In the work of LED full-color display , the function of the driver IC is to receive the display data according to the protocol ( from the receiving card or video processor and other information sources ) , internally generate PWM and current time changes, output and brightness grayscale refresh The associated PWM current is used to illuminate the LED . Display driver IC and a logic IC and a peripheral IC composed of MOS switches, act on the LED display and determine their current form of display.
1 , LED driver chip can be divided into general purpose chip and special chip
The so-called general-purpose chip, the chip itself is not designed specifically for LEDs , but some logic chips ( such as string 2 and shift registers ) with some logic functions of the LED display .
The dedicated chip refers to a driver chip specially designed for LED display screen according to the LED light-emitting characteristics . The LED is a current-characteristic device, that is, under the premise of saturation conduction, its brightness changes with the change of current, rather than by adjusting the voltage across it. Therefore, one of the biggest features of the dedicated chip is to provide a constant current source. The constant current source can guarantee the stability of LED drive, eliminating a flicker of the LED, the LED display shows high-quality images of the premise. Some dedicated chips also add special features for different industry requirements, such as LED error detection, current gain control and current correction.
2 , the evolution of the driver IC
The 1990s, LED display to a single color-based application, uses a constant voltage driver IC. In 1997 , China's first LED display driver control chip 9701 appeared , which crossed from 16 gray levels to 8192 gray levels, realizing the WYSIWYG of video. Subsequently, for LED lighting characteristics, constant current drive became the first choice for full-color LED display drive, while the more integrated 16- channel drive replaced the 8- channel drive. The late 1990s, Japan's Toshiba, the United States and Ti Allegro and other companies have launched 16-channel constant current LED driver chip, the beginning of the 21st century, China's Taiwan-based companies have also driven chip production and use. Nowadays, in order to solve the problem of PCB layout of small-pitch LED display , some driver IC manufacturers have introduced a highly integrated 48- channel LED constant current driver chip.
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