LED electronic display is composed of tens of thousands - hundreds of thousands of semiconductor light-emitting diode pixel points evenly arranged. The use of different materials can be manufactured in different colors of LED pixel points. Currently the most widely used are red, green, yellow. And the development of blue and pure green LED has reached a practical stage.
LED display (LED panel): LED is light emitting diode, light-emitting diode acronym in English, referred to as LED. it is a semiconductor light-emitting diode display by controlling its approximate appearance is made up of a lot of light-emitting diode is usually red, relying on the light of the light to display characters. It is a display screen used to display various information such as text, graphics, images, animations, quotes, videos, and video signals.
LED display (LED panel): also known as electronic display or floating word screen. Is composed of LED dot matrix, through the light of the lamp beads to display text, pictures, animation, video, content can be replaced at any time, each part of the components are modular structure of the display device. Usually consists of display module, control system and power supply system. Display module consists of LED lights composed of dot matrix composition, responsible for the light-emitting display; control system by controlling the corresponding area of the light and dark, you can let the screen display text, pictures, video and other content, constant dance card is mainly to play the animation; power supply system is responsible for the input voltage and current into the display needs the voltage and current.
LED display is divided into graphic display and video display, are composed of LED matrix block. Graphic display can be synchronized with the computer to display Chinese characters, English text and graphics; video display using a micro-computer for control, graphics, images and lush, real-time, synchronized, clear information dissemination to play a variety of information, but also can display two-dimensional, three-dimensional animation, video, television, VCD programs and the scene of the actual situation. LED display screen display screen with vibrant colors, three-dimensional sense of strong, static as oil paintings, moving as a Movie, widely used in stations, docks, airports, shopping malls, hospitals, hotels, banks, securities markets, construction markets, auction houses, industrial enterprise management and other public **** place.
Features of LED electronic display
LED display can display changing numbers, text, graphic images; not only can be used for indoor environment can also be used for outdoor environment, with a projector, TV wall, LCD display can not be compared with the advantages.
The reason why LED has been widely recognized and rapid development, is inseparable from its own advantages. These advantages are summarized as: high brightness, low operating voltage, low power consumption, miniaturization, long life, impact resistance and stable performance.
LED's development prospects are extremely broad, is now moving towards higher brightness, higher weather resistance, higher luminous density, higher luminous uniformity, reliability, full-color direction.
LED display superior performance: strong luminous brightness in the visible distance from the direct sunlight on the screen surface, the display content is clearly visible.
1, according to the color base color can be divided into
Single-color display: a single color (red or green).
Dual-color display: red and green dual-color, 256 levels of gray scale, can display 65536 (256 * 256) kinds of colors.
Full-color display: red, green, blue three-color, 256-level grayscale full-color display can show more than 16 million colors. 1.1, dual-color
Most of today's color LED display is a dual-color color screen, that is, each pixel has two LED cores: one for the red core, one for the green core. Red light tube core when the pixel is red, green light tube core when the pixel is green, red and green tube core at the same time when the pixel is yellow. Which red, green is called the base color.
9, full-color red and green dual-color plus blue base color, three base colors constitute a full-color. As a result of the composition of the full-color blue tube and pure green tube core technology is now mature, so the market is basically full-color.
2, according to the display device classification
LED digital display: display device for the 7-segment code digital tube, suitable for the production of the clock screen, interest rate screen, etc., display digital electronic display.
LED dot-matrix graphic display: the display device is composed of many evenly spaced light-emitting diodes dot-matrix display module, suitable for playing text, image information.
LED video display: the display device is composed of many light-emitting diodes, can display video, animation and other various video files.
3, according to the use of occasions classification
Indoor display: light-emitting point is smaller, generally Φ3mm - Φ8mm, the display area is generally a few to a dozen square meters.
Outdoor display: the area is generally dozens of square meters to hundreds of square meters, high brightness, can work in the sun, with windproof, rainproof, waterproof function.
4, according to the diameter of the light-emitting dots classification
Indoor screen: Φ3mm, Φ3.75mm, Φ5mm,
Outdoor screen: Φ10mm, Φ12mm, Φ14mm, Φ16mm, Φ18mm, Φ20mm, Φ25mm, Φ31.25mm, Φ36mm,
Outdoor screen (according to the pitch points) PH10, PH12, PH14, PH16, PH20, PH25, PH31.25, PH37.5 ......
Outdoor screen light-emitting basic unit for the light-emitting cylinder, the principle of light-emitting cylinder is a group of red, green and blue light-emitting diodes sealed in a plastic tube *** with light-emitting enhancement of brightness.
Super grayscale control with 1024-4096 levels of grayscale control, display color 16.7M or more, clear and realistic color, three-dimensional sense of strong.
Static scanning technology Adopting static latch scanning mode, high power drive, fully guarantee the luminous brightness.
Automatic Brightness Adjustment With the automatic brightness adjustment function, you can get the best playback effect in different brightness environments.
Comprehensive use of imported large-scale integrated circuits, greatly improving reliability, easy to debug and maintain.
All-weather work Fully adapt to a variety of harsh outdoor environments, anti-corrosion, waterproof, moisture, lightning, shock overall performance, cost-effective, good display performance, pixel tube can be used P10mm, P16mm and other specifications.
Advanced digital video processing, technology distributed scanning, modular design/constant-current static drive, brightness automatically adjusted, ultra-high-bright pure color pixel image picture is clear, no jitter and ghosting, to eliminate distortion
Video, animation, charts, text, pictures, and other kinds of information display, network display, remote control.
Three: LED color and process
The different materials used to manufacture LEDs can produce photons with different energies, which can control the wavelength of the light emitted by the LEDs, that is, the spectrum or color. The material used in the first LED in history was arsenic (As) gallium (Ga), whose forward PN junction voltage drop (VF), which can be interpreted as the light-up or operating voltage) was 1.424V, and the light emitted was in the infrared spectrum.
Another commonly used LED material for phosphorus (P) gallium (Ga), its forward PN junction voltage drop of 2.261V, the light emitted is green.
3. Based on these two materials, the early LED industry used GaAs1-xPx material quartz structure, theoretically can be produced from the infrared light has been to the green light range of any wavelength of the LED, the subscript X on behalf of the phosphorus element to replace the arsenic element percentage. Generally through the PN junction voltage drop can determine the wavelength color of the LED. Typical of which are GaAs0.6P0.4 red LED, GaAs0.35P0.65 orange LED, GaAs0.14P0.86 yellow LED and so on. As the manufacture of gallium, arsenic, phosphorus three elements, so commonly known as these LEDs for the three-element light-emitting tube. And GaN (gallium nitride) blue LED, GaP green LED and GaAs infrared LED, known as two-element light-emitting tube. The latest process is to use a mixture of aluminum (Al), calcium (Ca), indium (In) and nitrogen (N) four elements of the four elements of the AlGaInN four elements of the material manufactured four elements of the LED, can cover all the visible light as well as some of the spectral range of the ultraviolet light. Luminous intensity:
Four: LED display development process 40 years review
1970s the earliest GaP, GaAsP homojunction red, yellow, green low luminous efficiency LED has begun to be applied to the indicator, digital and text display.
From then on, LED began to enter a variety of applications, including aerospace, aircraft, automotive, industrial applications, communications, consumer products, etc., across all sectors of the national economy and thousands of households. By 1996 LED sales worldwide had reached billions of dollars. Although the LED has been subject to color and luminous efficiency limitations over the years, but due to the GaP and GaAsP LED has a long life, high reliability, low operating current, compatible with TTL, CMOS digital circuits, and many other advantages and thus has been by the user's green eyes.
In the last decade, high brightness, full-color has been the LED materials and device process technology research on the forefront of the subject. Ultra-high brightness (UHB) refers to the luminous intensity of 100mcd or more LED, also known as Candela (cd) level LED. high brightness A1GaInP and InGaN
LED development has progressed very rapidly, has now reached the conventional materials GaA1As, GaAsP, GaP impossible to achieve the performance level. 1991 Toshiba and the United States of America developed InGaInP and HP. HP developed into InGaA1P 620nm orange ultra-high brightness LED, 1992 InGaA1p590nm yellow ultra-high brightness LED practical. In the same year, Toshiba developed InGaA1P 573nm yellow-green ultra-brightness LED, normal light intensity of 2cd. 1994 Japan's Nichia company developed into InGaN 450nm blue (green) color ultra-brightness LED. up to this point, the color display required by the three primary colors of red, green, blue, as well as orange, yellow LEDs of a variety of colors have reached the Candelas level of luminous intensity, the realization of the ultra-brightness, full-color. Degree, full-color, so that the outdoor full-color display of light-emitting diodes has become a reality.
China's development of LED began in the seventies, the industry appeared in the eighties. There are about 100 enterprises, 95% of the manufacturers are engaged in back-channel encapsulation production, almost all of the required core imported from abroad. Through several "Five-Year Plan" of technological transformation, technological research, the introduction of foreign advanced equipment and some key technologies, so that China's LED production technology has been a step forward.
Second, the performance of ultra-high brightness LED: ultra-high brightness red A1GaAsLED and GaAsP-GaP LED compared to a higher luminous efficiency, transparent liner low (TS) A1GaAs LED (640nm) lumens efficiency has been close to 10lm / w, 10 times larger than the red GaAsP-GaP LED. Ultra-high brightness InGaAlP LEDs offer the same colors as GaAsP-GaP LEDs including: green-yellow (560nm), light green-yellow (570nm), yellow (585nm), light yellow (590nm), orange (605nm), light red (625nm deep red (640nm). Transparent substrate A1GaInP LED luminous efficiency compared with other LED structures and incandescent light sources, InGaAlP LED absorption substrate (AS) lumen efficiency of 101m/w, transparent substrate (TS) for 201m/w, in the wavelength range of 590-626nm than GaAsP-GaP LED lumen efficiency is higher than 10-20 times; and 2-4 times higher than GaAsP-GaP LEDs in the wavelength range of 560-570. Ultra-high brightness InGaN LEDs provide blue and green light, with wavelength ranges of 450-480nm for blue, 500nm for blue-green, and 520nm for green; and their lumen efficiencies are 3-151m/w. The current lumen efficiencies of ultra-high brightness LEDs have already exceeded that of incandescent lamps with filters, and they can replace incandescent lamps with power of less than 1w. Power 1w within the incandescent lamp, and with LED arrays can replace the power 150w within the incandescent lamp. For many applications, incandescent lamps are used to get red, orange, green and blue filters, and with ultra-high brightness LEDs can get the same color. In recent years, AlGaInP material and InGaN material manufactured ultra-brightness LEDs will be more than one (red, blue, green) ultra-brightness LED chips together, without filters can also get a variety of colors. Including red, orange, yellow, green, blue, its luminous efficiency have exceeded the incandescent lamp, is close to the fluorescent lamp. Luminous brightness has been higher than 1000mcd, can meet the outdoor all-weather, full-color display needs, with LED color big screen can show the sky and the ocean, realize three-dimensional animation. A new generation of red, green and blue ultra-high brightness LED has reached unprecedented performance.
Third, the application of ultra-high brightness LED: 1. information indicators
Car signaling: car indicators in the car's exterior is mainly directional lights, taillights and brake lights; in the car's interior is mainly a variety of instrumentation lighting and display. Ultra-high brightness LEDs for automotive indicators have many advantages over traditional incandescent lamps, and have a wide market in the automotive industry.LEDs can withstand strong mechanical shock and vibration. The average operating life MTBF is several orders of magnitude higher than that of incandescent bulbs, much higher than that of the car itself, so LED brake lights can be packaged as a whole without having to consider maintenance. Transparent substrate Al.GaAs and AlInGaP LED and incandescent bulbs with filters compared with a fairly high lumen efficiency, so that the LED brake lights and directional lights will be able to work in a lower drive current, the typical drive current is only incandescent 1/4, thus reducing the car used for the driving distance. Lower electrical power can also reduce the size and weight of the car's internal wiring system, while also reducing the internal temperature rise of the integrated LED signal lights, allowing the lens and housing to use a lower temperature resistance of the plastic. LED brake light response time of 100ns, shorter than the response time of incandescent lamps, which will give the driver more time to respond to the driver, thereby improving the safety of driving to ensure. The illumination and color of the exterior lights of the car are clearly defined. The car's internal lighting display is not like the external signal light by the relevant government departments of the control, but the car's manufacturers of LED color and illumination requirements. GaP LED has long been used in the car, ultra-high brightness AlGaInP and InGaN LED due to the color and illumination to meet the manufacturer's requirements, and therefore will be more to replace the incandescent lamps in the car. In terms of price, although LED lights are still more expensive compared to incandescent lights, there is no significant difference between the two in terms of the overall system. With the development of the utility of ultra-high brightness TS AlGaAs and AlGaInP LEDs, prices have been decreasing in recent years, and will decrease even more in the future.
Traffic signaling: ultra-high brightness LEDs to replace incandescent lamps for traffic signals, warning lights, signs are now all over the world, the market is broad, the demand is growing rapidly. According to the U.S. Department of Transportation in 1994 statistics, the United States installed traffic signals at intersections of 260,000, each intersection at least 12 red, yellow, blue-green signals. Many intersections have some additional turn signs and crosswalk warning lights for crossing the street. This allows for 20 signals per intersection, all illuminated at the same time. This can be deduced that the United States has about 135 million traffic signals across the country. At present, the use of ultra-high brightness LED to replace the traditional incandescent lamps to reduce power loss has achieved significant results. Japan's annual power consumption in traffic signals for about 1 million kilowatts, the use of ultra-high brightness LED to replace incandescent lamps, its power consumption is only 12% of the original.
Traffic signals in each country's competent authorities to develop the corresponding specifications, the provisions of the signal color, the minimum intensity of illumination, beam spatial distribution of the pattern, as well as the requirements of the installation environment, etc.. Although these requirements are written in accordance with the incandescent lamp, but the current use of ultra-high brightness LED traffic signals are basically applicable.
LED traffic signals and incandescent lamps, compared with a longer working life, generally up to 10 years, taking into account the impact of harsh outdoor environments, it is expected to reduce the life to 5-6 years. Currently ultra-high brightness AlGaInP red, orange, yellow LED has been industrialized, the price is relatively cheap, if the red ultra-high brightness LED module to replace the traditional red incandescent traffic signal head can be due to the sudden failure of red incandescent lamps to the safety of the impact caused by the lowest degree. General LED traffic signal module consists of a number of groups of series-connected LED lamps, 12-inch red LED traffic signal module, for example, in 3-9 groups of series-connected LED lamps, each group of series-connected LED lamps number 70-75 (total 210-675 LED lamps), when there is a LED lamp in series-connected LED lamps. ), when there is a LED single lamp failure, will only affect a group of signals, the rest of the groups reduced to the original 2/3 (67%) or 8/9 (89%), and will not be like incandescent lamps to make the entire signal head failure.
The main problem with LED traffic signal modules is that the cost still seems to be higher to 12-inch TS-AlGaAs red LED traffic signal modules, for example, was first used in 1994, the cost of 350 $, and by 1996 better performance of the 12-inch AlGaInP
LED traffic signal modules, the cost of $ 200. It is expected that the price of InGaN blue-green LED traffic signal modules will be comparable to AlGaInP not long from now. Incandescent traffic signal head cost is low, but power consumption, a 12-inch diameter incandescent traffic signal head power consumption of 150W, crossing the road sidewalk traffic warning lights power consumption of 67W, it is calculated that each intersection of incandescent signals per year of power consumption of 18,133KWh, equivalent to the annual electricity bill of 1450$; however, the LED traffic signal module is very power-saving! However, the LED traffic signal module is very power-saving, each 8-12 inches of red LED traffic signal module power consumption of 15W and 20W, respectively, the LED sign at the corner of the intersection can be used to display the arrow switch, power consumption is only 9w, according to the calculation, each intersection can save electricity 9,916KWh per year, equivalent to the annual savings of $793 electricity costs. According to the average cost of each LED traffic signal module 200 $, the red LED traffic signal module only with its savings in electricity, 3 years after the initial cost can be recovered, and began to get economic returns. Therefore, the current use of AlGaInP LED traffic information module, although the cost appears to be the ground, but from the long view, or cost-effective.
2. Large screen display
Large screen display is another huge market for ultra-high brightness LED applications, including: graphics, text, digital monochrome, two-color and full-color display. In Table 2 lists the various uses of LED displays. Traditional large screen active display generally use incandescent lamps, fiber optics, cathode ray tubes, etc.; passive display is generally used in the flip-flop method.
Table 3 lists a comparison of the performance of several displays.
LED display had been limited by the performance and color of the LED itself. Today, ultra-high brightness AlGaInP, TS-AlGaAs, InGaN LEDs have been able to provide bright red, yellow, green, blue various colors, can fully meet the requirements to achieve a full-color large-screen display.LED display can be assembled according to the pixel size of a variety of structures, small pixels are generally less than 5mm in diameter, each pixel of a single-color display with a T-1 (3/4) LED lamps. Each pixel of a two-color display is a two-color T-1(3/4) LED, and a full-color display requires three T-1 red, green, and blue lamps, or the assembly of a multi-chip T-1(3/4) LED as a pixel. Large pixels, on the other hand, are constructed by combining many T-1(3/4) red, green, and blue LEDs together. With InGaN (480nm) blue, InGaN (515nm) green and ALGaAS (637nm) red LED lamps as the LED display of the three primary colors, can provide realistic panchromatic performance, but also has a large range of colors including: blue-green, green-red, and so on, and the International Television System Committee (NTSC) stipulates that the color range of the television is basically consistent.
3. Liquid crystal display (LCD) back lighting
At least 10% in the liquid crystal display using active light as a back lighting, light source can make the LCD display easy to read in dark environments, full-color LCD displays also need to be a light source. LCD back lighting light source required are: incandescent light bulbs, field emitting luminescence, cold cathode fluorescence, LEDs, etc., which are listed in Table 4 for comparison, in which the LED in the LCD back lighting is required. Comparison, in which the LED in the LCD back lighting is the most competitive, the new ultra-high brightness AlGaInP, AlGaAs, InGaN LED can provide high efficiency light and a wide range of colors.
There are three main ways that LEDs are used for LCD back lighting. (1) the simplest is to install the LED lamp directly behind the LCD scattering film, available in many packaged LED lamps, they should have a very wide beam angle to make the axial light uniformity is good. Can also use the unencapsulated core, generally with GaP LED, however, with AlGaInP, TS-AlGaAs LED can be operated under small current, reducing power consumption. (2) Another way is edge light LCD back lighting, with a transparent or semi-transparent rectangular plastic block as a light guide, will be installed directly behind the LCD scattering film, the rear surface of the plastic block is coated with white reflective material, LED light from the plastic block of a side into the rest of the side for the white reflective material. (3) LED light into the fiber optic bundle, the fiber optic bundle behind the scattering film constitutes a flat sheet, you can use different methods of light out of the sheet as the back of the LCD lighting. The use of LEDs as backlighting LCD can be used for cell phones, notebook computers, with small LCDs in the power-saving communications products in the extensive use, there will be a greater demand for ultra-high brightness LEDs.
4. Solid lighting
Full-color ultra-brightness LED's practical and commercialization, so that the lighting technology is facing a new revolution, by a number of ultra-brightness red, blue, green LEDs made of solid state lighting lamps not only can send out the wavelength of a variety of continuously adjustable color light, but also can send out the brightness can be up to dozens of a hundred candelas of the white to become the source of illumination. Recently, Japan's Nichia company using its InGaN blue LED and fluorescent technology, and launched a white solid light-emitting device products, its color temperature of 6500K, efficiency up to 7.5 lumens per watt. For the same luminous brightness of incandescent lamps and LED solid state lighting lamps, the latter's power consumption is only 10% -20% of the former, incandescent lamp life is generally not more than 2,000 hours, while the life of the LED lamp up to tens of thousands of hours. This small size, light weight, good directionality, energy saving, long life, resistance to a variety of harsh conditions of the solid light source will certainly impact on the traditional light source market. Although the cost of this new lighting solid light source is still high, but can be applied to some special occasions such as mining, diving, rescue, military installations such as lighting. In the long run, if the production scale of ultra-high brightness LED is further expanded, the cost is further reduced, its advantages in energy saving and long life is enough to make up for the disadvantage of its high price. Ultra-high brightness LED will likely become a very competitive new electric light source.
5. Outdoor full-color series led display product features:
Strong applicability: Shanmu display specializes in a variety of outdoor environments for research, and the results are applied to the design of the system, so that its products in a variety of harsh outdoor environments in the adaptability and reliability have been significantly improved; colorful: by the three-color (red, green, blue) display unit box, red, green, Blue 256 levels of gray scale constitutes 16777216 colors, so that the electronic screen to achieve the display of colorful, high saturation, high resolution, high display frequency of dynamic images; Scope of application: government plazas, leisure plazas, bustling business centers, advertising and information dissemination boards, commercial streets, railway stations and so on.
5. Display modes include static, horizontal scrolling, vertical scrolling and page-flipping display. Single module control drive 12 (up to 24) 8X8 dot matrix, ****16X48 dot matrix (or 32X48 dot matrix), is a single MAX7219 (or PS7219, HD7279, ZLG7289 and 8279 and other similar LED display driver module) 12 times (or 24 times)! Can be used "cascade" way to form any dot matrix large display. Good display, low power consumption, and lower cost than the MAX7219 circuit.