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LED full-color display driver IC function and function

time:2021-10-19 source:ZJ Lighting Views:102


  LED full-color display driver IC function and function

  In the work of LED full-color display, the function of the driver IC is to receive the display data (from the receiving card or the video processor and other information sources) in accordance with the agreement, and to produce the PWM and current time changes internally, and the output and brightness grayscale refresh Wait for the relevant PWM current to light up the LED. The peripheral IC composed of driver IC, logic IC and MOS switch works together on the display function of the LED full-color display and determines the display effect it presents.

  1. Classification of LED driver chips

  The so-called general-purpose chip, the chip itself is not specially designed for LED, but some logic chips with some logic functions of LED full-color display screen (such as serial 2 parallel shift register).

LED full-color display driver IC function and function(图1)

  The dedicated chip refers to a driver chip designed specifically for LED full-color display according to the luminous characteristics of the LED. LED is a current characteristic device, that is, under the premise of saturated conduction, its brightness changes with the change of current, rather than by adjusting the voltage across it. Therefore, a feature of the dedicated chip is to provide a constant current source. The constant current source can ensure the stable driving of the LED and eliminate the flicker phenomenon of the LED, which is the prerequisite for the LED full-color display to display high-quality images. Some dedicated chips also add some special functions to the requirements of different industries, such as LED error detection, current gain control and current correction.

  2. The evolution of driver ICs

  In the 1990s, LED full-color display applications were dominated by single and dual colors, using constant voltage drive ICs. In 1997, a dedicated drive control chip 9701 for LED full-color displays appeared in China, which spanned from 16 gray levels to 8192 gray levels, realizing what you see is what you get in video. Subsequently, in view of the LED light-emitting characteristics, constant current drive became the choice of full-color LED display drive, and at the same time, the more integrated 16-channel drive replaced the 8-channel drive. At the end of the 1990s, companies such as Toshiba of Japan, Allegro and Ti of the United States successively introduced 16-channel LED constant current drive chips. At the beginning of the 21st century, the drive chips of Chinese Taiwanese enterprises were also mass-produced and used. Nowadays, in order to solve the problem of small-pitch LED display PCB wiring, some driver IC manufacturers have introduced a highly integrated 48-channel LED constant current driver chip.

  3. Performance indicators of the driver IC

  Among the performance indicators of LED full-color display screens, refresh rate, gray level and image expressiveness are one of the important indicators. This requires high consistency of current between the LED full-color display driver IC channels, high-speed communication interface speed, and constant current response speed. In the past, the refresh rate, grayscale, and utilization rate were in a trade-off relationship. To ensure that one or two of the indicators can be more excellent, the remaining two indicators must be appropriately sacrificed. For this reason, it is difficult for many LED display screens to have the best of both worlds in practical applications. Either they are not refreshed enough, black lines are prone to appear under high-speed camera shooting, or grayscale is not enough, and the color brightness is inconsistent. With the technological advancement of driver IC manufacturers, there have been breakthroughs in the three-high issues and have been able to solve these problems.

  In the application of LED full-color display, in order to ensure the user's long-term eye comfort, low brightness and high gray have become a particularly important standard for testing the performance of driver ICs.

  Energy saving: As a green energy source, energy saving is the eternal pursuit of LED displays and an important criterion for considering the performance of driver ICs. The energy saving of the driver IC mainly includes two aspects. One is to effectively reduce the constant current inflection point voltage, and then the traditional 5V power supply is reduced to below 3.8V; the other is to reduce the operating voltage and operating current of the driver IC by optimizing the IC algorithm and design. At present, some manufacturers have introduced a constant current driver IC with a low 0.2V turning voltage and an LED utilization rate that has increased by more than 15%. The power supply voltage is 16% lower than that of conventional products to reduce heat generation and greatly improve the energy efficiency of LED displays. .

  Integration: The function and role of LED full-color display driver IC. With the rapid decline of the pixel pitch of the LED display screen, the packaged devices to be mounted on a unit area have increased geometrically, which greatly increases the component density of the module driving surface. Take the P1.9 small-pitch LED as an example, a 15-scan 160*90 module requires 180 constant current drive ICs, 45 line tubes, and 2 138s. With so many devices, the wiring space available on the PCB becomes extremely crowded, which increases the difficulty of circuit design. At the same time, such a crowded arrangement of components can easily cause problems such as poor soldering, and also reduce the reliability of the module. With fewer driver ICs and a larger wiring area on the PCB, the demand from the application side forces the driver IC to embark on a highly integrated technical route.