LED full color display display principle and signal trend
As a new type of information display media developed rapidly in the world in the late 1980s, LED display screen uses dot matrix modules or pixels composed of light-emitting diodes to form a large-area display screen. With the characteristics of high performance ratio and low cost of use, it has rapidly grown into the mainstream product of flat panel display in just ten years, and has been widely used in the field of information display. So what is the working principle of LED display?
If you want to understand the working principle of the LED display, you must first figure out the various signal directions of the LED display. There are mainly 5 kinds of signals in the LED display. These 5 kinds of signals must be coordinated to complete the data transmission to complete the display The display works. This article will introduce the role of five kinds of signals.
The LED display screen is composed of three parts: data acquisition system, control system, and display system. The direction of the data signal is: peripherals – computer – DVI graphics card – data sending card – data receiving card – HUB adapter board – display screen.
The actual situation is that the HUB adapter board is used as the last link of data transmission, and all signals can be found on the HUB adapter board. The HUB adapter board is a card board that divides the signal sent by the control board into several tributaries, also called a breakout board. Under normal circumstances, it is determined according to the vertical number of modules of the LED electronic screen itself.
The various signals contained in the display. The signal starts from the HUB board and is connected to the unit board or module through the cable to complete the data transmission. Except for the data signal, which is transmitted serially, all other signals are transmitted in parallel. Now the various signal effects are analyzed as follows:
(1) CLK clock signal: The shift pulse provided to the shift register, each pulse will cause data to be shifted in or out one bit. The data on the data port must be coordinated with the clock signal to transmit data normally, and the frequency of the data signal must be 1/2 times the frequency of the clock signal. In any case, when the clock signal is abnormal, it will make the whole board display chaotic.
(2) STB latch signal: When one channel of data transmission is completed, the STB latch signal is valid, latches the data in the shift register, and displays the data content through the drive circuit to light up the LED. However, since the drive circuit is controlled by the EN enable signal, the premise of its lighting must be the enable state. The latch signal also needs to be coordinated with the clock signal to display a complete image. In any case, when the latch signal is abnormal, it will make the whole board display chaotic.
(3) EN enable signal: the whole screen brightness control signal, also used for display screen blanking. Just adjust its duty cycle to control the change in brightness. When the enable signal is abnormal, the whole screen will appear dark, dark or trailing.
(4) Color data signal: Provide the data needed to display the image. It must be coordinated with the clock signal to transmit data to any one of the display points. Generally, the data signals of red, green and blue are separated in the display screen. If a data signal is short-circuited to the positive or negative pole, the corresponding color will appear full on or off. When the data signal is suspended, the corresponding color will be displayed. The situation is uncertain.
(5) ABCD line signal: it only exists during dynamic scanning display. ABCD is actually a binary number, and A is the lowest bit. If the ABCD signal is expressed in binary, the maximum control range is 16 lines (0000-1111), 1/4 scanning. As long as the AB signal is fine, because the representation range of the AB signal is 4 lines (00-11). When the line control signal is abnormal, there will be display dislocation, highlight or image overlap.