LED control system is usually composed of the main control box, scanning board and display control device composed of three parts: The main control box from the computer's graphics card to obtain a screen pixel brightness data, and then redistributed to a number of pieces of scanning board, each Block scanning board is responsible for controlling the LED screen on the number of rows (columns), and each row (column) on the LED display control signal is sent using a serial mode.Currently there are two kinds of serial transmission control signals: a Is to scan the board to control the gray level of each pixel, the scanning board will be from the control box of each pixel brightness value decomposition (ie, pulse width modulation), and then open the LED signal in the form of pulses (lit 1 , Not bright 0) according to the line by serial transmission to the corresponding LED, control whether it is lit. This method uses fewer devices, but the large amount of serial transmission of data, because in a repeatedly lit During the period, each pixel needs 16 pulses under 16 levels of gray scale and 256 pulses under 256 levels of gray level. Due to the limitation of the working frequency of the device, generally, the LED screen can only achieve 16 levels of gray level.
Another method is the scan board serial transmission is not the content of each LED switching signal but an 8-bit binary brightness value. Each LED has its own pulse width modulator to control the lighting time. Thus, at In a repetitive lighting cycle, each pixel requires only 4 pulses at 16 levels of grayscale and 8 pulses at 256 levels of grays, greatly reducing the serial transmission frequency. With this decentralized control LED Grayscale method can easily achieve 256 gray-scale control.