Classification and Performance Parameters of LED Full Color Display Driver Chip
The LED full-color display driver chip is an important part of the display. Different driving methods of the LED chip can obtain different display image display effects. Therefore, the pros and cons of the driver chip will affect the display effect of the full-color in Novastar MCTRL5 LED display. Plays an important role.
LED Driver Chip Is Classified Into The Following Two Types
- General-purpose chip: It is used more in low-end LED screen production. The most commonly used general-purpose chip is 74HC595, which has 8-bit latch, serial-parallel shift register, and tri-state output. Each channel can output a maximum of 35 mA (not constant current).
- Dedicated chip: One of the biggest features of the dedicated chip is the supply of constant current. Because LED is a current characteristic device, that is, under the premise of saturation and conduction, its brightness changes with the change of the current, not with the voltage across the Change. The constant current source can ensure the stable driving of the LED and eliminate the flicker phenomenon of the LED.
Important Parameters Of LED Display Chip
Maximum output current: At present, the maximum output current of the mainstream constant current source chip is about 90 mA. Constant current is the basic feature of the dedicated chip technology, and it is also the basis for obtaining high picture quality. And each channel simultaneously outputs the maximum value of the constant current (that is, the maximum constant output current) is more meaningful to the display screen, because under the white balance condition, each channel is required to output the constant current at the same time.
Current output error: There are two types of current output errors. One is the inter-bit current error, which is the error between each output of the same chip. The other is the inter-chip current error, which is the error of the output current between different chips. . The current output error is a very important parameter of LED and has a great impact on the uniformity of the full color display. The larger the error, the worse the uniformity of the display screen, and it is difficult to make the screen body reach the white balance. At present, the bit-to-bit current error of the mainstream constant current source chip is generally within + 60%, and the chip-to-chip current error is within ± 15%.
The number of futures of constant current source transmission: There are two types of constant current source: 8-way constant source and 16-way constant source. Now 16-bit sources occupy the mainstream. The advantage is that the size of the LED driver chip is small, which is convenient for the LED driver HUB78 board (PCB) Wiring is more advantageous for LED driver boards with smaller dot pitch.
Data shift clock: The data shift clock determines the transmission speed of display data and is a key indicator that affects the update rate of the display screen. As a large-sized LED display device, the display refresh rate should be above 85 Hz to ensure a stable picture (no scanning glare). A higher data shift clock is the basis for the display to obtain a high refresh rate picture. At present, the mainstream constant current source driver chip shift clock frequency is generally above 15 MHz.
