LED driver chips can be divided into general and special chip. General-purpose chips are generally used for low-end products, such as indoor single color led display screen. The most commonly used general-purpose chip 74HC595, 8-bit latch, serial-parallel shift register and the three-state output. Each maximum output current of 35 mA (not constant). The general IC manufacturers can produce such chips.
Because LED is a current characteristic of the device, i.e., under the premise of saturated conduction, the brightness change with the current size of the change, not change with the change of voltage across. Therefore, one of the greatest features of the dedicated core is to provide a constant current source. The constant current source can ensure the stable driving of the LED to eliminate the flickering of the LED. The following will focus led display dedicated driver chips.
Problems
1 power consumption and heat problem
Led display chip power consumption and heat output current problem is the obstruction of driver chip development factors. In drive mode handheld led display screen that may arise in the future, this problem will become particularly prominent. With the LED device manufacturing process and the level of progress and drive current decreases, the problem will be solved step by step.
2 application cost issues
A mainstream 16 steady-state current led display screen driver chips can only drive 16-channel LED devices. A resolution is 024 × 768 led display must use multiple driver chips in order to get the desired effect, so that makes the material cost is relatively high. If by scanning driver chip, a the mainstream driver chip will be able to drive once a multi-channel LED devices will make applications to reduce the cost of many.
3 Summary
From this several LED driver chip manufacturer's product structure, the current mainstream chip is mainly divided into three grades. The first grade is a chip with a gray mechanisms, such chip with PWM function, gray, can be generated based on the input data easier to form deep-level gray-scale, high-quality screen is displayed. Second grade with the output open detection (LOD), Over Temperature Protection (TSD), brightness adjustment function of the chip Mai Yang, thanks to additional features, these chips are more suitable for specific occasions, such as for variable information boards, chip LED fault detection. The third file is the constant current source chip, without any additional features such chips only for LED constant current source to ensure that the led display screen body good picture quality.
