48V power supply

Why are you shouting?

It is all about finding a suitable transformer. Are you buying that? Where?

ahhhh,
I know MikeMI.
The cost of power supply is important for me.
50 wat transformer is expencive.
I think the very easy flyback is better. the feedback is not important because the ripple is not important for me.
but a short current protection is need.
I think a flyback with self oscillation is very cheap.
So
Is there any schematic for help me?

Here is a 56 VA 36 volt dual primary transformer for $15.71.

Triad Magnetics - FD7-36 - Transformers - Power Products - Allied Electronics

When rectified it will give you around 60 volts open circuit but being a split wound transformer the primary and secondary windings are side by side which means that the secondary can be easily opened up and a few turns removed to drop the voltage down if necessary.

You wont get close to that price building your own SMPS.

what about switching?
a flyback or halfbridge with self oscillation and thyroid core is very cheap, I guess.