Small Transformer Design

You need to define small...
One man's small is another mans huge.
To me 'small' is 4va, to someone else it is 5kVA
Del

Don't design one. Buy one instead.

Do an internet search for help in learning about transformers.

Here, I'll get the ball rolling with what you'll need to know first: Transformers - Wikipedia, the free encyclopedia

Try an internet search for "guide designed small transformer" as this search alone produced many results.

For me any transformer a single person can lift is small, any transformer you can accidently inhale and lose is really small, and any transformer you cannot see with the naked eye is tiny.