Color temperature controllable lighting device comprising different LED filaments

Abstract

The present disclosure relates to a lighting device. The lighting device (100) comprises a first elongated light-emitting diode, LED, filament (110) and a second elongated LED filament (120). The lighting device further comprises an at least partially light-transmissive envelope (130), which at least partially envelops at least the first LED filament and the second LED filament, and a base (140) on which the at least partly light-transmissive envelope is mounted. The first LED filament is configured to emit light with a different color temperature than the second LED filament. Further, the second LED filament is at least partially curved such that it defines at least part of a contour of a volume (421). The first LED filament is arranged at least partially within the volume.

Claims

1. A lighting device comprising: a first elongated light-emitting diode, LED, filament; a second elongated LED filament; an at least partially light-transmissive envelope at least partially enveloping at least said first LED filament and said second LED filament; and a base on which said at least partly light-transmissive envelope is mounted; wherein said first LED filament is configured to emit light with a different color temperature than said second LED filament; wherein said second LED filament is at least partially curved such that it defines at least part of a contour of a volume; and wherein said first LED filament is arranged at least partially within said volume, wherein said first LED filament has a first LED filament length and said second LED filament has a second LED filament length, and wherein said second LED filament length is more than twice as long as said first LED filament length, wherein said first LED filament is arranged along a central axis of said volume and said second LED filament forms a helix shape.

2. The lighting device of claim 1, wherein said first LED filament is adapted to emit light with a higher color temperature than said second LED filament.

3. The lighting device of claim 1, wherein the first LED filament is configured to emit light with a color temperature which is higher than 2700 K.

4. The lighting device of claim 1, wherein the second LED filament is configured to emit light with a color temperature which is lower than 2500 K.

5. The lighting device of claim 1, wherein said first LED filament has a larger diameter than said second LED filament.

6. The lighting device of claim 5, wherein said first LED filament has a first LED filament diameter and said second LED filament has a second LED filament diameter, and wherein said first LED filament diameter is more than twice as large as said second LED filament diameter.

7. The lighting device of claim 1, wherein said first LED filament is substantially straight or less curved than said second LED filament.

8. The lighting device of claim 1, further comprising a controller configured to control a power supplied to said first LED filament and a power supplied to said second LED filament.

9. The lighting device of claim 1, wherein said first LED filament and said second LED filament comprise LEDs configured to emit light with a peak wavelength in the range 365-380 nm and/or in the range 435-500 nm.

10. The lighting device of claim 1, wherein said first LED filament comprises: a first substrate having a first side on which a first plurality of LEDs is arranged; and a first encapsulant at least partially encapsulating said first side of said first substrate and said first plurality of LEDs; and wherein said second LED filament comprises: a second substrate having a first side on which a second plurality of LEDs is arranged; and a second encapsulant at least partially encapsulating said first side of said second substrate and said second plurality of LEDs.

11. The lighting device of claim 10, wherein said first encapsulant comprises a first wavelength converting material, and wherein said second encapsulant comprises a second wavelength converting material.

Description

DESCRIPTION OF THE DRAWINGS

(1) Exemplifying embodiments will now be described in more detail, with reference to the following appended drawings:

(2) FIG. 1 is a schematic illustration of a lighting device, in accordance with some embodiments;

(3) FIG. 2 shows schematic views of an extended first LED filament and an extended second LED filament in accordance with some embodiments;

(4) FIG. 3 shows cross sections of a first LED filament and a second LED filament in accordance with some embodiments;

(5) FIG. 4 is an illustration of a first LED filament and a second LED filament in accordance with some embodiments;

(6) FIG. 5 is an illustration of a first LED filament arranged along a central axis of a volume defined by a second LED filament, in accordance with some embodiments;

(7) FIG. 6 illustrates lengthwise cross sections of an extended first LED filament and an extended second LED filament, in accordance with some embodiments;

(8) FIG. 7 shows a schematic illustration of a lighting device in accordance with some embodiments;

(9) FIG. 8 is a schematic illustration of a lighting device in accordance with some embodiments.

(10) As illustrated in the figures, the sizes of the elements and regions may be exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of the embodiments. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

(11) Exemplifying embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments are shown. The 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 provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

(12) With reference to FIG. 1 a lighting device in accordance with some embodiments of the present disclosure will be described.

(13) FIG. 1 is a schematic illustration of a lighting device 100 comprising a first elongated LED filament 110, a second elongated LED filament 120, an at least partially light-transmissive envelope 130, a base 140, a controller 150 and connectors 151.

(14) In the present embodiment, the second LED filament 120 is curved to form a helix shape, which defines part of the contour of a cylindrical volume. In other embodiments, the volume may have other shapes. The first LED filament 110 is substantially straight, and is arranged within the cylindrical volume. The first LED filament extends along the elongation of the cylindrical volume, i.e. in a direction from one circular end of the cylindrical volume towards the opposite circular end of the cylindrical volume.

(15) The first and second LED filaments 110, 120 are connected to the controller 150 by means of connectors 151. Connectors 151 may comprise holding means for holding the first and second LED filaments 110, 120. Connectors 151 may comprise electrical connectors for supplying power to the first and second LED filaments 110, 120.

(16) In some embodiments, the first LED filament 110 and/or the second LED filament may be rigid. In some embodiments, the first LED filament 110 and/or the second LED filament 120 may be flexible. In certain embodiments, the first LED filament 110 may be rigid, while the second LED filament 120 may be flexible.

(17) The envelope 130 envelops the first and second LED filaments 110, 120. The envelope 130 is mounted on the base 140. The base 140 may comprise electrical connectors for connecting the lighting device 100 to a luminaire socket. The base 140 may be adapted to be connected with for example an Edison socket or a bayonet socket. The base 140 may for example comprise a cap, such as an E27 cap. The base 140 may further comprise a housing. In some embodiments, the controller 150 may be arranged within the housing.

(18) The first LED filament 110 is configured to emit light with a different color temperature than the second LED filament 120. For example, the first LED filament 110 may be configured to emit light with a higher color temperature than the second LED filament 120. For example, the first LED filament 110 may emit light with a correlated color temperature higher than 2700 K. Specifically, the LED filament 110 may be configured to emit light with a CCT which is higher than 2900 K. More specifically, the first LED filament 110 may be configured to emit light with a CCT higher than 3000 K.

(19) The second LED filament 120 may for example be configured to emit light with a CCT which is lower than 2500 K. Specifically, the second LED filament 120 may be configured to emit light with a CCT lower than 2400 K. More specifically, the second LED filament 120 may be configured to emit light with a CCT lower than 2300 K.

(20) Light emitted by the two LED filaments 110, 120 is mixed/combined to form the light emitted by the lighting device 100. The envelope 130 is at least partially light-transmissive to couple out the light emitted by the first and second LED filaments 110, 120, i.e. to transmit light outside the envelope 130. The envelope 130 has a reflectivity for wavelengths emitted by the LED filaments 110, 120 which may be less than 20%. Specifically, the reflectivity of the envelope 130 for wavelengths emitted by the LED filaments 110, 120 may be less than 15%. More specifically, the reflectivity of the envelope 130 for wavelengths emitted by the LED filaments 110, 120 may be less than 10%. For example, the envelope may be transparent.

(21) The controller 150 may be configured to control the power supply to the first LED filament 110 and the second LED filament 120 individually. Through control of the power supply of the LED filaments 110, 120, the brightness of each one of the LED filaments 110, 120 may be controlled.

(22) The ratio of power between the first LED filament 110 and the second LED filament 120 is of particular interest, as a change in the ratio of emittance between the two LED filaments 110, 120 may change the color temperature of the combined light. The controller 150 may control the color temperature of the light emitted by the lighting device 100 in a range extending from the CCT of the first LED filament 110 (no power supplied to the second LED filament) to the CCT of the second LED filament 120 (no power supplied to the first LED filament).

(23) With reference to FIG. 2, the respective lengths of the first LED filament and the second LED filament, in accordance with some embodiments, will be discussed (or compared).

(24) FIG. 2 shows a schematic view of a first LED filament 210, and a second LED filament 220. The first LED filament 210 and the second LED filament 220 may be equivalent to the first LED filament 110 and the second LED filament 120 described with reference to FIG. 1, except that both filaments have been extended to be straight so that their respective lengths may be compared. However, when arranged in a lighting device, such as the lighting device 100 described with reference to FIG. 1, at least the second LED filament 220 (and possibly both LED filaments) may be at least partially curved.

(25) The first LED filament 210 is shorter than the second LED filament 220, when they are both stretched out, i.e. not curved (or straight). The first LED filament 210 has a first LED filament length L1. The second LED filament 220 has a second LED filament length L2. For example, the second LED filament length L2 may be at least twice as long as the first LED filament length L1 (L2>2L1). Specifically, the second LED filament length L2 may be three times as long as the first LED filament length L1 (L2>3L1). More specifically, the second LED filament length L2 may be more than four times as long as the first LED filament length L1 (L2>4L1), such as five times as long (L2=5L1) or seven times as long (L2=7L1).

(26) In some embodiments, the first LED filament length L1 may be shorter than 8 cm. Specifically, the first LED filament length L1 may be shorter than 6 cm. More specifically, the first LED filament length L1 may be shorter than 5 cm.

(27) In some embodiments, the second LED filament length L2 may be longer than 10 cm. Specifically, the second LED filament length L2 may be longer than 12 cm. More specifically, the second LED filament length LED may be longer than 15 cm.

(28) With reference to FIG. 3, the respective diameters of the LED filaments, in accordance with some embodiments, will be discussed (or compared).

(29) FIG. 3 shows cross sections of the first LED filament 310 and of the second LED filament 320. The first LED filament 310 and the second LED filament 320 may be equivalent to the first LED filament 110 or 210 and the second LED filament 120 or 220 described with reference to FIG. 1 or FIG. 2, respectively.

(30) The first LED filament 310 has a larger diameter than the second LED filament 320. Specifically, the first LED filament 310 has a first LED filament diameter D1 and the second LED filament has a second LED filament diameter D2. The first LED filament diameter D1 may for example be twice as large as the second LED filament diameter D2 (D1>2D2). Specifically, the first LED filament diameter D1 may be three times as large as the second LED filament diameter D2 (D>3D2). More specifically the first LED filament diameter D1 may be four times as large as the second LED filament diameter D2 (D1>4D2), such as for example five times as large (D=5D2) or seven times as large (D1=7D2).

(31) In some embodiments, the first LED filament diameter D1 may be larger than 7 mm. Specifically, the first LED filament diameter D1 may be larger than 9 mm. More specifically, the first LED filament diameter D1 may be larger than 10 mm.

(32) In some embodiments, the second LED filament diameter D2 may be smaller than 7 mm. Specifically, the second LED filament diameter D2 may be smaller than 6 mm. More specifically, the second LED filament diameter D2 may be smaller than 5 mm.

(33) With reference to FIG. 4, the curvature of the LED filaments, in accordance with some embodiments, will be discussed (or compared).

(34) FIG. 4 is an illustration of a first LED filament 410 and a second LED filament 420. The first and second LED filaments 410, 420 may be equivalent to their counterparts described with reference to the previous figures.

(35) The first LED filament 410 is less curved than the second LED filament 420. Specifically, the first LED filament 410 is substantially straight. The second LED filament 420 is longer than the first LED filament 410 and the second LED filament 420 is arranged to form a helix shape. The helix shape defines part of a contour of a cylindrical volume 421. The helix shape has a central axis A. When arranged in a lighting device, such as the lighting device 100 described above with reference to FIG. 1, the first LED filament 410 may be arranged at least partially within the volume or space 421. More specifically, the first LED filament 410 may be arranged along the central axis A.

(36) The helix shape of the second LED filament 420 is one option among others. The second LED filament 420 may be at least partially curved to define (at least part of the contour of) any other volume in which the first LED filament 410 may be at least partially arranged. For example, the second LED filament 420 may have a curved shape defining part of a contour of a spherical volume, a conical volume etc.

(37) With reference to FIG. 5, an arrangement of LED filaments in accordance with some embodiments will be described.

(38) FIG. 5 shows two different views of an arrangement of a first LED filament 510 and a second LED filament 520 in accordance with some embodiments: one side view and one view along the central axis A (top view).

(39) The first LED filament 510 is substantially straight, and may be equivalent to any of the first LED filaments 110-410, described with reference to FIGS. 1-4. The second LED filament 520 forms a helix (spiral, coil) shape, and may be equivalent to any of the second LED filaments 120-420 described with reference to the FIGS. 1-4.

(40) The first LED filament 510 is arranged along the central axis A of the helical shape formed by the second LED filament 520.

(41) With reference to FIG. 6, the structure of the first and second LED filaments will be described.

(42) FIG. 6 shows a cross section of a first LED filament 610 and a cross section of a second LED filament 620, in accordance with some embodiments. For illustrative purposes, both LED filaments are shown as straight, however, as may be understood by the rest of the description and the claims, at least the second LED filament (and possibly both LED filaments) may be at least partially curved when arranged in a lighting device.

(43) The first LED filament 610 comprises a first substrate 612 having a first side 615. On the first side 615, a first plurality of LEDs 613 is arranged. A first encapsulant 614 encapsulates at least part of the first side 615 and the plurality of LEDs 613. The second LED filament 620 comprises a second substrate 622 having a first side 625. A second plurality of LEDs 623 is arranged on the first side 625. A second encapsulant 624 encapsulates at least part of the first side 625 and the plurality of LEDs 623.

(44) Each of the substrates 612, 622 may be light-transmissive. Specifically, the substrates 612, 622 may be transparent.

(45) The first substrate 612 may be a rigid substrate. The second substrate 622 may be a flexible substrate, such that it may be curved. For example, the second substrate 622 may be a foil.

(46) The first plurality of LEDs 613 may be arranged in one or more linear arrays on the first side 615 of the substrate 612. The LED pitch P1 (i.e. distance between successive LEDs) may be constant along the length of the LED filament 610, or vary. The first plurality of LEDs 613 may comprise LEDs which are configured to emit ultraviolet light, i.e. with a wavelength peak in the ultraviolet range 365-380 nm. The first plurality of LEDs 613 may comprise LEDs which are configured to emit blue light, i.e. with a peak wavelength in the range 435-500 nm. The first plurality of LEDs 613 may comprise one type of LEDs or more than one type of LEDs, such as blue LEDs and/or UV LEDs.

(47) The second plurality of LEDs 623 may be arranged in one or more linear arrays on the first side 625 of the substrate 622. The LED pitch P2 may be constant along the length of the LED filament 620, or vary. The second plurality of LEDs 623 may comprise LEDs which are configured to emit ultraviolet light, i.e. with a wavelength peak in the ultraviolet range 365-380 nm. The second plurality of LEDs 623 may comprise LEDs which are configured to emit blue light, i.e. with a peak wavelength in the range 435-500 nm. The second plurality of LEDs 623 may comprise one type of LEDs or more than one type of LEDs, such as blue LEDs and/or UV LEDs.

(48) The first LED filament 610 (i.e. the first plurality of LEDs 613) may comprise the same kinds/types of LEDs as the second LED filament 620 (the second plurality of LEDs 623). Alternatively, the first LED filament 610 and the second LED filament 620 may comprise different kinds of LEDs. For example, one of the LED filaments 610, 620 may comprise one type of LEDs, and the second one of the LED filaments 610, 620 may comprise the same type of LEDs and some other type of LEDs.

(49) The first encapsulant 614 may comprise a silicone material. The first encapsulant 614 may encapsulate the first side 615 and the plurality of LEDs 613. In the present embodiment, the encapsulant 614 encapsulates the entire substrate 612 (i.e. all sides of the substrate 612) and the full plurality of LEDs 613.

(50) The first encapsulant 614 may comprise a first wavelength converting material, configured to absorb at least some light emitted by the plurality of LEDs 613, and to emit light with a different peak wavelength. Such a wavelength converting material may comprise a luminescent material. For example, the wavelength converting material may comprise a red phosphor, for converting light emitted by the LEDs 613 to red light. Alternatively, or additionally, the first wavelength converting material may comprise a green/yellow phosphor, for providing green/yellow converted light.

(51) The second encapsulant 624 may comprise a silicone material. The second encapsulant 624 may encapsulate the first side 625 of the second substrate 622 and the plurality of LEDs 623. In the present embodiment, the encapsulant 624 encapsulates the entire substrate 622 (i.e. all sides of the substrate 622) and the full plurality of LEDs 623.

(52) The encapsulant 624 may comprise a second wavelength converting material, configured to absorb at least some light emitted by the plurality of LEDs 623, and to emit light at a different peak wavelength, i.e. with a different color. Such a wavelength converting material may comprise a luminescent material. For example, the wavelength converting material may comprise a red phosphor, for converting light emitted by the LEDs 623 to red light. Alternatively, or additionally, the second wavelength converting material may comprise a green/yellow phosphor, for providing green/yellow converted light.

(53) Further, the first and/or the second encapsulant 614,624 may comprise light scattering material. Specifically, in embodiments in which an encapsulant (first 614 and/or second 624) does not comprise any wavelength converting material, that encapsulant 614, 624 may comprise light scattering material. Light scattering material may, for example, comprise barium sulfate (BaSO.sub.4), aluminum oxide (Al.sub.2O.sub.3), and/or titanium dioxide (TiO.sub.2) particles.

(54) In other embodiments, the first LED filament 610 may comprise a second side which is opposite to the first side 615. A third plurality of LEDs may be arranged on the second side. The third plurality of LEDs may be arranged on the second side in a similar way as the first plurality of LEDs 613 is arranged on the first side 615. The third plurality of LEDs may be covered with an encapsulant like the encapsulant 614. The second side of the first LED filament 610 may also be covered/encapsulated by an encapsulant, such as the encapsulant 614.

(55) Further, the second LED filament 620 may comprise a second side which is opposite to the first side 625. A fourth plurality of LEDs may be arranged on the second side. The fourth plurality of LEDs may be arranged on the second side in a similar way as the first plurality of LEDs 623 is arranged on the first side 625. The fourth plurality of LEDs may be covered with an encapsulant like the encapsulant 624. The second side of the second LED filament 620 may also be covered/encapsulated by an encapsulant, such as the encapsulant 624.

(56) With reference to FIG. 7, a lighting device in accordance with some embodiments will be described.

(57) FIG. 7 shows an embodiment of a lighting device 700. The lighting device 700 may be equivalent to the lighting device 100, except that the second LED filament 720 is curved differently, defining a different volume. Specifically, the second LED filament 720 has a helical shape which has a diameter that is wider at the middle and tapers towards the ends, such that the volume which is at least partially defined by the second LED filament 720 may be described as a bicone. In other words, the diameter of the turns of the cylinder increases from the first turn/loop to the middle turn/loop, then the diameter decreases from the middle loop to the final loop. Thus, the first and last turns have smaller diameters than the intermediate turns/loops.

(58) With reference to FIG. 8, a lighting device in accordance with some embodiments will be described.

(59) FIG. 8 shows an embodiment of a lighting device 800. The lighting device 800 may be equivalent to the lighting device 100, except that the first LED filament 810 and the second LED filament 820 are arranged with a different orientation within the envelope 130.

(60) As the lighting device 100 in FIG. 1, the lighting device 800 of the present embodiment comprises an at least partially light-transmissive envelope 130 which is mounted on a base 140, and a controller 150. The base 140 defines a plane on which the controller 150 is arranged.

(61) In the present embodiment, the second LED filament 820 forms a helix shape defining a cylindrical volume. The second LED filament 820 is arranged within the envelope such that the central axis A of the cylindrical volume, defined at least in part by the second LED filament 820, extends substantially parallel to the plane defined by the base 140, instead of extending away (at an angle) from the base (as shown in FIG. 1). The first LED filament 810 is arranged along the central axis A of the volume defined (at least in part) by the second LED filament 820. Connectors 851 connect the LED filaments 810, 820 to the controller 150.

(62) 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.

(63) Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements.

(64) Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements, and the indefinite articles “a” and “an” do not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.