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.
Check out Intersil's new buck regulators. They'll go up to 42V and up to 10A, IIRC.
Regulatory problems, too.
Yes, I'd could roll my own buck with some automotive chip. Sorry, forgot to mention one minor detail: Must be isolated, or should be (we may be able to live without if it really has to be).
Thing is, with one of those ubiquitous 24VAC -> 12VDC switchers plus another buck we'd be at 60% overall efficiency or less and we can't quite afford that.
-- 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
: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.
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
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@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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.
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.
That's what Ross suggested and it's a solution I had planned for, but only in case there really is no other option.
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.
It used to be very popular in Europe but I haven't seen any industrial switch gear there in some 15 years. All the power contactors for huge motors and such were run on 24VAC. Up to 30-50A. Larger ones still had
24VAC "control contactors" but they'd drive huge 230VAC contactors, the kind that sounds like a gunshot when they engage.While studying for my masters I assembled gear like that because those jobs paid quite well, compared to bussing tables :-)
I still have a discarded supply transformer for a cabinet that was sold to me at scrap metal price. 24V, one kilowatt (!). That was from an older cabinet two stories high where you needed a ladder to get to some of the contactors. The secondary of that transformer consists of soaked-cloth insulated copper bar that was formed around the primary using a wooden mallet.
Looks like I hafta :-(
That's why I posted, was hoping for a silver bullet that lets me avoid it.
Yes, sorry, should be isolated but we could make it work without. AC/DC converters are generally isolated though because they use bridge rectifiers.
Yes, and we'd put one on there anyhow because it affords some surge protection.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Value wrong! If you only need 5 watts, the 33V filter cap ought to be about 200 uF, not 5000 uF. Or does '5000h' mean something other than the capacitance value?
We responded simultaneously. I had my secretary proof read for grammar and spelling.This explains the minor discrepancy in time stamp She's a bit slow but I keep her around because she's a good lay.:)
Yea good 105c caps are pricey particularliy for 250VDC or better. I just paid 7 bucks for two of these for a off line SMPS.
It's hard being a mad scientist on a budget.;>)
I assumed 5k hours (@105C), not 5000 henries. ;-)
Now, now ... :-)
That must be a SMPS in disguise :-)
500mOhm Rdson can get a bit toasty. But I only need a 63V cap.-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
I always thought it was meggeehoitzes :-)
-- SCNR, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Still trying to mount Lasers on sharks? ;-)
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
Even mutant sea bass run $25/lb.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Fortunately, their tiny legs don't let them carry much...
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
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