What Is the Relationship Between LED Screen Display Gray and Brightness?
The LED grayscale can also be called LED brightness. The gray level is also called Half-tone, which is mainly used to transmit pictures, including 16, 32, and 64 levels respectively. It uses the matrix processing method to process the pixels of the file into 16, 32 and 64 levels, making the pictures more clear. Whether it is monochrome, double color, and tri - color screen, the image or animation needs to be adjusted to each of the LED luminescent grayscales that constitute the pixel. The fine degree of adjustment is what we usually call the gray level.
There are two ways to control the grayscale of LED: one is to change the current flowing, the other is pulse width modulation. 1. change the current flowing through the LED. The general LED tube allows the continuous working current to be around 20 mA. In addition to the saturation phenomenon of red LED, the other LED grayscale is basically proportional to the current flowing through. The other method is to use the visual inertia of the human eye to use the pulse width modulation method to realize the gray level control, which is the periodic change of the width of the light pulse (the duty ratio). This cycle of repeated lighting is short enough, that is, the refresh rate is high enough. Since PWM is more suitable for digital control, in today's general use of microcomputers to provide LED display, almost all LED screens use PWM to control grayscale. The control system of LED is usually composed of three parts: main control box, scanning board and display control device.
The main control box gets a pixel of each color of brightness data from the display card of the computer and redistribues it to a number of scan boards. Each scan board is responsible for controlling a number of lines on the LED screen, and the LED display signal on each row (column) is transmitted in a serial manner.
There are two ways to transmit the display control signal in serial mode.
The 1. one is to centrally control the gray level of each pixel on the scanning board. The scanning board decomposes the gray value of each row pixel of the control box (pulse width modulation), and then transfers the open signal of each row of LED to the corresponding LED in the form of pulse (light is 1, not bright 0), and controls it to light. This method uses less devices, but the amount of data is large in serial transmission because each pixel needs 16 pulses in the 16 level gray level and 256 pulses under the 256 level gray level in a repeated light cycle. The LED screen is generally only 16 gradations because of the limited working frequency of the device.
The 2. one is pulse width modulation. The serial transmission of scanned boards is not a switch signal for each LED, but a 8 bit binary gray value. Each LED has its own pulse width modulator to control the lighting time. In this way, only 4 pulses are needed for each pixel in the 16 level gray level, and only 8 pulses are required under the 256 level gray level. The serial transmission frequency is greatly reduced. The 256 level gray level control can be easily realized by using this method of decentralized LED grayscale control.