There are two ways to control LED brightness. One is to change the current flowing through the LED, the general LED tube permits continuous current at 20 mA or so, in addition to a saturation of the red LED, the other LED brightness is substantially proportional to the current flowing; Another way is to use the human visual inertia with a pulse width modulation method to achieve gray scale control, that is, periodically changing a light pulse width (i.e. duty cycle), as long as the repetition cycle of light is short enough (ie, refresh frequency is high enough), human eye do not feel luminescent pixel in jitter. Since the pulse width modulation is more suitable for digital control, the microcomputer to provide the universal LED display content Today, almost all of the LED display are controlled using pulse width modulation gradation.
led tube set
LED control system usually consists of the main control box, scanning panels and display and control device has three major components. Main control box from the computer’s graphics card to get a screen pixel color luminance data, and then re-allocated to several blocks scan board, each board is responsible for controlling scanning LED screen on several rows (columns), and each row (column) on the LED display and control signals are transmitted with a serial manner. There are two serial transmission of display control signals: one is the central control panel scanning gray of each pixel, the scan board from the control box for each line of pixels brightness value decomposition (i.e. pulse width modulation), Then each row of LED turn signals in pulses (lit one, does not shine as 0) by line using serial transmission to the corresponding LED on the control whether the light. The use of fewer components, but the serial transmission data volume, because in a repeating cycle of light, each pixel in the 16 gray levels requires 16 pulses, the 256 gray levels required under 256 pulses, due to device operating frequency limit, generally only the LED screen to do 16 shades of gray.
Another method is to scan the contents of a serial transfer sheet is not a switch signal for each LED but an 8-bit binary brightness value. Each LED lighting has its own pulse width modulator to control the lighting time. Thus, in a repeating cycle of light, each pixel in the 16 gray scale requires only four pulses, 256 gray scale only eight pulses, greatly reducing the serial transmission frequency.