[Edit this paragraph] 1. Structure and luminous principle of LED
Fifty years ago, people knew the basic knowledge that semiconductor materials can emit light. Structure diagram of light-emitting diode, the first commercial diode was produced in 1960. The core of LED is a wafer composed of P-type semiconductor and N-type semiconductor. There is a transition layer between P-type semiconductor and N-type semiconductor, which is called pn junction. In the PN junction of some semiconductor materials, when the injected minority carriers recombine with the majority carriers, the excess energy will be released in the form of light, thus directly converting electric energy into light energy. When reverse voltage is applied to PN junction, minority carriers are difficult to inject, so they do not emit light. This kind of diode made by injection electroluminescence principle is called light emitting diode, commonly known as led. When it works in the positive [1] direction (that is, DC voltage is applied at both ends), when the current flows from the anode to the cathode of the LED, the semiconductor crystal emits different colors of light from ultraviolet to infrared, and the intensity of light is related to the current.
[Edit this paragraph] Second, the characteristics of LED light sources
1. voltage: LED uses low-voltage power supply, the power supply voltage is between 6-24V, which varies according to different products, so it is safer than using high-voltage power supply, especially suitable for public places. 2. Efficiency: Compared with incandescent lamps with the same light efficiency, the energy consumption is reduced by 80%. 3. Applicability: very small, each unit LED die is 3-5mm square, so it can be made into devices with various shapes, which is suitable for changing environments. 4. Stability: 65,438+million hours. The light attenuation is 50% of the initial value. 5. Response time: The response time of incandescent lamp is millisecond, and that of LED lamp is nanosecond. 6. Environmental pollution: no harmful metal mercury. 7. Color: You can change the color by changing the current. The LED can easily adjust the energy band structure and band gap of the material through chemical modification, so as to realize multi-color emission of red and yellow LED lamps. For example, when the current is low, the red LED will turn orange, yellow and finally green. 8. Price: LED is more expensive. Compared with incandescent lamps, the price of several incandescent lamps can be equivalent to the price of one LED lamp. Usually, each group of signal lamps needs to be composed of 300 ~ 500 diodes.
[Edit this paragraph] III. Types and development history of monochromatic light emitting diodes
The earliest LED light source based on the principle of semiconductor pn junction was produced in the early 1960s. The material used at that time was GaAsP, which emitted red light (λ p =650nm). When the driving current is 20 mA, the luminous flux is only a few thousandths of lumens, and the corresponding luminous efficiency is about 0. 1 lumen/watt. In the mid-1970s, the introduction of In and N elements led to green light (λ p =555nm), yellow light (λ p =590nm) and orange light (λ p =6 10nm), and the light efficiency was also improved to 1 lumen/watt. In the early 1980s, GaAlAs LED light source appeared, which made the light efficiency of red LED reach 10 lumen/watt. In the early 1990s, two new materials, GaAlInP emitting red and yellow light and GaInN emitting green and blue light, were successfully developed, which greatly improved the light efficiency of LED. In 2000, the light efficiency of the LED manufactured by the former reached 100 lumens/watt in red and orange regions (λ p =6 15nm), while the light efficiency of the LED manufactured by the latter reached 50 lumens/watt in green regions (λ p =530nm).
[Edit this paragraph] 4. Application of monochromatic LED
At first, LED was used as the indicating light source of instruments. Later, LEDs with various colors were widely used in traffic lights and large-area display screens, which produced good economic and social benefits. Take 12 inch red traffic light as an example. In the United States, 140 watt incandescent lamp with long life and low light efficiency was originally used as the light source, and LED line lamp produced 2000 lumens of white light. After passing through the red filter, 90% of the light is lost, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds Company adopted 18 red LED light sources, including circuit loss, * * * consumption 14 watt, which can produce the same light effect. Car signal lamp is also an important field of LED light source application. 1987, China began to install high-position brake lights on cars. Because of the fast response speed of LED (nanosecond level), the driver behind the car can know the driving situation as soon as possible and reduce the occurrence of rear-end collision. In addition, LED lights have been used in outdoor red, green and blue full-color display screens, keychain miniature flashlights and other fields.
[Edit this paragraph] V. Development of White LED
For general lighting, people need a white light source more. 1998 white LED has been successfully developed. This kind of LED is encapsulated by GaN chip and yttrium aluminum garnet (YAG). GaN chip emits blue light (λ p =465nm, Wd=30nm), and the high-temperature sintered YAG phosphor containing Ce3+ emits yellow light after being excited by this blue light, with a peak value of 550nm. The blue LED substrate is installed in the bowl-shaped reflection cavity and covered with a thin layer of YAG-mixed resin, about 200-500nm. Part of the blue light emitted by the LED substrate is absorbed by the phosphor, and the other part of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light. Now, for InGaN/YAG white LED, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, we can get all kinds of white light of 3500-10000 K. In fact, LED lamp is what we usually call energy-saving lamp. (This is wrong, the working principles of energy-saving lamps and LEDs used in daily life are completely different! But there is no problem that LED lights are called energy-saving lamps. ) The prices of LED lamps with different powers are different. Moreover, different processes and different appearance materials will also cause price differences.
[Edit this paragraph] VI. Comparison and competition between new neon lights and LED lights
The following is a comparison between neon lights and LED lights, with the latest LED technology, which is not the information you saw on the Internet before. 1.Is the life of LED light source 100000 hours? According to the calculation of 7% light decay, the actual time is only about 50000 hours. According to the light attenuation of 3%, the practical application can reach 80000 hours. 2. won't the 2.led heat up? Yes, it needs heat dissipation. 3. Can 3.LED replace incandescent lamp? The luminous flux, luminous efficiency and color rendering are all ok, but it is too expensive at present and will not decrease in recent years. But the cost of replacing incandescent lamps can be reduced by increasing the luminous flux of products. 4. Can 4.LED be simply used as a common light source? [2] No, to drive the power supply, optics and heat conduction should cooperate. The advantages of the two light sources compared with neon lights have been covered by LED, but the price of LED lights is too high at present. 6. The power supply of two light sources is better than that of low-voltage LED, but the water resistance is poor and the load current is too large. The input current of large particle 1 watt LED single lamp is 350mA. 7. The control technology of two light sources is easier to realize than LED, but neon lights are mature. 8. Compared with LED, the stability of the two light sources is inconsistent, and the neon lamp is quite stable. A few manufacturers can be relatively stable, such as combining CREE and AOD chips and taking the advantages of their respective chips. 9. Both light sources are more expensive than LEDs, but yellow and red are equivalent, and the main expensive one is LED white light. 10. Comparison of two kinds of outdoor light sources Poor waterproof of LED is the fatal weakness of outdoor use. 1 1. Comparison of two light sources on the market at present. The annual output value of global lighting products is 42 billion US dollars (China1500 million US dollars), and the proportion of LED light sources is less than 1%.
[Edit this paragraph] VII. What is the packaging of led lights?
Description of led lamp packaging: Simply put, led packaging is the process of packaging led packaging materials into led lamps; Led lamp packaging technology: Generally, led packaging has to go through crystal expanding, crystal fixing, welding, glue filling, foot cutting, light splitting, color separation and other processes. Led lamp packaging materials: The main packaging materials of led are: chip, gold wire, bracket, glue, etc. Led lamp packaging equipment: crystal expanding equipment, crystal fixing machine, welding machine, dispensing machine, baking box, etc. , generally divided into automatic packaging equipment and manual packaging equipment.
[Edit this paragraph] VIII. How to judge the quality of led lamp packaging?
Indicators of led lamp quality: Several indicators of led lamp quality include: angle, brightness, color (wavelength) consistency, antistatic ability, attenuation resistance and so on. Packaging materials of led lamps: led packaging materials are the direct and basic factors of led lamps. Led lamp is a combination of several main materials, and a good led lamp must be a combination of all packaging materials and production processes. Led lamp packaging technology: Generally, automatic equipment packaging is better than manual packaging, and the technical level of packaging is also the main factor of led lamp packaging, and the products produced by different manufacturers with the same material are very different;
[Edit this paragraph] 9. What kind of led lights do you need to make an led display?
Appearance of led lights: outdoor led electronic screen mainly adopts direct-entry oval led lights, and indoor led electronic screen mainly adopts surface-mounted led lights. Parameters of led lamp: Brightness varies according to the use environment and other factors. The wavelength of red light is 620 -625 nm, the wavelength of green light is 520 -525 nm, and the wavelength of blue light is 465 -470 nm.
[Edit this paragraph] X. led- Definition
LED (Light Emitting Diode) is a solid-state semiconductor device, which can directly convert electricity into light. The core of LED is semiconductor chip. One end of the LED chip is attached to the bracket, one end is the negative electrode, and the other end is connected to the positive electrode of the power supply, so that the whole chip is encapsulated by epoxy resin. The semiconductor wafer consists of two parts, one is a P-type semiconductor, in which holes are dominant, and the other is an N-type semiconductor, mainly electrons. But when these two semiconductors are connected together, a pn junction is formed between them. When the current acts on the chip through the wire, the electrons will be pushed to the P region, where they will recombine with holes and then release energy in the form of photons, which is the principle of LED light emission. The wavelength of light, that is, the color of light, is determined by the material forming the pn junction. Fifty years ago, people knew the basic knowledge that semiconductor materials can emit light. The first commercial diode was produced in 1960. LED is the abbreviation of English light emitting diode. Its basic structure is a piece of electroluminescent semiconductor material, which is put on the shelf with leads and then sealed with epoxy resin to protect the internal core wire, so the led has good seismic performance. The core of LED is a wafer composed of P-type semiconductor and N-type semiconductor. There is a transition layer between P-type semiconductor and N-type semiconductor, which is called pn junction. In the PN junction of some semiconductor materials, when the injected minority carriers recombine with the majority carriers, the excess energy will be released in the form of light, thus directly converting electric energy into light energy. When reverse voltage is applied to PN junction, minority carriers are difficult to inject, so they do not emit light. This kind of diode made by injection electroluminescence principle is called light emitting diode, commonly known as led. When working in the forward direction (that is, DC voltage is applied at both ends), when the current flows from the anode of the LED to the cathode, the semiconductor crystal emits different colors of light from ultraviolet to infrared, and the intensity of light is related to the current. At first, LED was used as the indicating light source of instruments. Later, LEDs with various colors were widely used in traffic lights and large-area display screens, which produced good economic and social benefits. Take 12 inch red traffic light as an example. In the United States, 140 watt incandescent lamp with long life and low light efficiency was originally used as the light source to generate white light with 2000 lumens. After passing through the red filter, 90% of the light is lost, leaving only 200 lumens of red light. In the newly designed lamps, Lumileds Company adopted 18 red LED light sources, including circuit loss, * * * consumption 14 watt, which can produce the same light effect. Car signal lamp is also an important field of LED light source application. For general lighting, people need a white light source more. 1998 white LED has been successfully developed. This kind of LED is encapsulated by GaN chip and yttrium aluminum garnet (YAG). GaN chip emits blue light (λp=465nm, Wd=30nm), and the high-temperature sintered YAG phosphor containing Ce3+ emits yellow light with a peak of 550nm after being excited by this blue light. The blue LED substrate is installed in the bowl-shaped reflection cavity and covered with a thin layer of YAG-mixed resin, about 200-500nm. Part of the blue light emitted by the LED substrate is absorbed by the phosphor, and the other part of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light. Now, for InGaN/YAG white LED, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, various white lights of 3500- 10000K can be obtained. This method of obtaining white light through blue LED is widely used because of its simple structure, low cost and high technical maturity. In 1960s, scientists and technicians developed LED according to the principle of semiconductor PN junction. The LED developed at that time was made of GaASP material, and its luminous color was red. After nearly 30 years of development, the familiar LED has been able to emit red, orange, yellow, green, blue and other colors of light. However, white LED for lighting has only been developed in recent years. Here, the white LED for lighting is introduced to readers. Led- introduces the relationship between visible light spectrum and led white light. As we all know, the wavelength range of visible light spectrum is 380 nm ~ 760 nm, which is seven colors of light that human eyes can feel-red, orange, yellow, green, cyan, blue and purple, but these seven colors of light are monochromatic. For example, the peak wavelength of red light emitted by LED is 565 nm. There is no white light in the spectrum of visible light, because white light is not monochromatic light, but synthetic light composed of many monochromatic lights, just as sunlight is composed of seven monochromatic lights, and white light in color TV sets is also composed of three primary colors: red, green and blue. Therefore, in order to make LED emit white light, its spectral characteristics should include the whole visible spectral range. However, under the current process conditions, it is impossible to manufacture an LED with this performance. According to people's research on visible light, the white light that people can see needs at least a mixture of two kinds of light, that is, two-wavelength light (blue light+yellow light) or three-wavelength light (blue light+green light+red light). The above two modes of white light need blue light, so taking blue light has become the key technology to make white light, which is the "blue light technology" pursued by major LED manufacturing companies. At present, there are only a handful of manufacturers who have mastered the "blue light technology" in the world, so there is still a process for the promotion and application of white LEDs, especially the promotion of high-brightness white LEDs in China. 2. Technical structure of white LED and white light source. For general lighting, from the process structure, white LED is usually formed by two methods. The first method is to use "blue light technology" and phosphor to form white light; The second is a variety of monochromatic light mixing methods. These two methods have successfully manufactured white light devices. The system for generating white light by the first method is shown in figure 1. In the picture, the LED GaM chip emits blue light (λ p = 465 nm) and is encapsulated with YAG (yttrium aluminum garnet) phosphor. When the phosphor is excited by blue light, it emits yellow light. As a result, blue light and yellow light are mixed to form white light (the structure of LED is shown in Figure 2). The second method is to package chips with different colors of light and produce white light by mixing the colors of light. 3. The application prospect of white LED lighting new light source. In order to illustrate the characteristics of white LED, let's take a look at the current situation of lighting source. Incandescent lamps and tungsten halogen lamps have luminous efficiency of 12 ~ 24 lumens/watt; The luminous efficiency of fluorescent lamps and HID lamps is 50 ~ 120 lumens/watt. White LED: 1998, the light efficiency of white LED is only 5 lumens/watt, 1999, reaching 15 lumens/watt, which is similar to ordinary household incandescent lamps. In 2000, the luminous efficiency of white LED reached 25 lumens/watt, which was similar to that of halogen tungsten lamp. Some companies predict that by 2005, the light efficiency of LED will reach 50 lumens/watt, and by 20 15 years, the light efficiency of LED is expected to reach 150 ~ 200 lumens/watt. At that time, the working current of white LED can reach ampere level. It can be seen that the development of white LED lighting source for writers will become a possible reality. Although incandescent lamps and tungsten halogen lamps for general lighting are cheap, they have low luminous efficiency (the thermal effect of lamps consumes electricity in vain), short service life and heavy maintenance workload. However, if white LEDs are used as lighting, they not only have high luminous efficiency, but also have a long service life (continuous working time is longer than 10000 hours) and hardly need maintenance. At present, German Hella Company has developed airplane reading lamp by using white LED. A street in Canberra, the capital of Australia, has used white LED as street lighting. China's urban traffic management lights are also replacing the early traffic order indicators with white LEDs. It can be predicted that in the near future, white LED will definitely enter the home to replace the existing lighting. LED light source has the advantages of using low-voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, multi-color luminescence and so on. Although the price is more expensive than the existing lighting equipment, it is still considered that there will be existing lighting equipment. Led- characteristics The characteristics and advantages of Led determine that it is the most ideal light source to replace the traditional light source, and it is widely used. A small LED is basically a small chip encapsulated with epoxy resin, so it is very small and light. Low-power LED consumes very little power. Generally speaking, the working voltage of LED is 2-3.6V. The working current is 0.02-0.03A That is to say, the power consumption does not exceed 0.1w.. Long service life Under proper current and voltage, the service life of LED can reach 65,438+100,000 hours. High-brightness low-heat environmental protection LED is made of non-toxic materials, unlike fluorescent lamps, which will cause pollution, and LED can also be recycled. Durable LEDs are completely encapsulated in epoxy resin, which is stronger than light bulbs and fluorescent tubes. There is no loose part in the lamp body, which makes the LED not easy to be damaged. Color temperature and application of color: (1) Color temperature of light source: People use the absolute temperature of a complete radiator equal to or close to the color temperature of light source to describe the color table of light source (the color seen when human eyes directly observe the light source), also known as the color temperature of light source. Color temperature is expressed as absolute temperature k, and different color temperatures will cause different emotional reactions. We generally divide the color temperature of light sources into three categories: A. Warm color light: the color temperature of warm color light is below 3300K K, which is similar to incandescent lamp and has more red components, giving people a warm, healthy and comfortable feeling. Suitable for families, houses, dormitories, hospitals, hotels and other places, or places with relatively low temperature. B. Warm white light: also called intermediate color, its color temperature is between 3300 K and 5300 K. Warm white light combined with soft light makes people feel happy, comfortable and quiet. Suitable for shops, hospitals, offices, restaurants, restaurants, waiting rooms and other places. C. cool light: also known as daylight color, its color temperature is above 5300K, and the light source is close to natural light, which makes people concentrate. Suitable for offices, conference rooms, classrooms, studios, design rooms, library reading rooms, exhibition windows and other places. Color rendering: the degree to which the light source presents the color of an object is called color rendering, that is, the degree to which the color is realistic. The light source with high color rendering performance is better in color, and the color we see is closer to the natural color. The light source with low color rendering performance is worse for color, and the color difference we see is also greater. Why is there a difference in color development? The key lies in the spectral characteristics of light. The wavelength of visible light is in the range of 380mm to 780mm, that is, the range of red, orange, yellow, green, cyan, blue and purple light we see in the spectrum. If the proportion of all kinds of light contained in the light emitted by the light source is close to natural light, the colors seen by our eyes will be more realistic. We usually use the color rendering index as the representation of color rendering. Under the irradiation of standard light source, the color rendering index of standard color is set to 100. When the color label is illuminated by the test light source, the degree of visual distortion of the color is the color rendering index of the light source. The larger the color rendering index, the smaller the distortion. Conversely, the greater the distortion, the smaller the color rendering index. Different places have different requirements for the color rendering index of light sources. In the International Lighting Association, the color rendering index is generally divided into five categories: Ra, scope of application, 1A >90, art galleries, museums, printing and other industries and places, 2B80-90-90, family, catering, high-end textile processing and similar industries, 2,60-80, office, school, outdoor street lighting, 3.
[Edit this paragraph] XI. Safety requirements of LED lamps
LED has the advantages of energy saving and environmental protection, and its development in the lighting industry has become the main trend. Because the technology and product attributes of LED are very different from those of traditional lamps, the current general lamp safety standards and specifications are obviously not applicable. In order to help the industry face up to this problem, this issue will introduce the technology used by LED lamps, the possible application scope and the safety assessment currently used by UL. The technology and characteristics of led lamp The so-called LED lamp, as its name implies, refers to the lamp products that use LED (Light Emitting Diode) technology as the main light source. LED is a solid semiconductor element, which uses current to flow forward to the junction of semiconductor p-n junction, and then the negatively charged electrons and positively charged hole carriers separated from the semiconductor combine with each other to produce photon emission. Different kinds of light-emitting diodes can emit different wavelengths of light, from infrared light to blue light, from purple light to ultraviolet light. In recent years, the new development is to coat fluorescent powder on blue LED, and convert blue LED into white LED products. This operation generally needs to cooperate with the driving circuit (LED driver) or power supply. The main function of driving circuit or power supply is to convert AC voltage into DC power, and at the same time complete the voltage and current consistent with LED to drive the matching components. LED light bulbs are small in size, light in weight, encapsulated by epoxy resin, can withstand high-strength mechanical shock and vibration, are not easy to break, and have a long brightness decay period, so the service life can be as long as 50,000-100000 hours, far exceeding that of traditional tungsten light bulbs10000 hours and fluorescent lamps10000 hours. Because the service life of LED lamps can reach 5 ~ 10 years, it can not only greatly reduce the replacement cost of lamps, but also drive the lamps with a small current. Under the same lighting effect, the power consumption is only half that of fluorescent tubes, so LEDs also have the advantages of saving electricity and energy. However, there are still some shortcomings in some LED technologies, so the shortcomings of using LED lamps at first are poor light quality (color rendering, consistency and color temperature), difficult heat dissipation, high price, and improper heat dissipation will lead to accelerated attenuation of the brightness of LED lamps and the service life of circuit components. With the rapid development of manufacturing technology in recent ten years, the above shortcomings, including the gradual decrease of thermal resistance of LED, are also improving the light quality. In 2008, the luminous efficiency of LED white light has reached 100 Lm/W and 20 10 years, and the luminous efficiency of LED warm white light is expected to increase from the current 70 Lm/W to100lm/w. Compared with other general light sources at present, the luminous efficiency of LED is obviously more and more advantageous. Tungsten filament bulbs are about 15 Lm/W, fluorescent lamps are about 45~60 Lm/W, and HID lamps are about120 ~150 lm/w. The following are the comparison of the lighting characteristics of LED and other commonly used lamps: Characteristics of lighting methods.
White LED has the advantages of less heat source, wide working environment, miniaturization, anti-vibration and concentrated light beam.
Daylight (fluorescent lamp) fluorescent lamp saves electricity, but the waste is fragile and there are problems such as mercury pollution
Incandescent tungsten filament bulbs have low efficiency, high power consumption, short life and fragility.
The application direction of product selection guide is 1. The external lighting of the building projects a certain area of the building, which is nothing more than using a projection lamp to control the shape of beam angle's round head and square head, which is completely consistent with the traditional concept of projection lamp. However, due to the small and thin LED light source, the research and development of linear projection lamps has undoubtedly become a highlight of LED projection lamps, because many buildings do not have prominent places to place traditional projection lamps. It is easy to install, and can be installed horizontally or vertically, which is better combined with the architectural surface, bringing new lighting vocabulary to lighting designers and expanding the creative space. It will also have an impact on the lighting technology of modern buildings and historical buildings. 2, landscape lighting LED lights renderings Because LEDs are not like traditional lamps, most of the light sources are glass bulbs, which can be well combined with urban street facilities. It can be used for lighting urban leisure spaces, such as paths, stairs, decks, waterfront areas and gardens. For flowers or low shrubs, LED can be used as the lighting source. LED hidden projection lamps will be particularly popular. The fixed end can be designed as plug-in type, which is convenient to adjust according to the plant growth height. 3. For places where signs and indicating lighting are needed to define and guide the space, such as separate display of roads and sidewalks, partial lighting of stair treads, indicating lighting of emergency exits, etc., LED self-luminous buried lamps with appropriate surface brightness or lamps embedded in vertical walls can be used, such as ground guiding lamps in the audience hall of a theater or indicator lamps on the side of seats, guiding lamps on the floors of shopping centers, etc. In addition, compared with neon lights, LED is low-voltage, there is no fragile glass, and the cost will not increase because of bending in production, so it is worth popularizing in logo design. 4. Indoor space display lighting In terms of lighting quality, LED light source has no heat, ultraviolet and infrared radiation, so it will not damage exhibits or commodities. Compared with the traditional light source, the lamp does not need additional filtering devices, and the lighting system is simple, low in cost and easy to install. Its precise light distribution can be used as a substitute for optical fiber lighting in museums. Color LED is used in commercial lighting metropolis, and white LED for interior decoration is combined with interior decoration to provide auxiliary lighting. LED can be used to hide light bands, which is especially beneficial to low space. 5. Entertainment places and stage lighting Because of the dynamic and digital control of LED on color, brightness and dimming, lively and saturated colors can create static and dynamic lighting effects. From white light to full spectrum of any color, the use of LED has opened up a new idea for the lighting of this kind of space. Compared with the service life of PAR lamps and metal halide lamps of 50-250 hours, the maintenance cost and the frequency of changing light sources are reduced. In addition, LED overcomes the phenomenon of color shift after metal halide lamps are used for a period of time. Compared with PAR lamps, there is no thermal radiation, which can make the space more comfortable. At present, the application of LED color decorative walls in catering buildings has become a common practice. 6. Video screen Full-color LED display screen is the most striking outdoor large-scale display device in the world today. It uses advanced digital video processing technology, with unparalleled super-large area and ultra-high brightness. According to different indoor and outdoor environments, different specifications of light-emitting pixels are used to achieve different brightness, color and resolution, and meet various purposes. It can use multimedia technology to dynamically display graphic animation information and play various multimedia files. At present, the most influential LED display screen in the world belongs to the new york Stock Exchange in Times Square, Manhattan, USA, with 65,438+08,677,760 LEDs and an area of 65,438+00,736 square feet. The screen can be divided into multiple screens and displayed at the same time, showing the market of Wall Street stock market to the public at a glance. In addition, Aurora International Headquarters, which has sprung up in Lujiazui Financial Center, Pudong, Shanghai, has an oversized LED screen with a length of 100m, with a total area of 3,600 square meters. This is the first one in the world. 7. The invention is suitable for lighting various lamps of electric cars, motorcycles and automobiles.
[Edit this paragraph] XII. The power supply of LED lamp determines the life of LED lamp.
Constant current source driving is the best LED driving mode. It is driven by a constant current source, and there is no need to connect a current limiting resistor in series in the output circuit. The current flowing through the LED is not affected by the change of external power supply voltage, ambient temperature and LED parameter discreteness, so it can keep the current constant and give full play to various excellent characteristics of the LED. LED constant current power supply is used to supply power to LED lamps. Because the current flowing through the led will be automatically detected and controlled during the operation of the power supply, there is no need to worry about the excessive current flowing through the LED at the moment of power-on, and there is no need to worry about the short circuit of the load and the burning of the power supply.