DPRG mailing list archives: [DPRG] switching power supply

Mon Mar 26 14:16:41 CDT 2007

>From: Ed Paradis <legomaniac at gmail.com>
>And I forgot to mention that 1 amp output gives you more than you'll
>ever need unless you're trying to run some sort of wireless LAN router
>or other embedded computer.

I've only used single board computers from Soekris and Technologic. So
my experience is limited. But conservatively,

x86 based single board computers require around 1 amp at 5 volts
ARM9 based single board computers require 200 mA to 400 mA at 5 volts

So if you can get around 1 amp from a 5 volt power supply, then as Ed
says, the embedded 32 bit computer becomes viable. However, even at
one amp, extra devices like cameras and radios can increase power
requirements dramatically. For instance, I think that even a generic
webcam draws around 100 mA.

>Honestly, 500mA is probably more realistic.

I've always used single board computers with an on-board switching
regulator. The 5 volt rail is able to source several hundred milliamps
ok to external devices. So if you were to use a computer, than an
external switching power supply may not be necessary.

The one thing I don't know about is driving a MOSFET H-bridge. I know
that current requirements to the FET gates can be pretty high. But in
this case, my guess is that it's probably smarter to buy something
off-the-shelf anyway (which then has its own power supply so again you
don't need an external one).

>On 3/26/07, Ed Paradis <legomaniac at gmail.com> wrote:
>> From what I've commonly needed and from what I remember from the
>> powertrends device:
>>
>> Input voltage: 7 to 35 volts
>> Output voltage: 5 volts
>> Maximum current output: 1 amp
>>
>> This allows the common 6 NiMH/NiCd cell packs (barely), 12 volt
>> leadacid, dual 12 volt lead acids, and the occassional large cell
>> count NiMH packs that DPA uses.