RU230857U1 - HEAT DISSIPATION PLATFORM FOR LED LIGHT - Google Patents

Abstract

The utility model relates to the field of lighting devices. The heat-dissipating platform for a LED lamp is a housing made of a material with high thermal conductivity, which is a radiator for heat dissipation into the environment and is used to secure at least one LED module on one side of the housing, and a power supply unit on the other. The housing of the heat-dissipating platform for the LED lamp is made using one metalworking method (cold stamping/laser cutting/sheet metal bending/milling of metal/rolled sheet casting, etc.). The housing is made in the form of a thin-walled plate with a platform of a different shape in plan, from which, on two opposite sides, the edge parts are bent along the length of the platform to one side to form side walls, inclined in opposite directions and in the body of which, opposite the areas where the LED modules are placed, slots are made, the end sections of which from the side of the platform are made in this platform. The slots opposite one section of the LED module placement are made inclined in the direction opposite to the inclination of the slots made in the adjacent section of the other LED module placement. The platform has bulges (blind holes) for fastening and fixing the LED modules. 6 fig.

Description

The utility model relates to the field of lighting devices and concerns the design of a heat-dissipating element of a LED lamp intended for lighting highways, streets, road infrastructure, residential areas, industrial and park areas, etc.

Along with the undeniable conveniences, LED lamps have a number of significant limitations associated with the high heat output of LED modules, which significantly limit the power or dimensions of the product and have a significant impact on the pricing of the final product.

During operation, LEDs require strict adherence to temperature conditions. This requirement is due to the fact that when heated, the efficiency and service life of LEDs are significantly reduced. The main reason for the heating of the LED is the heat generated during its operation. Therefore, to organize the correct operating mode, it is necessary to ensure effective heat dissipation. Continuous operation at elevated temperatures significantly accelerates the process of brightness reduction (degradation), which ultimately leads to a reduction in the useful life. For example, experimental data for two identical LEDs at the same current showed that the service life of the LED will differ in different operating conditions: so at an ambient temperature of -40 ° C, the crystal heats up to no more than 25-30 ° C, and the service life of the LED can be more than 100 thousand hours, and at a temperature of + 40 ° C, on the contrary: the crystal will heat up to + 75-90 ° C, accordingly, the estimated service life will decrease to 35,000 hours (a decrease in the brightness of the luminous flux by 30%).

The LED service life directly depends on the crystal heating temperature, the lower it is, the longer the service life. It is usually considered that the critical temperature for an organic silicon crystal is a temperature range of 100-150°C, while the rate of crystal degradation increases significantly with an increase in current strength to the maximum permissible value, as well as with an increase in temperature.

The degradation of the phosphor is determined mainly by temperature: the phosphor is usually applied directly to the crystal, which heats up quite strongly. The maximum non-destructive operating temperature of crystals in the LED, specified by the developers, usually does not exceed 110-150°C. But such heating leads to degradation of the phosphor and, as a consequence, a change in the color of the LED glow from pure white to violet or green.

In this regard, two problems are solved: heat removal from the crystal through the design elements of the LED module itself and heat removal from the operation of the LED lamp as a whole (reducing the heating of the total volume of the lamp housing in which the LED is located). As a rule, heat removal from the internal volume of the housing is solved quite simply by means of holes, cracks, radiators on the surface of the housing, etc., and the issue of radiator cooling is not a fully resolved problem.

As an example, we can consider the design of a LED lamp, including a housing with a radiator fixed thereto, elements for fastening an LED matrix, protective glass and a holder with an opening and a mechanism for fastening a tubular support console, the housing of the lamp is made collapsible in the form of a base, in the windows of which at least one LED matrix is mounted in its central part, a radiator is mounted on the base above the windows, longitudinal side walls are fixed on the sides of the base, connected by means of grooves-slots with air flow guides installed above the radiator and with at least two air flow guides of the holder, made in the form of ribs and mounted perpendicular to the longitudinal axis of the lamp, wherein the head part of the housing is made in the form of air flow guides mounted mainly parallel to the longitudinal axis of the lamp, and the holder of the lamp is made of a set of air flow guides, additionally connected to each other by means of at least three plates, the upper of which is connected by means of grooves-slots with at least two guides of the housing (RU 2506492, F21S 13/10, published 02/10/2014).

The disadvantage of this solution is the technological complexity of making a case with a radiator. A case made of heat-conducting material consists of a base on which a radiator of complex geometric shape with many longitudinal thin-walled protrusions in the form of ribs is fixed. The LED components themselves and the power supply for them are mounted in the cavity of such a case. It is traditionally believed that an increase in the number of heat-sink ribs allows increasing heat transfer from the case cavity to the external environment. In reality, this does not completely solve the problem of heat removal. The radiator is a complex element with a base in the form of a thickened part and thin ribs in the form of plates extending from it. Heat is removed due to lateral bends and their increase in number leads to an increase in the volume of heat released into the environment. But in reality, heat from the LED light source is removed to the heat-sink base, and from it - through the heat-conducting material of the radiator plates to their heat exchange surfaces, from where it is dissipated into the air. At the same time, the fins cooled by the air flow or by convection are not a reason to believe that the LEDs are cooled in the same way. In fact, in such lamps there is a three-stage heat transfer process: at the first stage, the heat heats the radiator base, at the second stage, the base heats the fins, at the third stage, the fins give off heat to the environment. That is, such a step-by-step heat transfer process for cooling LED elements and the power supply has shown satisfactory operation in practice for low-power LEDs. With an increase in the power of the LEDs, the convection heat transfer on the fins becomes insufficient for this lamp design.

A LED street light is known, comprising a radiator housing (made from a profile, cast, stamped or assembled from these parts) made of a heat-conducting material, with light module(s) installed therein, closed or unclosed lampshades, each of which has at least one solid-state light source and a current source(s) for powering them, the radiator housing-bracket has cooling slots, a central compartment and two peripheral compartments for accommodating light modules are made in the radiator housing, wherein the central compartment is intended to accommodate the power source(s) and the light module(s) or the light module(s), and a heat-conducting material is used to reduce the thermal resistance between the external structures and the radiator housing of the light (RU 149502, F21S 4/00, published 10.01.2015).

This decision was adopted as a prototype.

The radiator case is characterized by its thick-walled design and has a base plate and side walls bent away from the plate at an angle, ending in thin-walled cooling fins. A power supply is mounted in the cavity of the case between the inclined walls, and the LED elements are located on the back of the base plate and on the inclined surfaces of the side walls.

This design does not provide guaranteed cooling of the LED components and the power supply. This is explained by the fact that the housing itself is a heat sink from the operating components of the lamp. And the fins remove heat from this housing. But the heating of the housing occurs faster than the heat is removed from the fins. In the known solution, all surfaces of the housing, despite their unconventional tray-type shape for lamps, are covered with LED blocks placed on them. In this case, the housing does not remove heat, but only accepts it, heating up to the operating temperature of the LEDs (chips). The inner zone between the inclined side walls (bottom) is occupied by the power supply, which blocks the heat removal from both the side walls and the bottom. When receiving heat, the mass of the housing is heated with a gradient in the direction from the surface of the outer wall into the middle structure of the material. This heating of the housing occurs throughout its entire volume. In the places where the fins adjoin, the heat flow interacts with the fins, heating them and transferring heat to the environment. That is, partial cooling will occur not of the LED components and the power supply, but of the case itself and only in the areas where the ribs adjoin it. This solution also uses a similar cooling principle, which is suitable only for low-power LED light sources. When the power of these sources increases, a thermal mode equal to the overheating mode of the chips will be created inside the case, which significantly reduces the service life of the lamp.

This utility model is aimed at achieving a technical result consisting in increasing the operational reliability of a LED lamp by improving heat dissipation due to a change in the shape of the heat-dissipating element of this lamp.

The specified technical result is achieved in that in the heat-dissipating platform for the LED lamp, which is a housing made by a metalworking method (including cold stamping or laser cutting or flexible sheet metal or milling of metal or casting of rolled sheet, etc.), made of a material with high thermal conductivity, which is a radiator for removing heat into the environment and is used to secure at least one LED module on one side of the housing, and a power supply unit on the other, the housing is made in the form of a thin-walled plate with a platform, from which, along two opposite sides, edge parts are bent along the length of the platform to one side to form side walls, inclined in opposite directions and in the body of which, opposite to the areas where the LED modules are placed, slots are made, the end sections of which from the side of the platform are made in this platform, wherein the slots opposite one area where the LED module is placed are made inclined in the direction opposite to the inclination of the slots made in the adjacent area where another LED module is placed. And through holes can be made in the area between the areas where the LED modules are placed.

The side walls, in the preferred embodiment, are bent away from the base plate at an angle of at least 90 degrees.

The specified features are essential and are interconnected with the formation of a stable set of essential features sufficient to obtain the required technical result.

This utility model is illustrated by a specific example of implementation, which, however, is not the only possible one, but clearly demonstrates the possibility of achieving the required technical result.

Fig. 1 - view of the platform from above;

Fig. 2 - side view of the platform;

Fig. 3 - sectional view of the platform from the end;

Fig. 4 - view of the platform with LED modules and optics fixed to it;

Fig. 5 - end view of the assembled lamp, view of the assembled lamp.

Fig. 6 - demonstrates the ascending heat flows removed from the platform and released into the environment.

This utility model examines the design of a platform that is a housing for an LED lamp and provides, due to its design, improved heat dissipation, allowing, while maintaining the dimensions and weight, to use more powerful and efficient LED modules that provide a greater luminous flux and a smaller heat dissipation area, including at elevated ambient temperatures.

The improved heat dissipation system helps to increase the service life of the equipment, due to the precisely calculated air flow formed due to convective heat exchange between the radiator and the environment, which provides the necessary cooling of the LED module and power supply.

In the general case (Fig. 1-3), as a basic element the luminaire contains a platform 1 (housing) made of a material with high thermal conductivity, which is also a radiator for heat removal into the environment. On platform 1, on one side, at least one LED module 2 is fixed (Fig. 4 and 5), the board of which is pressed with the back side to the platform for heat transfer to this platform and into the environment from the side of the LED optics. Heat removal from the LED modules occurs due to heat transfer from the LED module to the platform and heat removal from it by convection.

In the claimed utility model, the main unit of the LED lamp is platform 1 (Fig. 1-3), which functions as a radiator.

The platform is made in the form of a thin-walled plate with a platform 3 of a rectangular or other shape in plan, from which, along two opposite sides, the edge parts are bent along the length of the platform to one side to form side walls 4, inclined in opposite directions (at an obtuse angle, preferably at an angle of 105° - established experimentally) and in the body of which slots 5 are made, the end sections 6 of which from the side of the platform are made in this platform. The shape and dimensions of the holes are selected in the process of calculating the product for heat transfer and are not essential for the object under consideration within the framework of this application.

The presence of these slots is essential, allowing for additional air flow to improve radiator cooling.

The plate is made of the same thickness within the tolerances according to the regulatory documentation. The thin-walled platform means that the plate thickness is significantly less than its other dimensions. In particular, in the real sample, the plate thickness for two LED modules is made approximately 3 mm with a platform length of 426 mm and a total platform width of 166 mm (height of the inclined walls is 44 mm). With an increase in the number of LED modules, the overall dimensions of the platform increase.

In this case, the slots 5 opposite one section of the placement of the LED module are made inclined in the direction opposite to the inclination of the slots made in the adjacent section of the placement of another LED module.

In the convection heat transfer mode, heat flows are directed along the heat exchange surface (into the cold layer zone). In this case, it becomes important that the beam (conditional expression, introduced to understand the essence of the process) of the upward flow from one point on the platform does not intersect and does not add up with the same beam of flow coming from a lower point on the platform. When a single flow of heat rays is formed, heat transfer decreases and the process of cooling the platform in this zone decreases. To eliminate the phenomenon of overlapping heat rays (jets), an oblique direction of the slots is provided, that is, at an angle to the surface of the platform.

In the area between the LED module placement sections 7, through holes 8 are made, arranged in a line running transversely to the area and located between the LED modules. This is necessary for additional air flow and improved heat transfer.

Such a plate has good indicators in terms of resistance to bending and twisting, since the side walls, spread apart at an angle greater than a right angle, are stiffening ribs, on the walls of which the vector of forces leading to deformations does not coincide with the vector of forces deforming the platform. This explains the fairly high bearing capacity of the platform and its resistance to changes in shape.

The implementation of slots 5 in the side walls with their continuation in the body of the platform allows to increase the heat transfer area and improve the conditions of air flow around the environment, which accelerates the plate cooling process not only on the side walls, but also on the platform. In this case, the distance between the end sections of the slots on the platform is made larger than the transverse size of the LED module. Fig. 6 shows the distribution of the heat flow emanating from the plate. It is evident that the heat sink, convectively moving upwards, is significantly larger than the heat release zone on the side of the LED modules. This indicates high efficiency of heat removal. Additional holes can be made on the surface of the platform to accelerate the plate cooling process. The holes located on the surface of the product are located at an optimal distance from each other and in the required quantity, which allows the heat sink technology to work correctly.

This design allows to reduce the overall weight of the product, increasing the amount of heat removed from the light sources, which in turn allows to create more powerful LED lamps in this housing, without deterioration in quality and loss of efficiency.

The presented platform design in the form of a thin-walled plate allows eliminating the overheating zone. In a thin-walled plate, when heated, the entire structure of the material receives the same temperature and heat transfer occurs to a similar degree uniformly over the entire area of the platform. In fact, the entire platform is a surface with high thermal conductivity and uniform heat transfer. At the same time, this surface is well washed by the air of the environment from all sides and therefore cools down quickly. The plate has a single-stage heat transfer.

According to the design, the case refers to metal-hybrid thermal interfaces that use a new heat transfer mechanism. Directly contacting the surface of the heat source, such a case directly dissipates heat. Since the thermal conductivity of aluminum is on average 100 times higher than that of thermal pastes, it is the heat transfer by the metal frame that becomes the dominant mechanism of its transfer ("Metal-hybrid thermal interfaces with high thermal conductivity" V.S. Kondratenko, Yu.I. Sakunenko, A.A. Vysokanov, Applied Physics Journal, 2017, No. 1, pp. 85-88). It has been proven that with this design, the plates do not have middle layers in the structure with a temperature different from the heating temperature of the surface layers. Both developed surfaces of the plate are both heat receivers and heat transferrs to the environment. But at the same time, the cooling time in terms of the rate of temperature decrease exceeds the rate of heating growth, which is confirmed by research in the field of heat removal from boards with LEDs due to the use of thin-sheet metal elements (article "Local heat removal based on metallized through holes" by N.P. Poruchikov, All-Russian scientific and technical conference of students "Student Scientific Spring 2016", posted on the Internet at: http://studvesna.ru). According to the data obtained, as stated in this article, with an increase in the area of the heat-dissipating surface of the thin-sheet element, the time of its cooling to the desired temperature decreases.

In order to maintain the tightness of individual elements of the LED lamp, the metal forming technology is also used in the design of the housing of the heat-dissipating platform for the LED lamp. Sheet metal forming is a process in which individual sections of the rolled sheet are formed, forming a blind hole on one side, and a convex shape on the other, on the surface of the product. The bulges 9 formed on the housing of the heat-dissipating platform after sheet metal forming - blind holes - become additional attachment points (mounting elements) on which the LED module is mounted. The resulting shape ensures a reliable connection of the LED modules with the platform to maintain the tightness of the steel/rolled sheet, thanks to the blind holes formed.

The conducted research and tests have shown a real possibility to increase the removal (output) of thermal energy from the operation of LED modules by changing the layout, shape and design of the radiator housing, which made it possible to use more powerful LEDs and increase the service life of the LED lamp.

Table No. 1. Comparison of the characteristics of a medium-power luminaire by utility model with the closest medium-power analogue by power

(DVO outdoor DKU-120 W).

Characteristic DVO-street DKU-120 W Lamp by utility model Power, W 120 110 IP protection rating IP65 IP67 Luminous flux, Lm 11000 15400 Width, mm 546 426 Depth, mm 170 166 Height, mm 67 88 Weight, kg 2,2 3 Warranty period 2 years 7 years

Comparative table No. 1 clearly shows the advantage of the new heat dissipation scheme in combination with the design, which really allows the use of more powerful power sources and LED modules with smaller dimensions of the lamp, which in turn increases its efficiency.

Table No. 2. Comparison of the characteristics of the luminaire by utility model with the closest high-power analogue

("PRO MODULE" SVT-STR-MPRO-79W-45X140-DUO-C)

Characteristic "MODULE PRO" SVT-STR-MPRO-79W-45X140-DUO-C Utility model lamp (4 LED modules) Utility model lamp (6 LED modules) Power, W 158 160 240 IP protection rating IP67 IP67 IP67 Luminous flux, Lm 26544 28000 36000 Width, mm 636 426 639 Depth, mm 256 250 250 Height, mm 90 88 88 Weight, kg 6.5 3.9 5 Warranty period 5 years 7 years 7 years

Comparative table No. 2 clearly shows that the new solution of the lamp with an improved heat dissipation system really allows the use of powerful power sources and LED modules with smaller dimensions, less weight and a longer warranty period, which increases the benefit and quality of the lamp for the end user for the entire period of operation.

Claims (10)

1. A heat-dissipating platform for a LED lamp, which is a housing made of a material with high thermal conductivity, which is a radiator for dissipating heat into the environment and is designed with the possibility of securing LED modules on one side and a power supply unit on the other side, characterized in that the housing is made by a metalworking method in the form of a thin-walled plate with a platform, from which, on two opposite sides, edge parts are bent along the length of the platform to one side to form side walls inclined in opposite directions, and in the body of which there are slots designed with the possibility of placing them opposite the areas where the LED modules are placed, the end sections of which on the side of the platform are made in this platform, wherein the slots in one section are made inclined in the direction opposite to the inclination of the slots made in the adjacent section, and between the sections through slots are made, arranged in a line passing transversely to the platform and located between the sections. 2. The platform according to item 1, characterized in that the body is made by cold stamping. 3. The platform according to item 1, characterized in that the body is made using a laser cutting method. 4. The platform according to item 1, characterized in that the body is made by bending sheet metal. 5. The platform according to item 1, characterized in that the body is made using a metal milling method. 6. The platform according to item 1, characterized in that the body is made using a rolled sheet method. 7. The platform according to item 1, characterized in that the platform is made of aluminum. 8. The platform according to item 1, characterized in that the platform is made of an aluminum-containing alloy. 9. The platform according to item 1, characterized in that the platform has blind holes designed to allow for fastening and securing LED modules. 10. The platform according to item 1, characterized in that each side wall is bent from the base plate by at least 90 degrees.