LED filament

Abstract

The present invention relates to an LED filament 10 comprising: a support 16; a plurality of first blue LEDs 22 disposed on the support and adapted to emit first blue light 24; a first elongated encapsulant 26 covering the first blue LEDs and at least a portion of the support, the first elongated encapsulant 26 having a first luminescent material 28 configured to convert at least a portion of the first blue light into first converted light 30; and an LED filament 14 including a top surface 34 on or above the first elongated encapsulant, the LED filament further comprising a string 36, 36′ of second blue LEDs 38 disposed on the top surface of the LED filament and adapted to emit second blue light 40, the light output surfaces 42 of the second blue LEDs facing away from the LED filament.

Description

[Technical Field]

[0001] The present invention relates to a light emitting diode (LED) filament. The present invention also relates to a lamp or luminaire comprising such an LED filament. The present invention also relates to a lighting system comprising such a lamp or luminaire. [Background technology]

[0002] A trend in lighting is LED filament lamps, which are LED lamps designed to resemble traditional incandescent bulbs with a visible filament for aesthetic and light distribution purposes, but with highly efficient light-emitting diodes. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to improve the performance and / or functionality of LED filaments. [Means for solving the problem]

[0004] According to a first aspect of the present invention, this and other objects are achieved by an LED filament comprising a carrier, a plurality of first blue LEDs adapted to emit a first blue light, the plurality of first blue LEDs being arranged on the carrier, and a first elongated encapsulant covering the plurality of first blue LEDs and at least a portion of the carrier, the first elongated encapsulant having a top surface, the first elongated encapsulant having a first luminescent material configured to convert at least a portion of the first blue light into a first converted light, the LED filament further comprising: a string of second blue LEDs adapted to emit a second blue light, the string of second blue LEDs being arranged on the top surface of the LED filament, the light output surfaces of the second blue LEDs facing away from the LED filament.

[0005] In this way, optical crosstalk (i.e., the effect of the blue LED being operated stimulating the phosphor converter of the LED filament, which then emits light of a different color) is reduced / non-existent, and therefore a pure blue color can be provided.

[0006] Preferably, less than 5% of the light of the second blue LED is converted (by the first luminescent material), more preferably less than 3% of the light of the second blue LED is converted (by the first luminescent material), and most preferably less than 1%, for example 0%, of the light of the second blue LED is converted (by the first luminescent material).

[0007] The top surface has a top surface area (TSA) and the string of second blue LEDs has a string area (SA), where SA<0.4TSA, in particular SA<0.2TSA. In this way, the string of second blue LEDs does not block and / or absorb (excessive amounts of) the first blue light and / or the first converted light.

[0008] The LED filament may further include a controller configured to individually control the emission of the first blue light by the plurality of first blue LEDs and the emission of the second blue light by the string of second blue LEDs. In this manner, the LED filament may selectively provide white light, colored light, or a combination thereof.

[0009] The string of second blue LEDs may or may not be disposed on a light-transmitting substrate, allowing the first blue light and / or the first converted light to easily pass through the string of second blue LEDs disposed above the first blue LEDs. The second blue LEDs and their electrical tracks may still block some light, but the first blue light and / or the converted light passes through the light-transmitting substrate or passes directly past the second blue LEDs and electrical tracks.

[0010] The second string of blue LEDs may be covered by a second elongated encapsulant that does not contain any luminescent or light-scattering material. In other words, the second elongated encapsulant does not contain any luminescent or light-scattering material. In this way, the optical light distribution requirements of the LED filament can be met. The second elongated encapsulant may be, for example, dome-shaped.

[0011] The string of second blue LEDs may have an LED pitch of less than 1000 μm, preferably less than 800 μm, more preferably less than 600 μm, and most preferably less than 500 μm. "LED pitch" may be the center-to-center distance between adjacent second blue LEDs of the string.

[0012] The LED filament may further include a plurality of red LEDs adapted to emit red light and, optionally, a plurality of green LEDs adapted to emit green light, with the plurality of red LEDs and the optional plurality of green LEDs disposed on the top surface of the LED filament. Alternatively, the plurality of red LEDs and the optional plurality of green LEDs may be disposed on the support for the LED filament, for example, below or adjacent to the first elongated encapsulant. The plurality of red LEDs and the optional plurality of green LEDs enable the LED filament to provide light of various colors. Accordingly, the controller may be further configured to individually control the emission of the red light by the plurality of red LEDs and the emission of green light by any plurality of green LEDs.

[0013] The plurality of red LEDs and the optional plurality of green LEDs may be arranged in at least one string, such as a string of red LEDs and another string of green LEDs, or a combined string of a second blue LED, a red LED, and optionally a green LED. Thus, in one or more embodiments, the string of second blue LEDs includes only a second blue LED. Also, in one or more embodiments, the string of second blue LEDs includes the plurality of red LEDs and optionally the plurality of green LEDs.

[0014] The first luminescent material may be configured to convert at least a portion of the first blue light into first converted light comprising first green / yellow light and first red light that, together with unconverted first blue light emitted by the plurality of first blue LEDs, form first white light having a first correlated color temperature (CCT1), preferably CCT1≦2500K.

[0015] The filament circuit may further include a plurality of third blue LEDs adapted to emit a third blue light, the plurality of third blue LEDs being disposed on the support, and a third elongated encapsulant covering the plurality of third blue LEDs and at least a portion of the support, the third elongated encapsulant having a second luminescent material configured to convert at least a portion of the third blue light into a second converted light. In this manner, the LED filament may provide white light with various color temperatures while still reducing or avoiding optical crosstalk.

[0016] The second string of blue LEDs may be disposed at the interface between the first elongated encapsulant and the third elongated encapsulant to reduce or minimize its effect on the first blue / converted light and the third blue / second converted light.

[0017] The second luminescent material may be configured to convert at least a portion of the third blue light into second converted light including second green / yellow light and second red light that, together with unconverted third blue light emitted by the plurality of third blue LEDs, form a second white light having a second correlated color temperature (CCT2) higher than the first correlated color temperature. Preferably, CCT2-CCT1≧500K, more preferably, CCT2-CCT1≧1000K. Typically, CCT2≧3500K. Furthermore, the color rendering index (CRI) of the first white light and the second white light may be at least 80.

[0018] According to a second aspect of the present invention, there is provided a lamp or luminaire comprising an LED filament according to the first aspect and an antenna operatively coupled to (the) controller of the LED filament, said antenna allowing the lamp or luminaire to be remotely controlled. The lamp may for example be a (retrofit) light bulb.

[0019] According to a third aspect of the present invention there is provided a lighting system comprising a lamp or luminaire according to the second aspect and at least one (remote) user interface for providing user input and / or at least one (remote) sensor for sensing data, wherein the controller is configured to control the first plurality of blue LEDs and the second plurality of blue LEDs, and optionally the red LEDs, the green LEDs and the third blue LEDs based on the user input and / or the data.

[0020] It is to be noted that the invention relates to all possible combinations of the features recited in the claims. [Brief explanation of the drawings]

[0021] These and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, in which embodiments of the invention are shown. [Figure 1a]1 is a cross-sectional view of an LED filament according to an embodiment of the present invention. [Figure 1b] FIG. 1b is a side view of the LED filament of FIG. 1a. [Figure 1c] FIG. 1b is a top view of the LED filament of FIG. 1a. [Figure 2a] 1 illustrates an LED filament according to another embodiment of the present invention. [Figure 2b] 1 illustrates an LED filament according to another embodiment of the present invention. [Figure 2c] 1 illustrates an LED filament according to another embodiment of the present invention. [Figure 2d] 1 illustrates an LED filament according to another embodiment of the present invention. [Figure 2e] 1 illustrates an LED filament according to another embodiment of the present invention. [Figure 3] FIG. 1 is a side view of an embodiment of the present invention including a lamp.

[0022] The sizes of layers and regions as shown in the figures may be exaggerated for illustrative purposes and are therefore shown to illustrate the general structure of embodiments of the present invention. Like reference numerals refer to like elements throughout. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are presented for thoroughness and completeness, and will fully convey the scope of the invention to those skilled in the art.

[0024] 1a-1c illustrate an LED filament 10 according to an embodiment of the present invention. The LED filament 10 can provide LED filament (device) light 12.

[0025] The LED filament 10 has an LED filament 14. The LED filament 14 may be rigid or flexible.

[0026] The LED filament 14 has a support 16. The support 16 is typically a substrate. The support 16 is typically elongated. Preferably, the LED filament 14 has a length L, where L>5D. A distance D corresponding to the width of the support 16 may be, for example, in the range of 0.5 to 5 mm. The support 16 may include two elongated edges 18a, 18b disposed at a distance D from each other, a first (main) surface 20a, and a second (main) surface 20b disposed opposite the first surface 20a. The support 16 may be rigid (e.g., made from a polymer, glass, quartz, metal, or sapphire) or flexible (e.g., made from a polymer or metal, e.g., a film or foil).

[0027] The LED filament 14 further includes a plurality of first blue LEDs 22 adapted to emit first blue light 24. The first blue light 24 may have a dominant peak wavelength within a wavelength range of 450 to 490 nm, for example. The plurality of first blue LEDs 22 are disposed on the support 16. Specifically, the plurality of first blue LEDs 22 may be attached to a first surface 20a of the support 16. Furthermore, the plurality of first blue LEDs 22 are preferably disposed in a linear array / string / single row on the longitudinal centerline of the support 16, here. The number of first blue LEDs 22 may be, for example, at least 10 or at least 20.

[0028] The LED filament 14 further includes a first elongated encapsulant 26 covering the plurality of first blue LEDs 22 and at least a portion of the support 16. The first elongated encapsulant 26 includes a first luminescent material 28 configured to convert at least a portion of the first blue light 24 into first converted light 30. Specifically, the first luminescent material 28 may be configured to convert at least a portion of the first blue light 24 into first converted light 30 including first green / yellow light and first red light, which, together with the unconverted first blue light 24, form first white light 32 having a first correlated color temperature CCT1. Preferably, CCT1≦2500 K (warm white light). Furthermore, the color rendering index (CRI) of the first white light 32 is preferably at least 80. The first luminescent material 28 may be a phosphor, and the first elongated encapsulant 26 may be made of, for example, silicone. The plurality of first blue LEDs 22 with the first elongated encapsulant 26 and the first luminescent material 28 may be referred to as a first white light source.

[0029] The LED filament 14 further has a top surface 34, here the top surface 34 of the first elongated encapsulant 26. The top surface 34 is opposite the bottom surface (second (support) surface 20b) of the LED filament 14. The top surface 34 and the bottom surface 20b may be surrounded by end surfaces. As can be seen in FIG. 1c, the top surface 34 has a top surface area TSA, generally TSA=L×D.

[0030] The LED filament 10 further includes a second light source including a string 36 of second blue LEDs 38 adapted to emit second blue light 40. The string 36 of second blue LEDs 38 here includes only second blue LEDs 38. The string of second blue LEDs is disposed directly on the top surface 34 of the LED filament 14 or on a light-transmitting substrate (not shown) on the top surface 34 of the LED filament 14 such that light output surfaces 42 of the second blue LEDs 38 face away from the LED filament 14. That is, during operation, the second blue light 40 is emitted away from the first encapsulant 26 containing the luminescent material 28. The light output surface 42 of each blue LED 38 may be the top surface, while the opposite bottom surface 44 of the blue LEDs 38 faces, and is optionally attached to, the top surface 34 of the LED filament 14 (of the first elongated encapsulant 26). Therefore, the second blue LEDs 38 may be referred to as top-emitting second blue LEDs 38. The string 36 of second blue LEDs 38 is preferably disposed at the longitudinal centerline of the top surface 34 of the LED filament 14, as seen in FIG. 1c. That is, the first and second blue LEDs 22, 42 may be arranged stacked facing the same direction. The number of second blue LEDs 38 may be, for example, at least 10, or at least 20.

[0031] By having a string 36 of second blue LEDs 38 disposed above / in front of the first elongated encapsulant 26 / first luminescent material 28 and emitting second blue LED light 40 away from the first elongated encapsulant 26 / first luminescent material 28 during operation, optical crosstalk (i.e., the effect of an operated blue LED 38 stimulating the phosphor converter / luminescent material 28 of the LED filament, which then emits light of a different color) is reduced / non-existent, and thus a pure blue color can be provided.

[0032] The string 36 of second blue LEDs 38 may have a string area SA. The string area SA may be the sum of the area of ​​the light output surface 42 of the second blue LED 38 and the area of ​​the associated electrical tracks. The (approximate) string area SA is indicated by diagonal stripes in FIG. 1c. Preferably, SA<0.2TSA, so that the second blue LEDs 38 do not block excessive amounts of the first blue light 24 and / or the first converted light 30. The electrical tracks may include, for example, copper wires / tracks. Furthermore, the string 36 of second blue LEDs 38 may have an ultra-narrow LED pitch P of less than 1000 μm.

[0033] The LED filament 10 may further include a second elongated encapsulant 46 covering the string 36 of the second blue LEDs 38. The second elongated encapsulant 46 does not include a luminescent material or a light-scattering material. The second elongated encapsulant 46 may be transparent, for example. The second elongated encapsulant 46 may be made of silicone, for example. The second elongated encapsulant 46 may have a dome-shaped cross-section with respect to width D, as seen in FIG. 1a, for example. The dome-shaped cross-section may be uniform along substantially the entire length of the second elongated encapsulant 46.

[0034] The LED filament 10 may further include an electronic controller 48. The controller 48 is configured to separately control the emission of the first blue light 24 by the plurality of first blue LEDs 22 and the emission of the second blue light 40 by the string of second blue LEDs 38. Thus, during operation, the LED filament 10 in Figures 1a-1c may selectively provide white light 32, blue light 40, or a combination thereof.

[0035] 2a is a cross-sectional view of an LED filament 10 according to another embodiment. The LED filament 10 in FIG. 2a is similar to the LED filament 10 in FIGS. 1a-1c, but further includes a plurality of red LEDs 50 adapted to emit red light 52 and a plurality of green LEDs 54 adapted to emit green light 56. The plurality of red LEDs 50 and the plurality of green LEDs 54 are disposed directly on the top surface 34 of the LED filament 14 or on a light-transmitting substrate (not shown) on the top surface 34 of the LED filament 14, with their light output surfaces 42′ facing away from the LED filament 14. The plurality of red LEDs 50 are disposed in a string on one side of the string 36 of the second blue LEDs 38, and the string of red LEDs 50 is parallel to the string 36 of the second blue LEDs 38. The plurality of green LEDs 54 are arranged in a separate string on the other side of the string 36 of the second blue LEDs 38, and the string of green LEDs 54 is also parallel to the string 36 of the second blue LEDs 38. The number of red LEDs 50 may be, for example, at least 10 or at least 20. The number of green LEDs 54 may be, for example, at least 10 or at least 20. The plurality of red LEDs 50 may be covered by an elongated encapsulant 58 similar to the second elongated encapsulant 46. Similarly, the plurality of green LEDs 54 may be covered by an elongated encapsulant 60 similar to the second elongated encapsulant 46. Alternatively, the second elongated encapsulant 46 may be extended to cover the red LEDs 50 and the green LEDs 54 (not shown in FIG. 2a). Here, the controller 48 may be configured to individually control the emission of red light 52 by the plurality of red LEDs 50 and the emission of green light 56 ​​by any plurality of green LEDs 54. Thus, in operation, the LED filament 10 in FIG. 2a can selectively provide white light 32, blue light 40, red light 50, green light 54, or combinations thereof.

[0036] 2b-2c are cross-sectional views of an LED filament 10 according to another embodiment. The LED filament 10 in each of FIGS. 2b-2c is similar to the LED filament 10 in FIG. 2a, except that a plurality of red LEDs 50 and a plurality of green LEDs 54 are disposed on the support 16 of the LED filament 14. Specifically, the plurality of red LEDs 50 may be disposed on and attached to the first surface 20a of the support 16 (on one side of the plurality of first blue LEDs 22), and the plurality of green LEDs 54 may similarly be disposed on and attached to the first surface 20a of the support 16 (but on the opposite side of the plurality of first blue LEDs 22). That is, the plurality of red LEDs 50 may be disposed in a string parallel to the linear array / string / single row of the first blue LEDs 22. Similarly, the plurality of green LEDs 54 may be disposed in another string parallel to the linear array / string / single row of the first blue LEDs 22.

[0037] In Figure 2b, the first elongated encapsulant 26 covers not only the first blue LEDs 22, but also the red LEDs 50, the green LEDs 54, and at least a portion of the support 16. In Figure 2c, the first elongated encapsulant, designated by reference numeral 26', has a limited extension in the width direction and covers (only) the first blue LEDs 22 and a portion of the support 16, but does not cover the red LEDs 50 and the green LEDs 54. The red LEDs 50 and the green LEDs 54 may be uncovered or may be provided with elongated encapsulants 58, 60 similar to Figure 2a (not shown in Figure 2c).

[0038] FIG. 2d is a top view of an LED filament 10 according to another embodiment. The LED filament 10 in FIG. 2d is similar to the LED filament 10 in FIG. 2a, except that the string comprising the second blue LED 38 also includes a plurality of red LEDs 50 and a plurality of green LEDs 54. That is, the plurality of second blue LEDs 38, the plurality of red LEDs 50, and the plurality of green LEDs 54 are arranged in a single string / line / row 36′, preferably at the longitudinal centerline of the top surface 34 of the LED filament 14. The LEDs 38, 50, 54 may be arranged in the string 36′ in an alternating color order (e.g., RGBRGB, i.e., (RGB)n, where n is preferably ≧5), although other arrangements, such as batching, may also be possible. Here, the second elongated encapsulant 46 may also cover the red LED 50 and the green LED 54.

[0039] FIG. 2e is a cross-sectional view of an LED filament 10 according to another embodiment. The LED filament 10 in FIG. 2e is similar to the LED filament 10 in FIG. 2a, except that the LED filament 14 further includes a plurality of blue LEDs 62 adapted to emit a third blue light. The plurality of third blue LEDs 62 are disposed on the support 16. Specifically, the plurality of third blue LEDs 62 may be attached to the first surface 20a of the support 16. Furthermore, the plurality of third blue LEDs 62 are preferably arranged in a linear array / string / single column. The string of third blue LEDs 62 may be arranged parallel to the aforementioned string of first blue LEDs 22. These strings may be attached on both sides of the longitudinal centerline of the support 16, as shown in FIG. 2e. The number of third blue LEDs 62 may be, for example, at least 10 or at least 20.

[0040] The LED filament 14 in FIG. 2e further includes a third elongated encapsulant 66 covering the plurality of third blue LEDs and a portion of the support 16. The third elongated encapsulant 66 includes a second luminescent material 68 configured to convert at least a portion of the third blue light 64 into second converted light 70. Specifically, the second luminescent material 68 may be configured to convert at least a portion of the third blue light 64 into second converted light 70 including second green / yellow light and second red light, which, together with the unconverted third blue light 64, form second white light 72 having a second correlated color temperature CCT2 different from the first correlated color temperature CCT1. Preferably, CCT2-CCT1≧500K, more preferably CCT2-CCT1≧1000K. Typically, CCT2≧3500K. Furthermore, the color rendering index (CRI) of the second white light 72 is preferably at least 80. The second luminescent material 68 may be a phosphor, and the second elongated encapsulant 66 may be made of, for example, silicone. The plurality of third blue LEDs 62 with the third elongated encapsulant 66 and the second luminescent material 68 may be referred to as a third white light source.

[0041] Each of the first elongated encapsulant 26 and the third elongated encapsulant 66 may cover approximately half of the support 16 when viewed in the width direction. Therefore, the first elongated encapsulant 26 and the third elongated encapsulant 66 may be parallel to each other (in the length direction of the LED filament 12 / LED filament 14). The top surface 34 of the LED filament 14 may be formed here by the top surfaces of the first elongated encapsulant 26 and the third elongated encapsulant 66. Furthermore, a string of second blue LEDs 38 may be disposed at a boundary 74 between the first elongated encapsulant 26 and the third elongated encapsulant 66 (at the top surface 34). A plurality of red LEDs 50 may be disposed in the first elongated encapsulant 26, and a plurality of green LEDs 54 may be disposed in the third elongated encapsulant 66. Alternatively, a single string of second blue LEDs 38, red LEDs 50 and green LEDs 54 (as in FIG. 2d) may be disposed at border 74 (not shown).

[0042] The controller 48 may also be configured here to individually control the emission of the third blue light 64 by the plurality of third blue LEDs 62. Thus, during operation, the LED filament 10 in FIG. 2e may selectively provide the first white light 32, the second white light 72, the blue light 40, the red light 50, the green light 54, or a combination thereof. Furthermore, the second elongated encapsulant here may be a common elongated encapsulant 46' that covers not only the string 36 of the second blue LEDs 38, but also the plurality of red LEDs 50 and the optional plurality of green LEDs 54. The common elongated encapsulant 46' may simplify the manufacture of the LED filament 10. Alternatively, the LED filament 10 in FIG. 2e may have individual elongated encapsulants 46, 58, 60, for example, as in FIG. 2a.

[0043] 4 illustrates a lamp 102 according to an embodiment of the present invention. The lamp 102 includes at least one LED filament 10, a controller 48, and an antenna 104 operatively coupled to the controller 48. The antenna 104 may be configured to receive user input from at least one user interface 106 and / or data from at least one sensor 108. The controller 54 may also be configured to control the plurality of first blue LEDs 22 and the plurality of second blue LEDs 38, as well as the optional red LED 50, green LED 54, and third blue LED 62, based on the user input from the user interface 106 and / or (sensor) data from the at least one sensor 108. The lamp 102, the user interface 106, and / or the sensor 108 may be referred to as the lighting system 100. The user interface 106 and / or the sensor 108 may be remote from the lamp 102. The user interface 106 may be embodied in, for example, a mobile phone. The at least one sensor 108 may include, for example, at least one of a camera, a light sensor, a presence sensor, and a proximity sensor.

[0044] The LED filament 14 / LED filament 10 is here arranged in a coiled configuration, although other configurations, such as a straight configuration, are possible. The lamp 102 may further include an envelope 110 surrounding the LED filament 14 / LED filament 10 and a base or cap 112 for electrically and mechanically connecting the lamp 102 to an external socket (not shown). The lamp 102 may be, for example, a retrofit light bulb.

[0045] Those skilled in the art will appreciate that the present invention is by no means limited to the preferred embodiments described above, but on the contrary, many modifications and variations are possible within the scope of the appended claims.

[0046] Furthermore, those skilled in the art will understand and achieve modifications to the disclosed embodiments in practicing the claimed invention, from a study of the drawings, the specification and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and the singular does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An LED filament, support, a plurality of first blue LEDs adapted to emit first blue light, the plurality of first blue LEDs being disposed on the support; a first elongated encapsulant covering the plurality of first blue LEDs and at least a portion of the support, the first elongated encapsulant having a first luminescent material configured to convert at least a portion of the first blue light into first converted light, the first elongated encapsulant having a top surface; and an LED filament having a string of second blue LEDs adapted to emit a second blue light, the string of second blue LEDs being attached directly to the top surface of the LED filament, the light output surfaces of the second blue LEDs facing away from the top surface.

2. 2. The LED filament of claim 1, wherein the top surface has a top surface area TSA, and the string of second blue LEDs has a string area SA, where SA<0.4TSA.

3. 3. The LED filament of claim 1, further comprising a controller configured to individually control the emission of the first blue light by the plurality of first blue LEDs and the emission of the second blue light by the string of second blue LEDs.

4. 4. The filament of claim 1, wherein the second string of blue LEDs is disposed on a light-transmitting substrate or is not disposed on a substrate.

5. 5. The filament of claim 1, wherein the second string of blue LEDs is covered by a second elongated encapsulant that is free of luminescent material and light-scattering material.

6. 6. The LED filament of claim 1, wherein the string of second blue LEDs has an LED pitch of less than 1000 μm.

7. 7. An LED filament according to claim 1, further comprising a plurality of red LEDs adapted to emit red light, and optionally a plurality of green LEDs adapted to emit green light, the plurality of red LEDs and the optional plurality of green LEDs being arranged on the top surface of the LED filament.

8. 8. The LED filament of claim 7, wherein the plurality of red LEDs and optionally the plurality of green LEDs are arranged in at least one string of the LED filament.

9. 9. The LED filament of claim 7 or 8, wherein the string of second blue LEDs includes only second blue LEDs.

10. 9. An LED filament according to claim 7 or 8, wherein the second string of blue LEDs also includes the plurality of red LEDs and optionally the plurality of green LEDs.

11. 11. The LED filament of claim 1, wherein the first luminescent material is configured to convert at least a portion of the first blue light into first converted light comprising first green / yellow light and first red light that, together with unconverted first blue light emitted by the plurality of first blue LEDs, form first white light having a first correlated color temperature CCT1, wherein CCT1≦2500K.

12. The LED filament is a plurality of third blue LEDs adapted to emit third blue light, the plurality of third blue LEDs being disposed on the support; and 12. The LED filament of claim 1, further comprising a third elongated encapsulant covering the plurality of third blue LEDs and at least a portion of the support, the third elongated encapsulant having a second luminescent material configured to convert at least a portion of the third blue light into a second converted light.

13. 13. The LED filament of claim 12, wherein the second string of blue LEDs is disposed at an interface between the first elongated encapsulant and the third elongated encapsulant.

14. 13. The LED filament of claims 11 and 12, wherein the second luminescent material is configured to convert at least a portion of the third blue light into second converted light comprising second green / yellow light and second red light that, together with unconverted third blue light emitted by the plurality of third blue LEDs, form second white light having a second correlated color temperature CCT2 higher than the first correlated color temperature, wherein CCT2-CCT1≧500K, and the color rendering index of the first white light and the second white light is at least 80.

15. a lamp or luminaire comprising an LED filament according to any one of claims 1 to 14 and an antenna operatively coupled to a controller of said LED filament; at least one user interface for providing user input and / or at least one sensor for sensing data, The lighting system is configured such that the controller controls the first plurality of blue LEDs and the second plurality of blue LEDs, and optionally the red LEDs, the green LEDs, and the third blue LEDs based on the user input and / or the data.

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