help needed in switch mode power supply design and anaylsis

I'm trying to design a 5 volt dc , 5 amp output switch mode power supply from a 240 volts ac mains supply for my digtal clock. i am completely in the dark and any assistance in terms of circuit schematics and general information will be greatly appreciated. This power supply must be well regulated and stable for the corret operation of this digital clock.

Please feel free to e-mail me mikechamboko@engineer.com

from a lost and troubled engineering fanatic

mike