power supply design on board.

[tapu]

Dear all,
I made a project.In which I designed a power supply for 5v & 12v dc.But i am using transformer(step down) externally of 500ma/12v.But i want to design a circuit which does not require external transformer.please reply.

 

[crutschow]

You always need a transformer to provide isolation safety when powering from the mains.
To minimize size you can use a mains powered AC-DC switching inverter. It switches at a high frequency so the transformer can be small.
The new small wall-warts use that technique.