Before the LED solar lamp design

To reduce the power consumption of LED headlamps, only through the first time in the light distribution control to reduce the white LED light loss, and in a few places to obtain the desired light distribution characteristics is not enough. In addition must also be able to use white leds in efficient condition. And one of the key lies in how to make white LED the heat generated by the release of heat dissipation design. In fact, the input power of white leds are mostly into heat energy. If the temperature rise of these heat make the white leds, the luminous efficiency will drop, increase calorific value. They would be in this way, luminous efficiency decline further, a vicious cycle of calorific value becomes larger.

figure 1: thermal design of headlamp locate

figure 2: LED headlamps modeling

the city of light industry in LED headlamps analytical simulation using the thermal fluid flow in the design of heat dissipation technology. In headlamps analytical simulation using thermal fluid flow in the design of heat dissipation is not rare, however, this is in the upstream design process, also is the material such as resin, convection, and heat resistance of components in the design of layout and the design of the fin base using the simulation technology, the efficient heat dissipation design.

the headlamps thermal design through the foundation design, detailed design, trial production test and design changes after the four process is applied to the products ( FIG. 1) 。 According to the city of light industry is responsible for the thermal design of kikuchi and heavy ( Develop the department core engineering simulation class senior experts, parsing technology senior engineer) Introduction, in the foundation design, while simulation model with difficulty is not high, when the florist is not much, but the information obtained by calculation is accounted for as much as 60% of the entire design ( FIG. 2) 。 The LED headlamps by using simulation technique in the foundation design, the effect significantly. Due to the separation of light and heat, so can be applied to the foundation design, the why to use simulation in foundation design? The answer lies in the LED headlamps's heat flow characteristics. From the point of white leds as the starting point of the cooling path, its flow path is:

as a heat source of the LED chip left

with the installation of the LED chip packaging substrate

left

the install base board heat spread to the whole packaging underside of thermal diffusion

left

radiator ( Heat sink, etc. ) The connection of the

left

radiator ( Heat sink, etc. )

left

the external air down, so to speak, from the white leds to the outside air the whole path are series state ( Figure 3) 。 And halogen lamp and HID lamp light source have been established the cooling path is rather complicated. The reason is that the light source itself to outside air radiation light and heat at the same time. That is not in a simple serial state. Therefore, its foundation in the design of the cooling model is relatively complex, only in the process of trial test and design change using simulation.

figure 3: use white LED headlamp and thermal path ( Image by city light industry

the LED light from the surface to the external radiation, air and heat from the back to the headlamps shell radiation, light and heat in a state of separation. Due to the LED on the surface of the thermal radiation can be ignored, so the heat flow path as mentioned above. So, the foundation design of modeling simple, analytical simulation can implement thermal fluid. With simulation results, the LED headlamps, thermal desorption implements the calculation precision of plus or minus 2 ℃, only two days to finish the heat dissipation design.

simulated on heat sink, etc on the basis of design and master some rough shape and basic performance, city light industry trial-manufacture 1 products. Then after the best shape and small part of design, entered the final shape of the cooling performance to confirm the mass production of product design. Because of the high precision of calculation, and therefore probably next time and later don't manufacture products used in mass production. This is the first time the city light industry production LED headlamps, therefore still manufacture the actual product. In addition, the heat sink and light distribution control using mirrors, etc in the design of thermal simulation takes about two and a half hours, and white leds only one and a half hours to the heat sink. Will the heat sink is divided into four parts, such as about 700000 grid was calculated.

lower heat sink and the connection of the thermal resistance of

according to the city of light industry is introduced, the design of LED headlamps, heat dissipation, also discusses the heat dissipation fin links in the path and the design of the fin itself. The reason is that the LED product is LED chip and heat diffuser are closed on the white leds package from the procurement of LED manufacturers, under the condition of headlamps producers cannot change.

in fin connection and heat sink, the problem to be solved is how to reduce the connection and the thermal resistance of heat sinks itself. To reduce the connection of thermal resistance, especially the important thing is: ( 1) Use wire clip, spring and screw to keep white leds press the stress on the radiator and uniform contact area; ( 2) Considering the cooling paste and thermal conductivity, and the associated with the degradation of time and area, thickness. In terms of heat sinks, need not combined cooling fan, and do not affect the size and shape of the headlamp design fluctuate. The thermal design, design the premise is to each white leds have 9 w in the 10 w power of the input into heat. Due to the maximum rating of white leds for 130 ℃ ( The surface temperature of the white leds) , so is according to any purpose design won't be up to 130 ℃.