NNTP-Posting-Date: Sat, 07 Dec 2002 11:51:14 -0600
Subject: Re: switching dc-dc: DIY or off-the-shelf
Date: Sat, 7 Dec 2002 12:57:29 -0500
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Hi, Thanks for your thoughts. That's the direction I I'm heading -- we
initially used off-the-shelf bricks, but then they got discontinued and we
had to scramble to find a replacement. And they cost more. I was worried,
however, that since they have so many more components than the "simple
switcher" approach, they must be better in some way :)
But with the NS webbench design software, it's quite easy indeed to do a
design, I just wanted to make sure there wasn't some catch.
"Mike Harrison" wrote in message
> On Fri, 6 Dec 2002 22:07:46 -0500, "Mike" wrote:
> >Hi, I'm wondering if anyone has any opinions regarding the use of
> >off-the-shelf DC-DC converter modules (around $25 for 10 watts) or doing
> >yourself (with e.g. the National Semi 2592HV) (about $10 total). Note
> >this is for 48 volt in, so it's a little more complicated. Are there any
> >drawbacks to the DIY approach, and if not, why doesn't everyone do it
> >instead of using the modules? In the little testing I've done, it seems
> >that the DIY aproach has a lot higher EMI, but I don't know if that's the
> >only problem. Any thoughts?
> Depends if it's a 1-off, a small production run or large volume.
> DIY is more design effort, but has the advantage that it can be
> tailored to your application, and usually fitted on the PCB with
> everything else.
> EMI is down to good PCB layout. It's unlikely to be hard to get EMI
> good enough for approvals - if you have particularly sensitive stuff
> near it it may be a little harder, but using an off-the-shelf unit may
> be no better in this respect.
> With off-the-shelf unit, you also run the risk that the manufacturer
> will change the design without telling you. here may also be a higher
> risk that they may discontinue it - this is less likely to happen with
> a DIY solution.
> The bottom line is to balance the extra cost of buying ready-made
> units against your time & effort designing a DIY solution.
> Switchers using the NS parts are not especially hard to get to work
> well, and personally I'd only ever consider a ready-made unit for
> 1-offs or where an isolated output is needed, which usually needs
> custom magnetics.