LED large screen brightness control method
There are two ways to control LED brightness. One is to change the current flowing through the LED. Generally, the LED tube allows a continuous working current of about 20 mA. Except for the saturation phenomenon of the red LED, the brightness of other LEDs is basically proportional to the current flowing; another method is to use The visual inertia of the human eye uses pulse width modulation to achieve grayscale control, which is to periodically change the light pulse width (that is, the duty cycle), as long as the period of repeated lighting is short enough (that is, the refresh frequency is high enough), human The eye can't feel the light-emitting pixels shaking. Because pulse width modulation is more suitable for digital control, so today, microcomputers are commonly used to provide LED display content, and almost all LED screens use pulse width modulation to control gray scale.
The control system of LED usually consists of three parts: main control box, scanning board and display control device. The main control box obtains the brightness information of each color of one screen pixel from the display card of the computer, and then redistributes it to several scanning boards. Each scanning board is responsible for controlling several rows (columns) on the LED screen, and each row (column) The display and control signals of the upper LED are transmitted in tandem. At present, there are two ways of transmitting display control signals in series: one is to control the grayscale of each pixel point on the scanning board, and the scanning board decomposes the brightness value of each row of pixels from the control box (that is, pulse width modulation), Then, the turn-on signals of the LEDs in each row are transmitted to the corresponding LEDs in the form of pulses (lighting is 1 and not lighting is 0) in rows and columns to control whether they are lit. This method uses fewer devices, but the amount of data transmitted in series is large, because in a repeated lighting cycle, each pixel requires 16 pulses at 16 gray levels and 256 gray levels 256 pulses, due to the limitation of the device operating frequency, generally only the LED screen can achieve 16 levels of gray.
Another method is that the content of the serial transmission of the scanning board is not the switching signal of each LED but an 8-bit binary brightness value. Each LED has its own pulse width modulator to control the lighting time. In this way, in a period of repeated lighting, each pixel point only needs 4 pulses in 16-level grayscale and only 8 pulses in 256-level grayscale, which greatly reduces the serial transmission frequency. With this method of discretely controlling the grayscale of LEDs, 256-level grayscale control can be easily achieved.
In terms of display effect, the advantages of OLED screens are too attractive compared to LCD screens. The OLED screen has the function of individually controlling the pixels. In daily use, not every scene needs to light up all the pixels of the screen. Therefore, it can display a more pure black effect, and can also achieve 1000000:1 in terms of contrast ratio, so that the bright places are bright enough, and the dark places are very dark, bringing a more realistic display effect.
In addition, compared with LCD screens, OLED screens have removed components such as backlights and polarizers. In terms of sliding and touch, OLED screens can provide a touch response speed of 0.2ms, and dynamic content such as content sliding and games. In the scene, the OLED screen can provide a clearer look and feel.
It is precisely because of this that more and more notebook manufacturers are beginning to deploy and promote OLED screens on their own products to further improve the display effect of their own products. Among the notebook computer manufacturers, ASUS is the most active. The slogan of #ASUSscreen# has been played before, and with the help of high-quality OLED screens, it brings a more amazing display effect than LCD. The recently launched new product, the ASUS Unparalleled series, has brought the 120Hz high-brush OLED screen to the 5K price range, reducing the dimension of products at the same price.
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