Many off-line SMPS ICs are designed to handle this range without switching.

It just becomes a case of selecting the IC from your favourite IC manufactu=
rer for the purpose. If you are looking at using an old chip then it may be=
 time to rethink the design and go to a new chip. ST seems to be one of the=
 suppliers of choice in this area.

See http://www.st.com/web/en/catalog/apps/SE423 and for the 'input voltage'=
 select 'wide range 50hz' after selecting SMPS AC/DC in the LH buttons.



> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
> Of Ryan O'Connor
> Sent: 26 March 2015 10:16
> To: Microcontroller discussion list - Public.
> Subject: [EE] universal main voltage PSU design
>=20
> I've been designing a smps, and I wonder, is there an elegant way to desi=
gn
> the input stage of the psu to be able to run from ~85-240VAC? I don't fan=
cy
> using active PFC, and would like to keep it simple.
> Preference is for the voltage to automatically be detected so they don't =
have
> to switch a switch based on where they live.
>=20
> Cheers
> Ryan
> --
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