Questions about datasheet of transformer(Wurth Elektronik)

[gwdbsuccess]

Hi,
It’s the first time that I design a flyback converter.
I want to ask a stupid question.


Is the value of 15V@20mA/15V@3A Absolute Maximum Rating???
If it is "Absolute Maximum Rating",then the transformer can't operate normally when Vin>90v
EX:
Vin(1-4)=400V
(1-4)5-6)=6:1
Vaux(5-6)=66.67V > 15V
So, I am very confused about the meaning of the value(15V@20mA/15V@3A)

plz help me with this problem.m(_ _)m

View attachment 750311771.pdf

 

[schmitt trigger]

You need to understand how a flyback converter operates. It is a boost-derived converter.

You are not considering the effect of the duty cycle.

 

[treez]

GWDBSUCCESS i have posted an LTsice simulation of an offline flyback that uses your transformer. Just convert from.txt to .asc, then open in ltspice, then hit running man icon.
Also posted is excel design doc.
The datasheet you attached does not give the ferrite type so you cannot calcuate the core loss...so you will have to do thermal measurement of core with thermocouple.
You can click it etc to find dissipations. But not switching loss etc.
You can also click to see rms currents etc

Also attached is a sim which shows the dc bus variation in voltage

- - - Updated - - -

It does not say if the windings are of TIW or ECW, so its not possible to be exact about exactly how much winding loss you could have.

Are you asking if you could have more than 15v and 3a output?

To find the winding loss just do i^2.R........i have shown how to calculate the rms winding current in the excel. But remember skin effect.
The isol is only to 2500vac and that sounds a bit low for universal mains...its usually 3000vac.

 

[gwdbsuccess]

treez
Thank you for your explanation and calculation!!

Are you asking if you could have more than 15v and 3a output?

Yes!!
If Vo=20V,Io=1A.
Can it work??

the Aux side(5-6):
If Vaux=30,Iaux=10mA.Duty=50%.
Can it work??

I just want to ask the definition of 15V@3A &15V@20mA.
Is it absolute or average??

 

[treez]

i dont think thats the way to look at it. I think they just put 15v and 3A as a recomendation example.
You look at it in terms of your winding loss, core loss, and voltages referred to primary and secondary, and the duty cycle, peak current etc.
But no, it doesnt have to be always 15v and 3a.....
maybe later i recalculate duty cycle etc for 20v and 1a...i am sure it can be done with this transformer.

 

[gwdbsuccess]

treez
thanks your explanation!

I will experiment with samples to understand it ~