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How is the LED filament shaped?

Update:18 Dec 2018
Summary:

The reason for the junction temperature of the LED is t […]

The reason for the junction temperature of the LED is that not all of the added electrical energy is converted into light energy, but a part is converted into thermal energy. The luminous efficacy of LEDs is currently only 100lm/W, and its electro-optical conversion efficiency is only about 20-30%. That is to say, about 70% of the electrical energy becomes heat.

The LED junction temperature is caused by two factors:

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

2. 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 reduce the recombination rate of carriers in the PN region. The leakage current multiplied by the voltage is the power of this part, which is converted into heat, but this part does not occupy the main component, because the internal photon efficiency is now close to 90%.

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