LED display as a high-tech products have aroused great attention, the use of computer control, optical, electrical integration of intelligent full color display has been widely used in the field. The pixels using LED light-emitting diodes, many light-emitting diodes arranged in dot matrix, constitute the LED array, and then constitute the LED screen. Through different LED drive mode, you can get different effects of the image. So the advantages of LED driver chip, LED display display quality plays an important role. LED driver chip can be divided into general-purpose chips and special chips.
General chip is generally used for LED display low-end products, such as indoor single, two-color screen. The most commonly used general-purpose chip is the 74HC595, with 8-bit latch, serial shift register and tri-state output. Each channel can output a maximum of 35mA non-constant current.
As the LED is the current characteristics of the device, that is, under the premise of saturation conduction, its brightness changes with the size of the current changes, not with the voltage changes at both ends of the change. The biggest feature of the dedicated chip is to provide constant current source output, to ensure the stability of the LED drive to eliminate the LED flashing phenomenon. With the output current, constant current and other characteristics, suitable for demanding high-current, high-quality occasions, such as outdoor full color, indoor full color and so on.
LED display with LED driver chip series SMT5026.SMT5026 built-in CMOS shift register and latch function, you can convert the serial input data into parallel output data format.
The second part: LED display system composition structure
(1) display unit
This is the main part of the LED display screen, by the luminescent material and drive circuit. Indoor screen is a variety of unit display panel, outdoor screen is the unit box.
(2) the main controller
The role is to enter the RGB digital video signal buffer, grayscale transformation, reorganization, and produce a variety of control signals.
(3) switching power supply
The purpose is to make 220V AC power into a variety of DC power provided to a variety of circuits.
(4) transmission cable
The display data generated by the master and the various control signals are transmitted by the twisted pair cable to the screen body.
(5) scan the controller
The function of the circuit board is data buffer, resulting in a variety of scanning signals and duty cycle gray-scale control signal.
(6) dedicated graphics card and multimedia card (video card)
LED full color display card in addition to the basic functions of the computer graphics card, but also the output of digital RGB signals and lines, fields, blanking and other signals to the master. Multimedia card in addition to the above functions can also enter the analog video signal into a digital RGB signal (that is, video capture).
(7) other sources and their external devices
Including computers, televisions, Blu-ray, DVD, VCD, video recorders and so on.