EP4736238A1 - Lighting arrangement - Google Patents

Abstract

A lighting arrangement comprises a respective plurality of first and second light emitting diodes M-LEDs, N-LEDs, arranged on a carrier. The M-LEDs comprise a die having a first surface area SA1 with a largest spatial extent SE1 that is at most (100) micrometers. The N-LEDs comprise a die having a second surface area SA2 with a largest spatial extent SE2 that is at most (300) micrometers. The M-LEDs emit first light having a first emission peak in green light. The N-LEDs are configured to emit second light having a second emission peak in blue light and configured to emit third light having a third emission peak in red light. A ratio defined by SA2/SA1 is equal to or larger than (10) and the arrangement light is white light having a correlated color temperature in a range 2000K to 6500K and a color rendering index of at least (80).

Description

LIGHTING ARRANGEMENT

FIELD OF THE INVENTION

The present invention generally relates to lighting arrangements configured to provide white light. More specifically, the present invention is related to a lighting arrangement comprising a plurality of light emitting diodes (LEDs).

BACKGROUND OF THE INVENTION

A trend in the development of LED lighting is the development of lighting arrangements capable of providing white light having any desired color temperature. For this purpose, the lighting arrangements are configured with a combination of a plurality of red (R), green (G) and blue (B) LED’s. While it is possible to configure a lighting arrangement with an appropriate combination of R, G and B LEDs in order to obtain such white light, a remaining issue is that of providing a pleasant viewing experience in terms of minimizing spottiness. Spottiness is the visibility of individual LEDs e.g. through a (diffusive) light exit window. A highly scattering/diffusive light exit window may be used, but such configuration will reduce the efficiency significantly e.g. due to multiple reflections and absorption losses.

SUMMARY OF THE INVENTION

It is of interest to provide a lighting arrangement that overcomes drawbacks of the prior art as discussed above.

This and other objects are achieved in a first aspect by providing a lighting arrangement having the features of the appended independent claim. Preferred embodiments are defined in the appended dependent claims.

Hence, according to the present invention, there is provided a lighting arrangement configured to provide arrangement light. The lighting arrangement comprises a carrier. A plurality of first light emitting diodes (M-LEDs) are arranged on said carrier. Each of the M-LEDs comprises a die having a first surface area (SAI), the first surface area having a largest spatial extent (SEI) that is less than or equal to 100 micrometers. The lighting arrangement further comprises a plurality of second light emitting diodes (N-LEDs) arranged on said carrier. Each of the N-LEDs comprises a die having a second surface area (SA2), the second surface area having a largest spatial extent (SE2) that is greater than or equal to 300 micrometers.

Note that where reference is made to surface area, this relates to the epitaxial or epitaxy (in short ‘epi’) surface area of the die which may only be on the top surface of the die.

The M-LEDs are configured to emit first light (LG1) having a first emission peak wavelength (XI) in a wavelength range of green (G) light. The wavelength range of green (G) light may be defined as light in a wavelength range from 500 nm to 580 nm.

The N-LEDs are configured to emit second light (LG2) having a second emission peak wavelength, (X2) in a wavelength range of blue (B) light, that may be defined as light in a wavelength range from 420 nm to 490 nm, and configured to emit third light (LG3) having a third emission peak wavelength (X3) in a wavelength range of red (R) light, may be defined as light in a wavelength range from 600 nm to 680 nm.

A ratio R1 defined by SA2/SA1 is equal to or larger than 10 and said arrangement light is white light having a correlated color temperature (CCT) in a range from 2000K to 6500K and a color rendering index (CRI) of at least 80 or at least 85.

Such a lighting arrangement shows an improved performance in terms of reduced spottiness and thereby providing an increased viewing experience. The spottiness depends on the size and luminous flux of each LED. Thus, by using small M-LEDs, i.e. MicroLEDs, the spottiness can be reduced. However, because MicroLEDs are relatively more expensive than ‘normal’ sized LEDs e.g. in terms of assembly costs, a combination of green M-LEDs and ‘normal’ sized red and blue LEDs are used. The reason is that the eyesensitivity is highest for green. By including smaller green LEDs in the lighting arrangement, they are less visible for the human-eye and thereby solving issues at least in terms of spottiness. Thus still, ‘normal’ sized red and blue LEDs can be used.

By configuring embodiments of the lighting arrangement such that SEI is less than or equal to 80 micrometers, SE2 is greater than or equal to 500 micrometers and R1 is greater than or equal to 20, it is possible to obtain an even higher improvement in reduced spottiness/ increased viewing experience, reduced costs and/or efficiency for the lighting arrangement.

In embodiments, SEI may be less than or equal to 80 micrometers, preferably <70 micrometers, more preferably <60 micrometers, most preferably <50 micrometers such as for example 40 micrometers. In embodiments, SE2 may be greater than or equal to 400 micrometers, preferably >500 micrometers, more preferably >600 micrometers, most preferably >700 micrometers such as for example 800 micrometers.

In embodiments, R1 may be greater than or equal to 20, preferably >25, more preferably >30, most preferably >35 such as for example 40.

The number of M-LEDs of the plurality of M-LEDs may be X, the number of N-LEDs of the plurality of N-LEDs may be Y and wherein X is greater than or equal to 5 times Y. That is, due to the fact that the size of the M-LEDs are smaller than the size of the N-LEDs, the number of M-LEDs is much greater than the number of N-LEDs in order to enable the lighting arrangement to provide sufficient light in the G wavelength range e.g. to obtain (high quality) white light.

The plurality of M-LEDs may be homogeneously distributed with a first pitch (Pl) within a first region on the carrier and the plurality of N-LEDs may be homogeneously distributed with a second pitch (P2) within a second region on the carrier.

Additionally or alternatively, the second region at least partly overlaps the first region and P2 is greater than or equal to 2 times PL In other words, by configuring the lighting arrangement with homogeneous distributions having different pitch of the M-LEDS and the N-LEDs, the performance of the lighting arrangement may be even further improved. By homogenously distributing the green M-LEDs it is possible to obtain an even higher improvement in reduced spottiness/ increased viewing experience, reduced costs and/or efficiency.

In embodiments, the carrier may have a size (e.g. largest spatial extent) smaller than 10 cm, preferably smaller than 5 cm.

In embodiments, the plurality of M-LEDs may be distributed/arranged within a first region on the carrier and the plurality of N-LEDs may be distributed/arranged within a second region on the carrier, wherein the second region may at least partly overlap the first region.

Each of the M-LEDs may have a first length (LI), a first width (Wl) and a first aspect ratio (ARI) defined by Ll/W 1. Each of the N-LEDs may have a second length (L2), a second width (W2) and a second aspect ratio (AR2) defined by L2/W2, where AR2 is greater than ARI . Due to the size of the M-LEDs and N-LEDs, for the M-LEDs a high aspect ratio is not possible, while this is possible for the N-LEDs Such a configuration is advantageous in that it may simplify electrical connections in terms of a larger distances between anode and cathode pads in the N-LEDs. By using a smaller aspect ratio for the green M-LEDs the visibility (spottiness) of the green LEDs is further improved. The reason is that the (longest) distance between the center of the die and is periphery is reduced.

The M-LEDs may comprise a luminescent material while at least a subset of the N-LEDs are free from any luminescent material. The reason is that green converted LEDs are much more efficient than direct emitting LEDs. For blue LEDs and red LEDs typically direct emitting LEDs are used. However, the N-LEDs may further comprise one or more phosphor converted white LEDs. That is, some of the N-LEDs may comprise a different luminescent material than the luminescent material comprised in the M-LEDs. The obtained effect is improved quality of white light.

The M-LEDs may comprise G LEDs and the N-LEDs may comprise one or more B LEDs emitting the second light having the second emission peak wavelength in the wavelength range of blue light. The lighting arrangement may further comprise one or more R LEDs emitting the third light having the third emission peak wavelength in the wavelength range of red light. For example, each B N-LED and/or each R N-LED may be neighbored by at least 2 G M-LEDs. That is, such a configuration of the lighting arrangement provides an optimal color mixing, e.g. for creating high quality white light.

Each N-LED may comprise 4 sides, wherein each side is neighbored by at least 1 M-LED. That is, such a configuration of the lighting arrangement provides an optimal color mixing, e.g. for creating high quality white light.

The plurality of M-LEDs may be connected with a respective anode having an anode surface area (ASA1) and a respective cathode having a cathode surface area, CSA1. The plurality of N-LEDs may be connected with a respective anode having an anode surface area (ASA2) and a respective cathode having a cathode surface area (CSA2). ASA2 may be greater than or equal to 4 times ASA1 and/or CSA2 may be greater than or equal to 4 times CSA1. In other words, the electrodes/electrical tracks are scaled to a suitable configuration.

The G M-LEDs may be connected via a first circuitry (CH). The one or more B N-LEDs may be connected via a second circuitry (CI2) and the one or more R N-LEDs may be connected via a third circuitry (CI3). A controller may be configured to individually control the emission of the first light emitted by said plurality of M-LEDs via the first circuitry, the emission of the second light emitted by said one or more of B N-LEDs via the second circuitry and the emission of the third light emitted by said one or more R N-LEDs via the third circuitry. For example, the first circuitry may comprise a first number of parallel arrangements (PAI) and the second circuitry may comprise a second number of parallel arrangements (PA2). Then, PAI may be greater than PA2. Alternatively, the first circuitry may comprise a first number of parallel arrangements and the second circuitry is a serial circuitry.

In embodiments, the lighting arrangement may comprises a light exit window e.g. an envelope or a plate. The light exit window may be light diffusive / scattering. The light exit window may be a diffuser having a reflectivity R. R may be in a range from 15% to 45%, especially 15% to 35%. A lower reflectivity is possible because the spottiness of the green LEDs is reduced.

In embodiments, a LED package may comprise the lighting arrangement.

In a second aspect there is provided a lamp or a luminaire comprising the lighting arrangement as summarized above. Such a lamp or luminaire provides corresponding effects and advantages as described above. The lamp may comprise a connector such as a cap to electrically and/or mechanically connect the lamp to a socket of a luminaire. The lamp may also have an antenna which is functionally connected to the controller allowing remote control of the lamp e.g. adjusting the intensity and/or color point/correlated color temperature e.g. using a remote control e.g. a mobile phone. The lamp may also have an envelope enveloping the lighting arrangement. The luminaire may have a mounting means to mount the luminaire to a wall or ceiling. The luminaire may comprise a light exit window such as a translucent plate to exit the arrangement light.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Fig. la schematically illustrates a top view of a lighting arrangement,

Figs, lb and 1c schematically illustrate a cross-sectional view of the lighting arrangement illustrated in figure la,

Fig. Id schematically illustrates a top view of an N-LED and four M-LEDs, Fig. le schematically illustrates anodes and cathodes in an N-LED and in four M-LEDs,

Fig. If schematically illustrates a lighting arrangement connected to a controller via circuitry,

Fig. 1g schematically illustrates two parallel arrangements of LEDs,

Fig. Ih schematically illustrates a parallel and a serial arrangement of LEDs, and

Fig. 2 schematically illustrates a lamp or a luminaire. DETAILED DESCRIPTION

As illustrated in figure la and figure lb, a lighting arrangement 100 configured to provide arrangement light comprises a carrier 151. A plurality of first light emitting diodes, M-LEDs, 101 are arranged on the carrier 151, each of the M-LEDs 101 comprising a die 111 having a first surface area, SAI, wherein the SAI has a largest spatial extent, SEI, that is less than or equal to 100 micrometers. A plurality of second light emitting diodes, N-LEDs 102 are arranged on the carrier 151, each of the N-LEDs 102 comprising a die 112 having a second surface area, SA2, wherein the SA2 has a largest spatial extent, SE2, that is greater than or equal to 300 micrometers.

Note that where reference is made to surface area, this relates to the epitaxial or epitaxy (in short ‘epi’) surface area of the die which may only be on the top surface of the die.

The M-LEDs 101 are configured to emit first light, LG1, having a first emission peak wavelength, I, in a wavelength range of green, G, light. The N-LEDs 102 are configured to emit second light, LG2, having a second emission peak wavelength, X2, in a wavelength range of blue, B, light. The N-LEDs 102 are also configured to emit third light, LG3, having a third emission peak wavelength, X3, in a wavelength range of red, R, light. A ratio R1 defined by SA2/SA1 is equal to or larger than 10 and the arrangement light is white light having a correlated color temperature, CCT, in a range from 2000K to 6500K and a color rendering index, CRI, of at least 80.

For example, the M-LEDs 101 may comprise G LEDs and the N-LEDs 102 may comprise one or more blue, B, LEDs emitting the second light, LG2, having the second emission peak wavelength, X2, in the wavelength range of blue, B, light. The N-LEDs 102 may further comprise one or more red, R, LEDs emitting the third light, LG3, having the third emission peak wavelength, X3, in the wavelength range of red, R, light.

In some embodiments, each B N-LED 102 and/or each R N-LED 102 may be neighbored by at least 2 G M-LEDs 101.

In some embodiments, and as schematically illustrated in figure Id, each N- LED 102 may comprise 4 sides, wherein each side is neighbored by at least 1 M-LED 101.

In some embodiments of the lighting arrangement 100, SEI is less than or equal to 80 micrometers, SE2 is greater than or equal to 500 micrometers and R1 is greater than or equal to 20. Although the lighting arrangement 100 schematically illustrated in figure la comprises a specific number of LEDs, i.e.16 N-LEDs and 64 M-LEDs, the number of M- LEDs of the plurality of M-LEDs (101) may be X and the number of N-LEDs of the plurality of N-LEDs (102) may be Y and wherein X is greater than or equal to 5 times Y.

As illustrated in figure la, the plurality of M-LEDs 101 may be homogeneously distributed with a first pitch, Pl, within a first region 161 on the carrier 151 and the plurality of N-LEDs 102 may be homogeneously distributed with a second pitch, P2, within a second region 162 on the carrier 151.

Additionally or alternatively, the second region 162 may at least partly be overlapping the first region 161 and P2 may be greater than or equal to 2 times PL

As illustrated in figure 1c, the M-LEDs 101 and the N-LEDs 102 may have other shapes than the round shape exemplified in figure la. For example, as illustrated in figure Id where the M-LEDs 101 and the N-LEDs 102 have rectangular shapes. For example, each of the M-LEDs 101 may have a first length, LI, a first width, Wl, and a first aspect ratio, ARI, defined by Ll/Wl. Each of the N-LEDs 102 may have a second length, L2, a second width, W2, and a second aspect ratio, AR2, defined by L2/W2, and AR2 may be greater than ARI .

As schematically illustrated in figure lb, the M-LEDs 101 may comprise a luminescent material 160 and at least a subset of the N-LEDs 102 are free from any luminescent material.

In some embodiments, and as schematically illustrated in figure 1c, the N- LEDs 102 may further comprises one or more phosphor converted white LEDs. Such a phosphor converted LED may, as exemplified in figure 1c, be realized by way of comprising luminescent material 170.

Turning now to figure le, in some embodiments, the plurality of M-LEDs 101 may be connected with a respective anode 121 having an anode surface area, ASA1, and a respective cathode 122 having a cathode surface area, CSA1. Similarly, the plurality of N- LEDs 102 may be connected with a respective anode 131 having an anode surface area, ASA2, and a respective cathode 132 having a cathode surface area, CSA2. In some embodiments, ASA2 may be greater than or equal to 4 times ASA1 and/or CSA2 may be greater than or equal to 4 times CSA1.

As schematically illustrated in figure If, the G M-LEDs 101 may be connected via a first circuitry, CI1, 141, the one or more B N-LEDs 102 may be connected via a second circuitry, CI2, 142 and the one or more R N-LEDs 102 may be connected via a third circuitry, CI3, 143. The lighting arrangement 100 may further comprise a controller 140 configured to individually control the emission of the first light emitted by said plurality of M-LEDs 101 via the first circuitry 141, the emission of the second light emitted by said one or more of B N-LEDs 102 via the second circuitry 142 and the emission of the third light emitted by said one or more R N-LEDs 102 via the third circuitry 143.

For example, as illustrated in figure 1g, the first circuitry 141 may comprise a first number of parallel arrangements PAI and the second circuitry 142 may comprise a second number of parallel arrangements PA2 or, as illustrated in figure Ih the second circuitry 142 may be a series circuit. In embodiments where both the first and second circuitry 141, 142 are parallel arrangements, then PAI is greater than PA2.

A lamp 200, or a luminaire 200, comprising a lighting arrangement 100 is schematically illustrated in figure 2. Such a lamp 200 or luminaire 200 may comprise a housing 201 and a transparent cover 202.

Claims

CLAIMS:

1. A lighting arrangement (100) configured to provide arrangement light, comprising: a carrier (151); a plurality of first light emitting diodes, M-LEDs, (101) arranged on said carrier, (151) each of the M-LEDs (101) comprising a die (111) having a first surface area, SAI, the first surface area, SAI, having a largest spatial extent, SEI, that is less than or equal to 100 micrometers; a plurality of second light emitting diodes, N-LEDs (102), arranged on said carrier (151), each of the N-LEDs (102) comprising a die (112) having a second surface area, SA2, the second surface area, SA2, having a largest spatial extent, SE2, that is greater than or equal to 300 micrometers; and wherein: the M-LEDs (101) are configured to emit first light, LG1, having a first emission peak wavelength, I, in a wavelength range of green, G, light; the N-LEDs (102) are configured to emit second light, LG2, having a second emission peak wavelength, X2, in a wavelength range of blue, B, light and configured to emit third light, LG3, having a third emission peak wavelength, X3, in a wavelength range of red, R, light; a ratio R1 defined by SA2/SA1 is equal to or larger than 10; and said arrangement light is white light having a correlated color temperature, CCT, in a range from 2000K to 6500K and a color rendering index, CRI, of at least 80.

2. The lighting arrangement (100) according to claim 1, wherein:

SEI is less than or equal to 80 micrometers;

SE2 is greater than or equal to 500 micrometers; and R1 is greater than or equal to 20.

3. The lighting arrangement (100) according to any one of the preceding claims, where: the number of M-LEDs in the plurality of M-LEDs (101) is X, the number of N-LEDs of the plurality of N-LEDs (102) is Y, and wherein X is greater than or equal to 5 times Y.

4. The lighting arrangement (100) according to any one of the preceding claims, wherein: the plurality of M-LEDs (101) are homogeneously distributed with a first pitch, Pl, within a first region (161) on the carrier (151), the plurality of N-LEDs (102) are homogeneously distributed with a second pitch, P2, within a second region (162) on the carrier (151), the second region (162) at least partly overlapping the first region (161), and wherein P2 is greater than or equal to 2 times PL

5. The lighting arrangement (100) according to any one of the preceding claims, wherein: each of the M-LEDs (101) has a first length, LI, a first width, Wl, and a first aspect ratio, ARI, defined by Ll/Wl each of the N-LEDs (102) has a second length, L2, a second width, W2, and a second aspect ratio, AR2, defined by L2/W2, and

AR2 is greater than ARI .

6. The lighting arrangement (100) according to any one of the preceding claims, wherein the M-LEDs (101) comprises a luminescent material (160), and wherein at least a subset of the N-LEDs (102) are free from any luminescent material.

7. The lighting arrangement (100) according to claim 6, wherein the N-LEDs (102) further comprises one or more phosphor converted white LEDs.

8. The lighting arrangement (100) according to any one of the preceding claims, wherein: the M-LEDs (101) comprise G LEDs; and the N-LEDs (102) comprise one or more blue, B, LEDs emitting the second light, LG2, having the second emission peak wavelength, 2, in the wavelength range of blue, B, light and comprise one or more red, R, LEDs emitting the third light, LG3, having the third emission peak wavelength, 3, in the wavelength range of red, R, light.

9. The lighting arrangement (100) according to claim 8, wherein: each B N-LED (102) and/or each R N-LED (102) is neighbored by at least 2 G M-LEDs (101).

10. The lighting arrangement (100) according to any one of the preceding claims, wherein each N-LED (102) comprises 4 sides, wherein each side is neighbored by at least 1 M-LED (101).

11. The lighting arrangement (100) according to any one of the preceding claims, wherein: the plurality of M-LEDs (101) are connected with a respective anode (121) having an anode surface area, ASA1, and a respective cathode (122) having a cathode surface area, CSA1, the plurality of N-LEDs (102) are connected with a respective anode (131) having an anode surface area, ASA2, and a respective cathode (132) having a cathode surface area, CSA2, and

ASA2 is greater than or equal to 4 times ASA1 and/or CSA2 is greater than or equal to 4 times CSA1.

12. The lighting arrangement (100) according to any one of the preceding claims, wherein: the G M-LEDs (101) are connected via a first circuitry, CI1, (141), the one or more B N-LEDs (102) are connected via a second circuitry, CI2,

(142), the one or more R N-LEDs (102) are connected via a third circuitry, CI3,

(143), and wherein: the lighting arrangement (100) comprises a controller (140) configured to individually control the emission of the first light emitted by said plurality of M-LEDs (101) via the first circuitry (141), the emission of the second light emitted by said one or more of B N-LEDs (102) via the second circuitry (142) and the emission of the third light emitted by said one or more R N-LEDs (102) via the third circuitry (143).

13. The lighting arrangement (100) of claim 12, wherein: the first circuitry (121) comprises a first number of parallel arrangements, PAI, - the second circuitry (122) comprises a second number of parallel arrangements, PA2, and

PAI is greater than PA2.

14. The lighting arrangement (100) of claim 12, wherein: - the first circuitry (141) comprises a first number of parallel arrangements,

PAI, the second circuitry (142) is a serial circuitry.

15. A lamp (200) or a luminaire (200) comprising the lighting arrangement (100) according to any one of the preceding claims.