LCD Display screen flicker

 > LCD Display screen flicker

The flickering phenomenon of the LCD display is called flicker. Flicker seriously affects the viewing effect of the lcd display , and the lcd display may be permanently damaged if it is operated in this state for a long time.

what is LCD Display screen flicker

The various polarity conversion methods of the panel have another characteristic of liquid crystal molecules, which is that they cannot always be fixed at a certain voltage. If the liquid crystal molecules are fixed at an angle for a long time, the liquid crystal molecules will no longer be able to respond to changes in the electric field due to the destruction of their characteristics. Rotation, so the liquid crystal molecules need to keep moving, so the method used is to allow the liquid crystal molecules to rotate in positive and negative electric fields. The absolute values of the positive and negative electric fields are the same, so the angle of rotation of the liquid crystal molecules is the same, and the brightness of the sub-pixel display is the same. When the display screen remains motionless, the liquid crystal molecules are constantly rotating, so as to maintain the normal operation of the LCD display.

Display flicker
LCD Display screen flicker
LCD Display screen flicker

However, there are also problems with this. Due to fluctuations in the production process, the opening voltage and closing voltage of each TFT switch, as well as the pixel capacitance, are different. When the same positive and negative voltages are applied, the brightness of the sub-pixels will be different. This kind of picture flickers. The phenomenon is called flicker. Flicker is a very important parameter and is measured with special instruments. The unit of flicker is dB, such as Konica Minolta’s CA410, admesy and other professional testing instruments.

So how to improve the flicker of the display?

Flicker is due to the difference in brightness between positive and negative frames. By modifying the common voltage, most sub-pixels can be kept in an acceptable range. For example, there are two voltages of 3V and -3V, but due to differences in the manufacturing process, the actual voltages become 4V and -2V. If no adjustment is made, flickers will occur, because when the same screen is displayed, 4V and -2V The corresponding brightness is different. By adjusting the common voltage to -1V, 4V and -2V are corrected to 3V and -3V, thereby eliminating the flickering phenomenon on the screen.

flicker

From the previous introduction, we know that the polarity of the picture needs to be constantly changed. In other words, for all sub-pixels in the lcd display screen, its polarity is constantly changing. There are two ways to invert pixels: column inversion and point inversion.

 

The first is column inversion. The polarity of the sub-pixels in each column is opposite, and the sub-pixels in one column have the same polarity.

column reversal

There is also dot inversion, that is, the polarity of each sub-pixel and its surrounding sub-pixels are different.

Point reversal

For lcd display screen flickering, dot inversion is the best inversion method, but because it consumes too much power, it is rarely used. The column flip mode is the most used. Different flip modes correspond to different flicker test images. Only by using the corresponding test screen can you get accurate results.

Column reversal tets image
dot inversion test image

Effect of signal on flicker

If the transmission signal is interfered with, the picture will flicker. For example, if there is strong electromagnetic or electric field interference near MIPI, LVDS, RGB, and SPI transmission cables, the picture will flicker. You can try placing the LCD displayer somewhere free of distractions and test whether the display improves.

signal impact

LCD display screen refresh frequency

The refresh rate of a normal LCD display is 60Hz. When the refresh rate is lower than this value, more sensitive people will be able to detect the flickering of the lcd display screen. We only need to set the refresh rate to above 60Hz, so this will not happen. Phenomenon.

LCD display screen operating environment

The LCD display is designed to withstand an operating temperature. It can operate stably at a suitable temperature. When the appropriate operating temperature is exceeded, problems may occur:

  1. When the operating temperature is too low, the display may fail to start, horizontal lines or smear may appear on the display, etc.
  2. When the operating temperature is too high, the impurities in the liquid crystal will precipitate more ions at high temperatures, and the charged particles will form an electric field in the display screen. This electric field will interfere with the work of the display screen and cause flickering or image sticking problems.

The lcd display is damaged.

The performance of the LCD display screen will be attenuated or damaged during use. For example, if it is scratched during the production process or the welding is not firm, it will be completely damaged during long-term use. This kind of failure cannot be recovered and only Can be repaired by replacing parts.

lcd damage
lcd damage
lcd bonding defects
lcd damage
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