Help in replacing bootstrap circuit with an isolated gate drive

Discussion in 'General Electronics Chat' started by ak52, Aug 23, 2016.

  1. ak52

    Thread Starter Member

    Oct 15, 2014
    145
    4
    Hello every one,

    I would like to upgrade an existing design of a bootstrap circuit with an isolated gate-drive to dive a high side nmos.
    I have drawn a rough schematic and would like a few sugesstion regarding the design.
    would the attached circuit work? also what should the values of R1 and R2 be?
    IMG_20160823_113343.jpg
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    That circuit won't work unless the 12V is referenced to the source of the MOSFET.
    That would likely require some sort of bootstrap circuit which you are trying to avoid.

    R1 should be small (10-50Ω) and R2 is not needed.

    You need a resistor in series with the input to limit the diode current.
     
  3. ak52

    Thread Starter Member

    Oct 15, 2014
    145
    4
    Thanks for the reply,is there any other alternative to this(bootstrap caps)?I read somewhere we can use isolated dc/dc converters to drive the high side fet,or some kind of pulse transformers.
    I donot have all the information required to implement either one of the above,could you please shed some light on the above.
    Thanks
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    Yes you could use an isolated DC/DC converter but that's a complex option.
    A pulse transformer will work for a limited range of duty-cycle.
    What's wrong with a bootstrap circuit using caps?
     
  5. ak52

    Thread Starter Member

    Oct 15, 2014
    145
    4
    Nothing wrong with using a bootstrap circuit Everything works perfectly,
    I'm just exploring new ways to turn on a high side MOSFET.
    In the above circuit ,would it be ok if i generate the 12v from a switching regulator(LMR62421) referenced to the source of the MOSFET?
     
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