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Thread: Relay for DC/DC converter shutdown

  1. #1

    Relay for DC/DC converter shutdown


    we plan to use a relay to shut down the DC DC converter in our car. To shutdown the converter one needs to connect a PC (primary control, typically 5.25 V) pin to the HV- contact.

    For this purpose I am searching for a relay. I have one in mind but I am not sure if it fits the rules. (See attached screenshots)

    The relay has a distance of 20-3.5 = 16.5 mm which is more than the required 12.7 mm. But can it withstand 425 V from the tractive system between contacts and coil? Max. switching voltage is only 300 VDC but the dielectric can handle "5,000 VAC, 1 min between coil and contacts".

    The 5,000 VAC sound good, but that about VDC? Is this relay able to do the job?

    Attached Images
    Last edited by inspire; 12-13-2013 at 01:20 PM.

  2. #2
    Dielectric strength is the maximum voltage you can apply between two points on a relay for a given time. Also....you've got everything there for you to make the judgement call. Is it rated high enough? Will it work? This seems like a question you need to answer.


    the maximum RMS Vac voltage. I went and looked at the definition. This is important!
    Last edited by jlangholzj; 12-14-2013 at 02:37 PM.
    South Dakota State University Alum
    Electrical/Daq/Engine/Drivetrain/Tire guy '09-'14

    Go big, Go blue, Go JACKS!

  3. #3

    why do you want to use a relay for this? As I understand, you want to pull 5V25_ISO to PACK-, controlled isolated from LV side to turn on the DCDC with an Enable Pin on HV side - correct? Why canīt you do this by a cheap optical coupler? This would also be easier to supply from a secondary battery used for startup.

    Another question I got is, whatīs the DCDC input current when turned off this way? Most DCDC I know will still be in the range of 2mA which will drain your batterie when stored significantly.

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