[ARC5] DC-DC Buck/Boost Converter Regulation

[Richard Hankins]

Dave

well, I can't vouch for the particular Ebay items you cite, but in 
principle a buck-boost converter (and only the first one is one of 
these) will keep the output at a fixed voltage with an input voltage 
both above /and below /that of the output.    You have the specs on the 
Ebay listings - and I see no reason to doubt them.

Note that the second one is boost only.    So it will give you 5 to 35V 
output with an input of 3V.   But put in 12V, and the output range will 
be limited to something like 13V to 35V.  In other words the output has 
to be higher than the input voltage.

As to whether a switch mode psu can regulate as well as an LM317 that 
depends what you are looking for.    The transient response of an LM317 
is pretty good.   Whether a SMPSU can do as well will depend on just how 
well its been designed.   You need to say precisely what aspect of 
regulation you are looking for.

And of course, you always have the old noise and ripple problems with 
the switchers that never really go away.   You can reduce it to 
tolerable levels - with enough filtering and screening of course.


Richard
G7RVI

On 31/10/2013 16:05, David Stinson wrote:
> I've been told that DC-DC Buck or Boost converters like these:
> http://www.ebay.com/itm/261316095061
> http://www.ebay.com/itm/261318532314
> will regulate their outputs through wide input excersions
> at least as well as something like an LM-317
> (assuming one stays within the devices design limitations).
>
> Can anyone here vouch for that?
> 73 D.S.
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