LED driver chips can be divided into general and special chip two chips.
The so-called general-purpose chip, the chip itself is not designed specifically for LED, but some logic chip with an LED display portion of logic functions (such as serial shift register and 2).
The chip is in accordance with special LED light emission characteristics designed specifically for LED display driver chip. LED is a current characteristic of the device, that is, under the premise of saturated conduction, the brightness varies with the change of the current, rather than by adjusting the voltage across it varies. Therefore, one of the largest dedicated chip feature is to provide a constant current source. Constant current source can guarantee the stability of LED drive, eliminating flicker LED, LED display is a high quality picture premise. Some dedicated chip for the requirements of different industries also added some special features, such as with LED error detection, and current gain control current correction.
Evolution of the driver IC:
90s of last century, LED display applications in a single color-based, using the constant voltage driver IC. In 1997, China experienced its first LED display dedicated Driver IC 9701, spans from 16 to 8192 gray gray realize WYSIWYG video. Subsequently, the luminescence properties for LED constant current drive becomes full-color LED display driver of choice, while more highly integrated 16-channel 8-channel driver instead of the driver. The late 1990s, Japan's Toshiba, the United States and Ti Allegro and other companies have introduced 16-channel constant current LED driver chip, the early 21st century, China's Taiwan-based companies have also driven chip production and use. Now, in order to solve a small pitch LED display PCB routing problem, some manufacturers has launched a drive IC LED constant current driver chip highly integrated 48-channel.
Driver IC's performance:
LED display performance indicators, and an image refresh rate and gradation expression is one of the most important indicators. This requires that LED display driver IC inter-channel current high consistency, high-speed communication interface rate and constant speed of response. In the past, refresh rate, and gray-scale utilization of three is a shift in the relationship, to ensure that one or two of the indicators which can be more excellent, would have been appropriate to sacrifice the remaining two indicators. For this reason, many LED display is difficult in practice both ways, either refresh is not enough, the high-speed camera equipment shooting prone black lines or is not enough gray, color brightness and darkness inconsistent. With advances in technology drive IC manufacturer, now a breakthrough in the problem of three high, has been able to solve these problems.
In the application of LED full color display, in order to ensure user comfort for a long time with the eyes, low-light high ash become a test driver IC performance a particularly important standard.
Trends driving the IC:
As a green energy saving LED display is the eternal pursuit, it is also considered an important criterion driver IC performance. Saving driving IC includes two aspects, one is to reduce the knee voltage constant current, and thus the traditional 5V to 3.8V power supply to reduce the following; the second is through the optimization algorithm and IC driver IC design reduces the operating voltage and operating current. There are already manufacturers launched a 0.2V low voltage transition, improvements of up to 15% utilization of LED constant current driver IC, using 16 percent less than conventional products reduce heat supply voltage, so that greatly enhance the energy efficiency of the LED display .
With the rapid decline of the pixel pitch LED display on the unit area to mount packaged devices to grow exponentially, greatly increasing component density module drive surface. In a small pitch P1.9 LED, for example, 15 sweep 160 * 180 90 module requires constant current driver IC, 45 tube rows, 2 138. So many devices available to make PCB routing space become extremely congested, increasing the difficulty of circuit design. At the same time, so crowded arrangement of components, can easily result in poor welding and other issues, but also reduces the reliability of the module. Driver IC less the amount, the greater the PCB layout area, demand from the application side of the driver IC must Forced onto the highly integrated technology roadmap.
Currently, the mainstream industry driver IC vendors have introduced a highly integrated 48-channel constant current LED driver IC, the large-scale integrated circuit peripheral to the driver IC wafer, you can reduce the complexity of the application side of the PCB design , but also to avoid the problems the manufacturers design engineers the ability to design differences or produced.