UCC28911: Transformer number of turns and size of wire

Hi Danilo,

Thank you for the query.

It seems from the attachment the customer is using UCC28C45 as shown below and the specifications also seem a lot different from the previous e2e thread:

In this case can you please reconfirm with the customer and post with the correct part number so that it is assigned to the correct product expert.

Regards.

Harish

Hi Danilo,

From the specifications attached we can arrive at initial estimates as follows:

N = (L x Imax)/(B x Ae)

Using Ae =12.2 mm2 for EE13/7/4, B=0.2T, Imax is the max current in the primary around 15mA, Fsw (assumed) as 105khz

N = 36turns (primary)

Secondary = 36 x 0.078 = 3turns

Aux = 36 x 0.422 = 15 turns

In order to calculate the wire areas, I would recommend the following approach:

Aw1 = (a1 x Ku x Wa)/ (n1)

where Aw1 is the wire area

a1 is the fraction of window area area allocated to each winding

Wa is the window area

Ku is the winding fill factor

n1 is the nimber of turns

You have have to do this for each winding to estimate nearest wire size.

I would ecommend that you see the following magnetics design guide by Llyod dixon to start with.

https://www.ti.com/lit/ml/slup127/slup127.pdf

Also it would be better to get custom samples designed by magnetic experts from Wurth electronik and Coilcraft.

Thank you

Regards,

Harish