　　 As a high-tech product, LED display has attracted people's attention. The intelligent full-color display that integrates light and electricity with computer control has been applied in a wide range of fields. The pixel points adopt LED light-emitting diodes, and many light-emitting diodes are arranged in a dot matrix to form an LED array, thereby forming an LED screen. Different effect images can be obtained by different LED driving methods. Therefore , the advantages and disadvantages of the LED driver chip play an important role in the display quality of the LED display . LED driver chips can be divided into general-purpose chips and dedicated chips.
General-purpose chips are generally used for low-end products of LED displays , such as single and dual-color screens in indoors. The most commonly used general-purpose chip is the 74HC595, which has an 8 -bit latch, a serial-to-parallel shift register, and a three-state output function. Each channel can output a maximum of 35mA non-constant current.
Since the LED is a current characteristic device, that is, under the premise of saturation conduction, its brightness changes with the magnitude of the current, and does not change with the voltage across it. ASIC most important feature is to provide a constant current source output to ensure stable driving of the LED, the LED flicker elimination. It has the characteristics of large output current and constant current, and is suitable for occasions requiring high current and high image quality, such as outdoor full color screen and indoor full color screen.
　　 LED display with built-in CMOS shift register latch function LED driving chip products SMT5026.SMT5026, can convert serial input data into parallel output data format.
Part II: System architecture of LED display
(1) Display unit
This is the main part of the LED display screen, and a light emitting material composed of a drive circuit. The indoor screen is a unit display panel of various specifications, and the outdoor screen is a unit cabinet.
(2) main controller
The function is to buffer the input RGB digital video signal, grayscale transform, reorganize, and generate various control signals.
(3) Switching power supply
The purpose is to convert 220V AC into various DC power supplies to various circuits.
(4) Transmission cable
The display data and various control signals generated by the master controller are transmitted to the screen body by the twisted pair cable.
(5) Scan controller
The board's function is data buffering, which produces various scan signals as well as duty cycle grayscale control signals.
(6) Dedicated display card and multimedia card ( video card )
In addition to the basic functions of the computer display card, the LED full color screen dedicated display card also outputs digital RGB signals and lines, fields, blanking and other signals to the main controller. In addition to the above functions, the multimedia card can also convert the input analog video signal into a digital RGB signal ( ie, video capture ) .
(7) Other signal sources and their external devices
Including computers, televisions, Blu-ray, DVD , VCD , camcorders, etc.
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