Flyback transformer with paralelled secondaries

[cupoftea]

Hi,
Our contractor insists on doing our interleave-wound Flyback SMPS transformer (Np/Ns = 12/16) as follows...

S1: 16 turn sec
P1: 12 turn pri
S2: 16 turn sec (S2 in pllel with S1)

This is a bad idea, he would be better off doing it with ...

S1: 8 turns SEC
P1: 12 turns Pri
S2: 8 turns SEC (S2 in series with S1).

This is because if a mistake is made and a 15 turn sec gets accidentally paralleled
with a 16 turn sec, then the 16 turn one will be driving current into the 15 turn piece.

Would you agree, series is always better?

Spec is...
24vin
24out
48Wout
60kHz

 

[betwixt]

Under that scenario yes but I would be concerned if a transformer could be manufactured so badly that turns were missing.
Parallel windings means each only carries half the current compared to series ones.

Brian.

 

[Easy peasy]

Indeed - the errors able to be introduced are less with the series approach,

however - if the wire sizes can be all the same - this would be a time saver in manufacturing

also - if you have a low pin count bobbin - paralleling may be useful - only 2 pins needed for pri


We have made very many transformer with paralleled pri and sec wdgs for best performance ( from 50W flybacks to 3kW H bridges ) - only about 1 in 100 have an issue

we return these for properly made ones.

 

[FvM]

This is because if a mistake is made and a 15 turn sec gets accidentally paralleled
with a 16 turn sec, then the 16 turn one will be driving current into the 15 turn piece.

Seriously? And how do you make the design fool-proof against other mistakes?

How about choosing a quality supplier?