Saturation of ferrite core in SMPS?

[eem2am]

Hi,

I am designing an offline, isolated flyback at 22W with Vout = 36V, Vin=85-265VAC.

I will be using a EFD25/13/9 ferrite core transformer from Epcos(the AL = 315 one, N87)

Ferrit core datasheet:-

**broken link removed**

On page 2 of the datasheet, it says Pv W/Set is 200mT....
https://i54.tinypic.com/34owms7.jpg

....but i thought the saturation flux density of most ferrites was 300mT?

My peak flux density is 220mT.

-do you think this will saturate this core?

 

[pico]

In general engineering thinking. Every design must have a good safety factor, stability and reliability.

 

[FvM]

What does the quantity Pv indicate? Just read the text exactly. The datasheet gives one characteristic point from the core losses versus AC flux and frequency characteristic. To see the complete characteristic, you have to refer to the N87 material data. N87 saturation flux at 100 °C is above 350 mT.

If you consider the simple fact, that efficiency is usually an objective when designing SMPS, you'll understand why the characteristic doesn't show losses above 200 mT.

P.S.: In your example, raising the flux from 200 to 220 mT would approximately result in core losses of 2.3 instead of 1.8 W for the transformer (assuming you're operating it at 100 kHz). That means more than 10 % losses for the transformer core only.