In order to develop LED street lamps, attention should be paid to the following aspects
Source: http://www.qdjiashang.com/news/3876.html Release time: 2018-10-25
A. The improvement of optical communication needs to be further improved from the basic level of high-power LED epitaxy technology, chip technology and so on. The method of making white LED at home and abroad is to place the LED chip on the encapsulated substrate, bond it with gold wire, then coat the chip with YAG phosphor, and then encapsulate it with epoxy resin. Resin not only protects the chip, but also acts as a condenser. Blue light emitted from the LED chip is scattered and absorbed into the surrounding phosphor layer for many times, and finally emits to the outside. The peak value of the spectrum of LED (blue) is 465 nm, and the half-width is 30 nm. Some blue light emitted by LED excites yellow YAG phosphor layer, which emits yellow light (peak 555 nm). Some blue light emits outward directly or after reflection. Finally, the external light is blue-yellow dichroic light, i.e. white light. Flip Chip (Flip Chip) technology can get more effective lighting than traditional LED chip packaging technology. But if we do not add a reflecting layer under the electrodes of the light emitting layer of the chip to reflect the wasted light energy, it will cause about 8% light loss. Therefore, the reflective layer must be added to the floor material. The light on the side of the chip must also be reflected by the mirror of the heat sink to increase the light output of the device. In addition, a layer of silica gel should be added between the light-conducting interface of Sapphire and epoxy resin to improve the refractive index of the chip. With the improvement of optical packaging technology, the luminous flux of high power LED devices can be greatly increased.
B. LED lighting fixtures are optimized to improve the quality of LED use. Therefore, it is particularly urgent to study the secondary optical distribution design of high-power LED light source to meet the needs of large-area projection and floodlighting lighting. By means of secondary optical design technology, the light extraction efficiency of the device can be improved by designing an additional reflecting cup, multiple optical lenses and aspheric surface. The illumination direction of the traditional light source is 360 degrees, and the lamp reflects most of the light to a specific direction by the reflector. Only about 40% of the light reaches the road surface directly through the glass cover. The other light is projected through the reflector of the lamp. The efficiency of the reflector of the lamp is generally only 50%~60%, so about 60% of the light is transmitted. It is projected on the road after losing 30%~40% of the lamp. A large part of the light output of the light source is limited to the heat consumption inside the lamp. Most of the light of the LED lamp is forward light, which can achieve & gt; 95% of the light efficiency. This is one of the important characteristics of the LED which is different from other light sources. If we can not make good use of this characteristic, the advantages of the LED will be greatly discounted. Most high-power LED lamps are assembled by several LED chips. To illuminate so many light sources in different directions, we give full play to the characteristics of the whole package of the chip and use lenses to solve the problem. Through optical design, according to different needs, we equip different convex curves, relying on lenses to distribute light to different directions, to ensure that The large angle of light output can reach 120 ~160 and the small one can gather the light within 30. Once the lens is fixed, the light distribution characteristics of the same kind of lamps will reach the same level on the premise of ensuring the production process. It is possible to make the LED street lamp meet the requirements of the road lighting standards through trial production and continuous summary of experience. Tunnel lamp, street lamp and general lighting lamp have met the lighting requirements of their respective application sites.
C. Heat dissipation is the key problem to be solved for LED street lamps. As we all know, LED is an optoelectronic device. Only 15%-25% of its energy is converted into light energy, and almost all the other energy is converted into heat energy, which makes the temperature of LED rise. In high-power LED, heat dissipation is a big problem. For example, if the photoelectric conversion efficiency of a 10W white LED is 20%, 8W energy will be converted into heat energy. Without heat dissipation measures, the core temperature of high-power LED will rise rapidly. When its temperature (TJ) rises above the maximum allowable temperature (generally 150 C), the high-power LED will be damaged by overheating. Therefore, in the design of high-power LED lamps, the most important design work is the heat dissipation design. Because of the high brightness requirement of LED street lamp and the harsh use environment, if the heat dissipation is not solved properly, it will quickly lead to the aging of LED and reduce its stability. A street lamp with 250W high pressure sodium lamp, due to mature technology and good heat dissipation control, even if it works 5000 hours, the light decay is still very small. Under the same conditions, if the heat dissipation of high-power LED street lamps is not solved properly, the light decay will be very large. The main ways of heat dissipation of LED street lamp are natural convection heat dissipation, forced fan heat dissipation, heat pipe, loop heat pipe heat dissipation and even temperature plate heat dissipation. The forced cooling system with fan is complex and low reliability, and the cost of heat pipe and uniform temperature plate is high.
D. LED street lamp, will eventually choose modular installation and maintenance. At present, the most commonly used high-pressure sodium lamp on the road surface, the internal ballast and other components are not easy to damage. Most of the reasons for the illumination failure are the damage of the light source. The way of maintenance is to replace the light source. A skilled operator can operate on a high platform by himself. However, there are many parts inside the LED street lamp, besides the light source (chip), the damage of other parts will cause the chip not to turn on. Therefore, in the field, it is impossible to immediately determine the cause of LED street lamp damage. If the LED street lamp is not on, it is necessary to remove the LED street lamp and return it to the factory for various tests. This way of replacing LED street lights seems very cumbersome. The final version of LED street lamp development is to develop into modularization. The light source and electricity are all replaced according to the plug-in, so that a skilled worker can independently judge the cause of the damage and carry out on-site maintenance. Eight hundred and eighty-eight thousand one hundred and eleven