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Analysis of the common technology of small pitch LED
2019 is a year of great development for small pitch LEDs. In this year, we have seen a lot of cutting-edge technologies. The new generation of COB, TOPCOB, MinLED, MicorLED, especially the appearance of flip-chip and common yin seems to have pointed out a direction for the future development of LED technology. Compared with the revolutionary technology of flip-chip before the mass production, the common-yin technology has become more grounded, and it is also a landing technology that can bring technical improvement to this market in recent years. So, what is the common yin technology? What is the advantage of this technology?
The principle of polarity of the common cathode technology
It is positive and negative. The common anode is to connect the positive poles of the diodes together and drive them by the negative poles. Then the common cathode is to connect the negative poles of the diodes together and drive them by the positive poles. We all know that one LED of a LED consists of red, green and blue LEDs. These diodes illuminate the diodes with their own drive circuits at very high turn-on and turn-off frequencies, and in this way let red, The three colors of green and blue are mixed with each other to show the various colors in our natural world. The common cathode technology is a kind of power supply driving method. Simply speaking, the three color diodes share one cathode (negative electrode) in the circuit design, and the anode (positive electrode) is provided with a control circuit to control the power supply of the LED, so it is called "common cathode". .
In contrast, it is still the "common yang" technology of mainstream technology. Why does the common yin technology bring many advantages? Let us first look at the following circuit schematic:
It can be seen from the figure that the anode of the diode is originally connected together to supply power uniformly, so it is necessary to meet the requirements of the highest voltage diode in the parallel circuit, and only the voltage dividing resistor can be added to the diode with low voltage requirement, and the voltage dividing resistor will Generates power and heat. After the common cathode is used, we can directly supply different voltages according to the different voltage requirements of the diodes, so that it is not necessary to configure the voltage dividing resistor.
Advantages of common yin technology
The operating voltage of the LED lamp bead can be reduced from 4.2-5V to 2.8-3.3V, while the display brightness and display effect are not affected. This reduction in 1V voltage brings a number of advantages:
The direct performance is that the power consumption is reduced by more than 25%. It is difficult to achieve such energy saving because of the need to add a voltage dividing resistor.
Secondly, due to the reduction of power consumption, the screen temperature of the entire screen is lowered. Since the stability and lifetime of the LED are inversely proportional to the temperature, the full-screen LED has higher reliability and longer life;
Finally, the common cathode technology has further improved the integration due to the elimination of excess resistance, which has reduced the number of components of the PCB and further improved the stability.