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Voltage Doubler

Discussion in 'Electronic Basics' started by Jay, Nov 21, 2004.

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  1. Jay

    Jay Guest

    I have a design for which I need to generate a high DC voltage (more than
    400V). My power source for this voltage is the UK mains (230Vrms @ 50Hz).
    The way I see it is that I have 2 options. The first option is to use a
    step up transformer and a bridge. The transformer would need a ratio of 1:2
    (primary: 230V, secondary: 460V). As I cannot find any off the shelf
    transformers I would need to wind my own. My second option is to use a
    simple voltage doubler consisting of 2 capacitors and 2 diodes. The output
    of the voltage doubler would be something close to 460V DC.

    Out of the 2 options the voltage doubler seems the most straightforward.
    Some questions I have on this setup are:

    1) Does the transformer option offer any advantage over the voltage doubler?
    2) How can I determine the maximum current that can be drawn from the
    voltage doubler?
    3) Is connecting a voltage doubler directly to the mains a good idea?

    If you have any opinions or advice on this subject then please share them.

    Thank you.
  2. John Larkin

    John Larkin Guest

    There are two configurations. One makes +2*V to neutral, the other
    makes +V and -V. "Full wave doubler" and "Half-wave doubler."
    650, theoretically, a bit less with diode and capacitor losses. 230
    VRMS is 650 peak-to-peak.
    That's too complex to do for free. Bigger caps allow more current. How
    much do you need?
    Depends on the hazards. Might be ok if you're careful as to which line
    is neutral.

    What's the application?

  3. peterken

    peterken Guest

    might use an inrush current limiter to safeguard your setup if using 230Vac
    as input
    might think of fusing the output (PTC or fuse)
    be very carefull if using mains directly, for personal security
  4. Gareth

    Gareth Guest

    Actually, the voltage doubler could, depending on the current you draw
    and the size of the capacitors, give you an output of twice the peak
    voltage (230V is the RMS value). This could be closer to 650V.

    2 * 230 * sqrt(2) = 650V

    Don't forget that the capacitors could remain charged after you
    disconnect the mains. Be very careful.


  5. Looks like you could find a suitable transformer if you hunted around
    at some sources that carry old tube type radio equipment. They would
    have 460 volt output or close transformers........also.....couldnt a
    person use a microwave oven transformer and strip off some of the
    secondary windings till he got the desired output ???
  6. Steve Evans

    Steve Evans Guest

    Theyre not built for continuous duty. You could try two in parallel.
  7. Bob Masta

    Bob Masta Guest

    You might look for dual-primary transformers, designed to
    allow easy conversion between 120V and 240V systems.
    In normal use for 240V, you would put the two primaries in series.
    Instead, you can either use only one primary (if your load
    current is small compared to the transformer rating), or hook them
    in parallel with the proper polarity to get double the output

    Just a thought.

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  8. John Larkin

    John Larkin Guest

    Either case will make the transformer saturate and catch fire.

  9. Rich Grise

    Rich Grise Guest

    If you're rewinding it, just add a few turns to the primary.

  10. Rich Grise

    Rich Grise Guest

    Yes - it's less likely to kill you.
    It has to do with capacitor values and how much ripple you can tolerate -
    I'd have to look up the formula, but one of the experts probably has it on
    the top of his head.
    Usually no, unless you have very good isolation.
    OK. :)

    Good Luck!
  11. Bob Masta

    Bob Masta Guest

    Don't run it that hard next time! ;-)

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
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