How wrap transformer...

[MaXiZ]

Hi to all..
I'm build some SMPS Push-pull topology. BUt i've the following doubt...
How I should wrap the tranformer?
Case 1)
---------------
SECONDARY2
SECONDARY1
---------------
PRIMARY2
PRIMARY1
---------------
CORE

Case 2)
-----------------
SECONDARY2
-----------------
PRIMARY2
-----------------
SECONDARY1
-----------------
PRIMARY1
-----------------
CORE

What's the correct one?

 

[Sch3mat1c]

#2. More coupling means better HF performance.

Tim

 

[MaXiZ]

More coupling

Wht mean exactly?
I'm not an engeneer... A beginner.. Sorry!

 

[MOER]

xfr

Interleave the primaries and secondaries as many times as possible. Reduces leakage inductance. WE typically split our high frequency switching supply transformers into 3 primary and 3 secondary windings.

So lay primary 1, then sec 1, pri 2, sec 2, pri 3 and last sec 3

Steve

 

[MaXiZ]

three primary on a push pull????

 

[richie00boy]

Interleaving is only good for transformers driven by H bridge. If the topology is of the centre tapped primary type, there will be small mismatches between the two primary windings causing gradual shift towards saturation. If the centre tapped primary type is to be used you should wind bifilar, i.e. two runs of wire wound at same time.

 

[MaXiZ]

Another small question...
Is better to insulate each wrap with insulating ribbon or allow "contact" between each warp?
Thanx in advance...