Abbreviation of English words, main meaning: LED = light emitting diode, which is a solid semiconductor device that can convert electric energy into visible light, and can directly convert electricity into light; LED = large electronic display screen, large electronic display screen; LED = disseminated lupus erythematosus, disseminated lupus erythematosus, a chronic and idiopathic autoimmune disease; Led is the past tense and past participle of lead, meaning "lead, lead"; IATA code of Pulkovo airport in Russia. This entry mainly introduces light emitting diodes. Directory [hidden] Basic information LED application Advantages 1, small size 2, low power consumption 3, long life 4, high brightness, low heat generation 5, environmental protection 6, durable lighting terminology LED lighting principle LED dimming control operation parameters and efficiency LED pull-up resistance LED display control system Basic information LED classification Advantages 1, small size 2, low power consumption 3, long life 4, high brightness Working parameters and efficiency of dimming control of LED pull-up resistor LED display control system LED classification [Edit this paragraph] Basic information LED (light emitting diode) is a solid-state semiconductor device, which can directly convert electric energy into light. The core of LED is semiconductor chip. One end of the chip is attached to the Sanfeng LED on the bracket, one end is the negative electrode, and the other end is connected with 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 [1] semiconductor, in which holes are dominant, and the other is an n-type semiconductor, in which electrons mainly exist. 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 determines the color of light, and the color of light is determined by the band gap width of the material that constitutes the pn junction. The 2.5-meter-wide resistance plate has been successfully installed and debugged by Cheng Zheng enterprises! Greatly improve the lighting effect [edit this paragraph] In view of the advantages of LED, it is mainly used in the following aspects: (1) display screen and traffic signal display light source application. LED lamps have the characteristics of earthquake resistance, quick light response, power saving and long service life, and are widely used in various indoor and outdoor display screens, which are divided into full color, three color and monochrome display screens, and there are 10 in China. Traffic lights mainly use ultra-high brightness red, green and yellow LEDs. Because of the energy-saving and high reliability of LED lights, traffic lights are being upgraded step by step all over the country, which is a good market opportunity with fast promotion speed and great market demand. (2) Application in automobile industry Automobile lamps include dashboard, audio indicator, switch backlight, reading lamp, external brake lamp, taillight, side lamp, headlight, etc. Incandescent lamps for automobiles are not resistant to impact and impact, easy to be damaged, short in life and need to be replaced frequently. 1987, China began to install high-position brake lights on cars. Due to the fast response speed of LED, drivers can be reminded to brake as soon as possible to reduce rear-end collision accidents. In developed countries, the central rear high-position brake light made of LED has become the standard of automobiles. The LED taillight module introduced by Hewlett-Packard Company in the United States in 1996 can be combined into various taillights at will. In addition, the light source in lighting components such as automobile dashboard can be used as ultra-high brightness light, so LED display screen is gradually adopted. China automobile industry is in a period of great development, which is an excellent opportunity to promote ultra-high brightness LED. In recent years, the annual output value 1 100 million yuan will be 3 billion yuan after five years. (3) The LED backlight with high efficiency side emission is the most eye-catching. As the backlight of LCD, LED has the characteristics of long life, high luminous efficiency, no interference and high cost performance, and has been widely used in electronic watches, mobile phones, BP machines, electronic calculators, credit card machines and so on. With the miniaturization of portable electronic products, LED backlight has more advantages, so the backlight manufacturing technology will develop towards thinner, lower power consumption and uniformity. LED is the key device of mobile phone. An ordinary mobile phone or PHS needs about 10 LED devices, while a color screen and a mobile phone with camera function need about 20 LED devices. At present, the backlight of mobile phones is very large, and 3.5 billion LED chips are used every year. At present, the output of mobile phones in China is very large, and most of the LED backlights are imported, which is an excellent market opportunity for domestic LED products. (4) (4) The early products of LED lighting source have low luminous efficiency, and the light intensity can only reach several tens of MCD, which is suitable for indoor occasions, household appliances, instruments and meters, communication equipment, microcomputers, toys, etc. At present, the direct goal is to replace incandescent lamps and fluorescent lamps with LED light sources, and this substitution trend has begun to develop from local application fields. In order to save energy, Japan is planning a light-emitting diode project (called "Lighting Japan") to replace incandescent lamps. The budget for the first five years is 5 billion yen. If LED is used to replace half of incandescent lamps and fluorescent lamps, the energy equivalent to 6 billion liters of crude oil can be saved every year, which is equivalent to the power generation of five 1.35 × 106kW nuclear power plants, and the generation of greenhouse gases such as carbon dioxide can be reduced, thus improving people's living environment. China also invested 5 billion yuan in 2004 to develop energy-saving and environmental-friendly semiconductor lighting plan [4]. (5) For other applications, such as a kind of flashing shoes popular with children, the built-in LED will flash when walking, and 500 million LEDs are used in Wenzhou alone; Using light-emitting diodes as the power index of electric toothbrushes, according to domestic manufacturers who are putting into production, the company has listed a small number of healthy toothbrushes, and it is estimated that 300 million light-emitting lamps will be needed every year for mass production; The popular LED Christmas lights are novel in shape, colorful, unbreakable and safe to use at low voltage. Recently, they have sold strongly in Southeast Asia, such as Hong Kong, and are widely welcomed by people, threatening and replacing the existing light bulb Christmas market. [Edit this paragraph] Advantages of LED The inherent characteristics of LED determine that it is the most ideal light source to replace the traditional light source, and it is widely used. First, small LEDs are basically very small chips encapsulated with epoxy resin, so they are very small and light. Second, low power consumption. The power consumption of LED is very low. Generally speaking, the working voltage of LED is 2-3.6V. The working current is 0.02-0.03A, that is, its power consumption does not exceed 0.1w. Third, the service life is long. With proper current and voltage, the service life of LED can reach 65,438+million hours. Four, high brightness, low heat LED adopts cold light technology, the calorific value is much lower than that of ordinary lighting. Five, environmental protection LED is made of non-toxic materials, unlike fluorescent lamps containing mercury, which will cause pollution, and LED can also be recycled. 6. 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. LED lamps are highly energy-saving: energy-saving and pollution-free means environmental protection. DC drive, ultra-low power consumption (single tube 0.03-0.06W), electro-optical power conversion close to 100%, the same light efficiency is more than 80% less than that of traditional light source. Longevity: LED light source is called longevity lamp, which means a lamp that never goes out. The solid-state cold light source is encapsulated by epoxy resin, and the lamp body has no loose parts, and there are no shortcomings such as easy burning, thermal deposition and light decay of the filament. The service life can reach 60,000-65,438+10,000 hours, which is more than 10 times longer than the traditional light source. Variety: LED light source can make use of the principle of three primary colors of red, green and blue to make the three colors have 256 shades of gray. Under the control of computer technology, it can produce 256× 256× 256 =16777216 colors, forming a combination of different light colors, and realizing colorful dynamic change effects and various images. Environmental protection: environmental protection benefits are better. There are no ultraviolet rays and infrared rays in the spectrum, neither heating nor radiation, and the glare is small. In addition, waste can be recycled without pollution and mercury. It is a cold light source and can be safely touched. It belongs to a typical green lighting source. High-tech: Compared with the monotonous luminous effect of traditional light source, LED light source is a low-voltage microelectronic product, which successfully combines computer technology, network communication technology, image processing technology and embedded control technology, so it is also a digital information product and a "high-tech" technology of semiconductor photoelectric devices, with the characteristics of online programming, unlimited upgrade and flexibility. [Edit this paragraph] Lighting term wavelength: The color intensity of light can be described by data, which is called wavelength. The wavelength of visible light ranges from 380 to 780 nanometers. Unit: nanometer (nm) brightness: brightness refers to the brightness of an object and is defined as the luminous intensity per unit area. Unit: nit light intensity: refers to the brightness of the light source. That is, it represents the physical quantity of visible light radiation intensity emitted by a light source in a certain direction and range. Unit: candlelight (cd) luminous flux: the sum of the energy emitted by the light source and the energy received by human eyes is luminous flux (φ). Unit: Lumens (Lm) Light Efficiency: The luminous flux emitted by the light source divided by the power of the light source. It is an important index to measure the energy saving of light source. Unit: lumens per watt (Lm/w). Color rendering: the degree to which a light source presents an object, that is, the fidelity of color. Usually called "color rendering index". Unit: Ra. Color temperature: at a certain temperature, the color of the light emitted by the light source is the same as that radiated by the blackbody, and the temperature of the blackbody is called the color temperature of the light source. Unit: Kelvin (K). Glare: the visual discomfort caused by objects with extremely high brightness or strong brightness contrast in the field of vision is called glare, which is an important factor affecting the lighting quality. Synchronization: Two or more LED lamps can work normally in a programmed synchronization mode within a specified time, and synchronization is the basic requirement for LED lamps to achieve coordinated changes. Protection grade: IP protection grade is classified according to the dust-proof and moisture-proof characteristics of lamps and consists of two numbers. The first number represents the level of dust prevention and foreign body invasion of lamps (0-6), and the second number represents the sealing degree of lamps against moisture and water invasion (0-8). The higher the number, the higher the protection level. [Edit this paragraph] The development of LED display can be divided into the following stages: The first stage is from 1990 to 1995, mainly monochrome and 16 two-color graphic screens. Used to display text and simple pictures, mainly used in public places such as stations, financial securities, banks and post offices. , as a public information display tool. In the second stage, from 1995 to 1999, dual primary color video screens with 64 and 256 gray levels appeared. The application of video control technology, image processing technology and optical fiber communication technology has pushed LED display screen to a new height. At this time, the large-scale integrated circuit chip for LED display control has also been developed and applied by domestic enterprises. In the third stage, from 1999, a large number of red, pure green and pure blue LED tubes flooded into China. At the same time, domestic enterprises have carried out in-depth research and development work, and the full-color display screens produced by red, green and blue LEDs have been widely used, and a large number of them have entered public places such as stadiums, convention centers and squares, making domestic large screens enter the full-color era. With the rapid development of LED raw material market, 200 1 year surface mount devices came out, mainly used in indoor full-color screens. With its characteristics of high brightness, bright colors and low temperature, the spacing between points can be adjusted at will, which is accepted by demanders at different price points. In just over two years, the product sales exceeded 300 million yuan, and the application market of surface mount full-color LED display screen entered the new century. In order to adapt to the "slimming" plan of the 2008 Olympic Games, Liard developed a surface-mounted two-color display screen, which is widely used in training halls and game timing and scoring systems. In terms of full-color screens in Olympic venues, in order to reduce investment, most full-color screens are detachable, which can be used as live broadcast tools during the Olympic Games and rented after the games, and can also be used as application tools in public places such as performances and national policy announcements to recover costs as soon as possible. As far as the market is concerned, China's entry into WTO and Beijing's successful bid for the Olympic Games have become new opportunities for the development of LED display industry. The domestic LED display market continues to grow. At present, the domestic LED display market share is nearly 95%. The international market capacity of LED display screen is expected to increase by 30% every year. The main manufacturers of LED display panels are concentrated in Japan, North China and other places, and the export share of LED manufacturers can be ignored. According to incomplete statistics, there are at least 150 manufacturers producing full-color screens in the world, among which there are about 30 large companies with complete products. At present, with the active promotion of LED industrialization by China government, the production technology of domestic LED display screen is basically synchronized with the world. Well-known domestic brands include: Yuan Heng Photoelectricity (yaham), skymax-display, aled, liantronics, MejLed, dicolor, Liansen, lhgd, TOP and so on.