Lighting Device

Abstract

The lighting device includes a plurality of modules, each having an array of LED chip connection pads. Interconnections between the pads provide groups of connection pads, each group including a parallel set of connection pads, the groups being in series with each other. An optical unit is provided for shaping the light output from the LED chips mounted on the pads. The groups are defined to (combinedly) minimize the overall spacing of the pads within a group to provide the best color mixing of the LEDs mounted on the connection pads.

Description

[Technical field]

[0001] The present invention relates to a lighting device, in particular to a lighting device comprising a plurality of modules, each having a respective light shaping unit. [Background technology]

[0002] Different applications require different lumen outputs even for lighting devices of the same dimensions. For example, different luminaire designs may have the same printed circuit board size and shape but require different numbers of LEDs mounted on that board area to produce different light outputs and / or operate at different output powers.

[0003] Despite the same board size and shape, different PCB designs are typically used to implement different numbers of LEDs in different product designs. Summary of the Invention [Problem to be solved by the invention]

[0004] A known alternative approach, which allows the same PCB design to be used, is to make use of so-called jumpers: these are resistors (acting as short circuits) that are installed in place of the LEDs to maintain circuit functionality, but reduce the number of LEDs compared to the maximum LED capacity of the PCB.

[0005] The need to manufacture multiple different PCB designs or otherwise use extra resistors (jumpers) increases the cost of manufacturing multiple systems.

[0006] Also, if a single PCB design can accommodate different numbers of LEDs, for example by using jumpers, there is the problem that the quality of the light output, e.g. color uniformity over an area, will also differ between implementations with different numbers of LEDs if different color LEDs are used. This is especially true when the PCB layout is constrained to a set of modules, each with its own beam shaping optical unit.

[0007] WO 2012 / 005771A2 discloses an LED array lighting component that includes a circuit board on which an array of LED chips is mounted and electrically interconnected.

[0008] US 2018 / 0259166A1 discloses a light source module including a circuit board and a plurality of light emitting diodes arranged on the circuit board.

[0009] EP 2397749A2 discloses a light emitting device that includes a series circuit, a substrate, and an encapsulant. [Means for solving the problem]

[0010] The invention is defined by the claims.

[0011] According to an example according to one aspect of the present invention, A substrate; At least two modules disposed on a substrate; wherein each module comprises: an array of LED chip connection pads; interconnects between chip connection pads for implementing a plurality of groups of connection pads, each group including a plurality of connection pads in parallel, the groups being in series with each other; LED chips mounted on connection pads, at least two LED chips of different color points being mounted on respective connection pads of each group; an optical unit for shaping the light output from the LED chip; Including, Each group of connection pads has a geometric centre, and a lighting device is provided in which for the given placement positions of the array, the sum of the distances from the connection pads in all groups to their respective geometric centres is minimal.

[0012] Herein, in the context of this disclosure, LED(s) or "light emitting diode(s)" have the same meaning as LED chip(s).

[0013] The lighting device comprises a module in which an array of LED chip connection pads are formed with a given placement, for example for a regular rectangular grid of LED positions.

[0014] First, the invention concerns the scalability of the module. The invention allows the module design to be scaled to different numbers of LEDs by simply not placing unwanted LEDs. Thus, LEDs may be on all LED connection pads or there may be free LED connection pads on which no LEDs are placed. The interconnection avoids the need for jumpers. Notably, even if LEDs of each group are omitted, the electrical circuit still functions, since there are still LEDs in each group (notably at least two LEDs of different color points).

[0015] Secondly, the invention relates to color mixing performance. By placing at least two different color points in each group, color mixing is improved due to the minimum overall spacing between LEDs in a group. The invention also provides electrical balancing, among other things, by having each group have the same or similar combination of LED types.

[0016] The different color points may be different color temperatures (eg, warm white and cool white), or different bins of the same color, or even different colors altogether.

[0017] The array of LED chip bond pads may, for example, have a regular rectangular grid of chip bond pads, and thus color mixing is achieved based on grouping of bond pads, and therefore LEDs, rather than based on LED chip position, which remains a regular grid.

[0018] The rectangular grid is, for example, a 3x4 grid (3 rows and 4 columns).

[0019] In this case, the first group is a 2x2 subarray in one corner of the grid, the third group is a 2x2 subarray in an adjacent corner of the grid, and the second group is the remaining 4x1 subarray. This provides a desired minimum sum of distances for a 4x3 grid divided into three subarrays of four chip connection pads. The groups are, for example, in series from first to third.

[0020] In one example, The first, 2x2 sub-array has two warm white LEDs and one cyan LED. The second, 4x1 sub-array has one warm white LED and two cool white LEDs. The third, 2x2 sub-array has two warm white LEDs, one cool white LED and one cyan LED.

[0021] The two cyan LEDs, for example, are in the center part of the module, which prevents the cyan color from being seen as separate spots.

[0022] The LEDs in all groups may have the same set of LED color points, in which case each group has good color mixing and the same overall mixed color point for each group, with no color variation across the area of ​​the module.

[0023] Alternatively, the LED chips provided in different groups may include at least two different sets of LED color points, which allows for greater flexibility in defining the overall output color point of the entire module.

[0024] There may be an LED on each LED connection pad, thus all LED space is occupied for maximum lumen output.

[0025] Alternatively, there may be one vacant connection pad within each group of LED connection pads.Alternatively, there may be two vacant connection pads within each group of LED connection pads.

[0026] Alternatively, different groups of LED connection pads may have different numbers of free connection pads. Thus, the series-parallel circuit arrangement provides the flexibility to configure the module in a variety of ways.

[0027] At least two different color points of LEDs are provided for each group of LED connection pads. Warm White, Cool White, and Cyan, It may include two of the following:

[0028] The optical unit may include a reflector around the outside of the array of LEDs. In one example, the reflector has a truncated square-based pyramid with a square entrance window at its base and a square light exit window at its apex. Alternatively, the optical unit may include a lens.

[0029] The lighting device may include a linear row of modules, for example four modules.

[0030] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. [Brief description of the drawings]

[0031] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] 1 shows a known layout of an LED circuit that can be configured as 36 LEDs or 48 LEDs. [Diagram 2] 1 shows an example of an LED circuit using a first design embodiment according to the present invention. [Diagram 3] 1 shows one possible way to interconnect the module's 12 LED connection pads. [Figure 4] 1 illustrates an improved manner for interconnecting connection pads. [Diagram 5] A strip of four modules is shown. [Figure 6] 1 shows a strip of modules in an exploded view. [Figure 7] One reflector is shown in more detail. [Figure 8] One possible combination of color points is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present invention will now be described with reference to the figures.

[0033] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the devices, systems and methods of the present invention will become better understood from the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used to denote the same or similar parts throughout the drawings.

[0034] The present invention provides a lighting device including a plurality of modules, each having an array of LED chip connection pads. The interconnections between the connection pads provide groups of connection pads, each group including a parallel set of connection pads, the groups being in series with each other. An optical unit is provided for shaping the light output from the LED chips mounted on the pads. The groups are defined to minimize (in combination) the overall spacing of the pads within the group to provide the best color mixing of the LEDs mounted on the connection pads.

[0035] FIG. 1 shows a known layout of an LED circuit that can be configured as 36 LEDs or 48 LEDs.

[0036] The circuit comprises four branches B1 to B4 in parallel, each branch comprising a string of 12 LEDs 10 in series.

[0037] Along each branch, three LEDs have space for the connection of parallel jumpers 12. By placing these parallel jumpers, the LEDs are bypassed. The LEDs may be in place but bypassed (the voltage drop across the jumper is less than the forward LED voltage). Thus, a standard 48 LED PCB can be reconfigured as a 36 LED device by adding three jumpers per branch. Alternatively, the LEDs to be bypassed may be omitted to reduce costs.

[0038] Thus the circuit can be switched between 48 LEDs (12 x 4 branches) and 36 LEDs (9 x 4 branches), or indeed other configurations are possible by bypassing a different number of LEDs.

[0039] FIG. 2 shows an example of an LED circuit using the first design embodiment according to the present invention.

[0040] The circuit includes 12 groups of LEDs G1 to G12, each group including a parallel number of LEDs 10. In this example, each group has 4 LEDs in parallel.

[0041] This makes the circuit scalable: for example, the circuit can be scaled from 48 LEDs (12 groups of 4 LEDs) to 36 LEDs (12 groups of 3 LEDs) without the need for jumpers, by simply leaving out one LED from each group.

[0042] Thus, the circuit can be scaled to different numbers of LEDs without having to populate unwanted LEDs.

[0043] The LEDs are attached to connection pads, which define the series and parallel arrangement as shown in the diagram. By connecting LEDs to all LED connection pads, full LED capacity is reached. However, by leaving free LED connection pads, a reduced LED count is achieved. If one or more (but not all) LEDs are omitted from each group, the electrical circuit will still function.

[0044] The invention relates inter alia to a lighting device comprising a line of modules or a plurality of lines of modules forming a 2D array, the modules together providing a set of LEDs, such as 48 LEDs or 36 LEDs in the above example.

[0045] For example, each module may contain up to 12 LEDs, and there may be four such modules to create a maximum 48 LED capacity.

[0046] The lighting device comprises spaced apart modules distributed over an area (a line or a 2D array). Together the modules provide a desired lumen output and the use of spaced apart modules achieves a desired unified glare rating (UGR), e.g. for office lighting.

[0047] As will be described below, each module has an optical element, such as a concave reflector, and the LEDs of the module are within the reflector cavity, as shown in Figures 5 and 6. Further details regarding this particular type of lighting device can be found in EP 2 792 936.

[0048] Each module has its own series-parallel arrangement, such as that shown in Figure 2, but in this example there are only 12 LEDs per module. The 12 LEDs are arranged in three groups, each with 4 LEDs in parallel, and the three groups are in series with each other. Thus, when all four modules are arranged in series, there are 12 parallel groups of LEDs, with all 12 groups in series with each other, thus forming the overall circuit of Figure 2.

[0049] Each module has an array of LED chip connection pads to which LEDs may or may not be connected. The interconnections between the chip connection pads implement multiple groups (G1-G12) of parallel connection pads. The connection pads are formed as a regular rectangular grid, specifically a 3x4 grid in this example.

[0050] 3 shows one possible way to interconnect the twelve LED connection pads 30. Each of the three rows of connection pads 30 forms one of the groups. The interconnections 32 between the pads provide the connection pads of each group in parallel and the groups in series with each other.

[0051] Another aspect of the present invention is to provide an improved layout of LED connection pads.

[0052] Figure 4 shows the connection pad layout for this 3x4 grid.

[0053] In this case, the first group of connection pads 30 is a 2×2 subarray in one corner of the 3×4 grid. This first group is labeled 1 in FIG. 4 and is in the upper left corner. Interconnects 32 place all of these connection pads in parallel between nodes N1 and N2. The second group of connection pads 30 is labeled 2 in FIG. 4 and is a 1×4 subarray forming the bottom row. Interconnects 32 place all of these connection pads in parallel between nodes N2 and N3. The third group of connection pads 30 is labeled 3 in FIG. 4 and is a 2×2 subarray in the upper right corner. Interconnects 32 place all of these connection pads in parallel between nodes N3 and N4.

[0054] It will be appreciated that this interconnection arrangement does not require crossovers and thus can be formed as a conductor single layer of a PCB.

[0055] Each connection pad is shown as a single square in Figures 3 and 4. In reality, each connection pad includes a pair of contacts for connection to an LED anode and an LED cathode.

[0056] Within each group, there is a geometric center, which is the geometric average of the locations of the centers of the connection pad areas. Each group has a sum of the distances between these centers. For the first group, arrows 40 represent these distances. For a 2x2 subarray, this sum of distances is as small as possible (no group of four connection pads has a lower sum of distances), while for a 1x4 subarray, the sum of distances is larger. However, for a given placement position of the array (i.e., a regular rectangular 3x4 grid in this example), the total sum (of all groups) is minimum.

[0057] This distance minimization is used to provide the best possible color mixing for LEDs of different color points, which may be because the different LEDs are of different bins (so they are designed to output the same color point but have different color points), or because the LEDs have different color temperatures (e.g. warm white vs. cool white, etc.), or because the LEDs have different colors (e.g. white (cool or warm) vs. cyan, etc.).

[0058] To take advantage of color mixing, at least two LEDs of different color points are mounted on the connection pads of each group, thus each group performs color mixing of different color points, rather than assigning each group a separate color point.

[0059] Furthermore, by providing each group with a different LED type rather than devoting each group to a particular LED color point and therefore type, improved electrical balancing is obtained.

[0060] The overall lighting device is formed by several modules, such as the module of figure 4. Each module has an optical unit for shaping the light output from a group of LED chips.

[0061] Figure 5 shows a strip of four modules M1-M4. Each module has an optical unit 50 in the form of a tapered reflector. The reflector has a truncated pyramid shape with a square or rectangular base. Thus, at PCB level there is a square or rectangular light receiving aperture around the module and a larger square or rectangular light exit aperture above the LED surface. The inner walls around the module are reflective. There may also be lenses over individual LEDs or small subgroups of LEDs. For example, two pairs 52 of LED connection pads (and therefore one pair of LEDs when connected) may have a shared lens.

[0062] A strip of modules is shown in an exploded view in Figure 6. Figure 6 shows the PCB 60 on which the LEDs 10 are mounted. The LEDs 60 are shared between the modules.

[0063] In this example, each group of connection pads has one free space and LEDs 10 are placed on the other three connection pads of each group. There may be two free connection pads in each group, or more for larger groups. At least two connected LEDs are left per group to take advantage of the color mixing of the geometric layout.

[0064] In other examples, different groups of LED bond pads may have different numbers of free bond pads (such as the example of FIG. 8 below).

[0065] The basic design may include free connection pads to create, for example, the 36 LED device of Figure 6. The design can then be upgraded to a 48 LED design without creating a new PCB.

[0066] The upgrade can be done with the same reflector design and using the same driver voltage window because the number of series groups is the same and therefore the LED forward voltage combinations are also the same.

[0067] 7 shows one reflector in more detail, showing a pyramidal shaped light entrance window 70 and a light exit window 72. An array of openings 74 are formed in the light entrance window 70. Each opening 74 contains two pairs of connection pads, so that up to two LED chips can be attached to each opening. Optionally, a lens may be formed in the light entrance window, as mentioned above.

[0068] FIG. 8 shows one possible combination of color points for one module (and which may be repeated in each module).

[0069] The 2x2 subarray of the first group G1 contains two warm white (WW) LEDs and one cyan (CY) LED. One space is left empty (X). The 1x4 subarray of the second group G2 contains two cool white (CW) LEDs and one warm white LED. One space is left empty. The 2x2 subarray of the third group G3 contains two warm white LEDs, one cool white LED and one cyan LED. There is no empty space.

[0070] The two cyan LEDs are aligned in the center of the module, which allows them to have greater contrast to the white LED and therefore reduces the spottiness of the cyan LEDs by being located next to each other. This is a tunable white, cyan enhanced, configuration.

[0071] Variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be implemented in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0072] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0073] It should be noted that when the term "adapted to" is used in the claims or the specification, it is intended to be equivalent to the term "configured for."

[0074] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A substrate; At least two modules provided on the substrate; wherein each module comprises: an array of LED chip connection pads; an interconnect between the LED chip connection pads, the interconnect providing a plurality of groups of LED chip connection pads; and LED chips mounted on the LED chip connection pads, at least two LED chips of different color points being mounted on respective LED chip connection pads of each group; an optical unit for shaping the light output from the LED chip; Including, a lighting device, wherein each group includes a plurality of LED chip connection pads in parallel, the plurality of groups being in series with one another, each group having a geometric center, and for a given placement position of the array, a sum of the distances from the LED chip connection pads in all groups to their respective geometric centers is minimal.

2. 10. The lighting device of claim 1, wherein the array of LED chip connection pads comprises a regular rectangular grid of LED chip connection pads.

3. 3. The lighting device of claim 2, wherein the rectangular grid is a 3x4 grid.

4. 4. The lighting device of claim 3, wherein a first group is a 2x2 subarray in one corner of the grid, a third group is a 2x2 subarray in an adjacent corner of the grid, and a second group is the remaining 4x1 subarray.

5. The first group of 2×2 subarrays includes two warm white LED chips and one cyan LED chip; the second group of 4×1 subarrays includes one warm white LED chip and two cool white LED chips; 5. The lighting device of claim 4, wherein the third group of 2x2 sub-arrays includes two warm white LED chips, one cool white LED chip, and one cyan LED chip.

6. The lighting device of claim 5 , wherein the two cyan LED chips are in a central portion of the module.

7. 10. The lighting device according to claim 1, wherein the LED chips in all groups have the same set of LED color points.

8. 10. The lighting device according to claim 1, wherein the LED chips provided in different groups include at least two different sets of LED color points.

9. There is an LED chip on each LED chip connection pad, or There is one free connection pad in each group of LED chip connection pads, or Within each group of LED chip bond pads, there are two free bond pads, or 10. The lighting device of claim 1, wherein different groups of LED chip connection pads have different numbers of free connection pads.

10. At least two different color points of the LED chip provided on each group of LED chip connection pads are Warm White, Cool White, and Cyan, 10. A lighting device according to claim 7, comprising two of:

11. 10. A lighting device according to any one of the preceding claims, wherein the optical unit (10) comprises a reflector (12) around the outside of the array of LED chips (10).

12. 12. The lighting device of claim 11, wherein the reflector has a square or rectangular based truncated pyramidal shape.

13. The lighting device according to claim 11 , wherein the optical unit comprises a lens.

14. 10. A lighting device according to any one of the preceding claims, wherein the lighting device comprises a linear array of said modules.

15. 15. The lighting device of claim 14, wherein the lighting device comprises four modules.

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