LED Display Driver IC Function:
It is to receive the data in accordance with the provisions of the agreement, with the data from a receiving card or video processor or other information sources. Then it produces PWM and current, outputs PWM current which is relevant to the brightness, grayscale and refresh rate. Driver IC, logic IC and IC around MOSFET work together on the LED screen showing and displaying effect.
For the photo above, the LED display driver IC noted in red, green, blue colors ellipse has the following functions:
- Red LED driver IC: It is to decide the brightness and control method of the LED display.
- Green LED driver IC: It is a logic IC, which is to control data transfer and decode.
- Blue LED driver IC: It is to provide power to the positive electrode of LED lamps. And only LED displays with scan methods have this type of driver IC.
Types of Driver IC:
There are two types of LED driver IC: General Chip and Special-Purpose Chip.
For the general chip, it is not designed specially for LED, but it has logic ICs which have part of the logic function for the LED display. For the special-purpose chip, it is designed specially for LED display according to the characteristics of LED. LED is a kind of component of the current characteristic, which means the brightness of LED display changes due to the change of the current on the condition of saturated conductivity. As a result, one important feature of the special-purpose chip is to provide a constant current source. The constant current could make sure the stable driver of LED and eliminate the flickering phenomenon, which is the premise to output high-quality content for an LED screen. For some special chips, some special functions are added according to specific applications, like LED error detection, current gain control, current correction, etc.
LED Display Driver IC Evolution:
More than 10 years ago, it is mainly single and double colors LED display in this field. And constant voltage driver IC was adopted for these two types. It was reported that the first type of special-purpose driver IC 9701 in the LED display was developed in 1997. This achievement means the grayscale from 16 grade to 8192 grade. It makes “What you see is what you get” coming true. Later, the constant current driving method became the preferred choice for the full color LED display according to the LED lighting feature. At the same time, a higher integration level of 16 channel driver replaced 8 channel driver. Before the year 2000, Toshiba, Allegro and Ti companies made constant current driver IC with 16 channel drivers. Also, some companies in China Taiwan produced this type. Now, some driver IC manufacturers develop high integration type of 48 channel drivers to meet the requirement of fine pitch LED display.
LED Display Driver IC Performance Index:
The refresh rate, grayscale grade and displaying effect are the most important indexes for an LED display. This requires high consistency of the current in LED display driver IC channels, high-speed communication interface rate, and constant current response rate. Before, it was difficult to make these three aspects balance, which reflects in either the refresh rate is not high and there are many lines on the LED screen when taking videos or photos, or the grayscale is not enough. Now, these three aspects have been solved as the technology of LED display driver IC has been improved.
The Trend of LED Display Driver IC:
1. Energy-saving. There are mainly 2 aspects for energy-saving driver IC:
☛ Converting regular voltage of 5V to 3.8V or below.
☛ Reducing driver IC control voltage and control current after optimizing the IC algorithm.
2. Integration. As small pitch LED display types have been applied more and more widely, it needs much more for driver ICs. This makes the space on PCB very limited and the circuit design is much more difficult. Because of this, high integration with 48 channel LED display driver IC came out. This could solve the problem perfectly.
Below is an example of 48 channel driver IC:
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