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Need a regulator or step-down circuit that steps a battery down from 7.2v to 4.7v

Discussion in 'Electronic Basics' started by IdeaMan, May 1, 2004.

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  1. IdeaMan

    IdeaMan Guest

    I want to step down a 7.2v lithium ion (Li-ion) camcorder battery to 4.7v to power my digital camera for long periods of
    time, can someone send me schematic via email or post one that fits my needs. Thank you for help with this. I forgot the
    email address: please send to of .
     
  2. Randy Day

    Randy Day Guest

    Simple and cheap; since you don't indicate a peak
    current requirement, you'll have to calculate a
    value for R.

    Any 3 diodes capable of handling the max expected
    current will work; yes, the diode polarity is
    correct as drawn.


    R
    ___
    7.2v in-|___|-+-----o ~4.5v out
    |
    V D1
    -
    |
    |
    V D2
    -
    |
    |
    V D3
    -
    |
    GND


    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de
     
  3. You come here to read the answer...

    There are tons of switchers available from various manufacturers.
    texasinstruments, lineartech, ...

    Rene
     
  4. amdx

    amdx Guest

    The diode circuit as drawn will only have about 2.1 volts output.
     
  5. Ken Moffett

    Ken Moffett Guest

    Why go to a shunt regulator? It wastes current in the diode string
    paralleling your load. A "series" diode regulator will only see the
    load current:

    Gnd---+7.2v--->|--->|--->|--->|---+4.7---Gnd

    This could be a mixture of standard silicon diodes and schottky diodes
    (with appropriate current and power ratings) to get the right voltage
    drop.
     
  6. Randy Day

    Randy Day Guest

    DOH!!!

    What was I thinking?
     
  7. Mjolinor

    Mjolinor Guest

    I suggest you were probably thinking " why did I drink so much beer last
    night" or similar.
     
  8. Tam/WB2TT

    Tam/WB2TT Guest

    I would put a light load of a couple of ma on the output of the diodes, so
    you don't hit the camera with 7.2V when you connect it. If you want to do it
    right, use an adjustable linear regulator.

    Tam
    .
     
  9. Ken Moffett

    Ken Moffett Guest

    Very true!
     
  10. Jamie

    Jamie Guest

    use a standard Post 5 volt regulator with 1 silicon diode in series on
    the output, this will give you a drop enough to put the final output to
    aprox 4.6 volts.
    P.S.
    the anode side will be connected to the Post output and the cathode
    would be your final out.. you may want to place a bypass cap at the
    output on the Post reg and cathode side of the diode.
     
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