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2 in parallel

Discussion in 'Electronic Basics' started by Jif, Dec 22, 2003.

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  1. Jif

    Jif Guest


    Any pro could help.
    I have an adjustable volt and current Power supply (0-6V and 0-8Amp)

    I need 10-12Amp so would it be ok to parallel it with a smaller
    transformer such (110 to 6V and current of 5Amp).

    I can't read the installed diode # but what should be a good one to
    use with both transformers.

    Do I need to change anything else


  2. CWatters

    CWatters Guest

    It's not that simple.

    If you had two unregulated transformers and could connect them up out of
    phase so they pump into the same capacitor. That would allow you to take
    more current out of that capacitor before the ripple becomes too great for
    any subsequent load/regulator . BUT you said one source is a regulated
    voltage source....

    Think about what would happen if you try to connect two ideal voltage
    sources together and one was actually 6.1V and the other 5.9V. A current
    would flow from the 6.1V supply to the 5.9V supply. That current would be
    given by the equation.... I= (6.1-5.9)/R where R is the resistance of the
    wire you used to connect them together. If R is small I is very large. For
    this reason you should never connect ideal voltage sources in parallel (or
    current sources in series) or something interesting will happen.

    If you use two diodes to connect two ideal voltage sources together that
    would stop the current flow described above but it would also stop your
    circuit working as intended. This is because the output will be 6.1-0.7=5.4V
    which means the diode in the 5.9V supply will have 0.5V accross it and won't
    be conducting (at least not enough). The 6.1V supply will supply all the
    current and the 5.9V will supply none (or next to none).
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