SOLID STATE LAMP

Abstract

The present invention relates to a lamp (1), comprising a lamp base (3), a semi-reflective envelope (2), at least one first solid state light source filament (4a-d) arranged inside the semi-reflective envelope (2), and a second solid state light source (5) arranged inside the semi-reflective envelope (2), wherein the reflectivity of the semi-reflective envelope (2) is in the range from 30% to 70% for light emitted by the at least one first solid state light source filament (4a-d) and the second solid state light source (5), wherein the at least one first solid state light source filament (4a-d) is arranged at a first distance lower than 7 millimeters from the semi-reflective envelope (2), and wherein the second solid state light source (5) is arranged at second distance higher than 15 millimeters from the semi-reflective envelope (2).

Claims

1. A lamp, comprising: a lamp base; a semi-reflective envelope; at least one first solid state light source filament arranged inside the semi-reflective envelope; and a second solid state light source arranged inside the semi-reflective envelope, wherein the reflectivity of the semi-reflective envelope is in the range from 30% to 70% for light emitted by the at least one first solid state light source filament and the second solid state light source, wherein said at least one first solid state light source filament is arranged at a first distance lower than 7 millimeters from the semi-reflective envelop, and wherein said second solid state light source is arranged at a second distance higher than 15 millimeters from the semi-reflective envelop.

2. The lamp according to claim 1, wherein said at least one first solid state light source filament is at least one LED filament, and wherein said second solid state light source is a non-filament LED light source.

3. The lamp according to claim 1, wherein said lamp has a longitudinal axis, and wherein said second solid state light source is arranged at said longitudinal axis.

4. The lamp according to claim 1, wherein said second solid state light source is a color temperature and/or color tunable light source.

5. The lamp according to claim 1, wherein said first distance is in the range of 0 to 2 mm.

6. The lamp according to claim 1, wherein said first distance is in the range of 3 to 7 mm (that is 3<D1<7 mm).

7. The lamp according to claim 1, wherein the shape of said at least one first solid state light source filament is at least partly matching the shape of said semi-reflective envelope.

8. The lamp according to claim 7, wherein the at least one first solid state light source filament at least partly follows a curvature of the semi-reflective envelope as seen in a longitudinal plane of the lamp.

9. The lamp according to any of claim 1, wherein the at least one first solid state light source filament has the shape of a helix with at least three turns.

10. The lamp according to any of claim 1, wherein the at least first solid state light source filament covers at least 50% of the length of the semi-reflective envelope as seen in a longitudinal plane of the lamp.

11. The lamp according to any of claim 1, wherein the at least one first solid state light source filament is configured to emit light of a first color temperature, and wherein the second solid state light source is configured to emit light of a second color temperature different than the first color temperature.

12. The lamp according to any of claim 1, further comprising a controller configured to control the at least one first solid state light source filament and the second solid state light source—such that at a total luminous flux below a total luminous flux threshold only the at least one first solid state light source filament emits light, and such that at a total luminous flux on or above the total luminous flux threshold both the at least one first solid state light source filament and the second solid state light source emit light.

13. The lamp according to claim 12, further configured such that at a total luminous flux above said total luminous flux threshold, said second solid state light source provides more light than said at least one first solid state light source filament.

14. The lamp according to claim 12, wherein said total luminous flux threshold is in the range of 300 to 500 lm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] As illustrated in the figures, some features including portions of the semi-reflective envelope or the LED filament maybe exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.

[0035] FIGS. 1a-b respectively show schematic side and cross sectional views of a solid state lamp in accordance with at least one embodiment of the present invention.

[0036] FIG. 2 shows a schematic side view of a solid state lamp in accordance with at least one other embodiment of the present invention.

[0037] FIGS. 3a-d show schematic side views of a solid state lamps in accordance with further embodiments of the present invention;

[0038] FIGS. 4a-c show exemplary operations of the lamp according to various embodiments of the present invention.

[0039] FIG. 5 is a schematic side view of a lamp according to yet another embodiment of the present invention.

DETAILED DESCRIPTION

[0040] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently 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 provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

[0041] FIGS. 1a-b illustrate a lamp 1 according to an embodiment of the invention. The lamp 1 is intended to have a look of an incandescent light bulb which is found to be highly appreciated by the viewers. The lamp 1 may be referred to as a retrofit lamp or an LED bulb or a filament LED bulb.

[0042] The lamp 1 comprises a lamp base 3. The lamp base 3 may also be referred to as a cap or cap base. The lamp base 3 is adapted to mechanically and electrically connect the lamp 1 to a lamp socket (not shown). The lamp base 3 may for example be a screw base.

[0043] The lamp 1 further comprises a semi-reflective envelope 2. The semi-reflective envelope 2 is connected to the lamp base 3, either directly or via an intermediate member. The semi-reflective envelope 2 may for example have a “straight-tubular” bulbshape as in FIG. 1a (e.g. ST64), though other shapes are possible as well. The height of the lamp 1 (envelope+base) may for example be about 14 cm, and the maximum width may be 6.4 cm.

[0044] The lamp 1 further comprises at least one first solid state light source filament, here four LED filaments 4a-d. Each LED filament 4a-d may comprise a substrate having an elongated body, and a plurality of LEDs mechanically coupled to the substrate. The LED filaments 4a-d may for example be adapted to emit white light. The white light is preferably within 12 SDCM from the BBL (Standard Deviation Colour Matching from the Black Body Locus), more preferably <10, most preferably <7. The white light has preferably a color temperature in the range from 2000 K to 8000 K, more preferably 2100 K to 5000 K, most preferably 2200 K to 4000 K. The CRI (Color Rendering Index) is preferably at least 70, more preferably at least 80, most preferably at least 85 such as for example 88 or 92. The LED filaments 4a-d are here straight, generally upright oriented, slightly tilted relative to the longitudinal axis 6 of the lamp 1, and parallel to the (frusto-conical portion) of the semi-reflective envelope 2. As can be seen in FIG. 1b, the LED filaments 4a-d are evenly distributed along the circumference of the semi-reflective envelope 2. Because the LED filaments 4a-d are not positioned on the central longitudinal axis 6 and the semi-reflective envelope 2 is a mixing chamber, light—in operation—is impinging on the inner surface of the semi-reflective envelope 2 from several angles. Please not that in FIG. 1a only LED filaments 4a and 4c are shown for brevity.

[0045] Within the context of the present invention, a LED filament is providing LED filament light and comprises a plurality of light emitting diodes (LEDs) arranged in a linear array. Preferably, the LED filament has a length L and a width W, wherein L>5W. The LED filament may be arranged in a straight configuration or in a non-straight configuration such as for example a curved configuration, a 2D/3D spiral or a helix. Preferably, the LEDs are arranged on an elongated carrier like for instance a substrate, that may be rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) or flexible (e.g. made of a polymer or metal e.g. a film or foil).

[0046] In case the carrier comprises a first major surface and an opposite second major surface, the LEDs are arranged on at least one of these surfaces. The carrier may be reflective or light transmissive, such as translucent and preferably transparent.

[0047] The LED filament may comprise an encapsulant at least partly covering at least part of the plurality of LEDs. The encapsulant may also at least partly cover at least one of the first major or second major surface. The encapsulant may be a polymer material which may be flexible such as for example a silicone. Further, the LEDs may be arranged for emitting LED light e.g. of different colors or spectrums. The encapsulant may comprise a luminescent material that is configured to at least partly convert LED light into converted light. The luminescent material may be a phosphor such as an inorganic phosphor and/or quantum dots or rods.

[0048] The LED filament may comprise multiple sub-filaments.

[0049] The lamp 1 further comprises a second light source 5, here a non-filament LED light source. The LED light source 5 may for example be an LED package. The LED light source 5 may for example be adapted to emit white light. The LED light source 5 is here arranged at (on) the central longitudinal axis 6. Furthermore, the LED light source 5 may be positioned in level with the LED filaments 4a-d, as seen along the longitudinal axis 6.

[0050] The lamp 1 may further comprise a controller 7 generally adapted to control the light output of the LED filaments 4a-d and the LED light source 5.

[0051] The reflectivity of the semi-reflective envelope 2 is in the range from 30% to 70% for light emitted by the at least one first solid state light source filament 4a-b and the second solid state light source 5. The semi-reflective envelope 2 may be, or act as, a diffuser configured to diffuse light. The semi-reflective envelope 2 can for example be made of clear glass provided with a coating to achieve the desired reflectivity. The coating may for example be a light scattering coating on the inside of the envelope 2. For example, a polymer matrix (e.g. of silicone, PMMA, PC, PET) comprising scattering particles (silicone, TiO.sub.2, BaSO.sub.4, and/or Al.sub.2O.sub.3 particles) or (air) bubbles may be used. Alternatively or complementary, the semi-reflective envelope 2 itself may be scattering. At an exemplary reflectivity of 50%, half of the light from the LED filaments 4a-d and the LED light source 5 is reflected by the semi-reflective envelope 2. Of the rest, most light is transmitted through the semi-reflective envelope 2, whereas some is absorbed by the semi-reflective envelope 2.

[0052] The LED filaments 4a-d are arranged at a first distance D1 from the semi-reflective envelope 2. The first distance D1 may be defined as a radial distance relative to the longitudinal axis 6 and/or as the minimum distance between the filament 4 and the envelope 2 measured perpendicular to the longitudinal axis 6. The first distance D1 is preferably <7 mm. That distance together with the above-discussed reflectivity enables projection of the LED filaments 4a-b onto the semi-reflective envelope 2 and thus the LED filament 4a-b are visible for a person. Specifically, in FIG. 1b, LED filament 4a is visible to person P. If the first distance D1 is in the range of 0 to 2 mm, cooling of the at least one first solid state light source filament can be improved. If the first distance D1 is in the range of 3 to 7 mm (3<D1<7 mm), homogenous lighting may be improved. Preferably the complete (or substantially the complete) at least one LED filament 4a-d is closer to the semi-reflective envelope 2 than 7 mm. In other words, D1, i.e. the minimum distance between the at least one LED filament 4a-d and the envelope 2 measured perpendicular to the longitudinal axis 6, is less than 7 mm at any point along the length of the at least one LED filament 4a-d. In FIG. 1a, the first distance D1 to the most adjacent point on the semi-reflective envelope 2 is constant throughout the length of the LED filaments 4a-d.

[0053] The LED light source 5 is arranged at a second distance D2 from the semi-reflective envelope 2. The second distance D2 may be defined as a radial distance relative to the longitudinal axis 6 and/or as the minimum distance between the filament 4 and the envelope 2 measured perpendicular to the longitudinal axis 6. The second distance D2 is preferably >15 mm. That distance together with the above-discussed reflectivity makes the LED light source 5 invisible for the person, whereby glare may be prevented.

[0054] FIG. 2 illustrates a lamp 1 according to another embodiment of the invention. This lamp 1 is similar to the lamp in FIGS. 1a-b, except that the second solid state light source 5 is a color tunable light source. The color tunable light source 5 may for example comprise at least one red LED “R”, at least one green LED “G”, and at least one blue LED “B”. The red, green, and blue LEDs could be individually controlled by the controller 7, whereby a color controllable LED filament lamp 1 may be provided.

[0055] FIGS. 3a-b illustrate lamps 1 according to further embodiments of the invention. These lamps may be similar to the lamp in FIGS. 1a-b, except that the LED filaments 4a-d at least partly follow a curvature of the semi-reflective envelope 2, as seen in a longitudinal plane of the lamp 1 (i.e. the plane of the paper or screen where you are viewing these figures). In FIG. 3a, the top portion 8 of each LED filament 4a-d is bent to match the dome-shaped top portion 9 of the semi-reflective envelope 2. In FIG. 3b, the complete LED filaments 4a-d are bent (curved) to match the semi-reflective envelope 2 having an A-shape. It is appreciated that the distance D1 may be constant throughout the length of the LED filaments 4a-d also in these embodiments.

[0056] In FIGS. 3c-d, the lamp 1 may be similar to the lamp in FIGS. 1a-b, except that it has at least one LED filament 4 shaped like a helix and that the semi-reflective envelope 2 is here candle-shaped. FIG. 3c is a cross-sectional view, and FIG. 3d is side view of the lamp 1 when turned on. By varying the radius of the helix-shaped at least one LED filament 4, the first distance D1 (here 0 mm) may be constant throughout the length of the at least one LED filament 4. The illustrated LED filament 4 has three and a half turns.

[0057] FIGS. 4a-c show exemplary operations of the lamp 1 according to various embodiments of the present invention, for example the lamp 1 shown in FIGS. 1a-b.

[0058] In FIG. 4a, the controller 7 is configured to control the LED filaments 4a-d and the LED light source 5 such that at a total luminous flux below a total luminous flux threshold 10 only the LED filaments 4a-d emit light (whereas the LED light source 5 is off), and such that at a total luminous flux on or above the total luminous flux threshold 10 both the LED filaments 4a-d and the LED light source 5 emit light. The total luminous flux threshold 10 may be in the range of 300 to 500 lm (lumen). Furthermore, the maximum output of the LED filaments 4a-d may be equal to the value of the total luminous flux threshold 10, as in FIG. 4a.

[0059] In FIG. 4b, the controller 7 is configured to control the LED filaments 4a-d and the LED light source 5 such that at a total luminous flux above the total luminous flux threshold 10, e.g. at or above 400 lm in case the threshold 10 is 300 lm, the LED light source 5 provides more light than the LED filament 4a-d.

[0060] In FIG. 4c, the LED filaments 4a-d and the LED light source 5 provide different color temperatures, and the controller 7 may be configured to control the LED filaments 4a-d and the LED light source 5 such that both emits light at any total luminous flux.

[0061] FIG. 5 illustrate a lamp 1 according to yet another embodiment. This lamp 1 is similar to the lamp in FIGS. 1a-b, except that is does not include the LED light source 5. Instead, it includes moving means 11 configured to move the at least one solid state light source filament 4 from a first distance d1 gradually or in steps to a second distance d2 with respect to the semi-reflective envelope.

[0062] 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. 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 or steps, and the indefinite article “a” or “an” 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 measured cannot be used to advantage.