However, judging from the overall performance of the LED display system, can these displays meet the needs of users? Can the images displayed on these LED displays meet the human vision? Can these LED displays withstand the different shutters of the camera? The test of camera from different angles? These are all issues that need to be considered for LED display screens. Below I will analyze several major factors (including refresh rate, gray level, etc.) that affect the LED display effect.
1. The refresh frequency of the LED display (visual refresh frequency): "Visual refresh frequency" refers to the screen update rate, usually expressed in Hertz (Hz). Generally speaking, the visual refresh frequency is above 3,000 Hz, which is efficient Can LED display. The higher the visual refresh frequency, the more stable the screen display, and the smaller the visual flicker. The low "visual refresh rate" of the LED display has an impact, in addition to the horizontal stripes appearing during video and photography, but also images similar to tens of thousands of light bulbs flickering at the same time, which may cause discomfort when viewed by the human eye , And even cause damage to the eyes.
2. The gray level of the LED display screen: "Gray level" refers to a variety of colors between *dark and *bright colors, with different color levels. Generally speaking, the gray level is above 14 bits. That is, it has at least 16,384 color levels and is a high-performance LED display. If the number of gray levels is insufficient, the color level is insufficient or the gradient color level is not smooth enough, and the color of the video cannot be fully displayed. The LED display effect is greatly reduced. Some low-efficiency LED displays can already be detected with obvious color patch distribution under the shutter 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.
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 frequency 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 on the traditional pulse width modulation (PWM) technology, which disperses the turn-on time of an image 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 count once per frame (LED die ON→LED die OFF), and break it up into multiple counts on average. , And each divided aliquot can maintain the original On/Off ratio before being broken up.
S-PWM technology provides different counting modes, so it can increase the image refresh rate up to 64 times. If you change to S-PWM to increase the image refresh rate, you can easily increase the visual refresh rate by 64 times with a low-level clock (such as 5MHz), and it can reach more than 4,800Hz. Compared with general video, the refresh rate is at least 10 times higher, and it can also avoid the problems of high-frequency electromagnetic interference (EMIissue), over-voltage surge (Overshoot) and under-voltage surge (Undershoot).
The LED display of the S-PWM driver chip is photographed with a digital camera's high-speed shutter, and there is still no horizontal black scan line and color patch distribution. Its visual refresh rate and gray scale performance far surpass those of LED displays using traditional switch-type driver chips.
The high-quality LED driver chip, built-in S-PWM technology, makes the refresh frequency up to 3840Hz, the gray level can reach 16bit, and when shooting under the condition of high-speed shutter, there will be horizontal black scan lines and color block distribution.
