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DC-DC converters

Discussion in 'Electronic Design' started by [email protected], Mar 30, 2006.

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  1. Guest

    What are the pros and cons of the various DC-DC step-up converter
    designs (say, 12V to 18V, 50 watts total)?

    I could use one for my old laptop (366 mhz, it wants 18V @ 2.7A).

    I went to this website:
    http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/co...


    and I see there are CUK converters, Boost, Buck Boost, etc.

    My intuition tells me there are trade-offs in efficiency, ease of
    construction, cost, consistency and durability between each of these
    methods.

    Any suggestions guys?
     
  2. John_H

    John_H Guest

    Your link was cut off - try using "tinyurl.com" to give us something to look
    at.

    I haven't seen a design touted as a Cuk converter outside of textbook pages;
    the idea is great for reducing ripple: input, otuput, or both.

    Are you in need of general learning? A single device? A design-your-own
    1k/mo production solution? Is your need non-isolated?
    _________________________________________
     
  3. John_H

    John_H Guest

    Your link was cut off - try using "tinyurl.com" to give us something to look
    at.

    I haven't seen a design touted as a Cuk converter outside of textbook pages;
    the idea is great for reducing ripple: input, otuput, or both.

    Are you in need of general learning? A single device? A design-your-own
    1k/mo production solution? Is your need non-isolated?
    _________________________________________
     
  4. Guest

    Eek! Well, basically the one at the end here:

    http://en.wikipedia.org/wiki/Dc-dc_converter



    I'd like to make this a learning experience. (Otherwise, I'd just buy
    one.) And hopefully something that can provide 50W, steady enough so
    as not to fry my laptop...

    A single device, I'm still a beginner as far as electronics are
    concerned... definitely not 1k/mo.

    Then again, I don't even know what I need to learn! What are the
    advantages of Buck vs. Boost, etc? Cuk is out? Why?

    I remember a DC-DC converter on the back of Forrest Mims' 555 handbook,
    but it needed a Radio Shack 120VAC/12VAC stepdown transformer. (I
    remember building it many years ago, and I only got about 50V out of
    it. Was expecting 120V...)
     
  5. Ken Smith

    Ken Smith Guest

    Flyback booster:

    Low parts count. Uses "off the shelf" parts. Vout must be more than Vin.
    Wide supply range. Not good for multiple outputs.

    Flyback isolated:

    Lowish parts count. Vout vs Vin can be anything. Wide supply range. May
    need a largish core for a given power. Large ripple currents. Fair
    tracking on multiple outputs.

    Buck:

    Low parts count. Off the shelf parts. Vout must be less than Vin. Not
    good for multiple outputs.

    Non-isolated Cuk:

    Good if you want to invert the sign of the voltage. Off the shelf parts.
    The coupling capacitor can be troublesome. Can make equal +/- supplies
    with good tracking.

    Isolated Cuk:

    Much like isolated flyback without the large ripple currents. Good
    tracking on multiple outputs. Special magnetics.

    Single ended forward converter:

    Use a flyback.

    psudo-squarewave, forward, voltage fed, isolated:

    Vout vs Vin can be almost anything. Low output side ripple currents.
    Small cores for a given power. Poor tracking on multiple outputs.
    Narrower Vin range.

    Psudo-squarewave, forward, current fed version:

    Same as above but low input ripple. Fair to good tracking on multiple
    outputs.

    Resonant isolated:

    Kind to switching parts. Needs more parts.
     
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