. The control circuit 124 is further configured to supply the corresponding operating current to each of the light-emitting semiconductor components.

For example, the control circuit 124 is configured to modulate the operating current using pulse width modulation (PWM). This makes it possible, for example, to individually adjust the pulse width or the amplitude of the pulses for each light-emitting semiconductor component 100. For example, the control circuit 124 can be connected to a voltage supply device 126.

According to further embodiments, the control circuit 124 can also be configured to impress a continuous current into each light-emitting semiconductor component 100. In this case, the impressed current intensity can be determined as a function of the color locus shift.

In general, aging effects such as shifts in the color coordinates occur during operation of LEDs. These can be caused, for example, by high operating temperatures and/or high current. In components with many pixels, which have, for example, approximately more than 1,000 light-emitting semiconductor components, for example more than 10,000 light-emitting semiconductor components, the color coordinates of each light-emitting semiconductor component can change individually. This can be due, for example, to different proximity to the power supply device, different frequency of control and the resulting individual current and temperature load. This can result in undesirable color inhomogeneities in the luminous surface, so-called burn-in effects. In particular, individual semiconductor components can each have a different color coordinate. As a result, for example, some of the pixels can have a more yellowish color impression, others a more blueish one.

Furthermore, a lighting device can have a different color location distribution regardless of the occurrence of aging effects due to manufacturing tolerances of the converters.

Because the control circuit 124 is configured to determine the operating current as a function of the current supply depending on the stored color location shift, it is possible to readjust the color location of each pixel, thus achieving improved color homogeneity overall. In particular, deviations in the color location, which may arise, for example, due to different emission wavelengths of the emitted mixed light of the individual semiconductor components, different converter thicknesses, or different load cases during operation and package degradations, can be reduced.

According to further embodiments, the lighting device may additionally comprise a temperature measuring device 127. The temperature measuring device 127 may be configured to determine an operating temperature for each of the light-emitting semiconductor components. As shown in 2A As shown, for example, the temperature measuring device can have two or more sensors. From the measured temperatures, the temperature distribution within the lighting device can be determined pixel-by-pixel using a suitable algorithm. According to further embodiments, a temperature sensor can also be assigned to each light-emitting semiconductor component 100. Furthermore, the control circuit 124 can be adapted to additionally determine the operating current as a function of the operating temperature of the associated light-emitting semiconductor component 100. In this way, a temperature-induced color locus shift can be compensated.

2A As an example, this figure shows the shift of a peak of a wavelength emitted by an LED, for example, a blue (InGaN) LED. As can be seen, the emission wavelength shifts toward a lower wavelength at higher currents.

2B shows, as an example, an absorption characteristic of a phosphor as a function of wavelength. As shown, the converter phosphor has a spectral absorption characteristic that strongly depends on the primary emission wavelength emitted by the light-emitting semiconductor components. As a result, the conversion efficiency and thus the color coordinate of the LED also change with the emitted wavelength. For example, it was found that a change in the emitted wavelength from 445 nm to 440 nm leads to a color coordinate shift along the conversion line toward the blue emission range, since the phosphor used in the converter 120 absorbs less strongly in this range.

2C shows various examples of a shift in the color coordinate (cy) as a function of current. The various diagrams show the shift for different primary emission wavelengths. Within each diagram, the shift is given for different phosphor compositions. For example, the phosphor can have the general composition Y ₃ (Al _1-x Ga _x ) ₅ O ₁₂ :Ce, with the Ga content x varying among the individual curves.

With the described control circuit, the respective current intensity or the amplitude of the pulses and/or the pulse width can thus be individually adjusted depending on the position of the associated light-emitting semiconductor component. Furthermore, it is possible to change the current intensity or the amplitude and/or the pulse width over time over the course of the operating time. According to embodiments, the control circuit 124 can be configured to readjust the current intensity or the amplitude and/or the pulse width after predetermined operating times, for example, every 100 hours of operation. For example, this can counteract temporal degradation of the light-emitting semiconductor components. In particular, the control circuit can be configured to supply different current intensities or signals with different amplitudes and/or different pulse widths to different light-emitting semiconductor components.

3 shows a schematic top view of the lighting device 10 according to embodiments. As can be seen, the individual light-emitting semiconductor components 100 can be arranged in rows and columns. A uniform converter element 120 is arranged above the arrangement 15 of light-emitting semiconductor components. The control circuit 124 is configured as described above. The control circuit 124 contains, for example, a memory 125. Furthermore, the control circuit 124 can be connected to a voltage supply 125.

According to embodiments, a lighting device 10 according to further embodiments may have only a single light-emitting semiconductor component 100 with converter element 120 and a drive circuit 124.

4 summarizes a method for operating the lighting device 10. The method comprises measuring (S100) an initial color location for each light-emitting semiconductor component, and setting (S120) an operating current for each light-emitting semiconductor component based on measured values that indicate a color location shift as a function of current supply. The method further comprises supplying (S130) the operating current to each of the light-emitting semiconductor components.

As described above, the initial color location may differ for each of the light-emitting semiconductor components due to process-related variations. For example, the initial color location may be determined as standard during the manufacturing process. The color location and the measured values indicating a color location shift as a function of the current supply, for example, current intensity and duration of the current supply, may be stored in the memory 125, for example, within the control device 124.

For example, the measured values indicating the color shift as a function of current can also be measured (see S110). This allows the determination of the color shift achieved at which current intensity for the lighting device with light-emitting semiconductor components and converter element.

For example, by adjusting the current supply (e.g., amplitude and pulse width), the color coordinate for each light-emitting semiconductor component 100 can be adjusted. According to further embodiments, a correlation of the color coordinate shift with the integrated load, for example, the temperature and/or the current, experienced by a light-emitting semiconductor component can be established for a sample lighting device. This correlation can be determined once in aging tests and also stored in the memory device 125. Based on the load, a predictive model can then determine the expected color coordinate. The current supply can be adjusted accordingly. The method can thus further comprise adjusting (S140) the current intensity after a predetermined operating period.

As described, both pulse-width modulated and uniform current supply can be used to locally adjust the color coordinates in pixelated components, i.e., lighting devices comprising a plurality of optoelectronic semiconductor components. As a result, a homogeneously luminous surface can be generated by the optoelectronic semiconductor component.

5 shows an optoelectronic component 20 having the above-described lighting device 10. For example, the optoelectronic component can be a vehicle headlight, used for illuminating rooms, or for vehicle interior lighting.

Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that the specific embodiments shown and described may be replaced with a variety of alternative and/or equivalent designs without departing from the scope of the invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, the invention is limited only by the claims and their equivalents.

LIST OF REFERENCE SYMBOLS

10

Lighting device

15

Arrangement of light-emitting semiconductor components

18

electromagnetic radiation

20

optoelectronic component

100

light-emitting semiconductor component

102

carrier

110

first semiconductor layer

111

second semiconductor layer

112

active zone

114

first contact element

115

second contact element

120

Converter element

124

Control circuit

125

storage device

126

Power supply device

127

Temperature measuring device

Claims (16)

A method for operating the lighting device comprising an arrangement (15) of a plurality of light-emitting semiconductor components (100); a uniform converter element (120) above the arrangement (15) of the plurality of light-emitting semiconductor components (100), wherein the converter element (120) is configured to convert a first wavelength of electromagnetic radiation (18) emitted by the light-emitting semiconductor components (100) into a second wavelength; and a drive circuit (124) configured to supply each of the light-emitting semiconductor components (100) with an associated operating current, comprising: measuring (S100) an initial color locus for each light-emitting semiconductor component; Setting (S120) an operating current for each light-emitting semiconductor device based on measured values indicating a color locus shift as a function of current supply; and supplying (S130) the operating current to each of the light-emitting semiconductor devices. Procedure according to Claim 1 , wherein the operating current is supplied in pulsed form, further comprising adjusting (S140) the pulse width and/or the amplitude after a predetermined operating time. Procedure according to Claim 1 or 2 , further comprising detecting an operating parameter after a predetermined operating time, wherein the pulse width and/or the amplitude is adjusted depending on the detected operating parameter. Procedure according to Claim 3 , wherein the operating parameter comprises an operating temperature of the light-emitting semiconductor component. Method according to one of the preceding claims, wherein a plurality of the light-emitting semiconductor components are operated in continuous wave mode. A lighting device (10), comprising: an array (15) of a plurality of light-emitting semiconductor components (100); a uniform converter element (120) above the array (15) of the plurality of light-emitting semiconductor components (100), wherein the converter element (120) is configured to convert a first wavelength of electromagnetic radiation (18) emitted by the light-emitting semiconductor components (100) into a second wavelength; a memory device configured to store measured values indicating a color locus shift as a function of current supply; and a drive circuit (124) configured to determine an operating current for each of the light-emitting semiconductor components (100) as a function of the stored color locus shift as a function of current supply and to supply the associated operating current to each of the light-emitting semiconductor components (100). Lighting device (10) according to Claim 6 , wherein the control circuit (124) is arranged to modulate the operating current by means of pulse width modulation. Lighting device (10) according to Claim 7 , wherein the control circuit (124) is configured to adjust an amplitude of the pulses individually according to a position of the associated light-emitting semiconductor component (100). Lighting device (10) according to one of the Claims 6 until 8 , wherein the control circuit (124) is configured to adjust a width of the pulses individually according to a position of the associated light-emitting semiconductor component (100). Lighting device (10) according to one of the Claims 6 until 9 , wherein the control circuit (124) is arranged to change the amplitude and/or the pulse width in a time-dependent manner. Lighting device (10) according to one of the Claims 6 until 10 , wherein the control circuit (124) is configured to supply signals having a different amplitude and/or different pulse width to different light-emitting semiconductor components (100). Lighting device (10) according to Claim 6 , wherein a plurality of the light-emitting semiconductor components (100) are operated in continuous wave mode. Lighting device (10) according to one of the Claims 6 until 12 , further comprising a temperature measuring device which is configured to determine an operating temperature for each of the light-emitting semiconductor components (100), wherein the drive circuit is suitable for additionally determining the operating current as a function of the operating temperature of the associated light-emitting semiconductor component (100). Optoelectronic component (20) which comprises the lighting device (10) according to one of the Claims 6 until 13 has. Optoelectronic component (20) according to Claim 14 , which is designed as a vehicle headlight or lighting device. Lighting device (10), comprising: a light-emitting semiconductor component (100); a converter element (120) above the light-emitting semiconductor component, wherein the converter element is configured to convert a first wavelength of electromagnetic radiation (18) emitted by the light-emitting semiconductor component (100) into a second wavelength; a memory device configured to store measured values indicating a color locus shift as a function of a current supply; and a control circuit (124) configured to determine an operating current as a function of the stored color locus shift as a function of a current supply and to apply the operating current to the light emitting semiconductor component (100).