Tool/software: Linux
I read an electronic magazine in which there is a report on how to solve the problem of LED cooling. After reading, I became interested in LED coolings. So I searched some related materials and information about this topic. Today I come to this forum to turn to you to discuss my understandings are appropriate.
Here are my personal understandings:
LED is known as the fourth generation of lighting or green light source, with energy saving, environmental protection, long life, small size, can be widely used in a variety of instructions, display, decoration, backlight, general lighting and urban night and other fields. In recent years, some of the world's economically developed countries around the development of LED launched a fierce technical competition. Which LED cooling has always been an urgent problem to be solved!
There are research data show that if the LED chip junction temperature of 25 degrees when the light is 100%, then the junction temperature rose to 60 degrees, the amount of light is only 90%; junction temperature of 100 degrees when the drop to 80%; 140 Only 70% of the degree. Can be seen to improve heat, control junction temperature is very important thing.
In addition to this LED heat will make its spectral movement; color temperature rise; forward current increases (constant pressure power supply); reverse current also increased; increased thermal stress; phosphor epoxy aging accelerated All kinds of problems, so that the LED cooling is the most important LED lighting design of a problem.
How to produce LED chip junction temperature ?
The reason LED heat is because the added power is not all converted into light energy, but part of the conversion into heat. LED light effect is currently only 100lm / W, the electro-optical conversion efficiency of only about 20 to 30%. That is, about 70% of the electricity has become heat.
Specifically, the LED junction temperature is due to two factors caused.
1. The internal quantum efficiency is not high, that is, in the electron and hole recombination, and can not produce 100% of the photon, commonly known as the "current leakage" leaving the PN region carrier recombination rate decreased. Leakage current multiplied by the voltage is part of the power, that is, into heat, but this part does not account for the main component, because now the internal photon efficiency is close to 90%.
2. The internally generated photons can not be all emitted to the outside of the chip and eventually converted to heat, which is the main reason, because the current known as the external quantum efficiency is only about 30%, most of them are converted into heat.
Although the incandescent light effect is very low, only 15lm / W or so, but it will almost all of the energy into light energy and radiation, because most of the radiation is infrared, so the light effect is very low, but exempt from The problem of heat dissipation.
LED cooling is now more and more people pay attention, it is because the LED light failure or its life is directly related to its junction temperature, heat dissipation is very good junction temperature, life is short.
Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of Led coolings. I need continual learnings.
What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.
May someone would like to help ?
thanks in advance
