Maker Pro
Maker Pro

24V switching PSU?

  • Thread starter Dirk Bruere at Neopax
  • Start date
D

Dirk Bruere at Neopax

Jan 1, 1970
0
Ian said:
Because the foldover currents will certainly be unmatched.
That being so, when shorted (or overloaded) one PSU will get -12V applied
across its terminals.
This may well be bad for it.
I was assuming that it was a 24V supply, not a 12V center tapped supply.
In any case, in some cases with motors, and fast reversing, the motor can
impose a negative voltage across the supply.

Well, it would be through FETs operating as in PWM mode

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org
 
K

Ken Smith

Jan 1, 1970
0
Can one get 500W of transformer, plus large caps, for the price of 2
PC power supplies?

If I went to Halted, chances are I could get a 5KVA transformer and the
needed caps for less than the price of one supply.
 
K

Ken Smith

Jan 1, 1970
0
Keith Williams said:
As others have pointed out, "RMS watts" (no capital 'W') is
meaningless.

It has a meaning:

It means you take the instantanious power square it, average it and then
take the sqrt. The result may not be useful but it isn't as meaningless
as measuring noise voltage in inches or something.
 
K

Ken Smith

Jan 1, 1970
0
Rich said:
But, can you put a 1N5406 in series with a 120V, 100W light bulb across
the 240V mains, and get 100W worth of light?

Yes, but not for as long as the bolb would last on 120V AC.
 
E

ehsjr

Jan 1, 1970
0
Keith said:
Not true anymore. The processors are powered off the +12V supply
output (the ATX-12V and EPS-12V specs). That's were the real power
is (500W is a little high though).

Here is one with 440W (20A) on the +12V output:

http://www.newegg.com/Product/Product.asp?Item=N82E16817163028

That's impressive. I wonder how ugly it would be if you
put the 3.3 and the +12 in series through two high current
diodes and tried to run a ham rig. Any thoughts?
(No, Virginia, while there may be a Santa Claus there is
no way I'll connect that setup to my IC746!)
Ed
 
ehsjr said:
Keith said:
The processors are powered off the +12V supply output (the ATX-12V and
EPS-12V specs). That's were the real power is (500W is a little high
though). [...]

That's impressive. I wonder how ugly it would be if you put the 3.3 and
the +12 in series through two high current diodes and tried to run a ham
rig. Any thoughts?

Pretty ugly. As far as I know, the outputs aren't floating with respect
to one another - the +12 V and +3.3 V share a common ground. You might
be able to do it with two power supplies, depending on if the secondary
common is also common to the powerline or not. Alternatively, some
people have opened up a PC supply and twiddled the regulation to boost
the +12 V by a volt or two to run stuff that wants to be in a car.

If you had some time on your hands, you could build a circuit with some
MOSFETs and some huge capacitors. Charge one capacitor off of the +3.3
V, then put it in series with the +12 V. Have another capacitor doing
the same thing, 180 degrees out of phase. Or three capacitors at 120
degrees, to give each cap more time to charge.

Down to maybe 10 m, you might be OK, but below that, the switching noise
from the supply may start to bother you. I know that there are switching
supplies designed for ham radios that are alleged to have more filtering
than a garden-variety switcher.

Matt Roberds
 
K

keith

Jan 1, 1970
0
It has a meaning:

It means you take the instantanious power square it, average it and then
take the sqrt.

I didn't say it couldn't be done, only that it ws meaningless.
The result may not be useful but it isn't as meaningless
as measuring noise voltage in inches or something.

As far as I'm concerned, it is exactly as meaningless.
 
Top