Technology | analysis of heat dissipation of LED display screen

Reasons why LED display can be widely used:

Ductility

The larger the LCD screen, the higher the equipment investment of the production line. It is easy to increase the size of LED display, just like building blocks. The resolution is also convenient to realize according to user requirements.

 

Full color

Bulbs and neon lights are monochrome, and led realizes the combination of RGB three primary colors.

 

High reliability

LED is solid, high reliability, unlike neon tubes, bulbs and the like that need vacuum tubes.

 

Long life

The theoretical life of LED chip can reach 100000 hours, and the actual service life is more than 30000 hours.

 

Environment friendly

Led itself is an energy-saving and pollution-free product.

At present, the biggest problem encountered by LED is heat dissipation, and so is led display. The power consumption of LED display screen is very large, and a considerable part of energy is wasted on heating. Heating can cause the following problems:

 

Wavelength drift

Wavelength drift will cause problems in color correction. The wavelength drift of LED is relatively large at low temperature and high temperature. According to the experimental data, the wavelength changes by 0.2-0.3nm for each degree of temperature change.

Output brightness reduction

The change of temperature per degree Celsius leads to the change of 1% output brightness, among which the red light is most affected. From - 40 degrees 180% brightness to 120 degrees less than 50%, that is, the brightness of the red light is reduced by nearly two-thirds. Relatively speaking, the brightness of blue light and green light is not so strongly affected by temperature, especially blue light. When the temperature rises, there is a problem. The brightness of LEDs of different colors is different.

LED life shortened due to temperature rise

According to the data of an American laboratory, the junction temperature increases from 63c to 74C, and the LED life decreases from 36000 hours to 16000 hours.

Excessive heat dissipation components lead to increased system cost

Waste energy and increase user cost

So where does the heat come from? From power supply to LED lamp, to LED driver, and then to adjustable resistance, the heating part includes LED lamp, LED driver and led wiring. Take 5V power supply as an example:

Power supply voltage: 5V;

LED：LED G/B Vfwd=3.2V，LED R Vfwd=2V

1. LED luminous efficiency is about 20%, and led heating accounts for 50% of the total heating

2. The controller and wiring account for about 5% of the total calorific value

3. Driving pressure drop: 1.8V (g / b) or 3V (R) pressure drop. The heating of the driving part accounts for more than 45% of the total heating.

The heating of LED lamp needs to improve the luminous efficiency of LED. The heating of controller and wiring is less, and there is little room for improvement. There is a lot of room to improve the heating of the driving part, which is also the part we expect to improve.

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