First of all, starting from the color point: single-color, two-color, three-color (full-color) LED display: 1. Monochromatic refers to the luminescent material whose display material has only one color, mostly red. 2. The two-color screen is generally composed of red and green LED diodes. 3. Three-color (full-color) screen, Outdoor LED screen from red…
First start from the color point: monochrome, two-color, three-color (full color) LED display:
1.Monochromatic refers to a luminescent material in which the display material has only one color, mostly red.
2.Two-color screens generally consist of red and green LED diodes.
3.Tri-color (full color) screen, consisting of red, green (wavelength 570nm), blue; true color, consisting of red, pure green (wavelength 525nm), blue.
Secondly, according to the environment: indoor, outdoor and semi-outdoor led display:
1.Indoor and outdoor semi-open air curtain, high brightness, can be used in outdoor sunlight, the screen is sealed, usually placed on the roof or window.
2.The indoor screen area is generally small (more than ten square meters), and the point density is very high. Under direct sunlight or ambient light, the visual distance is several meters. Because it is indoor, it does not need to open the air, and the screen cannot have Sealed waterproof function. Because the indoor display brightness is not high, the indoor display dot matrix module is mainly used.
3.The outdoor display area is tens of square meters, hundreds of square meters or even thousands of square meters, the point density is relatively thin (more than 1000-4000 points per square meter), and the luminous brightness is 3000-6000cd/square meter (different directions, brightness The requirements are also different), in direct sunlight, the visual distance is tens of meters, because it is outdoor, so you must use a waterproof box with a good wind-resistant, rain-proof and lightning-proof screen.
Classification of LED display
LED screens are divided into indoor LED screens and outdoor LED screens according to the use environment; LED screens are divided into single-primary LED screens, dual-primary LED screens and full-color LED screens according to display color; , 64, 128, 256-level gray LED screens, etc.; LED screens are divided into text LED screens, graphic LED screens, synchronous video LED screens, TV video LED screens, etc. according to display performance.
System composition structure of 6 major LED display screens
- Display unit: This is the main part of the LED display screen, which is composed of luminescent materials and driving circuits. The indoor screen is the unit display board of various specifications, and the outdoor screen is the unit box.
- Main controller: the function is to buffer the input RGB digital video signal, transform grayscale, reorganize, and generate various control signals.
- Switching power supply: The purpose is to convert 220V alternating current into various direct currents and provide them to various circuits.
- Transmission cable: The display data and various control signals generated by the main controller are transmitted to the screen body by twisted pair cables.
- Scanning controller: The function of the circuit board is data buffering, generating various scanning signals and duty ratio grayscale control signals. /6. Special display card and multimedia card (video card): In addition to the basic functions of a computer display card, the special display card for LED full-color screen also outputs digital RGB signals and signals such as line, field and blanking 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).
- Other signal sources and their external devices: including computers, TV sets, Blu-ray, DVD, VCD, camcorders, etc.
LED display driver chip introduction
As a high-tech product, LED display has attracted people’s attention. The intelligent full-color display that integrates light and electricity using computer control has been used in a wide range of fields. The pixel points use LED light-emitting diodes, and many light-emitting diodes are arranged in a dot matrix to form an LED array, which in turn forms an LED screen. Through different LED driving methods, images with different effects can be obtained. Therefore, the quality of the LED driver chip plays an important role in the display quality of the LED display. LED driver chips can be divided into general-purpose chips and special-purpose chips.
General-purpose chips are generally used for low-end LED display products, such as indoor single-color and double-color screens. The most commonly used general-purpose chip is the 74HC595, which has an 8-bit latch, a serial-parallel shift register, and a three-state output. Each channel can output a non-constant current of up to 35mA.
Because the LED is a current characteristic device, that is, under the premise of saturated conduction, its brightness changes with the change of the current size, and does not change with the change of the voltage across it. The biggest feature of the special chip is to provide a constant current source output, to ensure the stable driving of the LED, and to eliminate the flickering of the LED. It has the characteristics of large output current and constant current, and is suitable for occasions requiring large current and high image quality, such as outdoor full-color screens, indoor full-color screens, etc.