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

LED grayscale can also be called LED brightness. Gray scale is also called Half-tone, which is mainly used to transfer pictures. There are 16 levels, 32 levels and 64 levels respectively. It adopts matrix processing to process the pixels of files to level 16, 32 and 64. Levels make the transmitted images clearer. Whether it is a monochrome, two-color, or three-color full-color display, the brightness of each LED constituting a pixel needs to be adjusted to display an image or an animation. The degree of fineness of its adjustment is what we commonly call gray scale.

There are two ways to control the gray level of the LED: one is to change the current that flows, and the other is pulse width modulation.

Change the current flowing through the LED. The general LED tube allows the continuous operating current to be around 20 milliamperes. In addition to the saturation of the red LED, other gray levels are basically proportional to the current flowing through it;

Another method is to use the visual inertia of the human eye to achieve gray control with a pulse width modulation method, that is, to periodically change the light pulse width (ie, duty cycle) as long as the period of this repeated lighting is short enough (ie, refresh The frequency is high enough that the human eye cannot feel the jitter of the pixels.

Because pulse width modulation is more suitable for digital control, today, microcomputers are generally used to provide LED display content. Almost all LED screens use pulse width modulation to control the gray level. LED control system usually consists of three main parts: main control box, scan board and display and control device.

The main control box obtains the brightness data of each color of the pixels of one screen from the display card of the computer, and then re-assigns them to several scanning boards. Each scanning board is responsible for controlling several rows (columns) on the LED screen, and each row (column) is LED display control signal is transmitted in a serial manner.

There are currently two ways of serially transmitting the display control signal:

1) One is the centralized control of the grayscale of each pixel on the scanning board.

The scanning board decomposes the gray values ​​of the pixels in each row from the control box (that is, pulse width modulation), and then turns on the LED of each row in the form of pulses (lighting 1 and not lighting 0). To the corresponding LED, control whether it is lit. This method uses fewer devices, but the serially transmitted data is larger because each pixel requires 16 pulses at 16 gray levels and 256 gray levels at 256 gray levels during a repetitive lighting cycle. Pulses, due to device operating frequency limitations, generally only allow the LED screen to achieve 16 gray levels.

2) One is pulse width modulation.

The content of the serial transmission of the scan board is not the switching signal of each LED 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 repetitively lit period, each pixel needs only 4 pulses under 16 gray levels, and only 8 pulses under 256 gray levels, which greatly reduces the serial transmission frequency. Using this method of decentralized control of LED grayscale can easily achieve 256 grayscale control.