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Car automotive 12V protection

Discussion in 'Electronic Design' started by [email protected], Dec 18, 2012.

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  1. Guest

    Please take a look at the schematic at the link below.

    * D1 is for reverse polarity protection
    * (C40) 10n/100V is to filter our very fast and low energy transients.
    * LC filter to attenuate load dump and other high energy transients
    * D2 is to clamp the high voltage spikes to 26V. The down side circuitry can tolerate max of 30V only.

    Is the schematic OK? Is it robust enough? 24V jump start protection is not needed.

    What should be the ideal cut off frequency for LC filter? with the present values I get Fc of 107Hz. It would be better if inductance is reduced as it results into smaller size but Fc is going up.

    Is the placement of D2 TVS diode fine? or should it be placed before the inductor L1? I thought by placing it after the LC filter would result into attenuated spikes for D2 to handle.


    -bhavj nk
  2. Guest

    Thanks for the feedback.
    Any reason why it won't pass load dump test?
    There is a 0.8V diode drop due to D1. So 16V working voltage for D2 should be fine unless battery voltage exceeds 17V. isn't it?
    Doesn't L1 limit current surges?
    The schematic symbol is incorrect. It is actually ignition switched power.
  3. Guest

    Thank you. Can look at changing D2 to 5KP series but doesn't the LC filter attenuate the spikes and make them easy on D2?
  4. mike

    mike Guest

    This is informative if you haven't seen it.
  5. josephkk

    josephkk Guest

    Look up load dump protection with a search engine. 80 V with equivalent Z
    of 0.01 ohm for half a second. What does arithmetic tell you about L1?

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