How does the LED display panel work?

Dec 27, 2022, 5:58:17 AM

Basic principle of LED display

LED (Light Emitting Diode) is taken as the basic light emitting element (pixel) to control the brightness and extinction of each pixel or its brightness and darkness through the control circuit and drive circuit, so that the display screen with relevant pixel can display various information required by people.


How does the LED display panel work?

The basic working principle of LED display is dynamic scanning. Dynamic scanning can be divided into line scanning and column scanning, in which line scanning is more common. Line scanning is divided into 8 line scanning and 16 line scanning.

In the line scanning mode, each LED dot matrix chip has a group of column drive circuits, and the column drive circuit also has a latch or shift register to lock the font data of the content to be displayed. In the line scanning mode, the same row control pins of the same row of LED dot matrix chips are connected in parallel to one line, a total of 8 lines, and finally connected to a row drive circuit; There must also be a latch or shift register in the line drive circuit to latch the line scan signal.

The driving circuit of LED display screen is generally controlled by single chip microcomputer, among which 51 series is the most common. The displayed content is usually stored in the external data memory of the microcontroller in the form of a font.

The process of controlling LED display screen by single chip microcomputer is to read before writing.

According to the arrangement order of LED dot matrix chips on the screen, the microcontroller first writes font data to the column drive latch of the first LED dot matrix chip in row 1 in order, and then writes line scan signals to the row drive latch of this row after writing font data to the second and third LED dot matrix chips in row 1.

Then light the first row of the remaining rows in the same way. After being lit, it will be delayed for a period of time, and then the screen will be black, so that the single chip microcomputer can scan the LED screen in one line.

The scanning control of the second line and the third line of the LED display screen by the microcontroller is basically the same until the scanning control of the eighth line. After the control process is completed, the LED display screen can display a complete frame of image.

Although the LED display is lit line by line in this way, only one line is lit at a time, as long as each line can be lit more than 50 times per second, that is, the refresh rate is higher than 50 Hz, the image displayed on the LED display is still a full screen stable image due to human visual inertia.