Unseen "driving" force: IC drivers for LED screens

Chief editor - Vladimir Krylov
Deputy chief editor - Michael Nikulichev

LED screens have established a large niche in the outdoor advertising market. Several years ago it was necessary to convince customers and advertising agents that this new advertising carrier was useful and effective. Today, experienced advertisers know well all the advantages of indoor and outdoor digital advertising. The world is full of companies producing full-color LED screens, large and small, good and not so good. However only a handful of companies is really involved in developing new systems, improving image quality and designing new models. The majority of manufacturers are satisfied by cloning and reselling the existing LED screen systems.

This calls for a reminder that an electronic LED screen is a large and complex system comprising thousands of elements. A screen is only effective if controlled by specialists in both advertising and maintenance. But even these professionals are unaware of numerous elements that make screens work.

A tiny part that is essential in every LED screen is a so called IC driver, microchip that controls LEDs, their brightness and colors. For the last decade the market has been dominated by large companies with excellent reputation that manufacture LED drivers: Macroblock, Toshiba and others. The only problem is these strong chip and semiconductor manufacturers do not understand well real requirements of LED screen makers, those who strive to improve performance of screens and image quality.

In search of new ideas and products we came to central China where a huge corporation CCDL, Central China Display Laboratories has been working since 1988.

CCDL IC driver chip for LED screen CCDL IC driver chip for LED screen

The need for the trip and meeting with company management was primarily determined by two reasons: CCDL manufactures not only IC drivers but LED screens, too. Experts in both areas, they understand in depth requirements of customers and know all problems in LED screen making. We were not disillusioned in our expectations. The corporation has developed a new approach to controlling image quality of the screen. Unlike its competitors, CCDL decided to integrate various control functions in one chip and has created a unique IC driver. This new generation driver can simultaneously control 64 pixels, a task impossible for any other existing driver. They main models PW 19281, PW 192101 have 192 channels for 8x8 pixels with RGB clusters.

The other parameters that determine their high efficiency and reliability are:

  • RGB separate 10 bits inputs. 1,024 levels gradation;
  • 304-pin plastic QFP package;
  • CMOS gate arrays utilizing high-precision fabrication techniques;
  • LVTTL Schmitt input buffer with a fail-safe function that can be used for insertion and removal when power is on;
  • Low noise LVTTL output buffer, drive capability: I=24.0 mA;
  • Supply Voltage: 3.3 V ± 0.3;
  • Ambient temperature: 40°C to + 85°C (for operating);
  • Ambient temperature: 65°C to +150°C (for storage);
  • Load capacitance of output buffer: 100 pF.

Controlled by such IC drivers, screen’s LEDs serve longer and operate in more favorable conditions. As a result, the life of LEDs - the most expensive part of the LED screen - may be expected to increase, and brightness degradation be slower than on other less sophisticated control conditions. The most interesting and important function of CCDL drivers is Failed-Pixel Addressing Technology, that is scanning of LEDs and determination of failed LED lamps.

Large capital R&D investments have positively affected the company's final product: mobile LED screens. CCDL screens are now working in many parts of the world, and their reliability is determined by the correct approach to driving LEDs.