What are the methods of controlling the grayscale of LED roll-up screens?

  Gray scale is one of the very important parameter when we are using LED roll up screens. Grayscale, also known as halftone, is mainly used for transmitting images with 16, 32 and 64 levels. It uses matrix processing to process the pixels of a file into 16, 32 and 64 levels to make the transmitted image clearer. To display an image or animation, whether on a monochrome, bi-color or tri-color screen, requires adjusting the gray level of each LED emitting light that makes up a pixel, and the fineness of the adjustment is often referred to as grayscale. So did you know that controllingLED roll-up screenAre there any methods of grayscale? The following Vishay Technology editorial is for you:

  Method of controlling the gray level of the LED roll-up screen:

  1. change the current flowing through them.

  Change the current flowing through the LED, generally allow continuous operation current in the 20 mA or so, in addition to the LED red saturation phenomenon, the other LED gray scale is basically proportional to the current flowing through.

  2. Adjust the pulse width.

  We can take advantage of the visual inertia of the human eye to achieve grayscale control using the LED roll-up screen pulse width modulation method, i.e., periodically changing the width of the light pulse (i.e., duty cycle). As long as the repeated illumination period is short enough (i.e., the refresh frequency is high enough), the human eye will not feel the jitter of the light-emitting pixels.

  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 row of pixels from the control box (i.e., pulse width modulation), and then transmit the turn-on signal of each row of LEDs of the LED roller shutter screen serially in the form of pulses (1 when it is on, and 0 when it is not on) to the corresponding LEDs by rows to control whether they are turned on or not. This method of controlling the gray level of the LED roll-up screen uses less equipment, but the amount of serial data transmission is larger, because each pixel requires 16 gray level pulses and 256 gray level pulses in a repeated illumination cycle. LED screens are usually limited to 16 gray levels due to the limitation of the device's operating frequency.

  One type is pulse width modulation. Instead of a switching signal for each LED, the serial transmission from the scanning board is an 8-bit binary gray value. Each LED has its own pulse width modulator to control the illumination time. Thus, only four 16-level grayscale pulses and eight 256-level grayscale pulses are required per pixel during repeated illumination cycles, which greatly reduces the frequency of the serial transmission of the LED roll-up screen. Using this decentralized method of controlling the grayscale of the LED roll-up screen, 256 levels of grayscale control can be easily achieved.

  In summary, this is how to control the grayscale of LED roll-up screens. Because LED roll-up screen pulse width modulation is more suitable for digital control, so in today's widespread use of microcomputers to provide LED display content, almost all LED screens use pulse width modulation to control the gray level of the LED roll-up screen.