Lighting arrangement and LED filament arrangement arranged to emit white light

Abstract

There is provided a lighting arrangement (100) and a light emitting diode, LED, filament arrangement (500) configured to emit white lighting arrangement light (110) and LED filament light (505), respectively. The lighting arrangement comprises a carrier (120), a plurality of first LEDs (130), arranged on the carrier, configured to emit first LED light (140), an encapsulant (150) comprising a first luminescent material (155) comprising a first phosphor configured to at least partly convert the emitted first LED light into first converted light (160) comprising green light, wherein the emitted white lighting arrangement light comprises the green light and red light. The emitted white lighting arrangement light has a correlated color temperature, CCT, in a range of 1500-2500 K, and wherein at most 2% of the white lighting arrangement light in the visible wavelength range is in a wavelength range below 495 nm.

Description

[0001] Lighting arrangement and LED filament arrangement arranged to emit white light

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to lighting arrangements comprising light emitting diodes, LED. More specifically, the present invention is related to lighting arrangements and LED filaments arrangements arranged to emit white light.

[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] Due to the advantageous aspects of the use of LEDs, the interest has rapidly increased to replace conventional light sources with LEDs in many lighting arrangements. It will be appreciated that this replacement, also called retrofitting, is appreciated and desired by users who wish to have the look of an incandescent bulb. The light source replacement (retrofitting) is often performed by removing the conventional light source(s) from the luminaire (e.g. a lamp holder) of the lighting arrangement and attaching the LEDs, LED arrangement(s) or LED device(s) into the luminaire. One of these concepts is based on LED filaments which are placed in a bulb, as the appearance of lamps of this kind are appreciated as they are highly decorative.

[0007] Lighting devices and lamps comprising LEDs, whose light during operation are free from violet light (i.e. 380 nm - 420 nm) and / or blue light (i.e. 420 nm - 495 nm), are commercially available. Lighting devices and lamps of this kind may be used in applications to prevent sleep disruption of humans, as well as preventing negative impact on animal behavior, during the evening or night.

[0008] However, by the absence of violet and / or blue light of the light as emitted from lighting devices and lamps during operation, the light may be perceived as unnatural and / or non-aesthetical. Hence, it is an object of the present invention to combine the advantageous properties of light, emitted from LED lighting devices and / or LED lamps, which is free from violet and / or blue light, whilst still achieving a natural and / or aesthetically pleasing light.

[0009] US 10697591 discloses a low-luminance LED lamp that produces light designed for evening reading, relaxation and sleep. Low melanopic input balanced with high color rendering and a warm Correlated Color Temperature (CCT) produces a light with reduced circadian / melanopic input. An engineered LED phosphor produces a spectrum with relatively low blue and green content. This is balanced with a high CRT and the preference for warm (low-CCT) lighting in the evening.

[0010] SUMMARY OF THE INVENTION

[0011] It is of interest to combine the advantageous properties of LEDs with respect energy efficiency, light distribution purposes and / or aesthetics with the properties of light which is free from violet and / or blue light, whilst still providing a natural and / or aesthetically pleasing light emission.

[0012] This and other objects are achieved by providing a lighting arrangement and a LED filament having the features in the independent claims. Preferred embodiments are defined in the dependent claims.

[0013] Hence, according to the first aspect of the present invention, there is provided a lighting arrangement configured to emit white lighting arrangement light. The lighting arrangement comprises a carrier, a plurality of first LEDs arranged on the carrier, wherein the plurality of first LEDs is configured to emit first LED light comprising violet-blue light having a peak wavelength, Xo, in a wavelength range of 380 - 495 nm, and an encapsulant at least partially enclosing the carrier and at least partially enclosing the plurality of first LEDs. The encapsulant comprises a first luminescent material comprising a first phosphor configured to at least partly convert the emitted first LED light into first converted light comprising green light having a green peak wavelength, Xi, in a wavelength range of 505-520 nm. The emitted white lighting arrangement light comprises the green light, and red light having a peak wavelength, X2, in a wavelength range of 610-680 nm (or 610-660 nm). The emitted white lighting arrangement light has a correlated color temperature, CCT, in a range of 1500-2500 K, and wherein the first converted light has a spectral light distribution with a full width at half maximum, FWHM, of < 40 nm such that at most 2% of the emitted white lighting arrangement light in the visible wavelength range is in a wavelength range below 495 nm. According to the second aspect of the present invention, there is provided a LED filament arrangement configured to emit white LED filament light. The LED filament arrangement comprises at least one LED filament comprising an elongated carrier, at least one first linear array of a plurality of first LEDs, arranged on the elongated carrier, wherein the plurality of first LEDs is configured to emit first LED light comprising violet-blue light having a peak wavelength, Xo, in a wavelength range of 380 - 495 nm, and at least one elongated encapsulant at least partially enclosing the elongated carrier and at least partially enclosing the plurality of first LEDs. The at least one elongated encapsulant comprises a first luminescent material comprising a first phosphor configured to at least partly convert the emitted first LED light into first converted light comprising green light having a green peak wavelength, Xi, in a wavelength range of 505-520 nm. The emitted white LED filament light comprises the green light, and red light having a peak wavelength, X2, in a wavelength range of 610-680 nm (or 610-660 nm). The emitted white LED filament light has a correlated color temperature, CCT, in a range of 1500-2500 K, and wherein the first converted light has a spectral light distribution with a full width at half maximum, FWHM, of < 40 nm such that at most 2% of the emitted white LED filament light in the visible wavelength range is in a wavelength range below 495 nm.

[0014] Therewith, the LED filament arrangement is a lighting arrangement that comprises at least one LED filament wherein the carrier is an elongated carrier and the plurality of first LEDs is arranged in at least one first linear array on the elongated carrier.

[0015] Thus, the present invention is based on the idea of providing a lighting arrangement and / or a LED filament arrangement which is arranged to emit (extremely) warm white light which is free from violet and / or blue light. The suppression of violet-blue light from the white light is manifested by the first LED light comprising (or even constituting, i.e. being) violet-blue light, having a peak wavelength, Xo, in a wavelength range of 380 - 495 nm, whereas at most 2% (or at most 1% such as 0%) of the emitted white LED filament light in the visible wavelength range is in a wavelength range below 495 nm. By the features of the lighting arrangement and the LED filament arrangement, including the encapsulant, the emission of green and red light, the (low) CCT and the concentration of white light in the specified wavelength range, the lighting arrangement and the LED filament arrangement combine the advantageous properties of LEDs with respect energy efficiency, light distribution purposes and / or aesthetics with the properties of light which is free from violet and / or blue light, whilst still providing a natural and / or aesthetically pleasing light emission. It will be appreciated that the lighting arrangement and the LED filament arrangement share this same common general inventive concept.

[0016] There is provided a lighting arrangement, and / or a LED filament arrangement, configured to emit white light. By “white light”, it is here meant visible light in the wavelength range of 400-700 nm. The lighting arrangement comprises a carrier and a plurality of first LEDs arranged on the carrier. In case of a LED filament arrangement, the at least one LED filament comprises an elongated carrier and at least one first linear array of a plurality of first LEDs arranged on the elongated carrier, wherein the plurality of first LEDs is configured to emit first LED light comprising (or even constituting, i.e. being) violet-blue light having a peak wavelength, Xo, in a wavelength range of 380 - 495 nm. By the term “carrier”, it is here meant an element, substrate, printed circuit board, PCB, or the like, arranged to mechanically and / or electrically support the first LEDs. Hence, the plurality of first LEDs may be arranged, mounted and / or mechanically coupled on / to the carrier (e.g. a substrate), wherein the carrier is configured to mechanically and / or electrically support the first LEDs. The lighting arrangement (LED filament arrangement) further comprises an (elongated) encapsulant at least partially enclosing the (elongated) carrier and at least partially enclosing the plurality of first LEDs. By the term “encapsulant”, it is here meant a material, element, arrangement, or the like, which is configured or arranged to at least partially surround, encapsulate and / or enclose the carrier and the plurality of first LEDs. The encapsulant comprises a first luminescent material comprising a first phosphor configured to at least partly convert the emitted first LED light into first converted light. The first converted light comprises (or even constitutes, i.e. is) green light having a green peak wavelength, Xi, in a wavelength range of 505-520 nm. Hence, the first phosphor may be described or defined as a narrow-band green phosphor. By “peak wavelength”, it is here meant a (dominant) peak wavelength or centroid wavelength, i.e. a wavelength at which the light reaches a maximum intensity. The emitted white lighting arrangement (LED filament) light comprises the green light, and red light having a peak wavelength, X2, in a wavelength range of 610-680 nm (or 610-660 nm). The emitted white lighting arrangement (LED filament) light has a CCT in a range of 1500-2500 K. The first converted light has a spectral light distribution with a full width at half maximum, FWHM, of < 40 nm (preferably < 35 nm, more preferred < 30 nm, and even more preferred < 28 nm) such that at most 2% (or at most 1% such as 0%) of the emitted white lighting arrangement light in the visible wavelength range is in a wavelength range below 495 nm. According to an embodiment of the present invention, the lighting arrangement may further comprise a plurality of second LEDs arranged on the carrier, wherein the plurality of second LEDs is configured to emit second LED light comprising the red light. For example, the emitted second LED light may even constitute (i.e. be) the red light. It will be appreciated that the plurality of second LEDs constitutes other LEDs than the plurality of first LEDs. It is preferred that the number of second LEDs is higher, or even much higher, than the number of first LEDs. For example, the number of second LEDs may be twice as high as the number of first LEDs. The present embodiment is advantageous in that the lighting arrangement may be customized in order to achieve desired properties, for example comprising a relatively large number (or alternatively, a relatively small number) of second LEDs, which in turn emit the red light.

[0017] According to an embodiment of the present invention, the encapsulant may comprise a second luminescent material comprising a second phosphor configured to at least partly convert at least one of the emitted first LED light and the first converted light into second converted light comprising the red light. For example, the second converted light may even constitute (i.e. be) the red light. Hence, the second luminescent material with the second phosphor may convert the first LED light emitted from the plurality of first LEDs and / or the first converted light from the encapsulant. The second phosphor may be described or defined as a narrow-band red phosphor.

[0018] According to an embodiment of the present invention, the second converted light may have a light distribution with a full width at half maximum, FWHM, of less than 30 nm.

[0019] According to an embodiment of the present invention, the second phosphor may comprise a narrow-band phosphor comprising a manganese-activated narrow-band red fluoride phosphor with a peak emission wavelength range of 628-640 nm.

[0020] According to an embodiment of the present invention, a relation between a phosphor concentration, Pi, of the first phosphor and a phosphor concentration, P2, of the second phosphor, fulfills P2 > 3 Pi. Hence, the phosphor concentration, Pi, of the first phosphor is at least three times as high as the phosphor concentration, P2, of the second phosphor.

[0021] According to examples, the second phosphor may comprise or is a Mn- activated narrow-band class red phosphor.

[0022] With regard to Mn-activated narrow-band class red phosphors, this refers to a luminescent material of the type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, for instance comprising one or more of silicon and titanium, wherein X comprises a monovalent anion, at least comprising fluorine.

[0023] Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also lithium and / or cesium may be applied. In a preferred example, M comprises at least potassium. In yet another example, M comprises at least rubidium. The phrase “wherein M comprises at least potassium” indicates for instance that of all M cations in a mole M’xM2-2xAX6 , a fraction comprises K+and an optionally remaining fraction comprises one or more other monovalent (alkaline) cations (see also below). In another preferred example, M comprises at least potassium and rubidium. Optionally, the M’XM2- 2XAXe luminescent material has the hexagonal phase. In yet another example, the M’XM2- 2xAXe luminescent material has the cubic phase. For x=0, the composition is M2AX6.

[0024] Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba.

[0025] The term “tetravalent manganese” refers to Mn4+. This is a well-known luminescent ion. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’xM2-2xAX6 doped with tetravalent manganese may also be indicated as M’xM2-2xAi-mMnmX6. The mole percentage of manganese, i.e. the percentage it replaces the tetravalent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e. m is in the range of 0.001-0.15, especially in the range of 0.01-0.12.

[0026] As indicated above, X relates to a monovalent anion, but at least comprises fluorine. Other monovalent anions that may optionally be present may be selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I).

[0027] According to an example, M’xM2-2xAX6 comprises K^SiFe (indicated herein also as KSiF system). As indicated above, in another preferred example, M’xM2-2xAX6 comprises KRbSiFe (herein also indicated as K,Rb system). As indicated above, part of silicon is replaced by manganese (i.e. the formula may also be described as K2Sii-mMnmF6 or KRbSii-mMnmF6, with m as indicated above, or as KRbSiFe:Mn and K2SiFe:Mn, respectively). As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant” or “activator”. Hence, the hexafluorosilicate is doped or activated with manganese (Mn4+).

[0028] In specific examples, the luminescent material may comprise (K,Rb)2SiFe:Mn4+. Alternatively or additionally, in examples the third luminescent material may comprise K2SiFe:Mn4+. Alternatively or additionally, in examples the third luminescent material may comprise K2TiFe:Mn4+. In examples, the third luminescent material may comprise K2(Si,Ti)Fe:Mn4+. As can be derived from the above, “Si,Ti” may indicate one or more of Si and Ti.

[0029] According to an embodiment of the present invention, the first converted light may have a light distribution with a full width at half maximum, FWHM, of less than 30 nm. For example, the first phosphor may comprise a narrow-band phosphor.

[0030] According to an embodiment of the present invention, the first phosphor may comprise at least one of a barium magnesium aluminate, BAM, green phosphor and quantum dots. Hence, the first phosphor may comprise BAM green phosphor and / or quantum dots.

[0031] According to an embodiment of the present invention, the green peak wavelength, i, may be in a wavelength range of 508-517 nm.

[0032] According to an embodiment of the present invention, the encapsulant may comprise a third luminescent material comprising a third phosphor configured to at least partly convert at least one of the emitted first LED light and the first converted light into third converted light, wherein the third phosphor has a peak wavelength in a wavelength range of 520-590 nm. Hence, the third luminescent material with the third phosphor may convert the first LED light emitted from the plurality of first LEDs and / or the first converted light from the encapsulant. It may be preferred to provide a relatively low concentration of the third phosphor with respect to the first phosphor, in order to be on the black body locus, BBL, at the given CCT range. According to an example, the third phosphor may be a broad-band (yellow) phosphor and wherein the third converted light has a spectral light distribution with a full width at half maximum, FWHM, of more than 60 nm.

[0033] According to an example of the present invention, the encapsulant may comprise a fourth luminescent material comprising a fourth phosphor configured to at least partly convert at least one of the emitted first LED light and the first converted light into fourth converted light, wherein the fourth phosphor has a peak wavelength in a wavelength range of 560-610 nm. Hence, the fourth luminescent material with the fourth phosphor may convert the first LED light emitted from the plurality of first LEDs and / or the first converted light from the encapsulant. The fourth phosphor may be described or defined as a narrowband fourth phosphor.

[0034] According to an embodiment of the second aspect of the present invention, there is provided a LED filament arrangement, wherein the elongated carrier comprises an at least partially light-transmissive material and comprises a first surface and a second surface oppositely arranged the first surface, wherein the plurality of LEDs is arranged on the first surface. The first surface faces a first portion of the elongated encapsulant, and the second surface faces a second portion of the elongated encapsulant, wherein the second portion of the elongated encapsulant comprises the first phosphor. By the term “light-transmissive”, it is here meant that the carrier comprises a material, composition and / or substance which is transparent and / or translucent, allowing light to be transmitted through the carrier. Due to the light-transmissive material of the elongated carrier, the first LED light emitted from the plurality of first LEDs may be transmitted through the carrier and be converted by the first phosphor provided in the second portion of the elongated encapsulant. The present embodiment is further advantageous in that the LED filament light may be decorative and / or aesthetically pleasing.

[0035] According to an embodiment of the present invention, there is provided a LED filament lamp comprising the LED filament arrangement according to any one of the preceding embodiments of the second aspect of the present invention. The LED filament lamp comprises a light-transmissive envelope at least partly enclosing the at least one LED filament and a base electrically connected to the at least one LED filament for a supply of power to the plurality of LEDs of the at least one LED filament and configured to mechanically and electrically connect the lamp to a socket of a luminaire. By the term “envelope”, it is here meant an enclosing element, such as a cap, cover, or the like, comprising an at least partial translucent and / or transparent material. The present embodiment is advantageous in that the LED filament arrangement according to the invention may be conveniently arranged in substantially any luminaire, lamp or lighting device, such as a tubular lighting device, a LED filament lamp or a LED filament luminaire, luminaire, lighting system, or the like. The LED filament lamp may further comprise a driver for supplying power to the LEDs of the LED filament lamp.

[0036] According to an embodiment of the present invention, there is provided a LED filament lamp, wherein the envelope comprises an amber colored layer. The present embodiment is advantageous in that the layer of amber color renders an aesthetically pleasant vintage effect of the LED filament lamp. The present embodiment is further advantageous considering the effect that the LED filament arrangement is arranged to emit white light which is free from violet and / or blue light: as the amber-colored layer only absorbs blue light and due to the fact that there is no blue light, the layer does not (or hardly) absorb light.

[0037] 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.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] Fig. 1 schematically shows a LED filament lamp according to the prior art, Fig. 2 schematically shows a lighting arrangement according to an exemplifying embodiment of the first aspect of the present invention,

[0041] Figs. 3 and 4 schematically show LED filament arrangements according to exemplifying embodiments of the second aspect of the present invention,

[0042] Fig. 5 schematically shows a portion of a LED filament arrangement according to an exemplifying embodiment of the second aspect of the present invention, Fig. 6a is a diagram of intensity as a function of wavelength of the green light of the first converted light according to an exemplifying embodiment of the present invention,

[0043] Fig. 6b is a diagram of intensity as a function of wavelength of the red light according to an exemplifying embodiment of the present invention,

[0044] Fig. 7 schematically shows a portion of a LED filament arrangement in crosssection according to an embodiment of the second aspect of the present invention, and

[0045] Fig. 8 shows a LED filament lamp according to an exemplifying embodiment of the present invention.

[0046] DETAILED DESCRIPTION

[0047] Fig. 1 shows a LED filament lamp 10 according to the prior art, comprising a plurality of LED filaments 20. LED filament lamps 10 of this kind are highly appreciated as they are very decorative, as well as providing numerous advantages compared to incandescent lamps such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy. LED filament lamps 10 of this kind are able to produce warm white light. However, it is of interest to improve the properties of the light emitted from the LED filaments 20 without impairing the appearance and / or the decorative aspect of the LED filaments 20 and / or the LED filament lamps 10. Fig. 2 schematically shows a lighting arrangement 100 according to an exemplifying embodiment of the first aspect of the present invention. The lighting arrangement 100 is configured to emit white lighting arrangement light 110, i.e. visible light in the wavelength range of 400-700 nm. The lighting arrangement 100 comprises a plurality of first LEDs 130 arranged on a carrier 120. The plurality of first LEDs 130 is configured to emit first LED light 140. The first LED light 140 comprises (or is) violet-blue light having a peak wavelength, o, in a wavelength range of 380-495 nm. The lighting arrangement 100 further comprises an encapsulant 150 which at least partially encloses the carrier 120 and at least partially encloses the plurality of first LEDs 130. The encapsulant 150 comprises a first luminescent material 155 comprising a first phosphor configured to at least partly convert the emitted first LED light 140 into first converted light 160. The first converted light 160 comprises (or is) green light having a green peak wavelength, i, in a wavelength range of 505-520 nm. Hence, the first phosphor may be described or defined as a narrow-band green phosphor. The emitted white lighting arrangement light 110 comprises the green light, and red light 161 having a (red) peak wavelength, 2, in a wavelength range of 610-680 nm (or 610-660 nm). The emitted white lighting arrangement light 110 has a CCT in a range of 1500-2500 K. At most 2% (or at most 1% such as 0%) of the emitted white lighting arrangement light 110 in the visible wavelength range is in a wavelength range below 495 nm. Expressed differently, at least 98% of the white lighting arrangement light 110 in the visible wavelength range may be in a wavelength range of 500-800 nm.

[0048] Fig. 3 schematically shows a LED filament arrangement 500 according to an exemplifying embodiment of the second aspect of the present invention. The LED filament arrangement 500 is configured to emit white LED filament light 505, i.e. visible light in the wavelength range of 400-700 nm. The LED filament arrangement 500 comprises at least one LED filament 510 (shown as a single LED filament 510 in Fig. 2). Preferably, the LED filament 510 has a length, L, and a width, W, wherein L > 5W. The LED filament 510 may be arranged in a straight configuration or in a non-straight configuration such as for example a curved configuration, a 2D / 3D spiral or a helix. The LED filament arrangement 500 further comprises an elongated carrier 520. The elongated carrier 520 may be in the form of an element, substrate, printed circuit board, PCB, or the like. The elongated carrier 520 may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer or metal e.g. a film or foil). The LED filament arrangement 500 comprises at least one first linear array 530 (shown as a single first linear array 530 in Fig. 2) of first LEDs 531 arranged on the elongated carrier 520, whereby the elongated carrier 520 is configured to mechanically and / or electrically support the plurality of first LEDs 531. The plurality of first LEDs 531 is configured to emit first LED light 540. The first LED light 540 comprises (or is) violet-blue light having a peak wavelength, o, in a wavelength range of 380-495 nm. The LED filament arrangement 500 further comprises an elongated encapsulant 550 which at least partially encloses the elongated carrier 520 and at least partially encloses the plurality of first LEDs 531. The encapsulant 550 comprises a first luminescent material 555 comprising a first phosphor configured to at least partly convert the emitted first LED light 540 into first converted light 560. The first converted light 560 comprises (or is) green light having a green peak wavelength, i, in a wavelength range of 505-520 nm. Hence, the first phosphor may be described or defined as a narrow-band green phosphor. The emitted white LED filament light 505 comprises the green light, and red light 561 having a (red) peak wavelength, 2, in a wavelength range of 610-680 nm (or 610-660 nm). The emitted white LED filament light 505 has a CCT in a range of 1500-2500 K. At most 2% (or at most 1% such as 0%) of the emitted white LED filament light 505 in the visible wavelength range is in a wavelength range below 495 nm. Expressed differently, at least 98% of the white LED filament light 505 in the visible wavelength range may be in a wavelength range of 500-800 nm.

[0049] Fig. 4 schematically shows a LED filament arrangement 500 according to an exemplifying embodiment of the second aspect of the present invention. The LED filament arrangement 500 shown in Fig. 4 corresponds to the LED filament arrangement 500 shown in Fig. 3, and it is referred to Fig. 3 and the associated text for an increased understanding. Compared to Fig. 3, the LED filament arrangement 500 shown in Fig. 4 comprises a plurality of second LEDs 200 arranged on the elongated carrier 520, wherein the plurality of second LEDs 200 is configured to emit second LED light 210 comprising (or being) the red light 561 of Fig. 3.

[0050] Fig. 5 schematically shows a portion of a LED filament arrangement 500 according to an exemplifying embodiment of the second aspect of the present invention. It should be noted that many features and / or functions are omitted in Fig. 5 with respect to the LED filament arrangement 500 shown in Fig. 3 and / or Fig. 4, and it is referred to that or those figures for an increased understanding of the LED filament arrangement 500. In Fig. 5, the encapsulant 550, which at least partially encloses the carrier 520, comprises a plurality of luminescent materials 555, 565, 575, 585. It should be noted that the shape and / or position of each luminescent material 555, 565, 575, 585 is indicated for illustrative purposes only. Furthermore, it should be noted that the LED filament arrangement 500 may comprise substantially any combination(s) of luminescent materials 555, 565, 575, 585. As described in Fig. 3 and the associated text, the LED filament arrangement 500 comprises a first luminescent material 555 which in turn comprises the first (green) phosphor configured to at least partly convert the emitted first LED light into first converted light comprising (or being) green light having a green peak wavelength, i, in a wavelength range of 505-520 nm. The first phosphor may comprise barium magnesium aluminate, BAM, green phosphor and / or quantum dots. The encapsulant 520 may furthermore comprise a second luminescent material 565 comprising a second (red) phosphor configured to at least partly convert at least one of the emitted first LED light and the first converted light into second converted light comprising (or being) the red light. The second converted light may have a light distribution with a full width at half maximum, FWHM, of less than 30 nm. Furthermore, the second phosphor may comprise a narrow-band phosphor comprising a manganese-activated narrowband red fluoride phosphor with a peak emission wavelength range of 628-640 nm. It should be noted that there may be different phosphor concentration ratios or relations between the first and second phosphors. For example, a relation between a phosphor concentration, Pi, of the first phosphor and a phosphor concentration, P2, of the second phosphor, may fulfill P2 > 3 Pi, i.e. that the concentration of the second phosphor is at least three times as high as the concentration of the first phosphor. The encapsulant 520 of the LED filament arrangement 500 may furthermore comprise a third luminescent material 575 comprising a third (yellow) phosphor configured to at least partly convert the emitted first LED light and / or the first converted light into third converted light. The third phosphor may be a broad-band phosphor. The third converted light may have a spectral light distribution with a full width at half maximum, FWHM, of more than 60 nm. Hence, the LED filament arrangement 500 may have a configuration of a (narrow band) first (green) phosphor, a second (red) phosphor, which preferably is also narrow band, and a third (yellow) phosphor, e.g. YAG. The encapsulant 520 of the LED filament arrangement 500 may furthermore comprise a fourth luminescent material 585 comprising a fourth phosphor configured to at least partly convert the emitted first LED light and / or the first converted light into fourth converted light, wherein the fourth phosphor has a peak wavelength in a wavelength range of 560-610 nm.

[0051] Figs. 6a and 6b schematically disclose intensity distributions (y-axis, arb. units) as a function of wavelength (x-axis, nm). The leftmost distribution (curve) in Fig. 6a shows the excitation of the first phosphor (i.e. at which wavelengths the first phosphor can be excited), comprised in the first luminescent material, of the encapsulant. The first phosphor may be excited up to approximately 460 nm. It should be noted that the first phosphor excitation curve as shown in Fig. 6a is an example, and that other phosphor excitation distributions or curves are possible. The rightmost distribution (curve) in Fig. 6a shows the emitted first LED light converted into first converted light via the encapsulant comprising the first luminescent material, which in turn comprises the first phosphor. This (green) emission spectrum has a green (dominant) peak wavelength, i, in a wavelength range of 505-520 nm (in Fig. 6a, the green (dominant) peak wavelength, i, is approximately 515 nm. The leftmost distribution (curve) in Fig. 6b shows the excitation of the second phosphor (i.e. at which wavelengths the second phosphor can be excited), comprised in the second luminescent material, of the encapsulant. It should be noted that the second phosphor excitation curve as shown in Fig. 6b is an example, and that other phosphor excitation distributions or curves are possible. The rightmost distribution (curve) in Fig. 6b shows the emitted white LED filament light comprising red light having a red (dominant) peak wavelength, 2, in a wavelength range of 610-680 nm (or 610-660 nm). The second phosphor, which may comprise KSiF, may emit red light around approximately 630 nm with a narrow band. This narrow band of the second phosphor is advantageous compared to other phosphors which have a Tong tail’ in the far-red region, which light is less efficient as it is further away from the eye-sensitivity peak.

[0052] Fig. 7 schematically shows a portion of a LED filament arrangement 500 in cross-section according to an embodiment of the second aspect of the present invention. The elongated carrier 520 of the LED filament 510 comprises an at least partially light- transmissive material. The elongated carrier 520 comprises a first surface 580 and a second surface 585 oppositely arranged the first surface 580. The plurality of LEDs 531 is arranged on the first surface 580. The first surface 580 faces a first portion 590 of the elongated encapsulant 550, and the second surface 585 faces a second portion 595 of the elongated encapsulant 550. The second portion 595 of the elongated encapsulant 550 comprises the first phosphor.

[0053] Fig. 8 schematically shows a LED filament lamp 600 according to an embodiment of the present invention. The LED filament lamp 600, which may constitute substantially any kind of lamp or luminaire, comprises the LED filament arrangement 500 according to any one of the previously described embodiments of the second aspect of the present invention. The LED filament lamp 600 further comprises a light-transmissive envelope 610, which is exemplified as being bulb-shaped. The envelope 610 at least partially encloses the LED filament(s) 510 of the LED filament arrangement 500. The LED filament lamp 600 further comprises a base 620 electrically connected to the LED filament(s) 510 for a supply of power to the plurality of LEDs of the LED filament(s) 510. The base 620 is configured to mechanically and electrically connect the LED filament lamp 600 to a socket of a luminaire. The envelope 610 may, according to an example, comprise an amber-colored layer.

[0054] 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. For example, one or more of the LED filament(s) 510, the elongated carrier 520, etc., may have different shapes, dimensions and / or sizes than those depicted / described.

Claims

CLAIMS:

1. A lighting arrangement (100) configured to emit white lighting arrangement light (110), the lighting arrangement comprising: a carrier (120), a plurality of first light emitting diodes, LEDs (130) arranged on the carrier, wherein the plurality of first LEDs is configured to emit first LED light (140) comprising violet-blue light having a peak wavelength, o, in a wavelength range of 380-495 nm, an encapsulant (150) at least partially enclosing the carrier and at least partially enclosing the plurality of first LEDs, wherein the encapsulant comprises a first luminescent material (155) comprising a first phosphor configured to at least partly convert the emitted first LED light into first converted light (160) comprising green light having a peak wavelength, i, in a wavelength range of 505-520 nm, wherein the emitted white lighting arrangement light comprises: the green light, and red light having a peak wavelength, 2, in a wavelength range of 610-680 nm, wherein the emitted white lighting arrangement light has a correlated color temperature, CCT, in a range of 1500-2500 K, and wherein the first converted light has a spectral light distribution with a full width at half maximum, FWHM, of < 40 nm such that at most 2% of the emitted white lighting arrangement light in the visible wavelength range is in a wavelength range below 495 nm.

2. The lighting arrangement according to claim 1, further comprising: a plurality of second LEDs (200a-d) arranged on the carrier, wherein the plurality of second LEDs is configured to emit second LED light (210) comprising the red light.

3. The lighting arrangement according to claim 1 or 2, wherein the encapsulant comprises a second luminescent material (565) comprising a second phosphor configured toat least partly convert at least one of the emitted first LED light and the first converted light into second converted light (240) comprising the red light.

4. The lighting arrangement according to claim 3, wherein the second converted light has a spectral light distribution with a full width at half maximum, FWHM, of less than 30 nm.

5. The lighting arrangement according to claim 4, wherein the second phosphor comprises a narrow-band phosphor comprising a manganese-activated narrow-band red fluoride phosphor with a peak emission wavelength range of 628-640 nm.

6. The lighting arrangement according to claim 5, wherein a relation between a phosphor concentration, Pi, of the first phosphor and a phosphor concentration, P2, of the second phosphor, fulfills P2 > 3 Pi.

7. The lighting arrangement according to any one of the preceding claims, wherein the first phosphor comprises at least one of a barium magnesium aluminate, BAM, green phosphor and quantum dots.

8. The lighting arrangement according to any one of the preceding claims, wherein the peak wavelength, i, is in a wavelength range of 508-517 nm.

9. The lighting arrangement according to any one of the preceding claims, wherein the encapsulant comprises a third luminescent material (575) comprising a third phosphor configured to at least partly convert at least one of the emitted first LED light and the first converted light into third converted light (340), wherein the third phosphor has a peak wavelength in a wavelength range of 520-590 nm.

10. The lighting arrangement according to claim 9, wherein the third phosphor is a broad-band phosphor and wherein the third converted light has a spectral light distribution with a full width at half maximum, FWHM, of more than 60 nm.

11. The lighting arrangement according to claim 1, wherein the lighting arrangement is an LED filament arrangement that comprises at least one LED filament (510)wherein the carrier is an elongated carrier and the plurality of first LEDs (531) is arranged in at least one first linear array (530) on the elongated carrier (520).

12. The LED filament arrangement according to claim 11, wherein the elongated carrier comprises at least partially light-transmissive material and comprises a first surface (580) and a second surface (587) oppositely arranged the first surface, wherein the plurality of LEDs is arranged on the first surface, wherein the first surface faces a first portion (590) of the elongated encapsulant, and the second surface faces a second portion (595) of the elongated encapsulant, wherein the second portion of the elongated encapsulant comprises the first phosphor.

13. A LED filament lamp (600), comprising: the LED filament arrangement according to claim 11 or 12, a light-transmissive envelope (610) at least partly enclosing the at least one LED filament, and a base (620) electrically connected to the at least one LED filament for a supply of power to the plurality of LEDs of the at least one LED filament and configured to mechanocally and electrically connect said lamp to a socket of a luminaire.

14. A LED filament lamp (600) according to claim 13, wherein the envelope comprises an amber colored layer.

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