[kenreau]

I am interested in "quiet" linear regulated ps for my home network appliances.  Currently looking to just start with the Acopian prefab modules.

My question is, how much is too much amperage, or, too little?

The Acopian models I'm looking at have specs of 12vDC at 0.7 amps and 1.2 amps.  Given the one model is under the 0.75 Amp needed by the Modem, my initial thought was just get two of the 1.2 amp Acopians.   Is 1.2 Amps (supply) - 0.75 Amps (Modem needs) = +0.5 Amp over the needed rating too much???  My notion is the 1.2 Amp should not cause any issues with the 1.0 Amp Switch.


Cable Modem   12 VDC   0.75 Amps
Cisco Switch   12 VDC   1.0 Amps

Thanks
Kenreau

[Folsom]

Going higher is better. Your device will only use what it needs. Going low can mean inefficiency and more noise from too small of transformer. If we were talking voltage, then too much could cause harm. The only harm a 10A power supply would cause is you'd be paying for more electricity to be burned off in regulation; your devices would be fine.

Also a filter on the input is wise. It doesn't just benefit the device, but reduces noise to go to other devices

[kenreau]

Thanks very much for the quick reply and info. Exactly what I was looking for. 

Fwiw, I was very suprised to read the Acopians spec out only 1 mV RMS ripple.  The Jameco (Linear regulated) I compared it to was 50 mV.  Their switching ps was 150~200 mV.

Thanks
Kenreau

[Folsom]

Linear can easily regulate much lower ripple with how it's typically done. Output is say 18v, but could vary 15-20 with ripple and line changes (or abouts). You just bleed off till you get the 12v you want.

SMPS don't necessarily regulate, but generate. They're supposed to put out a given amount but when sag occurs they may not be robust enough to compensate or the output will shift to high briefly so it'll have to discharge some from reservoir caps to come back down. There's more to it than I can explain, most likely.

The SMPS is much more efficient, however. But Linear supplies sized closer to need will burn off less power. Inefficient 10A or 2A supply, you get the idea.

There are some high end SMPS units. $$$

[G Georgopoulos]

smps can be filtered much like unregulated ps's or you can use another technigue follow the smps with a linear regulated one (7812) etc...