The creation of a conservation-oriented society has become the consensus of the people. However, the overall efficiency of high-pressure sodium lamps that are still widely used in road lighting is not high, only about 70%, and the color rendering index is low, and the night lighting feels dim, which is not conducive to car driving. The resolution of targets and obstacles by personnel and pedestrians has a certain impact on road traffic safety.
At present, high-power white LEDs are unique in terms of luminous efficiency (>80lmPW), service life (>50000h), light output characteristics, color rendering performance (75-80), color temperature selection, controllability, and green pollution-free. Advantages, according to the requirements of urban road lighting design standards, convenient and flexible design of satisfactory street lights that meet the requirements of light output, and become a new high-quality light source with strong competitiveness. Among several key technologies that determine LED street light applications, heat dissipation design is a very important part and one of the technical bottlenecks that restrict its ability to be widely used. That is to say, the quality of the heat dissipation design will directly determine the performance and performance of the LED street lamp and whether the actual promotion and application can be successful.
High-power LED cooling solution
High-power LED is the basic light source that constitutes LED street light. The current chip P-light conversion efficiency is very low, only 15%~20%, the physical size of the chip is 1~6125mm2, the area is small, the power density and heat generation are very large. 80%~85% of the consumed energy will be converted into heat energy and need to be dissipated. When the temperature of the chip exceeds a certain value, the wavelength of the light becomes longer and the color is red-shifted, which will lead to a decrease in the light-emitting efficiency of the chip and a decrease in the service life. Wait a lot of questions. Therefore, to ensure that high-power LEDs can be used normally and effectively, heat dissipation is the key problem that needs to be solved first.
The effect of temperature on the LED and the primary cooling solution of the package
The junction temperature of high-power LED chips works closely with the luminous flux and lifetime. In order to dissipate up to 80% to 85% of the heat, the LEDs are packaged with a scientific thermal process design and a fruitful packaging process. By applying a highly thermally conductive material (internal heat sink) to ensure that the high heat generated by the chip can be smoothly exported, the LED after the package molding has good heat conduction and heat dissipation performance.
LED junction temperature and luminous flux, life relationship
Based on the working characteristics of high-power LEDs, the junction temperature has a direct interest in the size of the luminous flux and the length of the service life.
Figure 1 shows the relationship between junction temperature and luminous flux (Figure 1(a)) and lifetime (Figure 1(b)) for an international brand of LED chips.
It can be seen from Fig. 1 that as the junction temperature of the LED chip increases, the luminous flux of the output decreases regularly, and the service life also shows a rapid decline. Therefore, trying to maintain the temperature of the chip within the allowable range is the key technical problem to be solved first in LED applications.
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