Why ED display screen can be widely used, my summary is as follows:
1. Scalability: The larger the LCD screen, the higher the equipment investment in the production line. The increase in the size of the LED display is very easy, just like building blocks. The resolution is also convenient to realize according to user needs.
2. Full color: light bulbs, neon lights, etc. are all monochromatic, LED realizes the combination of RGB three primary colors.
3. High reliability: LED is solid-state lighting with high reliability, unlike neon tubes, bulbs and the like that require vacuum tubes.
4. Long life: The theoretical life of the LED chip can reach 100,000 hours, and the actual life is more than 30,000 hours.
5. Environmentally friendly: LED itself is an energy-saving and pollution-free product.
The biggest problem currently encountered by LEDs is heat dissipation, and the same is true for LED displays. The power consumption of the LED display is very large, and a considerable part of the energy is wasted on heat. Fever can cause the following problems:
1. Wavelength drift: Wavelength drift will cause problems in color correction. The wavelength drift of the LED is relatively large at low temperature and high temperature. According to experimental data, for every degree of temperature change, the wavelength changes by 0.2-0.3nm.
2. Output brightness reduction: 1% of the output brightness change caused by temperature change per degree Celsius, of which the red light is the most affected. From -40 degrees 180% brightness, to 120 degrees brightness is less than 50%, that is to say, the brightness of the red light is reduced by nearly two-thirds. Relatively speaking, the brightness of blue light and green light has less temperature influence, especially blue light. When the temperature rises, there is a problem. The brightness of LEDs of different colors is different.
3. The temperature rise causes the LED life to be shortened: According to the data of a laboratory in the United States, the junction temperature increased from 63C to 74C, and the LED life was reduced from 36,000 hours to 16,000 hours.
4. Too many heat-dissipating components lead to higher system costs.
5. It wastes energy and increases user costs.
So where does the heat come from? From the power supply to the LED lamp, to the LED driver, and then to the adjustable resistance, the heating part includes the LED lamp, the LED driver, and the LED connection line. Let's take 5V power supply as an example:
Power supply voltage: 5V,
LED: LED G/B Vfwd=3.2V, LED R Vfwd=2V
1. The luminous efficiency of LED is about 20%, and LED heating accounts for 50% of total heating
2. The controller and connecting wires account for about 5% of the total heat generation
3. Drive voltage drop: 1.8V(G/B) or 3V(R) voltage drop, the heating of the drive part accounts for more than 45% of the total heating.
The heating of the LED lamp needs to improve the luminous efficiency of the LED, the controller and the connecting wire have less heating, and there is not much room for improvement. There is a lot of room for improvement in the heat generation of the driving part, and it is also the part we look forward to improving.