Ferrite core transformer Design

Discussion in 'General Electronics Chat' started by kanaknpk, Sep 4, 2009.

  1. kanaknpk

    Thread Starter New Member

    Sep 4, 2009

    Plz provide the design for the transformer

    Input:220Volts,Input Frequency:50Hz,Switching Freq:20Khz
    Using Push pull ,Full bridge switching
    According to my calculation i have selected ETD49 core
  2. bertus


    Apr 5, 2008
  3. kkazem

    Active Member

    Jul 23, 2009
    Hi kanaknpk,

    I'm not trying to insult you, but do you know what you're doing? It sounds like you're trying to design an off-line, 220VAC, 50Hz input switching power supply.
    But when you use terms like a push-pull full bridge, I've got yo question whether you even should be doing this. First of all, push-pull and full bridge are two entirely different design topologies and require different power transformer primary designs.
    I'm most concerned that you could hurt or kill yourself by possibly not understanding just how dangerous an off-line switcher primary section really is, especially if it's got a 220 or 240 VAC input. The input gets full-wave rectified and filtered with very large capacitors up to about 350 to 380 VDC (yes, I said DC). And if you wind up touching both sides of that DC, it will clamp your muscles down such that you cannot let go. The current will also likely stop your heart and within a couple of minutes or less, you'll be dead! This type of circuitry is nothing to fool around with unless your an expert. Other dangers are that the switching transistors can explode if they fail, spewing shrapnel all over you including your eyes, blinding you and burning you. You need to use a plexiglass shield or similar to prevent that sort of thing.

    If you don't know how to design a high-frequency transformer and don't know the difference between push-pull and full bridge, I would have someone else do it. FIrst of all, we need to know which circuit you're really using, push-pull or full bridge. Probably the latter as push pull has many drawbacks for high-voltage high frequency power supplies.

    Feel free to ask me more questions but please be very careful with this deadly stuff.

    Good luck,
    Kamran Kazem
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    push-pull generally means applying drive both directions (bipolar as opposed to a basic single-ended drive with one transistor switch).

    A Full or H-Bridge is a perfectly reasonable way of providing a bipolar drive.

    The simpler alternative is a centre-tapped primary and two transistors, but the H-Bridge method has a big advantage of keeping the peak voltages down, as nothing exceeds the positive supply level. (The peak on a center-tap system is double the supply).

    sorry I can't help with the specifics of the design, I have dabbled with these in the past but it is dangerous and expensive components go bang very easily...
    I now only build secondary (low voltage side) switchers.