LED module for emitting mixed light, lighting device comprising such an LED module and method for manufacturing an LED module for emitting mixed light

Abstract

LED module (10) for emitting mixed light, preferably white light, comprising: - a module plate (11) with at least one dam (12) that limits at least one light field, wherein a plurality of LED chips (13) are arranged within the light field; - wherein several separately arranged, bead-shaped walls (14) are provided within the light field, forming separated areas (15) in the light field, wherein the LED chips (13) are arranged in the areas of the bead-shaped walls (14) and in the separated areas (15); and - wherein in the separated areas (15) a potting compound containing a phosphor or a phosphor mixture is provided; - wherein the LED chips (13) which are each arranged in a separate area (15) and the LED chips (13) which are each arranged in the areas of the bead-shaped walls (14) are each connected to each other as an LED string; - wherein the mixed light emitted by the LED module (10) is dimmable by means of current dimming, such that the color of the emitted mixed light changes through the process of current dimming, wherein at least one of the LED strings includes a resistor and at least one other of the LED strings does not include a resistor in order to provide the current dimming, wherein fewer LED chips are arranged in the LED string with the resistor than in the LED string without a resistor.

Description

1. Field of the invention

[0001] The present invention relates to an LED module (light-emitting diode module) for emitting mixed light, preferably white light. Furthermore, the present invention relates to a lighting device comprising such an LED module and a method for producing an LED module and a lighting device with at least one such LED module. 2. Background

[0002] LED modules suitable for emitting mixed light, particularly white light, are known from the prior art. These LED modules typically have a light-emitting field formed by a combination of individual light points. The individual light points are designed to emit different light spectra. For example, the light points emit blue light, red light, and yellow light generated by a phosphor. The light points are typically formed using a so-called globe-top process, in which dispensing drops are applied directly to the individual LED chips. However, such LED modules have a light field that is too large to be used in luminaires with comparatively small reflector sizes.However, such LED modules have a relatively large light field compared to non-controllable light sources, and the light must also be homogenized in a mixing chamber, which requires additional installation space and results in luminaires requiring a reflector that is insufficiently large to meet aesthetic requirements. Such light fields, if they are to be manufactured cost-effectively and with high efficiency, typically have a diameter of at least 19 mm (assuming a luminous flux of approximately 2000+ lm), although it is fundamentally impossible to reduce the diameter of the light field further using the known globe-top processes.

[0003] Furthermore, LED modules with a light field are known, for example from the document EP 2 738 825 A1, in which different areas are separated from one another by an integrally formed intermediate wall.

[0004] Finally, LED modules from Sharp are known under the product name “Tiger Zenigata LED,” which feature a strip-like arrangement of different areas on a light field.

[0005] US 2014 / 0 098 529 A1 discloses a light-emitting device comprising a substrate and a plurality of light-emitting sections.

[0006] EP 2 738 825 A1 discloses a light-emitting device comprising a base part, a plurality of light-emitting elements and a sealing part that seals the light-emitting elements.

[0007] JP 2013-229 492 A discloses a light-emitting module comprising a plurality of light-emitting elements mounted on a substrate, a first wavelength conversion part, and a second wavelength conversion part.

[0008] JP 2014-49504 A discloses a light-emitting device comprising a substrate, a plurality of LED chips mounted on the substrate, a first sealing part and a second sealing part kneaded with a wavelength conversion material and sealing the LED chips.

[0009] In light of this prior art, the object of the present invention is to provide an LED module and a method for producing an LED module for emitting mixed light, preferably a (mixed) white light, that improves on the known prior art. In particular, it is intended to be possible to provide LED modules that are particularly well suited for use in controllable operating room lights (OR lights) or in dimmable lighting for living spaces.

[0010] These and other objects, which will be mentioned in the following description, are achieved by the subject matter of the independent claims. The dependent claims develop the central idea of ​​the present invention in a particularly advantageous manner. 3. Detailed description of the invention

[0011] An LED module according to the invention for emitting mixed light, preferably white light, comprises at least: a module plate with at least one dam that delimits at least one light field, wherein a plurality of LED chips are arranged within the light field; wherein a plurality of bead-shaped walls arranged separately from one another are provided within the light field, which walls form separated regions in the light field; and wherein a potting compound with a phosphor or a phosphor mixture is provided in each of the separated regions.

[0012] In other words, the present invention proposes dividing a light field of an LED module into different, separate regions by means of separate, bead-shaped walls. A bead-shaped wall section is understood to be a wall section with a cross-sectional shape that essentially corresponds to a circular section, for example an essentially semicircular cross-sectional shape. Such bead-shaped walls can be applied in a simple manner using a so-called dispensing process, so that the separated regions can be provided in a simple manner. Potting compounds with identical phosphors or an identical phosphor mixture can be introduced into the various separate regions, or potting compounds with different phosphors orDifferent phosphor mixtures are introduced into the various separated areas. The LED chips are arranged both in the areas of the light field separated by the bead-shaped walls and in the area of ​​the bead-shaped walls themselves.

[0013] Advantageously, the potting compound is a silicone and / or epoxy-based potting compound which is completely transparent in the spectral ranges important for the function, preferably already in the liquid state, but at least in the crosslinked state.

[0014] The dam (or dams) preferably has a width, seen in plan view, of between 50 µm and 2 mm, particularly preferably between 300 µm and 1.5 mm, and further preferably between 500 µm and 1000 µm. The dam is either formed directly on the module plate, for example by applying and curing a suitable material (using a so-called dispensing process), or the dam is initially manufactured as a separate component which is subsequently connected to the module plate. Furthermore, it is preferred that the dam is formed with a mainly diffusely reflecting white surface or with a reflective metallic surface. Advantageously, no further dams are provided within the dam enclosing the at least one light field. However, a plurality of light fields, each delimited by a dam, can also be provided on the module plate.Analogous to the provision of the dam, the bead-shaped walls can also be formed either directly on the module plate, for example, by applying and curing a suitable material (preferably by a so-called dispensing process), or the bead-shaped walls can be initially manufactured as separate components or as a composite with the dam and then connected to the module plate. If LED chips are also provided in the area of ​​the bead-shaped walls, it is preferable to form the bead-shaped walls directly on the module plate, since in this case they are intended to cover the LED chips arranged underneath.

[0015] The surface of the light field formed by the potting compound and the bead-shaped walls can be smooth or wavy. A wavy surface can result either from the bead-shaped walls extending beyond the potting compound provided in the separated areas or from the potting compound extending beyond the bead-shaped walls.

[0016] Preferably, the light field encompassed by the at least one dam is circular and preferably has a luminous flux density of > 5 lm / mm 2 which results in a light field diameter of approximately 23 mm for a luminous flux package of 2000 lm. However, the applied invention can achieve a luminous flux density of > 25 lm / mm 2 which results in light field diameters of approximately 16 mm to approximately 11 mm for a luminous flux package of 2000 lm.

[0017] It is preferred that LED chips that emit a blue light spectrum are arranged in the at least one light field, wherein it is particularly preferred that only LED chips that emit a blue light spectrum are arranged in the at least one light field and in particular no LED chips that emit a red light spectrum. It may also be preferred to provide LED chips that emit a blue light spectrum only in certain regions of the at least one light field. The present invention generally understands light from the red light spectrum to mean light with a peak wavelength between approximately 580 and 670 nm, light from the blue light spectrum to mean light with a peak wavelength between approximately 390 and 480 nm, light from the green light spectrum to mean light with a peak wavelength between approximately 480 and 560 nm, and light from the yellow light spectrum to mean light with a peak wavelength between 560 and 630 nm.

[0018] Preferably, the potting compound arranged in the separated regions comprises green, yellow, or red phosphor or a mixture thereof. A phosphor is generally a substance that can be excited by light emitted by the LED chips used and subsequently emits a secondary light spectrum. Preferably, inorganic phosphors or a quantum dot are used in the present invention, for example, ZnS, ZnSe, CdS, CdSe, ZnTe, CdTe. Preferably, secondary light from the yellow, green, and / or red spectrum range is emitted by the phosphor when excitation occurs via blue light. When using deep blue light (<420 nm) or UV light, emission of blue light is also required. Other phosphors that can be used in the present invention are, for example: silicates (Ca3Sc2Si3O 12 : Ce3+), ortho-silicates (BOSE), garnets (YAG: Ce 3+ , (YGd)AG: Ce 3+ , LuAG: Ce 3+), Oxides (CaScO2: Eu 2+ ), SiALONs (a-SiALON: Eu 2+ , b-SiALON: Eu 2+ ), nitrides (La3Si6N 11 : Ce 3+ , CaAlSiN3:Ce 3+ ), oxy-nitrides (SrSi2N2O2: Eu 2+ , (Ca,Sr,Ba)Si2N2O2: Eu 2+ ).

[0019] Advantageously, the bead-shaped walls are arranged substantially parallel to one another on the light field, resulting in an alternating sequence of separated regions and bead-shaped walls on the light field. Such a configuration of the light field represents a particularly preferred embodiment of the present invention, as it allows a particularly homogeneous light impression of the LED module to be achieved.

[0020] In a preferred first alternative, LED chips are arranged on the light field both in the areas covered by the respective encapsulants and in the areas covered by the bead-shaped walls. In this case, green, yellow, or red phosphors, or a mixture thereof, are arranged in the bead-shaped walls. The phosphors already described above can also be used here.

[0021] Advantageously, the phosphor in the bead-shaped walls is selected such that these regions emit a (warm white) white light with a color temperature between 2500 K and 4000 K, preferably between 2800 K and 3500 K, and particularly preferably of approximately 3000 K; and wherein the phosphor in the separated regions is selected such that these regions emit a (cold white) white light with a color temperature between 4500 K and 8000 K, preferably between 5000 K and 7500 K, and particularly preferably of approximately 6500 K. It is particularly preferred that the LED chips, each arranged in a separate region, and the LED chips, each arranged in the regions of the bead-shaped walls, are each connected to one another as an LED strand. In this context, it is further preferred that the respective LED strands are interconnected and controllable in groups.In particular, it is preferred that the LED strings arranged in the separated areas are interconnected and controlled as a first group and the LED strings arranged in the areas of the bead-shaped walls are interconnected and controlled as a second group, so that the white light emitted by the LED module can be freely adjusted between the color temperature of the first group and the color temperature of the second group.

[0022] In the embodiment of the preferred first alternative, the LED module can be used particularly advantageously as a surgical light, since the surgeon can freely vary as needed between a cold white light, which is particularly suitable for illuminating bones or the like, and a warm white light, which is particularly suitable for illuminating meat tissue.

[0023] Particularly in the design as a surgical light, the specific color rendering indices Ra8 and Ri09 of the LED module are preferably greater than 90 at 4300 K. Due to the comparatively high color rendering quality in these specific ranges, such an LED module is particularly well suited as a surgical light, as the colors of bone and meat tissue are reproduced particularly well.

[0024] The LED module also includes LED chips in the bead-shaped walls and in the separated areas, although fewer LED chips are required overall. The mixed light emitted by the LED module is dimmable by current dimming, so that the color of the emitted mixed light changes as a result of the current dimming process. At least one LED string includes a resistor, and at least one LED string does not include a resistor, whereby fewer LED chips are arranged in the LED string with the resistor than in the LED string without a resistor, in order to provide current dimming. In this alternative, the bead-shaped walls are transparent.

[0025] In this alternative, the phosphor or phosphor mixtures for the separated areas and the bead-shaped walls are preferably selected such that the LED module can emit a (warm white) white light with a color temperature between 2000 K and 4000 K, preferably between 2200 K and 2700 K and particularly preferably of about 2700 K.

[0026] The LED chips, each arranged in a separate area and in a bead-shaped wall, are connected to one another as LED strings, whereby the different LED strings are preferably interconnected and controllable in several groups, but individual LED strings can also be controlled specifically if required.

[0027] Advantageously, the individual LED strands or interconnected groups are independently dimmable, for example, using current dimming. This makes it possible to dim the light emitted by the LED module. The combination of the warm white color temperature and dimmability makes such an LED module particularly suitable for illuminating living spaces, as it can provide a dimmable and comparatively warm, cozy light comparable to that of an incandescent bulb.

[0028] A method according to the invention for producing an LED module for emitting mixed light, preferably white light, comprises at least the following steps: providing a module plate with at least one dam that delimits a light field, wherein a plurality of LED chips are arranged within the light field; applying a plurality of bead-shaped walls arranged separately from one another in order to form regions in the light field that are separated from one another by the walls, wherein the LED chips are arranged in the regions of the bead-shaped walls and in the separated regions; filling each of the regions with a liquid potting compound, wherein the potting compound comprises a phosphor or a phosphor mixture, wherein the LED chips, each arranged in a separated region, and the LED chips, each arranged in the regions of the bead-shaped walls, are each connected to one another as an LED strand.The mixed light emitted by the LED module is dimmable by means of current dimming, so that the color of the emitted mixed light changes as a result of the current dimming process, wherein to provide the current dimming at least one of the LED strings comprises a resistor and at least one other of the LED strings comprises no resistor, wherein fewer LED chips are arranged in the LED string with the resistor than in the LED string without a resistor.

[0029] Furthermore, the present invention relates to a lighting device, in particular an operating room light or a dimmable light for illuminating living spaces, which comprises at least one LED module as described above. 4. Description of preferred embodiments

[0030] A detailed description of the figures is given below. It shows: Fig. 1 a schematic plan view of a first embodiment of an LED module according to the invention; Fig. 2 a schematic cross-sectional view of the Fig. 1 LED module shown; Fig. 3 a schematic view of a circuit of a second preferred embodiment of an LED module according to the invention; and Fig. 4 a schematic view of the second preferred embodiment of an LED module according to the invention; Fig. 5 shows the current flow through the respective connected LED strings Fig. Figure 6 shows the CIE standard color coordinates of the second preferred embodiment as a function of current dimming.

[0031] The figures show only parts of the features contained in independent claims 1 and 16.

[0032] In the following, a first preferred embodiment of an LED module 10, which is particularly well suited for use as an operating room light, together with a preferred manufacturing method of such an LED module 10 is described with reference to the Fig. 1 and Fig. 2 explained.

[0033] In a first step, a module plate 11 is provided with (at least) one dam 12, which preferably defines a substantially circular light field. A plurality of LED chips 13 are arranged within the light field. For the sake of clarity, a reference symbol is assigned to only one LED chip in the figures. As shown in Fig. 1, it is preferred that the LED chips 13 are arranged in rows and columns in the light field so that a substantially homogeneous distribution of the LED chips 13 on the light field can be achieved.

[0034] The dam 12 preferably has a width, as seen in plan view, of between 50 µm and 2 mm. The dam 12 can either be formed directly on the module plate 11 or initially manufactured as a separate component that is subsequently bonded to the module plate 11. In the preferred embodiment shown, the dam 12 is formed with a predominantly diffusely reflecting white surface.

[0035] The LED chips 13 are preferably blue-emitting LED chips, although, depending on the application, red-emitting, green-emitting, yellow-emitting, UV-emitting LED chips or a mixture thereof can also be used.

[0036] In a further step, several bead-shaped walls 14 are applied in the light field. This can be done, for example, using a so-called dispensing process, wherein the viscosity of the material of the bead-shaped walls 14 is selected such that unwanted spreading of the applied bead-shaped walls 14 is prevented.

[0037] As in Fig. 1, the bead-shaped walls 14 form separated regions 15 on the luminous field, which are delimited by the respective walls 14 and the dam 12. As in Fig. 1, in this embodiment LED chips 13 are arranged both in the separated areas 15 and in the areas of the walls 14.

[0038] In the next step, the regions 15 are filled with a flowable encapsulant such that the LED chips 13 are completely covered by the encapsulant. The encapsulant is preferably silicone and / or epoxy based and is preferably transparent, particularly in the cured state. As shown in Fig. 2, the heights of the bead-shaped walls 14 and the quantity of the respective casting compounds are selected such that a substantially "smooth" surface results. Alternatively, however, the surface formed by the bead-shaped walls 14 and the casting compounds can also be designed to be "wavy," either by the bead-shaped walls 14 extending beyond the casting compounds provided in the separated regions 15 or by the casting compounds extending beyond the bead-shaped walls 14. Alternatively, the bead-shaped walls 14 can also be made smaller, such that the flowable casting compound completely covers the walls 14, but not the dam 12.

[0039] In the Fig. 1 and Fig. In the first preferred embodiment shown in Figure 2, a phosphor is contained both in the potting compound and in the bead-shaped walls 14. It is particularly preferred if the phosphor in the bead-shaped walls 14 is selected such that these regions emit (warm white) white light with a color temperature between 2000 K and 4000 K, preferably between 2500 K and 3500 K, and particularly preferably of approximately 3000 K. Furthermore, it is particularly preferred if the phosphor in the separated regions 15 is selected such that these regions emit (cold white) white light with a color temperature between 8000 K and 5000 K, and particularly preferably of approximately 6000 K.

[0040] Preferably, the same phosphor or phosphor mixture is incorporated into the bead-shaped walls 14 and the encapsulants. Depending on the application, however, it is also possible to introduce different phosphors or phosphor mixtures into the individual bead-shaped walls 14 as well as into the respective encapsulants for the separated regions 15. As already explained above, inorganic phosphors or a quantum dot are preferably used in this case.

[0041] In the preferred embodiment shown, the LED chips 13, each arranged in a separate area 15, and the LED chips 13, each arranged in the areas of the bead-shaped walls 14, are each connected to one another as an LED string (not shown). The LED strings arranged in the separate areas 15 are interconnected and controllable as a first group, and the LED strings arranged in the areas of the bead-shaped walls 14 are interconnected and controllable as a second group. As a result, the white light emitted by the LED module 10 can be freely adjusted between the color temperature of the first group (cool white) and the color temperature of the second group (warm white).In this embodiment, the LED module 10 can be used particularly advantageously in a surgical light, as the surgeon can freely vary between a cool white light and a warm white light as needed, selecting the light color that provides the best viewing conditions for the particular surgical task. Preferably, the LED module 10 can achieve a luminous flux density of > 25 lm / mm. 2 In practice, the emitted light is focused onto a small area (about 10 cm 2 ). One LED module 10 has approximately 300 lm and delivers approximately 5000 lx, which, for example, in a combination of 20 modules, results in an irradiance of 100,000 lx, which is preferred for surgical lights.

[0042] A second preferred embodiment of an LED module which is particularly suitable for use as a dimmable luminaire for living spaces is explained below.

[0043] The production of the second preferred embodiment of an LED module according to the invention is basically carried out in a similar manner to the production of the first embodiment of the LED module 10, so that reference is made to the above explanations in this regard. In contrast to the first embodiment, the second embodiment can also have a smaller total number of LED chips. For example, a total of 5 LED strings can be provided, with preferably 3 LED strings each comprising 7 LED chips connected in series and 2 LED strings each comprising 6 LED chips connected in series (cf. Fig. 3). It is also possible to reduce the current flow compared to the first embodiment and to regulate it using a corresponding series resistor or a constant current source.

[0044] In this embodiment, too, only blue-emitting LED chips are preferably used, although, depending on the application, red-emitting, green-emitting, yellow-emitting, UV-emitting LED chips or a mixture thereof can also be used.

[0045] The Fig. 3 and Fig. 4 shows a schematic view of an electrical circuit of the LED chips of the second preferred embodiment, in which the LED module is particularly preferably used as a dimmable luminaire. As in Fig. As can be clearly seen in Figure 3, this LED module comprises a total of 5 LED strings, with 3 LED strings each comprising 7 LED chips connected in series, and 2 LED strings each comprising 6 LED chips connected in series. Alternatively, one or more constant current sources can be used instead of the resistors R2 and R3, which are arranged as series resistors in the 2 LED strings with only 6 LED chips connected in series. To provide the preferred control described below, it is necessary that fewer LED chips are connected in series in the 2 LED strings with resistors than in the LED strings without resistors. Fig. Figure 5 shows the currents that occur when the Fig. 3 and Fig. 4 shown circuit. The graph marked with reference numeral 30 shows the total current, the graph marked with reference numeral 31 shows the current flowing through the 3 LED strings without resistors, and the graph marked with reference numeral 32 shows the current flowing through the 2 LED strings with resistors. As shown in Fig. As shown in Figure 5, at high currents, the majority of the current flows through the three strings without resistors. At lower currents (current dimming), the proportion of current flowing through the two rows with resistors increases steadily, and at 100 mA (20% dimming), both parts are approximately equal. At 5% dimming (25 mA), the current flows almost exclusively through the two LED strings with resistors. If the combined light at around 500 mA is 2700 K and the individual light of the two LED strings with resistors is 2200 K (or candlelight at 1800 K), the current dimming process changes the light color from incandescent light to a dim light.

[0046] The color temperatures can be freely selected, as in the first embodiment, whereby a color temperature between 2700 K and 2200 K (or 1800 K) is preferred, as this allows the dimming behavior of an incandescent bulb to be simulated. Fig. Figure 6 shows the CIE standard color coordinates of the second preferred embodiment as a function of current dimming.

Claims

[1] LED module (10) for emitting mixed light, preferably white light, comprising: - a module plate (11) with at least one dam (12) which delimits at least one light field, wherein a plurality of LED chips (13) are arranged within the light field; - wherein within the light field, a plurality of bead-shaped walls (14) are provided which are arranged separately from one another and form separated regions (15) in the light field, wherein the LED chips (13) are arranged in the regions of the bead-shaped walls (14) and in the separated regions (15); and - wherein a casting compound with a phosphor or a phosphor mixture is provided in each of the separated regions (15); - wherein the LED chips (13), each arranged in a separate region (15), and the LED chips (13), each arranged in the regions of the bead-shaped walls (14), are each connected to one another as an LED strand; - wherein the mixed light emitted by the LED module (10) is dimmable by means of current dimming, so that the color of the emitted mixed light changes as a result of the current dimming process, wherein to provide the current dimming at least one of the LED strings comprises a resistor and at least one other of the LED strings comprises no resistor, wherein fewer LED chips are arranged in the LED string with the resistor than in the LED string without a resistor. [2] LED module (10) according to claim 1, wherein the dam (12) has a width, as seen in plan view, of between 50 µm and 2 mm, preferably between 300 µm and 1.5 mm and more preferably between 500 µm and 1000 µm, and wherein the dam (12) is preferably formed with a mainly diffusely reflecting white surface or with a mirror-like metallic surface. [3] LED module (10) according to one of claims 1 or 2, wherein the LED chips (13) emit a blue light spectrum, wherein particularly preferably only the LED chips (13) which emit a blue light spectrum are arranged in the at least one light field. [4] LED module (10) according to one of the preceding claims, wherein the light field delimited by the at least one dam (12) is radially symmetrical, particularly preferably circular, and preferably has a luminous flux density of > 5 lm / mm 2and with a luminous flux package of 2000 lm preferably has a diameter of about 23 mm, particularly preferred is a luminous flux density between 10 lm / mm 2 up to 20 lm / mm 2 provided and with a luminous flux package of 2000 lm preferably a light field diameter between about 16 mm to about 11 mm. [5] LED module (10) according to one of the preceding claims, wherein the surface of the light field formed by the potting compound and the bead-shaped walls (14) is smooth or wavy. [6] LED module (10) according to one of the preceding claims, wherein the phosphor or the phosphor mixture comprises green, yellow or red phosphor or a mixture thereof, wherein the phosphor is preferably an inorganic phosphor or a quantum dot. [7] LED module (10) according to one of the preceding claims, wherein the bead-shaped walls (14) are arranged parallel to one another on the light field. [8] LED module (10) according to one of the preceding claims, wherein the bead-shaped walls (14) comprise green, yellow or red phosphor or a mixture thereof, wherein the phosphor is preferably an inorganic phosphor or a quantum dot. [9] LED module (10) according to claim 8, wherein - the phosphor in the separated regions (15) is selected such that these regions emit a white light with a color temperature between 4500 K and 8000 K, preferably between 5000 K and 7500 K and particularly preferably of about 6000 K; and wherein - the phosphor in the bead-shaped walls (14) is selected such that these regions emit a white light with a color temperature between 2500 K and 4000 K, preferably between 3000 K and 3500 K and particularly preferably of about 3000 K. [10] LED module (10) according to one of the preceding claims, wherein the respective LED strands are interconnected and controllable in groups, wherein preferably the LED strands arranged in the separated regions (15) are interconnected and controllable as a first group and the LED strands arranged in the regions of the bead-shaped walls (14) are interconnected and controllable as a second group, so that the white light emitted by the LED module (10) can be adjusted as desired between the color temperature of the first group and the color temperature of the second group. [11] LED module (10) according to one of claims 7 to 10, wherein the specific color rendering indices Ra8 and R9 of the LED module (10) are greater than 90 at 4300 K. [12] LED module (10) according to one of the preceding claims, wherein the bead-shaped walls (14) are transparent. [13] LED module (10) according to claim 8, wherein the phosphor in the separated regions (15) and in the bead-shaped walls (14) is selected such that these regions emit a white light with a color temperature between 2000 K and 4000 K, preferably between 2200 K and 2700 K. [14] LED module (10) according to one of the preceding claims, wherein the respective LED strands are dimmable independently of one another, preferably by means of pulse width modulation. [15] Lighting device, in particular surgical light or dimmable light, comprising at least one LED module (10) according to one of the preceding claims. [16] Method for producing an LED module (10) for emitting mixed light, preferably white light, comprising at least the following steps: - Providing a module plate (11; 110) with at least one dam (12) which delimits a light field, wherein a plurality of LED chips (13) are arranged within the light field; - applying a plurality of bead-shaped walls (14) arranged separately from one another in order to form regions (15) in the light field which are separated from one another by the walls (14), the LED chips (13) being arranged in the regions of the bead-shaped walls (14) and in the separated regions (15); - filling the separated regions (15) with a liquid potting compound, wherein the potting compound comprises a phosphor or a phosphor mixture; wherein the LED chips (13) each arranged in a separated region (15) and the LED chips (13) each arranged in the regions of the bead-shaped walls (14) are each connected to one another as an LED strand; - wherein the mixed light emitted by the LED module (10) is dimmable by means of current dimming, so that the color of the emitted mixed light changes as a result of the current dimming process, wherein to provide the current dimming at least one of the LED strings comprises a resistor and at least one other of the LED strings comprises no resistor, wherein fewer LED chips are arranged in the LED string with the resistor than in the LED string without a resistor.

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