Color-controllable LED filament with smooth transitions

Abstract

An LED filament (100) includes an elongated substrate (110), a first region (120), a second region (130), and a third region (140) arranged between the first region and the second region. The first region includes a plurality of LEDs (121) of a first LED type, the plurality of LEDs (121) being configured to emit light having a first CCT and being arranged along at least one row on the substrate. The second region includes a plurality of LEDs (131) of a second LED type, the plurality of LEDs being configured to emit light having a second CCT different from the first CCT and being arranged along at least one row on the substrate. The third region (140) includes at least one first LED (141) of the first LED type and at least one second LED (142) of the second LED type. A first LED of the at least one first LED of the third region is located adjacent to a second LED of the second region. A second LED of the at least one second LED of the third region is located adjacent to the first LED of the first region.

Description

Technical Field

[0001] The present invention generally relates to the field of solid-state lighting. In particular, the present invention relates to a light emitting diode (LED) filament comprising an LED providing light having two different colors and a lighting device comprising such an LED filament. Background Art

[0002] Incandescent lamps are rapidly being replaced by lighting solutions based on light emitting diodes (LEDs). Solid-state lighting devices can offer many advantages over their incandescent, fluorescent, and gas discharge based counterparts. For example, they can extend operating life, reduce power consumption, and improve efficacy. Solid-state lighting devices such as LEDs are used in a wide range of lighting applications including general lighting.

[0003] LED based lighting has been developed as retrofit lamps to provide an appearance and light similar to that of an incandescent light bulb. However, in order to provide improved more decorative LED based lighting devices, further developments are needed.

[0004] WO18157428A1 discloses an LED filament with adjustable color temperature. The LED filament includes a first LED light-emitting array and a second LED light-emitting array, and the color temperature of the filament can be adjusted by coating the two arrays with different fluorescent colloids mixed with different fluorescent powders and by adjusting the color temperature of the first LED light-emitting array and the second LED light-emitting array. Summary of the invention

[0005] A general object of the present invention is to provide a color controllable LED filament lamp. In particular, it is desirable to be able to control the color temperature of a white light LED filament lamp. Adjusting the color temperature of the light can change the atmosphere of a room. Further, since many people spend a large portion of their day indoors at home and at work, the effects of different lighting on circadian rhythms and sleep patterns may become more significant. Being able to adjust the color temperature of lighting during the course of the day is beneficial for both improving work efficiency and maintaining healthier sleep patterns.

[0006] It is therefore an object of the present invention to provide an improved LED filament allowing color control. This and other objects are achieved by means of a LED filament as defined in the appended independent claim. Further embodiments are defined by the dependent claims.

[0007] The LED filament provides 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 meandering configuration, a 2D / 3D spiral or a helix. Preferably, the LEDs are arranged on an elongated carrier, such as, for example, a substrate, which may be rigid (e.g., made of polymer, glass, quartz, metal or sapphire) or flexible (e.g., made of polymer or metal, such as a film or foil).

[0008] In case the carrier comprises a first main surface and an opposing second main surface, the LEDs are arranged on at least one of these surfaces.The carrier may be reflective or light transmissive, such as translucent, preferably transparent.

[0009] The LED filament may include an encapsulant that at least partially covers at least a portion of the plurality of LEDs. The encapsulant may also at least partially cover at least one of the first major surface or the second major surface. The encapsulant may be a polymer material that may be flexible, such as, for example, silicone. Further, the LED may be arranged to emit, for example, LED light of different colors or spectra. The encapsulant may include a light-storage material that is configured to convert at least partially the LED light into converted light. The light-storage material may be a phosphor, such as an inorganic phosphor and / or quantum dots or rods.

[0010] An LED filament may include multiple sub-filaments.

[0011] In the present invention, a light emitting diode (LED) filament is provided. The LED filament includes an elongated substrate, a first region, a second region, and a third region. The first region includes only a plurality of first LEDs of a first LED type, and the plurality of first LEDs are configured to emit light having a first correlated color temperature (CCT). The first LEDs of the first region are arranged on the substrate along at least one row. The second region includes only a plurality of second LEDs of a second type, and the plurality of second LEDs are configured to emit light having a second CCT. The second CCT is different from the first CCT. The third region is arranged between the first region and the second region. The third region includes at least one first LED of the first type and at least one second LED of the second type. A first LED of the at least one LED of the first type in the third region is arranged adjacent to a second LED of the second region. A second LED of the at least one second LED of the third region is arranged adjacent to the first LED of the first region.

[0012] A plurality of first LEDs of the first region, a plurality of second LEDs of the second region, and at least one first LED and at least one second LED of the third region may be arranged on a first side of the substrate. The substrate may be at least partially light-transmissive, such as translucent or transparent. In an embodiment where the substrate is at least partially light-transmissive, the LEDs of the first region, the LEDs of the second region, and the LEDs of the third region may be arranged on more than one surface (side) of the substrate.

[0013] The first LEDs of the first area and the third area can be electrically connected. The second LEDs of the second area and the third area can be electrically connected. Specifically, these connections can be configured to allow separate power supply to the plurality of first LEDs and the plurality of second LEDs.

[0014] In other words, the LED filament may include a first linear array including LEDs of a first LED type that may be interconnected, and a second linear array including second LEDs of a second LED type that may be interconnected. Because the LEDs in the first array are all LEDs of the first type having a first CCT, and the LEDs in the second region are LEDs of the second type having a second CCT, the LEDs of the first array and the second array may be arranged such that there is a partial overlap between the first linear array and the second linear array corresponding to the third region, so that a transition from one color temperature (CCT) to another color temperature may occur in a gradual manner. The overlap (i.e., the third region) may include more than one LED of each type (first and second). For example, the overlap (third region) may include two, three, or four LEDs of each type.

[0015] By way of example, it will be appreciated that the number of LEDs in a linear array may be at least 10, more specifically at least 15, even more specifically at least 17.

[0016] Throughout the present invention, a first LED refers to a first type of LED configured to emit light having a first CCT. A second LED refers to a second type of LED configured to emit light having a second CCT.

[0017] In some embodiments, both types of LEDs can emit light having a color rendering index of at least 80, more specifically, at least 85, and even more specifically, at least 90.

[0018] The whiteness of a light source is usually described relative to an ideal black body radiator. As the temperature of an ideal black body increases, the black body begins to glow red, i.e., emits red light. As the black body heats up, the light becomes yellow, and finally, for very high temperatures, the emitted light becomes white. The correlated color temperature (CCT) of a light source is the temperature (expressed in Kelvin) of an ideal black body radiator that displays the most similar color. The black body line or black body locus (BBL) is the path that such a black body may take in a particular chromaticity space as its temperature increases.

[0019] In a sense, the everyday concept of color temperature is the opposite of the CCT scale. Typically, redder light is described as warmer light, while white-blue light is described as cooler light. In the CCT scale, red (warmer) light corresponds to lower (cooler) temperatures, while white-blue (cooler) light corresponds to higher (warmer) temperatures.

[0020] According to some embodiments, a first length of the first region and a second length of the second region may be related such that a ratio of the first length to the second length is in a range of 0.9 to 1.1.

[0021] A ratio between the lengths of the first region and the second region in the range of 0.9 to 1.1 may give the LED filament a symmetrical appearance, which may be aesthetically pleasing while providing a more uniform light distribution.

[0022] According to some embodiments, a first length of the first region and a second length of the second region may be related such that a ratio of the first length to the second length is greater than 1.2.

[0023] According to some embodiments, a first length of the first region and a second length of the second region may be related such that a ratio of the second length to the first length is greater than 1.2.

[0024] For some applications, for example, for activities that require higher object visibility, it may be desirable to have a higher color temperature. In these applications, it may be advantageous to have more LEDs with a higher CCT. Having a longer area with higher CCT LEDs may allow more higher CCT LEDs to be arranged on the filament. Thus, more light with a higher CCT may be emitted by the LED filament.

[0025] Alternatively, it may be desirable for the LED filament to provide cooler (yellower / redder) light, for example, in decorative lighting. In such applications, the area with lower CCT LEDs may be longer in order to include more lower CCT LEDs.

[0026] According to some embodiments, the third length of the third region may be less than half of the first length of the first region, and / or the third length may be less than half of the second length of the second region.

[0027] According to some embodiments, the first CCT may be higher than the second CCT.

[0028] According to some embodiments, the first CCT may be above 2500K.

[0029] Light with a CCT above 2500K can provide better visibility of objects. Including light above 2500K can allow the lighting device to be used for general lighting where activities requiring high visibility are performed, such as work places. Such activities can include reading and cleaning, for example.

[0030] For example, the first CCT may be higher than 2700K. Specifically, the first CCT may be higher than 3000K, such as 3300K.

[0031] According to some embodiments, the second CCT may be lower than 2400K.

[0032] Light with a CCT below 2400K is classified as warm white. This light can provide a comfortable atmosphere.

[0033] For example, the second CCT may be lower than 2200 K. Specifically, the second CCT may be lower than 2100 K, such as 2000 K.

[0034] An LED filament having a first type of LED providing light with a higher CCT and a second type of LED providing light with a lower CCT can allow for color control of light emitted by the LED filament based on powering different types of LEDs on the LED filament. Specifically, the light emitted by the LED filament can be a combination of light emitted by the first type of LED and the second type of LED. Thus, the combined light can vary within a range from the CCT of the second type of LED to the CCT of the first type of LED.

[0035] According to some embodiments, the first LEDs of the first region, the second LEDs of the second region, and the first LEDs and second LEDs of the third region may all be aligned along a single row on the substrate.

[0036] Arranging the three regions of LEDs in a row may provide a thinner LED filament, which in turn may reduce material costs and / or production costs.

[0037] According to some embodiments, the third region may include more than one first LED and more than one second LED.The LEDs of the third region may be arranged along a single row, wherein every other LED is a first LED.

[0038] The alternating first and second type LEDs in the third region can provide a transition from one CCT LED to another CCT LED. Such a transition can provide more uniform illumination and be more aesthetically pleasing.

[0039] According to some embodiments, the third region may include more than one first LED and more than one second LED. The LEDs of the third region may be arranged to form a gradient transition between the first LEDs of the first region and the second LEDs of the second region.

[0040] In other words, the first LEDs and the second LEDs in the third region are not uniformly distributed along the third region. In order to form a gradient (or gradual) transition between the first LEDs in the first region and the second LEDs in the second region, the density of the first LEDs in the third region is higher in the segment immediately adjacent to the first region and gradually becomes lower toward the segment immediately adjacent to the second region, and vice versa for the second LEDs in the third region. For example, the number of consecutive first LEDs between each second LED (group) in the third region may be larger in the segment immediately adjacent to the first region and gradually becomes smaller toward the segment of the third region immediately adjacent to the second region. Similarly, the number of consecutive second LEDs between each first LED (group) in the third region may be larger in the segment immediately adjacent to the second region and gradually becomes smaller toward the segment of the third region immediately adjacent to the first region.

[0041] This arrangement of LEDs in the third overlapping region can provide a gradual transition from LEDs of one color (CCT) to LEDs of another color (CCT). The gradual transition can provide a gradient of color (CCT) of light from a first region (emitting light having a first CCT) to a second region (emitting light having a second CCT). This transition can provide a more uniform and aesthetically pleasing illumination for the LED filament.

[0042] According to some embodiments, the first LEDs of the first region, the second LEDs of the second region, and the first and second LEDs of the third region can be arranged along two separate rows on the substrate. The first row can include some of the first LEDs from the first region, the first LEDs from the third region, and some of the second LEDs from the second region. The second row can include some of the first LEDs from the first region, the second LEDs from the third region, and some of the second LEDs from the second region.

[0043] In other words, the first LEDs of the first region may be arranged in two separate rows and the second LEDs of the second region may be arranged in two separate rows. At least one first LED of the third region may be arranged in a row aligned with one of the first LED rows of the first region and one of the second LED rows of the second region, and the at least one second LED of the third region may be arranged in a row aligned with the other first LED rows of the first region and the other second LED rows of the second region. The rows may be parallel.

[0044] Arranging the LEDs of the first region, the second region, and the third region into two rows can increase the density of the LEDs on the substrate (i.e., placing more LEDs on a shorter substrate). Thus, a more compact LED filament can emit more light. Arranging the LEDs of the third region into a row including the first LED and a row including the second LED can provide a transition of the light emitted by the LED filament from a first CCT to a second CCT.

[0045] According to some embodiments, the distance between two consecutive LEDs in a first portion of the first area adjacent to the third area may be shorter than the distance between two consecutive LEDs in a portion of the first area opposite to the first portion. Further, the distance between two consecutive LEDs in a second portion of the second area adjacent to the third area is shorter than the distance between two consecutive LEDs in a portion of the second area opposite to the second portion.

[0046] In other words, the distance (or pitch) between consecutive LEDs may be greater in regions near the end points of the substrate (e.g., in the ends of a combined row of LEDs including the first, second, and third regions) than in regions of the substrate (or row) between those ends. Increasing the distance between the two outermost LEDs or the three or four outermost LEDs in a row of LEDs on an LED filament may provide a more gradual falloff in hue of light at the edges of the LED filament.

[0047] Further, since the first LEDs in the third region can be placed in a staggered manner with the second LEDs or arranged together with the second LEDs in another manner, the spacing between two first LEDs (of the first type) in the third region can be greater than the spacing between two first LEDs in the first region. To create symmetry, the spacing between the LEDs in the portion of the first region farthest from the third region can be adapted to reflect the spacing of the first LEDs in the third region, and the same is true for the second LEDs. A more symmetrical spacing and arrangement of the LEDs can provide more uniform light, and a more pleasing appearance of the LED filament and the emitted light can be obtained.

[0048] According to some embodiments of the present invention, a lighting device is provided. The lighting device may include at least one LED filament, as described above with reference to any of the aforementioned embodiments. The lighting device may also include an at least partially light-transmissive capsule, the capsule at least partially encapsulating the at least one LED filament. The lighting device may include a base on which the capsule is mounted. The lighting device may include a controller configured to control the power supply to the first LED of the first area and the at least one first LED of the third area. The controller may also be configured to control the power supply to the second LED of the second area and the at least one second LED of the third area.

[0049] For example, the controller can control the power (or current) supply to the first LEDs of the first and third regions separately or independently of the power (or current) supply to the second LEDs of the second and third regions. Specifically, all the first LEDs of the first and third regions can share a power supply, and all the second LEDs of the second and third regions can share a separate power supply.

[0050] Since the plurality of first LEDs and the plurality of second LEDs can be controlled separately, the controller can control the light emission from different types of LEDs. By changing the emission ratio of two LED sets (or multiple LEDs) with different color temperatures, the correlated color temperature (CCT) of the combined light (i.e., the light emitted by the lighting device) can be adjusted. Specifically, the CCT control range can extend from the CCT of the LED type with the lowest color temperature to the CCT of the LED type with the highest color temperature.

[0051] Specifically, varying the emission ratio between the plurality of first LEDs and the plurality of second LEDs can allow the color temperature of the combined light (i.e., the light emitted by the lighting device) to be moved within a range between the CCT of the first LED type and the CCT of the second LED type along a line close to the black body line (BBL). This means that the behavior of the LED filament can be similar to an ideal black body radiator within a range.

[0052] In an embodiment including one LED type in a higher color temperature range and one LED type in a lower color temperature range, the same lighting device can be used for different activities. This can provide the user with the option of adapting the lighting to the current activity and mood based on the power supplied to the first LED compared to the power supplied to the second LED.

[0053] Further, control of the power (or current) supply to the first LED of the first LED type and the second LED of the second LED type may also control the flux of light emitted by the lighting device.The controller may be adapted to control both the CCT of the combined light and the intensity or flux of the combined light.

[0054] For example, at least one LED filament may be arranged to extend away from the base, or to extend substantially parallel to a plane defined by the base.

[0055] According to some embodiments, the lighting device may include at least one first LED filament as described above with respect to any of the aforementioned embodiments and at least one second LED filament as described above with respect to any of the aforementioned embodiments. The at least one first LED filament and the at least one second LED filament may be arranged substantially parallel to each other in different directions.

[0056] Since the first region of one LED filament can be arranged closer to the second region of another LED filament, arranging the LED filaments in different directions can increase the uniformity of the light emitted by the lighting device. In particular, in embodiments where more than one LED filament is arranged side by side with each other, every other LED filament can be arranged inverted relative to the other LED filaments, i.e., if the LED filaments are equal and symmetrical, the first region of the LED filament is arranged side by side with the second region of the neighboring LED filament.

[0057] Alternatively, all of the LED filaments may be arranged in a similar orientation, such as substantially parallel to their first regions arranged along one another and their second regions arranged along one another.

[0058] It should be noted that other embodiments using all possible combinations of the features described in the embodiments described above can be envisioned. Therefore, the present invention also relates to all possible combinations of the features mentioned herein. Any embodiment described herein can be combined with other embodiments also described herein, and the present invention relates to all combinations of features. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Now, exemplary embodiments are described in more detail with reference to the following drawings:

[0060] Figure 1 is a schematic illustration of an LED filament according to some embodiments;

[0061] Figure 2 is a schematic side view of an LED filament according to some embodiments;

[0062] Figure 3 is a schematic illustration of an LED filament according to some embodiments;

[0063] Figure 4 shows a schematic illustration of an LED filament in which the lengths of different regions are shown;

[0064] Figure 5 is a schematic illustration of an LED filament according to some embodiments;

[0065] Figure 6 shows a schematic illustration of an LED filament in which LEDs in a third region form a gradient transition according to some embodiments;

[0066] Figure 7 is a schematic illustration of an LED filament including two LED rows D according to some embodiments;

[0067] Figure 8 is a schematic illustration of an LED filament in which the distance between consecutive LEDs is different in certain portions of the area according to some embodiments;

[0068] Fig. 9 is a schematic illustration of a lighting device according to some embodiments;

[0069] Fig.10 is a schematic illustration of a lighting device including more than one LED filament according to some embodiments.

[0070] As shown in the figures, the size of elements and regions may be exaggerated for illustrative purposes and are therefore provided to illustrate the general structure of the embodiments. Therefore, embodiments may include more or fewer LEDs. The same reference numerals represent the same elements throughout. DETAILED DESCRIPTION

[0071] Now, the exemplary embodiments are described more fully below with reference to the accompanying drawings, in which the currently preferred embodiments are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided to be thorough and complete and to fully convey the scope of the invention to the skilled person.

[0072] refer to Figure 1 , a light emitting diode (LED) filament according to some embodiments will be described.

[0073] Figure 1The LED filament 100 includes a substrate 110, a first region 120, a second region 130, and a third region 140. The third region 140 is located between the first region 120 and the second region 130 on the substrate 110. The first region 120 includes a plurality of first LEDs 121 arranged in a row on a first side of the substrate 110. The second region 130 includes a plurality of second LEDs 131 arranged in a row on a first side of the substrate 110. The third region 140 includes a first LED 141 and a second LED 142. The third region 140 may correspond to an overlap of two LED arrays, the first LED array including the first LED 121 of the first region 120 and the first LED 141 of the third region 140, and the second LED array including the second LED 131 of the second region 130 and the second LED 142 of the third region 140. The first LED 121 of the first area 120, the first LED 141 of the third area 140, the second LED 142 of the third area 140, and the second LED of the second area 130 are arranged in a row on the substrate 110. The first LED 141 of the third area 140 is arranged adjacent to the second LED of the second area 130. The second LED 142 of the third area 140 is arranged between the first LED 141 of the third area 140 and the first LED of the first area 120.

[0074] The first LED 121 and the first LED 141 are both first type LEDs. The first type LED is configured to emit light having a first correlated color temperature (CCT). The second LED 131 and the second LED 142 are both second type LEDs. The second type LED is configured to emit light having a second CCT different from the first CCT. In some embodiments, the first CCT is higher than the second CCT. For example, the first CCT may be higher than 2500K. Specifically, the first CCT may be higher than 2700K. More specifically, the first CCT may be higher than 3000K, such as 3300K. The second CCT may be, for example, lower than 2400K. Specifically, the second CCT may be lower than 2200K. More specifically, the second CCT may be lower than 2100K, such as 2000K.

[0075] The light emitted by the LEDs of the first type and the light emitted by the LEDs of the second type arranged on the LED filament 100 together form the light emitted by the LED filament 100 .

[0076] In some embodiments, the LED can be a blue LED and / or a UV LED, which is covered by a light-storage material, for example, a sealant including the light-storage material. The luminescent material can be a phosphor, such as, for example, an inorganic phosphor or quantum dots / rods. The blue light and / or UV light can then be converted into converted light by the light-storage material. Green / yellow phosphors and / or red phosphors can be used to obtain green / yellow light and red light, respectively.

[0077] Further, it should be appreciated that the first LED and the second LED can be phosphor-converted LEDs (pc LEDs). The type, concentration, and layer thickness of the phosphor of the first LED can be different from the type, concentration, and layer thickness of the phosphor of the second LED. LEDs that emit lower color temperatures typically have higher phosphor thicknesses, higher concentrations, and / or phosphors that emit higher wavelengths of light.

[0078] The first LED 141 of the third area 140 is electrically connected to the plurality of first LEDs 121 of the first area 120 via an electrical connection 122. The second LED 142 of the third area 140 is electrically connected to the second LED 131 of the second area 130 via an electrical connection 132. The electrical connection 122 can be configured to supply power to the first LEDs 121, 141. The electrical connection 132 can be configured to supply power to the second LEDs 131, 142. In the present embodiment, the first electrical connection 122 and the second electrical connection 132 are series connections for supplying power to the respective LEDs. In other embodiments, the LEDs can be connected in other ways. For example, the first LED can be connected in parallel and / or the second LED can be connected in parallel. In other embodiments, the LEDs can be connected in smaller groups.

[0079] The substrate 110 may be partially light-transmissive. The substrate may be, for example, translucent or transparent. The substrate 110 may be at least partially curved. The substrate 110 may be at least partially flat. The substrate 110 may be rigid. The substrate 110 may be flexible.

[0080] refer to Figure 2 , an LED filament according to some embodiments will be described.

[0081] Figure 2 is a schematic side view of an LED filament 200. The LED filament 200 may be equivalent to the reference Figure 1 The LED filament 100 is described. The LED filament includes an encapsulant 250 that encapsulates a substrate 110 and an LED disposed on a first side 211 of the substrate 110 .

[0082] In other embodiments, the sealant may cover at least a portion of the LEDs disposed on the first side. The sealant may also cover at least a portion of the substrate. Some embodiments may have LEDs disposed on more than one surface (or side), such as LEDs disposed on two opposite surfaces of the substrate. In some embodiments, the sealant may cover the sides of the substrate on which the LEDs are disposed and the LEDs on these sides. In some embodiments, the sealant may encapsulate all sides of the substrate.

[0083] The sealant 250 may include a polymer. The sealant 250 may include a silicone-based material. The sealant 250 may include a diffusive material for propagating light. For example, the sealant 250 may include scattering particles, such as one or more of the following: barium sulfate (BaSO4) particles, aluminum oxide (Al2O3) particles, and titanium dioxide (TiO2) particles. The sealant is at least partially light-transmissive, such as translucent or transparent.

[0084] Reference Figure 3 will describe an LED filament according to some embodiments. The LED filament 300 may be equivalent to the LED filament 100 described in reference Figure 1 except that the third region 340 of the LED filament 300 includes three first LEDs 341 and three second LEDs 342. The three first LEDs 341 are arranged in a manner staggered with the three second LEDs 342 such that every other LED (or overlapping) in the third region 340 is a first LED 341.

[0085] Other embodiments may include more or fewer LEDs in the third region, and these LEDs may be arranged alternately as Figure 3 shown.

[0086] Reference Figure 4 will describe the lengths of different regions. Figure 4 is a schematic illustration of an LED filament 400 that may be equivalent to the LED filament 100 described in reference Figure 1 In Figure 4 , the first region has a first length L1, the second region has a second length L2, and the third region has a third length L3.

[0087] In some embodiments, the ratio of the first length L1 to the second length L2 is in the range of 0.9 to 1.1, i.e., 0.9L2 < L1 < 1.1L2, such that the lengths of the first region and the second region are substantially the same. Such embodiments may have a symmetric appearance.

[0088] In other embodiments, the ratio of the first length L1 to the second length L2 is greater than 1.2, i.e., L1>1.2L2. In such embodiments, the first region having the first LED is longer than the second region including the second LED. Thus, the first region can include more LEDs than the second region, thereby providing more intensity at the first CCT.

[0089] In other embodiments, the ratio of the second length L2 to the first length L1 is greater than 1.2, i.e., L2>1.2L1. In such embodiments, the region with the first LED is shorter than the second region including the second LED. Therefore, the second region can include more LEDs than the first region, thereby providing more intensity at the second CCT.

[0090] In some embodiments, the third length L3 may be less than half of the first length L1, ie, L3<0.5L1. In some embodiments, the third length L3 may be less than half of the second length L2, ie, L3<0.5L2.

[0091] refer to Figure 5 , an LED filament according to some embodiments will be described.

[0092] Figure 5 5 is a schematic diagram of an LED filament 500. The LED filament 500 may be identical to the reference filament 500 except that the third region 540 includes two first LEDs 541 and two second LEDs 542. Figure 1 The described LED filament 100. Two first LEDs 541 are arranged adjacent to each other between one second LED 542 of the second LEDs 542 and the second LED of the second region. Two second LEDs 542 are arranged adjacent to each other between one first LED 541 of the first LEDs 541 and the first LED of the first region.

[0093] In other words, in the third area, the second LEDs form a group of two LEDs following the group of two LEDs of the first type. Every two LEDs are of the first type and every two LEDs are of the second type.

[0094] In other embodiments, there may be more such alternating pairs of LEDs in the third region. Further, in other embodiments, different kinds of LEDs may be regrouped by groups of more than two LEDs, such as, for example, three, four or more LEDs.

[0095] refer to Figure 6 , an LED filament according to some embodiments will be described.

[0096] Figure 6is a schematic diagram of an LED filament 600. The LED filament 600 may be equivalent to the reference Figure 1 The LED filament 100 described, except that there are more LEDs in the third region, the LEDs are arranged in a different manner.

[0097] The third region 640 of the LED filament 600 includes four first LEDs 641 and four second LEDs 642. In this configuration, there are a first region, a third region, and a second region from left to right on the LED filament 600. The first region is composed of two first LEDs. The third region is formed by a second LED and a subsequent first LED, two consecutive second LEDs and two consecutive first LEDs, and a second LED and a subsequent first LED. The second region includes two consecutive second LEDs. When the density of the first LEDs gradually decreases from the first region to the second region and the density of the second LEDs gradually increases from the first region to the second region, the LEDs in the third region 640 form a gradual transition between the first LEDs in the first region and the second LEDs in the second region. This gradual transition of LED density can provide a color gradient from a first CCT in the first region to a second CCT in the second region to the light emitted by the third region.

[0098] refer to Figure 7 , an LED filament according to some embodiments will be described.

[0099] Figure 7 is a schematic diagram of an LED filament 700. The LED filament 700 may be equivalent to the reference Figure 1 The LED filament 100 is described except that the LEDs of the first region 720 , the second region 730 , and the third region 740 are arranged in two parallel rows 705 , 715 .

[0100] In this illustration, the first row 705 includes, from left to right, four first LEDs in the first region 720, four first LEDs in the third region 740, and four second LEDs in the second region 730. In this configuration, the second row 715 is arranged above the first row 705 on the substrate and is separated from the first row (e.g., parallel to the first row). In this illustration, the second row 715 includes, from left to right, four first LEDs in the first region 720, four second LEDs in the third region 740, and four second LEDs in the second region 730. Therefore, in the third region 740, the first LEDs and the second LEDs are arranged in separate rows.

[0101] However, in other embodiments, the LEDs may be arranged in more than two rows, and the LEDs of the third region may be arranged in any other manner described herein or using a combination of arrangements described herein.

[0102] refer to Figure 8 , an LED filament according to some embodiments will be described.

[0103] Figure 8 Shown are a schematic image of an LED filament 800 and an exploded view of the LED filament 800. The LED filament 800 may be identical to the LED filament 100, except that the distance between adjacent LEDs is changed in some portions.

[0104] In this embodiment, the LED filament 800 includes four first LEDs in the first region 820 , one first LED and one second LED in the third region 840 , and four second LEDs in the second region 830 .

[0105] The spacing (or first pitch P2) between the two first LEDs of the first region 820 is the same as the spacing (or first pitch P4) between the two second LEDs of the second region 830, the two first LEDs are located at a position farthest from the third region 840 (in this illustration, on the leftmost), and the two second LEDs are located at a position farthest from the third region 840 (in this illustration, on the rightmost). Between all other consecutive LEDs, the spacing (second pitch P1, P3) is the same and shorter than the previously mentioned spacing (first pitch P2, P4).

[0106] Turning to the exploded view, it can be seen that the first array 825 including the first LEDs 821 of the first region and the first LEDs 841 of the second region is symmetrical about a first symmetry line A that divides the array 825 into two equal parts. The length of the shortest distance D1 between the first LEDs of the third region 840 and the first LEDs of the first region 820 is the same as the length of the first pitches P2, P4.

[0107] Likewise, the second array 835 including the second LEDs 831 of the second region and the second LEDs 842 of the third region is symmetric about a second symmetry line B that divides the array 835 into two equal parts.

[0108] In other embodiments, the spacing between the LEDs in the first and second regions may be as Figure 8 The same is suitable for reflecting the spacing between LEDs of the same type in the third area.

[0109] refer to Fig. 9 , a lighting device according to some embodiments will be described.

[0110] Fig. 9960 is a schematic illustration of a lighting device 960 according to some embodiments. The lighting device 960 includes an LED filament 900, which can be equivalent to any LED filament described with respect to any of the preceding figures. The lighting device 960 also includes an at least partially light-transmissive enclosure 961, a base 962, a controller 963, and a connector 964.

[0111] The LED filament 900 is arranged to extend away from a plane defined by the base 962. However, in other embodiments, the LED filament 900 may be arranged in a different orientation.

[0112] The encapsulant 961 encapsulates the LED filament 900. The encapsulant 961 is at least partially light-transmissive to couple out the light emitted by the LED filament 900, i.e., transmit the light to the outside of the encapsulant 961. The reflectivity of the encapsulant 961 to the wavelength of the light emitted by the LED filament 900 may be less than 20%. Specifically, the reflectivity of the outer shell 961 to the wavelength of the light emitted by the LED filament 900 may be less than 15%. More specifically, the reflectivity of the outer shell 961 to the wavelength of the light emitted by the LED filament 900 may be less than 10%. For example, the encapsulant 961 may be transparent.

[0113] The enclosure 961 is mounted on a base 962. The base 962 may include an electrical connector for connecting the lighting device 960 to a luminaire socket. The base 962 may be adapted to connect to, for example, an Edison socket or a bayonet socket. The base 962 may, for example, include a cap, such as an E27 cap. The base 962 may also include a housing. In some embodiments, the controller 963 may be disposed within the housing.

[0114] The LED filament 900 is connected to the controller 963 by means of a connector 964. The connector 964 may include a retaining device for retaining the LED filament 900. The connector 964 may also include an electrical connection for supplying power to the LED filament 900.

[0115] The controller 963 is configured to control the power supply to the first LEDs 921 , 941 of the first type of LED filament and the power supply to the second LEDs 931 , 942 of the second type of LED filament 900 .

[0116] The controller 963 may be configured to individually control power supply to the first LEDs 921, 941 and the second LEDs 931, 942 of the filament 900. By controlling the power supply to the LEDs, the brightness of each of the sets of first LEDs 921, 941 and the sets of second LEDs 931, 942 may be controlled.

[0117] The power ratio between the first type of LED 921, 941 and the second type of LED 931, 942 is particularly interesting because changes in the ratio of the emissivity between the different types of LEDs can change the color temperature of the combined light. The controller 963 can control the color temperature of the light emitted by the lighting device 960 within a range extending from the CCT of the first LED 921, 941 (without power to the second LED 931, 942) to the CCT of the second LED 931, 942 (without power to the first LED 921, 941).

[0118] The controller 963 can be configured to operate the LED filament in different modes. According to a first operating mode, which can be referred to as "starting with high CCT", the first LED and the second LED can be turned off in an initial state, and then the first LED can be turned on while the second LED is still turned off. As a next step, the second LED can be turned on while the first LED is still turned on. The advantages of this operating process or operating mode can be as follows: when the LED filament or lighting device is turned on, high quality light is directly provided (the object can be better seen due to the higher CCT).

[0119] According to another operating mode which may be referred to as "starting with low CCT", the first LED and the second LED may be turned off in the initial state, and then the second LED may be turned on while the first LED is still turned off. As a next step, the first LED may be turned on while the second LED is still turned on. The process then has the advantage of starting with filament light.

[0120] As yet another operation mode referred to as “starting with average CCT”, the first LED and the second LED are turned off in an initial state, and the first LED and the second LED are turned on. This operation mode provides a gradient appearance, which can be considered a design feature.

[0121] According to other operating modes, the LED can be turned on to reach the maximum current immediately or gradually reach a specific current level (slowly increase the current). Similarly, the LED can be turned off to suppress all current supply immediately, or turned off using a dimming function (slowly reduce the current).

[0122] Each of the first LEDs can provide a first luminous flux (LF1), and each of the second LEDs can provide a second luminous flux (LF2). When the first LED and the second LED are turned on, the LEDs can be controlled to switch from LF1>LF2 to LF2>LF1. In this way, the (correlated) color temperature can be adjusted.

[0123] refer to Fig.10 , a lighting device according to some embodiments will be described.

[0124] Fig.10 is a schematic illustration of a lighting device 1060, which may be equivalent to reference Fig. 9 The lighting device 960 is described, except that the lighting device 960 includes four LED filaments 1100, 1101, which may be equivalent to any of the LED filaments described with reference to the previous figures.

[0125] The lighting device 1060 comprises a pear-shaped enclosure 1061 mounted on a base 1062. Inside the enclosure, two first LED filaments 1100 and two second LED filaments 1101 are arranged, which may be of the same type as the two first LED filaments 1100. The LED filaments 1100, 1101 are arranged parallel to each other and extend (substantially perpendicularly) away from a plane defined by the base 1062 of the lighting device 1060. The LED filaments 1100, 1101 are connected to a controller 1063 via connections 1064.

[0126] The LED filaments 1100, 1101 are arranged so that every other LED filament is a first LED filament 1100, and every other LED filament is a second LED filament 1101. The two first LED filaments 1100 are guided so that the section of the first LED filament 1100 including the second region 1030 is farthest from the base 1062. The two second LED filaments 1101 are arranged upside down relative to the two first LEDs. In other words, the two second LED filaments 1101 are arranged in opposite directions relative to the first LED filaments 1100 so that the section of the two second LED filaments 1101 including the first region 1025 is arranged farther away from the base 1062.

[0127] In other embodiments, the LED filaments 1100, 1101 may be arranged differently within the enclosure 1061. For example, the LED filaments 1100, 1101 may be arranged in the same direction. Alternatively, the LED filaments 1100, 1101 may be arranged in different directions and orientations.

[0128] Those skilled in the art realize that the present invention is by no means limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

[0129] Although features and elements are described above in particular combinations, each feature or element may be used alone without the other features and elements or in various combinations with or without the other features and elements.

[0130] Additionally, variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention by studying 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.

Claims

1. A light emitting diode (LED) filament (100), comprising: an elongated substrate (110); a first region (120) comprising only a plurality of first LEDs (121) of a first LED type, the plurality of first LEDs being configured to emit light having a first correlated color temperature and being arranged along at least one row on the substrate; a second region (130) comprising only a plurality of second LEDs (131) of a second LED type, the plurality of second LEDs being configured to emit light having a second correlated color temperature and being arranged along at least one row on the substrate, the second correlated color temperature being different from the first correlated color temperature; as well as A third region (140) is arranged between the first region and the second region on the substrate, the third region comprising at least one first LED (141) of the first LED type and at least one second LED (142) of the second LED type, wherein a first LED of the at least one first LED of the third region is located adjacent to the second LED of the second region, and wherein a second LED of the at least one second LED of the third region is located adjacent to the first LED of the first region, so that a transition between the first correlated color temperature in the first region and the second correlated color temperature in the second region is achieved in a gradual manner.

2. The LED filament (400) according to claim 1, wherein a first length (L1) of the first region and a second length (L2) of the second region are related such that a ratio of the first length to the second length is in the range of 0.9 to 1.

1. 3 . The LED filament of claim 1 , wherein a first length of the first region and a second length of the second region are related such that a ratio of the first length to the second length is greater than 1.

2. 4 . The LED filament of claim 1 , wherein a first length of the first region and a second length of the second region are related such that a ratio of the second length to the first length is greater than 1.

2.

5. The LED filament according to any one of claims 1 to 4, wherein a third length (L3) of the third region is less than half of a first length of the first region and / or the third length is less than half of a second length of the second region. 6 . The LED filament according to claim 1 , wherein the first correlated color temperature is higher than the second correlated color temperature.

7. The LED filament according to any one of claims 1 to 4, wherein the first correlated color temperature is higher than 2500K.

8. The LED filament according to any one of claims 1 to 4, wherein the second correlated color temperature is lower than 2400K.

9. The LED filament according to any one of claims 1 to 4, wherein the first LEDs of the first region, the second LEDs of the second region, and the first LEDs and the second LEDs of the third region are aligned along a single row on the substrate.

10. The LED filament (300) according to any one of claims 1 to 4, wherein the third region comprises more than one first LED (341) and more than one second LED (342) arranged along a single row, wherein every other LED is a first LED.

11. The LED filament (600) according to any one of claims 1 to 4, wherein the third region comprises more than one first LED (641) and more than one second LED (642), and the more than one first LED and the more than one second LED are arranged to form a gradient transition between the first LED of the first region and the second LED of the second region.

12. The LED filament (700) according to any one of claims 1 to 4, wherein the first LED of the first region, the second LED of the second region, and the first LED and the second LED of the third region are arranged on the substrate along two independent rows; wherein a first row (705) includes some first LEDs of the first LEDs of the first region, the first LEDs of the third region, and some second LEDs of the second LEDs of the second region; and The second row (715) includes some first LEDs of the first region, the second LEDs of the third region, and some second LEDs of the second LEDs of the second region.

13. The LED filament (800) according to any one of claims 1 to 4, wherein a distance (P1) between two consecutive LEDs in a first portion of the first region located adjacent to the third region is shorter than a distance (P2) between two consecutive LEDs in a portion of the first region opposite to the first portion, and / or wherein a distance (P3) between two consecutive LEDs in a second portion of the second region located adjacent to the third region is shorter than a distance (P4) between two consecutive LEDs in a portion of the second region opposite to the second portion.

14. A lighting device (960), comprising: At least one LED filament (900) according to any one of the preceding claims; An at least partially light-transmissive capsule (961) at least partially encapsulating the at least one LED filament; a base (962) on which the capsule is mounted; as well as A controller (963) is configured to control power supply to the first LED of the first region and the at least one first LED of the third region of the at least one LED filament, and to control power supply to the second LED of the second region and the at least one second LED of the third region of the at least one LED filament.

15. The lighting device according to claim 14, further comprising at least one first LED filament (1100) according to any one of claims 1 to 13 and at least one second LED filament (1101) according to any one of claims 1 to 13, wherein the at least one first LED filament and the at least one second LED filament are arranged substantially parallel to each other and in different directions.

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