Power Supply Schematic

Discussion in 'The Projects Forum' started by tracecom, Nov 14, 2012.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
    I am planning to build the PS shown attached. Anything I should change or be aware of?

  2. MrChips


    Oct 2, 2009
    I would use a bridge rectifier and ground the center tap of the transformer secondary.
  3. tshuck

    Well-Known Member

    Oct 18, 2012
    Be aware that CR3 isn't connected to anything :)

    Why not rectify your voltage to a full wave rectifier instead of half wave?
    Especially considering you are using a center-tapped transformer...

    Edit: Mr. Chips has beaten me again!
    Last edited: Nov 14, 2012
  4. MrChips


    Oct 2, 2009
    CR3 is what is known as a floating diode.
  5. wayneh


    Sep 9, 2010
    Speaking of diodes, you should have reverse current diodes around your regulators to protect them.
  6. Six_Shooter


    Nov 10, 2012
    I just built a power supply for a school project, and it uses a very similar design, as far as the "positove supply" shows, I also used a transformer that has a center tap, what I was wondering was using the center tap to provide basically two power supplies, both 9V, but when used together, one would be "negative" in reference to the center tap, and the other positive, could that not be used, along with a pair of bridge rectifiers, to provide the desired goal of two power supplies?

    In mine it's just a 0 to 15V single power supply, but would be interested in possibly building another, if there would be a benefit.
  7. Doktor Jones

    Active Member

    Oct 5, 2011
    Assuming he already has the transformer, if he used the center tap as ground he'd end up with two ~4-6 volt outputs (positive and negative) -- the diagram shows the full output voltage as 12.6VAC, so if he were to use the center tap he'd only get 6.3VAC on either side.

    One consideration that comes to mind is to make sure the 2200uF caps are rated at least 25V (35V or 50V would be ideal); the peak voltage of rectified 12.6VAC is around 17.8V if my math is right, so lower-rated capacitors might not be so happy in there. Also, I like to leave overhead if possible to account for line surges/etc. :)

    You may also want to consider fuses/breakers... not sure whether it would be better to fuse the outputs or the input (on the transformer secondary). Might just be best to do both ^_^
  8. SgtWookie


    Jul 17, 2007
    Using the rectifier as shown will give you twice the voltage but will also double the ripple on the filter caps. You will likely find the 2200uF caps inadequate when powering significant loads at anywhere near maximum voltage output.