With the development and application of indoor LED display more and more, whether in the command center, monitoring center or even in the studio, you can see that the LED display is widely used. However, from the perspective of the overall performance of the LED display system, can these displays meet the needs of users? Can the images displayed by these LED displays conform to human vision? Can these LED displays withstand different shutter speeds of the camera? The test of different angles of photography? These are all issues that LED display screens need to consider. Below I will make a brief analysis of several factors (including refresh rate, gray level, etc.) that affect the effect of LED display.  

 

　　1. The refresh rate of the LED display (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 efficient Can LED display. The higher the visual refresh rate, the more stable the screen display and the less visual flicker. The low "visual refresh rate" of the LED display screen will not only affect the horizontal horizontal stripes during videography and photography, but also produce images similar to tens of thousands of bulbs flashing at the same time, which may cause discomfort to the human eye when viewing. , and even cause damage to the eyes.  

 

　　

Although for the human eye, the visual refresh rate above 60Hz has been perceived as a continuous picture, but the higher the visual refresh rate, the more stable the displayed image, and the less likely the human eye feels fatigued. Nowadays, in high-quality video, in order to obtain a finer picture, such as the wonderful playback or the process of close-up photography, high-speed cameras of more than 1,000 Hz per second are used for shooting. At this time, it is a big challenge to be able to present a continuous picture (no black scanning lines) or continuous color gradation even at a high shutter speed for the LED display that will also be photographed.

 

2. Gray scale of LED display: "Gray scale" refers to the color gradation of various colors between the darkest and brightest colors, with different changes. Generally speaking, the gray scale is above 14 bits (bit). That is to say, it has at least 16,384 color levels and above, which is a high-efficiency LED display. If the number of gray scales is insufficient, there will be insufficient color gradation or insufficient smoothness of the gradation color level, so that the color of the video cannot be fully displayed. The LED display effect is greatly reduced. Some low-efficiency LED displays can already detect obvious color distribution at 1/500s shutter speed. If we increase the shutter speed, such as 1/1,000s or 1/2,000s, the situation will be even more obvious.

 

Third, what affects the refresh frequency and gray level of the LED display?

 

We know several core components of the LED display, such as LED switching power supply, LED driver chip, LED lamp beads, etc. For the refresh frequency and gray level of the LED display, the LED driver chip directly determines the visual refresh rate of the LED display. , the performance of gray scale. Among the current LED driver chips, the latest technology is "ScrambledPWM (S-PWM) technology". S-PWM technology is an improvement of the traditional pulse width modulation (PWM) technology, which disperses the on-time of an image into Several shorter on-times to increase the overall visual refresh rate. To further explain, the built-in S-PWM technology of the new generation of LED driver chips can break up the original method of counting once per frame (LED die ON→LED die OFF) into multiple counts on average. , and each equal part that is scattered can maintain the original On/Off ratio before it is scattered.

 

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

 

The LED display of the S-PWM driver chip is photographed with a high-speed shutter of a digital camera, and there is still no horizontal black scanning line and color block distribution. The performance of its visual refresh rate and gray level far exceeds that of LED displays using traditional switching driver chips.

 

The high-quality LED driver chip has built-in S-PWM technology, making the refresh rate up to 3840Hz and the gray level up to 16bit. When shooting with high-speed shutter, horizontal black scanning lines and color block distribution will appear.