Weak current College】 【how to buy a good led display.

<br> With the application of led display, led display and universal access to the market an unprecedented trend of rapid development. This years LED large screen demand soared, causing various size factory mushrooms grow, suddenly all say their own good, the bad and .the ugly customer difficile, but most of them price-oriented. But as the saying goes, buyers than sellers, generally means the buyer how to go down, go to the astute requires sellers, but also difficult to smart too sellers, let the sellers .account. The result is like a million of BMW didn't buy it bought 300 Jetta. <br> However, as a member of the integrity of the manufacturer, you should put the industry's important information prior to tell buyers for their choice not to .pursue the information asymmetry. <br> LED full color large screen after several years of development, rough look seems to have a mature industry, as a matter of fact, whether domestic or foreign manufacturers, is still a long way to go, especially outdoor .large screen, most of the products after two years of operation, it is difficult to maintain within the user's expectations. <br> Why is that? <br> Here first of all a big misunderstanding, most people think that the main materials LED screen ., IC life has reached 10 000 hours, 365 days / year, 24 hours / day running, the service life of 11 years, most customers are concerned only with the renowned LED and IC. In fact, this thing is a necessary but not sufficient .condition, because the red, green, blue three lamp of fair use, to display all the more important, for the different colors of light, to make it work in the best condition, for a good display will become more important. IC's reasonable control ., also help to overcome the PCB wiring problems are not reasonable. Just like a car with a good engine and circuit control, not necessarily become a good car. This is a critical factor is this: <br> Because of the LED, IC is .a semiconductor device, their conditions of use on the environment, preferably in the required room temperature of around 25 ° c, its the best working mechanism. But in fact a outdoor large screen are applied at different temperatures, summer may be in more than 60 .℃, winter may at-20 ° c below. When manufacturers product is 25 ¡ .æ to test conditions, the different product categories, fact tranche running condition of 60 ° c or-20 ° c, then LED, IC work efficiency and performance are not consistent, you may actually belong to a stall of becomes more stalls, brightness is .inconsistent, the screen body naturally become flowers. This is because in different temperature conditions, red, green and blue light attenuation and decline of brightness are different, and in 25 ℃, the white balance is good, but at 60 ° c, the three .colors of the LED brightness is decreased, and the attenuation values do not match, it will produce a screen brightness decrease and partial color, full of quality will decrease. And IC? IC temperature range is-40 ° c-85 ℃. As the .outside temperature is too high, causing the body temperature rises, if the box at the temperature exceeds 85 ° c, IC will cause overheating and result in instability, or drift to difference between current or movie channel difference too large to cause corruption. <br .> At the same time, power is also very important, because the power supply in different temperature conditions, the stability of its work, the output voltage and load capacities vary, because it assumes the role of logistics support, so it guarantees the ability to .directly affect the quality of the screen. <br> Cabinet design for display is also very important, on the one hand, the role of circuit protection, on the other hand is safe effect, dustproof, waterproof effect. But more importantly ventilation heat circuit .system design is good, with the power-on time and outside temperature, thermal drift of components will also increase, which causes the image quality deterioration. <br> <br> Five factors determine the quality of LED display screen <br> <br .> LED (light emitting diode) on the importance of the display can be compared to the car's engine, the air conditioning compressor. Choose a good performance of the LED is a high-performance led display. However, even if the same ingredients, the .same ingredients, the same stove, different levels of Chef may also vary dishes out of cooking. Therefore, the possibility of using LED more is the touchstone for the display manufacturer. General view screen has the following five key performance indicators and LED is closely related .to quality parameters: brightness and viewing angle, uniformity and clarity, pixel out rate, life expectancy, energy consumption and energy efficiency. <br> 1. the brightness and viewing angle <br>-Display brightness depends primarily on the LED luminous intensity and .the LED density <br>-Display perspective should address the luminous flux waste problem <br> Display brightness depends primarily on the LED luminous intensity and the LED density. In recent years, LED in the substrate, extension, chip and package, an endless .stream of new technology, particularly of indium tin oxide (ITO) current extension layer technology and process stability and maturity, the LED luminous intensity has been significantly improved. At present, the international first-class brand low power LED on the horizontal angle of view .for 110 °, vertical angle of 50 degrees of luminous intensity of the Green tube is high as 4000mcd, red tube da 1500mcd, blue tube da 1000mcd. The spacing in pixels to 20mm, the brightness can be reached more than 10000nit. The display can .be used in any environment 24 / 7. <br> On the display screen angle, one worthy of our consideration of phenomena: led display particularly outdoor screen, people's observation angle under which basic is from, and to existing led display product form, half .of the light flux disappear in the vast sky. In energy intensive today, do we have the more reasonable solution? worth thinking about. <br> 2. uniformity and clarity <br> Various performance parameters. LED inconsistent is the main cause of the .effect uniformity <br> The definition restricting led display-improvement was uniformity and not physical pixels of spacing <br> Led display technology development today, uniformity has become the measure of the most important advantages and disadvantages of the display. People often say "little .bright LED display, all the brilliant "the pixels and the serious imbalance between modulesThe image of a metaphor. Professional point of argument as" dust effect "and the" mosaic phenomenon ". <br> Cause cause uneven: LED various performance parameters; display .in production, the installation process of assembling accuracy; other electronic components of the electrical parameters of consistency is not enough; modules, PCB design of norms. <br> "LED various performance parameters of the inconsistency" is the major cause. These performance parameters .of inconsistent mainly include: light intensity is not consistent, smooth inconsistencies, color coordinates inconsistencies, the primary colors of light intensity distribution curve of the attenuation characteristics are not consistent and inconsistent, and so on. How to resolve LED performance parameters of inconsistency, current .industry there are two main ways: first, the technology by LED specifications of further subdivision, improve the performance of LED consistency; the second is through subsequent correction of the ways to improve display uniformity. Subsequent correction or rectification from the earlier module, modules, .correction, to the development of point-by-point correction today. Correction technique is from a simple light intensity correction, to the light intensity + color coordinate calibration. <br> However, we think that the subsequent correction is not a panacea. Which .is inconsistent with the optical axis, the light intensity distribution curve of the attenuation characteristics are not consistent and inconsistent, assembling accuracy as well as the design of norms is not available through subsequent correction to eliminate, even such subsequent correction makes the optical axis, attenuation ., assembling precision inconsistency. <br> Therefore, through the practice of our conclusion is: subsequent correction just treatment table, while the LED is the fundamental parameters of segmentation is the led display industry in the future. <br> Speaking to display uniformity and .clarity of the relationship, the industry is often a misunderstanding of understanding, namely to resolution alternative definition. In fact, the display resolution is the human eye on screen resolution, uniformity (SNR), brightness, contrast, and so many factors of subjective experience .. Simply reduce the physical pixel pitch increase resolution, to the neglect of uniformity, to improve the sharpness is without a doubt. Imagine a serious "dust effect" and the "mosaic phenomenon" screen, even if it's a physical pixel pitch and then small ., high resolution and then, nor is it possible to get a good image clarity. <br> Therefore, in a sense, the present constraints led screen sharpness improvement was "uniformity" instead of "physical pixel pitch". <br> 3. .display pixel out of control <br>. Display pixel out mainly LED fail <br>-Electrostatic discharge is the biggest incentive for failure <br> Result display pixel out for various reasons, the most important reason is that the "failure" LED. .<br> The main LED failure can be divided into two areas: one is the quality LED itself; the second is the use of improper methods. By analyzing our conclusion LED failure modes and the two main correspondence between. <br> Above we talked .about a lot of failure usually LED to LEDs general inspection tests cannot be found. In addition, at the electrostatic discharge, high current (junction temperature caused by too high), the improper use of an external force, etc, many LED failure is in .the high temperature, low temperature, the rapid pace of change in temperature or other adverse conditions, due to the LED chip, epoxy resin, bracket, leader, solid Crystal glue, PPA Cup etc materials thermal expansion coefficient of variation, raises its internal stress .in different, therefore, LED the quality inspection is a very complex work. <br> These factors are interrelated and that will affect the display of quality and longevity. Customers in the selection screen, but also a comprehensive study, to make the right judgement .. <br> Effect of temperature on the large screen still further, assume that the customer purchased a 6 m wide and 10 m high (60 m2) with large screen, while the total area is not large, but the internal composition of the unit ., the unit of temperature between the boxes are not necessarily proportional to the temperature inside the box will also be affected by the impact of air convection temperature not consistent, causes the cell box or cell body temperature, brings the productivity of semiconductor devices, which reflected .the glow brightness LED lamp, look for "flower" screen. <br> <br> Furthermore, for purposes of GaN-based LED, electrostatic discharge is the largest of its failure. Electrostatic discharge led LED failure mechanism is complex, equipment, tools ., containers and the human body are possible with electrostatic and electrostatic discharge, this at least several hundred volts, the tens of thousands of volts, the discharge time in the nanosecond level. We display production, installation, use the blue green tube failure, often .LED-PN knot was to electrostatic discharge breakdown. International Association of strictly defines the static electricity standard electrostatic discharge mode, mainly divided into human body model (HBM) discharge and machine model (MM) discharge. Our devices for electrostatic discharge sensitivity (ESDS) .is divided into three levels (human body model): 1-level 0 ~ 1999V; level 2 to 2000 ~ 3999V; level 3 above for 4000V. Normally LED by electrostatic discharge sensitivity in human mode in several hundred volts ~ tens of thousands of volts .and in machine mode only several dozen volts to around 500 volts. LED display screen as a production complex, difficult, electrostatic discharge, LED <br> <br> Electrostatic discharge sensitivity should choose level 2 or above is completed (human body model), .and electrostatic protection must run through the whole production process. <br> <br> 4. life <br>. LED life determines the display's life <br> From the device manufacturer, and device applications to improve both LED life <br> Led .display monitor's life is determined by many factors, however, many factors contribute to the end of life is that you can spare parts (such as switching power supply) for replaceable to continually extend life. While the LED is not likely to be a replacement, .so that once LED life comes to an end, it means that the display of the termination of life. Certain sense LED lifetime determines the life of the display. LED life usually in luminous intensity attenuation to initial value of 50% of the time period for .life. LED as a semiconductor material, it is often said that 10 million hours of life, but that is under ideal conditions. But in the actual usageThe following is not. We have a simple test method and calculation formula can calculate the life of the .LED: the LED is placed in the actual working environment under the same conditions, and 1000 hours of work of the measured light intensity of initial and final values, then the formula will be launched in the life of the LED. We selected some famous brand .blue pipes in ambient temperature to 50 ° c, current 20mA environment 1000 hour measured after the final value is the initial value, according to 0.88 × formula we can figure out the blue tube in this environment of life-5422 hours. <br> We .say that LED the life of life decided to display, but is not to say that LED life equal to the life of the display. Due to display screen work not only LED every day work at full load, display in normal play video programs, the .display's lifetime should be LED lifetime of 6 ~ 10 times when working in low-current LED of life can be even longer. Therefore, the choice of the brand LED display lifetime up to 5 000 hours or so. <br> How to make LED .lifetime longer? under normal circumstances we can from the device manufacturer and device applications on both hands. Terms from the device manufacturing: select high-quality epitaxial materials; increase the chip area, reduce the current density; balanced current density; reduces thermal resistance; .choice of good performance and anti-UV ability strong packaging materials can make the LED for longer life. <br> Terms from the device applications: thermal design as from the module to the project or even a future system maintenance; lower Centre LED current; .properly configured, the base color LED LED synchronization attenuation are can extend the service life of LED. <br> <br> 5. energy consumption and energy efficiency <br>. The led luminous efficiency, reduce energy consumption is the development direction of the .display <br>. LED as a green, energy-saving light sources increasingly favor <br> Improve the led luminous efficiency, reduce energy consumption is a led screen display technology an important direction of development, it has the following positive significance: first energy .saving, emission reduction, protection of the environment; the second is to reduce power and capacity, power equipment and cooling device inputs; 3 save electricity bill reduction of operational costs; fourth, the lower the temperature display; the fifth is slowing the speed LED .attenuation; VI is to improve the system reliability; seven was to extend the life of the display; 8 is to reduce screen-parameters of drift, stable image effects. <br> Led luminous efficiency (ie external quantum efficiency) is LED in quantum .efficiency and escape rate decision. Today, LED by internal quantum efficiency is as high as 90 percent, but due to the low escape rate, so external quantum efficiency become bottlenecks to improve led luminous efficiency. In order to break through the bottleneck of restricting the .development of the industry, many innovative solutions are proposed, at the same time has the theoretical verification, most of which have entered the pilot phase, some have been successful, and ultimately of industrialization has laid a solid foundation. <br> LED as a .green, energy-saving light sources for people of all ages, as a mainstream media, the leading display technology of the future. <br> In short, the device manufacturing and device application itself is a complementary opposites, devices and technological progress has brought .to market and application market prosperity needs is the device technology and progress of the eternal power. Let us work together on downstream businesses, open up a new LED display technology for the future. <br> <br>.