Is LED backlighting an anti-historical trend? The screen flash problem has been around since the era of CRT displays. CRT is the meaning of a cathode ray tube. The display using this imaging device is relatively large in size, which is the kind of "big head" product we used in the past. The imaging principle of CRT monitors is to use the electron gun to bombard the phosphor on the picture tube to produce images. Because the frequency of this bombardment is not enough, the screen will flicker. This kind of flicker is very obvious, almost every user who uses CRT monitor. Can feel it. As the CRT display exits history, the LCD display begins to surface. The initial LCD monitors used CCFL backlights, which are cold cathode fluorescent tubes. The lamp is closely attached to the rear of the display panel to emit light, and the device supplies light to the liquid crystal through a polarizing plate or the like. The backlight has a certain relief for the problem of the screen flash, but because it is not environmentally friendly and consumes a large amount of energy, in the country Under control, began to gradually withdraw from the market. Nowadays, CCFL backlight products are hardly seen on the market. LED backlights have occupied almost all markets, not only in the display field, but also in the backlight system of TVs and mobile phones. This is a solid-state light source with long life, low energy consumption and small size, making LED the most mainstream backlight device. So why do some people say that LED backlighting is born against the historical trend? One of the most important reasons is that after using the LED display, some of the sensitive users of the eyes began to notice the flickering phenomenon of the screen. In the process of using the eyes, the eyes are sore and tearful, so why is the LCD monitor only different in backlight? In the case, the problem of screen flicker has appeared again? Is this the sin of LED backlight? Here we have to mention the problem of PWM dimming, which is the key point that causes the LCD screen to flicker. PWM dimming problem you don't know We know that the display can adjust the brightness, so how is this change realized? The principle is that the display needs to adjust the brightness of the LED light, and the brightness is too complicated to adjust the brightness. In order to save cost, adjust the brightness of the screen. The industry will use a flashing way to solve it. The brightness of the LED light source is fixed, so that the LED light source is continuously turned on and off, and the brightness of the screen is adjusted by adjusting the opening time and the closing time. The specific process is like this, for example, the LED backlight flashes 1000 times, of which 500 times are turned on and 500 times are turned off. If the time of opening is stopped for 1 second, the time of closing is paused for 0.5 seconds. At this time, the brightness of the screen is lower than the opening and closing. The backlight system of the same time is strong. In this way, when the user adjusts the brightness of the screen, the brightness of the brightness actually benefits from the change of the LED backlight blinking. In fact, this adjustment method is called PWM modulation (pulse width modulation) in the industry. In actual products, the brightness of LED backlights is very fast. The general public display with PWM dimming usually operates at about 200Hz-1000Hz, while the human eye is hard to detect when the frequency reaches 100Hz. The obvious brightness changes, because the process of human perception of brightness is accumulated. When the speed of flashing is fast enough, the picture seen by the human eye is "always bright". Most of the current product displays on the market use PWM modulation. This kind of display can see the flickering problem when the screen brightness is dark, and the user with sensitive eyes can see the impact of the PWM brightness adjustment on the eyes. In fact, we can also do such a test, when dimming the brightness of the screen, use your finger to shake the screen, you will see obvious residual image, and when the brightness is high, it is a fan-shaped picture. So is the CCFL backlight display not using PWM modulation? Why is there only a problem with LED flashing? Is the CCFL backlight not flashing? In fact, the CCFL backlight display also uses PWM modulation, but since CCFL is a kind of fluorescent lamp, the flashing situation is not serious. This is because the process of forming a spot on the phosphor by the electrons in the fluorescent tube has a retarding effect, so there is a visual retention, that is, an afterglow effect. Therefore, for a display using CCFL backlight, it does have certain advantages in flicker performance, but it does not really solve the problem of screen flash. LED backlight Due to the principle of illumination, the LED backlight is on or off, so it is difficult to form the afterglow effect. Therefore, in the PWM modulation, the LED display flashes significantly at low brightness. At this time, the LED light source is turned off longer than the open time, and the human eye's perception of "darkness" is obvious. The following figure is a comparison of the 0 brightness screen flash of the LED backlight and the CCFL backlight. We found that the PWM fluctuation of the CCFL backlight is also very large. LED backlighting does not go against history. Although it has defects in the problem of flickering, it is only obvious when it is low in brightness. The CCFL backlight is also essentially flickering. To completely solve the problem of screen flicker, there are two ways, one is to change the PWM modulation method, one uses self-issued display technology, such as the future OLED display screen, there is no such problem. At present, to achieve no flash screen can only solve this problem from the PWM modulation. Industry's silent screen flash solution There are also two ways to start with PWM modulation, which can achieve the effect of making the screen not flash. One is to use a linear dimming method to modulate the LED without this adjustment. In fact, this method is to change the brightness of the LED current, but the LED light-emitting material will have different color temperature when the current is different (the LED backlight will be burnt out when the brightness is too high). Therefore, linear dimming has certain drawbacks. The way to improve this effect is to make the brightness of the screen less adjustable, so that the color temperature of the screen will not change significantly. Household Electric Screwdriver Household Electric Screwdriver,Mini Power Screwdriver,Mini Tool Kit,Screw Driver Power Tool SUZHOU CREATION SPACE INTELLIGENT TECHNOLOGY CO.,LTD , https://www.mypkey.com