RU2569312C2 - Light-emitting diode light source (versions) - Google Patents

Light-emitting diode light source (versions) Download PDF

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RU2569312C2
RU2569312C2 RU2013117665/07A RU2013117665A RU2569312C2 RU 2569312 C2 RU2569312 C2 RU 2569312C2 RU 2013117665/07 A RU2013117665/07 A RU 2013117665/07A RU 2013117665 A RU2013117665 A RU 2013117665A RU 2569312 C2 RU2569312 C2 RU 2569312C2
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Сергей Александрович Панин
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Сергей Александрович Панин
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Abstract

FIELD: physics, optics.
SUBSTANCE: invention relates to electronic engineering. In a white light-emitting diode (LED), having a housing and a reflector, the housing is made of heat-scattering material, the inner part of the housing is in the form of at least one segmented reflector which forms a directional pattern of light flux distribution, having a layer of reflecting material consisting of at least one layer and a layer of light-transmitting dielectric material consisting of at least one layer. At least one LED chip is mounted inside the housing. The housing is covered on the top by a converter which is made from at least one layer of light-transmitting material. A layer of a point phosphor is deposited on at least one side of the converter. The side of the converter directed towards at least one LED chip is coated by a layer of reflecting material consisting of at least one layer.
EFFECT: providing high efficiency of a white LED light source with a remote converter, providing high colour homogeneity and enabling specification of the directional pattern of the emitted light flux with a small size of the white LED light source.
29 cl, 9 dwg, 1 tbl

Description

FIELD OF THE INVENTION

The invention relates to the field of electronic technology, namely to light emitting diodes (LEDs), and can find application in semiconductor technology in the design and manufacture of LEDs.

State of the art

Solid state lighting technology is beginning to conquer the white lighting market thanks to the latest advances in the development of efficient LEDs, especially nitride (InGaN), and the highest achievable lighting efficiency among all known white light sources. LED solutions are widely used in those lighting devices, such as linear and street lamps, in which the illuminator is relatively large and highly heated LEDs can be distributed so as to ensure efficient heat removal from them. The development of LED substitutes for traditional incandescent and halogen lamps with a small form factor with a high luminous flux, in view of the significant prospects in solving the problem of energy conservation, is one of the most urgent modern scientific and technical problems, but its solution is very difficult due to volume limitations for the placement of control electronics ( drivers) and a relatively small surface to remove the heat generated by the LEDs in such lamps. White LEDs often contain blue LEDs coated with YAG: Ce phosphorus. Powerful (one watt or more) blue LEDs have an efficiency of about 30-50% more than white LEDs. In addition, it is believed that when phosphorus converts blue light into yellow light in white LEDs, approximately 20% of the incident light energy is spent on phosphorus heating. Technical specifications indicate that the power drop of blue LEDs is approximately 7-10% when encapsulating the LED crystal and 7-10% at 25-125 ° C, while the power drop of white LEDs is approximately 15-20% at the same temperature itself. Thus, in high-power white LEDs there are significant restrictions on heat and light fluxes.

The basis of any LED fixture designed to replace standard fixtures is LED crystals. White light is often obtained by mixing the radiation of a combination of LED crystals with different colors of radiation, for example, blue, green and red or blue and orange, etc.

However, in recent years, LED-based white light sources with photoluminophore converters that emit yellow or orange (red) radiation when absorbing blue or UV radiation from an LED crystal have come to the fore in terms of use. Such a device comprises an LED crystal emitting primary relatively short-wavelength radiation, and a conversion phosphor medium irradiated with said relatively short-wavelength radiation, which, when irradiated with said relatively short-wavelength radiation, is excited to emit a second, relatively longer-wavelength radiation in response. For example, monochrome blue or UV radiation emerging from a crystal is converted to white light by packing the crystal into organic and / or inorganic phosphors in a polymer matrix.

A device is known for a white light source based on LEDs with a photophosphor converter, which includes an LED nitride crystal, which, when excited, emits primary blue radiation. The crystal is placed on the conductive frame of the reflector bowl and is electrically connected to the conductors. Conductors supply electrical power to the crystal. The crystal is coated with a layer of transparent resin, which includes a conversion material to convert the radiation wavelength. The type of conversion material used to form the layer may be selected depending on the desired spectral distribution of the secondary radiation that is produced by the conversion material. The crystal and fluorescent layer are covered with a lens. The lens is usually made of clear epoxy or silicone. When a white light source is operating, an electric voltage is applied to the crystal, and primary radiation is emitted from the upper surface of the crystal. Part of the emitted primary radiation is absorbed by the conversion material. Then, the conversion material in response to the absorption of the primary light emits secondary radiation, that is, converted light having a longer wavelength peak. Part of the emitted primary radiation, which remains not absorbed, is transmitted through the conversion layer together with the secondary radiation. The lens directs the unabsorbed primary radiation and the secondary radiation in a general direction, like outgoing light. Thus, the exit light is a complex light that is composed of the primary radiation emitted by the crystal and the secondary radiation emitted by the conversion layer. The conversion material can also be configured so that only a small fraction or all of the primary light does not leave the device, as in the case of a crystal that emits UV primary light combined with one or more conversion materials that emit visible secondary light (US Pat. No. US 6351069 IPC H05B / 3314, published on 02.26.2002).

The aforementioned known device, in which a phosphor layer is formed on the surface of the LED, has several drawbacks, namely, it is difficult to achieve color uniformity due to the phosphor being in direct mechanical, optical and thermal contact with the surface of the LED, which leads to significant changes in length light paths depending on the angle of radiation propagation through the thickness of the phosphor layer, in addition, the high temperature from a heated LED undesirably changes the color coordinates of the phosphor and dit to its degradation. There is also a high thermal resistance crystal radiator.

To eliminate the aforementioned disadvantages, white light sources with a wavelength converter remote from the LED are proposed. A light emitting device based on this principle is known, in which the white light source includes a shell formed by a transparent medium with an internal volume. Said medium may be formed from any suitable light transmitting material, such as a transparent polymer or glass. Said medium contains in its internal volume an LED crystal located on the base. The first and second electrical contacts are connected to the emitting and back sides of the LED chip, respectively, and to the emitting side of the LED chip, connected to the first electrical contact by a conductor. Fluorescent and / or phosphorescent components, or mixtures thereof, in other words, a phosphor medium, which converts the radiation emitted by the LED side, into white light, are associated with the light-transmitting medium. The phosphor is dispersed in the shell of the sweeping transmission medium and / or placed in the form of a film coating on the inner wall of the surface of the shell. Alternatively, the phosphor may be a coating on the outer wall of the assembly shell if the shell is used solely under environmental conditions in which such an outer coating can satisfactorily be maintained (for example, where it is not subject to abrasion or degradation). The phosphor can, for example, be distributed in a polymer or molten glass, from which the shell is then formed to ensure its homogeneous composition and to ensure light exit from the entire surface of the shell (US Patent No. US 6,600,175, IPC H01L 33/50, published July 29, 2003) .

Also known is a white LED long lamp with a remote converter of cylindrical shape. This lamp includes a linear heat sink, a plurality of LEDs mounted on the heat sink along the long side of the heat sink, and a light-emitting shade installed on the heat sink in line with the LED, where the semicircular section of the shade located opposite the LED includes a phosphor that is excited by light from the LED . The heat sink is made of a heat-conducting material, such as aluminum. The ceiling is made of a transparent material, such as glass or plastic. The phosphor can be applied as a coating on the inside of the ceiling or introduced into the coating material. Phosphor-free flat parts that are attached to the heat sink on either side of the LEDs have internal reflective surfaces, such as aluminum coatings that reflect the light incident on them from the LEDs, to a portion of the lampshade (US Pat. No. 7,618,157 B1, IPC F21V 29/00 , published November 17, 2009).

The conversion layer may include phosphor material, quantum dot material, or a combination of such materials, and may also include a transparent base material in which the phosphor material and / or quantum dot material are dispersed.

It is known that layers that contain powder phosphors can transmit, absorb, reflect and scatter light incident on them. When such a layer scatters light, it can also transmit, absorb and reflect part of the scattered light.

In this regard, a common drawback of the above two inventions is that the radiation excited in the phosphor grains when exposed to LED radiation, as well as the reflected LED radiation, is inevitably partially absorbed in the phosphor layer and on the internal elements of the device, which leads to a decrease in the source efficiency white light.

A study is known in which blue LED crystals were fixed by means of silver-containing glue to a crystal holder with gold conductors. The LED housings are 5x7 mm in size and the crystal size is 24 mils (thousandths of an inch), which is 600 × 600 μm square in shape with a thickness of 220 μm. Then the radiation flux was measured. Were selected LED LED naked blue crystal cases with a power output of 123 mW at a current strength of 150 mA to ensure the same initial conditions. During the study, the ratio of the fractions of radiation propagating back and forth from the conversion layer of the YAG: Ce phosphor excited by blue radiation with a wavelength of about 470 nm, which is converted to radiation in the yellow wavelength range, was determined. It also turned out that more than 60% of the light emitted and reflected by the conversion layer propagates back to the excitation source and most of this light is lost within the LED assembly. This study showed that even in the case of the phosphor http: //yag.ce/ (yttrium aluminum garnet doped with cerium) with an optical refractive index of 1.8 mixed in an epoxy resin with an optical refractive index of 1.6 at a phosphor density of 8 mg / cm 2 , which allows you to create a balanced white light, the proportion of radiation directed backward and transmitted forward, including blue and yellow radiation, are 53% and 47%, respectively, and for only yellow radiation 55% and 45%, respectively. Thus, the photon-scattering housing developed in the course of this study can increase the efficiency of light output by 61% compared to a conventional phosphor white LED. It is also known that a case with a scattering lens can increase light efficiency and reduce the reabsorption process in an insulated phosphor design (Improved performance white LED. Narendran, N. Fifth International Conference on Solid State Lighting, Proceedings of SPIE 5941, 45-50. Bellingham , WA: International Society of Optical Engineers, 2005 see Internet resource http://www.lrc.rpi.edu/programs/solidstate/pdf/narendranSPIE2005.pdf).

The disadvantages of the aforementioned developed case are that it does not solve the problem of cooling the LED crystal, there are high losses of light flux through the lens forming the radiation pattern.

A prototype of the claimed utility model is a device according to patent application US 20120140466, in which an LED lighting device adapted to emit light with a selective radiation angle taken relative to the radiation axis of the lighting device comprises a cup-shaped (parabolic) reflector and a plurality of LEDs, the LEDs being made so that during operation each emits light in a certain radial direction to the axis of radiation of the lighting device, and the axis of emission of LED light is made at an angle of at least 40 degrees to the radiation axis of the lighting device. In preferred embodiments, the LEDs are configured such that their radiation axis is substantially perpendicular to the radiation axis of the lighting device, and the reflector comprises a corresponding portion of a parabolic reflective surface associated with the corresponding one of said LEDs (US Patent Application No. US 20120140466 (A1), IPC F21V 7/00, published 07/07/2012).

The above prototype has the following disadvantages. Due to the fact that LEDs of the blue and ultraviolet spectrum that are encapsulated using conventional technology are used, there are thermal (due to the large number of thermal transitions of the crystal-radiator LEDs) and light (with traditional encapsulation of LEDs, blue losses of 7-10% of the light flux and losses associated with with high temperature LED crystal, up to 10%) loss. A sophisticated reflector design is used, which consists of several parts. This solution is applicable only for circular radiation patterns, and accordingly has limited use. The aluminum circuit board or substrate on which the LEDs are mounted does not have reflectivity, which significantly increases light losses. Has no solution to increase the quantum yield of the LED crystal.

Disclosure of the claimed invention

The technical result of the claimed utility model is the ability to set the radiation pattern of the emitted light flux at a small size of the LED light source. An additional technical result is the provision of high color uniformity of the emitted light and high efficiency of the LED light source. The ability to set the pattern of the emitted light flux at a small size of the LED white light source is achieved through the use of a segmented reflector.

High color uniformity is achieved through the use of a segmented reflector and a phosphor converter.

The high efficiency of the LED white light source is achieved through the use of a segmented reflector, a point phosphor converter, heat dissipation by the LED casing (reducing the number of thermal transitions) and the possibility of using various types of LED crystals.

Brief Description of the Drawings

FIG. 1 is a schematic sectional view of a light emitting diode.

FIG. 2 is a schematic sectional view of a light emitting diode using a dissecting element.

FIG. 3 is a schematic sectional view of a light emitting diode with a spherical reflector shape and several LED crystals (matrix of LED crystals).

FIG. 4 is a graph of reflectance of silver-based materials according to Almeco Group.

FIG. 5 is a plan view of a phosphor converter with spot application of a phosphor.

FIG. 6 is a cross-sectional view of a phosphor converter with spot application of a phosphor.

FIG. 7 is a graph of correlated color temperature versus angle using various forms of phosphor.

FIG. 8 is a graph of the relationship between the ratio of the intensities of yellow and blue light versus the angle when using various forms of the phosphor.

The implementation of the invention

In accordance with FIG. 1, the light emitting diode (matrix of light emitting diodes) includes a housing 1, the inner part of which is made in the form of a segmented reflector 2, consisting of a layer 3 of reflective material and a layer 4 of light transmitting dielectric material, at least one crystal 5 of a light emitting diode (LED), fixed by means of a light-transmitting heat-conducting silicone or epoxy composite material 6 and a converter 7. The housing 1 is made of heat-conducting material such as polymers, ceramics, metal, etc. An LED crystal 5 intended to emit blue primary radiation 8 is mounted in a recess in the base of the housing 1, on a light-transmitting heat-conducting silicone or epoxy composite material 6 so that the lower surface of the crystal (crystal matrix) 5 LED has a minimum clearance with a layer 4 of light-transmitting dielectric material of the segmented reflector 2. This allows you to increase the power of the quantum yield of the crystal (crystal matrix) 5 LED. A translucent heat-conducting silicone or epoxy composite material 6 with a layer thickness of less than 10 μm is deposited on the radiating surface of the crystal (crystal matrix) 5 LEDs, which protects the crystal (crystal matrix) 5 LEDs from oxidation and also does not prevent the penetration of rays to reflector 2.

On top, the housing 1 is covered with a converter 7 made of a phosphor, which is designed to convert the primary radiation 8 of blue, secondary radiation 10 of blue, etc. in white radiation.

The proposed LED operates as follows.

The primary radiation 8 of the blue color of the crystal (matrix of crystals) 5 LEDs is formed in a segmented reflector 2 into the luminous flux of maximum intensity and a predetermined radiation pattern and is directed to the surface of the phosphor converter 7, where part of the primary radiation 8 of blue color is converted to white radiation, and about 60 % of radiation 9 is reflected from the surface of the grains of the phosphor of the phosphor converter 7 and returns to the layer 3 of the reflective material of the segmented reflector 2, where the reflection is converted to the rays of the secondary radiation 10, and again directed to the surface of the phosphor converter 7, where part of the secondary radiation 10 of blue is converted to white radiation, and part is reflected and returned to the surface of the reflector 2, in which it is again formed and reflected, being converted into rays of tertiary radiation, etc.

The segmented reflector 2 can also consist of two or more reflectors, for example, the first one forms a predetermined radiation pattern of the primary light flux 8 of the crystal (crystal matrix) 5 LEDs and is located at the recess of the housing of the segmented reflector 2, and the second is a reflector forming the radiation pattern of the secondary radiation 10 from the rays of the light flux 9 reflected by the Converter 7.

The efficiency of the output of the luminous flux of segmented reflectors is two times greater than that of parabolic, conical and other reflectors.

To achieve the necessary radiation patterns, a segmented reflector can be made square, rectangular, round, etc., the reflecting surface can be made in the form of:

- ellipsoid, parabola, etc. with an optical surface, smooth, with facets or made in the form of segments;

- a stepped reflector, which is a stage consisting of parabolic elements or elements whose shape combines a parabola and an ellipse;

- homophocal or confocal reflectors, consisting of the primary and secondary reflectors;

- a multifocus reflector using reflector parts, the shape of which combines a parabola and an ellipse, in which many focal points are formed;

- faceted reflector;

- any combination of reflector elements specified in the previous paragraphs.

To increase the reflection efficiency of the primary blue radiation 8 emitted by the crystal (crystal matrix) 5 LEDs and the reflected radiation of the phosphor converter 7 on the surface of the segmented reflector 2, secondary radiation 10, etc., it is necessary to apply a high coefficient coating on the surface of the segmented reflector 2 optical reflection. Examples of coating materials with a high optical reflectance are silver, aluminum, dichroic coatings and aluminum combined with a dichroic coating to increase the optical reflectance of aluminum, and materials such as titanium oxide and alumina formed by the sol-gel method.

In the proposed LED design, the reflective material layer 3 is made of 99.99% pure silver, having a high reflectivity for light with a wavelength of 440-850 nm (up to 96%) and a heat-conducting characteristic of 430 W / m * K.

To prevent oxidation of the layer 3 of the reflective material, a layer 4 of light-transmitting dielectric material (for example, SiO 2 , SiO, etc.) having high light transmittance is applied to it. Layer 3 of reflective material and layer 4 of light-transmitting dielectric material are applied, for example, by physical vapor deposition. According to the data published by Lumen LLC, Russia (presentation “Remote phosphor. Opportunities and prospects”, M. Marakulin, Saransk, 2012, see Internet resource http://lumeon.ru/index.php? route = information / spec & spec id = 11) and Intematix Corporation, USA (Mixing Chamber Design Considerations for ChromaLit ™ Remote Phosphor Light Sources, 10.01.2013, see Internet resource http://www.intematix.com/uploads/files / intematix mixing chamber design for chromalit.pdf), an increase in the optical reflectance of the segmented reflector surface from 95% to 99% gives an increase in luminous flux by 19%.

The table shows the data of the company Lumen LLC, Russia and Intematix Corporation, USA.

The reflection coefficient of the walls of the mixing chamber Improving light emission with a remote phosphor system 95% eleven% 96% fifteen% 97% 19% 98% 22% 99% thirty%

From the data given in the table, it is seen that an increase in reflectivity of the reflector by 4% leads to an increase in luminous flux by 19%. According to the Almeco Group company (Fig. 4), at a wavelength of 455-465 nm, silver-based material V98100 has a reflectivity of 96% (99% for the entire spectrum of visible light is indicated on the material data, but actually at a wavelength of 455 -465 nm reflectance is only 96%). By applying a layer 4 of a light-transmitting dielectric material, which is also a protective layer, to a layer 3 of silver reflecting material, silver film of 124 nm thick SiO 2 , the reflectivity of segmented reflector 1, in the wavelength spectrum of 455-465 nm, increases to 98%. The optical reflection coefficient of silver coated with a SiO 2 layer is described in the scientific work Polarization compensating protective coatings for TPF-Coronagraph optics to control contrast degrading cross polarization leakage Kunjithapatham Balasubramanian *, Daniel J. Hoppe, Pantazis Z. Mouroulis, Luis F. Marchen, and Stuart B. Shaklan Jet Propulsion Laboratory, California Institute of Technology. Thus, the use of applying a layer of SiO 2 in the proposed LED gives an increase in the luminous flux of the white light of the LED by another 15-20% (compared with the calculated data shown in the table).

A further increase in the efficiency of LEDs is possible due to the deposition of additional films of metal oxides and fluorides having dielectric properties. Thus, it is possible to increase the optical reflectance of the segmented reflector 2 to 99.9%.

There are various patterns of the distribution of light emitted by the LED, such as the distribution of the "bat" distribution according to Lambert and distribution with side lobes. To calculate the design of a segmented reflector, it is necessary to take into account the radiation pattern of the light emitted by the LED crystal (crystal matrix). When distributing the type of "side lobes" it is easier to form a given radiation pattern of the light emitted by the LED crystal (crystal matrix).

In accordance with Figure 2, when the radiation pattern of the type of "Lambert distribution" or "bat" for wide-focus radiation patterns of LEDs, when designing a reflector, it is proposed to use element 11 for dissecting the light flux (dissecting element 11), consisting of any heat-scattering material with a deposited layer 12 of reflective material and a layer 13 of light-transmitting dielectric that protects the layer 12 of the reflective material from oxidation. The use of a dissecting element reduces the luminous flux of the crystal (crystal matrix) 5 LED by 1% to 3%, depending on the reflectivity of the said dissecting element 11. Depending on the desired radiation pattern, the dissecting element 11 may have the shape of a cone, a pyramid etc. To enhance the luminous flux and complete the radiation pattern of the light flux, the upper part of the dissecting element 11 is a segmented reflector.

In accordance with Fig. 3, in order to achieve the necessary radiation pattern, when creating an LED array, any bottom shape of a segmented reflector 2 (trapezoidal, triangular, spherical, etc.) can be used.

To create circular patterns of the distribution of light with an angle from 150 degrees to 350 degrees vertically (for example, for use in non-directional lamps), a design of at least two segmented reflectors (depending on the required luminous flux and power of the LEDs used), covered a single phosphor converter 7 having the shape of a hemisphere, half cylinder, trapezoid, etc.

For example, a standard lamp with an E27 base having a radiation angle of 360 degrees horizontally and 270 degrees vertically, when using three LED crystals, it will consist of three segmented reflectors, each of which forms a radiation pattern of 120 degrees horizontally and 135 degrees vertically when using four LED crystals - from four segmented reflectors, each of which forms a light distribution pattern of 90 degrees horizontally and 135 degrees vertically ticked, when using five LED crystals - from five segmented reflectors, each of which forms a radiation pattern of 72 degrees horizontally and 135 vertically, etc.

To calculate the optical model of LEDs, namely, to calculate the absorption, optical reflection, transmission, fluorescence, scattering of the rays of the light flux and to calculate the segmented reflector, you can use the computer-aided design (CAD) system.

For LED crystals emitting light with a different wavelength, optical and thermal losses also occur with conventional encapsulation. When using the encapsulation method proposed in this description, the luminous flux increases, a predetermined pattern of light distribution is formed, and heat removal from the LED crystal (crystal matrix) is improved.

If the LED crystal emits light with a wavelength of less than 440 nm or more than 850 nm, then materials having a maximum reflection coefficient (99.9%) are used for the layer 3 of reflective material for the required radiation wavelength of the encapsulated LED crystal (matrix of crystals).

The housing 1 of the LED is made of heat dissipating material. This design uses heat dissipating polymer composites (TRPC). LED housing 1 can be made of thermally conductive dielectric composites using additives such as aluminum oxide (thermal conductivity up to 5 W / (m * K)), aluminum nitride (thermal conductivity up to 20 W / (m * K)), hexagonal boron nitride (thermal conductivity up to 100 W / (m * K)), graphite (has a thermal conductivity of more than 200 W / (m * K), but it has high electrical conductivity), etc. The manufacture of the LED housing 1 from heat-scattering polymer composites can reduce the consumption of silver used in applying the layer 3 of reflective material due to the low roughness achieved in the manufacture of castings (almost a mirror surface).

The silver technologies used when applying layer 3 of the reflective material of the segmented reflector 2 can also be saved by the use of the following technologies: a layer of any highly thermally conductive inexpensive metal (for example, aluminum) is applied to the surface of the body 1, which reduces the roughness of the casting, then a silver layer and layer 4 are applied to the metal layer light transmitting dielectric material.

In addition, the claimed invention provides the ability to create current-carrying paths for the crystal (matrix of crystals) of the LED directly on the surface of the segmented reflector, which allows you to use the method of automatic installation of crystals on a chip-on-board. To create 2 current-carrying tracks on the reflective surface of a segmented reflector, first a copper layer is applied to the reflector surface with a thickness necessary for the maximum current of the crystal (crystal matrix) 5 LEDs, which also reduces the roughness of the casting. Then a layer 3 of reflective material (for example, silver) is applied. Next, conductive paths are cut by a laser machine and a layer 4 of light-transmitting dielectric material is deposited, then, using a laser machine, a layer 4 of light-transmitting dielectric material is evaporated in the places of formation of the contact pads, where LED crystals are then placed.

In addition, the manufacture of LEDs of the proposed design allows you to further remove heat from the crystal (matrix of crystals) of the LED. Layer 6, made of a translucent heat-conducting silicone or epoxy composite material (thermal conductivity up to 5 W / (m * K)) with a thickness of less than 10 microns, gives a low thermal resistance. Layer 4, made of light-transmitting dielectric material, has a thermal conductivity of 1.2 W / (m * K), which with a layer thickness of 123 nm makes it possible not to take into account the thermal resistance of layer 4. Layer 3 of reflective material made of 99.99% pure silver (thermal conductivity 430 W / (m * K)), effectively removes heat from the crystal (matrix of crystals) 5 LEDs into the housing 1, made of a heat-dissipating polymer composite.

To further increase the external quantum efficiency of the pn junction of the 5 LED crystal, it is necessary to reduce the thickness of the LED crystal substrate (matrix of crystals) by any known technology, for example, scribing, and then when installing a crystal with a refined substrate, the light flux of the crystal (crystal matrix) increases in this design ) LED by reducing the thermal resistance of the substrate and increasing the light transmission of the substrate (silicon carbide film passes up to 50% of the light flux in depending on the structure, and with a thickness of 0.2 μm it can reach 90%).

The recess at the bottom of the segmented reflector 2 and the housing 1 can be used as a base for installing LED crystals obtained by elevator-off (LLO) technology, LED crystals obtained by the technology of thin-film inverted crystals (Thin Film Flip Chip - TFFC), and crystals LED made by other technologies.

Phosphor converter design 7

The phosphor converter 7, which covers the LED housing 1, is a light-converting element and is made of light-transmitting material, for example, polymer, polymethyl methacrylate, polycarbonate, etc., on which a layer of a phosphor mixture is applied, and made in the form of a plate or product of a more complex spatial shape and geometry, for example, a hemisphere, half cylinder, etc. The applied phosphor layer can be continuous, point (in the form of spheres, hemispheres, etc.), linear (in the form of cylinders, half-cylinders, etc.) and any other shape.

In FIG. 5 and 6 depict the phosphor converter used in the proposed LED. The phosphor converter 7 is a point converter. The base 14 of the phosphor converter 7 is made of light transmitting material such as a polymer, polymethyl methacrylate, polycarbonate, and the like. On the basis of the converter 14 7 are the points of the phosphor 15, designed to convert blue radiation into white light. The lower side of the converter 7 (the side directed to the crystal (crystal matrix) 5 LED) is covered with a metal layer 16 and a layer 17 of reflective material around the points 12 of the phosphor. The entire bottom side of the base 14 is covered by a plate 18 made of light-transmitting silicone or epoxy material.

Between the edges of the points of the phosphor 15 and the edges of the layers 16 and 17 there are gaps 19, designed to transmit blue radiation.

In the proposed design, to reduce the roughness of the light-transmitting material from which the base 14 of the converter 7 is made, a metal layer 16, for example, aluminum, copper, etc., is applied to the lower side of the base 14, and then a layer 17 of reflective material is applied to the metal layer 16 having a high reflectivity, for example, silver with a reflectivity of up to 99%.

Then, on the base 14 of the converter 7, points 15 of a phosphor of a predetermined shape are applied.

The phosphor base 14 is connected to the plate 18 by means of a light transmitting silicone or epoxy material. When forming the converter, it is necessary to leave gaps 19 for the output of blue and yellow radiation between the points 15 of the phosphor and the layers 16 and 17, which allows you to save the angular ratio of the correlation color temperature. The phosphor points 15, as well as the dimensions of the gaps 19 between the points 15 and the layers 16 and 17, can be optimized in terms of shape, layer thickness, size, and reducing or increasing the concentration of the phosphor to increase the overall light output and create the necessary LED radiation pattern. Instead of metals, any materials having a high optical reflection coefficient in the blue emission spectrum can be used.

Instead of a plate 18 of light-transmitting material, a layer of SiO 2 can be applied, which will increase the reflectivity of the layer 17 of reflective material.

The metal layer 16 and the reflective material layer 17 have a high thermal conductivity. They effectively remove heat from the phosphor, the conversion efficiency of blue light to white in the converter will decrease with an increase in the temperature of the converter of 0.03% / K, as confirmed by the study Determining phosphors effective quantum efficiency for remote phosphor type led modules, A. Keppens.

The use of the proposed point phosphor converter allows to increase the luminous flux efficiency compared to a solid phosphor, due to heat removal from the phosphor and at the same time allows to reduce the angular dependence of the correlated color temperature (compared to a solid phosphor), which is necessary when creating wide-focus distribution patterns light LED lamp. The above advantages are clearly visible in FIGS. 7 and 8, where the use of a conventional remote phosphor converter and a point remote phosphor converter is compared.

To connect the housing 1 and the phosphor converter 7, it is necessary to use heat-conducting composite materials. For better heat transfer of the phosphor converter 7 is a groove 20 (Fig.6) with an open layer of silver.

To create LED modules (multi-chip LED matrix) for aggressive environments and in anti-vandal design, the light-converting phosphor converter is glued with a transparent thermally conductive silicone or epoxy composite material with polished tempered glass, for example, BOROFLOAT® (light transmission up to 94% according to Abrisa Industrial Glass, USA (see the Internet resource http://www.us.schott.com/borofloat/enqlish/index.html)). The main loss of light transmission in glass is the air-glass-air transition (approximately 4-5%). Loss of light transmission in the proposed design will be from 1-5% depending on the used transparent composite material and the quality of bonding.

If the LED crystal emits light with a wavelength of less than 440 nm and more than 850 nm, then materials having a high light transmission coefficient are used as light transmitting materials for the required wavelength of the encapsulated LED crystal (matrix of crystals).

For effective heat removal from the LED, for example, a cellular radiator consisting of a base can be used, around the outer surface of which radiator fins are fixed. Transverse plates are fixed on the radiator fins. Adjacent transverse plates located in one section of the radiator formed by the radiator fins are interconnected by connecting plates, thus forming a honeycomb structure. At the same time, a transverse platform is located inside the radiator base, on which a thermally loaded LED is located.

To increase the efficiency of LED luminaires and increase their service life, it is proposed to use a stabilized current source based on a transistor single-stage AC / DC converter with power factor correction and the use of series-parallel schemes of ceramic capacitors.

This scheme of a single-stage stabilized current pulse source (driver) has several advantages over traditional two-stage converters with input bridge rectifiers: when using the appropriate keys, their efficiency can exceed 98%, and the power factor can reach 0.999, and the total harmonic coefficient (THD) can be no more than 2 %; they are smaller and lighter; have a lower cost of magnetic cores; characterized by one hundred percent use of all components both with a negative and a positive half-wave of the input voltage. They have more stable output voltage and current characteristics compared to linear and flyback converters. The principle of operation of such a converter is described in the sources of Slobodan Cuk. Modeling, Analysis and Design of Switching Converters, PhD thesis, November 1976, California Institute of Technology, Pasadena, California, USA. and Slobodan Cuk, R. D. Middlebrook. Advances in Switched-Mode Power Conversion, Vol. 1, II, and III, TESLAco 1981 and 1983.

There are a large number of integrated circuits (ICs) of power correctors and current regulators, therefore, in this work, general solutions are presented.

One of the main requirements is to ensure the compactness and adaptability of the stabilized current source. It is proposed to use a dielectric TRPC as the base material of a printed circuit board in the design of a stabilized current source, conductive tracks are made by the chemical method, the method of physical vapor deposition of metals, or by any other method. Given that this luminaire has limited space for the location of the power source, the circuit board is traced for surface mount components.

Examples of stabilized current sources used

Example 1. A stabilized current source without galvanic isolation is advisable to use in devices of low power. The scheme of such power sources must be calculated using elements with a large supply of power. In this circuit, the diode bridge is replaced by two MOSFIT transistors with a resonant circuit, consisting of a resonant inductor L1 and a resonant capacitor C1. Using this switching method leads to the fact that the constant voltage transmission coefficient is determined only by the parameters of the duty cycle. Both with a negative and a positive input voltage, the duty cycle coincides with the constant-voltage transmission coefficient of a conventional boost converter, which automatically leads to rectification of the mains voltage without using an input bridge rectifier, which leads to the creation of a transistor converter, in which this circuit has all components - three keys, an input inductor L1, an inductor L2 and a capacitor C1 of the resonant circuit - are used 100%, since they all take part in the transformation of both positive and negative half wave of the AC input voltage.

Example 2. A stabilized current source with galvanic isolation. It consists of a resonant circuit, which includes a coil L1 and two capacitors C1 and C2. While the first capacitor C1 is charging, the second capacitor C2 is discharged. In the second half of the cycle, the process repeats: the first capacitor C1 is discharged, and the second capacitor C2 is charged. Therefore, the resulting ripple voltage on the series capacitors is equal to twice the ripple voltage on each capacitor. The isolation transformer in this circuit uses both the positive and negative parts of the hysteresis loop. The inductor L1 and the primary winding of the transformer are turned on in parallel to each other. Therefore, despite the excitation by alternating voltage, both elements - both the inductor L1 and the transformer Tr1, have identical forms of variable signals, which allows them to be placed on one core. In addition to isolation by transformer Tr1, this solution adds flexibility to the circuit, since it allows lowering the output DC voltage to any given value by changing the number of turns in the windings of the isolation transformer.

Example 3. A stabilized current source with galvanic isolation and a neutral wire. One of the early DC transmission systems was the three-wire system proposed by Edison, with one neutral wire in which there is no current, compared to two-wire DC systems in such systems there was a doubling of the transmitted power with the same amount of copper used, i.e. they are more preferable since the transistor converter is capable of generating an output DC voltage of both positive and negative polarity. Changing the polarity of both rectifiers to the opposite constant voltage at the output of the converter will become negative. To further reduce size and weight, as well as to increase the efficiency (Efficiency) of a pulsed source of stabilized current, it is necessary to use the integration of two separate converters into one converter with two outputs, having one L1 inductor, and one active key (see http : //powerelectronics.com/power_management/regulator_ics/true-bridgeless-pfc-http: //http.7/powerelectronics.com/power_managementyregulator_ics/true-bridgeless-pfc-converter-part2-201008/ and http: // http. v / www.russianelectronics.ru / developer-r / review / micro / doc / 55155 /)

In all the schemes presented above, both active power correctors and passive ones can be used. ICs of current regulators can be used both with built-in MOSFIT transistors and with external ones.

In most switching power supplies, today they use electrolytic capacitors, which have a short service life (maximum 10,000 hours) and a large variation in parameters (+/- 20%). Therefore, for a long service life of power sources (100,000 hours), it is necessary to use ceramic or tantalum capacitors. It should be borne in mind that ceramic capacitors have the following differences from tantalum:

- lower impedance value and better ESR filtering properties;

- capacity that does not change over a wide range of frequencies;

- withstand significant voltage overloads;

- have the best temperature characteristics.

Given the above, in the schemes of stabilized current sources presented above, it is necessary to use ceramic capacitors.

An example of the use of ceramic capacitors for the output capacitor is shown in Fig.9. In this example, the output electrolytic capacitor with a capacity of 1000 μF and a voltage of 160 V in a pulsed source of stabilized current with a frequency of 100 kHz is replaced by twenty-four ceramic capacitors 1206-X5V-25 B-10 μF. To meet stringent requirements for nominal stability, for example, in timing circuits, the use of ceramic capacitors with dielectric X5R and X7R is recommended.

The advantage of using the proposed design of an LED white light source is that the radiation diagram of a crystal (crystal matrix) LED is formed by a segmented reflector in the wavelength range of the crystal (crystal matrix) LED, and not after the phosphor converter converts white radiation in reflectors and optical lenses. This constructive solution for the encapsulation of a crystal (matrix of crystals) LED allows you to increase the luminous flux of a white LED, more than 100%, compared with traditional phosphor diodes, improves the uniformity of the angular distribution of the correlated color temperature (CCT), helps to achieve high chromatic stability in a wide the range of the operating current of the LED, allows you to get a predefined radiation pattern, get a uniform luminous flux, increase the maximum current LED crystal.

Claims (29)

1. LED light source comprising a housing and a reflector, characterized in that the housing is made of heat-scattering material, the inner part of the housing is made in the form of at least one segmented reflector forming a radiation pattern of the light flux containing a layer of reflective material, consisting of at least at least one layer, and a layer of light transmitting dielectric material consisting of at least one layer, at least one crystal of a light emitting diode (LED), replicated inside the case, on top of the case is covered with a converter made of at least one layer of light-transmitting material.
2. The light source according to claim 1, characterized in that at least one side of the converter is embossed.
3. The light source according to claim 1, characterized in that it contains at least one element for dissecting the light flux, which includes a layer of reflective material consisting of at least one layer.
4. The light source according to claim 3, characterized in that at least one element of the dissection of the light flux is integrated into at least one part of the converter or housing.
5. The light source according to claim 1, characterized in that part of the segmented reflector is made in the form of an ellipsoid.
6. The light source according to claim 1, characterized in that part of the segmented reflector is made in the form of a parabola.
7. The light source according to claim 1, characterized in that the segmented reflector has at least one step.
8. The light source according to claim 1, characterized in that the segmented reflector consists of a main and at least one additional reflector.
9. The light source according to claim 1, characterized in that the surface of the segmented reflector has at least one facet.
10. An LED white light source comprising a housing and a reflector, characterized in that the housing is made of heat-scattering material, the inner part of the housing is made in the form of at least one segmented reflector, forming a directional pattern of the distribution of the light flux containing a layer of reflective material, consisting of at least one layer, and a layer of light-transmitting dielectric material, consisting of at least one layer, at least one crystal of a light-emitting diode ( ID) mounted within the housing, the housing top is covered with a converter made from at least one layer of light-transmissive material, wherein on at least one side of the converter applied to the phosphor layer.
11. The light source according to claim 10, characterized in that at least one side of the converter is embossed.
12. The light source according to claim 10, characterized in that it contains at least one element for dissecting the light flux, which includes a layer of reflective material consisting of at least one layer.
13. The light source according to claim 12, characterized in that at least one element of the dissection of the light flux is integrated into at least one part of the converter or housing.
14. The light source according to claim 10, characterized in that the phosphor is included inside the light-transmitting material of the base of the converter.
15. The light source according to claim 10, characterized in that part of the segmented reflector is made in the form of an ellipsoid.
16. The light source according to claim 10, characterized in that part of the segmented reflector is made in the form of a parabola.
17. The light source according to claim 10, characterized in that the segmented reflector has at least one step.
18. The light source according to claim 10, characterized in that the segmented reflector consists of a main and at least one additional reflector.
19. The light source according to claim 10, characterized in that the surface of the segmented reflector has at least one facet.
20. An LED white light source comprising a housing and a reflector, characterized in that the housing is made of heat-scattering material, the inner part of the housing is made in the form of at least one segmented reflector, forming a radiation pattern of the light flux containing a layer of reflective material, consisting of at least one layer, and a layer of light-transmitting dielectric material, consisting of at least one layer, at least one crystal of a light-emitting diode ( ID), mounted inside the housing, on top of the housing is covered with a converter made of at least one layer of light-transmitting material, with a layer of a point phosphor deposited on the side of the converter directed to at least one LED crystal, and the side of the converter directed towards at least one LED crystal is coated with a layer of reflective material consisting of at least one layer.
21. The light source according to claim 20, characterized in that at least one side of the converter is embossed.
22. The light source according to claim 20, characterized in that it contains at least one element for dissecting the light flux, which includes a layer of reflective material consisting of at least one layer.
23. The light source according to p. 22, characterized in that at least one element of the dissection of the light flux is integrated into at least one part of the converter or housing.
24. The light source according to claim 20, characterized in that the phosphor is included inside the light-transmitting material of the base of the converter.
25. The light source according to claim 20, characterized in that part of the segmented reflector is made in the form of an ellipsoid.
26. The light source according to claim 20, characterized in that part of the segmented reflector is made in the form of a parabola.
27. The light source according to claim 20, characterized in that the segmented reflector has at least one step.
28. The light source according to claim 20, characterized in that the segmented reflector consists of a main and at least one additional reflector.
29. The light source according to claim 20, characterized in that the surface of the segmented reflector has at least one facet.
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