Demonstration of R&D and design capabilities of Shenzhen LED large screen

The LED large screen industry in Shenzhen has gradually shifted from a single labor-intensive processing to an industrial cluster development. At the same time, it has gradually changed from an international processing type to a technological innovation type. In recent years, Shenzhen's independent research and development capabilities of LED large screens have been greatly enhanced. Many high-density and high-definition LED large screens that we could not manufacture ourselves before can now be produced.

What does the refresh rate and gray scale of the LED large screen mean? The following Shenzhen United Huiye Technology will analyze it for everyone. With the development and application of indoor LED large screens, LED large screens can be widely used in command centers, monitoring centers and even studios. However, judging from the overall performance of the LED large screen system, can the images displayed on these LED large screens conform to human vision? Can these displays meet the needs of users? Can these LED large screens withstand different shutters of cameras? The test of taking pictures from different angles? These are the problems that LED large screens need to face. Below I will briefly analyze several major factors that affect the effect of LED large screens (including refresh rate, gray level, etc.).

The gray level of the LED large screen "Gray level" refers to the color levels of various colors between the darkest and the brightest colors, with different changes. Generally speaking, the gray level is above 14 bits (bit), that is, at least There are more than 16,384 color levels, and it is a large high-efficiency LED screen. If the number of gray levels is insufficient, the color level will be insufficient or the gradient color gradation will not be smooth enough, and the color of the video cannot be fully displayed. The LED display effect is greatly reduced.

Some low-efficiency LED large screens can already detect obvious color patch distribution under the shutter speed of 1/500s. If we increase the shutter speed, such as 1/1,000s or 1/2,000s, the situation will be even worse obvious. What affects the refresh rate and gray level of the LED large screen? We know several core components of the LED large screen, such as LED switching power supply, LED driver chip, LED lamp beads, etc., for the refresh rate and gray level of the LED large screen Level, the LED driver chip directly determines the performance of the LED large screen in terms of visual refresh rate and gray scale. Among the current LED driver chips, the latest technology is "ScrambledPWM (S-PWM) technology". S-PWM technology is a technology that improves the traditional pulse width modulation (PWM). into several shorter on-times to increase the overall visual update rate.

To further explain, the S-PWM technology built into the new generation of LED driver chips can break up the original method of counting once per frame (LED grain ON→LED grain OFF) into multiple counts on average , and each broken up equal portion can maintain the original On/Off ratio before breaking up. The large LED screen of the S-PWM driver chip is photographed with a high-speed shutter of a digital camera, and there will still be no horizontal black scanning lines and color block distribution (as shown in the figure below). Its visual refresh rate and grayscale performance are far beyond those of large LED screens using traditional switch-type driver chips.

S-PWM technology provides different counting modes, so it can increase the image refresh rate up to 64 times. If it is replaced by S-PWM to increase the image refresh rate, it only needs to use a low-level clock (such as 5MHz) to easily increase the visual refresh rate by 64 times, and it can reach more than 4,800Hz. Compared with general video vision, the refresh rate is at least 10 times higher, and it can also avoid the problems of high-frequency electromagnetic interference (EMIissue), overshoot and undershoot.

Refresh frequency of LED large screen (visual refresh rate) "Visual refresh rate" refers to the rate of screen update, usually expressed in Hertz (Hz), generally speaking, the visual refresh rate is above 3,000Hz, which is a high-efficiency LED large screen. Screen. The higher the visual refresh rate, the more stable the screen display, and the smaller the visual flicker. The low "visual refresh rate" of the large LED screen not only affects horizontal stripes when taking pictures and taking photos, but also produces images similar to tens of thousands of light bulbs flashing at the same time, which may cause discomfort to the human eye when watching , and even cause damage to the eyes.

Although to the human eye, the visual refresh rate above 60Hz already feels continuous images, but the higher the visual refresh rate, the more stable the displayed image, and the less likely the human eye will feel fatigued. In today's high-quality video, in order to obtain more detailed images, such as wonderful playback or close-up photography, high-speed cameras above 1,000 Hz are used for shooting. At this time, for the large LED screen that will also be photographed, it is a big challenge to still be able to present continuous images (no black scanning lines) or continuous color gradation under high-speed shutter.

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