EP2965358B1 - Led module and lighting assembly having a corresponding module - Google Patents

Description

The present invention relates to an LED module according to the preamble of claim 1, which consists of an arrangement of electronically interconnected LEDs and a support for the LEDs, and an arrangement for emitting light with such an LED module.

Basis for the present invention is the currently common interconnection of LEDs on boards to series and parallel circuits. Preferably, a parallel connection of an arbitrary number of LED series circuits is selected here. In particular, carrier boards are considered in the present case, which are flat and on which the LEDs are arranged in a uniform grid. Such an arrangement is currently used to operate LEDs with low power consumption efficiently on common high-voltage converters. Normally, the same number of LEDs is interconnected within such interconnections in all parallel series circuits or strings.

In LED modules, which are provided for illumination purposes and configured in the manner described above, in operation a considerable heat is generated by the LEDs, which should be dissipated efficiently to reduce the thermal load of the LEDs or in a designated temperature range to keep and thus extend their life. For example, therefore metal core boards are used, which are optionally coupled with corresponding heat sinks, through which then the heat can be dissipated.

However, even with the application of these measures for heat dissipation, the thermal load of the carrier and in particular the LEDs arranged thereon vary in size. In a usually provided equidistant equidistant arrangement of the LEDs on a board, the heat is dissipated over the edge regions or end regions of a mainly elongate LED board much more effective than over the central or central region. Due to this imbalance, the LEDs from the central area must be cooled better or the cooling measures must be designed more effective, which entails a higher cost.

In the JP 2012043700 Therefore, it is proposed to operate LED strands that run side by side along a board, with different currents, whereby an imbalance in the thermal load should be avoided. Each LED beach is here separately connected to a corresponding output of a driver and is individually supplied with a corresponding power.

Starting from this prior art, the present invention has the object to distribute the thermal load for LEDs on a board evenly without disturbing the uniform arrangement of the LEDs or to make the cooling in the center more efficient.

This object is achieved according to the invention with the objects specified in the independent claims. Particular embodiments or advantageous developments of the invention are specified in the dependent claims.

According to the invention, therefore, an LED module is provided, which has an arrangement of electronically interconnected LEDs in parallel circuits of series circuits of the LEDs and a carrier or a circuit board, which is provided as a support structure for the LEDs, wherein the parallel circuit is chosen such that in that the arrangement of the LEDs has a uniform grid, wherein the number of LEDs of a series circuit from the outer region of the carrier is smaller than the number of LEDs of one Series connection from the inner region and wherein in operation, the LEDs of the series circuit from an outer region of the carrier each subject to a stronger current load than the LEDs of the series circuit from an inner region ,.

The design of the LED interconnection according to the invention, which compensates for the imbalance in the thermal load present in LED modules of the prior art, can be realized in different ways.

The asymmetrical interconnection is characterized in that the number of LEDs in a strand located in the edge region of the carrier or the printed circuit board is reduced compared to the number of LEDs in one strand from the central region. This means that more series circuits are found in the edge area of the board than in the center or in the central area of the board, although the arrangement of the LEDs as a whole is uniform or homogeneous. The difference in the number of LEDs of the individual strands has the consequence that The LEDs in the center or in the middle area are now subject to a lower current load and thus produce less heat. This takes into account the fact that the heat in the middle or central region of the module can be dissipated less effectively to the environment or cooling elements coupled to the module, so that ultimately seen a total of significantly more uniform thermal load over surface. Furthermore, in this embodiment, all the LEDs on the board are substantially identical.

Furthermore, a further useful effect can lie in a targeted amplification of luminous flux at the edge region of the LED modules. This can lead to a higher homogeneity of the luminances on a light exit surface, in particular in the case of a planar arrangement of a multiplicity of LED modules according to the invention combined with diffuse optical systems.

Fig.1

eine Skizze eines erfindungsgemäßen LED-Moduls gemäß einem ersten Ausführungsbeispiel;

Fig.2

eine perspektivische Skizze des LED-Moduls von Fig. 1 gekoppelt an einen Kühlkörper;

Fig.3

eine Querschnittskizze einer Anordnung zur Lichtabgabe bestehend aus dem LED-Modul und einer optischen Diffusor-Platte und

Fig.4

eine Skizze des LED-Moduls gemäß einer nicht beanspruchten Variante.

The invention will be explained in more detail below with reference to the drawings. Show it:

Fig.1

a sketch of an LED module according to the invention according to a first embodiment;

Fig.2

a perspective sketch of the LED module of Fig. 1 coupled to a heat sink;

Figure 3

a cross-sectional diagram of a light emitting arrangement consisting of the LED module and a diffuser optical plate and

Figure 4

a sketch of the LED module according to a not claimed variant.

In Fig.1 a sketch of an LED module 1 according to the invention is shown according to the first embodiment, consisting of an elongate planar support or a circuit board 2 and arranged thereon in a uniform grid LEDs 3, which are connected via electrically conductive connections 4 to a parallel circuit of eleven series circuits 6. In this case, the uniform grid of five rows 5, each with nine LEDs 3 is formed. Furthermore, all the LEDs 3 are preferably substantially identical in at least their forward voltage, more preferably identical in all their properties, with respect to the forward voltage being understood to mean that the deviations from each other should be as low as possible below 0.1V.

According to the invention, the interconnection of the LEDs 3 is carried out in such a way that the number of LEDs 3 per series circuit 6 in the central or middle row on the carrier 2 is greatest and that this number is smaller, the farther an observed row 5 from the center or center axis is removed. This is particularly evident in this embodiment in that - counted from above - the first row 5 three series circuits 6, each with three LEDs 3, the second row 5 two series circuits 6 each with five or four LEDs 3 and the third row, the at the same time is the most central, a series circuit 6 with nine LEDs 3 has. An immediately resulting consequence therefore consists in that, in the case of an interconnection according to this first exemplary embodiment, basically more series circuits 6 or LED strands 6 are required than ultimately LED rows 5 are arranged on the carrier 2.

To operate the LED module 1, a voltage provided by an operating device (not shown) is applied between the common end points 7 and 8 of all the electrically conductive connections 4. Since all series circuits 6 are supplied with the same voltage during operation, the LEDs 3 are in the series circuits 6 in the edge region of the carrier 2 due to their smaller number per series circuit 6 individually under increased voltage load and thus increased power load. Thus, the focal points of the current load of all LEDs 3 are outsourced to the outer regions of the carrier 2. This has the desired effect that now also the focus of heat generation outsourced to the outer regions of the carrier 2 and so the central regions of the carrier 2 are thermally relieved.

It should be clarified at this point that Fig. 1 serves primarily to the basic representation of the inventive concept, namely to use LED strands, each with different numbers of LEDs. In reality, the numbers of LEDs will differ less than this Fig. 1 is shown. For example, a concrete embodiment would be conceivable in which three LED strands are provided, wherein the middle Stang consists of 21 LEDs and the two outer strands each have 18 LEDs.

Incidentally, it would also be conceivable for an LED string to extend over several rows of the LED board in order to achieve a uniform grid arrangement of LEDs. In the aforementioned example with three LED strings, e.g. the last LEDs of the middle strand (with 21 LEDs) are arranged in the outer rows, so that a uniform LED grid with 3 x 19 LEDs results. Despite everything, heat is primarily generated in the side areas in order to achieve the desired goal of uniform thermal stress.

In Fig.2 is shown as an arrangement 11 for cooling such an LED module 1 according to the invention, as shown in FIG Fig. 1 is shown is possible. The LED module 1 is fastened, for example, on its underside on a heat sink 12 or coupled thereto, wherein the means for fastening in Fig. 2 are not visible. It is assumed in the present case that the LED module 1 is thermally evenly utilized during operation even without cooling measures due to the inventive design, with the result that the heat sink 12 no further or more specific cooling mechanisms below the center of the LED module. 1 in the arrangement 11 as required at the edge of the heat sink 12. That is, the equalization of the thermal load according to the invention is achieved solely by the design of the LED module 1, so that the use of the heat sink 12, the thermal load can be further reduced overall without the heat sink would have to be formed in any particular way.

In Fig. 3 is a cross-sectional diagram of an arrangement 15 for light emission, consisting of inventive LED module 1 in operation and an optical diffuser plate 18 shown. The LED module 1 and the diffuser plate 18 are arranged substantially parallel to each other at a certain distance. In the drawing, it is also shown that the LEDs 3 in the edge region of the carrier 2 emit more light than the LEDs 3 in the central region due to the higher current load, with the result that the radiation density 16 at the edge is greater than the radiation density 17 in the center , The diffuser plate can now be designed to homogenize or evenify the light of the LED module 1 in the emission direction, which is characterized by the uniform radiation density 19.

Alternatively, it may even be advantageous for the LEDs 3 to emit more light in an edge region of the carrier 2 than the LEDs 3 in the central region. Usually For example, in illumination arrangements, a plurality of LED modules 1 are arranged next to one another on a preferably planar surface in combination with an optical diffuser plate 18, preferably according to FIG Fig. 3 , Usually, the distance of the LED modules 1 with each other is greater than the distance between the LED rows with each other on a module, which would mean that - provided - same light emission of all LEDs 3, the areas between the LED modules 1 appeared less bright This effect is now automatically compensated by means of the LED modules 1 according to the invention in that the LEDs 3 in the edge regions of the respective LED modules 1 shine brighter due to the higher current load, resulting in a total of significantly more homogeneous appearance of the brightness distribution leads. The optical diffuser plate 18 then additionally provides for a better homogenization.

In Fig. 4 is a sketch of a non-inventive LED module 22 according to a second embodiment, analogous to the LED module 1 according to variant one off Fig. 1 , shown. One of the major differences between the LED module 1 of Fig. 1 and the LED module 22 of Fig. 4 consists in the fact that in the LED module 22 different LEDs are used, which differ in their forward voltage. LEDs with different forward voltages are identified by numbers 24, 26 and 28, with identical numbers representing identical forward voltages. However, each LED row 25, 27 or 29 preferably only has LEDs with identical forward voltages, ie, within a row, the deviations in the forward voltages are already below 0.1V as we mentioned earlier. The differences in the forward voltages between the various LED rows 25, 27, 29, however, should preferably be at least 0.1V.

The second major difference is that in the module of Fig. 4 Each series circuit has the same number of LEDs. As a result, the number of LED rows coincides with the number of series circuits. Furthermore, the electrical connection is no longer asymmetrical, as in the LED module 1 of Fig. 1 the case was.

The complete arrangement of the LEDs and electrical connections on the carrier 23 is conveniently placed axially symmetrically about the LED array 29 so as not to cause asymmetry in the thermal loading of the carrier 23 during operation, even if the total thermal load of the carrier were not uniform. The carrier 23 from Fig. 4 and the carrier 2 off Fig. 1 do not necessarily have to be different.

The forward voltages of the LEDs 24 in the outer row 25 are selected to be smaller than the forward voltages of the LEDs 26 in row 27. Similarly, the forward voltages of the LEDs 26 in row 27 are to be selected to be smaller than the forward voltages of the LEDs The same applies to the remaining unnumbered rows in the lower part of the LED module 22 by Achsenspiegelung all properties on the series 29. Thus, due to the smaller forward voltages towards the outside of the carrier 23 ensures that in the corresponding LEDs a higher current flow is present, so focal points of the current load or thermal load are shifted to the edge regions of the carrier 23.

The use of LEDs of different forward voltage is made possible for example by taking LEDs of the identical type, which nevertheless have different forward voltages during production. Optionally, the use of completely different types of LEDs is possible.

As already mentioned, the two ideas for a better distribution of the thermal load can also be combined with one another. In this case, then different LEDs are used on the module and the lengths of the LED series circuits varies.

Of course, that can be done in FIG. 4 illustrated LED module in an analogous manner as the module according to FIG. 1 be combined with heat sinks or optical elements. In the representations of the Fig. 2 and Fig. 3 Thus, the LED module 1 can be easily replaced by the LED module 22.

In summary, therefore, by using an LED module according to the invention, it is possible to save costs that arise through the use of cooling measures. Further, by optimizing the distribution of the thermal stress, the life of LEDs can be extended and more homogeneous appearances can be obtained with respect to the light output inside and / or outside of lighting devices containing an LED module according to the invention.

Claims (4)

1. An LED module (1), having an arrangement of electronically connected LEDs (3) and a carrier (2) for the LEDs (3), wherein a parallel connection of series circuits (6) of LEDs (3) is present,
   wherein the parallel connection is selected in such a manner that the thermal load on the carrier (2) caused by the operation of the LEDs (3) is distributed substantially uniformly across the carrier (2),
   wherein the arrangement of the LEDs (3) has a uniform grid,
   and wherein during the operation the LEDs (3) of the series circuit (6) from an outer area of the carrier (2) are in each case subjected to a greater current load than the LEDs (3) of the series circuit (6) from an inner area,
   characterized in that
   the number of LEDs (3) of a series circuit (6) from the outer area of the carrier (2) is smaller than the number of LEDs (3) of a series circuit (6) from the inner area.
2. An LED module according to Claim 1,
   characterized in
   that all the LEDs (3) on the carrier (2) are substantially identical.
3. An arrangement for the light output (15), consisting of LED module (1, 22) according to any one of the preceding claims and an optical device (18),
   characterized in
   that the optical device (18) is designed to substantially homogenize or to equalize the light (16, 17) outputted by the LED module (1, 22) during operation.
4. An arrangement according to Claim 3,
   characterized in
   that said arrangement has several LED modules (1, 22) arranged side by side.

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