Universal SMPS design

Hi there,

I need some advice and guidance.

I have this design specifications for the almighty SMPS

1)Input Voltage : 24V-270V AC/DC (Universal Range)
2)Power Rating : 20W
3)Output Voltage : 20VDC
4)Output Current : 1 - 2A
5) Isolated

Add 1) I have troubles with this specification. Mainly ICs used in AC/DC converter operates from 80V-260V basicly because they are used to convert from 230VAC to xxx DC. Because of this feature I have to design the Voltage detector and the switching mechanism which will switch between high input voltage converter to low voltage converter.

Any idea how to solve this ?

Thanks for your help, Sasa


P.S. the 6th and 7th req. cheapest and smallest as possible

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