As a new type of information display media that has developed rapidly around the world in the late 1980s, LED display screens use dot matrix modules or pixels composed of light-emitting diodes to form a large-area display screen with high reliability, long service life, strong environmental adaptability, and price With the characteristics of high performance ratio and low cost of use, it has rapidly grown into the mainstream flat panel display product in the past ten years and has been widely used in the field of information display. So what is the working principle of LED display?
To understand the working principle of the LED display, you must first figure out the various signal trends of the LED display. There are mainly 5 types of signals in the LED display. These 5 signals must be coordinated to complete the data transmission to complete the display. The display works. This article will introduce the functions of 5 kinds of signals respectively.
The LED display screen is composed of three parts: a data acquisition system, a control system, and a display system. The direction of the data signal is: Peripheral-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 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 from the control board into several branches, also called a splitter board. Under normal circumstances, it is determined according to the longitudinal number 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 flat cable to complete the data transmission. Except for the serial transmission of data signals, all other signals are transmitted in parallel. Now analyze the effects of various signals as follows:
(1) CLK clock signal: the shift pulse provided to the shift register, each pulse will cause the data to move in or out of 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 disorderly.
(2) STB latch signal: When the data transmission of one channel is completed, the STB latch signal is valid, and the data in the shift register is latched, and the data content is displayed through the drive circuit to light up the LED. However, since the drive circuit is controlled by the EN enable signal, the precondition for its lighting must be that the enable is turned on. The latch signal also needs to be coordinated with the clock signal to display a complete image. In any case, when there is an abnormality in the latched signal, the entire board will be displayed in a disorderly manner.
(3) EN enable signal: the entire screen brightness control signal, also used for display blanking. Just adjust its duty cycle to control the change of brightness. When the enable signal is abnormal, the entire screen will appear dark, dark, or tailing.
(4) Color data signal: Provide the data needed to display the image. It must be coordinated with the clock signal to transmit the data to any display point. Generally, the red, green and blue data signals 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 or not bright. 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 scan 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 is in progress As long as the AB signal is fine, because the AB signal range is 4 lines (00-11). When the line control signal is abnormal, there will be display misalignment, highlighting or image overlap, etc.
