LED filament arrangement comprising a mixing chamber

Abstract

There is provided a light emitting diode, LED, filament arrangement (100) for use in a LED filament lamp (900). The LED filament arrangement comprises at least one LED filament (115) and an elongated light-transmissive enclosure (200) enclosing the at least one LED filament and defining a mixing chamber (250) arranged to mix the LED filament light into mixed LED filament light, wherein the elongated light-transmissive enclosure has a geometric cross-section (300) comprising four side portions (320a-d). A top side portion (320a) and a bottom side portion (320b) are transflective such that at least part of the mixed LED filament light exits the top side portion, and the bottom side portion, as LED filament arrangement light (118).

Description

[0001] LED filament arrangement comprising a mixing chamber

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to a light emitting diode, LED, filament arrangement. More specifically, the present invention relates to a LED filament arrangement comprising a mixing chamber arranged to mix the LED filament light.

[0004] BACKGROUND OF THE INVENTION

[0005] The use of light emitting diodes, LEDs, 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.

[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. The visible LED filament(s) may provide a light distribution which is effective and decorative at the same time, whilst taking advantage of LED technology.

[0007] Phosphor-converted LED filaments are frequently occurring in prior art arrangements. LED filaments of this kind may provide a yellow-orange appearance, which, on the one hand, may be acceptable and / or even desirable for certain applications or installations, whereas, on the other hand, it may be desirable to provide LED filament (arrangements) which may appear white or whitish.

[0008] It is of particular interest to provide an arrangement in which LED filaments attain a vintage look, as these decor style LED filaments are very attractive. It is desired to even further improve the performance, functionality and / or appearance of LED filament lamps. More specifically, it is desirable to improve the performance and / or functionality of the light emission and / or light distribution from the LED filament lamps. Another purpose is to augment the appearance and / or the decorative aspect of the LED filaments and / or the LED filament lamps, both during operation (on-state) as well as when switched off (off-state).

[0009] US 2023 / 099125 relates to a color tunable and / or color temperature tunable LED filament. The LED filament comprises an elongated carrier having a first major surface and a second major surface arranged opposite to said first major surface, a plurality of LEDs arranged in at least one linear array on said first surface of said elongated carrier, wherein the plurality of LEDs includes LEDs of different colors and / or different color temperatures, a first elongated transparent or substantially transparent layer covering the plurality of LEDs on the first major surface and also at least partly covering said first major surface, and a first elongated light scattering layer, arranged to at least partially cover said first transparent or substantially transparent layer.

[0010] SUMMARY OF THE INVENTION

[0011] It is of interest to explore the possibility of combining one or more of the numerous advantages of LED filaments comprising LEDs, whilst improving the LED filaments’ performance and / or functionality, e.g. in terms of light distribution, light output, brightness and / or efficiency, via the properties of the light emission from, and / or features of, the LED filaments, and improving the appearance and / or the decorative aspect of the LED filaments and / or the LED filament lamps during on-state and off-state.

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

[0013] According to the present invention, there is provided a LED filament arrangement for use in a LED filament lamp, configured to provide, in an on-state, LED filament arrangement light. The LED filament arrangement comprises at least one LED filament configured to provide, during operation, LED filament light. The at least one LED filament extends along a length axis, LX, and comprises an elongated carrier, a plurality of light emitting diodes, LEDs, arranged on a first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light. The at least one LED filament further comprises an encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light. The LED filament arrangement further comprises an elongated light-transmissive enclosure enclosing the at least one LED filament and defining a mixing chamber arranged to mix the LED filament light into mixed LED filament light, wherein the elongated light-transmissive enclosure has a geometric cross-section comprising four side portions. The four side portions comprise oppositely arranged top and bottom side portions, and oppositely arranged first and second side portions, bridging the top and bottom side portions, wherein the top side portion has a first reflectivity, Ri, the bottom side portion has a second reflectivity, R2, the first side portion has a third reflectivity, R3, and the second side portion has a fourth reflectivity, R4. A normal, Ni, of the first major surface of the at least one LED filament is parallel to one of a normal, N2, of the bottom side portion, a normal, N3, of the first side portion, and a normal, N4, of the second side portion. The top side portion and the bottom side portions are transflective such that at least part of the mixed LED filament light exits the top side portion, and the bottom side portion, as LED filament arrangement light.

[0014] Thus, the present invention is based on the idea of providing a LED filament arrangement comprising (a) LED filament(s) arranged in a light-transmissive enclosure arranged to mix LED filament light into mixed LED filament light, wherein the reflectivity properties of the side portions of the enclosure, in particular the transflective top and bottom side portions, provides exit of the mixed LED filament light as LED filament arrangement light.

[0015] The present invention is advantageous in that the mixing chamber defined by the elongated light-transmissive enclosure of the LED filament arrangement improves the performance and functionality of the exiting LED filament arrangement light, as well as the appearance and the decorative aspect thereof.

[0016] It will be appreciated that (prior art) LED filament(s), which may have a yellow-orange color, may instead appear white by the construction and features of the LED filament arrangement. Hence, the LED filament arrangement may render a white appearance of the LED filament(s), optimize the hiding of the yellow-orange color of the (encapsulant of the) LED filament(s), whilst maintaining an aesthetically attractive LED filament look. In other words, the properties of the LED filament arrangement may cause the LED filament(s) to appear white or whitish when the LED filament is in an off-state, i.e. rendering the LED filament(s) white or whitish (for an observer of the LED filament arrangement). The obtained effect is a visually attractive off-state white appearance of the LED filament(s). More specifically, the LED filament arrangement may hereby attain a vintage look, and it will be appreciated that a decor style LED filament arrangement of this kind is considered very attractive. Hence, the invention is advantageous in that the LED filament arrangement is attractive for an observer, and that an improved lighting performance also may be attained.

[0017] The present invention is further advantageous in that the properties of the LED filament arrangement may be easily and conveniently customized for desired properties of the light distribution from the LED filament arrangement, as well as the aesthetic appearance of the LED filament arrangement. More specifically, properties of the elongated light- transmissive enclosure which encloses the LED filament(s), such as e.g. transmissivity, reflectivity, thickness, porosity, etc., may be set or tuned for different purposes. For example, one or more properties of the LED filament arrangement may be advantageously set in order to render a white appearance of the LED filament(s), optimize the hiding of the yellow- orange color of the encapsulant whilst maintaining an aesthetically attractive LED filament look, etc.

[0018] The present invention is further advantageous in that the numerous advantages of using LED technology may be combined with the attractiveness and the appealing properties of the LED filament arrangement as disclosed.

[0019] The present invention is further advantageous in that the LED filament arrangement of the present invention comprises relatively few components. The low number of components is advantageous in that the LED filament arrangement is relatively inexpensive to fabricate. Moreover, the low number of components of the LED filament arrangement implies an easier recycling, especially compared to devices or arrangements comprising a relatively high number of components which impede an easy disassembling and / or recycling operation.

[0020] According to the present invention, there is provided a LED filament arrangement for use in a LED filament lamp, configured to provide, in an on-state, LED filament arrangement light. In embodiments, the LED filament arrangement light may be white light having a correlated color temperature, CCT, in a range from 2000 to 6500 K, and preferably a color rendering index, CRI, of at least 80, or at least 85. The at least one LED filament extends along a length axis, LX. Preferably, each LED filament has a length, LF, and a width, WF, wherein LF > 5WF or even LF > 10WF. The LED filament(s) 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 has a light-emitting surface that extends along the length, and preferably at least partly around the axis of elongation. The light-emitting surface is preferably arranged to homogenously emit light and / or to emit light omnidirectionally. The at least one LED filament comprises an elongated carrier, and a plurality of light emitting diodes, LEDs, arranged on a first major surface of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light. The elongated carrier may, for instance, be a substrate, that 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 elongated carrier may be reflective or light transmissive, such as translucent and preferably transparent. The plurality of LEDs may be arranged on the first major surface of the elongated carrier in a linear array. By the term “array”, it is here meant a linear arrangement or chain of LEDs, or the like. The at least one LED filament further comprises an encapsulant at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light. By the term “encapsulant”, it is here meant an (elongated) material, element, arrangement, or the like, which in the present context is configured or arranged to at least partially cover, surround, encapsulate and / or enclose the first major surface of the elongated carrier and the plurality of LEDs. The encapsulant may be a polymer material which may be flexible such as for example a silicone. The luminescent material of the encapsulant may be a phosphor such as an inorganic phosphor and / or quantum dots or rods. The LED filament arrangement further comprises an elongated light-transmissive enclosure enclosing the at least one LED filament and defining a mixing chamber arranged to mix the LED filament light into mixed LED filament light, wherein the elongated light-transmissive enclosure has a geometric crosssection comprising four side portions. By “mixing chamber”, it is here meant that the reflectivity properties of the elongated light-transmissive enclosure, defining the mixing chamber, provides the possibility for the light from the LED filament(s) to reflect and to mix before transmission through (via) the elongated light-transmissive enclosure as LED filament light. The cross-section of the elongated light-transmissive enclosure may be quadrilateral, e.g. rectangular or quadratic. The four side portions comprise oppositely arranged top and bottom side portions, and oppositely arranged first and second side portions, bridging the top and bottom side portions, wherein the top side portion has a first reflectivity, Ri, the bottom side portion has a second reflectivity, R2, the first side portion has a third reflectivity, R3, and the second side portion has a fourth reflectivity, R4. Hence, the four side portions of the elongated light-transmissive enclosure have a respective reflectivity, R1-R4. A normal, Ni, of the first major surface of the at least one LED filament is parallel to one of a normal, N2, of the bottom side portion, a normal, N3, of the first side portion, and a normal, N4, of the second side portion. Hence, the normal, Ni, of the first major surface is parallel to the normal, N2, of the bottom side portion, the normal, N3, of the first side portion, or the normal, N4, of the second side portion. The top side portion and the bottom side portions are transflective such that at least part of the mixed LED filament light exits the top side portion, and the bottom side portion, as LED filament arrangement light. By “transflective”, it is here meant both reflective and transmissive, i.e. that the top and bottom side portions are configured to reflect and transmit the mixed LED filament light.

[0021] According to an embodiment of the present invention, the at least one LED filament may be arranged on an inner surface of one of the bottom side portion, the first side portion, and the second side portion. Hence, the LED filament(s) may be arranged on the inner surface of the bottom side portion, the first side portion, or the second side portion. The present embodiment is advantageous in that the position of the LED filament(s) with respect to the reflectivity properties of the side portions of the enclosure, in particular the transflective top and bottom side portions, may provide an even further improved emission of LED filament arrangement light from the LED filament arrangement and / or an even further improved LED filament arrangement concerning its aesthetic appearance.

[0022] According to an embodiment of the present invention, the at least one LED filament may not be in direct physical contact with any inner surface of the top side portion, the bottom side portion, the first side portion, and the second side portion. Hence, the LED filament(s) may be arranged or mounted in the LED filament arrangement such that the LED filament(s) is (are) not arranged on (abutting) any inner surface of the side portions, i.e., that the LED filament(s) do(es) not touch any of the side portions. The present embodiment is advantageous in that an even further improved light distribution may be provided by the lighting arrangement.

[0023] According to an embodiment of the present invention, Ri < R2. Hence, the second reflectivity, R2, of the bottom side portion may be higher (larger) than the first reflectivity, Ri, of the top side portion. For example, the first reflectivity, Ri, may be in a range of 10 - 25 %, preferably in a range of 12 - 25 %. According to an exemplifying embodiment, it is preferred that Ri < R2 - 10 %, and even more preferred, Ri < R2 - 20 %. The present embodiment is advantageous in that the relatively smaller first reflectivity, Ri, of the top side portion compared to the second reflectivity, R2, of the bottom side portion contributes to the creation of a similar or the same spatial light distribution as a normal LED filament.

[0024] According to an embodiment of the present invention, at least one of R2 < R3 and R2 < R4, may be fulfilled. Hence, the second reflectivity, R2, of the bottom side portion may be smaller than the third reflectivity, R3, of the first side portion and / or the second reflectivity, R2, of the bottom side portion may be smaller than the fourth reflectivity, R4, of the second side portion. According to an exemplifying embodiment, it is preferred that R2 < R3 - 10 %, and even more preferred, R2 < R3 - 20 % and / or that R2 < R4 - 10 %, and even more preferred, R2 < R4 - 20 %. The present embodiment is advantageous in that these reflectivity relations, whereby the third reflectivity, R3, of the first side portion and / or the fourth reflectivity, R4, of the second side portion may be relatively high with respect to the second reflectivity, R2, of the bottom side portion, may provide a customized and / or desirable directional LED filament arrangement light.

[0025] According to an embodiment of the present invention, max (Ri, R2) < min (R3, R4). Hence, the smaller of the third reflectivity, R3, of the first side portion and the fourth reflectivity, R4, of the second side portion may (still) be larger than the larger of the first reflectivity, Ri, of the top side portion and the second reflectivity, R2, of the bottom side portion. According to an exemplifying embodiment, it is preferred that max (Ri, R2) < min (R3, R4) - 10 %, and even more preferred that max (Ri, R2) < min (R3, R4) - 20 %. The present embodiment is advantageous in that these reflectivity relations, whereby the third reflectivity, R3, of the first side portion and the fourth reflectivity, R4, of the second side portion may be relatively high with respect to the first reflectivity, Ri, of the top side portion and the second reflectivity, R2, of the bottom side portion, an even further customized and / or desirable directional LED filament arrangement light may be provided.

[0026] According to an embodiment of the present invention, the top side portion has a first thermal conductivity, Ki, the bottom side portion has a second thermal conductivity, K2, the first side portion has a third thermal conductivity, K3, and the second side portion has a fourth thermal conductivity, K4, wherein max (Ki, K2) < min (K3, K4). Hence, the four side portions of the elongated light-transmissive enclosure have a respective thermal conductivity, K1-K4, whereby the smaller of the third thermal conductivity, K3, of the first side portion and the fourth thermal conductivity, K4, of the second side portion may (still) be larger than the larger of the first thermal conductivity, Ki, of the top side portion and the second thermal conductivity, K2, of the bottom side portion. For example, the top side portion and / or the bottom side portion may comprise metal (e.g. one or more metal strips), having a relatively high thermal conductivity. The present embodiment is advantageous in that the thermal conductivity properties of the side portions of the elongated light-transmissive enclosure provide an efficient thermal management of the plurality of LEDs of the LED filament(s). More specifically, the LED filament arrangement hereby provides an improved cooling of the plurality of LEDs of the LED filament(s) during operation. Additionally, and consequently, the plurality of LEDs may hereby be operated (driven) at a higher current compared to an arrangement without these properties. Hence, the present embodiment provides an increased service life of the LED filament arrangement via its thermal management and / or achieves an even further improved light distribution and / or appearance of the LED filament arrangement.

[0027] According to an exemplifying embodiment, it is preferred that max (Ki, K2) < 0.5-min (K3, K4). By this significant difference between the thermal conductivities, i.e. that the top and bottom side portions have (very) low thermal conductivities, Ki, K2, whereas the first and second side portions have (very) high thermal conductivities, K3, K4, an even more efficient thermal management of the plurality of LEDs of the LED filament(s) may be achieved by the heat dissipation provided by the first and second side portions.

[0028] According to an embodiment of the present invention, the at least one LED filament may be arranged on an inner surface of one of the first side portion and the second side portion, and wherein the LED filament arrangement may further comprise an optical element arranged on one of the first side portion and the second side portion opposite the side portion on which inner surface the at least one LED filament is arranged. The optical element is configured to redirect LED filament light incident on the optical element to at least one of the top side portion and the bottom side portion. Hence, the LED filament(s) is arranged on an inner surface of the first side portion or second side portion, and wherein the LED filament arrangement further comprises an optical element arranged on the first side portion or the second side portion opposite the side portion on which inner surface the LED filament(s) is arranged, wherein the optical element is configured to redirect LED filament light incident on the optical element to the top side portion and / or the bottom side portion. The present embodiment is advantageous in that the optical element may conveniently direct the (mixed) LED filament light towards the top side portion and / or the bottom side portion for exiting the LED filament arrangement therethrough, resulting in an even further customized and / or desirable emission of the LED filament arrangement light from the LED filament arrangement.

[0029] According to an embodiment of the present invention, the at least one LED filament may be arranged on one of the first side portion and the second side portion, and wherein at least one of the top side portion and the bottom side portion tapers with respect to one of the normal, Ns, of the first side portion and the normal, N4, of the second side portion of which side portion the at least one LED filament is arranged on. Hence, the LED filament(s) may be arranged on the first side portion or the second side portion, and wherein the top side portion and / or the bottom side portion tapers with respect to the normal, Ns, of the first side portion or the normal, N4, of the second side portion of which side portion the LED filament(s) is arranged on. The present embodiment is advantageous in that the outcoupling of the (mixed) LED filament light from the LED filament arrangement is even further improved.

[0030] According to an embodiment of the present invention, the LED filament arrangement may further comprise an anode electrical contact arranged at a first end portion of the at least one LED filament and at a first end portion of the elongated light-transmissive enclosure, and a cathode electrical contact arranged at a second end portion of the at least one LED filament, opposite the first end portion and at a second end portion of the elongated light-transmissive enclosure. The present embodiment is advantageous in that the arrangement of the anode and cathode electrical contacts of the LED filament(s), via its easy mechanical fixation, achieves a convenient and efficient supply of power to the plurality of LEDs of the LED filament(s) of the LED filament arrangement.

[0031] According to an embodiment of the present invention, the mixing chamber may comprise at least one partition element partitioning the mixing chamber into a plurality of mixing chamber segments. Each mixing chamber segment of the plurality of mixing chamber segments comprises at least one LED of the plurality of LEDs, and wherein at least one of at least one of the at least one partition element extends perpendicular to the length axis, LX. At least two mixing chamber segments of the plurality of mixing chamber segments are arranged in an array extending parallel to the length axis, LX, and at least one of the at least one partition element extends parallel to the length axis, LX, whereby at least two mixing chamber segments of the plurality of mixing chamber segments extend parallel to the length axis, LX, is fulfilled. Hence, the mixing chamber may comprise one or more partition elements partitioning the mixing chamber into a plurality of mixing chamber segments, wherein each mixing chamber segment of the plurality of mixing chamber segments comprises at least one LED of the plurality of LEDs. Furthermore, the partition element(s) extends perpendicular to the length axis, LX, whereby at least two mixing chamber segments of the plurality of mixing chamber segments are arranged in an array extending parallel to the length axis, LX, and / or the partition element(s) extends parallel to the length axis, LX, whereby at least two mixing chamber segments of the plurality of mixing chamber segments extend parallel to the length axis, LX. The present embodiment is advantageous in that particularly decorative light effects of the LED filament arrangement light may be obtained.

[0032] According to an embodiment of the present invention, the at least one LED of the plurality of LEDs comprised in any mixing chamber segment of the plurality of mixing chamber segments may be configured to emit light with one of a correlated color temperature, CCT, and a color point, being different from a corresponding one of a correlated color temperature, CCT, and a color point, of the light configured to be emitted by the at least one LED of the plurality of LEDs comprised in any other mixing chamber segment of the plurality of mixing chamber segments. Hence, the LED(s) comprised in any mixing chamber may be configured to emit light with a correlated color temperature, CCT, or a color point, being different from a corresponding correlated color temperature, CCT, or color point, of the light configured to be emitted by the LED(s) comprised in any other mixing chamber segment. The present embodiment is advantageous in that the decorative and / or aesthetical effect(s) of the LED filament arrangement and / or the lighting thereof may be augmented even further by the different correlated color temperatures, CCT, and / or color points.

[0033] According to an embodiment of the present invention, the LED filament arrangement may further comprise at least one mixing chamber segment shielding arranged to shield at least one mixing chamber segment of the plurality of mixing chamber segments, wherein the at least one mixing chamber segment shielding has a fifth reflectivity, Rs, wherein Rs > max (Ri, R2). Hence, the LED filament arrangement may further comprise one or more mixing chamber segment shieldings arranged to shield one or more mixing chamber segments, wherein the (fifth) reflectivity, Rs, of the shielding(s) is larger than the largest of the first reflectivity, Ri, of the top side portion and the second reflectivity, R2, of the bottom side portion. The present embodiment is advantageous in that the shielding of the mixing chamber(s) may provide an even more advantageous lighting distribution and / or decorative effect of the LED lighting arrangement.

[0034] According to an example of the present invention, the encapsulant may comprise a light scattering material configured to at least partially diffusely transmit and at least partially diffusely reflect the LED filament light. Hence, the light scattering material of the encapsulant may be configured or arranged to at least partially diffusely transmit and diffusely reflect the LED filament light. By “diffusely transmit”, it is here meant that the light scattering material is configured to transmit the LED filament light whilst providing diffusion of the LED filament light upon transmission. By “diffusely reflect”, it is here meant that the light scattering material is configured to reflect the LED filament light whilst providing diffusion of the LED filament light upon reflection. The present example is advantageous in that the diffusive property of the encapsulant may achieve an omnidirectional, or at least almost omnidirectional, light distribution via the diffusive transmission and reflection. The present example is further advantageous in that the encapsulant’s reflectivity may even further enhance the effect of masking or hiding a yellow-orange color of the LED filament(s).

[0035] According to an example of the present invention, the elongated carrier may be light transmissive, wherein the encapsulant may at least partially cover a second major surface, opposite the first major surface, of the elongated carrier. The present example is advantageous in that the light transmissive elongated carrier may achieve an (almost) omnidirectional light distribution of the LED filament. The present example is further advantageous in that the encapsulant may influence the light transmitted via the second major surface, due to the light transmissive property of the elongated carrier, thereby even further enhancing the aesthetical appearance of the LED filament arrangement during operation.

[0036] According to an embodiment of the present invention, there is provided a LED filament device. The LED filament device comprises a LED filament arrangement according to any one of the preceding embodiments, and a controller coupled to the at least one LED filament. The controller, in case the LED filament comprises a single LED filament, is configured to individually control the LEDs of the LED filament, and wherein the controller, in case of the LED filament comprises a plurality of LED filaments, is configured to individually control each LED filament. By “controller”, it is here meant any device, unit, or the like, which is able to control the luminous flux either by wire or via wireless technology. The present embodiment is advantageous in that the controller may conveniently and efficiently control the LEDs of the (single) LED filament or each LED filament of the plurality of LED filaments, thereby even further ameliorating the light emission from the LED filaments and improving the appearance and / or the decorative aspect of the LED filaments.

[0037] According to an embodiment of the present invention, there is provided a LED filament lamp comprising one of at least one LED filament arrangement according to any one of the previous embodiments and a LED filament device of the previous embodiment. The LED filament lamp further comprises a light-transmissive envelope at least partly enclosing the LED filament arrangement, and a connector for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire. Hence, the LED filament lamp comprises one or more LED filament arrangements, or a LED filament device which in turn comprises a LED filament arrangement. The present embodiment is advantageous in that the LED filament lamp, comprising the LED filaments, combines the aspects of a desired light emission and aesthetical appearance provided via the LED filament arrangement and / or via the feature(s) of the lamp.

[0038] 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.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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.

[0041] Fig. 1 shows a LED filament lamp according to the prior art,

[0042] Figs. 2a and 2g schematically show LED filament arrangements according to exemplifying embodiments of the present invention,

[0043] Figs. 2b-2f and Fig. 2h schematically show cross-sections of a LED filament arrangement according to exemplifying embodiments of the present invention, and

[0044] Fig. 3 shows a LED filament lamp comprising a LED filament arrangement according to an exemplifying embodiment of the present invention.

[0045] DETAILED DESCRIPTION

[0046] 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. However, it is of interest to improve the properties of the light distribution emitted from the LED filaments 20, and to even further augment the decorative appearance and / or aspect of the LED filaments 20 and / or the LED filament lamps 10.

[0047] Fig. 2a schematically shows a LED filament arrangement 100 according to an exemplifying embodiment of the present invention. The LED filament arrangement 100 is intended for use in a LED filament lamp, and is configured to provide, in an on-state, LED filament arrangement light 110. The LED filament arrangement light 110 may, for example, be white light having a correlated color temperature, CCT, in a range from 2000 to 6500 K, and preferably a color rendering index, CRI, of at least 80, or at least 85. The LED filament arrangement 100 comprises at least one LED filament 115 extending along a length axis, LX. In Fig. 2a, the LED filament arrangement 100 is exemplified as having a single (i.e. one) LED filament 115, but it should be noted that the number of LED filaments 115 is substantially arbitrary.

[0048] Preferably, the (each) LED filament 115 has a length, LF (not indicated) and a width, WF (not indicated), wherein LF > 5WF or even LF > 10WF. The width, WF, and / or the height, HF, of the LED filament 115 may be in a range of 1-3 mm. The LED filament(s) 115 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 115 has a lightemitting surface that extends along the length, and preferably at least partly around the axis of elongation. The light-emitting surface is preferably arranged to homogenously emit light and / or to emit light omnidirectionally. The at least one LED filament 115 comprises an elongated carrier 120, and a plurality of light emitting diodes, LEDs 130, arranged on a first major surface 145 of the elongated carrier 120, wherein the plurality of LEDs 130 is configured to emit LED light 150. It should be noted that the LED filament 115 may comprise substantially any number of array(s) of the plurality of LEDs 130. The plurality of LEDs 130 preferably comprises more than 5 LEDs, more preferably more than 8 LEDs, and even more preferred more than 10 LEDs. The plurality of LEDs 130 may be direct emitting LEDs which provide a color. The elongated carrier 120 may, for instance, be a substrate, that 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 elongated carrier 120 may be reflective or light transmissive, such as translucent and preferably transparent.

[0049] The LED filament 115 further comprises an encapsulant 160 which at least partially covers the first major surface 145 of the elongated carrier 120 and at least partially encloses the plurality of LEDs 130. The encapsulant 160 comprises a luminescent material configured to at least partly convert the emitted LED light 150 into converted light 170. The luminescent material of the encapsulant 160 may be a light-scattering material, e.g. a polymer matrix comprising BaSCL, AI2O3 and / or TiCh particles. The luminescent material of the encapsulant 160 may be a phosphor such as an inorganic phosphor (e.g. YAG, LuAG, ECAS, KSiF, etc.) and / or quantum dots or rods. The phosphor may further be e.g. a (blue) green / yellow and / or red phosphor. Although not shown, a concentration of the luminescent material in the encapsulant 160 may vary over the length of the LED filament 115. The LED filament arrangement 100 further comprises an elongated light-transmissive enclosure 200 enclosing the LED filament 115 and defining a mixing chamber arranged to mix the LED filament light into mixed LED filament light.

[0050] The LED filament arrangement 100 comprises an anode electrical contact 500 arranged at a first end portion 510 of the LED filament 115 and at a first end portion 520 of the elongated light-transmissive enclosure 200. The LED filament arrangement 100 further comprises a cathode electrical contact 600 arranged at a second end portion 610 of the LED filament 115, opposite the first end portion 510, and at a second end portion 620 of the elongated light-transmissive enclosure 200.

[0051] Figs. 2b-2f and Fig. 2h schematically show cross-sections of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100 according to exemplifying embodiments of the present invention. It is referred to Fig. 1 and the associated text for an increased understanding of the features and / or functions of the LED filament arrangement 100. Furthermore, it should be noted that some references present in Fig. 1 are absent in Figs. 2b-2f and Fig. 2h for reasons of visibility.

[0052] Fig. 2b schematically shows a cross-section of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100, perpendicular to the length axis, LX, of the LED filament 115 thereof. The elongated light-transmissive enclosure 200 of the LED filament arrangement 100 encloses the LED filament 115 and defines a mixing chamber 250 arranged to mix the LED filament light 118 into mixed LED filament light. The elongated light-transmissive enclosure 200 has a geometric cross-section 300 comprising four side portions 320a-d. The four side portions 320a-d comprise oppositely arranged top 320a and bottom 320b side portions, and oppositely arranged first 320c and second 320d side portions, bridging the top 320a and bottom 320b side portions. The top side portion 320a has a first reflectivity, Ri, the bottom side portion 320b has a second reflectivity, R2, the first side portion 320c has a third reflectivity, R3, and the second side portion 320d has a fourth reflectivity, R4. In the example of Fig. 2b, the cross-section 300 of the elongated light- transmissive enclosure 200 is rectangular, but is should be noted that the cross-section 300 alternatively may have any quadrilateral form (e.g. quadratic). In Fig. 2b, the LED filament 115 is arranged on an inner surface of the bottom side portion 320b of the elongated light- transmissive enclosure 200. A normal, Ni, of the first major surface of the LED filament 115 is parallel to a normal, N2, of the bottom side portion 320b (and consequently, perpendicular to a normal, N3, of the first side portion 320c, and perpendicular to a normal, N4, of the second side portion 320d. The top side portion 320a and the bottom side portion 320b are transflective (i.e. both reflective and transmissive) such that at least part of the mixed LED filament light exits the top side portion 320a and the bottom side portion 320b as LED filament arrangement light. According to this example of the LED filament arrangement 100, the second reflectivity, R2, of the bottom side portion 320b is higher than the first reflectivity, Ri, of the top side portion 320a, i.e. R2 > Ri, which is schematically indicated by the arrows indicating a (larger) transmission of mixed LED filament light through the top side portion 320a compared to a (smaller) transmission of mixed LED filament light through the bottom side portion 320b. For example, the portion of the mixed LED filament light transmitted through the top side portion 320a may be in the range of 60% -80%, such as approximately 70 %, whereas the portion of the mixed LED filament light transmitted through the bottom side portion 320b may be in the range of 20% -40%, such as approximately 30 %.

[0053] Fig. 2c schematically shows a cross-section of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100, perpendicular to the length axis, LX, of the LED filament 115 thereof. Analogously with Fig. 2b, the elongated light-transmissive enclosure 200 in Fig. 2c has a geometric cross-section 300 comprising four side portions 320a-d. The four side portions 320a-d comprise oppositely arranged top 320a and bottom 320b side portions, and oppositely arranged first 320c and second 320d side portions, bridging the top 320a and bottom 320b side portions. The LED filament 115 is arranged on an inner surface of the first side portion 320c of the elongated light-transmissive enclosure 200. According to this example of the LED filament arrangement 100, the smaller of the third reflectivity, R3, of the first side portion 430c and the fourth reflectivity, R4, of the second side portion 320b may (still) be larger than the larger of the first reflectivity, Ri, of the top side portion 320a and the second reflectivity, R2, of the bottom side portion 320b, i.e. max (Ri, R2) < min (R3, R4). Furthermore, the four side portions 320a-d of the elongated light- transmissive enclosure 200 may have a respective thermal conductivity, K1-K4, whereby the smaller of the third thermal conductivity, K3, of the first side portion 320c and the fourth thermal conductivity, K4, of the second side portion 320d may (still) be larger than the larger of the first thermal conductivity, Ki, of the top side portion 320a and the second thermal conductivity, K2, of the bottom side portion 320b, i.e. max (Ki, K2) < min (K3, K4).

[0054] Fig. 2d schematically shows a cross-section of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100, perpendicular to the length axis, LX, of the LED filament 115 thereof. The LED filament 115 is arranged on an inner surface of the first side portion 320c of the elongated light-transmissive enclosure 200. The LED filament arrangement 100 comprises an optical element 400 arranged on the second side portion 320d opposite the first side portion 320c. The optical element 400, which in Fig. 2d is exemplified as having a triangular (wedge) shape, is configured to redirect LED filament light incident on the optical element 400 to the top side portion 320a and / or the bottom side portion 320b.

[0055] Fig. 2e schematically shows a cross-section of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100, perpendicular to the length axis, LX, of the LED filament 115 thereof. The LED filament 115 is arranged on an inner surface of the first side portion 320c of the elongated light-transmissive enclosure 200. The top side portion 320a and the bottom side portion 320b taper with respect to the normal, N3, of the first side portion 320c upon which the LED filament 115 is arranged.

[0056] Fig. 2f schematically shows a cross-section of an elongated light-transmissive enclosure 200 of a LED filament arrangement 100, perpendicular to the length axis, LX, of the LED filament 115 thereof. The elongated light-transmissive enclosure 200 has a geometric cross-section 300, which in this case is rectangular, comprising four side portions 320a-d. The LED filament 115 is arranged at a central portion of the elongated light- transmissive enclosure 200, whereby the LED filament 115 is not in direct physical contact with any inner surface of the top side portion 320a, the bottom side portion 320b, the first side portion 320c, and the second side portion 320d.

[0057] Figs. 2g and 2h schematically show LED filament arrangements 100 according to exemplifying embodiments of the present invention. The mixing chamber of the elongated light-transmissive enclosure 200 of the LED filament arrangement 100 comprises a plurality of partition elements 700a, b. The plurality of partition elements 700a, b partition the mixing chamber into a plurality of mixing chamber segments 255, wherein each mixing chamber segment of the plurality of mixing chamber segments 255 comprises at least one LED of the plurality of LEDs.

[0058] According to the example of Fig. 2g, the plurality of partition elements 700a extends perpendicular to the length axis, LX, of the LED filament 115, whereby at least two mixing chamber segments 255a-m of the plurality of mixing chamber segments 255 are arranged in an array extending parallel to the length axis, LX.

[0059] According to the example of Fig. 2h, showing the LED filament arrangement 100 in cross-section in accordance with Figs. 2a-f, a (first) LED filament 115a is arranged on an inner surface of the first side portion 320c and a (second) LED filament 115b is arranged on an inner surface of the second side portion 320d of the elongated light-transmissive enclosure 200. At least one partition element 700b extends parallel to the length axis, LX, of the LED filament 115, whereby at least two mixing chamber segments 255n,o extend parallel to the length axis, LX. In the example of the LED filament arrangement 100 of Fig. 2h, the LED(s) of the plurality of LEDs of the LED filament 115a comprised in mixing chamber segment 255n is configured to emit light with a correlated color temperature, CCT, or a color point, being different from a corresponding correlated color temperature, CCT, or a color point, of the light configured to be emitted by the LED(s) of the plurality of LEDs of LED filament 115b comprised in mixing chamber segment 255o. The LED filament arrangement 100 may further comprise, according to an example, at least one mixing chamber segment shielding arranged to shield at least one mixing chamber segment of the plurality of mixing chamber segments 255. The at least one mixing chamber segment shielding has a fifth reflectivity, Rs, wherein the fifth reflectivity, Rs, is larger than the largest of the first reflectivity, Ri, of the top side portion 320a and the second reflectivity, R2, of the bottom side portion 320b, i.e. Rs > max (Ri, R2).

[0060] Fig. 3 schematically shows a LED filament lamp 900 according to an embodiment of the present invention. The LED filament lamp 900, which may constitute substantially any kind of lamp or luminaire, comprises one or more LED filament arrangements 100 according to any one of the previously described embodiments. The LED filament lamp 900 further comprises a light-transmissive envelope 910, which is exemplified as being bulb-shaped. The light-transmissive envelope 910 at least partially encloses the LED filament arrangement(s) 100. The LED filament lamp 900 further comprises a connector 920 for electrically and mechanically connecting the LED filament lamp 900 to a socket of a luminaire. The LED filament lamp 900 may further comprise a controller 810 coupled to the LED filament(s) of the LED filament arrangement(s) 100. The controller 810 is configured to control the luminous flux of the LED filament light. The controller 810 is schematically indicated by a dashed rectangle in the connector 920, but it should be noted that the controller 810 may be arranged at substantially any position or place. In case the LED filament arrangement(s) 100 comprise(s) a single LED filament, the controller 810 may be configured to control the LEDs of the single LED filament. In case the LED filament arrangement(s) 100 comprise(s) a plurality of LED filaments, the controller 810 may be able to individually control each LED filament of the LED filament arrangement 100.

[0061] 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 arrangement 100, the LED filament(s) 115, the elongated light- transmissive enclosure 200, etc., may have different shapes, dimensions and / or sizes than those depicted / described.

Claims

CLAIMS:

1. A light emitting diode, LED, filament arrangement (100) for use in a LED filament lamp (900), configured to provide, in an on-state, LED filament arrangement light (110), the LED filament arrangement comprising at least one LED filament (115) configured to provide, during operation, LED filament light (118), wherein the at least one LED filament extends along a length axis, LX, and comprises an elongated carrier (120), a plurality of light emitting diodes, LEDs (130) arranged on a first major surface (145) of the elongated carrier, wherein the plurality of LEDs is configured to emit LED light (150), an encapsulant (160) at least partially covering the first major surface of the elongated carrier and at least partially enclosing the plurality of LEDs, wherein the encapsulant comprises luminescent material configured to at least partly convert the emitted LED light into converted light (170), an elongated light-transmissive enclosure (200) enclosing the at least one LED filament and defining a mixing chamber (250) arranged to mix the LED filament light into mixed LED filament light, wherein the elongated light-transmissive enclosure has a geometric cross-section (300) comprising four side portions (320a-d) comprising oppositely arranged top (320a) and bottom (320b) side portions, and oppositely arranged first (320c) and second (320d) side portions, bridging the top and bottom side portions, wherein the top side portion has a first reflectivity, Ri, the bottom side portion has a second reflectivity, R2, the first side portion has a third reflectivity, R3, and the second side portion has a fourth reflectivity, R4, wherein a normal, Ni, of the first major surface of the at least one LED filament is parallel to one of a normal, N2, of the bottom side portion, a normal, N3, of the first side portion, and a normal, N4, of the second side portion,wherein the top side portion and the bottom side portions are transflective such that at least part of the mixed LED filament light exits the top side portion, and the bottom side portion, as LED filament arrangement light., and, wherein the at least one LED filament is arranged on an inner surface of one of the first side portion and the second side portion.

2. The LED filament arrangement according to claim 1, wherein the LED filament arrangement further comprises an optical element (400) arranged on one of the first side portion and the second side portion opposite the side portion on which inner surface the at least one LED filament is arranged, wherein the optical element is configured to redirect LED filament light incident on the optical element to at least one of the top side portion and the bottom side portion.

3. The LED filament arrangement according to claim 1, wherein the at least one LED filament is not in direct physical contact with any inner surface of the top side portion, the bottom side portion, the first side portion, and the second side portion.

4. The LED filament arrangement according to any one of the preceding claims, wherein Ri < R2.

5. The LED filament arrangement according to any one of the preceding claims, wherein at least one ofR.2 < R3 andR2 < R.4, is fulfilled.

6. The LED filament arrangement according to any one of the preceding claims, wherein max (Ri, R2) < min (R3, R4).

7. The LED filament arrangement according to any one of the preceding claims, wherein the top side portion has a first thermal conductivity, Ki,the bottom side portion has a second thermal conductivity, K2, the first side portion has a third thermal conductivity, K3, and the second side portion has a fourth thermal conductivity, K4, wherein max (Ki, K2) < min (K3, K4).

8. The LED filament arrangement according to any one of claims 1-2 and 4-7, wherein the at least one LED filament is arranged on one of the first side portion and the second side portion, and wherein at least one of the top side portion and the bottom side portion tapers with respect to one of the normal, N3, of the first side portion and the normal, N4, of the second side portion of which side portion the at least one LED filament is arranged on.

9. The LED filament arrangement according to any one of the preceding claims, further comprising an anode electrical contact (500) arranged at a first end portion (510) of the at least one LED filament and at a first end portion (520) of the elongated light-transmissive enclosure, and a cathode electrical contact (600) arranged at a second end portion (610) of the at least one LED filament, opposite the first end portion and at a second end portion (620) of the elongated light-transmissive enclosure.

10. The LED filament arrangement according to any one of the preceding claims, wherein the mixing chamber comprises at least one partition element (700a, b) partitioning the mixing chamber into a plurality of mixing chamber segments (255), wherein each mixing chamber segment of the plurality of mixing chamber segments comprises at least one LED of the plurality of LEDs, and wherein at least one of at least one (700a) of the at least one partition element extends perpendicular to the length axis, LX, whereby at least two mixing chamber segments (255a-m) of the plurality of mixing chamber segments are arranged in an array extending parallel to the length axis, LX, and at least one (700b) of the at least one partition element extends parallel to the length axis, LX, whereby at least two mixing chamber segments (255n,o) of the plurality of mixing chamber segments extend parallel to the length axis, LX, is fulfilled.

11. The LED filament arrangement according to claim 10, wherein the at least one LED of the plurality of LEDs comprised in any mixing chamber segment of the plurality of mixing chamber segments is configured to emit light with one of a correlated color temperature, CCT, and a color point, being different from a corresponding one of a correlated color temperature, CCT, and a color point, of the light configured to be emitted by the at least one LED of the plurality of LEDs comprised in any other mixing chamber segment of the plurality of mixing chamber segments.

12. The LED filament arrangement according to claim 4, and claim 10 or 11, further comprising at least one mixing chamber segment shielding arranged to shield at least one mixing chamber segment of the plurality of mixing chamber segments, wherein the at least one mixing chamber segment shielding has a fifth reflectivity, Rs, wherein Rs > max (Ri, R2).

13. A LED filament device (800), comprising a LED filament arrangement according to any one of the preceding claims, and a controller (810) coupled to the at least one LED filament, wherein the controller, in case the LED filament arrangement comprises a single LED filament, is configured to individually control the LEDs of the LED filament, and wherein the controller, in case of the LED filament comprises a plurality of LED filaments, is configured to individually control each LED filament.

14. A LED filament lamp (900), comprising one of at least one LED filament arrangement according to any one of claim 1- 12, and a LED filament device according to claim 13, a light-transmissive envelope (910) at least partly enclosing the LED filament arrangement, and a connector (920) for electrically and mechanically connecting the LED filament lamp to a socket of a luminaire.

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