LED screen chip function introduction


The LED screen is composed of many chips to perfectly display various brilliant colors. The chip is equivalent to the brain of the LED screen. It is the process of copying the display image 1 to 1 to the LED screen through computer programming. The chip needs high-speed calculation during work. And LED screen signal receiving and sending conversion. Recently, the trade war between the United States and China has been in full swing. In this trade war, the United States has banned the supply of chips to ZTE within 7 years, which is of particular concern.

Chip technology, the country's most important weapon, is the core of the core technology of the electronic integrated circuit industry. The ZTE chip incident reflects my country's shortcomings in chip technology, and the core technology is controlled by others, which is not conducive to the healthy development of the industry. In the field of communication, my country's chips rely heavily on foreign imports, and the annual chip imports are astonishingly large. Once foreign countries stop exporting to us, our entire industry will face a state of shock, and the consequences will be very serious.

Chip technology is also the core of technology in the LED screen industry. It is necessary for us to understand the role of chip technology in the development of the LED screen industry. The performance of the LED screen is closely related to the LED driver chip. The following joint Huiye editor (www.xspled.com) will introduce the relationship between the LED screen and the chip. 1. Dedicated chip: The dedicated chip has the characteristics of large output current and constant current, and is more suitable for occasions with large current and high image quality requirements, such as outdoor full-color screens, indoor full-color screens, etc.; the key performance parameters of the dedicated chip are the maximum output current , constant current source output channels, current output error and data shift clock, etc.

2. Number of output channels of constant current source: The number of output channels of constant current source mainly has two specifications: 8 (8-bit source) and 16 (16-bit source). Now 16-bit source is basically the mainstream: such as TLC5921, TB62706/TB62726, MB15026/MB15016 etc. The main advantage of the 16-bit source chip is that it reduces the chip size and facilitates the wiring of the LED driver board (PCB), especially for PCBs with small pitches. 3. Maximum output current: At present, the maximum output current of mainstream constant current source chips is mostly defined as the maximum output current of a single channel, generally around 90mA.

Constant current is the most fundamental characteristic of dedicated chips, and it is also the basis for obtaining high image 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 in the white balance state, each channel is required to output the constant current at the same time. Generally, the maximum constant current output current is less than the allowable maximum output current.

4. Current output error: The current output error is divided into two types, one is the inter-bit current error, that is, the error between each output of the same chip; the other is the inter-chip current error, that is, the output current between different chips error. The current output error is a key parameter, which has a great influence on the uniformity of the display screen. The larger the error, the worse the uniformity of the LED screen, and it is difficult to make the screen body achieve white balance.

At present, the bit-to-bit current error of mainstream constant current source chips is generally less than ±6%, and the inter-chip current error is less than -+15%. 5. General-purpose chips: General-purpose chips are generally used for low-end products of LED screens, such as indoor single-color screens, double-color screens, etc. The most commonly used general-purpose chip is the 74HC595.

74HC595 has 8-bit latch, serial-parallel shift register and three-state output. Each channel can output a maximum current of 35mA (non-constant current). General IC manufacturers can produce such chips.

6. Types of driver chips: LED driver chips can be divided into general-purpose chips and special-purpose chips. The so-called general-purpose chip, the chip itself is not specially designed for LED, but some logic chips with some logic functions of the LED screen (such as serial-parallel shift register). The dedicated chip refers to a driver chip designed specifically for LED screens according to the LED light-emitting characteristics.

LED is a device with current characteristics, that is, under the premise of saturated conduction, its brightness changes with the change of current, rather than by adjusting the voltage across it. Therefore, one of the biggest features of the dedicated chip is to provide a constant current source. The constant current source can ensure the stable driving of the LED and eliminate the flickering phenomenon of the LED, which is the prerequisite for the LED screen to display high-quality images.

Some special-purpose chips also add some special functions according to the requirements of different industries, such as brightness adjustment and error detection. 7. Data shift clock: The basic functions of the LED screen driver chip include the function of a serial shift register, so as to realize the cascading and transmission of display data, and build a large-size LED screen with multiple display points. The data shift clock determines the transmission speed of the display data, and plays a vital role in the update rate of the display data displayed on the display.

As a large-size display device, the display refresh rate should be above 85Hz to ensure a stable picture (no scanning flicker). A higher data shift clock is the basis for the display to obtain high refresh rate images. At present, the shift clock frequency of mainstream constant current source chips is generally above 15MHz.

The above-mentioned focus is on professional chip technology. LED driver special chip technology is related to the quality and stability of the overall picture of the LED screen. The core technology of electronic components like this must be firmly in our own hands to ensure the healthy and sustainable development of the LED screen industry! .

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