Full color LED display driver IC function and role

by:Xinyao LCD     2020-04-09
In the work of full color LED display screen, the function of driver IC is received in accordance with the agreement according to the data ( From receiving card or video processor, etc) , changes in internal production PWM and the current time, output PWM current associated with brightness grayscale refresh, etc to light up the LED. Driver IC and logic IC and surrounding of MOS switch IC, work together in the LED display display function and determine its rendering effect. The LED driver chip can be divided into general and special chip. The so-called general chip, the chip itself is not designed specifically for the LED, but some has LED display part of the logic function logic chip ( Such as string and shift register 2) 。 Refers to the special chip and in accordance with the characteristics of LED and designed specially for the LED display driver chip. LED is device current characteristics, namely on the premise of saturated conductivity, the brightness changes with the change of the current, not by adjusting the voltage at the ends of the change. One of the biggest characteristic is to provide special chip so constant current source. Constant current source can guarantee the stability of the LED driver, eliminate the LED flashing phenomenon, is the precondition of LED display shows high quality images. Some special chip also the requirements of different sectors to increase some special functions, such as have LED error detection and correction of current gain control and current. The evolution of driver IC: in the 90 s, with single and double color LED display application is given priority to, is the constant voltage driver IC. Appeared in 1997, our country's first special LED display driver chip 9701, from 16 grey level crossing to 8192 grey level, realize the video what you see is what you get. Then, in view of the LED characteristics, constant current driver to make the first selection of full-color LED display driver, at the same time, more integrated drive replaced 8 channel drive 16 channels. In the late 1990 s, Japanese companies such as Toshiba, the Allegro, and Ti launched 16 channel LED constant current driver chip, at the beginning of the 21st century, China's Taiwan company driver chip and the production and use. Now, in order to solve the problems of the small spacing LED display PCB wiring, some driver IC manufacturers and introduced a high integration of 48 channel LED constant current driver chip. Driver IC performance indicators: in the performance of the LED display, refresh rate and grey scale and image expression is one of the most important indicator. This requires LED display driver IC channel between the current rate of high consistency, high speed communication interface and constant current response speed. In the past, the refresh rate and utilization rate of gray-scale and is a reciprocal relationship, to ensure that one or two indicators can be more outstanding, will be appropriate at the expense of the rest of the two indicators. To this end, a lot of LED display, in practice it is hard to kill two birds with one stone, either refresh is not enough, it's easy to have a black line under high-speed cameras filming, either gray level is not enough, color and brightness. With the progress of driver IC manufacturers, has been a breakthrough on three highs, have been able to solve these problems. In the application of full color LED display screen, in order to ensure that the user for a long time in the comfort of the eye, high low light grey become a test driver IC performance is the main standard. Driver IC trends: 1, energy saving, as a green energy, energy conservation is the eternal pursue of LED display, is also a important considerations drive IC performance standards. Driver IC energy-saving mainly includes two aspects, one is effectively reduce the constant current inflection point voltage, and then cut the traditional 5 v power supply to 3. The following 8 v; 2 it is through the optimized algorithm for IC design and reduce driving IC operating voltage and current operation. There are manufacturers launched with 0. 2 v voltage low twist, improve the utilization ratio of more than 15% of the LED constant current driver IC, using 16% lower than normal product of the power supply voltage to reduce heat, to greatly improve energy efficiency for LED display. 2, integration: as the LED display pixel spacing drops rapidly, per unit area to SMT packaging components with geometric ratio growth, greatly increase the module density on the surface of the drive components. In order to P1. 9 LED, for example, small spacing 15 of the 160 * 90 modules need 180 constant current driver IC, 45 manager, 2, 138. So many devices, make PCB wiring available space is very crowded, increased the difficulty of the circuit design. At the same time, so crowded components, easy to cause such problems as poor welding, at the same time, it reduces the reliability of the module. Driver IC less dosage, PCB larger area, demand from the application of reversed transmission drive IC must be on the high integration of technical route. At present, the industry mainstream driver IC vendors are successively introduced a high level of integration of 48 channel LED constant current driver IC, the mass of peripheral circuit are integrated into the driver IC wafer, can reduce the complexity of the application side PCB design, also avoid each manufacturer engineers design capability or arising from the difference design problems.
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