Full color led display driver IC function and role
LED full-color display of the work, the role of the driver IC is to receive the agreement in accordance with the provisions of the display data (from the receiving card or video processor and other information sources), in the internal production of PWM and current time changes, output and brightness gray refresh Related to the PWM current to light the LED. Driver IC and logic IC and MOS switch composed of peripheral IC, the role of the LED display on the display and determine the presentation of the display.
LED driver chip can be divided into general-purpose chip and dedicated chip two:
The so-called general-purpose chip, the chip itself is not specifically designed for the LED, but some with LED display part of the logic function of the logic chip (such as string 2 and shift register).
The special chip is designed in accordance with the LED light-emitting characteristics designed specifically for LED display driver chip. LED is the current characteristics of the device, that is, under the premise of saturation conduction, the brightness changes with the current changes, rather than by adjusting the voltage at both ends of the change. So the biggest feature of a dedicated chip is to provide constant current source. Constant current source can ensure the stability of the LED drive to eliminate the flashing LED phenomenon is the LED display shows the premise of high-quality screen. Some special chips also for the requirements of different industries to add some special features, such as LED error detection, current gain control and current correction.
Drive the evolution of the IC
The last century, 90 years, LED display applications to single and double color, using a constant voltage drive IC. In 1997, China appeared in the first LED display dedicated drive control chip 9701, from 16 gray scale to 8192 level gray, to achieve the video of the WYSIWYG. Subsequently, for the LED light-emitting characteristics, constant current drive to become full-color LED display driver of choice, while a higher degree of integration 16-channel drive instead of 8-channel drive. The 20th century, the late 90s, Japan's Toshiba, the United States Allegro and Ti and other companies have launched 16-channel LED constant current driver chip, the early 21st century, China Taiwan-based enterprise driver chip also mass production and use. Now, in order to solve the problem of small-pitch LED display PCB layout, some driver IC manufacturers have introduced a highly integrated 48-channel LED constant current driver chip.
Driver IC performance indicators
In the LED display performance indicators, refresh rate and grayscale and image performance is one of the most important indicators. This requires high consistency between the LED display driver IC channels, high-speed communication interface rates, and constant current response. In the past, the refresh rate, the gray scale and the utilization rate are three aspects of the relationship, to ensure that one or two of the indicators can be more excellent, it is necessary to sacrifice the remaining two indicators. To this end, many LED display in the practical application is difficult to the best of both worlds, or is not enough refresh, high-speed camera equipment under the black line is easy to shoot, or is not enough gray, color brightness is inconsistent. With the driver IC manufacturers of technological progress, has been in the three high problems on the breakthrough, has been able to solve these problems.
In the LED full color display application, in order to ensure the user for a long time with the eye comfort, low light gray test to become a test driver performance is a particularly important standard.
Driving IC Trends
1, energy saving
As a green energy, energy saving is the eternal pursuit of LED display, but also consider the driver IC performance is an important criterion. Driving IC energy-saving mainly includes two aspects, one is to effectively reduce the constant current inflection point voltage, and then reduce the traditional 5V power supply to 3.8V below; Second, by optimizing the IC algorithm and design to reduce the driver IC operating voltage and operating current. At present, manufacturers have introduced a 0.2V low turn voltage, to enhance the LED utilization of more than 15% of the constant current driver IC, the use of conventional products than the 16% lower supply voltage to reduce heat, so that LED display energy efficiency greatly improved The
With the LED display pixel pitch decreased rapidly, the unit area to be mounted on the packaging device to increase the geometric factor, greatly increasing the module drive surface component density. To P1.9 small pitch LED, for example, 15 sweep 160 * 90 module requires 180 constant current driver IC, 45 rows of tubes, 2 138. So many devices, so that PCB available wiring space has become extremely crowded, increasing the difficulty of circuit design. At the same time, so crowded components of the arrangement, easily lead to poor welding and other issues, but also reduces the reliability of the module. Driving ICs less, PCBs larger wiring area, and demand from the application side Forced drive ICs must embark on a highly integrated technology route.
At present, the industry's leading driver IC suppliers have introduced a highly integrated 48-channel LED constant current driver IC, large-scale peripheral circuits integrated into the driver IC wafers, can reduce the application of PCB circuit board design complexity , But also to avoid the manufacturers of engineers design or design differences arising from the problem.