LED module with double diffuser

Abstract

LED module that features: - at least one LED chip mounted on a carrier that produces white, greenish-white, green, greenish-yellow or yellow light via phosphor conversion, - a first diffuser element that diffusely scatters light from the at least one LED chip and is spaced at least 1 mm, preferably at least 2 mm, away from the at least one LED chip, forming an air gap, and - a second diffuser element, which, viewed in the direction of light emission, is located outside the first diffuser element and separated from it, preferably by forming an air gap, - wherein the first diffuser element is hood-shaped, and - wherein the wall thickness of the first diffuser element in an area above the at least one LED chip is less than in the edge area of ​​the hood-like diffuser element, which diffusely scatters laterally emitted light from the at least one LED chip.

Description

[0001] The invention relates to an LED module that can be used, for example, in retrofit LED lamps designed as replacements for halogen lamps or incandescent lamps.

[0002] LED lamps are increasingly used for lighting. They are characterized by their high luminous efficiency and long lifespan. Furthermore, their extremely small size allows for very flexible application. LEDs are mostly manufactured as LED modules. These modules typically consist of at least one blue LED, which generates white light through a wavelength converter integrated into the LED. RGB LED modules allow for the creation of any color, with adjustment and dimming possible via PWM control of the individual color channels.

[0003] US 2004 / 0217364 A1 concerns a lamp that emits white light and a solid-state emitter for emitting light in the UV wavelength spectrum.

[0004] GB 2 366 610 A relates to an electroluminescent lamp with electroluminescent elements that emit photons in the visible and UV range.

[0005] WO 2011 / 085146 A2 concerns a compact light-mixing LED light generator and a white LED lamp with a narrow beam and high color rendering index.

[0006] WO 2010 / 128419 A1 concerns a light source with a light emitter arranged in a translucent shell.

[0007] WO 2009 / 119038 A2 relates to a molded resin product, a semiconductor light source, a lighting device and a method for manufacturing the molded resin product.

[0008] LED lamps can be used in the form of so-called retrofit LED lamps. These LED lamps have the form and function of, for example, a conventional incandescent bulb, but they contain one or more LEDs or LED modules as the light source. To adjust the supply current, the retrofit LED lamp also has its own driver circuit, which, starting from, for example, a mains voltage supplied via the socket, adapts the supply current to the operating conditions of the LEDs. Therefore, the LED retrofit bulbs can be screwed into ordinary lamp sockets like conventional incandescent bulbs and operated using the supplied mains current.

[0009] However, with LED modules that integrate LED chips on a common substrate, the problem arises that the emitted light from the at least two (or more) LED chips with different emission spectra must be mixed as homogeneously as possible in order to produce white light with adjustable color temperature.

[0010] The known optical elements used for light mixing are diffusers, lenses, reflectors, etc., and their combinations.

[0011] However, using a diffuser, for example as the top of an LED lamp, with the proposed solution presents the problem that negative shadowing effects can occur in an edge area of ​​the diffuser-shaped top. In other words, when this edge area of ​​the diffuser-shaped top is viewed with the human eye, it can be disadvantageous that instead of the mixed spectrum of the at least two LED chips, locally separated spectra or colors are perceived, as if from a backlit lampshade.

[0012] To remedy this problem, the invention generally proposes to provide a diffuser element with at least two shells, comprising a primary diffuser element and a top part acting as a secondary diffuser.

[0013] While the invention is described in the present description with reference to, for example, a candle-shaped retrofit LED lamp element, it is also apparent that the invention can be applied generally to LED modules, in particular to those in which at least two LED chips with different emission spectra are arranged on the same plane. The solution can be integrated into LED luminaires, for example, ceiling lights, spotlights, and table lamps.

[0014] The invention is therefore based on the objective of proposing an LED module with improved color homogeneity of the emission characteristics.

[0015] The problem is solved according to the invention by the features of the independent claims. The dependent claims represent advantageous embodiments of the invention.

[0016] One aspect of the invention provides for an LED module that features: - at least one LED chip mounted on a carrier, - a first ("primary") diffuser element that diffusely scatters light from at least one LED chip, and - a second (“secondary”) diffuser element which, viewed in the direction of light emission, is located outside the first diffuser element and is separated from it, preferably by forming an air gap.

[0017] The LED module can have at least two LED chips with different emission spectra.

[0018] At least one LED chip can be covered with a color conversion agent.

[0019] At least one LED chip produces white, greenish-white or green light through phosphor conversion.

[0020] At least one LED chip produces monochromatic light, e.g. in the red spectrum.

[0021] One or both diffuser elements can be made of a plastic material and / or glass.

[0022] The first diffuser element is shaped like a hood.

[0023] The first diffuser element can be designed in such a way that the edge area of ​​the hood completely surrounds the LED chip(s), at least laterally.

[0024] The wall thickness of the first diffuser element is less in an area above the at least one LED chip than in the edge area of ​​the hood-like diffuser element, which diffusely scatters laterally emitted light from the at least one LED chip.

[0025] The first diffuser element can be mounted on the LED carrier or on an element arranged below the LED carrier, which is preferably designed to dissipate heat.

[0026] The first diffuser element can be mounted mechanically, e.g. by snapping it into place.

[0027] The first diffuser element is spaced away from at least one LED chip, forming an air gap.

[0028] The first diffuser element is spaced at least 1mm, preferably at least 2mm, away from the LED chip.

[0029] One or both diffuser elements can have a homogeneous or inhomogeneous wall thickness between 0.1mm and 5mm, preferably between 1mm and 3mm.

[0030] The first diffuser element can overlap with the side surfaces of the carrier for at least one LED chip.

[0031] The first and / or second diffuser element may contain color conversion agents (“remote color conversion”), which are located directly above one or more of the LED chips, either as an alternative or in addition to a color conversion layer.

[0032] The invention relates to an LED light comprising an LED module of the type mentioned above.

[0033] The invention relates in particular to a retrofit LED lamp comprising a socket for halogen or incandescent lamps and an LED module of the type mentioned above.

[0034] Further advantages, properties and features of the invention will now be explained with reference to the figures in the accompanying drawings.

[0035] They show: Fig. 1a an embodiment of a retrofit LED lamp according to the invention in an exploded view, Fig. 1b the embodiment of Fig. 1a in an assembled manner, and Fig. 2 and Fig. 3 further embodiments of a primary diffuser according to the present invention.

[0036] Fig. 1a and Fig. Figure 1b shows an embodiment of an LED lamp according to the invention with an LED module 7.

[0037] This is a retrofit LED lamp 1 for use in a conventional lamp socket. For this purpose, the bulb 1 has a conventional base 2, for example with an E14, E17, or E27 screw thread. Alternatively, a base designed for a low-voltage connection, such as a G4, G5, or G6 pin base, is also possible. A BA9 or BA15 bayonet base is also conceivable.

[0038] When the retrofit LED lamp 1 is supplied with mains AC voltage or low-voltage voltage via a suitable lamp socket, current adjustment is required for the correct operation of the LED module 7. For this purpose, the lamp has a driver circuit 5. This can include any control circuit conceivable for this application, as known from the prior art. For example, an AC-DC converter for rectifying a mains AC voltage can be considered. Advantageously, a DC-DC converter or other converter can be connected downstream of this to reduce the voltage, current, or power. A switch that is operated by pulse width modulation (PWM) can be used for this purpose. A downstream current limiting circuit, for example using a transistor circuit, can also be considered.

[0039] The LED module 7 can comprise one or more LEDs and / or OLEDs. In particular, fluorescent-converted blue LEDs, RGB LED modules, or any combination thereof can be used. The fluorescent-converted LEDs consist, in particular, of at least one blue LED in which a portion of the emitted blue light is converted into yellow or greenish-yellow light by means of color conversion agents such as phosphor. The use of fluorescent-converted green and / or greenish-white LEDs is also conceivable. Preferably, one or more additional red LEDs (or other monochromatic LEDs) are used, which result in a higher color rendering index and provide a warmer light. The red LEDs can be arranged separately from the fluorescent-converted blue LEDs, or they can be located next to them, so that a portion of their emitted red light is also fluorescent-converted.

[0040] The LED module can be implemented as a COB ("Chip-on-Board") module.

[0041] The LED chips 20, 21 can be covered with a potting compound that is dome-shaped (e.g. as a globe top).

[0042] According to the invention, the LED module 7 is now mounted on an inner layer of a heat sink arrangement. Thus, the LED module and the inner layer 6 are connected over a surface area. The inner layer is as flat as possible in the area where the LED module rests, thereby maximizing the contact area between the inner layer and the LED module, i.e., ensuring full-surface contact. The inner layer can consist of an upper part 6 and a lower part 4. This allows the inner layer to at least partially enclose the driver circuit 5. Advantageously, the lower part 4 has an opening on its underside, through which the driver circuit can protrude or through which a conductor can extend, establishing an electrical contact with the power supply. The upper part 6 also has an outwardly convex shape, providing sufficient space on its inner surface for the driver circuit.On its outer surface, preferably in the center of the bulge, it has a flat area on which the LED module 7 is mounted. The upper part 6 can therefore have an approximately hemispherical shape that is flattened on its upper surface.

[0043] The upper and lower parts 6 and 4 are connected over a large area, thus facilitating heat transfer between the parts and ensuring strong mechanical fixation. A bayonet fitting, a screw thread, or a linear, conical, or stepped connection can be used for this purpose. It is also conceivable that one part could be clipped into the other. The two-part design of the inner layer also simplifies the installation of the LED module 7, as the upper and lower parts can be used separately. Furthermore, the driver circuitry can be more easily integrated. The upper part 6 can also incorporate optical features in the area of ​​the LED module, such as a cavity in which the LED module is mounted. However, it is advantageous if the generated light can exit at a wide angle.

[0044] The inner layer consists of a conductive material such as metal, e.g. aluminum, or plastic.

[0045] Therefore, it also exhibits high thermal conductivity.

[0046] The heat sink assembly further comprises an outer layer surrounding the inner layer, the outer layer having the largest possible surface area. This layer also consists of a top part 8 and a bottom part 3. These are preferably connectable via a thread, thus ensuring high mechanical fixation and high heat transfer through a large common surface area between the parts. The outer layer preferably consists of a non-conductive material such as plastic, or at least of a low-conductivity material with insulating properties. Furthermore, it has a lower thermal conductivity than the inner layer.

[0047] This results in the advantageous effect that heat from the heat source, i.e., the LED module and also the driver circuit, is quickly dissipated by the inner layer and then absorbed by the outer layer. For this purpose, the inner and outer layers are at least partially flush against each other. This is shown in the exemplary embodiment of Fig. 1b is the case for the two sub-parts 4 and 3. Thus, both layers have the largest possible contact surface, ensuring maximum heat transfer between them. For this purpose, the two sub-parts 4 and 3 are also shaped so that they fit together with as little air gap as possible. They can, for example, have a conical shape with tight tolerances. It is also conceivable that, to increase the contact surface area of ​​the outer and inner layers, the layers could have a corresponding, interlocking structure, such as ribs or waves.

[0048] Between the top sections 6 and 8 of the inner and outer layers, there is a space containing the LED module 7. This space may contain optical elements such as a lens. Furthermore, it is possible that this space is at least partially filled, for example with a transparent material, allowing heat dissipation between the two top sections.

[0049] The lower part of the outer layer is connected to the lamp base 2 in such a way that both parts have a large common surface area. This ensures high heat transfer between the outer layer and the lamp base.

[0050] The outer layer is also at least partially translucent or transparent, particularly in the area of ​​the top part 8, so that the light generated by the LED module 7 shines through it. The top part 8 may also have optical properties such as a lens, diffuser particles, or other features.

[0051] The lower part 3 has a thickness of at least 100µm, preferably at least 200µm and more preferably at least 500µm, but preferably at least 1000µm.

[0052] A gap may exist between the inner layer and the driver circuit. This gap may be filled with air. It is also conceivable that it is filled with a potting compound. The potting compound could also form a bond between all parts of the cooling assembly, the lamp base 2, and the driver circuit. This would promote mechanical fixation and heat transfer between the parts.

[0053] Contact between the inner and outer layers can also be established by having the inner layer consist of a metal insert within an outer layer produced by molding. Mechanical fixation can be achieved using standard methods such as ribs or cavities in the metal insert. The outer layer and the metal insert, i.e., the inner layer, can also be bonded using an adhesive such as glue, grease, cement, or an elastomer. The use of plastic inserts is also conceivable.

[0054] The inner layer can have an additional, third layer on its inner surface, at least partially. This layer has insulating properties, thus further protecting the driver circuit from short circuits. It is conceivable that this insulating layer has a recess in the area below the LED module, allowing an electrical connection between the driver circuit and the LED module to be established via the inner, conductive layer. However, it is also conceivable that the third layer is continuous, with both the inner layer and the third layer being pierced by conductors in the area of ​​the LED module for contact purposes.

[0055] As in Fig. 1a and Fig. As shown schematically in Figure 1b, the LED module 7 can have a common circuit board 30 on which at least two LED chips 20 and 21 are mounted. The LED chips 20 and 21 preferably emit light with different spectra. For example, LED chip 20 can emit white light via phosphor conversion, while LED chip(s) 21 can emit monochromatic light, for example, in the reddish range. A particular embodiment relates to the fact that the mixed spectrum of the LED lamp, for example, the color temperature of white light, can be adjusted by appropriately controlling the LED chips 20 and 21 with different spectra.

[0056] However, due to the arrangement of the LED chips 20, 21 on the common circuit board 30, or generally on the same level, the problem arises that negative shadowing effects can occur in an edge region of the diffuser-shaped upper part 8. In other words, if this edge region 40 of the diffuser-shaped upper part 8 is viewed with the human eye, it may be disadvantageous that not the mixed spectrum of the two LED chips 20, 21, but rather locally separated spectra or colors, like a kind of backlit lampshade, can be perceived.

[0057] To remedy this problem, the invention generally proposes providing a diffuser element with at least two layers, comprising a primary diffuser element 10 and the upper part 8 acting as a secondary diffuser. While the invention is described in the present description with reference to, for example, a candle-shaped retrofit LED lamp element, it is also apparent that the invention can generally be applied to LED modules, particularly those in which at least two LED chips with different emission spectra are arranged on the same plane.

[0058] As in Fig. As can be seen in Figure 1a, the primary diffuser element 10 can enclose the LED chips 20, 21 in a hood-like manner. This can be a rounded hood (for example, with a U-shaped or box-shaped cross-section).

[0059] As in Fig. 1a and Fig. As can be seen in Figure 1b, the hood-shaped primary diffuser element 10 is designed such that the edge region of the hood completely surrounds the LED chips 20, 21, at least laterally. In the example shown, Fig. 1a, Fig. 1b the hood-shaped primary diffuser element 10 is extended even further down, namely onto the heat sink body 6, on which in turn circuit board 30 of the LED module 7 is mounted in thermal contact.

[0060] Both the upper part 8 and the primary diffuser element 10 can be made of a plastic material, for example, polycarbonate, polystyrene, polyester, polymethyl methacrylate (PMMA), or their copolymers. The diffuser elements can contain plastic particles, the refractive indices of the particle core and particle shell preferably not being the same. The plastic particles can be dispersed in a polymer matrix.

[0061] The two diffuser elements can also be made of glass or glass-plastic mixtures.

[0062] The secondary diffuser element (upper part) 8 is preferably spaced from the primary diffuser element 10 by forming an air gap with an average minimum distance of, for example, at least 1 mm, preferably at least 3 mm.

[0063] The primary diffuser element and the secondary diffuser element can be manufactured as a single, integral, double-shell-looking piece.

[0064] The primary diffuser element 10 is preferably spaced at a homogeneous or inhomogeneous distance of at least 1 mm, more preferably at least 2 mm, again preferably forming an air gap (a space filled with gaseous medium) from the nearest LED chips 20, 21.

[0065] The wall thickness of the primary diffuser element 10 and / or the upper part 8 acting as a secondary diffuser can each be homogeneous or inhomogeneous. The homogeneous or inhomogeneous wall thickness can be between 0.1 mm and 5 mm, preferably between 1 mm and 3 mm.

[0066] With regard to the primary diffuser element 10, for example, the area 50 of the primary diffuser element 10 located above the LED chips 20, 21 can have a reduced wall thickness compared to the area 60 of the hood-like primary diffuser element 10.

[0067] The primary diffuser element 10 can be mechanically attached (by clips, snapping, gluing, etc.) to a carrier, for example also to the circuit board 30 of the LED module 7.

[0068] As in Fig. 2. As can be seen, the primary diffuser element can differ from the box shape in Fig. 1a, Fig. As shown in Figure 1b, the primary diffuser element 11 may also be dome-shaped.

[0069] In Fig. Figure 3 shows an embodiment in which the primary diffuser element 12 is arranged directly on the circuit board 30 of the LED module 7, which also carries the LED chips 20, 21.

[0070] Light from the LED chips 20, 21 is diffusely scattered by the primary diffuser element 7, 11, 12. Since the human eye cannot look directly at the primary diffuser element 10, 11, 12 when the LED lamps are mounted, but only at the secondary diffuser element located outside it in the form of the upper part 8, color separation is advantageously no longer perceptible. Thus, even when directly viewing the edge region 40 of the secondary diffuser element 8, the human eye will perceive a mixed spectrum of the LED chips 20, 21, but no spatially separated color effects.

[0071] The first and / or second diffuser element may contain color conversion agents (“remote color conversion”), which are located directly, i.e. without an air gap, over one or more of the LED chips, either as an alternative or in addition to a color conversion layer.

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