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N phase power filtering

Discussion in 'Electronic Basics' started by [email protected], Mar 16, 2007.

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    Suppose you have n "equally spaced" rectified sinusodial voltage
    sources. If you add them up you get a smoother voltage. I remember
    seeing that Asus used this on some of its motherboards and I'm curious
    as to if it can be used in high current power supplies? Even three
    phase seems to be a huge improvement in the capacitive filtering
    needs.

    Is this practical?

    Looking at this site

    http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

    It says that I would need .1F or more just for a 15A with a fixed
    voltage and its only good up to 1V. For my ps I want to have a
    variable voltage source which might be from 2V to 20V. So I might be
    dropping ~20V across the regulator at 10A. This is only 200W and I was
    going to use several transistors to split the current load.

    http://focus.ti.com/lit/ds/symlink/lm317.pdf

    The very last schematic is for high current regulation and I was going
    to duplicate the stage with several TIP120's and BJT's. I think I can
    run those stages in parallel to reduce the power dissipation on the
    TIP120's? I might have to mess around with the resistor values but
    I'll try and figure that out later.

    The real issue is the supply filtering that I'm worried about. I have
    a few 3300uF caps but even then it would take about a dozen or more by
    what that web site says and even then I wouldn't get very good
    regulation.

    I was wondering if there are alternative methods to filtering besides
    using caps that are not more expensive for high currents.

    What I remember from the ASUS motherboard was that it had a series of
    small caps around the cpu socket and it was something like 8 phase for
    smoothing over the voltage to the cpu. I can't seem to find any
    information on the subject though.

    Thanks,
    Bob
     
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