I have a 6V to 20V input I want to convert to 12V at 1 amp maximum continuous current. The output must be the same polarity as the input, so that pretty much means a SEPIC is the only way to go... However, I've been looking around and all solutions I've seen thus far require many components and a lot of surface area; I'm looking to minimise surface area as far as possible, and to do this I don't mind sacrificing a bit of efficiency. Does anyone have any suggestions?
Asked
Active
Viewed 580 times
3
-
Have you look at buck-boost ICs? – Kellenjb Nov 01 '10 at 00:38
-
can you put numbers to things like "minimize surface area"? what kind of range would you consider acceptable? – Kortuk Nov 01 '10 at 00:39
-
A buck boost would invert polarity. – Thomas O Nov 01 '10 at 09:36
-
I'm looking for <250mm^2 area. – Thomas O Nov 01 '10 at 09:37
-
A buck stage (reducing the input to 4V) followed by a boost stage (4V to 12V) would not invert polarity. Efficiency wouldn't be great (cascaded converters) but it would do the job. – Adam Lawrence Nov 01 '10 at 16:28
-
Yeah, but then I have to have a buck converter rated to deliver 3 amps (+inefficiencies) instead of a SEPIC at 1 amp. A 3 amp buck converter could be quite big, possibly bigger than the SEPIC itself. – Thomas O Nov 01 '10 at 17:02
2 Answers
3
I've built a SEPIC and published this page about it, there's even a description of how to build a the inductor without unobtainium: http://dren.dk/carpower.html
... but the inductor design is pretty hackish, so it's not going to win any medals for production use.
dren.dk
- 3,512
- 18
- 17
2
Page 31 of this datasheet for the Linear Technology LT3757 has an application circuit using a SEPIC converter for a 5.5v to 36v input and 12v 2A output. The biggest part appears to be the dual inductor, which is 12.5 mm square. Since you only need a 1A output, you might get by with a smaller inductor in the DRQ74 series, which is 7.6 mm square, however it is currently a non-stock item at Digi-Key.
tcrosley
- 47,708
- 5
- 97
- 161
-
-
@sherrellbc Links fixed. I answered this 3 1/2 years ago, have no idea how long they've been broken. – tcrosley Jun 14 '14 at 04:19
-