LED display function is how
I. What is LED?
In some semiconductor materials, PN junction, the injection of minority carrier and majority carrier recombination extra time to time to the form of light energy released, which convert light energy directlMonitor
y into electrical energy. PN junction reverse voltage, minority carrier injection is difficult, it is not light. This use of principle of injection electroluminescence diodes called LEDs produced, known as LED.
LED luminous color and light-emitting efficiency and production of LED materials and processes related to the widely used red, green, and blue. As the LED voltage is low (only 1.5-3V), can take the initiative to have a certain luminescence and brightness, Brightness and voltage (or current) regulation, which itself has impact-resistant, anti-vibration, long life (100,000 hours), so in large display device, the display is currently no other way match with LED display.
The red and green LED together produced as a pixel color display screen or a color screen name; the red, green
LCD Panel
and blue LED tube put together as a three-color pixel of the display screen or call Full color. Production of indoor LED screen pixel size is generally 2-10 mm, often used to produce several different color of the LED die into one package, outdoor LED screen pixel size mostly 12-26 mm, each pixel by a number of various color LED, the finished tube, said pixel, two-color pixel 3 red tube generally composed of two green, three-color pixel 2 red 1 green tube with a blue component.
Whether using LED production monochrome, color or tri-color screen pixels to display images need to form the luminance of each LED must be able to adjust the fine adjustment of the degree is the gray scale. The higher the gray level, the more exquisite display of images, color and the more abundant, and the corresponding display control system is also more complex. General 256 gray scale images, color transition has been very soft, while the 16-level grayscale color image, color transition boundaries clear. Therefore, the current color LED screen all requests made of 256 gray scale.
2, LED brightness control method:
There are two methods of controlling LED brightness. One is to change the current flowing through the LED, LED tube to allow the general current of 20 mA continuous work around, in addition to the red LED with saturation, the other LED brightness is basically proportional to the current flowing through; Another way is to use human visual inertia with a pulse width modulation method to achieve gray scale control, which is cyclical changes in pulse width (ie duty cycle), as long as the repeated cycle of light short enough ,LCD(ie the refresh rate high enough), who eye is not feel the trembling of light-emitting pixels. As the pulse width modulation is more suitable for digital control, so in general the use of computer to provide the LED display today, almost all of the LED screen is used to control the pulse width modulated gray levels.
LED control system is usually the master box, scan control unit board and was composed of three parts. Main control box from the computer's graphics card to get a colored screen pixel luminance data, then re-allocated to a number of block scanning plate, each scan control board LED screen for a number of rows (columns), and each row (column) on the LED control signal is an outstanding way to use serial transmission. There are two serial transmission mode display control signals: one is the centralized control panel scan pixel grayscale, scan board will come from the control box of each line of pixel brightness value decomposition (ie, pulse width modulation), then the opening of the line LED signals in pulses (light 1, light = 0) transmitted by serial line to the corresponding LED on the control whether they light up. This use of the device small, but the serial transmission of data volume, because in a repeating cycle of light, each pixel gray level in the 16 required under 16 pulses required under the 256 gray 256 pulses, as the device operating frequency limit, the general can only do 16-level grayscale LED screen.
Another method is to scan the contents of the plate serial transmission is not a signal for each LED in the switch but the brightness of an 8-bit binary value. Each LED has its own pulse width modulator to control the light time. Thus, in a repeating cycle of light, each pixel in 16 gray scales are required, four pulses, 256 only eight pulses under the gray, greatly reduce the serial transmission frequency. LED intensity with this method of decentralized control can be easily controlled with 256 gray scales.
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· LED display general specification
* The basic structure of graphics display
* The basic structure of the video LED display
· LED display screen performance comparison with other
* Indoor LED electronic display main technical parameters
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