LED chip in the whole small spacing LED system, its quality and performance and high stability, reliability, low light high grey high brush and other indicators characteristics are closely related. Therefore, it puts forward the following three higher requirements for LED chips:
There are strict requirements on the dead light rate of LED lamp beads
Because the industry standard of the traditional LED display dead light rate is in one in 10,000, and the density of the light bead chip of the small spacing led display is larger, so the dead light rate of small spacing should be controlled in one in 100,000 or even one in a million to meet the needs of long-term use. Otherwise, after a period of time, the dead light will cover the whole screen, which is unacceptable to the user. Therefore, such a strict dead light rate, on the LED chip factory quality control system put forward higher requirements.
There are two commonly used evaluation indicators in the field of LED chips: 1. "static electricity release" refers to the chip's ability to withstand the impact of static electricity without damage. As the number of LED chips used in small spacing display screens has increased by geometric multiples, in order to reach the strict dead light rate of one part per 100,000 or even one part per million, the chip must pass the full test of ESD 2000v, in order to maximize the guarantee that each one will not be broken by static electricity. 2. "reverse leakage current" : the smaller the leakage current of LED chip, the higher its reliability, the longer the service life, and the less likely it is to die. At present, the highest standard in the industry is less than 0.05uA@ -12v, and only a few chip factories can do this, so the strict implementation is even less.
02 LED chip how to improve response to high refresh rate requirements
Small spacing LED display, due to the need to face some cameras and shooting, will have a higher refresh rate requirements than conventional display. Therefore, the higher the refresh frequency is, the higher the tolerance of LED chip in high frequency pulse current. However, for the display made by the existing ordinary chip, the higher refresh rate will lead to various inconsistent abnormal display of the display screen in the future. Therefore, the LED chip should not only have the shortest response time when dealing with high refresh, but also need to turn on the capacitor with high consistency and turn off quickly and all the time.
How can LED chip realize the display requirement of small spacing, low brightness and high grey
As a result of today's users of small spacing product requirements are no longer to compare who is high brightness, but to compare who is low brightness. Comparison is whose display can achieve a reduction in brightness without loss of gray and picture quality. Therefore, the realization of low brightness and high gray, small spacing LED display in addition to the use of high-performance driver IC, and LED chip is crucial.
In order to ensure a good display effect, small spacing LED display sets clear requirements on the total brightness per unit area. The increase in the number of chips of bit area means that the brightness of a single LED chip needs to be reduced in the same proportion. The overall brightness of LED display screen is generally realized by adjusting the driving current of LED chip. In the use environment of some small spacing leds, the forward current of LED chip has been reduced to 1mA or even less than 0.5ma. This requires that under small current operation, the brightness and wavelength of the RGB tricolor chip must have a good consistency, and when the working current is adjusted, the brightness and wavelength change characteristics of the RGB tricolor chip must be basically consistent, otherwise, there will be the phenomenon of splashes.