# Formula for SMPS transformer calculation

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#### UroBoros

smps transformer

Hi

For designing power transformers using CRGO and low cost core, normally we use some simple formula which relates transformer cross sectional area, core permeability and some turns/volt etc. Such simple calculations are practically sufficient for our purpose.

Just like that is there any easy method for claculating SMPS ferite transformer design data? Transformer is to be used with Top Switch Ics or UC3842 chip.

picstudent

#### hardings

##### Member level 3
smps transformer design

Good question!
I think Picstudent is talking about flyback transformer.

Hope someone here can explain the most reasonalbe design for flyback transformer.

The question can be more exact if we take 5V/1A output design as an example.

Here is some starting point as I know:
1. The transformer can not saturate in any condition;
2. Setup the boundary between DCM and CCM.

Points: 2

Mithun_K_Das

Points: 2

### Mithun_K_Das

Points: 2

#### UroBoros

smps transformer calculation

Hi
Thanks for the application note. it has a lot of info on it. let me read it.

Flyback transformer design with minimum mathematics and minimum parameters are in my mind. ( Accuracy may be slightly compramised.)

normal ferrite material is considered.

frequency can be standard or included in the variables if possible.

We need to know power required and cross sectional area of core. Then we can reach turns/volt by calculation.

Then we can trim later after by trial run.

I am not experienced in this, but from different small SMPS circuits I reached the conclusion that almost all below 60W gerally use the same line up. So if we can reach a general formula we can use it to change transformers for different volts and currents within this low power area.

So for small power we can use EE16 and some 30W range we can use EE25 or higher.The rest of circuit almost same.

Is this a workable idea or is there other factors which i overlook and makes this idea non practical?

Thanks
Picstudent

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