LED display driver IC is such a key component, it is like the central nervous system of the human brain, and it is in charge of the body's physical actions and the mental thinking of the brain. The performance of the driver IC determines the effect of the led display screen, especially the use of modern large-scale activities and high-end venues, making people more stringent requirements for LED display driver IC.
The role of the driver IC: Receiving display data (from the receiving card or video processor and other information sources) in accordance with the protocol, produce PWM and current time changes, output PWM current which has relation with LED display brightness, grayscale, refresh rate,etc prameters. to light LED display. Driver ICs, logic ICs, and peripheral ICs composed of MOS switches work together to display the functions of the LED display and determine the display effect it presents.
The classification of the driver IC: led display driver chip can be divided into two kinds of general-purpose chips and special chips.
The so-called general-purpose chip, the chip itself is not designed specifically for the LED, but some logic chips with a led display part of the logic function.
The special chip refers to the driver chip designed specifically for the LED display according to the LED light emitting characteristics. LED is a current characteristic device, that is, under the premise of saturation conduction, its brightness changes with the change of the current, rather than by adjusting the voltage across it. Therefore, one of the biggest characteristics of a special chip is to provide a constant current source. The constant current source can ensure the stable driving of the LED and eliminate the flickering phenomenon of the LED, which is a prerequisite for the LED display to display a high-quality picture. Some special chips also add special features for different industry requirements such as LED error detection, current gain control, and current correction.
Because led is a current characteristics device, that is, under the premise of saturation conduction, its brightness changes with the change of the current size, not with the change of the voltage across it. Therefore, one of the biggest features of a dedicated chip is to provide a constant current source. The constant current source ensures stable LED driving and eliminates LED flicker.
The problems of LED display driver chips:
1: Application cost
A mainstream 16-bit steady state current LED display driver chip can only drive 16 LED devices. A LED display with a resolution of 1024 x 768 must use multiple drive chips to achieve the desired effect, which results in higher material costs. If the driving chip itself adopts a scanning method, then a mainstream driving chip can drive multiple LED devices at a time, which will reduce the application cost.
2: power consumption and heat problems
Due to the large output current, the power consumption and heat generation of LED display chips have always been the first factor that hinders the development of the driver IC. This problem will become more prominent in the future of handheld LED display drive methods that may occur. With the advancement of the price of LED electronic display screen manufacturing process and the reduction of driving current, problems will be solved gradually.
3: Currently mainstream chips are mainly divided into 3 levels. The first level is a chip with a gray-scale mechanism. This type of chip has a PWM function inside it. It can generate gray levels based on input data, and it is easier to form deep gray levels and display high-quality images. The second layer is a chip with output open-circuit detection (LOD), temperature over-temperature protection (TSD), and brightness adjustment functions. These chips are more suitable for specific occasions due to additional functions. For example, they are required for variable information boards. With LED detection error. The third level is a constant current source chip without any additional functions. This type of chip only provides a constant current source for the LED and ensures good screen display quality.
Drive IC evolution:
In the 90s of the last century, LED display applications were dominated by single and double colors, using a constant voltage driver IC. In 1997, China's first LED display dedicated drive control chip 9701 emerged. It spanned 16 shades of gray to 8192 shades of gray to achieve WYSIWYG. Subsequently, for the LED light-emitting characteristics, constant-current drive to become the preferred choice for full-color LED display driver, while the more integrated 16-channel drive replaces the 8-channel drive. In the late 1990s, Japan's Toshiba, Allegro, and Ti of the United States successively introduced 16-channel constant current LED driver chips. At the beginning of the 21st century, the driver chips of Chinese Taiwanese companies were also mass-produced and used. Today, in order to solve the problem of PCB layout of small-pitch LED display screens, some driver IC manufacturers have also introduced highly integrated 48-channel LED constant current driver chips.
Driver IC performance indicators:
Among the performance indicators of LED display screens, refresh rate and gray level and image expression are one of the most important indicators. This requires high consistency of the current between the LED display driver IC channels, high-speed communication interface rate, and constant current response speed. In the past, the three aspects of refresh rate, grayscale, and utilization rate were a kind of shifting relationship. To ensure that one or both of the indicators can be more excellent, we must appropriately sacrifice the remaining two indicators. For this reason, many LED displays are difficult to achieve the best of both worlds in practical applications, or they are insufficiently refreshed. High-speed camera equipment is prone to black lines when they are photographed, or the gray scale is not enough, and the color brightness is inconsistent. With the advancement of driver IC manufacturers' technology, there have been breakthroughs in the three high issues and these problems have been solved.
In the application of small-pitch LED display, in order to ensure the user's comfortable eyes for a long time, low-light and high-gray becomes a particularly important standard for testing the performance of the driver IC. This article is collected by the China Identification Network. For more information, please visit the logo Business School.
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