[time-nuts] DC-DC converter

Hal Murray hmurray at megapathdsl.net
Sat Sep 26 09:05:08 UTC 2009

> Does anyone know where I can get an inexpensive 12VDC to 48VDC
> converter to power one of my Z3801A's? I can find 12VDC to 24VDC
> units, like this one at Jameco: http://www.jameco.com/webapp/wcs/
> stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&p
> roductId=212514

That unit is the SD-50B-24.

Unless I'm reading the data sheet wrong (and making a fool of myself), A is 
12V input, B is 24V input, and C is 48V input.

You want the SD-50A-24 which Jameco doesn't carry.  Mouser does carry them.  
Probably many others too.

I haven't seen anything in the 12V to 48V area.  I haven't been looking 
recently.  Several years ago I was keeping an eye on the DC-DC converter area 
but I was interested in 48V inputs so I could have easily skimmed over 
something appropriate for your usage.

I think you have several options:

Use two of the units above (or similar) with the outputs in series.  You only 
need 25W each.  Or maybe 4x 12V to 12V units at 12 or 15W each.

Get lucky and find a unit that goes directly 12V to 48V.  I was going to say 
that given the lack of suggestions so far, I doubt if you will find one.  But 
then Ed Palmer found some on EBay...

Another option is to go 12V DC to 120V AC and then 120V AC to 48V DC.  Both 
of those are common.  The efficiency will suffer because of the double 
conversion, but modern converters are 90+% efficient and both units will be 
from highly competitive markets so you should have a lot of choices.  You can 
(obviously) avoid the first stage when running off wall power.

You could also build your own.  I haven't looked, but I'll bet you can find 
an app note from one of the usual chip vendors telling you how to do it.  You 
don't need isolation or fancy regulation on the output.  That should simplify 
things a lot.

These are my opinions, not necessarily my employer's.  I hate spam.

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