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What is the relationship between LED display gray scale and brightness?

Jul. 25, 2019

What is the relationship between LED display gray scale and brightness? The high brightness computer Monitor supplier would like to share with us.

LED grayscale can also be called LED brightness. Gray level is also known as half-tone, mainly used to transfer pictures, there are 16, 32, 64 levels of three ways, it USES matrix processing of the file pixels into 16, 32, 64 levels, so that the transfer of pictures more clearly. Whether it is monochrome, two-color or three-color screen, to display images or animation, it is necessary to adjust the gray scale of each LED that constitutes the pixel, and the fine degree of adjustment is what we usually call the gray level.

There are two ways to control the grayscale of high brightness computer Monitor: changing the current flowing through them, and pulse-width modulation. 1. Change the current flowing through the LED. Generally, the continuous working current of LED tube is about 20 ma. Except for red LED with saturation phenomenon, other LED gray scale is basically proportional to the current flowing through. Another method is to make use of the visual inertia of human eyes and use pulse width modulation method to achieve grayscale control, that is, periodically change the light pulse width (that is, duty ratio), as long as the cycle of repeated lighting is short enough (that is, the refresh frequency is high enough), the human eyes will not feel the luminous pixels shaking. Since pulse width modulation (PWM) is more suitable for digital control, almost all LED screens use PWM to control the grayscale when microcomputer is commonly used to provide LED display content. LED control system is usually composed of main control box, scanning board and display control device.

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The main control box obtains the colored brightness data of a screen pixel from the computer display card, and then redistributes it to a number of scanning boards. Each scanning board is responsible for controlling a number of rows (columns) on the LED screen, and the display control signals of the LED on each row (column) are transmitted in a serial way.

There are currently two ways of serial transmission of display control signals:

1. One is to centrally control the grayscale of each pixel point on the scanning board. The scanning board will decompose the grayscale value of each pixel from the control box (namely pulse width modulation), and then transmit the opening signal of each LED in the form of pulse (lit as 1, not lit as 0) in a serial mode to the corresponding LED in line to control whether it is lit or not. This method USES few devices, but the amount of data transmitted in serial is large, because each pixel needs 16 pulses at the level of 16 gray scale and 256 pulses at the level of 256 gray scale within a cycle of repeated lighting. Due to the limitation of the operating frequency of devices, it is generally only possible to make the LED screen achieve the level of 16 gray scale.

2. One is pulse width modulation. Scanning board serial transmission of the content is not each LED switch signal but an 8-bit binary gray value. Each LED has its own pulse width modulator to control the lighting time. In this way, in a cycle of repeated lighting, only 4 pulses are needed for each pixel point at level 16 gray scale, and only 8 pulses are needed at level 256 gray scale, greatly reducing the serial transmission frequency. With this method of decentralized control of LED grayscale, 256 levels of grayscale control can be easily achieved.

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