Analysis of Problems Existing in LED Display Driver Chips

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

Since LED is a current characteristic device, that is, under the premise of saturated conduction, its brightness changes with the change of current size, not with the change of voltage across its two ends. Therefore, one of the biggest features of dedicated chips is to provide a constant current source. The constant current source can ensure the stable drive of LED and eliminate the flickering phenomenon of LED. The following will focus on the problems existing in the dedicated driver chip of LED display.

Problems

1. Power consumption and heating issues

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

2. Application cost issues

A mainstream 16-bit steady-state current LED display driver chip can only drive 16 LED devices. A LED display with a resolution of 1024×768 must use multiple driver chips to achieve the desired effect, which makes the material cost relatively high. If the driver chip itself adopts a scanning method, then a mainstream driver chip can drive multiple LED devices at a time, which will greatly reduce the application cost.

Summarize:

Judging from the product structure of these LED driver chip manufacturers, the current mainstream chips are mainly divided into three grades. The first grade 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 second grade is a chip with output open circuit detection (LOD), temperature overheat protection (TSD), and brightness adjustment functions. These chips are more suitable for specific occasions due to their additional functions. For example, if they are used for variable information boards, the chip is required to have the ability to detect LED errors. The third grade 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 that the screen displays good picture quality.