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Uniform LED backlight brightness control

   light emitting diode (LED) wide use in a variety of terminal equipment has long been amazed so many people: from car head lights, traffic signals, digital displays, advertising billboards, and existing technologies such as large displays, general lighting of the building, as well as other applications such as LCD backlight, LED light source makes the most of the growing prevalence of products must be redesigned. With the increasing efficiency and brightness, as well as costs continued to decline, LED eventually to replace traditional light sources a major source of lighting for consumer applications. This article will address the LCD LED backlight is compared with other large display of lighting technology, whereby the description LED application design needed to face the challenges.  

     image correction technology LED brightness difference  

     Gymnasium or usually contains dozens of groups with large billboards advertising display panels with thousands of LED. In each display zone, each LED (also known as pixel) issued by the difference in brightness is great; often the brightest and darkest LED the difference between 15% and 20%, which manufacturers must continue to address difficult issues such as quality and management. Although all LED would encounter such problems, but in a dynamic video display needs on the application of uniform brightness quality seems particularly serious. Manufacturers are taken to compensate for the brightness difference between the two methods, one approach is to buy from suppliers of similar brightness LED; other was adopted "image correction (dotcorrection)" high quality LED-driven components.  

     similar to the brightness of the LED has a number of advantages, their prices are usually higher. Dealer will first measurement of the brightness of the LED under the specific current and similar brightness red, green and blue light LED together. This approach can at least affect the design of the case for low level lighting system provides a uniform brightness; the downside is speed loss of brightness of each LED is different, so after some time the brightness will become uneven. This flaw makes it only as a short-term solution, or after one or two years later, the screen will turn into one. In addition, if a panel fails and needs to be replaced, the new Panel brightness differences can also occur with the original Panel.  

     for higher-order display brightness matching requirements are even more stringent, LED a similar brightness alone cannot meet the requirements of this type of application. In order to make pixel and Panel can display life cycle maintenance of uniform brightness, manufacturers will use a built-in image correction features advanced LED drive components. Like points amendment is through adjustment individual LED current to management pixel highlights of a method: processor just control sent to whole block LED displayed district of total current, again by LED drive component adjustment individual LED current to produced uniform brightness; this said processor can will its operation effectiveness for other work, and not needed to uniform brightness and query form or in each update cycle for each star LED for complex of multiplication operation. In order to provide image correction function, manufacturer, through the screen capture measure the brightness of each LED, still a benchmark system the dark LED LED, pixel brightness is then adjusted to and benchmarks LED the same adjustment is based on the current LED outputs brightness of each pixel to reduce certain proportion. Texas instruments (TI) TLC5940 or other similar components each LED point correction will be stored in the built-in EEPROM memory chip, or dynamic modifications during each update cycle. This double image correction method is very flexible, which can be updated when the external lighting conditions change the brightness of the Panel as a whole, and can also provide long-term preservation of image information is amended to ensure that the Panel brightness uniformity. As long as the pixel brightness changes over time, or needs to be adjusted because of the fault of the Panel and replacing, engineering staff can update the EEPROM data. We will use the following example to illustrate this approach.  

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