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The reason and the calculation of LED lights heating

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With the increase of temperature of the chip, can enhance non radiative recombination, and further weaken the luminous efficiency. Because, people subjectively think no heat of large power LED, but in fact. A large amount of heat, that occur in the use of process problems. Plus many first-time use of high-power LED thermal problem of people, also don't understand how to effectively solve, make the product reliability has become a major problem. So, LED is there a heat generating? How much can produce heat?
Driven by the electric field, overcoming the PN junction electric field, from area N to area P transition, these electronic and P area of the hole composite. Due to drift to the free electron P District P district price is higher than the energy of the electron, electron back to lower energy states of the composite, the excess energy in the form of a photon emitted. Emit a photon wavelength and energy difference of Eg related. Visible light region, mainly in the vicinity of the PN junction, the luminescence is due to the recombination of electrons and holes to release energy results. A semiconductor diode, electronic into semiconductor region to all away leaving the semiconductor region, will encounter resistance. From a simple principle, the physical structure of semiconductor diode simply from the principle, the number of electronic and return to positive physical structure of the source cathode semiconductor diode is issued by the equal. Diode common, in the event of recombination of electron hole pairs is, because the energy difference of the factors of Eg, the release of no photon spectra in the visible range.
The electrons in the diode internal way, can because of the presence of resistance and power consumption. The power consumption in line with the basic law of electronics:
In the formula: RN is N body resistance
VTH is a turn-on voltage of PN junction
RP is a P body resistance
The power consumption of the heat generated as the:
Type: t diode electrifying time.
In essence, LED is still a semiconductor diode. Therefore, LED in the positive work, its working process meets the above description. Electric power consumption for it it:
Where: ULED is the positive voltage at both ends of the LED light source:
ILED is the current through the LED
The consumption of electrical power is converted into heat release:
Q=PLED * t
Type: t for the conduction time
Electrons in P area and hole compound release energy, and not by the external power source to provide, but because the electrons in the N zone, in the absence of an external electric field, its energy level than the valence electron energy levels of P region of high Eg. When it reaches the P zone, and hole compound and become the valence electrons of P area, it will free up so much energy. The size of Eg is determined by the material itself, has nothing to do with the external electric field. The external power supply of electronic function is to push it to do directional movement, and overcome the effect of PN junction.
LED heat production has nothing to do with the light effect; does not exist a few percent of the electric power to produce light, the other a few percent of the electric power generating heat in a relationship. Through the derivation and the measurement of thermal resistance LED heat generation, thermal resistance, junction temperature of high power to understand the concept and theory formula, the actual package design, evaluation and application of products we can research of high-power LED. There is a need to explain the thermal management is a key problem in the LED products of luminous efficiency is not high at the present stage, fundamentally improve the luminous efficiency to decrease heat production is a fundamental solution to the need to develop the technology of every link, chip manufacturing, packaging and application progress of LED products.


Keywords for the information: PN junction,power LED,chip manufacturing

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