Light emitting diode (LED)-based filament lamp and luminaire comprising at least one LED-based filament lamp

Abstract

A filament lamp based on light emitting diodes (LEDs) comprises an LED filament, and the LED filament comprises (i) a first sub-filament with a plurality of first LEDs and (ii) a second sub-filament with a plurality of second LEDs. Wherein the first sub-filament and the second sub-filament are positioned to ensure that light emitted by each of the plurality of first LEDs is respectively mixed with light emitted by any one of the plurality of second LEDs, the first sub-filament and the second sub-filament are arranged such that the combination of light emitted by the first sub-filament and light emitted by the second sub-filament is perceived as light emitted by a single filament, a first driver arranged to drive a plurality of first LEDs of the first sub-filament, a second driver different from the first driver is arranged to drive a plurality of second LEDs of the second sub-filament.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to the field of lighting, and more particularly to a light emitting diode (LED) based filament lamp comprising a plurality of LEDs arranged in a filament-like pattern. BACKGROUND

[0002] A light emitting diode, LED, based filament lamp, also known as an LED filament bulb, is a type of bulb that combines the energy efficiency and longevity of LEDs with the aesthetic appeal of a traditional incandescent filament bulb.

[0003] Unlike traditional incandescent bulbs, which use a filament wire to produce light, LED filament bulbs use a plurality of LEDs arranged in a filament-like pattern. These LEDs emit light when current passes through them, providing illumination in a similar way to traditional bulbs.

[0004] LED filament bulbs can be designed to mimic the warm glow and appearance of incandescent bulbs. The LEDs are typically housed within a clear or frosted glass enclosure, often shaped like a traditional bulb, to create a familiar and nostalgic appearance. The filament-like arrangement of the LEDs helps to distribute light more evenly and create a pleasing omnidirectional illumination.

[0005] LED filament bulbs can offer several advantages over traditional incandescent bulbs. They are highly energy efficient, consuming significantly less electricity and producing less heat. LED technology also results in these bulbs having a much longer lifespan compared to incandescent bulbs. LED filament bulbs can last tens of thousands of hours, reducing the frequency of bulb replacement and lowering maintenance costs.

[0006] Furthermore, LED filament bulbs can come in a variety of shapes, sizes, and color temperatures, allowing users to choose the right ambiance for their space. They are also compatible with standard bulb sockets, making it easy to retrofit existing fixtures with LED technology.

[0007] LED based filament bulbs typically comprise a filament containing a plurality of LEDs, and a driver responsible for powering these LEDs. If a fault condition occurs in the driver, the filament, or both, the LED based filament bulb will be considered as broken. SUMMARY

[0008] It would be advantageous to implement an LED based filament bulb designed such that it will still work to some extent even when a fault condition occurs in the driver or the filament.

[0009] It would also be advantageous to implement a luminaire comprising such an LED based filament bulb.

[0010] In a first aspect of the present disclosure, there is provided a light emitting diode, LED, based filament lamp, comprising:

[0011] An LED filament, comprising:

[0012] (i) a first sub-filament having a plurality of first LEDs, and

[0013] (ii) a second sub-filament having a plurality of second LEDs,

[0014] a first driver arranged for driving the plurality of first LEDs of the first sub-filament;

[0015] a second driver, different from the first driver, arranged for driving the plurality of second LEDs of the second sub-filament.

[0016] The first sub-filament and the second sub-filament can be positioned such as to ensure that light emitted by each of the plurality of first LEDs is mixed with light emitted by any of the plurality of second LEDs, respectively, such that the combination of light emitted by the first sub-filament and light emitted by the second sub-filament is perceived as light emitted by a single filament at a target distance.

[0017] The inventors have found that it can be beneficial to create an LED-based filament lamp, wherein the LED filament is interpreted as comprising at least two sub-filaments. Both sub-filaments have a plurality of LEDs.

[0018] The basic concept is based on the insight that the first sub-filament and the second sub-filament can be positioned in such a way that a user can perceive the sub-filaments as a single filament. The user can not be able to distinguish the different sub-filaments from each other. The target distance is considered to be the distance between the LED-based filament lamp and the user during normal operation. For example, the LED-based filament lamp can be installed on a ceiling. The LED-based filament lamp can also be used for a floor lamp. Preferably, the target distance is larger than 30 cm, preferably larger than 50 cm.

[0019] To achieve this technical effect, the first sub-filament and the second sub-filament can be positioned in such a way that light emitted by each of the plurality of LEDs of the first sub-filament is mixed with corresponding light emitted by any of the plurality of second LEDs, such that the combination of light emitted by the first and second sub-filaments is perceived by the user as light emitted by a single filament.

[0020] The first driver is for driving the plurality of LEDs of the first sub-filament, and the second driver is for driving the plurality of LEDs of the second sub-filament.

[0021] After the above, if a fault condition occurs in any of the sub-filaments, that particular sub-filament can be damaged. The other sub-filament can still work properly. The result is that the user cannot see or notice the damaged sub-filament. When one of the sub-filaments has been damaged, the functionality of the LED-based filament lamp can be reduced, but the LED-based filament lamp can still work properly. For example, the total amount of lux emitted by the LED-based lighting lamp can be reduced.

[0022] After the above, if a fault condition occurs in any of the two drivers, the corresponding sub-filament can no longer work properly. This particular scenario is the same as the scenario outlined above. The user cannot see or notice the sub-filament that no longer works properly. The user will have the impression that the LED-based filament lamp works properly, although the total amount of lux or the color range can be reduced. The user cannot see the non-working sub-filament because the sub-filaments are perceived as a single filament as a whole.

[0023] One of the advantages of the present disclosure is that there is no need to replace the LED-based filament lamp in case of a fault condition. The LED-based filament lamp can still function above certain quality standards, thereby increasing the expected lifetime of the LED-based filament lamp as a whole.

[0024] In summary, in other words, the positioning of the first and second sub-filaments is arranged such that the light emitted by each LED in the first group mixes with the light emitted by any LED in the second group. As a result, the combined light from the first and second sub-filaments is perceived as if emitted by a single filament.

[0025] To ensure the above effect, the first and second sub-filaments can be strategically positioned. The LEDs in the first sub-filament can be arranged in a way that allows their emitted light to mix with the light emitted by any LED in the second sub-filament. This can be achieved by placing the LEDs of the first group close to the LEDs of the second group.

[0026] A specific arrangement can include interleaving the LEDs from the two sub-filaments such that each LED from the first sub-filament is interleaved with an LED from the second sub-filament along the length of the filament. Alternatively, the LEDs from each group can be positioned side by side, ensuring that the emitted light from adjacent LEDs in different sub-filaments overlaps and mixes.

[0027] Additionally, optical components such as diffusers or reflectors can be utilized to further enhance the mixing of light. These components help to scatter and redirect the emitted light, ensuring that it effectively interacts and merges.

[0028] By positioning the LEDs and employing appropriate optical techniques, the combined effect of the light emitted by the first and second sub-filaments creates the illusion of a single filament, resulting in a cohesive and uniform lighting appearance.

[0029] In an example, the first and second sub-filaments are arranged in parallel and adjacent to each other.

[0030] The above can require the LEDs in the two sub-filaments to be positioned side-by-side.

[0031] By arranging the sub-filaments in parallel, the LEDs in each sub-filament are aligned in a row or series, extending side-by-side from each other. This configuration ensures that light emitted from adjacent LEDs in the first sub-filament overlaps and mixes with light emitted by adjacent LEDs in the second sub-filament.

[0032] The close proximity and parallel arrangement enables the two sub-filaments to work together to produce a cohesive and uniform lighting appearance, giving the impression of a single filament.

[0033] In another example, the first sub-filament and the second sub-filament are positioned such that the maximum distance between the second sub-filament and the first sub-filament is equal to or less than 5mm, preferably equal to or less than 3mm, more preferably equal to or less than 1mm, most preferably 0mm.

[0034] The distance between the sub-filaments can affect how well light emitted by LEDs in one sub-filament mixes with light emitted by LEDs in the other sub-filament. When the sub-filaments are positioned closer together, there is a higher chance of the emitted light overlapping and interacting, resulting in better mixing. This proximity allows light from adjacent LEDs in different sub-filaments to effectively combine, resulting in a uniform and cohesive lighting appearance.

[0035] The distance between the sub-filaments can also affect the visual perception of the emitted light. By keeping the sub-filaments closer together, the human eye can perceive the combined light as if it were emitted by a single filament. This visual illusion can be important for achieving the desired effect of replicating the appearance of a traditional incandescent filament bulb.

[0036] Ensuring an appropriate distance between the sub-filaments can help to maintain the uniformity of the emitted light. If the sub-filaments are positioned too far apart, there can be gaps or inconsistencies in the lighting pattern, resulting in an uneven appearance. By minimizing the distance between the sub-filaments, the light distribution becomes more consistent, producing a smoother and more balanced illumination.

[0037] In another example, the distance from each LED in the plurality of first LEDs to an LED in the plurality of second LEDs is less than 5mm, preferably less than 3mm, more preferably equal to or less than 1mm, most preferably 0mm.

[0038] The inventors have found that it can be beneficial to ensure that the LEDs in different sub-filaments are spaced apart with a maximum distance of 5mm. Preferably, the distance between these LEDs is smaller, for example less than 3mm.

[0039] In another example, the LED-based filament lamp comprises an elongated carrier comprising a first sub-filament and a second sub-filament. Preferably, the elongated carrier can be a monolithic carrier.

[0040] The sub-filaments can be positioned on the same elongated carrier, such as a printed circuit board, PCB, or any other type of carrier. The sub-filaments can still be driven by different drivers, such that the sub-filaments are isolated from each other. In an example, the PCB can be a metal core PCB.

[0041] In another example, the first sub-filament is connected in series with the second sub-filament.

[0042] In another example, the first sub-filament is connected in parallel with the second sub-filament.

[0043] In yet another example, the filament comprises:

[0044] a first elongated encapsulant covering the plurality of first LEDs, the first elongated encapsulant comprising a first luminescent material configured to at least partially convert LED light emitted by the plurality of first LEDs into first converted light, and / or a first scattering material configured to at least partially scatter LED light emitted by the plurality of first LEDs into first scattered light; and

[0045] a second luminescent material configured to at least partially convert LED light emitted by the plurality of second LEDs into second converted light, and / or a second scattering material configured to at least partially scatter LED light emitted by the plurality of second LEDs into second scattered light.

[0046] In yet another example, the filament comprises:

[0047] a first elongated encapsulant covering the plurality of first LEDs, the first elongated encapsulant comprising a first luminescent material configured to at least partially convert LED light emitted by the plurality of first LEDs into first converted light, and / or a first scattering material configured to at least partially scatter LED light emitted by the plurality of first LEDs into first scattered light; and

[0048] a second luminescent material configured to at least partially convert LED light emitted by the plurality of second LEDs into second converted light, and / or a second scattering material configured to at least partially scatter LED light emitted by the plurality of second LEDs into second scattered light.

[0049] wherein the first elongated encapsulant is in physical contact with the second elongated encapsulant.

[0050] The inventors have found that it can be beneficial to cover the plurality of first LEDs and the plurality of second LEDs with a luminescent material and / or a scattering material. This further improves the effect that the sub-filaments are perceived as a single filament.

[0051] In another example, the second sub-filament light has a first correlated color temperature, the second sub-filament light has a second correlated color temperature, wherein .

[0052] The inventors have found that it is desirable that the first and second sub-LED filament emit (substantially) the same CCT, but that the first sub-LED filament is optimized for the first driver, while the second sub-LED filament is optimized for the second driver. For example, turning off the first driver and operating the second driver at full power allows to dim simply to 50% while operating at high efficiency. Thus, the LED-based filament lamp can receive a dimming signal, and it can be determined to turn on or turn off the first driver or the second driver depending on the dimming level. Preferably, the first driver is disabled when the dimming signal is below a threshold value, while the second driver is kept active. In the disabled case, it is understood that the power stage of the driver is turned off such that no power can be provided to the corresponding sub-filament, while the driver only consumes a very small standby power.

[0053] In an example, the first and second luminescent material can be the same, e.g. in terms of phosphor composition and / or phosphor concentration.

[0054] In another example, the second sub-filament light has a first correlated color temperature, the second sub-filament light has a second correlated color temperature, wherein .

[0055] In an example, the first and second luminescent material can be different, e.g. in terms of phosphor composition and / or phosphor concentration.

[0056] In another example, the LED-based filament lamp further comprises a light-transmissive outer shell at least partially enclosing the LED filament.

[0057] In an example, the length of the first sub-filament is substantially equal to the length of the second sub-filament.

[0058] An advantage of this particular embodiment is that the two sub-filaments are created more directly, which together appear as a single filament.

[0059] As an alternative, the first sub-filament can be longer than the second sub-filament. Even in this particular case, the technical effect is obtained over the entire range, although this is not necessary. In case of a malfunction in the second sub-filament, the user can not perceive any malfunction condition in the LED-based filament lamp. In case of a malfunction in the first sub-filament, the user can perceive a malfunction condition in a small portion of the first sub-filament.

[0060] In an example, the first driver and the second driver are any of:

[0061] a step-down converter;

[0062] a step-up converter.

[0063] The first driver and the second driver can have the same main input, for example 230 volt alternating current, AC. The converter can have an isolated output.

[0064] The driver can thus comprise a switch mode power supply. A switch mode power supply, SMPS, is an electronic circuit that uses switching devices such as transistors or MOSFETs to efficiently convert one form of electrical power to another. It is often used to regulate and convert electrical power from a power source such as the mains supply in order to provide a stable and specific output voltage or current for LEDs.

[0065] In another example, the first driver and the second driver are at least partially enclosed by a base of the LED filament lamp.

[0066] In another example, the first driver is electrically isolated from the second driver.

[0067] In an example, the first driver can be arranged to drive only the first plurality of LEDs of the first sub filament, and the second driver can be arranged to drive only the second plurality of LEDs of the first sub filament.

[0068] In an example, the second driver can differ from the first driver in terms of (maximum) output power.

[0069] In an example, the maximum output power (PI) of the second driver can differ from the maximum output power (P2) of the first driver. For example, the electronic component arrangement of the first and second driver can differ. In an example, the first driver can provide a maximum output power (PI) of 3 W, while the second driver can provide a maximum output power (P2) of 12 W.

[0070] In an example, in the first operating mode, the light emitted by the first sub filament can have a higher luminous flux and / or intensity than the light emitted by the second sub filament.

[0071] In an example, in the second operating mode, the first sub filament can emit light, while the second sub filament does not emit light.

[0072] In an example, in the third operating mode, the second sub filament can emit light, while the first sub filament does not emit light.

[0073] In a second aspect of the present disclosure, a luminaire is provided, the luminaire comprising at least one LED-based filament lamp according to any one of the above examples.

[0074] It is noted that the advantages explained with respect to the first aspect (LED-based filament lamp) also apply to the second aspect (luminaire comprising such LED-based filament lamp).

[0075] In the drawings, like reference numerals can be used to denote similar components throughout the several views. Further, various components of the same type can be distinguished by following the designation with a dash and a second designation that distinguishes among the group. If only the first designation is used, the description is applicable to any of the components bearing the same first designation, regardless of the second designation.

[0076] The above and other aspects of the present disclosure will become apparent from and elucidated with reference to the examples described hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0077] Figure 1 An example of a LED-based filament lamp according to the present disclosure is disclosed;

[0078] Figure 2 Another example of a LED-based filament lamp according to the present disclosure is disclosed;

[0079] Figure 3 A luminaire according to the present disclosure is disclosed. DETAILED DESCRIPTION

[0080] It is noted that in the description of the drawings identical reference numerals on different drawings designate identical or similar components. For the sake of clarity, the drawings can not be to scale.

[0081] Reference will now be made in detail to specific implementations, examples of which are illustrated in the accompanying drawings. It should be noted that the subject matter described herein is not limited to the specific implementations described herein. Rather, specific implementations are described herein to provide functionality in accordance with the subject matter of this disclosure. Implementations can be combined, other implementations can be utilized, and modification can be made without departing from the scope and spirit of the subject matter. Where possible, like components have been given the same reference numbers in order to illustrate the similarities in structure, function, and / or use between components. Although the drawings represent the subject matter described herein, the drawings are not necessarily drawn to scale and should not limit the scope of the claims herein. The detailed description should be read with the accompanying drawings in mind, making use of the descriptions from one drawing to facilitate understanding of another drawing, as the components of the described implementations can be positioned in a number of different orientations and the component designs / arrangements can be changed while still falling within the scope of the subject matter.

[0082] The following detailed description is merely illustrative in nature and is not intended to limit the scope of the disclosure, as claimed. Rather, the following detailed description provides an enabling description for one of ordinary skill in the art to implement the claimed subject matter. Variations and modifications to the disclosed subject matter can be made based on the description set forth herein, including combining features of the disclosed examples with other embodiments, without departing from the scope of the subject matter.

[0083] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof, means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions thereof. Where the context permits, words in the detailed description using the singular or plural number can also include the plural or singular number respectively. The word "or" in reference to a list of two or more items covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0084] These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system can vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to the specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the detailed description explicitly defines these terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

[0085] Figure 1 Example 1 of a light emitting diode, LED, based filament lamp according to the present disclosure is disclosed.

[0086] The LED based filament lamp 1 comprises a LED filament 7. The LED filament comprises a first sub filament 4 and a second sub filament 3. The sub filaments 3, 4 both comprise a plurality of LEDs. The first sub filament 4 comprises a plurality of first LEDs. The second sub filament 3 comprises a plurality of second LEDs.

[0087] The first and second sub filaments are integrated on a substrate 2. The substrate can be a printed circuit board, PCB. A PCB is typically a board made of a non-conductive material that serves as a base for mounting electronic components such as LEDs and provides interconnections between them.

[0088] Another option is to mount the LEDs on so-called Flex PCBs. This type of PCB can be made of flexible materials such as polyimide or polyester. They offer the advantage of being able to bend and conform to different shapes, making them suitable for applications where flexibility or space constraints are a concern. Flexible PCBs can be used to mount LEDs and provide electrical connections in applications where rigid PCBs can not be suitable.

[0089] Another option involves ceramic substrates. These types of substrates can be used, for example, in LED-based filament lamps with a helical filament. Ceramic substrates can provide improved thermal conductivity and insulation properties. They can effectively dissipate the heat generated by the LEDs and help maintain a stable operating temperature.

[0090] According to the present disclosure, the first and second sub-filaments can be positioned to ensure that the light emitted by each of the first LEDs (i.e. located on the first sub-filament) is mixed with the light emitted by any of the second LEDs (i.e. located on the second sub-filament). This achieves that the combination of the light emitted by the first sub-filament and the light emitted by the second sub-filament is perceived as light emitted by a single filament.

[0091] The LEDs of the different sub-filaments can be placed in close proximity to each other. The closer they are, the more effectively the light they emit will mix together, creating the illusion of a single filament. Positioning them side by side or very close together helps to minimize any perceived separation between the two light sources (i.e. the two sub-filaments).

[0092] Optics or diffusers can be incorporated to mix the light from the two sub-filaments. Optical elements such as lenses or light diffusing materials can help scatter and mix the light, reducing any apparent boundaries between the two light sources. This can result in more uniform and mixed illumination, making it appear as if it is coming from a single filament.

[0093] The inventors have found that it is also beneficial to align the direction of the light paths from the two sub-filaments. Ensuring that the light emitted by the two sub-filaments is directed towards the same focal point or general area. This alignment can help create a convergence of light and reduce the perception of multiple light sources.

[0094] Another criterion can be related to the viewing angle. The LEDs of the sub-filaments can be positioned in a way that improves the viewing angle for the desired effect. The viewing angle at which the light is observed is considered and the LED positions are adjusted accordingly.

[0095] Another criterion involves brightness matching. The brightness of the sub-filaments can be closely matched to each other. By ensuring that the two sub-filaments have similar brightness levels, it helps to further enhance the illusion of a single filament. This can be achieved by adjusting the current or voltage provided to each LED or by selecting LEDs with similar specifications.

[0096] The LED-based filament lamp further comprises a first driver 5 and a second driver 6. The first driver is arranged for driving the plurality of first LEDs of the first sub-filament 4. The second driver is arranged for driving the plurality of second LEDs of the second sub-filament.

[0097] The drivers are separate from each other. They can be connected to the same mains power, i.e. a power voltage like 230 V. The secondary sides of the drivers 5, 6 are electrically isolated from each other.

[0098] Figure 2 Another example of an LED-based filament lamp according to the present disclosure is disclosed.

[0099] The filament is indicated with reference 26. The sub-filaments are indicated with reference 22 and 23. Figure 2 The illustrated embodiment differs from Figure 1 The illustrated embodiment differs from the previously described embodiment in that the sub-filaments 22, 23 are each positioned on a separate substrate 24, 25.

[0100] Figure 3 A luminaire 31 according to the present disclosure is disclosed. Two sub-filaments are indicated with reference 32 and 33, and two drivers are indicated with reference 34 and 35.

[0101] According to the present disclosure, the LEDs of different sub-filaments can be positioned close to each other, typically within a few millimeters, to ensure that the emitted light overlaps and creates the desired mixing effect. The exact distance and angle of the LEDs can vary depending on the specific design and application, and can be determined through experimentation and testing.

[0102] If the second sub-filament fails, the user will not be able to "see" the second sub-filament. The functionality of the lamp is reduced, e.g. less light output, or reduced color combination, or any similar functionality, but the user will not "see" that a particular sub-filament is not operating correctly.

[0103] It is further noted that the LED-based filament lamp according to the present disclosure can comprise a third sub-filament. The third sub-filament can be accompanied by a third driver. All sub-filaments can be positioned such that it appears as if there is one filament in the LED-based filament lamp.

[0104] Another advantage of the present disclosure relates to the drivers of the individual sub-filaments. The sub-filaments can be of different nature, such that they have different electrical characteristics. As a result, the load encountered by the first driver can be different from the load encountered by the second driver. According to the scheme provided by the present disclosure, the drivers can be adapted to the specific load.

[0105] It should also be noted that for energy efficiency purposes it can be decided to switch off certain loads. This reduces the energy consumption while keeping the lamp operational. As mentioned above, a fault condition can occur in any of the drivers or subfilaments, but as a consequence it can also be a conscious decision to switch off one of the subfilaments. This is possible because the user will not perceive the lamp as being damaged, but will assume the lamp to be operational.

[0106] To reduce the number of claims, certain aspects of the technology are presented in terms of some embodiments in the form of certain claims. However, the applicant contemplates that each aspect of the technology can be embodied in any number of claims, including claims not expressly set forth. For example, although some aspects of the technology can be presented in the form of computer-readable medium claims, other aspects of the technology can be embodied in computer-readable medium claims, or in other forms, such as device-plus-function claims.

[0107] In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of implementations of the technology disclosed. It will be apparent, however, to one skilled in the art that embodiments of the technology disclosed can be practiced without some of these specific details.

[0108] Other variations of the disclosed embodiments can be understood and effected, by those skilled in the art in practicing the claimed application, 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 measures are recited in mutually different dependent claims does not indicate that a combination of these measures can not be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A filament lamp (1, 21, 31) based on a light-emitting diode (LED), comprising: - LED filaments (7, 26), including: (i) A first sub-filament having multiple first LEDs (3, 4, 22, 23, 32, 33), and (ii) A second sub-filament (3, 4, 22, 23, 32, 33) having multiple second LEDs. The first sub-filament (3, 4, 22, 23, 32, 33) and the second sub-filament (3, 4, 22, 23, 32, 33) are positioned to ensure that light emitted by each of the plurality of first LEDs is mixed with light emitted by any one of the plurality of second LEDs, such that the combination of light emitted by the first sub-filament (3, 4, 22, 23, 32, 33) and light emitted by the second sub-filament (3, 4, 22, 23, 32, 33) is perceived as light emitted by a single filament at the target distance; - A first driver (5, 34) is arranged to drive the plurality of first LEDs of the first sub-filaments (3, 4, 22, 23, 32, 33), wherein the first driver (5, 34) is either a buck converter or a boost converter; - A second driver (6, 35), different from the first driver (5, 34), is arranged to drive the plurality of second LEDs of the second sub-filaments (3, 4, 22, 23, 32, 33), wherein the second driver (6, 35) is either a buck converter or a boost converter.

2. The LED-based filament lamp (1, 21, 31) according to claim 1, wherein the first sub-filament and the second sub-filament (3, 4, 22, 23, 32, 33) are arranged parallel to each other and adjacent to each other.

3. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the first sub-filament (3, 4, 22, 23, 32, 33) and the second sub-filament (3, 4, 22, 23, 32, 33) are positioned such that the maximum distance between the second sub-filament (3, 4, 22, 23, 32, 33) and the first sub-filament (3, 4, 22, 23, 32, 33) is equal to or less than 5 mm, preferably equal to or less than 3 mm.

4. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the distance from each of the plurality of first LEDs to the LED of the plurality of second LEDs is less than 5 mm, preferably less than 3 mm.

5. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the LED-based filament lamp (1, 21, 31) comprises an elongated carrier, the elongated carrier comprising a first sub-filament (3, 4, 22, 23, 32, 33) and a second sub-filament (3, 4, 22, 23, 32, 33).

6. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the first sub-filament (3, 4, 22, 23, 32, 33) and the second sub-filament (3, 4, 22, 23, 32, 33) are electrically connected in series.

7. The LED-based filament lamp (1, 21, 31) according to any one of claims 1 to 5, wherein the first sub-filament (3, 4, 22, 23, 32, 33) and the second sub-filament (3, 4, 22, 23, 32, 33) are electrically connected in parallel.

8. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the filament further comprises: - A first elongated package covering the plurality of first LEDs, the first elongated package including a first light-emitting material and / or a first scattering material, the first light-emitting material being configured to at least partially convert LED light emitted by the plurality of first LEDs into first converted light, and the first scattering material being configured to at least partially scatter LED light emitted by the plurality of first LEDs into first scattered light; as well as - A second luminescent material and / or a second scattering material, wherein the second luminescent material is configured to at least partially convert LED light emitted by the plurality of second LEDs into second converted light, and the second scattering material is configured to at least partially scatter LED light emitted by the plurality of second LEDs into second scattered light; The first elongated package and the second elongated package are in physical contact.

9. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the light from the first sub-filament (3, 4, 22, 23, 32, 33) has a first correlated color temperature, and the light from the second sub-filament (3, 4, 22, 23, 32, 33) has a second correlated color temperature, wherein... ≤300K.

10. The LED-based filament lamp (1, 21, 31) according to any one of claims 1 to 8, wherein the light from the second sub-filament (3, 4, 22, 23, 32, 33) has a first correlated color temperature, and the light from the second sub-filament (3, 4, 22, 23, 32, 33) has a second correlated color temperature, wherein 500K.

11. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the length of the first sub-filament (3, 4, 22, 23, 32, 33) is substantially equal to the length of the second sub-filament (3, 4, 22, 23, 32, 33).

12. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the maximum output power of the second driver (6, 35) is different from the maximum output power of the first driver (5, 34).

13. The LED-based filament lamp (1, 21, 31) according to any one of the preceding claims, wherein the first driver (5, 34) is electrically isolated from the second driver (6, 35).

14. A luminaire comprising at least one LED-based filament lamp (1, 21, 31) according to any one of the preceding claims.

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