Like traditional light sources, LED flood light (LEDs) also generate heat during operation, depending on the overall luminous efficiency. Under the action of external electric energy, the radiation of electrons and holes recombines to produce electroluminescence, and the light radiated near the P-N junction needs to pass through the semiconductor medium and the package medium of the chip itself to reach the outside (air).
Comprehensive current injection efficiency, radiant luminescence quantum efficiency, chip external light extraction efficiency, etc., finally only 30-40% of the input electrical energy is converted into light energy, and the 60-70% of the energy is mainly caused by non-radiative recombination lattice vibration. The form transforms heat.
The increase in the temperature of the chip enhances the non-radiative recombination and further weakens the luminous efficiency. Because people think subjectively that high-power LEDs don’t have heat, they do. A lot of heat, so that problems occur during use.
In addition, many people who use high-power LED flood lightfor the first time do not know how to solve the heat problem effectively, which makes product reliability a major problem. So, is there any heat generated by the LED? How much heat can you produce? How big is the heat generated by the LED?
The heat production of LEDs has nothing to do with light efficiency. A few percents of the electrical power does not produce light, and a few percent of its electrical power creates a thermal relationship. Through the understanding of high-power LED heat generation, thermal resistance, junction temperature concept and theoretical formula derivation and thermal resistance measurement, we can study the actual package design, evaluation and product application of high-power LED.
It should be noted that thermal management is a key issue at the current stage of low luminous efficiency of LED products. It is the bottom line to fundamentally improve the luminous efficiency to reduce the generation of thermal energy, which requires chip manufacturing, LED packaging and application product development. Advances in technology at all stages.
It has been found in the LED industry that the use of a constant voltage source drive does not guarantee the uniformity of LED brightness and affects the reliability, lifetime and light decay of the LED. Therefore, super bright LEDs are usually driven by a constant current source. The constant current supply eliminates current changes caused by forwarding voltage changes.
This produces a constant LED brightness regardless of the forward current. It is easy to generate a constant current power supply. It is only necessary to adjust the voltage across the current sense resistor without adjusting the output voltage of the power supply.
Compared with the performance of the current main high-power IED driver control chip, when applying the high-power IED driver control chip, it can be selected according to different applications:
1. When higher power is required, the power device can be selected without the controller integrated in the chip, so that the power device can be separately selected according to the actual power requirement.
2. When a higher conversion efficiency is required, such as a portable device, a drive circuit of a switching power supply type can be selected.
3. When applied to equipment with high reliability, you can choose a chip with comprehensive control functions such as temperature protection and fault alarm.