AC Capacitive Voltage Divider - Help?

Discussion in 'The Projects Forum' started by Shike, Jun 29, 2008.

  1. Shike

    Thread Starter New Member

    Jun 29, 2008
    2
    0
    Hey everyone, I'm new here and was hoping I could get some help on something I've been trying to figure out.

    Recently I read up on using a capacitive divider to make a simple PSU. I was wondering if anyone could confirm if the circuit I'm thinking of will work.

    In general, it'd look like this:

    [​IMG]

    Would this be feasible at providing +30V with upwards of 10A after rectification, and is there any safety issues I should be concerned with besides working with mains?

    I plan to expand with fusing and further filtering if it's given the ok.

    Thanks in advance,

    -Drew ;)
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You dont need the 250 and 750uF capacitors, remove them. I would recommend you to use a center tapped transformer to have a bipolar power supply.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It is not a safe design. If the 250uF cap should short, the remainder of the circuit would be connected to the mains. Caps frequently short out when they fail.

    You should use a transformer, or a "buck" design.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I would also replace the 10pf caps with much much larger caps. I would add regualtors after said caps.
     
  5. Shike

    Thread Starter New Member

    Jun 29, 2008
    2
    0
    What would you suggest for a buck design then that's capable of putting out +20V-35V and up to roughly 10A?

    I'm trying to build a ~500W/channel class A/B amplifier and transformers for this are generally expensive and cumbersome. I know I've seen sub plate amps with even more power without transformers, so I know it can be done. :confused:

    Actually, the goal there was to use reactive capacitance to provide a load and step AC down without the need of a transformer.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    There are two strong disadvantages to using dividers to "step down" a voltage. One is waste. The other is a changing load can have a large effect on the desired voltage.

    A much better use of dividers is for measurement - a negligible amount of power is needed and the load is fixed.
     
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