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 technologies have new achievements. Blue chip LED developed, full color LED display screen enter in the market; computer and microelectronics technology development, azure 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 into the development of dozens of enterprises, annual production associated with several hundred million yuan, product applications involving finance, sports, airport, railway station, highway, traffic, commercial advertising, posts and telecommunications because fields, in particular in 1993 is the stock industry development caused the LED display market regrowth. LED display in the field of flat panel display mainstream product situation is formed basically, the LED video display industry become the new high-tech industry.
The LED control system usually consists of a principal control box, to scan the board and display control device of three parts. The main control box from 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 responsible for that control of the LED screen rows ( columns), and each row ( column) on the LED display control signal is employed for serial transmission. There are currently two serial transfer display control signal.
1) is a scanning board centralized control of all pixels gray, to scan the board will result from the control box of this rows of pixels brightness value decomposition (i.e., pulse width modulation ), the particular LED enlightened signal with pulse form ( light1bright,0) by using serial transmission to the corresponding LED, control the light. Like that the use of devices is less, but the serial transmission data amount is large, as in a repetitive light cycle, each pixel in the next 16 gray-scale16pulse, in your next 256 gray-scale256pulse, the device working frequency limit, generally only the LED screen to16 gray.
2) another method for you 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 part of the 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 can easily 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 greater than 120Hz to achieve flicker-free image display. This necessitates 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