At present, LED electronic displays appear more and more frequently in various occasions, and their excellent display effects are attracting more and more customers to buy and use. However, many people use mobile phones or cameras to take pictures of LED displays. But it is very likely to find that things such as water ripples do not show the effects seen by the human eye. So what is going on here? Here, Topsun Optoelectronics conducts a brief analysis from several places such as refresh frequency and gray level. What is the impact of PWM technology on LED electronic display refresh?

   Refresh frequency of LED electronic display

   "Refresh frequency" refers to the number of times the screen is updated per second, usually expressed in Hertz (Hz is the unit). Generally speaking, the refresh frequency is above 3,000Hz, which is a high-performance LED electronic display. The higher the visual refresh rate, the more stable the screen display. The visual flicker is smaller. The low "visual refresh rate" of the LED electronic display has the effect of not only the horizontal stripes appearing during shooting and photography, but also images similar to tens of thousands of light bulbs flickering at the same time. This may cause discomfort when viewing, and even cause damage to the eyes.

 Although to the human eye, the visual refresh rate of more than 60Hz has already felt a continuous picture, but the higher the visual refresh frequency, the more stable the displayed image, and the less fatigue the human eye will feel. Nowadays, in 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 per second are used for shooting. At this time, for the LED electronic display that will also be photographed, it is a big challenge to still be able to present continuous images (without black scanning lines) or continuous color gradation under high-speed shutter.

  Grayscale of LED electronic display

 "Gray level" refers to various colors that have different color levels between the darkest and brightest colors. Generally speaking, the gray level is 14 bits or more, that is, at least 16,384 color levels or more. It is a high-performance LED. Electronic display screens. If the number of gray levels is insufficient, there will be a lack of color gradation or the color gradation is not smooth enough, and the color of the film cannot be fully displayed. The LED display effect is greatly reduced. Some low-efficiency LED electronics When the display screen is under 1/500 shutter, the obvious color patch distribution can already be detected. If I increase the shutter speed, such as 1/1,000 or 1/2,000, it will be more obvious.

 Know several core components of LED electronic display, such as LED switching power supply, LED driver chip, LED lamp beads, etc. For the refresh frequency and gray level of LED electronic display, LED driver chip directly determines the visual refresh of LED display Representation of frequency and gray level. Among the current LED driver chips, the highest new technology is "ScrambledPWMS-PWM technology." S-PWM technology is an improved radical pulse width modulation (PWM technology, which divides the on-time of an image into several shorter leads). Through time, to increase the overall visual update rate. Furthermore, the built-in S-PWM technology of the new generation of LED driver chips can count once per frame (LED die ON LED die OFF method, average Break up into multiple counts, and each broken up 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 switch to S-PWM to increase the image refresh rate, you only need to use a low-level clock (such as 5MHz to easily increase the visual refresh rate by 64 times, and it can reach 4,800Hz or more. Compared with the general video refresh rate) The ability of at least 10 times higher, can also prevent the occurrence of high-frequency electromagnetic interference (EMIissu over-voltage surge (Overshoot and under-voltage surge (Undershoot) problems.

The LED electronic display of the S-PWM driver chip uses the high-speed shutter of the digital camera to take pictures, and there is still no horizontal black scan line and color patch distribution. Its visual refresh frequency and gray level expression are far beyond the use of a radical switch type drive. Chip LED electronic display.