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  • LED Hedlight thermal management

    Hello to everyone! This is my first post on "HID Planet". I visit this site for a very long time and since i prepare LED retrofit project, i decide to register and publish my work. I also need help with thermal management.
    I would love to see how exactly thermal management is configured in LED headlamps! Active cooling, where air goes in and where goes out. I know there is, in most cases, 2 fans. But i didn't find anywhere on the net, some details about air circulation.
    Does anyone here know how active cooling in Full LED Headlamps work? Thanks!

  • #2
    Welcome to HID Planet, at least as a poster. It really depends on the projector. Some are passively cooled with heatsinks. Some have fans. Headlights are sealed so air doesn't move in and out of the headlight, just around the inside. Is there a specific type of headlight you are referring to?

    2000 Toyota MR2 Spyder
    2017 Lexus CT200h F Sport

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    • #3
      as halo said, there's a lot of versions that are passively cooled. another thing to watch out for is that there is now thermally-conductive plastics, so what appears to be just part of the housing can now be part of the heatsink design...
      The time you enjoy wasting, is not wasted time

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      • #4
        I get two "Valeo" BiLed module from Mini 2017. Someone from this forum said they are "fanless" design. They are without fan, at least fan is not part of module like other BiLed module with fan. I drive bmw e46. I have extra pair of headlights. They are not complete but...ok for some experiment. My intend is to retrofit those BiLed module. So i need to think about cooling. I don't have original driver so i will make them. They will be based around Linear Technology (Analog Devices) LT3755. NTC resistor is included in circuit so there will be thermal protection. Low beam consist of 3 pcs Osram oslon submount 1x3 array and High beam is from 2pcs. For one low beam i need one driver, around 29Volts and 1.0- 1.4 Amp (i am not sure, i must find optimal value, brightness vs temperature)! Also for high beam one driver, same for other side!
        I was found some audi headlight diagram. There was air intake on the bottom of the headlight housing. Filter infront of fan. Air outtake at the back of the headlight. That kind of active cooling seems very good and logical. If air just circle inside housing- what cool it?

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        • #5
          Huh I've never seen vents on a headlight for fans. But I've also never examined Audi headlights. I'm pretty sure all headlights containing the Koito Bi-LED (AKA most of Toyota and Lexus' lineup) are sealed.

          2000 Toyota MR2 Spyder
          2017 Lexus CT200h F Sport

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          • #6
            Originally posted by noz-25 View Post
            I get two "Valeo" BiLed module from Mini 2017. Someone from this forum said they are "fanless" design. They are without fan, at least fan is not part of module like other BiLed module with fan. I drive bmw e46. I have extra pair of headlights. They are not complete but...ok for some experiment. My intend is to retrofit those BiLed module. So i need to think about cooling. I don't have original driver so i will make them. They will be based around Linear Technology (Analog Devices) LT3755. NTC resistor is included in circuit so there will be thermal protection. Low beam consist of 3 pcs Osram oslon submount 1x3 array and High beam is from 2pcs. For one low beam i need one driver, around 29Volts and 1.0- 1.4 Amp (i am not sure, i must find optimal value, brightness vs temperature)! Also for high beam one driver, same for other side!
            I was found some audi headlight diagram. There was air intake on the bottom of the headlight housing. Filter infront of fan. Air outtake at the back of the headlight. That kind of active cooling seems very good and logical. If air just circle inside housing- what cool it?
            The fanless Valeo biled is their Gen II module, as they call it. However there are 3 versions to my knowledge and all carry Nichia chips. Each version has a slightly different customized Nichia chip.

            I have all 3 bileds and I have two different original drivers. I have not been able to power them up (referring to BMW versions not Ford/Lincoln biled) as I believe Valeo and BMW have purposely added a secondary circuit from an external control module that controls the main function.

            I look forward to your progress for building the driver. If your biled version is the latest Gen II then it should have these Nichia chips...



            And the closest match I can find on the Nichia product page is the NC3W321A. Hopefully the datasheet will help you spec out your driver.

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            • #7
              evo77 Thanx for Your help! About LEDs used in these modules...when i first get them, i start to google and search trying to identify them.
              They are in my opinion most similar with Osram Oslon Submount KW C3L5L1.TE. I will measure size of LEDs again and compare it with Oslon and Nichia datasheet. However what ever model it is, they are all (1x3 array) very similar. My plan is to drive them with 1.0 Amp and increase to 1.2 or 1.4 Amp depending on the temperature. Do You maybe know some good source for technical staff, design, thermal management of OEM LED headlights? I would love to learn how do they do it! Thanks!

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              • #8
                I can assure you they are indeed Nichia chips, not Osram. But please feel free to take your measurements and compare them to both datasheets.

                Nichia dies have a full face phosphor coating with barely any gaps. Osram Oslon series dies always have a signature corner notch to identify them. Plus they have a gap in between each die. And also the cathode/anode pads are different too.

                OEMs do not reveal their secrets to building LED headlamps because it is a competitive market. There are principles and basics that they all follow but being innovative is where the lighting suppliers stand out and snatch that big contract with the auto maker. You may find some generic material on the web if you google but most of it may be a few years old and LED technology moves so rapidly that the information is outdated. Detailed and thorough papers on the subject you will have to purchase. You can find papers on SAE.org for a fee. Perhaps even on ECE website (not sure about this one).

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                • #9
                  Whether your selected LED system has active cooling or passive cooling, your focus should be how to replicate to secure similar convection passage.

                  General tendency of passive cooling LED system in vehicle headlamp uses wider pitch, tall fin to enhance chimney effect to achieve higher convection coefficient.
                  Addition to that, some of heatsink has something like alumina ceramic coating, other oxidized metal coating to enhance far inferred radiation to achieve better cooling capacity.

                  Koito Bi-LED projector with cooling fan is designed to be adopted in many application, it can be said somewhat standardized core parts within their group and it should be one of easier system to retrofit.
                  As manufacture designed system to be universal rather than application specific LED array system.

                  It's best to use with original driver of course, as many of OEM LED system may be using custom chipset, which exact data sheet may not be available to public.



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                  • #10
                    evo77 and upashi Thanks a lot for Your help and info! For driver i wil use all new components from Arrow. Most of them meet "automotive requirements"!

                    evo77 i didn't understand You are sure that LEDs are Nichia! Since You are, i fully trust You. I'm grateful You helped me! Your expirience and knowledge mean a lot to me! upashi thanx a lot for Your reply. In next period of time i have lot of work to do, lot of retrofiting! Before i order all components i need for LT3755 driver, i was thinking is it better to buy finished BiLed projector!? But numbers show that these OEM modules have much stronger output! I hope i will suceed with this project!

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