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  1. #1
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    Transformer structure winding structure

    Hi all,

    I'm trying to understand transformer winding structure as below:

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    Based on the transformer structure above, I noticed that there have 3 winding

    1. Primary winding : N1, N5, N9
    2. Secondary winding : N2
    3. Auxiliary winding : N3, N7

    However, when I referring to the image of winding internal construction together with bobbin, I start to confuse. Based on Figure 1.0,

    1. Primary winding : N1, N2, N3
    2. Secondary winding : N4, N5, N6
    3. Auxiliary winding : N7, N8

    Why the winding structure is difference between Figure 1.0 & Figure 2.0? Based on my understanding, the most internal winding should be primary & follow by secondary winding as other transformer image (example shown by power integration)

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  2. #2
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    Re: Transformer structure winding structure

    You are mixing unrelated diagrams of different transformers, with different number of windings. As far you are referring to Power Integrations application notes, there's most likely a detailed explanation of each transformer design.

    Your text descriptions fit neither figure 1 nor figure 2, also both figures are apparently unrelated. Clearly, figure 1 implements a different winding arrangement than the simple Power Int transformer, there are shieldings and possibly splitted windings. You should really refer to the original document explaining the design.



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    Re: Transformer structure winding structure

    Basically, I understand the transformer drawing structure from Power Integration application notes. This is what I expect for other transformer structure as well.

    Just for your information, this transformer drawing (Figure 1.0 & Figure 2.0) is from other transformer maker & not from Power Integration.

    Based on your statement, do you mean that Figure 1.0 & Figure 2.0 are not related/wrong?



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    Re: Transformer structure winding structure

    Figure 1 and 2 are implementing additional features not involved in the PI design, as already mentioned in my post. I see that you didn't yet come across splitted windings and shields, but they serve a purpose.

    Splitted windings with interleaved primary and secondary are a popular means to reduce leakage inductance.


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    Re: Transformer structure winding structure

    Hi FvM,

    Thank you very much. The word "interleaved" really help me. How about below image? Why in the primary section, P1 & P2 are stacked & in secondary, S1 & S2 are separated? What is the actual number of turns for secondary? In my calculation, the number of secondary turns should be 7. But from the image, they are parallel of 7 turns (S1 & S2)

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    Last edited by deepsetan; 15th January 2020 at 10:26.



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    Re: Transformer structure winding structure

    If S1 and S2 are parallel connected, the effective number of secondary turns is 7. You need to review the circuit schematic to verify that the secondary windings are actually parallel connected.


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    Re: Transformer structure winding structure

    Hi FvM,

    Noted.

    How about the primary connection? Why they using center tap at the transformer input? Normally I see the center tap at secondary output (example for +/- output application)



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    Re: Transformer structure winding structure

    Center tap indicates a specific inverter circuit, probably two transistor push-pull.



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