Flyback Transformer Design (48V in, 12v out, how to layer turns, leakage inductance)

[ElecDesigner]

Hi,

I'm working on a high frequency flyback power supply. Specs approx:
1MHz sw freq
Vin 48V
Vout 12V
Power out 10-20W

My questions are regarding the transformer.

1. I have decided on a core, windings etc. I have a 2 layer primary and 2 layer secondary.
What would generally be the best way to layer this?
I was thinking 1 layer of primary first but would it be better to have.....
1. 1 layer pri, then 1 layer sec, then 1 layer pri, then the final sec. or
2. 2 secondary layers directly together sandwiched between the two single primary layers.

Is there a rule of thumb for leakage inductance of a well designed (& manufactured) flyback transformer - perhaps as a percentage of the main inductance?

 

[smijesh]

re: Flyback Transformer Design (48V in, 12v out, how to layer turns, leakage inductance)

1. 1 layer pri, then 1 layer sec, then 1 layer pri, then the final sec. or
Leakage inductance will be reduce ¼ th of regular primary secondary winding but inter winding capacitance will be double. Wave form rigging will be very less

2. 2 secondary layers directly together sandwiched between the two single primary layers.
Leakage inductance will be reduce 1/2 rd of regular primary secondary winding and less inter winding capacitance . Wave form rigging also less
Better to go ahead with second option (2.2)

(Inter winding capacitance are important if high voltage application)

 

[schmitt trigger]

re: Flyback Transformer Design (48V in, 12v out, how to layer turns, leakage inductance)

Do you have any additional requirements, like creepage distance? I don't think so, since your primary is relatively low voltage. But please check.