LED street light design is not as simple as home lighting source, because the LED street light is used in a harsh environment. It needs to be able to withstand strong winds and early/late huge temperature differences. It also has high luminous flux requirements for the illumination performance of components. Only the lighting system itself needs to meet the design requirements. The matching drive circuit, lamp housing, heat dissipation design, etc. must be matched to meet the final product audit requirements, in order to achieve high reliability and long service life. The rapid development of LED light-emitting components has greatly improved the brightness of the unit components. The existing LEDs have made breakthroughs in the die and packaging technology. The single component has high luminous efficiency, long life and smaller size, and digital drive loop control. It can meet the demand for dimming applications like traditional lamps, highlighting its great growth potential in the lighting application market, and the ban on the ban on the sale of incandescent bulbs based on environmental requirements, which is equivalent to the replacement of LEDs with bulbs. The best publicity, using LED high-efficiency lighting sources to replace traditional low-efficiency lighting sources is just around the corner. However, the quality of LED lighting products in the market is mixed, the performance of some low-priced products is not good, or the reliability and long-life performance of LEDs are neglected, which affects user confidence. For poor optical design, LED lighting status is also caused. Not as comfortable as traditional light sources. The same street lighting LED street lights are also in the same situation. The road lighting facilities are the lighting facilities that the user will touch every day. If the color rendering variation or the brightness is obviously insufficient, the user will doubt the practicality of the LED public lighting. . Changing the LED light source for streetlights can greatly save energy loss. Generally, in LED lighting applications such as roads or tunnels, the LED light efficiency of street lamps is defined at 85 lumens per watt per watt or higher. If the function is constructed with existing technology, It will be able to find street lamps and public lighting facilities made of LED light source technology, and its energy consumption will be much lower than that of high-brightness traditional light source lamps such as incandescent lamps, xenon lamps and halogen lamps, although the energy consumption is greatly won, but In fact, the LED light source is used as a street light, and still suffers from reliability and light decay rate (lifetime). First, let's understand how the reliability of LEDs is defined. Generally speaking, reliability refers to the ability of products to perform their target functions under unit time and conditions. Observing the causes of LED light source lamps is mainly divided into several states, one is serious. Damage failure, which represents the serious damage of the LED light source system, and the other is the occurrence of the light source parameters of the LED light source, affecting its operating efficiency, that is, the luminous flux performance of the LED under normal conditions, if it appears below the initial system Below 70, it is a parametric fault. Whether it is a parametric type or a serious fault phenomenon, it means that the LED light source street light is no longer suitable for lighting tasks and must be repaired or replaced. The low reliability will increase the maintenance and repair costs. The longevity of LEDs cannot be fully realized. Analysis of LED light source failure causes component quality is the first level and observes the typical fault curve of LED light source streetlights. It can be divided into several types, one of which occurs early in the initial operation of the product, and may be caused by random component failures. Excessive runtime will also gradually lead to wear and tear. Most of the initial failures are caused by LED components or defects in the process of using components, or poor soldering of the components and the electronic substrate. There are quite a few reasons for this. It can be static or overload current, or The mechanical stress during the material causes structural damage of the components, and such problems can be found and corrected when the product is operated for 5 to 10 hours after the machine is on the machine. As for the material loss type fault caused by the use of the extended time, although it is a process that the material must pass, it is also traceable. The parameters for observing the attenuation of the LED light output can be evaluated by parameters such as luminous flux and color coordinates. Luminous flux is the output of light. LEDs can generally last for 50,000 hours of operation, but the luminous flux performance will decay with the use of time. When the LED luminous flux decays to the indicated value of 70, it is the LED L70. parameter. Because the wear and component aging caused by long-term use is very important for evaluating component performance, when a certain number of LEDs reach the cumulative value of L70 to half of the total number, this time interval is L70/B50, which represents the key to LED service life. Data chart. Users expect high life expectancy of LED light source. EnergyStar's life expectancy for outdoor LED lighting fixtures is defined as 35,000 hours, even though the L70/B50 of LED lighting components can reach 50,000 hours, but because The light-fading performance of the component itself is affected by a large number of factors, such as a closed lamp housing or a poor heat-dissipating operating environment, or even a short-circuit drive circuit, which may cause the LED light-emitting element to enter the light-emitting period earlier. Affect its durability. With the existing LED lamp manufacturing process, there are quite a lot of ways to improve the overall life of the lamp. For example, in the LED packaging, the LED package can be said to be the key to the reliability of the left and right, and the high-power chip package is matched with high heat resistance. The ceramic substrate with low surface variation is packaged, which not only achieves excellent performance in heat dissipation, but also is a packaging technology that is relatively stable in thermal conductivity and related parameters. In addition, the package size is also gradually reduced. At present, the package size of LED components driven by 10 to 13W can be as small as 3mm*3mm or even smaller. The street lamp/tunnel environment is poorly tested. The lamp housing is waterproof, dustproof and heat-dissipating. However, the actual situation and situation is that the LED street lamp is set up outdoors or in a tunnel. The lamp will be deeply eroded by automobile exhaust and acid rain, and the corrosive gas will be The drive circuit is faulty. In the packaging process of the LED, the silver plating material is used for reflective use, but in fact, the silver material tends to react with the acidic and corrosive gases to become black, so that it directly affects The luminous flux performance of LED light source street lamps, the original silver plating treatment should be changed to a corrosion-resistant design to improve the light flux output caused by corrosion and blackening of materials. In addition to the improvement of the LED component itself, the design of the lamp housing is also the key to the overall product design, because the strong performance of the product depends on the waterproof, dustproof and heat dissipation effects of the lamp housing. The general street lamp will adopt two-piece or three-piece. It is made up of a small number of components and fasteners to enhance the strength of the overall luminaire. Water-proof rubber is also used around the inlaid lampshade glass to avoid rainwater intrusion, and important wire and cable joints are also treated with rubber waterproofing. The lamp housing basically needs to be responsible for the self-heat dissipation requirement. Generally, the LED light-emitting module and the metal lamp housing are laminated to each other, so that the heat source of the LED can be dissipated to the outside of the lamp shell through the metal heat conduction property, and part of the design An active cooling system can also be added to assist the fixture in heat dissipation. Component aging and dust intrusion are also the main faults of LED lamps. Therefore, in addition to air and humidity, component aging and dust problems must also be considered in product design. Basically, as long as high reliability LED light-emitting components are used, It can solve more than half of the product failure problems, followed by how to improve the dust intrusion into the lamp housing and the lighting device is short-circuited due to the wetness of the lamp housing. With better LED components and high-reliability lighting system integration, LED lighting streetlight facilities can naturally achieve better reliability and service life. On the other hand, the LED light source street light is not as bright as possible, but the product design should be carried out in the most economical and most effective way. Generally speaking, about 20 meters in the double lane of about 8 meters wide. A street lamp is set in the meter. The night lighting requirement of the street lamp only needs 10lx, which is enough. The design of the light source over 10lx is basically a waste of energy. With this demand, the corresponding LED light source needs are designed. You can master the required light source driving power, LED type and quantity, and the drive circuit and protection circuit, lamp housing design can also make corresponding development choices, naturally you can find the corresponding optimized product configuration from the requirements, and Not to develop high-efficiency, high-brightness, high-life products, resulting in high product costs, can not cut into the application market.
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