After the 1990 LED display began to enter a period of rapid development, the global information industry high speed growth, information technology in various fields constantly breakthrough, LED display in the LED material and control technology has new achievements. Blue chip LED developed, full color LED display screen to enter the market; computer and microelectronics technology development, browsing screen control technology appeared in the field of video control technology, display gray scale to achieve 16 gray and64 gray level adjusting ash, display the dynamic display effect is improved greatly. This stage, LED display in China's development speed very quickly, from the first 2 empty company, annual output value of tens of millions of yuan to the development of dozens of enterprises, annual production value of several hundred million yuan, product applications involving finance, sports, airport, railway station, highway, traffic, commercial advertising, posts and telecommunications as well as other fields, in particular in 1993 is the stock industry development caused the LED display market occurrence. LED display in the field of flat panel display mainstream product situation is formed basically, the LED display screen industry become the new high-tech industry.
The LED control system usually created main control box, to scan the board and display control device of three parts. The particular control box around the computer's display card get a screen pixel colors and brightness data, then reassigned to a plurality of scan board, each scan board is liable for the control of this LED screen rows ( columns), and each and every row ( column) on the LED display control signal is used for serial transmission. Several currently two serial transfer display control signal.
1) is a scanning board centralized control of all pixels gray, to scan the board will come against the control box belonging to the rows of pixels brightness value decomposition (i.e., pulse width modulation ), then LED enlightened signal with pulse form ( light1bright,0) with serial transmission to your corresponding LED, control the light. In this manner the use of devices is less, but the serial transmission data amount is large, just like a repetitive light cycle, each pixel in the next 16 gray-scale16pulse, within the next 256 gray-scale256pulse, the device working frequency limit, generally only the LED screen to16 gray.
2) another approach is to scan the board serial transmission is not the content of each LED switch signal but a8 bit binary brightness value. Each LED has a pulse width modulator to control the lighting time. So, in a repetitive light cycle, each pixel point next 16 gray-scale only need4 pulses,256 gray level of just under8 pulse, greatly reduces the serial transmission frequency. The decentralized control gray LED method could achieve256 gray scale control.
General LED large screen will flicker frequency to, due to, LED itself does not have lasting effect characteristic, so the traditional constant current source pulse width modulation control gray LED screen refresh rate must be as compared to 120Hz to achieve flicker-free image computer screen. This requires the gray-scale data low lose eight frame image signal frequency increasing refresh, refresh data the result appeared great redundancy, increased LED driver board hardware.New from http://www.aoyiteled.net/ candle bulb