LED lamp heating cause and calculation formula

LED bulbs are hot in the market, the prices of major brand online stores are dazzling, and expensive is also expensive, cheap and cheap. Today Xiaobian said one of the shortcomings of LED bulbs: fever. What should I do if the LED bulb is hot? LEDs generate heat, and many people think that LEDs are cold light sources. This is just the principle of LED lighting.

Comprehensive current injection efficiency, radiation luminescence quantum efficiency, external light extraction efficiency of the chip, etc., finally only 30-40% of the input electrical energy is converted into light energy, and the remaining 60-70% of the energy is mainly caused by non-radiative recombination lattice vibration. Form converts heat.

The increase in the temperature of the chip enhances the non-radiative recombination and further weakens the luminous efficiency. Because people think that high-power LEDs have no heat, in fact, there are. A lot of heat, so that problems occur during use. In addition, many people who use high-power LEDs for the first time do not know how to solve the heat problem effectively, which makes product reliability a major problem.

The internal quantum efficiency is not high, that is, when electrons and holes recombine, photons cannot be generated 100%, and it is generally called "current leakage" to lower the recombination rate of carriers in the PN region. Multiplying the leakage current by the voltage is the power of this part, which is converted into heat, but this part is not the main component, because the internal photon efficiency is now close to 90%.

The internally generated photons cannot be completely emitted outside the chip and finally converted into heat. This part is the main one, because the current external quantum efficiency is only about 30%, and most of it is converted into heat.

As mentioned above, although the incandescent lamp has a very low light efficiency of only 151m/W, it converts almost all of its electrical energy into light energy and radiates it. Because most of the radiant energy is infrared, the light efficiency is very low. But it eliminates the problem of heat dissipation.

To solve the heat dissipation of LED bulbs, we mainly start from two aspects. Before and after packaging, it can be understood as LED chip heat dissipation and LED bulb heat dissipation. The heat dissipation of the LED chip is mainly related to the selection and process of the substrate and the circuit. This article mainly introduces the heat dissipation of LED bulbs, because any LED will be made into lamps, so the heat generated by the LED chips will always be dissipated into the air through the outer casing of the lamps. Lei Yusi lighting lighting believes that if the heat dissipation is not good, because the heat capacity of the LED chip is small, a little bit of heat accumulation will make the junction temperature of the chip increase rapidly. If it works in a high temperature for a long period of time, its life will be very fast. shorten. However, there is a lot of way for this heat to actually lead the chip to the outside air. Specifically, the heat generated by the LED chip comes out of its metal heat sink block, first passes through the solder to the PCB of the aluminum substrate, and then passes through the thermal conductive glue to the aluminum heat sink. Therefore, the heat dissipation of LED hotel engineering lamps actually includes two parts: heat conduction and heat dissipation.

However, the heat dissipation of the LED lamp housing may have different options depending on the power level and the place of use. There are mainly the following cooling methods:

Aluminum fins: This is the most common way to dissipate heat, using aluminum fins as part of the enclosure to increase heat dissipation.

Thermally conductive plastic case: Fill the thermal conductive material during injection molding of the plastic case to increase the heat conduction and heat dissipation capability of the plastic case.

Air hydrodynamic heat dissipation: Air fluid mechanics uses the shape of the lamp envelope to create convective air, which is the lowest cost way to enhance heat dissipation.

The interior of the fan lamp housing uses a long-life and efficient fan to enhance heat dissipation: low cost and good effect. However, it is more troublesome to change the fan, and it is not suitable for outdoor use. This design is rare.

Heat pipe heat dissipation technology: The heat pipe uses heat pipe technology to guide heat from the LED chip to the heat sink fin of the case. This is a common design in large luminaires such as street lights.

Surface radiation heat treatment treatment of the surface of the lamp housing for radiation heat treatment: simply apply the radiation heat dissipation coating, which can be radiated away from the surface of the lamp housing.

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