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Got Fet?

Discussion in 'Electronic Design' started by Yzordderrex, Oct 12, 2005.

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  1. Yzordderrex

    Yzordderrex Guest

    I need a 1200v mosfet near a half amp or amp.

    This is for a flyback that runs off of 600v mains for motor drive. By
    the time I fit in decel limit override and overvoltage trip point the
    bus can get up to about 1000v. I figure I will have to pay attention
    to flyback voltage and I might be able to squeek by.

    Package in TO-220 or TO-247 might be best.

    FYI Sanyo makes a nice 1500v part, but cost$. I also see that ST micro
    makes 1500v mosfet now too.


    regards,
    Bob
     
  2. Yzordderrex

    Yzordderrex Guest

    Ok, which one?

    regards,
    Bob
     
  3. I presume this is just a few watts to power the drive itself? Why not
    use a BJT ?


    Best regards,
    Spehro Pefhany
     
  4. 2SC(something-or-other) would be a good start. 5148 maybe (1500V), but
    I can't do your shopping for you. Try Hitachi, Toshiba etc.


    Best regards,
    Spehro Pefhany
     
  5. Yzordderrex

    Yzordderrex Guest

    I'll go poke around some. I don't really have a lot of hope for
    bipolar. I don't think the TI UC38C44 current mode power supply
    controller will like to drive it very well. Probably not much gain on
    the part. I got a slick design that runs good with a Topswitch and a
    800v fet on top, but boss says it takes up too much room. Other design
    uses 1500v Sanyo part but boss says too expensive.

    regards,
    Bob
     
  6. You could also consider a hybrid emitter switched biplar transistor
    (ESBT).. don't know about the cost though. They are specifically
    targetted at your type of auxilliary supply application.

    Eg: http://www.st.com/stonline/products/literature/an/11259.pdf


    Best regards,
    Spehro Pefhany
     
  7. Jim Thompson

    Jim Thompson Guest

    Love it! That TL431 plus opto-coupler load-side sensing could be
    straight out of my mid '70's SMPS's that I designed for GenRad.

    ...Jim Thompson
     
  8. Yzordderrex

    Yzordderrex Guest

    Spehro,

    I've got some of them ST Micro parts in my toy box. Got eng samples
    last year. I'll check em out.


    There's probably a few billion power supplies using that feedback
    scheme. I've put at least a million out there by myself. Thanks for
    the circuit if it's the one you did Jim.

    regards,
    Bob
     
  9. I forget who does it, but they even make optos with the TL431 built
    in.


    Best regards,
    Spehro Pefhany
     
  10. Jim Thompson

    Jim Thompson Guest

    I have to dig thru my paper archives but, IIRC, my version used
    back-to-back opto-couplers to narrow the range of loop gain variation,
    and had soft start and current limit as well. This was in the PSP
    (Portable Service Processor) testers, which had 128 (again IIRC, or
    was it 256 :) of my custom designed pin driver chips.

    ...Jim Thompson
     
  11. Jim Thompson wrote...
    Do you know who designed the TL431 chip?
     
  12. Jim Thompson

    Jim Thompson Guest

    I don't know. But I fell in love with that chip when it first hit the
    market... some many uses.

    ...Jim Thompson
     
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