DC-DC converters: very dirty RF?

January 15, 2010

Hey everyone,

Since the Asus Eee PC I tested showed a lot of high fields, and the screen is

rather small to use with an external keyboard and mouse, I'm now looking at a

shielded LCD monitor from Low EMF Office in Italy; unlike " Safe Level " , the guy

really seems to go the whole way in making the monitor as low emission as

possible.

Along with that I'm once again considering using a Mini ITX system from Logic

Supply (a small, fanless computer with a solid state hard drive).

Many of their computers can be run from a DC source, which appeals to me, since

I'll eventually be off grid and DC powered everything, anyway.

The thing is, to power them with DC, they use built in DC-DC converters, often

under the name of " PicoPSU " . Some are strictly 12V converters, while others can

accept a wide range of input voltage, some between 9 and 30 volts, and would up

or down-regulate it accordingly. I am certain these are switching converters.

My question is, can anyone here say if these would be worse for RF emissions

(both emitted and conducted) than, say, your average AC-DC converter used in a

desktop PC and monitor?

My assumption is not - only because they're only regulating the voltage, as

opposed to regulating the voltage *and* changing high voltage AC to low voltage

DC, in the case of a normal AC-DC adapter - but this is my assumption. I don't

really know for sure.

Since these fanless cases are aluminum, I'm not as worried about the RF coming

through the air - I could always put the case in a shielded space. But I would

wonder about the RF getting conducted to the keyboard and mouse. I'd certainly

use ferrites, but if anyone has thoughts about this particular sort of DC-DC

converter, I'd appreciate hearing them!

Thank you!

R.

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