【 Weak current College 】 led display several driven solution describes 】

1 Introduction
LED display screen as a high-tech products attracted people's attention, using the computer control, light, electricity as one of the big-screen smart display has been applied to many areas. Led display monitor's pixels with LED light-emitting diode, many light-emitting diodes are arranged in a matrix, LED array, which in turn form constitutes the LED screen. Through different led driver, you can get different effects to images. Therefore the pros and cons of driver chips, on the led screen display quality plays an important role.
LED driver IC can be divided into General and specific chip. Universal chip is typically used for led display monitor's low-end product, such as indoor single, two-color screen, etc. The most common generic chip is the 74HC595 with 8-bit latch, conspiracy and shift registers and 3-state output function. Per-channel maximum output current 35mA (not current). General IC manufacturers are capable of producing such chips.
Because of the LED is the current characteristics of the device, i.e. in saturated on-premise, the brightness with the current size of the changes, not with its voltage changes. Therefore, specific chip one of the greatest features is to provide a constant current source. Constant current source to ensure the stability of the LED drive, eliminate the phenomenon of flashing LED. The following will focus on the led display of special driver IC.
2 chip's main parameters and development status
ASIC has a current, constant-current, and other basic features, compare the requirements applicable to the picture quality of high-current, high places, such as outdoor full color led display, indoor fully colorful display, etc. Chip key performance parameters have the maximum output current, constant current output channels, current output error (bittobit, chiptochip) and data transfer clock, etc.
1) maximum output current
Current mainstream of constant current source chip maximum output currentsare defined as single maximum output current, General 90mA. Current steady is the basic characteristics of a dedicated chip is also the basis for getting superior picture quality. Each channel simultaneous output constant current for maximum value (i.e. maximum constant output current) to display something more meaningful, because the white balance in the State, require each way at the output current of electricity. General maximum constant current output current is less than the allowable maximum output current.
2) constant current output channels
Constant current source output channels with 8-bit (8-ch hengyuan) and 16-bit (16-channel hengyuan) two kinds of specifications, now 16-bit source representing mainstream, its main advantage is reduced chip size, is advantageous for LED driver Board (PCB) layout, especially in the dot pitch smaller LED driver Board more favourable.
3) current output error
Current output error divided into two types of bits between current error, i.e. the same chip each error between the output and a film current error, i.e. different chip error between the output current. Current output error is a very important parameter, the homogeneity of the display screen. The larger the display error of uniformity, the poor, it is difficult to make the screen body reached the white balance. Current mainstream constant current source chip between current error (bittobit) generally in less than 60%, + (chiptochip) film current error in ± 15% or less.
4) data transfer clock
Data transfer clock determines the display of the data transfer speed is display update rate of key indicators. As a large display, the display refresh rate should be above the 85Hz, can guarantee stable picture (no scan HDTV). High data transfer clock is the display gets high refresh rate of the screen. Current mainstream constant current source driver IC shift clock frequency
Rate generally 15MHz above.
In the upper reaches of the LED Epitaxial wafers, chips, United States, Japan, the EU still have a lot of technical superiority, and China Taiwan region has become an important production base of LED. Although China has LED wafer, chip production technology on the distance the advanced international level there is a large gap, national chip and wafer production was concentrated in the low-end product, but the domestic large application needs, to downstream manufacturers LED a tremendous opportunity. Although various chip solutions are used to drive the led display, but because of various chip have feature different, so the driving characteristics of the programme will also vary. Here is our dominant 16-bit constant current led driver IC, and from the application point of comparison between them.