What are the problems with LED display chip drivers?

LED driver chips can be divided into general chips and special chips. General chips are generally used in indoor single-color and dual-color screens. The most commonly used general chip is 74HC595, which has 8-bit latch, serial-to-parallel shift register, and three-state output functions. Each channel can output a maximum current of 35mA (not a constant current). Generally, IC manufacturers can produce such chips.

Because the led is a current characteristic device, that is, under the premise of saturated conduction, its brightness changes with the change of the current size, not with the change of the voltage at both ends. Therefore, one of the biggest features 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.

The LED display is mainly a large-size flat-panel display formed by splicing display units composed of LEDs and their driving chips.

The performance of the driver chip plays a vital role in the display quality of the LED display. In recent years, with the vigorous development of the LED market, many powerful IC manufacturers, including Japan’s Toshiba (TOSHIBA), Sony (SONY), the United States’ Texas Instruments (T1), Taiwan’s Macroblock (MBl) and Dianjing Technology ( SITl), etc., began to produce LED driver chips. However, the current LED display chip driver has the following three problems.

1. Power consumption and heating problems

Due to the large output current, the power consumption and heat generation of the LED display chip has always been the first factor hindering the development of the driver chip. This problem will become particularly prominent in the driving methods of handheld LED displays that may appear in the future. With the improvement of the manufacturing technology level of LED devices and the reduction of driving current, the problem will be gradually solved.

2. Cost issue

A mainstream 16-bit steady-state current LED display driver chip can only drive 16 LED devices. An LED display with a resolution of 1024x768 must use multiple drive chips to achieve the desired effect, which makes the material cost relatively high. If the driver chip itself adopts the scanning method, then a mainstream driver chip can drive multiple LED devices at one time, which will reduce the application cost a lot.

3. Picture quality issues

At present, mainstream chips are mainly divided into 3 levels. The 1st level is a chip with a grayscale mechanism. This type of chip has a PWM function inside, which can generate grayscale according to the input data, making it easier to form a deep grayscale and display high-quality images. The 2nd level is chips with output open circuit detection (LOD), temperature overheats 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 the ability to detect LED errors. The 3rd level is a constant current source chip without any additional functions. This type of chip only provides a constant current source for the LED to ensure good screen quality.