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electronics inside car headlight

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car headlamp electronics

hello,

i have to design smps led driver to go inside the enclosure of a car headlight.

with the lamp OFF, (yes, "off"), on a baking hot sunny day of 35 deg C, how hot will it be inside the lamp enclosure? (roughly)

-assuming the headlight is in the sun and not shaded.

am i right in saying that the "greenhouse" effect will mean its going to be about 80 deg C, even with the electronics OFF ?
 

inside a car headlight

80C is probably a good guess if in bright sunlight for a long time. The exact temperature depends on so many variables it would be almost impossible to calculate.

Don't forget the reason for sealing a normal headlight is to prevent thermal shock of cold air or moisture reaching the extremely hot glass of the lamp. Also to keep dirt out of the lens of course.

If you are using LEDs instead of an incandescent lamp, the temperature will be much lower and the LEDs will probably have in-built lenses of their own so venting the enclosure is a viable option.

Brian.
 

inside a headlight

thankyou Brian,

but i can assure you that all our LED enclosures for cars are sealed.

I was referring to the temp with the lights off BTW
 

headlight inner temperature

Ambient temp of 35 may not raise the temperature too high to the tune of 80 celcius. Head lamp inner surfaces are high reflectivity and may not absorb too much of radiation from outside. The inner part of the head lamp assembly will certainly be cooler than a black seat cover of a two wheeler in sunshine. Blac dull surfaces are good absorbers of radiation.
 

electronics inside the car

The problem with conventional parabolic reflectors is they focus heat. The facia glass is patterned which will prevent one really hot spot developing but probably produces many smaller hot spots instead. These will of course be mobile as the sun angles change, either by passage of time of because the vehicle is moving.

I would think 80C is quite a likely scenario at a hot spot but it could be considerably cooler in an un-focussed area.

LEDs should function as high as 80C although at reduced efficiency but its pushing the limits of temperature for a working SMPS under load. Of course, most people would not be using the light in bright sunshine anyway.

Brian.
 

temperature inside headlight

80 degrees C is very hot for humans.
Billions of people in India and China live in temperatures almost as hot without any air-conditioning.
 

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