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Blasting a Design with Power Mosfet Models

Discussion in 'Electronic Design' started by D from BC, Feb 13, 2007.

  1. D from BC

    D from BC Guest

    There's a wide variety of power mosfets all with complicated dynamics.

    Has anyone created a large modern mosfet spice library for LTspice
    with models from many sources...
    Then set up LTspice to try each mosfet model one after another with
    results all together on one graph. (If capable..)
    That way the optimum mosfet can be found for a given application..

    The mosfet library file can made smaller by only having mosfets with
    V,I, and P specs that suit the app.

    Something like that is going to have a long run time but the computer
    can run while I'm sleeping.. :)

    Comments...?
    D from BC
     
  2. If you use Spice power MOSFET models to select a suitable MOSFET
    for a design you are likely to be disappointed. That's because
    there's scarcely a perfect power MOSFET Spice model out there,
    and the few really good ones work well primarily only for certain
    aspects they were optimized to be good at. Most, if not all,
    are downright awful when compared against certain types of bench
    measurements. You'll be much better off studying datasheets and
    performing the relevant circuit calculations with the MOSFET data.
     
  3. D from BC

    D from BC Guest

    I'm just discovering that..
    I got the Infineon library and tried the SPA21N50 model (it's a
    subckt) in LTspice. All I get is singular matrix errors in my app.
    If I use a VDMOS mosfet model (LTSpice), it's ok.

    It should be possible someday to do a "run all mosfets" routine in
    spice..
    I was just curious if there was a lazy way to compare power
    dissipation between power mosfets operating above 100khz.

    Well... back to the traditional method...Math, datasheets and bench
    testing.
    Until the models and software get better :)

    D from BC
     

  4. You left out using the manufacturer's tables of their
    MOSFET properties to pick out candidate parts. These
    should have reasonably-low, but not too low Ron, and
    not too high Ciss, etc. Select a preferred package
    and see if it's available in stock anyplace. Etc.
     
  5. D from BC

    D from BC Guest

    Shopping for mosfets is like shopping for music...Not too hard and not
    too soft.. :)

    I do use the web tables to narrow down the search but there can be
    still many candidates per manufacture..

    Who's on top now in producing mosfets approaching the ideal high speed
    power switch? (+100W application). Maybe I can just focus on one
    manufacture...say Fairchild??
    D from BC
     
  6. D from BC

    D from BC Guest

  7. Henry Kiefer

    Henry Kiefer Guest

    |
    | Shopping for mosfets is like shopping for music...Not too hard and not
    | too soft.. :)
    |
    | I do use the web tables to narrow down the search but there can be
    | still many candidates per manufacture..
    |
    | Who's on top now in producing mosfets approaching the ideal high speed
    | power switch? (+100W application). Maybe I can just focus on one
    | manufacture...say Fairchild??

    As far as I can tell Fairchild is one of the topmost candidates (if cost is included).
    I recognized that every manufacturer specialized in specific subfields here.

    Would be a nice feature for LTspice to run libraries as batch for comparision.

    - Henry
     
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