What's the difference between LED screen scanning
Author:Heaven and earth Time:2021-06-10 13:33 Browse(949)
After years of production practice of LED display screen, scanning drive is widely used nowadays. Scanning driver uses the characteristics of human eyes. When LED is driven by high frequency current pulse, human eyes can feel it
After years of production practice of LED display screen, scanning drive is widely used nowadays.
scanning drive uses the characteristics of human eyes.

What's the difference between LED screen scanning

when LED is driven by high-frequency current pulse, human eyes can feel itIt is the average value of effective brightness.
for example.
LED is driven by 20mA current pulse with 50% duty cycle, and its luminous effect is equivalent to driving by 10mA constant DC (100% duty cycle).
in application
the duty cycle is usually 1:16 (6.25%).
theoretically.
the LED is driven in the mode of 1:16 (1 / 16 of the practical LED is on, and the other 15 / 16 of the practical LED is off), and the pulse current is lowHowever, in practical application, the pulse time of 1 / 16 is calculated according to the refresh rate of the whole screen and the technical parameters provided by the LED supplierIt is suggested that the maximum value of pulse current should be 5 times of the constant current value.
because the pulse current exceeds 50 Ma, its size is not directly proportional to the luminous brightness.
therefore, the brightness of the lamp should be improvedIt can still be close to the brightness of 20mA static driving.
the results show that the brightness of the system is still close to that of 20mA static drivingAdvantages of scan drivenThe biggest advantage of scan driver is to save driver chip.
make the driver circuit simple, so as to reduce the cost.
the design of scan driver is simpleDisadvantages of scan driverThe LED display adopts scanning driving mode.
if the maximum current limit is also followed, it will not appear any problem.
however.
the problem is gradually obviousLarge pulse current is used to get the required brightness, which makes the light output decay faster than that of LED without scanning drive.
the results show that the LED with large pulse current can get the required brightnessThe life of LED display is defined as normal operation until the white peak output value is the original valueHowever,
for the scanning drive system with a duty cycle of 1:8 or higher, its service life is greatly reduced(divided by 4), the brightness is only half of the factory value in about two yearsAnother problem is that the LED screen still has "mosaic" phenomenon in its service life, which is a disgusting phenomenonThis is due to the adoption of scanning driver.
each LED module is aging at a different rateCompared with the difference of adjacent pixels, the human eye is more sensitive to this effect.
the results show that the human eye is more sensitive to this effectIf different batches of LEDs are applied to one LED display screen, the situation may be even worse.
because the brightness of different batches of LEDs may also be inconsistent.
some LEDs must be improved during factory productionLine adjustment to make the LED of the whole screen match.
for those LEDs that are already dark, more current should be used to drive them.
this means that they will age faster in the future.
the light output of LEDs will increase with timeIn other words, in the early stage of normal use, the attenuation is faster.
LED displays produced in different batches are used.
the scanning driving mode is adopted, which may lead to the emergence of MA in less than a yearSeck phenomenonShanghai Xixun offline with gray controllerPowerful network function.
supports all kinds of views (AVI.
mpg, MP4, 3gp, WMV, ASF, flv, etc.). Flash animation (SWF) supports all kinds of scanning modes.
.
speed difference.
.
the speed of flash animation is different
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