As a high-tech product, LED display has attracted great attention. Intelligent full color display screen integrated with light and electricity has been widely applied in many fields. The pixel points are LED light emitting diodes, and many light-emitting diodes are arranged in lattice mode to form a LED array, and then the LED screen is formed. Different effect images can be obtained by different LED driving modes. Therefore, the advantages and disadvantages of the LED driver chip play an important role in the display quality of the LED display. The LED driver chip can be divided into general chip and special chip.
General chip is generally used for low end products of LED display, such as single and double color screen in the indoor. The most common common chip is 74HC595, which has 8 bit latch, serial shift register and three state output function. The current of a non constant current of the maximum output of 35mA per path.
Because LED is a current characteristic device, that is, under the premise of saturation conduction, its brightness varies with the change of current size, and does not change with the voltage at both ends. The most important feature of the special chip is to provide the output of constant current source, to ensure the stable drive of LED and to eliminate the scintillation of LED. Has the characteristics of large output current, constant current, suitable for high current and high quality occasions, such as outdoor full-color, indoor full color etc..
LED display uses LED driver chip products, SMT5026.SMT5026 built in CMOS shift register and latch function, which can transform serial input data into parallel output data format.
The second part: the system architecture of LED display
(1) display unit
This is the main part of the LED display screen, which is made up of light emitting materials and drive circuits. The indoor screen is the unit display board of all kinds of specifications, and the outdoor screen is the unit box.
(2) master controller
The function is to buffer the input RGB digital video signal, transform the gray level, reorganize, and produce various control signals.
(3) switching power supply
The purpose is to change the 220V AC power into various DC electric circuits for various circuits.
(4) transmission cable
The display data and various control signals produced by the master controller are transmitted to the screen body by the twisted pair cable.
(5) scanning controller
The function of the circuit board is data buffering, producing a variety of scanning signals and duty ratio gray level control signals.
(6) special display card and multimedia card (video card)
LED full color display special card in addition to the basic function of the computer display card, also the output of digital signal and RGB, field and blanking signals to the main control instrument. In addition to the above functions, the multimedia card can also transform the input analog Video signal into a digital RGB signal (that is, video acquisition).
(7) other signal sources and their connection devices
It includes computers, TV sets, blue light, DVD, VCD, video camera and so on.