How to find smps transformer parameters

Thread Starter


Joined Dec 19, 2015
Hello all,

I am designing a flyback smps with 5 Volt , 1 amp dual output. For that design i use software PI expert of smps design software. As i contact to manufacture of transformer. They want the following parameters.

1) Type of core and core size
2) winding details
3) number of tons
4) Start and End in location of the each winding on the bobbin
5) Induction of the main winding

And i have no idea about this parameters.But from that software i can find this parameters.Please let me know if there is another way to find this parameters (software or online calculator).

I am attaching my design here.

I want to verify this specification. Please share yours ides from all experts presents here. :)


Thread Starter


Joined Dec 19, 2015
Thanks to all for reply.

But i am still confuse how to verify transformer specification that provide exact rating. I have contacted with manufacturer they all tell me that it working on trial and error method means after they manufactured we have to change some other components and check the output current and voltage.


Joined Aug 21, 2008
I know this is not exactly the answer for which you were looking, but it appears you don't want to learn how to design transformers. There are many trade-offs in the design of a transformer. What might be your best shortcul is to find a design of an offline flyback transformer for a similar power supply. If you look around on the Power Integrations website you should find several examples of transformer design and almost certainly one for a 5V 1A output. Just pay attention to the frequencies.

The transformer in your schematic has a part number. Why not find out the specifications of that transformer.