The LED display is a Flat panel display, made up of small LED modules that display text, images, video, video signalsGrayscale, and other information.
LED, light-emitting Diode (short for light emitting diode). It is a diode made of gallium (Ga) with compounds of arsenic (As), phosphorus (P), nitrogen (N), and indium (In), which radiates visible light when electrons are combined with holes, by means of a light-emitting diode display So it can be used to make light-emitting diode. Serving as an indicator light in circuits and instruments or constituting a literal or digital display. GALLIUM arsenide diodes glow red, gallium phosphide green, silicon carbide yellow, and indium gallium nitride.
Expression of LED Display with different languages
LED display, LED screen, Pantalla LED, paineis de LED, Affichage LED, LED vertoning, Ekran LED, LED ማሳያ, شاشة LED, LED էկրան, LED ekranı, LED pantaila, святлодыёдны дысплей, LED প্রদর্শন, LED ekran, LED дисплей, Kuwonetsera kwa LED, LED di mostra, LED zaslon, LED displej, LED ekrano, LED-ekraan, LED-näyttö, Affichage LED, LED დისპლეი, LED-Anzeige, Οθόνη LED, એલઇડી ડિસ્પ્લે, Dirije ekspozisyon, LED nuna, Hōʻike ka LED, תצוגת LED, एलईडी प्रदर्शन, LED zaub, LED kijelző, LED skjá, Ngosipụta ọkụ, Tampilan LED, Taispeáint faoi stiúir, Display a LED, LEDディスプレイ, Tampilan LED, ಎಲ್ಇಡಿ ಪ್ರದರ್ಶನ, LED дисплейі, បង្ហាញ LED, LED 디스플레이, LED дисплей, DUXERIT ostentationem, LED displejs, LED ekranas, LED дисплеј, Paparan LED, LED ഡിസ്പ്ലേ, LED wiri, Whakaaturanga rama, एलईडी प्रदर्शन, LED дэлгэц, LED Display ကို, एलईडी प्रदर्शन, LED-skjerm, د LED نندارتون, صفحه نمایش LED, Wyświetlacz LED, LED ਡਿਸਪਲੇ, Afișaj LED, Lili faʻaalia, Taisbeanadh LED, ЛЕД дисплеј, Pontšo ea LED, LED kuratidza, ليڊ ڊسپلي, LED තිරය, LED displej, LED zaslon, Muuqaalka LED, tampilan LED, Kuonyesha LED, Намоиши LED, LED காட்சி, LED డిస్ప్లే, จอแสดงผล LED, Світлодіодний дисплей, ایل ای ڈی ڈسپلے, LED displeyi, Màn hình LED, Arddangos LED, Ukubonisa i-LED, געפירט אַרויסווייַזן, Ifihan LED etc.
Aliases: LED screen, LED advertisement screen, an electronic display screen
LED Module Size: 200mm*150mm, 200mm*300mm, 192mm*192mm, 200mm*168.75mm, 300mm*168.75mm, 240mm*240mm, 250mm*250mm, 256mm*128mm, 128mm*128mm, 256mm*256mm,320mm*160mm, 192mm*192mm, 256mm*256mm, 160mm*160mm, 160mm*320mm, 244mm*244mm, 192mm*192mm, 160mm*80mm, 192mm*96mm, 384mm*192mm, 244*122mm, 320mm*168mm, 480mm*240mm, 304.8mm*304.8mm/ 1’*1′ etc.
▪ Ultra-high brightness
▪ Large screen display
▪ Product Features
7 Technological advantages
▪ Dot matrix module scheme
▪ Single light scheme
▪ Patching scheme
▪ Sub-surface solution
9 Technical Indicators
▪ Pixel out of control rate
▪ Brightness discrimination level
▪ Grayscale nonlinear transformation
▪ Drive mode
10 Pollution Prevention
▪ Mosaic installation
▪ Hanging installation
▪ Wall mounted
▪ Roof mounted
▪ Column mounting
12 Frequently asked questions
▪ Source of static electricity
▪ Electrostatic discharge failure
▪ Anti-static measures
▪ Transportation and packaging
13 The best in the world
15 Heat dissipation
16 Buying tips
17 Dimensional design
19. Consider the problem
20 Future trends
The luminous color and luminous efficiency of LED is related to the material and technology of making LED. In the beginning, the lamp ball is all blue light, and then added phosphors. According to the different needs of users, different light colors can be adjusted Red, green, blue, and yellow are widely used. Because the LED working voltage is low (only 1.2 ~ 4.0 v), it can emit light actively and has a certain brightness, and the brightness can be adjusted by voltage (or current), and it is also impact resistant, vibration resistant and long life (100,000 hours), so in large-scale display equipment, no other display can match the LED display.
A display made by combining red and green LED chips or light bulbs for a single pixel is called a tricolor or double primary color screen Putting red, green, and blue LED chips or tubes together as a pixel on a display is called a primary color or full color. If there is only one color is called single-color or single-color screen, making indoor LED screen pixel size is generally 1.5-12 mm, often using several can produce different primary color LED core package into one Outdoor LED screen pixel size for most of the 6-41.5 mm, each pixel by a number of various single-color LED composition, the common product called Pixel Cylinder, two-color Pixel cylinder is generally composed of 2 red 1 green, three-color Pixel is composed of 1 red 1 green 1 blue.
Whether using LED to make single color, tri-color or full-color screen, to display the image must be composed of pixels of each LED brightness must be able to adjust, the degree of fine adjustment is the gray level of the screen. The higher the gray level, the finer the image is displayed, the richer the color is, and the more complex the corresponding display control system is generally 256 gray-scale image, a color transition has been very soft, and 16 gray-scale color image, color transition line is very obvious. Therefore, color LED screen are currently required to be made of 256 to 4096 grayscale.
The LED luminescent materials used in the display screen have the following forms:
1, LED light (or single light) Generally consists of a single LED chip, reflector, metal anode, metal cathode, and an epoxy resin shell with light-transmitting ability. One or more (different color) single lamps can be used to form a basic pixel, which is mostly used for outdoor displays due to high brightness.
2, LED dot matrix module The light matrix is composed of several wafers and encapsulated in a plastic case with epoxy resin. It is suitable for row and column scanning drive, and it is easy to form a high-density display screen, which is mostly used in the indoor display.
3, SMD LED lighting (or SMD LED) is the package of LED lighting, which can be used in indoor full-color display, which can realize single-point maintenance and effectively overcome the mosaic phenomenon.
1, the area is malleable, the LCD area is large, it is difficult to achieve seamless splicing, the LED display can be arbitrarily extended, and seamless splicing.
2, LCD plasma screen luminous flux attenuation is very fast, generally run about a year and a half or so, you need to replace, but the LED display under the same operating conditions for at least five years no problem.
3, LED brush screen machine can use interactive technology to enhance the interaction between the screen and the advertising audience, such as a custom touch screen, cloud technology broadcast control management.
4, In terms of display effect, the high brightness of the LED display screen, the wide viewing angle and the good color reproduction ability are also superior to the LCD screen. LED brush screen machines are generally used in airports, shopping malls, hotels, high-speed rail, subway, cinema, exhibitions, office buildings, etc., target customers have strong spending power and have huge advertising value.
The reason why LED has been widely recognized and developed rapidly is inseparable from its own advantages. These advantages are summarized as follows: high brightness, low operating voltage, low power consumption, large size, long life, impact resistance, and stable performance. The development prospect of LED is extremely broad, and it is developing towards higher brightness, higher weather resistance, higher luminous density, higher luminous uniformity, reliability, and full color. An LED display is widely used for advertising in different outdoor venues such as stadiums, commercial applications, banks, securities, postal services, terminals, shopping malls, stations, postal services, telecommunications, institutions, surveillance, schools, restaurants, hotels, entertainment, etc. Propaganda, the 2013 Russian Universiade UNILUMIN uses Umesh25 building screen real-time broadcast screen smooth and delicate.
Static scanning technology adopts static latch scanning mode, high power drive, fully guarantees the brightness of illumination. Automatic brightness adjustment has automatic brightness adjustment function, which can get the best playback effect under different brightness environments. LED display keeps brightness while There is also a drawback, that is, in the rainy days, the LED display screen is wet by the rain, and the human eye can easily induce eye diseases when facing the display screen for a long time, and there is a situation of tearing. This kind of light source pollution, LED display as Environmental protection technology should require more consideration of the emotional impact of light on people, and not the excessive pursuit of brightness.
Fully adopting imported large-scale integrated circuits, the reliability is greatly improved, and it is easy to debug and maintain.
The LED luminescent materials used in the display screen have the following forms:
1 LED light (or single light) Generally consists of a single LED chip, reflector, metal anode, metal cathode, and an epoxy resin shell with light-transmitting ability. One or more (different color) single lamps can be used to form a basic pixel, which is mostly used for outdoor displays due to high brightness.
2 LED dot matrix module The light matrix is composed of several wafers and encapsulated in a plastic case with epoxy resin. It is suitable for row and column scanning drive, and it is easy to form a high-density display screen, which is mostly used in the indoor display.
3 SMD LED lighting (or SMD LED) is the package of LED lighting, which can be used in indoor full-color display, which can realize single-point maintenance and effectively overcome the mosaic phenomenon.
LED display performance is superior:
1) The brightness of the light is strong. When the sunlight is directly on the screen surface within the visible distance, the display content is clearly visible. Super gray control, with 1024-4096 gray level control, the display color is 16.7M or more, the color is clear and vivid, and the stereoscopic effect is strong.
2) Static scanning technology. Using static latch scanning mode, high power drive, fully guarantee the brightness of the light.
3) Automatic brightness adjustment. With automatic brightness adjustment function, it can get the best playback effect under different brightness conditions.
4) Fully adopting imported large-scale integrated circuits, the reliability is greatly improved, and it is easy to debug and maintain.
5) Advanced digital video processing, technical distributed scanning, BSV LCD splicing technology HD display, modular design / constant current static drive, automatic brightness adjustment, super bright solid color pixels, clear image, no jitter, and ghosting, Eliminate distortion. Video, animation, graphics, text, pictures and other information display, network display, remote control.
The color of the LED is different from the material used to make the LED, and photons with different energies can be generated, thereby controlling the wavelength of the light emitted by the LED, that is, the spectrum of color.
- The material used in the history of the first LED is arsenic (As) gallium (Ga), its forward PN junction voltage drop (VF, can be understood as lighting or operating voltage) is 1.424V, the emitted light is an infrared spectrum.
- Another commonly used LED material is phosphorous (P) gallium (Ga), which has a forward PN junction voltage drop of 2.261V and emits green light.
- Based on these two materials, the early LED industry used the GaAs1-xPx material structure to theoretically produce LEDs from infrared light to any wavelength in the green range. The subscript X represents the percentage of phosphorus replaced by arsenic. The wavelength of the LED is typically determined by the PN junction voltage drop. Typical examples include a red LED with GaAs 0.6P0.4, an orange LED with GaAs 0.35P0.65, and a yellow LED with GaAs 0.14P0.86. Since the manufacturing uses three elements of gallium, arsenic and phosphorus, these LEDs are commonly referred to as three-element luminous tubes. The GaN (gallium nitride) blue LED, the GaP green LED, and the GaAs infrared LED are called two-element LEDs. The latest technology is a four-element LED made of four elements of AlGaInN mixed with aluminum (Al), calcium (Ca), indium (In) and nitrogen (N). It can cover all visible light and some UV. The spectral range of light.
- Luminous intensity is measured in units of illuminance (lux), luminous flux units (lumen Lumen), and luminous intensity units (candlelight power)
- 1CD (candlelight) refers to the luminous intensity of a completely radiated object at an area of one-sixth of a square centimeter at the freezing point of platinum. (Formerly a whale oil candle with a diameter of 2.2 cm and a mass of 75.5 grams, burning 7.78 grams per hour, a flame height of 4.5 cm, luminous intensity along the horizontal direction)
- 1 Lm (lumen) refers to the luminous flux of a 1 CD candle illuminated on a plane having a distance of 1 cm and an area of 1 cm 2.
- 1Lux refers to the illuminance of 1L of luminous flux evenly distributed over an area of 1 square meter.
- Generally, the active illuminator adopts a luminous intensity unit candle CD, such as an incandescent lamp, an LED, etc.; a reflective or penetrating object uses a luminous flux unit lumen L, such as an LCD projector, and the illuminance unit Lux Lux, which is generally used in photography and the like. The three units of measure are numerically equivalent but need to be understood from different angles. For example, if the brightness (light flux) of an LCD projector is 1600 lumens, and the size of the projection to the total reflection screen is 60 inches (1 square meter), the illumination is 1600 lux, assuming that the light exits from the light source 1 In centimeters, the area of the light exit is 1 square centimeter, and the luminous intensity of the light exit is 1600CD. The true LCD projector, due to loss of light propagation, loss of reflection or light-transmissive film, and uneven distribution of light will greatly reduce the brightness, and generally, 50% efficiency is very good.
- In actual use, light intensity calculations often use data units that are easier to map or use. For the LED display screen, the active illuminant generally adopts CD/m2 as the unit of luminous intensity, and the observation angle is used as an auxiliary parameter, which is equivalent to the illuminance unit of the screen surface; this value and the effective display area of the screen Multiply, the illuminance of the entire screen at the optimal viewing angle is obtained. Assuming that the illuminance of each pixel in the screen is constant within the corresponding space, this value can be considered as the luminous flux of the entire screen. Generally, the outdoor LED display must have a brightness of more than 4000CD/m2 to have an ideal display effect under daylight. Ordinary indoor LED, the maximum brightness is about 700 ~ 2000 CD / square meter. The luminous intensity of a single LED is in units of CD, and is equipped with a viewing angle parameter. The luminous intensity has no relationship with the color of the LED. The luminous intensity of a single tube varies from a few mCD to five thousand mCD. The luminous intensity given by the LED manufacturer refers to the point at which the LED illuminates at a current of 20 mA, with the highest luminous intensity at the best viewing angle and at the center position. The shape of the top lens and the position of the LED chip from the top lens when packaging the LED determine the LED viewing angle and intensity distribution. Generally speaking, the larger the LED viewing angle is, the smaller the maximum luminous intensity is, but the luminous flux accumulated on the entire three-dimensional hemisphere is unchanged.
- When a plurality of LEDs is relatively tightly discharged, the illuminating spheres are superimposed on each other, resulting in a relatively uniform distribution of luminous intensity of the entire illuminating plane. When calculating the luminous intensity of the display screen, it is necessary to multiply the maximum point luminous intensity value provided by the manufacturer by 30% to 90% according to the LED viewing angle and the emission density of the LED as the average luminous intensity of the single tube.
- Generally, the luminous life of LEDs is very long, and manufacturers generally indicate that they are more than 100,000 hours. Actually, attention should also be paid to the brightness decay period of LEDs. For example, most of the UR red tubes used for automobile taillights are illuminated for ten to several tens of hours. It’s only half of the original. The brightness decay period has a lot to do with the material process of LED production. Generally, when the economic conditions permit, a four-element LED with slower luminance attenuation should be selected.
- White is a mixture of red, green and blue colors according to the brightness ratio. When the brightness of the green light is 69%, the brightness of red is 21%, and the brightness of blue is 10%, the human eye feels pure white after color mixing. However, the chromaticity coordinates of the LED red, green and blue colors cannot achieve the full chromatographic effect due to the process and the like, and the control primary colors include the brightness of the biased primary colors to obtain white light, which is called color matching.
- Before color matching for a full-color LED display, in order to achieve the best brightness and the lowest cost, LED devices with three primary colors with a luminous intensity of approximately 3:6:1 should be selected to form pixels.
- White balance requires that the three primary colors are still pure white synthesized at the same gray value.
- Primary color, primary color.
- Primary colors refer to the basic colors that can be combined into various colors. The primary colors in the shade are red, green, and blue. If there is a deviation in the primary colors, the area where the color can be synthesized will be reduced, and the triangles in the spectrum table will be reduced. From a visual point of view, the color will not only be biased, but also the degree of richness will be reduced.
LED display screens are classified in a variety of ways and are generally classified as follows:
(1) divided into indoor, outdoor and semi-outdoor according to the use environment
The indoor screen area is generally from less than 1 m² to more than ten m²s. The indoor LED display is used in the indoor environment. This type of display has moderate brightness, large viewing angle, close color mixing distance, lightweight and high density. It is suitable for closer viewing.
The outdoor screen area is generally from a few m²s to tens or even hundreds of m²s, the point density is relatively thin (more than 2500-10000 Pixels per m²), the brightness of the light is 5500-8500cd/m² (different direction, different brightness requirements), in the sun Used under direct shooting conditions, the viewing distance is several tens of meters away, and the screen body has good wind, rain, and lightning protection capabilities.
The semi-outdoor screen is between the outdoor and the indoors. It has a high luminous brightness and can be used outdoors under direct sunlight. The screen has a certain seal, usually under the eaves or in the window.
(2) Divided into monochrome, double base, and three base colors (full color) by color
Monochrome refers to a luminescent material with only one color on the display, mostly single red, and yellow-green on some special occasions (such as funeral homes).
The dual primary color LED display consists of red and green LED lights. The 256-level gray dual-color display can display 65,536 colors (two-color screen can display red, green, and yellow colors).
The full-color LED display consists of red, green and blue LED lights that display white balance and 16,777,216 colors.
(3) Synchronous and asynchronous by control or usage
Synchronous mode means that the LED display works basically the same as the monitor of the computer. It maps the computer image to the map on the real monitor with an update rate of at least 30 fields/second, usually with a multi-gradation color display. Ability to achieve multimedia advertising effects.
Asynchronous mode means that the LED screen has the ability of storage and automatic playback. The edited text and non-grayscale pictures on the PC are transmitted to the LED screen through the serial port or another network interface, and then automatically played by the LED screen offline. Generally, there is no gray. The display capability is mainly used to display text information and can be multi-screened.
(4) Divided by pixel density or pixel diameter
Since the LED dot matrix module used in the indoor screen has relatively uniform specifications, it is usually divided according to the pixel diameter of the module: ∮ 3.0mm 62500 pixels/m² ∮ 3.75mm 44321 pixels/m² ∮ 5.0mm 17222 pixels/m²
Indoor surface mount pixel Pixels:
P1.25 640,000 Pixels/m²
P1.56 409,600 Pixels/m²
P1.58 400,689 Pixels/m²
P1.667 360,000 Pixels/m²
P1.875 284,089 Pixels/m²
P1.904 275,625 Pixels/m²
P1.923 270,400 Pixels/m²
P2.0 250,000 Pixels/m²
P2.5 160,000 Pixels/m²
P3 111,111 Pixels/m²
P4 62,500 Pixels/m²
P5 40,000 Pixels/m²
P6 27,777 Pixels/m²
P7.62 17,222 Pixels/m²
P8 15,625 Pixels/m²
P10 10000 Pixels/m²
Pixel diameter and number of pixels of the outdoor screen
P10 10,000 Pixels/m²
P12.5 6,400 Pixels/m²
P16 3,906 Pixels/m²
P20 2,500 Pixels/m²
P25 1,600 Pixels/m²
P31.25 1,024 Pixels/m²
(5) According to the display, performance can be divided into
Video display: generally full-color display
Text display: generally single-color display
Graphic display: generally dual-color display
Quote display: generally a digital tube or single primary color display;
(6) According to the display device can be divided into
LED digital display: The display device is a 7-segment digital tube, which is suitable for making clock screens, interest rate screens, etc., and displaying digital electronic displays.
LED dot matrix graphic display: The display device is a dot matrix display module composed of a plurality of uniformly arranged light-emitting diodes, which is suitable for playing text and image information.
LED video display: The display device is composed of many light-emitting diodes, which can display various video files such as video and animation.
Conventional LED display: The display is fixed in one position with a steel structure. The main common ones are outdoor large single-column LED advertising screens, as well as single and two-color LED displays installed on the wall for playing the train information.
Rental LED display: At the time of design, the R&D department considers that the screen is often used for installation and disassembly. Therefore, the left and right cabinets are fast-locked with a positioning function, and the positioning is accurate. The entire cabinet is installed within 10 seconds. Rental screens are mainly used for stage performances, wedding venues, and large spring festivals.
(7) According to the direction of development can be divided into :
The “advertising media display” that has been widely used: the single-and-two-color display screen of the door and the full-color display on the surface of the square building are mainly advertising;
“Industrial indicator display” that is quietly rising: to the PLC/DCS and other distributed control systems, supporting an auxiliary display, such as display speed, flow, temperature, pressure, etc.
The red A1GaAs LED has higher luminous efficiency than the GaAsP-GaP LED, and the lumen efficiency of the transparent liner low (TS) A1GaAs LED (640 nm) is close to 10 lm/w, which is 10 times larger than that of the red GaAsP-GaP LED. Ultra-high brightness InGaAlP LEDs provide the same color as GaAsP-GaP LEDs: 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 source, InGaAlP LED absorption substrate (AS) has a lumen efficiency of 101m / w, transparent substrate (TS) is 201m / w, at 590 The lumen efficiency of GaAsP-GaP LED is 10-20 times higher in the -626nm wavelength range and 2-4 times higher than the GaAsP-GaP LED in the 560-570 wavelength range. Ultra-high brightness InGaN LEDs provide blue The color and green light have a wavelength range of 450-480 nm, a blue-green color of 500 nm, a green color of 520 nm, and a lumen efficiency of 3-151 m/w. The lumen efficiency of ultra-high-brightness LEDs exceeds that of incandescent filters. The lamp can replace the incandescent lamp with a power of less than 1w, and the LED array can replace the incandescent lamp with a power of less than 150w. For many applications, the incandescent lamp uses a filter to get red, orange, green and blue, and with super High-brightness LEDs give the same color. AlGaInP materials and InGaN materials. The ultra-high-brightness LEDs are manufactured by combining multiple (red, blue, green) ultra-high-brightness LED chips, and various colors can be obtained without filters, including red, orange, yellow, green, and blue. It has already surpassed the incandescent lamp and is close to the fluorescent lamp. The brightness of the light is higher than 1000mcd, which can meet the needs of outdoor all-weather and the full-color display. The LED color large screen can express the sky and the ocean to realize three-dimensional animation. A new generation of red and green, Blue ultra-high brightness LED has achieved unprecedented performance, can achieve splicing display, using BSV LCD splicing technology to achieve large-screen high-brightness display.
Large screen display
The large screen display is another huge market for ultra-high brightness LED applications, including monochrome, two-color and full-color displays for graphics, text, and numbers. The various uses of the LED display are listed in Table 2. Conventional large-screen active displays generally use incandescent lamps, optical fibers, cathode ray tubes, etc.; passive displays generally use a flop method. Table 3 lists the performance comparisons for several displays. LED displays have been limited by the performance and color of the LED itself. Today, ultra-high-brightness AlGaInP, TS-AlGaAs, and InGaN LEDs are available in bright red, yellow, green, and blue colors to meet the full-color display requirements. The LED display can be assembled into various structures according to the pixel size. The small pixel diameter is generally less than 5mm. Each pixel of the monochrome display uses a T-1 (3/4) LED lamp, and each pixel of the two-color display is two-color. T-1 (3/4) LED lights, full-color display requires 3 T-1 red, green, blue lights, or a multi-chip T-1 (3/4) LED light as a pixel. Large pixels are made up by combining many T-1 (3/4) red, green, and blue LED lights. InGaN (480nm) blue, InGaN (515nm) green and ALGaAs (637nm) red LED lamps are used as the three primary colors of LED display, which can provide realistic full-color performance, and have a large color range including blue-green, green red, etc. It is basically in line with the TV color range stipulated by the International Television System Committee (NTSC).
It has strong applicability and rich colors: it consists of three primary colors (red, green and blue) display unit boxes, and red, green and blue 256-level gray scales constitute 16777216 colors, which makes the electronic screen display rich in color, high saturation and high. Dynamic image with high resolution and high display frequency; scope of application: government plaza, leisure plaza, prosperous business center, advertising information release card, commercial street, railway station, stadium (UNILUMIN Universiade).
Compared with other large screen terminal displays, LED displays have the following main features:
- High Brightness: Outdoor LED display brightness is greater than 8000CD/m², is the only outdoor all-weather use large display terminal; indoor LED display brightness is greater than 2000MCD/m².
- Long Life: LED life up to 100,000 hours (10 years) or more, the parameter generally refers to the design life, the brightness dark also counts;
- Large viewing angle: Indoor viewing angle can be greater than 160 degrees, the outdoor viewing angle can be greater than 120 degrees. The viewing angle depends on the shape of the LED light-emitting Diode 4, screen area can be large or small, small to less than a square meter, large can reach hundreds, thousands of square meters;
- Easy to interface with computer, rich support software.
|TV Wall||Full Color, Large size||The screen has a sense of separation Low brightness cannot be used outdoors, large color difference, high cost|
|PDP||fine picture, small area||Small area, low brightness, short life|
|Projector||full-color, the picture is fine||Brightness is low, it can’t be used outdoors, and the picture is unevenly received.|
Functions and characteristics of Blue Light Intelligent LED display screen
The Blue Light smart displays use the same ASIC as the AVAGO HCMS-29XX smart displays for yellow, orange, red, and green light products, and the package size and pin arrangement are the same as the HCMS-29XX series, which uses a 5×7 point Matrix of a serial interface. These high-performance point-matrix displays are powered by a CMOS chip embedded in the circuit board. Each display can be connected directly to a microprocessor or Microcontroller, eliminating the need for additional interface components. Use serial interface can bring more display word number through minimum connection line number the universal, readable 5×7 Pixel display format also displays Roman letters, Katakana, and other user-defined symbols or characters. These Blu-ray displays are designed to stack vertically and horizontally, making them ideal for multi-character displays.
The Blu smart screen is similar to other Avago smart displays in that the blue LED has high-quality color performance, while the rest is a slight variation on the parameters.
Like other smart displays, the BLU smart display also uses two separate power systems, one as the display’s logic circuit and the other as the LED power supply. Using two power supply system can keep the logic circuit power supply pure, and can independently control the voltage of LED and logic circuit, the LED voltage can vary from 0V to 5.5 v without affecting the DOT Matrix Register or control register.
For Blue LEDs, the voltage can vary between 4.5 v and 5.5 v without causing any noticeable impact on light output or undesirable Pixel differences. Basically, the LED voltage cannot be lower than 4.0 v because blue LEDs have a higher forward conduction voltage than conventional GaP colors; the logic voltage can vary between 3 V and 5.5 v without affecting display information or display strength Working Below 4.5 v will affect the timing and logic levels, and below 3V may cause changes in the Matrix Register and Control Register contents.
The Blue Light smart display provides two ways to change brightness, by controlling the peak current of the Pixel and by using pulse width modulation, which can be set to D0 to D5 bits of the control character group shown in figure 1. In addition, it is not recommended that the LED supply voltage pulse width modulation to control the brightness of the display.
7. Technical advantages
Comparison of existing common indoor full-color schemes:
Dot matrix module solution
The earliest design proposal was developed from the indoor pseudo-color dot matrix screen.
Advantages: The raw material cost is the most advantageous, and the production and processing technology is simple and the quality is stable.
Disadvantages: poor color consistency, more serious mosaic phenomenon, poor display effect.
Single light scheme
In order to solve the problem of dot matrix color, a solution of outdoor display technology is used, and outdoor pixel multiplexing technology (also called pixel sharing technology, virtual pixel technology) is transplanted to the indoor display.
Advantages: Color consistency is better than dot matrix module.
Disadvantages: The color mixing effect is not good, the viewing angle is not large, and there is a color difference in the horizontal direction. The processing is more complicated and the antistatic requirement is high. It is more difficult to achieve an actual pixel resolution of 10,000 points or more.
A patch light tube is used as a display element.
Advantages: Color consistency, viewing angle and other important display indicators are the best in the existing program, especially the three-in-one surface sticker color mixing effect is very good.
Disadvantages: The processing process is cumbersome and the cost is too high.
In fact, it is an improvement of the single lamp scheme, which is still being improved.
Advantages: There is little difference between the display of color consistency, viewing angle and other primary indicators and labeling schemes, but the cost is lower, the display effect is very good, and the resolution can theoretically achieve more than 17200.
Disadvantages: Processing is more complicated and antistatic requirements are high.
- Promote your product to attract customers.
- Play a shop front decoration, improve the role of enterprise-grade.
- It’s about lighting and being original.
- It serves to popularize knowledge. Can Be used to play small enterprise products information, knowledge of the relevant industry
- Act as a bulletin board. (sales promotion, job posting)
- It sets the mood. Through the screen can play superior and all kinds of VIP visit to visit, guide the words of welcome, all kinds of major festive celebration.
- Play a warning role, often used in road traffic LED navigation instructions and so on.
There is no denying that the ultimate goal of setting up advertising boards is to spread the message of goods, attract the target customers and make as much profit as possible. And LED billboard is to achieve this goal to become the first choice of corporate propaganda.
9. Technical Indicators
Pixel out of control rate
Out-of-control Pixel rate is the proportion of the smallest Pixel (Pixel) working abnormally. There are two patterns of out-of-control pixels: One is a blind spot, or blind spot, which is not lit when it needs to be lit, and the other is a constant bright spot, which is lit all the time when it needs to be dark. In general, pixels are composed of 2R1G1B (two red lights, one green light and one blue light, the same as below), 1R1G1B, 2R1G, 3R6G, and so on, but out of control is not usually the same pixel within the red, green, and blue lights all go out of control at the same time But if one of the lights gets out of control, we assume the Pixel is out of control. For the sake of simplicity, we count and calculate the out-of-control pixels according to the basic colors of the LED display, and take the maximum of them as the out-of-control ratio.
The number of out-of-control pixels as a percentage of the total number of pixels on the screen is called the “out-of-control rate for whole-screen pixels”. In addition, to avoid out-of-control pixels being concentrated in one area, we propose the “area out-of-control Pixel rate”, which is the ratio of the number of out-of-control pixels to the total number of pixels in the area (i.e., 10000) within 100100 pixels. This index quantifies the requirement of “the out-of-control pixels are distributed discretely” in the general specification for LED display screen SJ / T11141-2003.
The domestic LED display screen will be aged before it leaves the factory, and the out-of-control Pixel LED lights will be repaired and replaced “whole-screen Pixel out-of-control rate” within 1 / 104, “regional Pixel out-of-control rate” within 3 / 104 is no problem, and even some individual manufacturer’s enterprise standards do not allow out-of-control pixels before factory But this is bound to increase the manufacturer’s manufacturing maintenance costs and extended shipping time. In different applications, the actual requirements of Pixel out-of-control rate can be greatly different. Generally speaking, the LED display screen is used for video playback. The requirement of 1 / 104 is acceptable and can be achieved For simple character information publishing, it is reasonable to limit the specification to 12 / 104
Grayscale is also known as the color scale or Grayscale refers to the brightness of the degree of light. For digital display technology, grayscale is the decisive factor of the number of display colors. Generally speaking, the higher the Grayscale, the richer the color display, the screen is also more delicate, easier to display a wealth of details.
The gray level depends mainly on the A / D conversion bit of the system. Of course, the system’s video processing chip, memory, and transmission system must provide corresponding digital support to go. At present, domestic LED display mainly uses 8-bit processing system, that is 256(28) Grayscale. The simple idea is that there are 256 brightness changes from black to white. Using RGB Tricolor can constitute 256256,256,16777216 kinds of colors. Commonly referred to as 16 terabytes. International brand display screen mainly uses 10-bit processing system, that is, 1024 Grayscale, RGB tricolor can constitute 1.07 billion colors.
Although grayscale is the decisive factor in determining the number of colors but does not mean that the more unlimited the better. Because the resolution of the human eye is limited, and the improvement of system processing bits will involve the changes in system video processing, storage, transmission, scanning and so on. Generally speaking, the 8-bit system can be used in civil or commercial products, and the 10-bit system can be used in broadcast products.
Brightness discrimination level
A luminance level is the brightness of an image that the human eye can distinguish from the darkest to the whitest image. Some of the screens mentioned above have very high grayscale levels, ranging from 256 to 1024. However, due to the limited sensitivity of the human eye to brightness, cannot fully identify these gray levels. This means that many adjacent gradations of grayscale human eyes may look the same. And the ability to see varies from person to person. For the display screen, the more the level of recognition of the human eye is naturally the better because the image is shown for people to see. The more light a person can see, the larger the screen’s color space and the greater the potential for color richness. Luminance discrimination level can be tested with special software, and the general display screen can reach more than 20 levels, even if it is a good level.
Grayscale nonlinear transformation
Non-linear transformation of grayscale refers to the transformation of Grayscale data according to empirical data or some Arithmetic non-linear relationship and then provide to the display screen. Because the LED is a linear device, the non-linear display characteristic is different from the traditional display. In order to let the LED display effect can conform to the traditional data source and at the same time without losing the gray level, generally in the LED display system will do the non-linear transformation of gray level data The number of transformed data bits is increased (to ensure no gray data is lost). Some of the domestic control system suppliers so-called 4096 gray level or 16384 gray level or higher are referred to after non-linear transformation of the grayscale space size. Class 4096 uses a nonlinear transform from 8-bit source to 12-bit space, while class 16384 uses a nonlinear transform from 8 bit to 16-bit space. The non-linear transformation from 8-bit source is more space than the 8-bit source. Usually at least 10. As with Grayscale, this parameter is not as large as it should be, and generally, 12 bits is enough to make the transformation.
Common drive mode is generally a constant-voltage drive and constant-current drive, a constant-voltage drive is a constant voltage input to drive, lighting screen. It’s very rare. The constant-current drive is the use of constant current to provide drive, lighting screen. Common is the 1 / 8th, 1 / 4th, and 1 / 16th Scans. These so-called scanning means are close to several lights of the same color with a driver chip to drive the control. Of course, the more the driver chip brightness, refresh rate, then the higher the cost is. An average of 1 / 8 is a good choice.
10. Pollution Prevention
In the world, the light pollution of the LED display screen is generally divided into three categories: white light pollution, artificial daylight pollution, and color light pollution. At present, only the white pollution of China’s Glass Curtain Wall in the relevant provisions of artificial daylight and light pollution has not yet been relevant provisions. However, considering the light pollution caused by people feel uncomfortable, so in the design of LED display screen should take into account the prevention and control of light pollution.
First, the use of the system can automatically adjust the brightness adjustment system
We know that during the day and night, the brightness of the environment varies greatly at different times and places. If the brightness of the LED display is greater than 60% of the ambient brightness, we obviously feel the discomfort of the eyes, which means that it causes light pollution to people. Through the outdoor brightness acquisition system, the ambient brightness is collected at any time. The display control system automatically converts the broadcast brightness suitable for the environment through software by receiving system data.
Second, multi-level grayscale correction technology
The ordinary display system uses an 8-bit color display level so that the color is hard at some low gray levels and excessive colors. It also causes the incompatibility of colored light. The new LED large-screen control system uses a 14-bit color display layer, which greatly improves the hardness of the color in excess. Make people feel soft when watching. Avoid people’s discomfort with light.
Third, the reasonable choice of installation location and reasonable planning of the display area
There is an empirical plan for viewing distance and viewing angle and display area, while image research has specific design requirements for viewing distance and viewing angle of the display screen. When designing the display screen, it should meet the design requirements as much as possible and plan properly.
Fourth, the selection and design of the content.
LED large screen is a public media, there are public welfare, advertising, instruction and so on. When we choose to play the content, we must agree with the public request to avoid refusal. This is also an important aspect of preventing display light pollution.
The LED diode itself is a green light source. Although it is caused by a design consideration and application requirements on the large-scale LED display screen of the cluster type, this kind of contradiction is inevitable, and It cannot be completely eradicated. Only by using technical means and policies and regulations to minimize the pollution of color light, coordinate the needs of advertisers and the public’s viewing psychology. At the same time, we also see that compared to today’s neon and white light box advertising, the light pollution of the LED display has been greatly reduced. And the LED electronic display also has the advantages of energy saving and rich color, and it will definitely replace the neon outdoor lighting and information display.
The installation and commissioning of the LED display not only reflects the quality of the product but also determines the effect of the display when it is used. There are five common LED display installation methods:
Suitable for indoor screens with a small area. Since the installation space is small, in order not to occupy the space, the same size area is dug on the wall according to the size of the screen body, and the LED display screen is embedded in the wall. The wall is required to be a solid wall. The method of pre-maintenance is costly.
It is more suitable for large-scale places such as station LED electronic display and airport LED electronic display to play the role of indicating signs. It is required that the screen area is small (below 10 square meters), and it is required to have a suitable installation place, such as a beam or a lintel at the top, and the screen body is generally added with a back cover.
It is more suitable for the installation of indoor LED display, the area is small (less than 10 square meters), the wall requirements are solid walls, hollow bricks or simple partition walls are not suitable for this installation.
It is mainly suitable for outdoor advertising LED electronic display. The installation location is mainly the roof of the building. As the height of the building increases, the windproof level to be considered also increases.
It is mostly used for the installation of outdoor advertising LED display screens, where the view is wide and the surrounding areas are relatively empty, such as squares and parking lots. According to the size of the screen body, it can be divided into a single column and double column type.
12. Frequently asked questions:
LEDs attach great importance to anti-static measures. The following are some instructions for static electricity and anti-static:
Source of static electricity
The sources of static electricity that affect the circuit are mainly human body, plastic products, and related equipment. Among them, the static power source from the use environment has the following items:
- Floor, work table and chair
- Work clothes, packaging containers
- Painted or waxed surfaces, organic and fiberglass materials.
- Cement floors, painted or waxed floors, plastic floor tiles or floor leather.
- Chemical fiber overalls, non-conductive work shoes, clean cotton overalls.
- Plastic, box, box, bag, tray, foam pad.
Electrostatic discharge failure
Sudden failures and potential failures.
The electrostatic failure above 90 in the use environment is a potential failure, which shows that the electrical over-stress resistance of the circuit is weakened and the service life is shortened.
- Train static electricity knowledge and related technologies on personnel using static sensitive circuits.
- Establish an anti-static work area, use the anti-static floor, anti-static workbench, anti-static grounding lead and anti-static device in the area, and control the relative humidity to 40 or above.
- The damage caused by static electricity to electronic equipment may be released anywhere from the manufacturer to the field equipment. The hazard is caused by insufficient, effective training and equipment failure. LEDs are devices that are sensitive to static electricity. INGAN wafers are generally considered to be “first” susceptible to interference. And ALINGAP LEDs SHI “second place” or better.
- ESD damaged devices can show dim, blur, extinction, short or low VF or VR. Equipment damaged by ESD should not be confused with electronic overloads, such as incorrect current design or drive, wafer attachment, wire shield grounding or packaging, or common environmental induced pressure.
- ESD security and control procedures: Most electronic and electro-optical companies have very similar ESDs and have successfully implemented ESD control, manipulation and main programs for their devices. These programs have been used to detect quality effects because of ESD. ISO-9000 certification also lists him as a normal control program.
ESD sensitive equipment should always be stored in an antistatic bag or container during daily operation. This includes the inventory of detailed catalogs, shipping, and WIP. Prevention during transport includes the consumption of fleets, boxes or other equipment, such as with conductive wheels or drag-and-drop connections, where the ESD equipment is grounded.
LED companies facing development opportunities First, although China has a certain gap in the production technology of LED upstream epitaxial wafers and chips with the United States, Japan, and the European Union, the application demand in the domestic and international markets is very large, and the terminal consumer market is diversified. Decentralized structure is not easy to form a market monopoly, thus bringing huge opportunities for LED downstream manufacturers, especially for mainland Chinese enterprises with relatively backward technology, there is a large space for survival and development.
Secondly, it is due to the Chinese government’s active promotion of LED industrialization. In 2003, the National Semiconductor Lighting Coordination Leading Group, which established an inter-ministerial committee, launched the “National Semiconductor Lighting Project”. The National “863” Program has also invested in relevant enterprises and research institutions to support basic research and technology research and development.
13.The best in the world
The world’s largest LED display is 9,500 square meters outside the opening ceremony venue of the 2010 World Expo in Shanghai. . .
The LED screens on the market are all in pursuit of being thinner and lighter. The LED transparent screen on display at the theme Pavilion of the 2010 Shanghai World Expo is a successful case. The display area is 400 square meters. It is made of P18 pasted technology, and the structure of the die-cast aluminum box What is more interesting is the ingenious way of installation.
1. The switch sequence:
When opening the screen: first turn on the controller computer, then open the screen. When closing the screen: first turn off the screen, then turn off the controller computer.
(The computer does not turn off the display first, which will cause the screen to appear bright, and the LED burns out the lamp, which has serious consequences.)
- The interval between switch screens should be greater than 5 minutes.
- After the computer enters the engineering control software, it can be powered on.
- Avoid opening the screen in the full white screen state because the system has the largest inrush current. 5. Avoid opening the screen in the out of control state, because the system has the largest inrush current.
A computer does not enter the control software and other programs;
B computer is not powered;
The C control section power is not turned on.
- When the ambient temperature is too high or the heat dissipation conditions are not good, the LED lighting should be careful not to open the screen for a long time.
- When a part of the electronic display body appears very bright, it should be noted that the screen should be turned off in time, and it is not suitable to open the screen for a long time in this state.
- The power switch of the display often trips. Check the screen or replace the power switch.
- Regularly check the firmness of the hook. If there is looseness, pay attention to timely adjustment, re-reinforce or update the hanger.
- According to the environment of the large screen display screen and control part, avoid insect bites, and place anti-rat medicine if necessary.
As LED technology has received extensive attention as a new generation of lighting technology in recent years, LED power has increased, and heat dissipation has become more and more important. According to long-term observation by researchers, this is because the light decay of LED or its lifetime is directly related to its junction temperature. The heat dissipation is not good, the junction temperature is high, and the lifetime is short.
Unlike incandescent lamps and fluorescent lamps used in the past, their energy loss is large, but most of the energy is directly emitted by infrared rays, and the light source generates less heat. LEDs, in addition to being consumed as visible light, convert other energy. It became hot. Since electronic products are gradually moving toward high density and high integration, LED products are no exception. Therefore, solving the problem of LED heat dissipation has become a major problem in improving LED performance and developing the LED industry.
Reasons cause LED heating:
The reason why the LED heats up is that the added electric energy is not converted into light energy, but a part is converted into heat energy. The luminous efficacy of LED is only 100lm/W, and its electro-optic conversion efficiency is only about 20~30%. That is to say, about 70% of the electrical energy becomes heat.
Specifically, the LED junction temperature is caused by two factors:
- The internal quantum efficiency is not high, that is, when electrons and holes recombine, photons cannot be generated 100%, and it is generally called “current leakage” to lower the recombination rate of carriers in the PN region. Multiplying the leakage current by the voltage is the power of this part, which is converted into thermal energy, but this part is not the main component because the internal photon efficiency is close to 90%.
- The internally generated photons cannot be completely emitted outside the chip and finally converted into heat. This part is mainly because the external quantum efficiency is only about 30%, and most of it is converted into heat.
As mentioned above, although the incandescent lamp has a low light efficiency of only about 15 lm/W, it converts almost all of the electrical energy into light energy and radiates it. Because most of the radiant energy is infrared, the light efficiency is very low. But it eliminates the problem of heat dissipation.
LED heat dissipation solution:
Solving the heat dissipation of LEDs mainly starts in two aspects. Before and after packaging, it can be understood as the heat dissipation of LED chips and the heat dissipation of LED lamps. The heat dissipation of the LED chip is mainly related to the selection and process of the substrate and the circuit because any LED will be made into the lamp, so the heat generated by the LED chip is always dispersed into the air through the outer casing of the lamp. If the heat dissipation is not good, because the heat capacity of the LED chip is small, a little bit of heat accumulation will cause the junction temperature of the chip to increase rapidly. If it is operated at a high temperature for a long period of time, its life will be shortened very quickly. However, there is a lot of ways for this heat to actually lead the chip to the outside air. Specifically, the heat generated by the LED chip comes out of its metal heat sink block, first passes through the solder to the PCB of the aluminum substrate, and then passes through the thermally conductive glue to the aluminum heat sink. Therefore, the heat dissipation of LED lamps actually includes two parts: heat conduction and heat dissipation.
However, the heat dissipation of the LED lamp housing may have different options depending on the power level and the place of use. There are mainly the following cooling methods:
- Aluminum fins: This is the most common way to dissipate heat, using aluminum fins as part of the enclosure to increase heat dissipation.
- Thermally conductive plastic case: Fill the thermally conductive material during injection molding of the plastic case to increase the heat conduction and heat dissipation capability of the plastic case.
- Aerodynamics: The use of the shape of the lamp housing to create convective air, which is the lowest cost way to enhance heat dissipation.
- Fan: The inside of the lamp housing is cooled by a long-life and high-efficiency fan, which has low cost and good effect. However, it is more troublesome to change the fan, and it is not suitable for outdoor use. This design is rare.
- Heat pipe: The heat pipe technology is used to guide the heat from the LED chip to the heat sink fin of the casing. Large lamps, such as street lamps, are common designs.
- Surface radiation heat treatment: The surface of the lamp shell is radiated and heat-dissipated. The simple method is to apply Zhisheng Weihua radiation heat-dissipating paint, which can radiate heat away from the surface of the lamp housing.
The following describes a new type of heat-dissipating coating: ZS-411 radiation heat-dissipating coating, which has high thermal conductivity and large heat-dissipating surface area and has high emissivity in a relatively wide wavelength range (1-20μm). Significantly improved overall performance including conduction, convection, and radiative heat dissipation.
The coating uses a high-performance heat-dissipating solution with highly visible and near-infrared light reflectivity, high thermal infrared emissivity and stability, and good physical properties, chemical properties and good properties. The multi-complexity of the construction property, the working principle of the heat-dissipating solution is that the aggregation occurs by the aggregation of the inorganic colloidal particles (less than 100 nm). The addition of carbon nanotubes and other materials with high thermal conductivity and emissivity in the coating solution can make the surface of the coating exhibit a macroscopic, smooth and microscopic rough morphology of the nanomaterial component, which can greatly increase the contact area between the heat sink and the outside. Significantly improve heat dissipation. At the same time, a large number of spinel which has been electronically transitioned are added as composite infrared radiators, which not only increase the impurity level, but also improve the infrared radiation coefficient, and maintain the corresponding thermal stability and heat resistance.
In general, the luminous efficiency of LEDs is still relatively low, resulting in an increase in junction temperature and a decrease in lifetime. In order to reduce the junction temperature to improve life, it is necessary to pay great attention to the problem of heat dissipation.
1, the ambient brightness for the brightness requirements of the screen
The general brightness requirements are as follows:
(1) Indoor: >800CD/M2
(2) Semi-indoor: >2000CD/M2
(3) Outdoor (sitting south to north): >5500CD/M2
(4) Outdoor (sitting north facing south): >8000CD/M2
What are the brightness requirements for red, green and blue in white composition: red, green and blue contribute differently in terms of white-color. The root cause is that the retina of the human eye is different for different wavelengths of light. After a large number of experimental tests, the following approximate ratios are obtained for reference design:
The brightness ratio of simple red, green and blue is 3:6:1, the ratio of brightness to red, green and blue is: 3.0:5.9:1.1. Under the condition of clear brightness and dot density, how to calculate the brightness of a single tube:
The calculation method is as follows: (taking two red, one green, one blue as an example)
Red LED light brightness: brightness (CD) / M2 ÷ points / M2 × 0.3 ÷ 2
Green LED light brightness: brightness (CD) / M2 ÷ points / M2 × 0.6
Blue LED light brightness: brightness (CD) / M2 ÷ points / M2 × 0.1
For example, 2500 points per square meter, 2R1G1B, the brightness requirement per square meter is 5000CD/M2, then:
The brightness of the red LED light is: 5000÷2500×0.3÷2=0.3
The brightness of the green LED light is: 5000÷2500×0.6=1.2
The brightness of the blue LED light is: 5000÷2500×0.1=0.2
The brightness per pixel is: 0.3×2+1.2+0.2=2.0CD
- Consider the factors of the screen area allowed by the user’s site.
(1) The relationship between the effective line of sight and the actual site size;
(2) pixel size and resolution;
(3) The unit is an area estimate of the base;
(4) Screen body mechanical installation and maintenance operation space;
(5) The influence of the inclination of the screen body on the distance.
3, the user needs the playback effect
(1) Text display: depending on the size of the text and the need for resolution;
(2) ordinary video display: 320 × 240 dot matrix;
(3) Digital standard DVD display: ≥ 640 × 480 dot matrix;
(4) Complete computer video: ≥800×600 dot matrix;
4, the factors to be considered in the design of the display size
(1) the need to display content;
(2) Space conditions of the venue;
(3) display unit template size (indoor screen) or pixel size (outdoor screen);
(4) the general aspect ratio of the display;
(5) Graphic screen: determined according to the displayed content;
(6) Video screen: generally 4:3 or close to 4:3 the ideal ratio is 16:9.
5, display power consumption indicators and power requirements
The power consumption of the display is divided into average power consumption and maximum power consumption. The average power consumption, also known as the working power, is the actual power consumption. The maximum power consumption is the power consumption during extreme conditions such as startup or full illumination. The maximum power consumption is an essential factor for AC power supply (wire diameter, switch, etc.). The average power consumption is generally 1/3 of the maximum power consumption.
6, the key indicators of LED
(1) Maximum output current: The current mainstream constant current source LED driver chip has a maximum output current of about 90 mA per channel. The maximum value of the constant current output per channel simultaneously makes more sense for the display, because in the white balance state, it is required to simultaneously output a constant current per channel.
(2) Constant current output channel number: The constant current source output channel has 8 bit and 16-bit specifications, 16 bits occupy the mainstream, and its main advantage is to reduce the chip size and facilitate LED driver board (PCB) wiring, especially for LED driver boards with smaller dot pitches are more advantageous.
(3) Accurate current output: one is the current error value between the same chip channel; the other is the output current error value between different chips. The accurate current output is a critical parameter that has a large impact on the display uniformity of the LED display. The larger the error, the worse the display uniformity is, and it is difficult to achieve a white balance of the screen. The bit to bit current error of the mainstream constant current source chip is generally within ±3%, and the chip to chip current error is within ±6%.
(4) Data shift clock: It determines the transmission speed of the display data and is a key indicator that affects the update rate of the LED display. As a large-size display device, the display refresh rate should be above 85 Hz to ensure a stable picture (no scanning flicker). A higher data shift clock is the basis for the display to obtain a high refresh rate picture. The mainstream constant current source driver chip shift clock frequency is generally above 15MHz ~ 25MHz.
- Dimensions of the display design There are three important factors when designing the screen size:
- (1) The need to display content;
- (2) Space conditions of the venue;
- (3) Display unit template size (indoor screen) or pixel size (outdoor screen).
- Power consumption and power requirements
The maximum power consumption of the light bar is the power consumption during extreme conditions such as start-up or full-light. The maximum power consumption is an essential factor for AC power supply (wire diameter, switch, etc.). The average power consumption is generally 1/3 of the maximum power consumption. LED light bar conversion power supply is very important, mainly divided into a constant current power supply, constant voltage power supply; AC220V input, DC12V output, DC24V output, DC36V output, DC48C output. A LED power supply can also be divided into the rainproof power supply, non-waterproof power supply, and waterproof power supply;
The display is a large-scale precision electronic device. For safe use and reliable operation, the AC220V power input terminal or the AC220V power input terminal of the computer connected to it must be grounded. The display conversion power supply is very important (LED switching power supply), AC220V input, DC5V output. There are also DC3.3V output, DC7.5V output, DC13.8V output; car display, power supply DC12V input, DC24 input…
Note: The AC220V power input ground of the computer is connected to the computer case.
The LED display needs to be cleaned before and after installation. This is a very important part to prevent the LED display from appearing unclear during the operation, mosaic phenomenon and color cast during black screen. After the display screen is in operation for a certain period of time, there will be dust and other debris that may be displayed, and the LED display screen will be cleaned and maintained regularly, which can prolong the service life of the LED display and improve the quality of the LED display. Therefore, the cleaning of the LED display is particularly important both before and after the screen is installed.
- Cleaning of semi-finished products of LED modules
When the LED module is only a semi-finished product without a kit, it needs to be cleaned with a special washing water. The LED module is stained with some washing water and then brushed with a brush to accelerate the dissolution of the rosin and the flux detachment. Remove dust and impurities.
- Cleaning after installation of LED electronic display
LED electronic display installation shows that dust and impurities will accumulate after a period of time. In order not to affect the display effect of the display, it is necessary to clean the surface of the LED display with clean water or detergent such as detergent or detergent. The surface that can be cleaned is cleaned, and care must be taken when cleaning. The cleaned water cannot be brought to the back of the LED module.
19. Considering the problem
For special requirements, outdoor displays must be
(1) Select an industrial-grade integrated circuit chip with a working temperature between -40 ° C and 80 ° C to prevent the LED display four-way chip from starting up when the winter temperature is too low;
(2) In order to ensure long-distance visibility under strong ambient light conditions, ultra-high brightness light-emitting four-way diodes must be used;
(3) The display medium adopts a new wide viewing angle tube with a wide viewing angle. The color of the four-way chip is pure and consistent, and the lifespan exceeds 100,000 hours. The outer packaging of the display medium is currently the most popular with a rectangular cylinder with a cover, a silicone seal, and no metallization; its appearance is exquisite and beautiful, durable and durable, with direct sunlight, dustproof, waterproof, high-temperature resistance, and short circuit protection. “Five defenses” features;
(4) The joint between the screen body and the screen body and the building must be strictly waterproof and leakproof; the screen body should have good drainage measures, and once the water accumulation occurs, it can be discharged smoothly;
(5) Install lightning protection devices on the display screen and buildings. The main body and the outer casing of the LED electronic display are well grounded, and the grounding resistance is less than 3 ohms so that the large current caused by lightning is discharged in time;
(6) Install the ventilation equipment to cool down, so that the internal temperature of the screen is between -10 °C and 40 °C. An axial fan is installed on the back of the screen to discharge heat and extend the life of the four-way LED display.
The main problems of the outdoor screen are as follows
(1) The ambient temperature varies greatly. When the full-color LED display is working, it must generate a certain amount of heat. If the ambient temperature is too high and the heat dissipation is poor, the integrated circuit may not work properly or even be burned, so that the display system cannot work normally;
(2) The audience is wide, the distance between the vision is long, the field of vision is wide, and the ambient light changes greatly, especially in direct sunlight;
(3) The display screen is installed outdoors, often with sun and rain, wind and dust cover, the environment is bad, the electronic equipment is wet or severely damp, which may cause the short circuit or even fire, causing malfunction or even fire, causing loss;
(4) The display may be subject to strong electric and magnetic attacks caused by lightning.
How to distinguish the quality of the LED screen
1: Flatness: The surface flatness of the LED display should be within ±1mm to ensure that the displayed image is not distorted. Local bumps or recesses may cause the viewing angle of the display to appear dead angle. The quality of flatness of car LED display manufacturers is mainly determined by the production process.
2: Brightness and viewing angle: the brightness of the indoor full-color screen should be 800-2000cd/m2, and the brightness of the outdoor full-color screen should be 5000-7500cd/m2 to ensure the normal operation of the display. Otherwise, the brightness will be too low or too High cannot see the image displayed. The brightness is primarily determined by the size of the LED die crystal. The size of the viewing angle directly determines the number of display audiences, so the larger the angle, the better. The size is mainly determined by the way the die is packaged.
3: White balance effect: White balance effect is one of the most important indicators of the display. In color science, when the ratio of red, green and blue primary colors is 1:4.6:0.16, pure white will be displayed. If the actual ratio has a slight deviation, there will be deviations in white balance, and it is generally necessary to pay attention to whether white is blue or yellowish. Car LED display manufacturers introduce the white balance is mainly determined by the display control system, the die also has an impact on the color reproduction.
4: There is no color block color difference: color block means that there is an obvious color difference between adjacent modules, the color transition is in module unit, and the color block phenomenon is mainly caused by a poor control system and low gray level, caused by a lower scan frequency.
5: Reducing color: The reproducibility of color refers to the reproduction of color on the display screen. The color displayed on the display screen should be consistent with the color of the source, so as to ensure the realism of the image.
6: Whether there is mosaic or dead point phenomenon: Mosaic refers to the effect of the uneven color of the unit module on the display screen, which is always bright or often black, and the module is necrotic. The main reason is the display screen. The quality of the connectors used is not good. The dead point refers to a single point that is always bright or often black on the display. The number of dead points is mainly determined by the quality of the die pixel.
The LED display industry has developed rapidly and has formed a new stage of development. It is divided into three phases:
1, LED display utility stage: LED display has environmental protection, high brightness, high definition, high reliability, and other characteristics gradually emerged, and in the previous stage, the LED display market just meets people’s needs, but in the LED display the screen products are not up to the requirements, but the quality is not enough.
With the development of LED displays, LED products have now made a new breakthrough. At least the progress is improved over the previous stage. It has also developed a series of products that are completely different from traditional light source applications. The LED display will have a larger and wider development space. An LED display is not only a beautification effect, its change makes it more relevant to people’s work and life. Nowadays, manufacturers have to fight for the advantages of designing applications and technology research and development.
2, LED display intelligent control stage: With the continuous development and development of LED display technology, LED as semiconductor industry, will also catch this high-speed train, play its high controllability. From home to office buildings, from roads to tunnels, from cars to walks, from indoors to outdoors, intelligently controlled LED display systems will provide a higher level of service to humans. The LED display industry will also go from making products to designing products to providing a total solution.
3, LED display replacement acceptance stage: Because the characteristics of LED display products are mainly reflected in high light efficiency (low energy consumption), long life characteristics of this stage is the initial stage of LED display development, so in terms of price, in the customer It seems that there is a certain comparison. Of course, the customer has an acceptance process, a transition, and acceptance of the customer’s habits and appearance. Let customers know the characteristics of LED display products, and choose a feature that saves electricity and longevity. This makes it easy for customers to accept its relatively high price, especially in commercial applications, not to mention the fact that today’s customers are second in price, mainly in terms of quality. Therefore, each manufacturer is now fighting for the price advantage. The display effect of the screen is higher. When the display refresh rate is insufficient, the scanning horizontal line will appear. It is necessary to improve the scanning output technology of the LED display control system so that the refresh rate of the LED display is higher than that of the general camera, eliminate the scanning horizontal line under the camera shooting.
In summary, LED display is in the stage of rapid development and growth. I believe that in the near future, LED display will be applied in more fields, and various LED displays will appear on the market. The new products of the screen bring consumers better, more convenient and more energy-saving LED display.
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