Light emitting device

Abstract

An LED filament lamp emits lamp light of a third correlated color temperature, CCT3. An LED filament light source emits LED filament light of a first correlated color temperature, CCT1, of a first light intensity, I1, and a first luminous flux, LF1. A transparent envelope at least partly encloses the LED filament light source. A further LED light source provides further LED light of a second correlated color temperature, CCT2, a second light intensity, I2, and a second luminous flux, LF2. The further LED light source provides the further LED light to the envelope. The envelope is a light emitting structure configured to emit the further LED light and to transmit the LED filament light. The lamp light thus comprises one or more of the LED filament light and the further LED light and CCT1≤2500K, 8000K≥CCT2≥3500K and 2≥LF1 / LF2≥0.5, wherein CCT1, CCT2 and LF1 / LF2 are chosen such that 3400K≥CCT3≥2600K.

Description

[0001] Light emitting device

[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 an LED filament light source and a transparent envelope.

[0004] BACKGROUND OF THE INVENTION

[0005] The original bulb lamps powered by electricity were of the type having metal wire filaments enclosed within more or less evacuated glass bulbs. This type of bulb lamps was the ubiquitous choice of light source for more than a century until the introduction of LEDs. Light sources based on LEDs have now replaced the light bulb as a source of light in homes and in many other locations. Initially, mainly due to the inherent structural characteristics of LEDs, the early LED light sources (i.e. LED lamps) did not resemble the earlier light bulbs and in many cases were considered as aesthetically inferior to a light bulb of the earlier type. Thus, for aesthetic reasons, a desire for light sources having the look of the traditional bulb shaped filament lamp came back when it was found that this was technically feasible to make light sources using LED filaments.

[0006] 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.

[0007] WO 2023 / 213608 provides a lighting device that comprises: a light emitting element, and a translucent envelope enclosing the light emitting element and having a surface area at least three times bigger than the light emitting area of the light emitting element, wherein the envelope is coated with a layer of phosphor with a thickness of 0.05-1.0 mm and the layer of phosphor is configured to block less than 30 percent of the visible light emitted by the light emitting element.

[0008] In US 11519563 a light-emitting device is provided that comprises a transparent light exit window, and a LED filament adapted for emitting a first light output along one or more light output directions through the transparent light exit window. The light-emitting device comprises a light guide. The light guide comprises an incoupling feature, configured for receiving light emitted by a light source and for coupling of the light emitted by the light source into the light guide. The light source comprises or is constituted by at least one of the LED filament or a separate light source comprised in the light-emitting device.

[0009] SUMMARY OF THE INVENTION

[0010] It is of interest to provide a LED filament lamp that is capable of overcoming drawbacks of prior art devices.

[0011] 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.

[0012] Hence, according to the present invention there is provided a LED filament lamp configured to emit, in operation, lamp light of a third correlated color temperature, CCT3. The LED filament lamp comprises an LED filament light source configured to emit, in operation, LED filament light of a first correlated color temperature, CCT1, of a first light intensity, 11, and a first luminous flux, LF1. A transparent envelope at least partly encloses the LED filament light source.

[0013] A further LED light source is configured to provide further LED light of a second correlated color temperature, CCT2, a second light intensity, 12, and a second luminous flux, LF2.

[0014] The transparent envelope is light scattering and has a reflectivity below 20%. Preferably, the reflectivity is at least 7%. Inventors have found that with such reflectivity the visibility of the LED filament is high while sufficient further LED light is provided in a homogenous way e.g. from the light guide.

[0015] The further LED light source is configured to provide the further LED light to the envelope. The envelope is a light emitting structure configured to emit, in operation, the further LED light and to transmit the LED filament light. The lamp light thus comprises one or more of the LED filament light and the further LED light and CCTl<2500K (preferably CCTl>1600K), 8000K>CCT2>3500K and 2>LFl / LF2>0.5 , wherein CCT1, CCT2 and LF1 / LF2 are chosen such that 3400K>CCT3>2600K.

[0016] With such a difference in CCT, combined with the ratio in LF between filament and envelope results in the LED filament being well visible through a slightly scattering envelope. In other words, an effect of such a configuration is homogenous functional light in the far field, namely white lamp light having a CCT3 in a range of 2600- 3400K on or close to the blackbody locus (BBL) in the International Commission on Illumination (CIE) 1931 chromaticity space, while the LED filament is well visible through the slightly scattering glowing envelope.

[0017] In various embodiments, the LED filament light, the further LED light and the lamp light may be white light. This type of light is preferred for general lighting.

[0018] In various embodiments, 2300K>CCTl>1700K, 5000K>CCT2>3500K and / or 3300K>CCT3>2700K. These CCTs are preferred for general lighting.

[0019] In various embodiments, the further LED light may have a second color point and the LED filament light may have a first color point being closer to the blackbody locus (BBL) in the International Commission on Illumination (CIE) 1931 chromaticity space, than the second color point. For example, the second color point may be at least 10 Standard Deviation Color Matching (SDCM) above the BBL.

[0020] The envelope may comprise a light guide comprising light out-coupling means and a light in-coupling face. At least part of the further LED light may then be coupled into the light guide via the light in-coupling face and light-guided via total internal reflection through the light guide, and subsequently coupled out of the light guide via the light out- coupling means e.g. light reflective dots or pattern. In other embodiments, the further LED light source is configured to illuminate an inner surface of the envelope. For example, the envelope may comprise a light scattering layer e.g. provided on a major surface of the envelope.

[0021] Such a light guide configuration of the envelope enables improved control of the light of the further LED light source out of the envelope. The term control may refer to setting desired intensities and / or correlated color temperatures. In addition, inventors have found that by using such configuration and the conditions of CCTl<2500K, 8000K>CCT2>3500K and 2>LFl / LF2>0.5, wherein CCT1, CCT2 and LF1 / LF2 are chosen such that 3400K>CCT3>2600K further improves visibility of the LED filament through the light guide based envelope. The reason is that the areas of the light guide which are not covered by the outcoupling means enables improved visibility of the LED filament when the lamp is lit under the specified operating conditions.

[0022] The first light intensity, II, may be related to the second light intensity, 12, such that II > 10*12, preferably II > 25*12, more II > 50*12, most preferably II > 75*12.

[0023] Such a relation between II and 12 means that the visibility of the LED filament through the envelope may be further improved and thereby improve the appearance of the LED filament lamp. The first luminous flux, LF1, may be related to the second luminous flux, LF2, such that LF2 > LF 1.

[0024] Such a relation between LF1 and LF2 means that glare from the LED filament through the envelope may be kept at an appropriate level and thereby improve the appearance of the LED filament lamp.

[0025] The LED filament lamp may further comprise a controller that is configured to (e.g. individually) control one or more of the CCT1, CCT2, LF1, LF2, Il and 12 (by controlling the LED filament light source and the further LED light source). In embodiments, the controller may control one or more of the CCT1, CCT2, LF1, LF2, Il and 12 based on input of a user interface, a clock module and / or a sensor.

[0026] A controller will enable control of the visibility and glare of the LED filament light with respect to the further LED light and thereby enable an improved appearance of the LED filament lamp.

[0027] For example, such a controller may enable the first correlated color temperature, CCT1, of the LED filament light source to be variable between a primary first correlated color temperature, CCTla, and a secondary first correlated color temperature, CCTlb, different from the primary first correlated color temperature, CCTla, such that the third correlated color temperature, CCT3 is variable between a primary third correlated color temperature, CCT3a, and a secondary third correlated color temperature, CCT3b, different from the primary third correlated color temperature, CCT3a.

[0028] Such a controller configuration enables tuning of the visibility of the LED filament.

[0029] Moreover, such a controller may enable the second correlated color temperature, CCT2, of the further LED light source to be variable between a primary second correlated color temperature, CCT2a, and a secondary second correlated color temperature, CCT2b, different from the primary second correlated color temperature, CCT2a, such that the third correlated color temperature, CCT3, is variable between a primary third correlated color temperature, CCT3a, and a secondary third correlated color temperature, CCT3b, different from the primary third correlated color temperature, CCT3a.

[0030] Such a controller configuration also enables tuning of the visibility of the LED filament.

[0031] Such a controller may enable the ratio LF1 / LF2 to be variable such that CCT3 is variable thereby enabling tuning of the visibility of the LED filament.. Such a controller may also or alternatively enable CCT1 and CCT2 to be simultaneously variable such that CCT3 is constant, i.e. within 300 K, thereby enabling a constant CCT3 but tuned visibility of the LED filament. In this context, ‘constant, i.e. within 300K’ means that the CCT has a maximum variation of 300 K.

[0032] The LED filament light source may comprise an array of a plurality of LEDs arranged on a first major surface of an elongated carrier. An elongated encapsulant may at least partly cover the first major surface and at least partly enclose the plurality of LEDs. The further LED light source may comprise a red LED light source, a green LED light source and a blue LED light source. For example, the red LED light source, the green LED light source and the blue LED light source may be controlled by the controller to obtain white, further LED light.

[0033] In a further aspect, there is provided a luminaire comprising a LED filament lamp as summarized above, wherein the LED filament lamp comprises a connector mechanically and electrically connected to a socket of the luminaire.

[0034] Such a luminaire provides the effects and advantages as summarized above.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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:

[0037] Fig. la schematically illustrates a LED filament lamp,

[0038] Fig. lb schematically illustrates a detail of the LED filament lamp in Fig. la, Fig. 2a schematically illustrates an elongated carrier comprising LEDs, Fig. 2b schematically illustrates a cross-section view along A-A of the carrier illustrated in Fig. 2a,

[0039] Fig. 3 schematically illustrates color points in a CIE 1931 chromaticity space, Figs. 4a-c schematically illustrate CCT variation diagrams, and Fig. 5 schematically illustrates a luminaire.

[0040] DETAILED DESCRIPTION

[0041] As illustrated in Figures la and lb, an embodiment of a LED filament lamp 1 is configured to provide, in operation, lamp light 13 of a third correlated color temperature (CCT3) comprises an LED filament light source 100. The LED filament light source 100 is configured to emit, in operation, LED filament light 11 of a first correlated color temperature (CCT1) of a first light intensity (II) and a first luminous flux (LF1). A transparent envelope 101 is at least partly enclosing the LED filament light source 100.

[0042] A further LED light source 102 is configured to provide further LED light 12 of a second correlated color temperature (CCT2), a second light intensity (12) and a second luminous flux (LF2).

[0043] The further LED light source 102 is configured to provide the further LED light 12 to the envelope 101 and the envelope 101 is a light emitting structure configured to emit, in operation, the further LED light 12 and to transmit the LED filament light 11. Thus, the lamp light 13 comprises one or more of the LED filament light 11 and the further LED light 12.

[0044] With regard to CCT1, CCT2 and CCT3, CCTl<2500K, 8000K>CCT2>3500K and 2>LFl / LF2>0.5, wherein CCT1, CCT2 and LF1 / LF2 are chosen such that 3400K>CCT3>2600K.

[0045] As illustrated in Figure 3, the LED filament light 11 may have a first color point 301, 302 and the further LED light 12 may have a second color point 303, 304, the first color point 301, 302 being closer to the blackbody locus, BBL, 350 in the CIE 1931 chromaticity space, than the second color point 303, 304. For example, the second color point 303, 304 may be at least 10 SDCM or at least 12 SDCM, above the BBL 350.

[0046] In various embodiments, the LED filament light may have a color point within 7 SDCM from the BBL.

[0047] In various embodiments, Il is greater than or equal to 10 times 12 and in various embodiments, LF2 is greater than LF1.

[0048] In the embodiment of the LED filament lamp 1 illustrated in Figures la and lb, the envelope 101 comprises a light guide. The light guide comprises light out-coupling means 103 and a light in-coupling face 104. At least part of the further LED light 12 is coupled into the light guide via the light in-coupling face 104 and light-guided via total internal reflection through the envelope 101 in the form of a light guide, and subsequently is coupled out of the envelope 101 in the form of a light guide via the light out-coupling means 103.

[0049] The transparent envelope 101 should be light scattering and having a reflectivity below 20%, and preferably at least 7%. Inventors have found that with such reflectivity the visibility of the LED filament is high while sufficient further LED light is provided in a homogenous way by outcoupling of the further LED light from the light guide. A controller 120 may be configured to control one or more of the CCT1, CCT2, LF1, LF2, Il and 12. The controller may be configured to control CCT1, CCT2, LF1, LF2, Il and 12 based on input of a user interface, a clock module and / or a sensor.

[0050] For example, as illustrated in Figure 4b, the first correlated color temperature, CCT1, of the LED filament light source 100 may be variable between a primary first correlated color temperature (CCTla) 301 and a secondary first correlated color temperature (CCTlb) 302 different from the primary first correlated color temperature, CCTla, 301 such that the third correlated color temperature, CCT3, is variable between a primary third correlated color temperature (CCT3a) 305 and a secondary third correlated color temperature (CCT3b) 306 different from the primary third correlated color temperature, CCT3a 305.

[0051] Alternatively (see Figure 4c) or in addition (see Figure 4a), the second correlated color temperature, CCT2, of the further LED light source 102 may be variable between a primary second correlated color temperature (CCT2a) 303 and a secondary second correlated color temperature (CCT2b) 304 different from the primary second correlated color temperature, CCT2a, 303 such that the third correlated color temperature, CCT3, is variable between a primary third correlated color temperature (CCT3a) 305 and a secondary third correlated color temperature (CCT3b) 306 different from the primary third correlated color temperature, CCT3a, 305.

[0052] Figure 4b illustrates an example where CCT1 is controlled to vary between CCTla 301 and CCTlb 302 whereas CCT2 is kept constant. As a consequence, CCT3 varies between CCT3a 305 and CCT3b 306.

[0053] Figure 4c illustrates an example where CCT2 is controlled to vary between CCT2a 303 and CCT2b 304 whereas CCT1 is kept constant. As a consequence, CCT3 varies between CCT3a 305 and CCT3b 306.

[0054] In other embodiments, CCT1 and CCT2 are controlled to simultaneously vary such that CCT3 is constant.

[0055] In further embodiments, the ratio LF1 / LF2 is controlled to vary such that CCT3 is variable.

[0056] The following table exemplifies how the control of CCT1, CCT2 and the ratio

[0057] LF1 / LF2 affects CCT3:

[0058] Referring also to Figures 2a and 2b, the LED filament light source 100 may comprise an array of a plurality of LEDs 141 arranged on a first major surface 143 of an elongated carrier 142. An elongated encapsulant 144 may at least partly cover the first major surface 143 and at least partly enclose the plurality of LEDs 141. Moreover, the further LED light source 102 may comprise a red LED light source 131, a green LED light source 132 and a blue LED light source 133.

[0059] Figure 5 illustrates an embodiment of a luminaire 500 comprising a LED filament lamp 1 as described herein, wherein the LED filament lamp 1 comprises a connector 121 mechanically and electrically connected to a socket 501 of the luminaire 500.

Claims

CLAIMS:

1. A light emitting diode, LED, filament lamp (1) configured to emit, in operation, lamp light (13) of a third correlated color temperature, CCT3, and the LED filament lamp (1) comprising: an LED filament light source (100) configured to emit, in operation, LED filament light (11) of a first correlated color temperature, CCT1, of a first light intensity, II, and a first luminous flux, LF 1 ; a transparent envelope (101) at least partly enclosing the LED filament light source (100); the envelope is light scattering and has a reflectivity below 20%; a further LED light source (102) configured to provide further LED light (12) of a second correlated color temperature, CCT2, a second light intensity, 12, and a second luminous flux, LF2; wherein: the further LED light source (102) is configured to provide the further LED light (12) to the envelope (101); the envelope (101) comprises a light emitting structure (110) configured to emit, in operation, the further LED light (12) and to transmit the LED filament light (11); the envelope (101) comprises a light guide as the light emitting structure (110), the light guide comprising light out-coupling means (103) and a light in-coupling face (104), wherein at least part of the further LED light (12) is coupled into the light guide via the light in-coupling face (104) and light-guided via total internal reflection through the light guide (101), and subsequently is coupled out of the light guide (101) via the light out- coupling means (103); the lamp light (13) comprises the LED filament light (11) and the further LED light (12); andCCTl<2500K, 8000K>CCT2>3500K and 2>LFl / LF2>0.5, wherein CCT1, CCT2 and LF1 / LF2 are chosen such that 3400K>CCT3>2600K, and wherein the LED filament lamp further comprising a controller (120) configured to control one or more of the CCT1, CCT2, LF1, LF2, Il and 12,wherein CCT1 and CCT2 are simultaneously variable such that CCT3 has a maximum variation of 300 K.

2. The LED filament lamp (1) according to claim 1, wherein the envelope has a reflectivity of at least 7%.

3. The LED filament lamp (1) according to claim 1 or 2, wherein II > 10*12.

4. The LED filament lamp (1) according to any one of the previous claims, wherein LF2>LF 1.

5. The LED filament lamp (1) according to any of the preceding claims, wherein the first correlated color temperature, CCT1, of the LED filament light source (100) is variable between a primary first correlated color temperature, CCTla, (301) and a secondary first correlated color temperature, CCTlb, (302) different from the primary first correlated color temperature, CCTla, (301) such that the third correlated color temperature, CCT3, is variable between a primary third correlated color temperature, CCT3a, (305) and a secondary third correlated color temperature, CCT3b, (306) different from the primary third correlated color temperature, CCT3a (305).

6. The LED filament lamp (1) according to any of the preceding claims, wherein the second correlated color temperature, CCT2, of the further LED light source (102) is variable between a primary second correlated color temperature CCT2a (303) and a secondary second correlated color temperature CCT2b (304) different from the primary second correlated color temperature CCT2a (303) such that the third correlated color temperature, CCT3 is variable between a primary third correlated color temperature CCT3a (305) and a secondary third correlated color temperature CCT3b (306) different from the primary third correlated color temperature CCT3a (305).

7. The LED filament lamp (1) according to any one of the preceding claims, wherein the ratio LF1 / LF2 is variable such that CCT3 is variable.

8. The LED filament lamp (1) according to any one of the previous claims, wherein 2300K>CCTl>1700K, 5000K>CCT2>3500K, 3300K>CCT3>2700K.

9. The LED filament lamp (1) according to any one of the previous claims, wherein the further LED light (12) has a second color point (303, 304) and the LED filament light (11) has a first color point (301, 302) being closer to the blackbody locus, BBL, (350) in the International Commission on Illumination, CIE, 1931 chromaticity space, than the second color point (303, 304).

10. The LED filament lamp (1) according to claim 9, wherein the second color point (303, 304) is at least 10 Standard Deviation Color Matching, SDCM, above the BBL (350).

11. The LED filament lamp (1) according to any one of the previous claims, wherein: the LED filament light source (100) comprises an array of a plurality of LEDs (141) arranged on a first major surface (143) of an elongated carrier (142), an elongated encapsulant (144) at least partly covering the first major surface (143) and at least partly enclosing the plurality of LEDs (141), and the further LED light source (102) comprises a red LED light source (131), a green LED light source (132) and a blue LED light source (133).

12. A luminaire (500) comprising a LED filament lamp (1) according to any one of the preceding claims, wherein the LED filament lamp (1) comprises a connector (121) mechanically and electrically connected to a socket (501) of the luminaire (500).

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