electric vehicle LED's...hard project...

Discussion in 'The Projects Forum' started by lurker6, Sep 10, 2009.

  1. lurker6

    Thread Starter New Member

    Sep 8, 2009
    My back ground is Mechanical and PCB. ( I need EE help)
    I hope to make a custom led taillight for my father-inlaw.
    He is even making custom lens covers with his logo on them.
    It will have to be a flex on aluminum board. (expensive but he has a budget)

    I need help with the schematic...
    I have spec'd out the LED as - POWER TOPLED with lens OSRAM
    PN-LS E63F-DBFA-1-1 Super RED

    data sheet-
    http://catalog.osram-os.com/catalogue/catalogue.do;jsessionid=44739A0847BDBF2B4CBF49FC37 88F45B?act=downloadFile&favOid=020000030001d405000100b6

    Vehicle input Voltage is 11-16V
    So I understand each led wants 2.15V at 50ma.
    I understand how to do this with simple resistors.
    I understand the simple constant current circuit with a lm317 for each
    led or led string.

    Both of these circuits are not how professionals do it?
    I have seen other production taillight units.
    I have not seen the schematics but i have looked at the boards. I will get a pic and post it soon. but it appears to be 2 resistors/ 1cap and 1or2 sot-23 packages near each led....only 2 pin connector to the board.

    Really just looking for some in-site on a professional ev efficient design which should only mean expensive parts. The quick and dirty circuits are everywhere but im looking to recreate an audi type design into a custom forum factor..

    willing to trade skill for skill

    the forum is very cool

    Last edited: Sep 10, 2009
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    It's probably a current regulator, an LM317 can be wired this way.
  3. SgtWookie


    Jul 17, 2007
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    I've seen some commercial LED drive circuits that use an inductor. I've not traced through them, but the obvious deduction is that they are a switched-mode constant current driver.

    A simpler version would be an oscillator to do a simple form of PWM. That would reduce power dissipation and increase efficiency.

    Most LEDs are rated for at least 10x continuous current in sufficiently short bursts.
    The efficiency also increases as drive current increases.

    10% duty cycle drive at 1KHz or so typically gives twice the light output as steady current with the same mean value, which is one of the reasons for using pulsed or PWM drive.

    For vehicle lighting, I believe they use multiple independent drive circuits for the LED chains, so the light still visibly functions in case of a component failure.

    Remember in many places it is illegal to drive a vehicle without fully working lights (hence the requirement to carry spare lamp bulb sets).

    You cannot change the LED assembly, so it must be fail-safe.
  5. lurker6

    Thread Starter New Member

    Sep 8, 2009
    Thanks for all your comments and suggestions. To further explain...
    This will be a Flex on Aluminum Circuit (pic to Follow) so it will be a single sided design. (no through-hole parts)
    There are 9 LEDs in the upper oval and 13 LEDs on the lower oval.

    This is replaceable just like current led tail lights (having trouble getting pics of this type of system). Most new cars are with leds are done this way.

    New question:
    see attachment

    Does this circuit accomplish the task for a given 11-16V input...?
    Does it need some reverse protection..?


    Last edited: Sep 11, 2009