LED electronic display driver IC function and role?

Publisher: Supplier of LED Display Time: 2020-11-11 Views: 1911

In the work of the LED electronic display, the role of the driver IC is to receive the display data (from the receiver card or video processor and other sources of information) in accordance with the provisions of the protocol, in the internal production of PWM and the current time change, the output and the brightness of the gray scale refreshing and other related PWM current to light up the LED. the driver IC and the logic IC and the peripheral IC composed of MOS switches, the joint role of the LED display function and determine the display effect. The driver IC, logic IC and peripheral IC consisting of MOS switches work together in the display function of the LED display and determine the display effect it presents.

 

LED driver chip can be divided into general-purpose chip and special-purpose chip. The so-called general-purpose chip, the chip itself is not specifically designed for the LED, but some of the LED display part of the logic function of the logic chip (such as string 2 and shift registers).

 

The special chip is designed in accordance with the LED light-emitting characteristics of the LED display driver chip, LED is the current characteristics of the device, that is, under the premise of saturated conduction, its brightness changes with the current changes, rather than by adjusting the voltage on both sides of the changes. Therefore, one of the biggest features of the special chip is to provide a constant current source. Constant current source can ensure the stable driving of LED, eliminate the flickering phenomenon of LED, is a prerequisite for LED display to show high-quality picture. Some special chips for different industries also added some special features, such as LED error detection, current gain control and current correction.


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1, the evolution of driver IC

 

In the 90s of last century, LED display applications to single and two-color based, using a constant voltage driver IC. 1997, China's first LED display dedicated driver control chip 9701, from 16 levels of gray scale across to 8192 levels of gray scale, realizing the video of WYSIWYG. Subsequently, for the LED light-emitting characteristics, constant current drive has become the first choice of full-color LED display driver, while the higher integration degree of 16-channel drive instead of 8-channel drive. 20 century, the end of the 1990s, Japan, the United States companies have launched 16-channel LED constant current driver chip, the beginning of the 21st century, China Taiwan-based companies have also been mass-produced and use of the driver chip. Nowadays, in order to solve the problem of small pitch LED display PCB wiring, some driver IC manufacturers have launched a highly integrated 48-channel LED constant current driver chip.

 

2, driver IC performance indicators

 

In the LED display performance indicators, refresh rate and gray level and image performance is one of the most important indicators. This requires high consistency of current between the LED display driver IC channels, high speed communication interface rate and constant current response speed. In the past, the refresh rate, gray level and utilization of three aspects is a kind of relationship, to ensure that one or two of the indicators can be more excellent, we must properly sacrifice the remaining one to two indicators. For this reason, many LED display in the practical application is difficult to have the best of both worlds, either the refresh is not enough, high-speed camera equipment to shoot black lines easily, either gray scale is not enough, the color darkness and brightness is not consistent. With the advancement of driver IC manufacturers technology, has now been a breakthrough in the three high problems, has been able to solve these problems.

 

In the application of LED electronic display, in order to ensure the comfort of the user's eyes for a long time, low brightness and high gray has become a test of the performance of the driver IC is a particularly important criterion.

 

3, the trend of driver IC

 

Energy saving: as a green energy, energy saving is the eternal pursuit of the LED display, but also an important criterion to consider the performance of the driver IC. Driver IC energy saving mainly includes two aspects, one is to effectively reduce the constant current inflection point voltage, and then the traditional 5V power supply to 3.8V operation; the second is through the optimization of IC algorithms and design to reduce the driver IC operating voltage and operating current. Currently there are manufacturers have introduced a 0.2V low inflection voltage, to enhance the LED utilization rate of more than 15% of the constant current driver IC, the use of conventional products 16% lower supply voltage to reduce heat, so that the LED display energy efficiency greatly improved.


Integration: With the rapid decline in the pixel pitch of the LED display, the unit area to be mounted on the packaging device to geometric multiples of the growth, greatly increasing the module drive surface component density. P1.9 small pitch LED, for example, 15 sweep 160 * 90 module requires 180 constant current driver IC, 45 line tube, 2 138. so many devices, so that the PCB available wiring space has become extremely crowded, increasing the difficulty of circuit design. At the same time, such a crowded arrangement of components, very easy to cause welding problems, but also reduces the reliability of the module. Driver IC less dosage, PCB larger wiring area, the demand from the application side to force the driver IC must be on a highly integrated technology route.


At present, the industry's mainstream driver IC suppliers have launched a highly integrated 48-channel LED constant current driver IC, large-scale peripheral circuits integrated into the driver IC wafers, can reduce the complexity of the application side of the PCB circuit board design, but also to avoid the design capabilities of engineers from various manufacturers or design differences in the problems arising.