Are there any 24VAC to 3.3VDC/1.5A SMPS?
in [Design]
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From: Hammy on 5 Jun 2010 06:45 On Fri, 04 Jun 2010 17:56:04 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Gents, > >Does anyone know of a little AC/DC switch mode converter module that can >take 24VAC and put out well regulated 3.3V at 1.5A or more? $25 in 1k >qty would be nice, availability in the US would be even nicer. > >All I see is 24VAC to 12VDC and placing two in a row costs effiency. >Sure, I could roll my own again but this time we want to avoid NRE and >agency hassle (EMC et cetera). You could just add a bridge rectifier and a filter cap. This would widen your selection to several hundred of the SMPS's that have a max input to 36 or 75 Vin. Cheapest one I could find with a quick search is http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=445-3306-ND
From: Spehro Pefhany on 5 Jun 2010 09:41 On Fri, 04 Jun 2010 17:56:04 -0700, the renowned Joerg <invalid(a)invalid.invalid> wrote: >Gents, > >Does anyone know of a little AC/DC switch mode converter module that can >take 24VAC and put out well regulated 3.3V at 1.5A or more? $25 in 1k >qty would be nice, availability in the US would be even nicer. > >All I see is 24VAC to 12VDC and placing two in a row costs effiency. >Sure, I could roll my own again but this time we want to avoid NRE and >agency hassle (EMC et cetera). 24VAC is not a very common voltage (24VDC is much more popular in industrial applications). I second the suggestion of adding a bridge and filter cap upstream of a converter, along with maybe a CM choke and some film or ceramic caps. You didn't specify whether you needed isolated or not, that's going to make a difference. When you read the detailed app notes, most of the modules require some filtering ahead of them to meet EMC requrements anyway (small caps and CM choke maybe), so it's not really "extra" work. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Joerg on 5 Jun 2010 11:17 Michael Kellett wrote: > "Joerg" <invalid(a)invalid.invalid> wrote in message > news:86tllfFibtU1(a)mid.individual.net... >> Gents, >> >> Does anyone know of a little AC/DC switch mode converter module that can >> take 24VAC and put out well regulated 3.3V at 1.5A or more? $25 in 1k qty >> would be nice, availability in the US would be even nicer. >> >> All I see is 24VAC to 12VDC and placing two in a row costs effiency. Sure, >> I could roll my own again but this time we want to avoid NRE and agency >> hassle (EMC et cetera). >> >> -- >> Regards, Joerg >> >> http://www.analogconsultants.com/ >> >> "gmail" domain blocked because of excessive spam. >> Use another domain or send PM. > > Why not use a transformer to take the 24V AC up to 110V and then use any bog > standard switcher to get your 3.3V ? > Michael Kellett > Not enough space :-( Plus on this one it could get us into regulatory hot water. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 5 Jun 2010 11:20 Ross Herbert wrote: > On Fri, 04 Jun 2010 17:56:04 -0700, Joerg <invalid(a)invalid.invalid> wrote: > > :Gents, > : > :Does anyone know of a little AC/DC switch mode converter module that can > :take 24VAC and put out well regulated 3.3V at 1.5A or more? $25 in 1k > :qty would be nice, availability in the US would be even nicer. > : > :All I see is 24VAC to 12VDC and placing two in a row costs effiency. > :Sure, I could roll my own again but this time we want to avoid NRE and > :agency hassle (EMC et cetera). > > > I don't think there are any 24Vac input converters off the shelf - almost zero > demand I would think. > > Why not use one of the 6 - 10W, 18-36V input DC-DC converters (eg. V-Infinity)? > Provide a bridge rectifier and bulk filter cap in front of it. A few bucks for > the BR and cap would keep it under $20 per unit in 1K quantity. That's solution B, if I really, really have to. In this case that would require some regulatory scrutiny though because the input side would now not be "taken care of by module" anymore. If that wasn't an issue I'd just roll my own because then I won't have to deal with those dreaded 50C or 60C derating issues that "professional" switchers often exhibit. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 5 Jun 2010 11:24 Hammy wrote: > On Fri, 04 Jun 2010 17:56:04 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Gents, >> >> Does anyone know of a little AC/DC switch mode converter module that can >> take 24VAC and put out well regulated 3.3V at 1.5A or more? $25 in 1k >> qty would be nice, availability in the US would be even nicer. >> >> All I see is 24VAC to 12VDC and placing two in a row costs effiency. >> Sure, I could roll my own again but this time we want to avoid NRE and >> agency hassle (EMC et cetera). > > You could just add a bridge rectifier and a filter cap. This would > widen your selection to several hundred of the SMPS's that have a max > input to 36 or 75 Vin. ... That's what Ross suggested and it's a solution I had planned for, but only in case there really is no other option. > ... Cheapest one I could find with a quick search is > > http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=445-3306-ND We could probably get one from CUI for under $15, offsets the cost for a good 105C/5000h or similar electrolytic up front. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
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