Heat dissipation scheme of high power LED street lamp in road lighting

To create a conservation oriented society has become the consensus, but the comprehensive efficiency of high pressure sodium lamps, road lighting is still a lot of use is not high, only about 70%, and the color index is low, the night lighting dim feeling, is not conducive to motorists and pedestrians on the target and obstacle resolution, have a certain influence on the road traffic safety.

At present, the luminous efficiency of high power white LED (>80lmPW), service life (>50000h), light output characteristics, color performance (75 ~ 80), color selection and adjustment of green and non pollution and so on has unique advantages, according to city road lighting design standard, convenient and flexible design in line with the requirement of light output, satisfactory lights, become a new quality light source with strong competitiveness. In the key technologies of LED street lighting, the design of heat dissipation is a very important part, and it is also one of the technical bottlenecks that restrict its wide use. In other words, the quality of the design will directly determine the performance of LED street lamp performance indicators and the actual application of the success of the promotion.

Heat dissipation scheme for high power LED

High power LED light source is the basic form of LED street lamp, electric current P chip light conversion efficiency is very low, only 15%~20%, the physical size of the chip is 1 ~ 6125mm2, the area is very small, the power density and heat a large, the power consumption in the 80%~85% will be converted to heat and need to be released, and the chip temperature exceeds a certain value, the emitting wavelength becomes longer and the color shift will lead to decreased chip light output efficiency and service life reduce many ask. Therefore, in order to ensure the normal use of high-power LED, heat is the first key issue to be solved.

The influence of temperature on LED and the primary heat dissipation scheme

The junction temperature of high power LED chip is closely related to the flux and the life. In order to heat up to 80%~85% of the heat, LED in the package when the use of a scientific design of thermal processes and efficient packaging process. Through the application of high thermal conductivity materials (internal heat sink) to ensure that the heat generated by the chip can be derived, making the package after forming LED has good thermal conductivity and thermal energy performance.

Relationship between LED junction temperature and luminous flux and life

Based on the working characteristics of high power LED, the junction temperature is directly related to the size of the flux and the length of service life.

Figure 1 shows the relationship between the junction temperature and luminous flux (Figure 1 (a)) and service life (b) of an international brand LED chip.

As can be seen from Figure 1, with the increase of the junction temperature of the LED chip, the luminous flux of the output is falling down regularly, and the service life also shows a trend of rapid decline. So try to maintain the temperature of the chip in the allowable range, is the first to solve the key technical problems of LED applications.