Can a Lin PSU be used for a device that uses Switching PSU?

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Ethan

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I'm curious I it would be OK to power things like computer peripherals, (hard drives/hubs/misc gadgets) that are normally supplied with switching PSUs with a linear PSU. The reason is I have a bunch of those external switching PSUs all over the place. It would be nice to consolidate all that into one box.

Thanks!
 
I was thinking along the same lines, but then realized, I don't know a darn thing about switching power supplies, so I don't reaaaaaaally know.

I suppose I could cheat and just put all the little switching supplies into a box and rack it, especially since the current demands are pretty hefty for some of these devices. But it would still be nice to keep the little switching supplies accessible for when I travel.

But I'm still curious. Other than being unpractical, would a linear supply work?
 
> I have a bunch of those external switching PSUs all over the place

Until you prove otherwise, you need "a bunch of" power supplies because you don't want all your gear sharing a common power ground.
 
What if the PSU was limited to only the "same" devices.

For instance I have 6 identical external Seagate drives. Couldn't they all share the same power ground? Consoles do this...

Thanks P!
 
the drives won't care what kind of PSU is feeding them due to their circuitry and their power regulation on board, so in this instance that would work just fine as long as there isn't an overwhelmingly noisy rail.

in fact the isolation involved in switchmodes is better for digital devices. remember that hash can work both ways. Digital has a nice feature called "ground bounce". that's where the ground potential changes due to the off-on nature of the current. once you couple this onto an analog ground plane you get noise radiation back into the system from GROUND! once your ground is noisy, there isn't much you can do to quiet the system down without rethinking you grounding planes and ultimately separating them through ferrite.

so it really depends on what you are trying to power. good quality switching PSUs are just as quiet as linears and can even be quieter and cleaner if they are designed right, however there is a large mass of cheapo switching PSUs with poor components, regulation and filtering that feed things like TVs and computers that don't need super clean rails and these are the ones that give switching PSUs a bad name.

If you look in digikey and see a Switchmode PSU for 100$ and wonder why the next page has the similar rated PSU for 10$ then take a close look at the fineprint specs and you might find your answer.

:thumb:
 
Just watch out for the peak current demanded by some of those devices, in particular, hard drives. They take very large current peaks (a few amps) for their voice coil motors. You don't want the supply to crap out if all drives decide to seek at the same time. If you have AC power supplies with an on-board rectifier to generate +/- supplies you can be in for a surprise as well.
 
In case this might also matter for particular applications, some cheap linear supplies have no regulator and give you little-to-no isolation from input surges, brownouts, and so forth. Buyer beware
 

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