Patent Application
20240060612
The present invention generally relates to lighting arrangements comprising one or more light emitting diodes. More specifically, the lighting arrangement is related to a light emitting diode (LED) filament lamp configured to provide an appearance of a candle light during operation of the LED filament lamp.
The use of light emitting diodes (LED) for illumination purposes continues to attract attention. Compared to incandescent lamps, fluorescent lamps, neon tube lamps, etc., LEDs provide numerous advantages such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy. However, the light generated by LED lamps as well as incandescent lamps may, for some applications, appear static, “cold” and/or unattractive.
Candles, on the other hand, are able to generate light which is highly attractive and appealing. Light emitted from the open flame of a candle may, compared to light emitted from LEDs and/or incandescent lamps, appear more vivid, “warm”, aesthetic and/or romantic. However, one of the major disadvantages of the use of candles is the risk of fire associated with an open flame.
Hence, it is an object of the present invention to try to overcome the respective disadvantages of candles, on the one hand, and light emitted from LEDs, on the other hand, by exploring the possibility of combing one or more of the respective advantages of candle light and LED lighting devices.
In CN 106678730 a filament is disclosed with two parallel positioned arrays of LEDs that can be individually controlled. The two arrays of LEDs are of different color and therewith the color temperature of the filament can be controlled.
Hence, it is of interest to explore the possibility of combining one or more of the numerous advantages of LED lighting devices with the attractiveness and the appealing properties of light emitted from a candle.
This and other objects are achieved by providing a LED filament lamp having the features in the independent claim. Preferred embodiments are defined in the dependent claims.
Hence, according to the present invention, there is provided a light emitting diode, LED, filament lamp, comprising at least one LED filament having a base portion and a top portion extending over a length, L, along a longitudinal axis, A. The LED filament comprises an array of a plurality of LEDs, extending along the longitudinal axis A, and an encapsulant at least partially enclosing the plurality of LEDs, wherein the encapsulant comprises a luminescent material. In case, the LED filament is either curved or flexible, the longitudinal axis is to be interpreted as following the array of LEDs in the filament. The linear array of LEDs comprises a plurality N of blue LEDs emitting blue light and a plurality of M red LEDs emitting red light, such that the linear array of LEDs comprises a density of blue LEDs and a density of red LEDs, wherein the density of blue LEDs decreases and/or the density of red LEDs increases from the base portion to the top portion along at least a portion of the length (L). As a consequence, the color temperature, CTL, of the light emitted from the at least one LED filament decreases from the base portion to the top portion over at least a portion of the length of the at least one LED filament.
Thus, the present invention is based on the idea of providing a LED filament lamp wherein the appearance of the LED filament(s) of the LED filament lamp and/or the light emitted from the LED filament lamp during its operation may resemble or mimic that of a candle. Furthermore, by the features of the LED filament lamp, the lamp is furthermore able to combine one or more of the numerous advantages of LED lighting devices with the attractiveness and the appealing properties of light emitted from a candle.
The present invention is advantageous in that properties of the LED filament(s) of the LED filament lamp may lead to a generation of light which may resemble or mimic the relatively vivid, “warm”, aesthetic and/or romantic light of an open flame of a candle.
The present invention is further advantageous in that the LED filament lamp may combine the aesthetic features of candle light with the incontestable safety of operating an electric light compared to that of a light source having an open flame.
The present invention is further advantageous in that the LED filament lamp has a much longer operational life compared to that of a candle. Hence, it is much more convenient and/or cost-efficient to operate a LED filament lamp instead of a candle.
It will be appreciated that the LED filament lamp of the present invention furthermore comprises relatively few components. The low number of components is advantageous in that the LED filament lamp is relatively inexpensive to fabricate. Moreover, the low number of components of the LED filament lamp implies an easier recycling, especially compared to devices or arrangements comprising a relatively high number of components which impede an easy disassembling and/or recycling operation.
The LED filament lamp comprises at least one LED filament. The at least one LED filament, in its turn, comprises an array of LEDs. By the term “array”, it is here meant a linear arrangement or chain of LEDs, or the like, arranged on the LED filament(s). Under linear arrangement it is understood that the LEDs are connected in a linear way, this does not mean that the LEDs are arranged in a one dimensional array on the substrate; deviating forms may occur, like e.g. an array having a width of two LEDs (as shown in
It is the insight of the present invention that when the array of LEDs comprises relatively more blue LEDs at the base portion than at the top portion, or when the array of LEDs comprises relatively more red LEDs at the top portion than at the base portion.
Consequently, the color temperature of the light emitted from the at least one LED filament may decrease in a direction from the base portion to the top portion at least along the portion of the LED filament. The present embodiment is advantageous in that the decrease of the color temperature of the light emitted from the LED filament(s) may resemble that of a candle light.
This objective can be realized by an array of LEDs with a sequence of blue (B) and red (R) LEDs, which sequence has at the base portion relatively more blue LEDs (B) than at the top portion, or alternatively, at the top portion relatively more red LEDs (R) than at the base portion. For instance, the sequence of the LEDs on a filament—as seen from base portion to top portion—may be: B-B-B-R-B-B-R-B-R-B-R-B . . . , here the number of blue LEDs diminishes and after each section with blue LEDs there is one red LED, so from base portion to top portion, the emitted light will become more reddish showing a lower color temperature.
Each block of a certain number of blue and red LEDs, until the next blue LED is referred to as sub-sequence. The example given above starts with the sub-sequence B-B-B-R, followed by the sub-sequence B-B-R, then B-R, B-R, B . . . . The same holds when the sequence of LEDs starts with a red LED at the bottom portion; in that case a sub-sequence is a block of a certain number of red and blue LEDs, until the next red LED.
As an alternative, with the same result, the sequence can read e.g. B-B-B-R-B-B-B-R-R-B-B-B-R-R-R-, Many more arrangements of the red and blue LEDs are possible, as long as they are arranged in such a way that a gradual decrease of color point is realized from the base portion to the top portion of the LED filament.
The word gradual in the context of the present invention should be interpreted that the color emitted from the LED filament changes in a smooth and natural way from more blueish to more reddish when going from the bottom portion to the top portion. This effect is observed at some distance from the LED filament when the light of the individual LEDs is mixed—for instance by the use of a diffusing layer on the encapsulant—is such a way that the individual colors of the LEDs are not predominantly observable.
Some more arrangements of the sequence of the LEDs on the LED filament according to the invention are given in Table 1. The LEDs may form a subset of LED of the total set of LEDs in the linear array of LEDs according to one or more of the following examples.
In an embodiment of the invention the number of neighboring LEDs with the same annotation is less or equal to 4 (i.e. maximum 4 neighboring blue LEDs B and maximum 4 neighboring red LEDs R).
In an embodiment of the invention the linear array of LEDs comprises at least one blue LED neighbored on both sides by red LEDs (i.e. -R-B-R-), at least one sequence of two blue LEDs neighbored on both sides by red LEDs (i.e. -R-B-B-R-), and at least one sequence of three blue LEDs neighbored on both sides by red LEDs (i.e. -R-B-B-B-R-).
In an embodiment of the invention the linear array of LEDs comprises at least one red LED neighbored on both sides by blue LEDs (i.e. -B-R-B-), at least one sequence of two red LEDs neighbored on both sides by blue LEDs (i.e. -B-R-R-B-), and at least one sequence of three red LEDs neighbored on both sides by blue LEDs (i.e. -B-R-R-R-B-).
According to an embodiment of the present invention, a first section of the at least one LED filament is defined between the base portion and an intermediate portion of the at least one LED filament. A second section of the at least one LED filament is defined between the intermediate portion and the top portion of the at least one LED filament. At least one of the density of the blue LEDs decreases and the density of the red LEDs increases along the first section and may remain constant along the second section. Consequently, the color temperature of the light emitted from the at least one LED filament may decrease along the first section in a direction from the base portion to the intermediate portion, and may remain constant along the second section. Hence, the light emitted from the LED filament(s) has a relatively high color temperature, although decreasing, between the base portion and the intermediate portion of the LED filament(s). In relation, the light emitted from the LED filament(s) has a lower, constant color temperature between the intermediate portion and the top portion of the LED filament(s). The present embodiment is advantageous in that the LED filament(s) hereby may, to an even further extent, mimic or resemble the light emitted from an open flame.
According to an embodiment of the present invention, the first section of the at least one LED filament may be shorter than the second section of the at least one LED filament. It will be appreciated that the LED filament(s) may mimic the appearance and/or properties of a wick of a candle. The present embodiment is advantageous in that the configuration may even further contribute to the generation of light from the LED filament lamp which may resemble that of candle light.
According to an embodiment of the present invention, in the LED filament lamp the LEDs in the array of LEDs are separated by a certain distance, the pitch, and in this embodiment they are arranged at a constant pitch P. Therewith, the differences in the density of the blue and/or red LEDs will be realized by changing the relative number of red and blue LEDs in order to obtain a decreasing color temperature from the base portion to the top portion.
As an alternative embodiment of the present invention the LEDs in the array of LEDs (140) having a pitch P wherein said pitch increases for the blue LEDs and/or decrease for the red LEDs from the base portion to the top portion over at least a portion of the length of the at least one LED filament. I this embodiment the differences in the density of for instance the Blue LEDs is realized by increasing the pitch of the blue LEDs from the base portion to the top portion, therewith reducing the amount of blue light emitting from the LED filament and as a consequence the color temperature will decrease.
The same effect can be realized by decreasing the pitch of the red LEDs when going from base portion to top portion. This leads to a higher red-light output towards the top portion and as a consequence a lower color temperature.
Additionally, in case the pitch of the blue and/or red LEDs is varied over the length of the filament, it may be necessary to adapt the drive current to the blue and red LEDs in order to keep the overall light output on the same level.
According to an embodiment of the present invention, the LED filament the number of blue LEDs N is at least 10, and also the number of red LEDs M is at least 10. With these numbers of LEDs their mutual spacing (pitch) is small enough to realize a smooth light distribution over the filament. Even more preferred is a LED filament in which the number of blue LEDs is larger than 1.3 times the number of red LEDs. This ratio between blue and red light emitting LEDs enables a preferred color temperature distribution for mimicking the desired a candle type of lamp.
In a further embodiment, the LED filament lamp is provided with a luminescent material that converts at least a part of the blue light into converted light, preferably said converted light is green and/or yellow light. This enables the realization of a candle type of filament lamp with a more natural color impression.
According to an embodiment of the present invention, the LED filament lamp may further comprise a diffusor element. The diffusor element may at least partially enclose the at least one filament and be arranged to diffuse the light emitted from the at least one filament. By the term “diffusor element”, it is here meant a diffusing layer and/or an element which possesses properties for diffusing light. For example, the “diffusor element” may be a light guide which is translucent e.g. by surface roughness or scattering.
The present embodiment is advantageous in that the diffusor element may contribute to an emission of light from the LED filament lamp which, to an even further extent, may resemble that of a candle.
According to an embodiment of the present invention, the LED filament lamp may further comprise a control unit coupled to the at least one LED filament and be configured to control the power supply of the at least one LED filament. By the term “control unit” it is hereby meant a device, arrangement, element, or the like, which is configured to control the power supply to the LED filament(s). It will be appreciated that the control of the control unit furthermore may be performed according to one or more predetermined settings. By the term “predetermined setting”, it is hereby meant a setting, setup, program, relationship, or the like, which is set or determined in advance. The control unit may hereby control the power supply, and consequently, the color temperature of the light emitted from the LED filament(s) as a function of this or these predetermined setting(s).
In a further example, the control unit may be configured to individually control an operation of each LED of the plurality of LEDs.
According to an embodiment of the present invention, the LED filament lamp may comprise at least two LED filaments, wherein the control unit may be configured to individually control the power supply to the at least two LED filaments and to individually control the operation of each LED of the plurality of LEDs of each LED filament. The present embodiment is advantageous in that the control unit may operate the power supply to the LED filaments and control the operation of each LED such that an even more “vivid” light is emitted from the LED filaments, which may resemble light from an open flame candle.
According to an example of the present invention, the LED filament lamp may comprise at least two LED filaments arranged in parallel along the longitudinal axis. The present embodiment is advantageous in that the present arrangement of LED filaments may, to an even further extent, lead to an emission of light from the LED filaments which may have appearance and the aesthetically appealing properties of candle light.
According to an example of the present invention, the LED filament lamp may comprise three LED filaments arranged in parallel along the longitudinal axis. The three LED filaments may further be grouped such that in a cross-section, parallel to the transverse axis, each LED filament is arranged on a respective corner of a triangle.
According to an example of the present invention, the LED filament lamp may comprise at least two LED filaments, wherein the lengths of at least two of the at least two LED filaments may differ from each other. The present embodiment is advantageous in that the arrangement of LED filaments as exemplified may lead to an emission of light from the LED filaments which may resemble candle light.
According to an example of the present invention, the LED filament lamp may comprise at least two LED filaments, wherein at least two of the at least two LED filaments may be shifted with respect to each other along the longitudinal axis. In other words, the plurality of LED filaments, arranged in a parallel, may be shifted with respect to each other.
According to an embodiment of the present invention, the LED filament lamp may comprise at least two LED filaments. The color temperature CTL1 of the light emitted from the at least one first LED filament may differ, at least along a portion thereof along the longitudinal axis, from the color temperature CTL2 of the light emitted from the at least one second LED filament. The present embodiment is advantageous in that the ability of the LED filament lamp to vary the color temperature with respect to different LED filaments may contribute to the appearance and the aesthetically appealing properties of candle light.
According to an embodiment of the present invention, the color temperature of the light emitted from the at least one LED filament may vary along the length of the at least one LED filament in the range of 5000 K to 1500 K, more preferably 4000 K to 1700 K, and most preferred 2700 K to 1900 K. In combination herewith, or according to another embodiment of the present invention, the color rendering index of the light emitted from the LED filament lamp may be at least 70, preferably at least 75, and even more preferred 80.
Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.
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.
The LED filament 120 further comprises a substrate 130a of elongated shape for supporting the plurality of LEDs 140. For example, the plurality of LEDs 140 may be arranged, mounted and/or mechanically coupled to the substrate 130. The LED filament 120 further comprises an encapsulant (shown in
The encapsulant comprises a luminescent material. For example, the luminescent material may comprise a fluorescent material, an inorganic phosphor, an organic phosphor, and/or quantum dots/rods. The encapsulant may furthermore, or alternatively, comprise a polymer material, for example a silicone.
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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. For example, one or more of the LED filament(s) 120, etc., may have different shapes, dimensions and/or sizes than those depicted/described.
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| Number | Date | Country | Kind |
|---|---|---|---|
| 19203452.8 | Oct 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/077909 | 10/6/2020 | WO |
