Lighting arrangement with light gradient

Abstract

A LED filament arrangement (100) comprises a plurality of LED filaments (120) arranged in sequence with increasing CCT such that a shift in CCT between neighboring LED filaments is not noticeable by humans, thereby providing a smooth, unobtrusive transition in CCT.

Description

[0001] Lighting arrangement with light gradient

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to lighting arrangements. In particular, the present invention relates to light emitting diode (LED) filament arrangements.

[0004] BACKGROUND OF THE INVENTION

[0005] The use of light emitting diodes (LED) for illumination purposes continues to attract attention. Compared to incandescent lamps, fluorescent lamps, neon tube lamps, etc., LEDs provide numerous advantages such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy. In particular, LED filament lamps are highly appreciated as they are very decorative.

[0006] In lighting design, with the use of LEDs, a light gradient may refer to the change in CCT of light across a space or an object. A gradual shift in CCT from one area to another can create a sense of depth and dimension, while abrupt changes in CCT may make people feel uncomfortable.

[0007] To achieve a light gradient, a combination of different LED light sources with varying CCTs may be used. Alternatively, in some lighting arrangements, lighting fixtures with adjustable CCTs are used. For example, warm white (2700K) fixtures may be used in one area and cool white (5000K) fixtures in another, gradually blending the two to create a cohesive overall effect.

[0008] The goal of a light gradient is to create a comfortable and pleasing environment, and to highlight specific areas or features within a space. By making an improved smooth light gradient in CCT, an improved lighting effect can be achieved.

[0009] SUMMARY OF THE INVENTION

[0010] In light of the above, it is of interest to provide alternative lighting arrangements in order to improve their optical performance and lighting effects. These and other objects are achieved by providing a LED lighting arrangement having the features in the independent claims. Preferred embodiments are defined in the dependent claims. Hence, according to an aspect of the present invention, there is provided a LED filament arrangement, configured to emit LED filament arrangement light, wherein the LED filament arrangement extends along a principal axis, A, and comprises a plurality of LED filaments, configured to emit LED filament light. Each LED filament of the plurality of LED filaments comprises an elongated carrier, and an array of a plurality of LEDs arranged on the elongated carrier, wherein the plurality of LEDs is configured to emit LED light, and an encapsulant at least partly enclosing the plurality of LEDs and at least partly covering the elongated carrier, wherein the encapsulant comprises a luminescent material configured to at least partly convert the emitted LED light into converted light, wherein the LED filament light comprises the converted light, and optionally (part) of the LED light. Each LED filament of the plurality of LED filaments has a respective correlated color temperature, CCTx, wherein the plurality of LED filaments comprises a first LED filament configured to emit first LED filament light having a first correlated color temperature, CCTi, a second LED filament configured to emit second LED filament light having a second correlated color temperature, CCT2, and a third LED filament configured to emit third LED filament light having a third correlated color temperature CCT3, wherein CCTi<CCT2<CCT3. The first LED filament, the second LED filament, and the third LED filament are arranged in sequence in order of increase in CCT, and wherein a difference, D, between the CCT of the emitted LED filament light from neighboring LED filaments of the plurality of LED filaments, for each pair of neighboring LED filaments of the plurality of LED filaments, is within the range 300 K> D > 50 K.

[0011] Thus, the present invention is based on the idea of providing a LED filament arrangement in which the LED light sources are arranged in sequence with increasing CCT such that the neighboring LED filaments have very small difference in CCT. As a result, the shift in CCT between neighboring LED filaments is not noticeable by humans, and the performance, functionality and / or appearance of the LED filament arrangement is improved.

[0012] According to some embodiments, the plurality of LED filaments further comprises a fourth LED filament configured to emit fourth LED filament light having a fourth correlated color temperature, CCT4, wherein CCT1<CCT2<CCT3<CCT4 and wherein the first LED filament, the second LED filament, the third LED filament and the fourth LED filament are arranged in sequence in order of increase in CCT. The obtained effect is an improved smooth light gradient in said arrangement.

[0013] According to some embodiments, the plurality of LED filaments further comprises a fourth LED filament configured to emit fourth LED filament light having a fourth correlated color temperature, CCT4, and a fifth LED filament configured to emit fifth LED filament light having a fifth correlated color temperature, CCTs, wherein CCT1<CCT2<CCT3<CCT4<CCT5 and wherein the first LED filament, the second LED filament, the third LED filament, the fourth LED filament, and the fifth LED filament are arranged in sequence in order of increase in CCT. The obtained effect is a further improved smooth light gradient in said arrangement.

[0014] According to some embodiments, the first luminescent material comprises a green-yellow phosphor configured to at least partly convert the emitted LED light into first converted light comprising green-yellow light having a peak wavelength within a wavelength range of 500-580 nm, and a red phosphor configured to at least partly convert the emitted LED light and / or first converted light into second converted light comprising red light having a peak wavelength within a wavelength range of 600-680 nm.

[0015] According to some embodiments, the first LED filament of the plurality of LED filaments is arranged at a first end of the LED filament arrangement, and wherein CCTi is the lowest CCT of the emitted LED filament light, CCTiow, and a final LED filament of the plurality of LED filaments is arranged at a second end of the LED filament arrangement, opposite the first end of the LED filament arrangement, and wherein the CCT of the emitted LED filament light of the final LED filament is the highest CCT of the emitted LED filament light, CCThigh, and wherein CCThigh - CCTiow > 500 K. According to some embodiments, at least one of CCTiow < 2500 K, and CCThigh > 3000 K, is fulfilled. Preferably, CCThigh - CCTiow > 1000 K.

[0016] Due to these arrangements, the LED arrangement may have a further improved smooth light gradient.

[0017] According to some embodiments, at least three LED filaments of the plurality of LED filaments are arranged in a single plane.

[0018] According to some other embodiments, the principal axis, A, intersects each LED filament of the plurality of LED filaments.

[0019] According to some embodiments, each LED filament of the plurality of LED filaments has a LED filament length, L, and a LED filament width, W, and wherein each LED filament of the plurality of LED filaments is arranged at a distance, SD, from a respective adjacent LED filament, wherein SD is at least one or two times the LED filament width, W and less than one times the LED filament length, L. According to some embodiments, at least one LED filament of the plurality of LED filaments is arranged at a respective angle, a, with respect to the principal axis, A, wherein 70° > ai > 20°.

[0020] According to some embodiments, all LED filaments of the plurality of LED filaments are arranged in parallel with respect to each other.

[0021] According to some embodiments, the plurality of LED filaments comprises at least a first subset of LED filaments, wherein all LED filaments of the at least a first subset of LED filaments are arranged at a same angle, e , with respect to the principal axis, A, the first subset of LED filaments comprises at least two LED filaments, and, at least a second subset of LED filaments, wherein all LED filaments of the at least a second subset of LED filaments are arranged at a same angle, ak, with respect to the principal axis, A, the second subset of LED filaments comprises at least two LED filaments, wherein oy ak. According to some embodiments, LED filaments of the first subset may be arranged perpendicular to the LED filaments of the second subset. In other words, the LED filaments may be arranged in a zigzag configuration, wherein two subsequent / adjacent LED filaments may be arranged at a mutual angle of 90 degrees.

[0022] According to some embodiments, wherein at least a LED filament of the at least a first subset of LED filaments, and at least a LED filament of the at least a second subset of LED filaments, are arranged in a plane, P, extending along the principal axis, A, and at least partially overlap in the plane, P, to form a cross-shape, wherein each of the first and the second subsets comprises at least 3 LED filaments, and the LED filaments forming the cross-shape are arranged to have the same CCT.

[0023] With the above arrangements, different alternatives of the LED filament arrangement are provided, thus different decorative lighting effect can be provided.

[0024] According to some embodiments, the LED filament arrangement further comprises a controller coupled to the plurality of LED filaments, wherein the controller is configured to individually control each LED filament or each subset of LED filaments of the plurality of LED filaments. Due to this arrangement, each LED filament of the plurality of LED filaments can be controlled individually, thus the decorative lighting or CCT can be controlled individually.

[0025] In embodiments, the LED filament arrangement light may be white light e.g. having a corelated color temperature in a range from 2500K to 4000K and / or having a color rendering index of at least 80. The LED filament arrangement light comprises the LED filament light of the plurality of LED filaments. Hence, according to another aspect of the present invention, there is provided a LED filament lamp, the LED filament lamp comprises the LED filament arrangement according to above, a light-transmissive (e.g. transparent) envelope (e.g. tubular or bulb shaped) at least partly encloses the LED filament arrangement, and a base arranged to mechanically and electrically connect the LED filament arrangement to a socket of a luminaire. The present embodiment is advantageous in that the LED lamp, comprising the LED filament arrangement is aesthetically attractive and provides light which has desirable properties such as smoot light gradient thus to provide high comfort for observers.

[0026] Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figs, la-lc schematically show exemplary LED filament arrangements according to embodiments of the present invention.

[0030] Fig. 2 schematically shows exemplary elongated carriers for the LED filaments according to embodiments of the present invention.

[0031] Figs. 3a-3c schematically show exemplary LED lamps according to exemplifying embodiments of the LED filament arrangements of the present invention.

[0032] DETAILED DESCRIPTION

[0033] Figs, la-lc schematically show exemplary LED filament arrangements 100 according to embodiments of the present invention. The LED filament arrangements 100 will be elaborated in reference to Fig. 2. According to Figs, la-lc, the LED filament arrangements 100 comprise a plurality of LED filaments 120 arranged in sequence with increasing CCT such that a shift in CCT between neighboring LED filaments 120 is not noticeable by humans. Specifically, according to some embodiments, the LED filament arrangements 100 are configured to emit LED filament arrangement light, wherein the LED filament arrangement 100 extends along a principal axis, A, and comprises a plurality of LED filaments 120. The plurality of LED filaments 120 is configured to emit LED filament light, wherein each LED filament of the plurality of LED filaments 120 comprises an elongated carrier 125 as shown in Fig. 2, and an array of a plurality of LEDs 130 arranged on the elongated carrier 125, wherein the plurality of LEDs 130 is configured to emit LED light. Each LED filament further comprises an encapsulant at least partly enclosing the plurality of LEDs 130 and at least partly covering the elongated carrier 125, wherein the encapsulant comprises a luminescent material configured to at least partly convert the emitted LED light into converted light, wherein the LED filament light comprises the converted light.

[0034] According to some embodiments, the converted light or the combination of (part ol) the LED light and the converted light is white light, preferably with a color rendering index, CRI, of at least 80. Each LED filament of the plurality of LED filaments 120 has a respective correlated color temperature, CCTx, wherein the CCTx includes color points on the black body locus, BBL. The plurality of LED filaments 120 comprises a first LED filament 120-1 configured to emit first LED filament light having a first correlated color temperature, CCTi, a second LED filament 120-2 configured to emit second LED filament light having a second correlated color temperature, CCT2, and a third LED filament 120-3 configured to emit third LED filament light having a third correlated color temperature, CCT3, wherein CCTi<CCT2<CCT3. The first LED filament 120-1, the second LED filament 120-2, and the third LED filament 120-3 are arranged in sequence in order of increase in CCT, and a difference, D, between the CCT of the emitted LED filament light from neighboring LED filaments of the plurality of LED filaments 120, for each pair of neighboring LED filaments of the plurality of LED filaments 120, is within the range 300 K > D > 50 K, preferably 200 K > D > 50 K, more preferably 150 K > D > 50 K. With this arrangement, a shift in CCT between neighboring LED filaments is not noticeable. According to some embodiments, the plurality of LED filaments 120 further comprises a fourth LED filament 120-4 configured to emit fourth LED filament light having a fourth correlated color temperature, CCT4, and a fifth LED filament 120-5 configured to emit fifth LED filament light having a fifth correlated color temperature, CCTs, wherein CCT1<CCT2<CCT3<CCT4<CCT5 and wherein the first LED filament 120-1, the second LED filament 120-2, the third LED filament 120-3, the fourth LED filament 120-4, and the fifth LED filament 120-5 are arranged in sequence in order of increase in CCT.

[0035] According to some embodiments, the first luminescent material comprises a green-yellow phosphor configured to at least partly convert the emitted LED light into first converted light comprising green-yellow light having a peak wavelength within a wavelength range of 500-580 nm, and a red phosphor configured to at least partly convert the emitted LED light and / or first converted light into second converted light comprising red light having a peak wavelength within a wavelength range of 600-680 nm.

[0036] According to some embodiments, the first LED filament 120-1 of the plurality of LED filaments 120 is arranged at a first end of the LED filament arrangement, and wherein CCTi is the lowest CCT of the emitted LED filament light, CCTiow. Furthermore, a final LED filament of the plurality of LED filaments 120 is arranged at a second end of the LED filament arrangement 100, wherein the second end is opposite to the first end of the LED filament arrangement 100. The CCT of the emitted LED filament light of the final LED filament is the highest CCT of the emitted LED filament light, CCThigh, and wherein CCThigh - CCTiow > 500 K, preferably CCThigh - CCTiow > 1000 K. According to some embodiments, at least one of CCTiow < 2500 K, preferably CCTiow < 2300 K and CCThigh > 3000 K is fulfilled.

[0037] According to some embodiments, the LED filaments are preferably arranged at an angle which is different from 0 or 90 degrees with respect to the principal axis, A, of the LED filament arrangements 100. Preferably, all LED filaments are arranged at the same angle, or alternatively, two subsets of the LED filaments may be arranged like this, wherein each subset has a different angle and includes a cross-shaped LED filament configuration. According to some embodiments, at least one LED filament of the plurality of LED filaments 120 is arranged at a respective angle, a, with respect to the principal axis, A, wherein 70° > oo > 20°. Further according to some alternative embodiments, the plurality of LED filaments 120 comprises at least a first subset of LED filaments such as 120-2 and 120-4, wherein all LED filaments of the at least a first subset of LED filaments are arranged at a same angle, oy, with respect to the principal axis, A, and the first subset of LED filaments comprises at least two LED filaments. The plurality of LED filaments 120 further comprises at least a second subset of LED filaments such as 120-1,120-3 and 120-5, wherein all LED filaments of the at least a second subset of LED filaments are arranged at a same angle, ctk, with respect to the principal axis, A, wherein the second subset of LED filaments comprises at least two LED filaments, and wherein oy ak is fulfilled. Further according to some embodiments, at least a LED filament of the at least a first subset of LED filaments, and at least a LED filament of the at least a second subset of LED filaments, are arranged in a plane, P, extending along the principal axis, A, and at least partially overlap in the plane, P, to form a cross-shape, wherein each of the first and the second subsets comprises at least 3 LED filaments, and the LED filaments forming the cross-shape are arranged to have the same CCT. According to some embodiments, at least three LED filaments of the plurality of LED filaments 120 are arranged in a single plane. According to some further embodiments, the principal axis, A, intersects each LED filament of the plurality of LED filaments 120. Further according to some embodiments, each LED filament of the plurality of LED filaments 120 has a LED filament length, L, and a LED filament width, W, and wherein each LED filament of the plurality of LED filaments 120 is arranged at a distance, SD, from a respective adjacent LED filament, wherein SD is at least two times the LED filament width, W and less than one times the LED filament length, L.

[0038] According to some other embodiments, all LED filaments of the plurality of LED filaments 120 are arranged in parallel with respect to each other.

[0039] According to some embodiments, to control decorative lighting or CCT of the LED filaments 120 separately, the LED filament arrangement may further comprise a controller 185 coupled to the plurality of LED filaments 120, wherein the controller 185 is configured to individually control each LED filament or each subset of LED filaments of the plurality of LED filaments 120.

[0040] Figs. 3a-3c schematically show LED lamps according to exemplifying embodiments of the present invention. The LED filament lamp 300 comprises the LED filament arrangement according to above, a light-transmissive envelope 200 at least partly encloses the LED filament arrangement, and a base 301 arranged to mechanically and electrically connect the LED filament arrangement to a socket 302 of a luminaire 303. The LED filament arrangement 100 is the same as the above described LED filament arrangements according to Figs, la-lc, to avoid redundancy, the details of LED filament arrangement 100 will not be repeated herein. However, the LED filament arrangements 100 in Figs. 3a-3c have different patterns of arrangement. The details of the arrangement pattens with be elaborated below in combination of Figs, la-lc and 3a-3c.

[0041] According to some embodiments, the LED filaments are preferably arranged at an angle which is different from 0 or 90 degrees with respect to the principal axis, A, of the LED filament arrangements 100. Preferably, all LED filaments are arranged at the same angle as shown in Fig. 3a, or alternatively, two subsets of the LED filaments may be arranged like this, wherein each subset has a different angle and includes a cross-shaped LED filament configuration as shown in Fig. 3b and 3c. According to some embodiments, at least one LED filament of the plurality of LED filaments 120 is arranged at a respective angle, a, with respect to the principal axis, A, wherein 70° > m > 20° as shown in Fig. la. Further according to some alternative embodiments, as shown in Fig. lb, the plurality of LED filaments 120 comprises at least a first subset of LED filaments such as 120-2 and 120-4, wherein all LED filaments of the at least a first subset of LED filaments are arranged at a same angle, cy, with respect to the principal axis, A, and the first subset of LED filaments comprises at least two LED filaments. The plurality of LED filaments 120 further comprises at least a second subset of LED filaments such as 120-1,120-3 and 120-5, wherein all LED filaments of the at least a second subset of LED filaments are arranged at a same angle, ak, with respect to the principal axis, A, wherein the second subset of LED filaments comprises at least two LED filaments, and wherein cy ak is fulfilled. Further according to some embodiments, as shown in Fig. 1c, at least a LED filament of the at least a first subset of LED filaments, and at least a LED filament of the at least a second subset of LED filaments, are arranged in a plane, P, extending along the principal axis, A, and at least partially overlap in the plane, P, to form a cross-shape, wherein each of the first and the second subsets comprises at least 3 LED filaments, and the LED filaments forming the cross-shape are arranged to have the same CCT.

[0042] According to some other embodiments, all LED filaments of the plurality of LED filaments 120 are arranged in parallel with respect to each other.

[0043] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Claims

CLAIMS:

1. A light emitting diode, LED, filament arrangement (100), configured to emit LED filament arrangement light, wherein the LED filament arrangement extends along a principal axis, A, and comprises a plurality of LED filaments (120), configured to emit LED filament light, wherein each LED filament of the plurality of LED filaments comprises an elongated carrier (125), and an array of a plurality of LEDs (130) arranged on the elongated carrier, wherein the plurality of LEDs is configured to emit LED light, an encapsulant at least partly enclosing the plurality of LEDs and at least partly covering the elongated carrier, wherein the encapsulant comprises a luminescent material configured to at least partly convert the emitted LED light into converted light, wherein the LED filament light comprises the converted light, wherein each LED filament of the plurality of LED filaments (120) has a respective correlated color temperature, CCTx, wherein the plurality of LED filaments (120) comprises a first LED filament (120-1) configured to emit first LED filament light having a first correlated color temperature, CCTi, a second LED filament (120-2) configured to emit second LED filament light having a second correlated color temperature, CCT2, and a third LED filament (120-3) configured to emit third LED filament light having a third correlated color temperature, CCT3; wherein CCTi<CCT2<CCT3; and wherein the first LED filament, the second LED filament, and the third LED filament are arranged in sequence in order of increase in CCT, and wherein a difference, D, between the CCT of the emitted LED filament light from neighboring LED filaments of the plurality of LED filaments, for each pair of neighboring LED filaments of the plurality of LED filaments, is within the range 300 K > D > 50 K.

2. The LED filament arrangement according to claim 1 , wherein the plurality of LED filaments further comprising a fourth LED filament (120-4) configured to emit fourthLED filament light having a fourth correlated color temperature, CCT4, and a fifth LED filament (120-5) configured to emit fifth LED filament light having a fifth correlated color temperature, CCTs, wherein CCT1<CCT2<CCT3<CCT4<CCT5 and wherein the first LED filament, the second LED filament, the third LED filament, the fourth LED filament, and the fifth LED filament are arranged in sequence in order of increase in CCT.

3. The LED filament arrangement according to claim 1 or 2, wherein the first luminescent material comprises: a green-yellow phosphor configured to at least partly convert the emitted LED light into first converted light comprising green-yellow light having a peak wavelength within a wavelength range of 500-580 nm; and a red phosphor configured to at least partly convert the emitted LED light and / or first converted light into second converted light comprising red light having a peak wavelength within a wavelength range of 600-680 nm.

4. The LED filament arrangement according to any one of the preceding claims, wherein the first LED filament (120-1) of the plurality of LED filaments is arranged at a first end of the LED filament arrangement, and wherein CCTi is the lowest CCT of the emitted LED filament light, CCTiow, and a final LED filament of the plurality of LED filaments is arranged at a second end of the LED filament arrangement, opposite the first end of the LED filament arrangement, and wherein the CCT of the emitted LED filament light of the final LED filament is the highest CCT of the emitted LED filament light, CCThigh, and wherein CCThigh - CCTiow > 500 K.

5. The LED filament arrangement according to claim 4, wherein at least one of CCTiow < 2500 K, and CCThigh > 3000 K is fulfilled.

6. The LED filament arrangement according to claim 4 or 5, wherein CCThigh - CCTiow > 1000 K.

7. The LED filament arrangement according to any one of the preceding claims, wherein at least three LED filaments of the plurality of LED filaments are arranged in a single plane.

8. The LED filament arrangement according to any one of the preceding claims, wherein the principal axis, A, intersects each LED filament of the plurality of LED filaments.

9. The LED filament arrangement according to any one of the preceding claims, wherein each LED filament of the plurality of LED filaments has a LED filament length, L, and a LED filament width, W; and wherein each LED filament of the plurality of LED filaments is arranged at a distance, SD, from a respective adjacent LED filament, wherein SD is at least two times the LED filament width, W and less than one times the LED filament length, L.

10. The LED filament arrangement according to any of preceding claims, wherein at least one LED filament of the plurality of LED filaments is arranged at a respective angle, (Xi, with respect to the principal axis, A, wherein 70° > m > 20°.

11. The LED filament arrangement according to any one of the preceding claims, wherein all LED filaments of the plurality of LED filaments are arranged in parallel with respect to each other.

12. The LED filament arrangement according to claim 10, wherein the plurality of LED filaments comprises at least a first subset of LED filaments, wherein all LED filaments of the at least a first subset of LED filaments are arranged at a same angle, oy, with respect to the principal axis, A, the first subset of LED filaments comprises at least two LED filaments, and, at least a second subset of LED filaments, wherein all LED filaments of the at least a second subset of LED filaments are arranged at a same angle, ctk, with respect to the principal axis, A, the second subset of LED filaments comprises at least two LED filaments, wherein oy ctk.

13. The LED filament arrangement according to claim 12, wherein at least a LED filament of the at least a first subset of LED filaments, and at least a LED filament of the at least a second subset of LED filaments, are arranged in a plane, P, extending along the principal axis, A, and at least partially overlap in the plane, P, to form a cross-shape, wherein each of the first and the second subsets comprises at least 3 LED filaments, and the LED filaments forming the cross-shape are arranged to have the same CCT.

14. The LED filament arrangement according to any of preceding claims, further comprising a controller (185) coupled to the plurality of LED filaments, wherein the controller is configured to individually control each LED filament or each subset of LED filaments of the plurality of LED filaments.

15. A LED filament lamp (300), comprising the LED filament arrangement according to any one of the preceding claims, a light-transmissive envelope (200) at least partly encloses the LED filament arrangement, and a base (301) arranged to mechanically and electrically connect the LED filament arrangement to a socket (302) of a luminaire (303).

Images