LED filament lamp

Abstract

A LED filament lamp comprises a plurality of M first LED filaments arranged parallel with each other along a circular first path having a first diameter, D1, and a plurality of O second LED filaments arranged parallel with each other along a circular second path having a second diameter, D2, inside the first path. Each first LED filament is spaced apart from neighboring first LED filaments by a first gap having a first spacing distance, S1. Each second LED filament is spaced apart from neighboring second LED filaments by a second gap having a second spacing distance, S2. A light-transmissive envelope at least partly encloses the plurality of LED filaments, and D2<D1 and S2<S1 and M≥O.

Description

[0001] LED filament lamp

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to light emitting devices. More specifically, the present invention is related to a light emitting diode (LED) filament lamp comprising a plurality of elongated LED filaments inside a light-transmissive envelope.

[0004] BACKGROUND OF THE INVENTION LED light source technology has developed during the last decades to a point where, in terms of luminous output, LED-based light sources can replace older technology light sources within almost all fields of application, even in fields requiring very high luminous flux combined with very high luminance. For example, in the field of high-pressure sodium (HPS) lamps having efficacies of 100 lumens per watt or more, it is now possible to replace HPS lamps such as Philips SON-T lamps with lamps comprising LED light sources in the form of LED filaments. A luminous flux of more than 10000 Im out of a small tubular source with rotationally symmetrical intensity distribution is also important for light sources that are to be used in existing road lighting luminaires that were designed for HPS lamps.

[0005] However, there still remain various aspects of such light sources using LED filaments. For example, there is still a need for improving the performance and / or the appearance of light sources using LED filaments.

[0006] CN 205447330 U discloses a LED light source module reaches LED filament lamp including it, LED light source module includes the luminous strip of metallic interconnect frame and two piece at least LED, the luminous strip of LED is parallel interval arranged each other, the both ends of the every luminous strip of LED are fixed in respectively on two metallic interconnect frames, LED filament lamp includes driver.

[0007] SUMMARY OF THE INVENTION

[0008] It is of interest to provide a LED filament lamp that is capable of overcoming drawbacks of prior art devices. This and other objects are achieved in a first aspect by providing a LED filament lamp having the features of the appended independent claim. Preferred embodiments are defined in the appended dependent claims.

[0009] Hence, according to the present invention there is provided a LED filament lamp providing LED filament lamp light. The LED filament lamp light may be white light having a correlated color temperature in a range from 1700 K to 6500 K, and may have a color rendering index (CRI) of at least 80 or at least 85. The LED filament lamp comprises a plurality of N LED filaments. Each LED filament of the plurality of N LED filaments comprises an array of a plurality of LEDs arranged on or in an elongated carrier having an elongation direction. A light-transmissive envelope at least partly encloses the plurality of LED filaments.

[0010] The array may be in the form of LEDs arranged along one or more lines on or in the carrier. The light-transmissive envelope may be elongated and (its longitudinal axis) may be aligned with the elongated carriers.

[0011] A connector is configured to provide electric connection between a power source and the plurality of N LED filaments, and preferably also a mechanical connection between a power source and the LED filament lamp 1.

[0012] The plurality of N LED filaments comprises a plurality of M first LED filaments configured to provide, in operation, first LED filament light. The plurality of M first LED filaments are arranged parallel with each other along a circular first path having a first diameter, DI. The first path is in a plane perpendicular to the elongation direction and each first LED filament is spaced apart from neighboring first LED filaments by a first gap having a first spacing distance, SI.

[0013] As the skilled person will realize, considering manufacturing tolerances, the spacing distance SI and any other spacing distance defined herein is to be interpreted as an average spacing distance. Moreover, the concept of “parallel” is to be interpreted as substantially parallel, e.g. a few degrees deviation (e.g. within + / -3 degrees) is to be considered parallel in the present context. Moreover, the concept of “circular” is to be interpreted as including shapes such as elliptic and oval shapes.

[0014] The plurality of N LED filaments comprises a plurality of O second LED filaments configured to provide, in operation, second LED filament light. The plurality of O second LED filaments are arranged parallel with each other along a circular second path having a second diameter, D2 and they are arranged inside the first path. The second path is in the plane perpendicular to the elongation direction and each second LED filament is spaced apart from neighboring second LED filaments by a second gap having a second spacing distance, S2. D2<D1 and S2<S1 and M>O. For example, the relation between M and O may be such that M=0+n, with n=0, 1, 2, 3, 4. In various embodiments, O is at least 5, thereby enabling an improved luminous output and spatial light distribution. In various embodiments, D1-D2 may be at least 0.5 times or at least 1 time the width of the first and / or second LED filaments.

[0015] In other words, a LED filament lamp comprises an outer path with a plurality of LED filaments. A gap is present between neighboring LED filaments in this outer path. These gaps allow light emitted from the back of these filaments to escape through the gaps and light emitted by LED filaments arranged along the inner path can also escape through the gaps. The luminous output of such a LED filament lamp can be increased to a degree that it can replace HPS lamps in high-performance applications such as street-lighting.

[0016] In embodiments, the first and / or the second LED filament light may be white light.

[0017] The LED filament lamp light may comprise the first and second LED filament light. The first LED filament light may have a first correlated color temperature (CCT1) and the second LED filament light may have a second correlated color temperature (CCT2). In embodiments CCT2-CCT1 <300K i.e. basically the (almost) same CCT. Alternatively, in embodiments, CCT2-CCTl>500K i.e. different CCTs.

[0018] In some embodiments, the first LED filaments are arranged such that said first gaps are angularly aligned, in the plane perpendicular to the elongation direction, with said second LED filaments.

[0019] By such alignment of the gaps between the outer path first LED filaments and the inner path second LED filaments, a significant part of the second LED filament light emitted by the second LED filaments will pass through the gaps and thereby avoid being reflected by the first LED filaments of the outer path.

[0020] For example, each second LED filament of the plurality of O second LED filaments may have a width, W2, and the first spacing distance SI is in a range from 0.5 to 1.5 times W2, preferably from 0.7 to 1.3 times W2 .

[0021] Such a relationship between the spacing distance SI between the outer path first LED filaments and the width W2 of the second LED filaments enable a maximum filling of first LED filaments while still providing sufficiently large gaps for allowing second LED filament light to escape via the gaps. In some embodiments, each second LED filament of the plurality of O second LED filaments is arranged flush with neighboring second LED filaments.

[0022] With such an arrangement of the second LED filaments, it is possible to maximize the number of second LED filaments having a particular width W2. It is to be noted that the flush arrangement in practice means that, due to manufacturing tolerances, a minimal gap will exist between each second LED filament and such a minimal gap will be in a range from 1-1000 micrometers, e.g. 100 micrometer.

[0023] In some embodiments, S2 is in a range from 0.1 mm to 1 mm or from 0.05 mm to 1 mm.

[0024] Such an arrangement, allowing the second spacing distance S2 of the second gaps to be such that the second LED filaments are not flush with each other, allows maximizing the number of second LED filaments, while at the same time allowing control of thermal management, i.e. avoiding overheating of the lamp.

[0025] In some embodiments, S2<O.5S1.

[0026] In other words, the second spacing distance S2 between each second LED filament of the inner path is in some embodiments less than or equal to half the first spacing distance SI between each first LED filament of the outer path. Such an arrangement further enables maximizing the luminous output of the LED filament lamp.

[0027] In some embodiments, D2>0.6-Dl.

[0028] In other words, the diameter of the second path along which the second LED filaments are arranged is in these embodiments at least 0.6 times the diameter of the first path along which the first LED filaments are arranged. This allows for maximizing the number of second LED filaments and thereby also maximizing the luminous output of the LED filament lamp.

[0029] In some embodiments, D2<0.9-Dl.

[0030] In other words, there is spacing between the first and second LED filament arrangements such that second LED filament light can escape well.

[0031] In some embodiments, the light-transmissive envelope 104 has an inner diameter, D3, and wherein D3-Dl<lcm and Dl-D2>lcm. This allows a maximum diameter D2 of the second path and thereby enabling a maximum number of second LED filaments, while at the same time enabling a sufficiently large gap between DI and D2 to allow room for the first and second LED filaments.

[0032] In some embodiments, each LED filament of the plurality of N LED filaments comprises an encapsulant at least partly enclosing the plurality of LEDs and at least partly covering a first major surface of the elongated carrier, the encapsulant comprises one or more of a luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs into converted light and a light-scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into scattered light. The LED filament lamp light may thereby comprise one or more of the converted light, the scattered light and (part of) the LED light.

[0033] By selecting an encapsulant having desired characteristics in terms of wavelength conversion and scattering properties, such embodiments enable improved spectral and / or spatial light distribution.

[0034] In various embodiments, at least 80% of the first and second LED filament light is emitted in the forward direction and / or the elongated carrier has a reflectivity of at least 80 %. Such arrangements provide the LED filament lamp with an improved efficiency.

[0035] In various embodiments, each filament of the plurality of LED filaments may have a length, L, a width, W and a thickness, T, wherein L>8T, L>8W, W>2T and W is in a range from 5 mm to 20 mm.

[0036] The LED filament lamp may in various embodiments further comprise a controller configured to individually control the plurality of M first LED filaments and the plurality of O first LED filaments. By providing a controller, it is possible to control and thereby improve the efficiency of the lamp, for example at lower luminous outputs such as during night time when less luminous output is required in relation to during night time. Various dimming protocols may be used, such as dimming the lamp light by switching off or dimming the second LED filaments while the first LED filaments remain luminous. In other words, in a first operational mode the first and second LED filaments may emit first and second LED filament light, while in a second operational mode only the second LED filaments provide LED filament light i.e. the first LED filament do not or hardly (e.g. <5% of its maximum) emit first LED filament light.

[0037] According to a further aspect, there is provided a luminaire comprising a LED filament lamp according to any one of the preceding claims. Such a luminaire provides effects and advantages that correspond to the effects and advantages presented above in connection with the LED filament lamp.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention where:

[0039] Fig. la schematically illustrates a side view of a LED filament lamp, Fig. lb schematically illustrates a cross-sectional view of the LED filament lamp in figure la,

[0040] Figs. 2a-d schematically illustrate in cross-section a respective embodiment of a LED arranged on and in a carrier,

[0041] Figs. 3 and 4 schematically illustrate a respective top view of LED filaments arranged along paths,

[0042] Fig. 5 schematically illustrates a top view of LED filaments, and Figs. 6a and 6b schematically illustrate a luminaire.

[0043] DETAILED DESCRIPTION

[0044] Figures la and lb show a LED filament lamp 1 providing LED filament lamp light. The LED filament lamp 1 comprises a plurality of N LED filaments 101, 111. Each LED filament 101, 111 of the plurality of N LED filaments comprises an array of a plurality of LEDs 102, 112 arranged on or in an elongated carrier 103, 113 having an elongation direction 10. A light-transmissive envelope 104 at least partly encloses the plurality of LED filaments 101, 111. The LED filament lamp light may be white light having a correlated color temperature in a range from 1700 K to 6500 K, and may have a color rendering index of at least 80 or at least 85.

[0045] As exemplified in figure la, the array may be in the form of LEDs arranged along one or more lines on or in the carrier 103, 113. As illustrated in figures 2-d, the LEDs 102, 112 may be more or less on or in the carrier 103, 113. Figure 2a exemplifies a LED 102, 112 being in the carrier 103, 113 and visible from one side of the carrier 103, 113. Figure 2b exemplifies a LED 102, 112 being partly in the carrier 103, 113 and partly on the carrier 103, 113. Figure 2c exemplifies a LED 102, 112 being on the carrier 103, 113. Figure 2d exemplifies a LED 102, 112 being in the carrier 103, 113 and visible from two sides of the carrier 103, 113.

[0046] As exemplified in figure la, the light-transmissive envelope 104 may be elongated and may be aligned with the elongated carriers 103, 113. Other embodiments may comprise an envelope that is more bulbous or even spherical. A connector 150 is configured to provide electric connection between a power source and the plurality of N LED filaments 101, 111. The connector is preferably also configured to provide a mechanical connection between the LED filament lamp 1 and a power source, for example in the form of a socket configures to be connected to an outlet.

[0047] The plurality of N LED filaments 101, 111 comprises a plurality of M first LED filaments 101 configured to provide, in operation, first LED filament light. The plurality of M first LED filaments 101 are arranged parallel with each other along a circular first path 12 having a first diameter, DI. The first path 12 is in a plane perpendicular to the elongation direction 10 and each first LED filament 101 is spaced apart from neighboring first LED filaments 101 by a first gap 16 having a first spacing distance, SI. As the skilled person will realize, considering manufacturing tolerances, the spacing distance SI and any other spacing distance defined herein is to be interpreted as an average spacing distance.

[0048] Herein, the concept of “parallel” is to be interpreted as substantially parallel, e.g. a few degrees deviation is to be considered parallel in the present context. Moreover, the concept of “circular” is to be interpreted as including shapes such as elliptic and oval shapes.

[0049] The plurality of N LED filaments comprises a plurality of O second LED filaments 111 configured to provide, in operation, second LED filament light. The plurality of O second LED filaments 111 are arranged parallel with each other along a circular second path 14 having a second diameter, D2 and they are arranged inside the first path 12. The second path 14 is in the plane perpendicular to the elongation direction 10 and each second LED filament Ill is spaced apart from neighboring second LED filaments 111 by a second gap 19 having a second spacing distance, S2. D2<D1 and S2<S1 and M>O. For example, the relation between M and O may be such that M=0+n, with n=0, 1, 2, 3, 4. In various embodiments, O is at least 5. As exemplified in figure lb, 0=8 and M=8; as exemplified in figure 3, 0=4 and M=8; as exemplified in figure 4, 0=7 and M=7.

[0050] In various embodiments, D1-D2 may be at least 0.5 times or at least 1 time the width Wl, W2 of the first and / or second LED filaments 101, 111.

[0051] The first and / or the second LED filament light may be white light. The LED filament lamp light may comprise the first and second LED filament light. The first LED filament light may have a first CCT (CCT1) and the second LED filament light may have a second CCT (CCT2). In various embodiments CCT2-CCT1 <300K i.e. basically the (almost) same CCT. Alternatively, in various other embodiments, CCT2-CCTl>500K i.e. different CCTs. In some embodiments, the first LED filaments 101 are arranged such that said first gaps 16 are angularly aligned, in the plane perpendicular to the elongation direction 10, with said second LED filaments 111. Such angular alignments are illustrated in figure lb, figure 3 and figure 4. For example, each second LED filament 111 of the plurality of O second LED filaments 111 may have a width, W2, and the first spacing distance SI is in a range from 0.5 to 1.5 times W2, preferably from 0.7 to 1.3 times W2 .

[0052] As illustrated in figure 4, each second LED filament 111 of the plurality of O second LED filaments 111 may be arranged flush with neighboring second LED filaments 111. As noted above, the concept of being flush with each other is to be understood as including the consideration of manufacturing tolerances such that in practice there is a minimal gap of between filaments that typically is in the range 1-1000 micrometers, e.g. 100 micrometer.

[0053] The second spacing distance S2 , i.e. the second gaps 19, may in a range from 0.1 mm to 1 mm.

[0054] In some embodiments, S2<O.5S1.

[0055] In some embodiments, D2>0.6-Dl.

[0056] In some embodiments, the light-transmissive envelope 104 has an inner diameter, D3, and wherein D3-Dl<lcm and Dl-D2>lcm.

[0057] As illustrated in figure 2c and figure 2d, each LED filament 101, 111 of the plurality of N LED filaments comprises an encapsulant 120 at least partly enclosing the plurality of LEDs 102, 112 and at least partly covering a first major surface (and a second major surface in the example of figure 2d) of the elongated carrier 103, 113, the encapsulant 120 comprises one or more of a luminescent material configured to at least partly convert LED light emitted by the plurality of LEDs 102, 112 into converted light and a lightscattering material configured to at least partly scatter LED light emitted by the plurality of LEDs 102, 112 into scattered light.

[0058] As illustrated in figure lb, the LED filaments 101,111 may be arranged in the LED filament lamp 1 such that at least 80% or at least 90% of the first and second LED filament light is emitted in a forward direction 41, 42 and / or the elongated carrier 103, 113 has a reflectivity of at least 80 % or at least 90%.

[0059] As indicated in figure la and figure 2a, each filament of the plurality of LED filaments 101, 111 may have a length, L, a width, W and a thickness, T, wherein L>8T, L>8W, W>2T and W is in a range from 5 mm to 20 mm. L may be at least 4 cm or at least 6 cm or at least 8 cm. T may be in a range from 2 to 6 mm. As indicated in figure la, the LED filament lamp 1 may further comprise a controller 151 configured to individually control the plurality of M first LED filaments 101 and the plurality of O second LED filaments 111. The controller 151may be configured to control the lamp 1 using various dimming protocols. For example, the lamp light may be dimmed by switching off or dimming the second LED filaments 111 while the first LED filaments 101 remain luminous.

[0060] Figure 5 illustrates an example where the LED filaments 101 in the first (outer) path 12 are tilted. In other words the LED filaments 101 in the first (outer) path 12 may be arranged such that respective surface normal directions N have directions that do not pass a center point C of the outer path 12.

[0061] Figure 6a and figure 6b illustrate a luminaire 500 comprising a LED filament lamp 1 as described in connection with figures 1 to 5 and a reflector 501. Figure 6a is a side view of the luminaire 500 and figure 6b is a bottom view of the luminaire 500.

[0062] Optical simulations show that when the LED filaments 111 arranged at the second (inner) path 14 are aligned with the gaps 16 between the LED filaments 101 in the first (outer) path 12, then the total light output (luminous flux) is increased compared to a configuration with filament LEDs (with minimal spacing) only in the first path. Such a configuration provides an increased total flux even though the optical efficiency may be somewhat reduced.

Claims

CLAIMS:

1. A light emitting diode, LED, filament lamp (1) providing LED filament lamp light, the LED filament lamp (1) comprising:a plurality of N LED filaments (101, 111), each LED filament (101, 111) of the plurality of N LED filaments comprises an array of a plurality of LEDs (102, 112) arranged on or in an elongated carrier (103, 113) having an elongation direction (10),a light-transmissive envelope (104) at least partly enclosing the plurality of LED filaments (101, 111), anda connector (150) configured to provide electric connection between a power source and the plurality of N LED filaments (101, 111), wherein:the plurality of N LED filaments (101, 111) comprises a plurality of M first LED filaments (101) configured to provide, in operation, first LED filament light, the plurality of M first LED filaments (101) being arranged parallel with each other along a circular first path (12) having a first diameter, DI, said first path (12) being in a plane perpendicular to the elongation direction (10), each first LED filament (101) being spaced apart from neighboring first LED filaments (101) by a first gap (16) having a first spacing distance, SI,the plurality of N LED filaments comprises a plurality of O second LED filaments (111) configured to provide, in operation, second LED filament light, the plurality of O second LED filaments (111) being arranged parallel with each other along a circular second path (14) having a second diameter, D2 and being arranged inside the first path (12), said second path (14) being in the plane perpendicular to the elongation direction (10), wherein each second LED filament (111) being spaced apart from neighboring second LED filaments (111) by a second gap (19) having a second spacing distance, S2, and wherein D2<D 1 and S2<S 1 and M>O, andwherein each second LED filament (111) of the plurality of O second LED filaments (111) has a width, W2, and the first spacing distance SI is in a range from 0.5 to 1.5 times W2.

2. The LED filament lamp (1) according to claim 1, whereinthe first spacing distance SI is in a range from 0.7 to 1.3 times W2.

3. The LED filament lamp (1) according to claim 1 or 2, wherein said first LED filaments (101) are arranged such that said first gaps (16) are angularly aligned, in the plane perpendicular to the elongation direction (10), with said second LED filaments (111).

4. The LED filament lamp (1) according to any one of the preceding claims, wherein each second LED filament (111) of the plurality of O second LED filaments (111) is arranged flush with neighboring second LED filaments (111).

5. The LED filament lamp (1) according to any one of claims 1 to 3, wherein S2 is in a range from 0.1 mm to 1 mm.

6. The LED filament lamp (1) according to any one of the preceding claims, wherein S2<O.5S1.

7. The LED filament lamp (1) according to any one of the preceding claims, wherein D2>0.6-Dl.

8. The LED filament lamp (1) according to any one of the preceding claims, wherein the light-transmissive envelope (104) has an inner diameter, D3, and wherein D3-Dl<lcm and Dl-D2>lcm.

9. The LED filament lamp (1) according to any one of the preceding claims, wherein M=0+n, with n=0, 1, 2, 3, 4.

10. The LED filament lamp (1) according to any one of the preceding claims, wherein O is at least 5.

11. The LED filament lamp (1) according to any one of the preceding claims, wherein each LED filament (101, 111) of the plurality of N LED filaments comprises an encapsulant at least partly enclosing the plurality of LEDs (102, 112) and at least partly covering a first major surface of the elongated carrier (103, 113), the encapsulant comprises one or more of a luminescent material configured to at least partly convert LED light emittedby the plurality of LEDs into converted light and a light-scattering material configured to at least partly scatter LED light emitted by the plurality of LEDs into scattered light.

12. The LED filament lamp (1) according to any one of the preceding claims, wherein one or more of the following applies:at least 80% of the first and second LED filament light is emitted in the forward direction;the elongated carrier has a reflectivity of at least 80%.

13. The LED filament lamp (1) according to any one of the preceding claims, wherein each filament of the plurality of LED filaments has a length, L, a width, W and a thickness, T, wherein L>8T, L>8W, W>2T and W is in a range from 5 mm to 20 mm.

14. The LED filament lamp (1) according to any one of the preceding claims, further comprises a controller configured to individually control the plurality of M first LED filaments and the plurality of O first LED filaments.

15. A luminaire (500) comprising a LED filament lamp (1) according to any one of the preceding claims.

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