# Dual Polarity high current OF PSU computer

Discussion in 'Power Electronics' started by mostafa_gordy, Feb 21, 2013.

1. ### mostafa_gordy

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0
Mar 11, 2012
Hi....
what is way to get Dual Polarity +12V -12V high current of an PSU ATX computer ??

2. ### BobK

7,682
1,688
Jan 5, 2010
You can't. The -12V supply is low current.

Bob

3. ### mostafa_gordy

14
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Mar 11, 2012
what is way to boost currentof -12v ?

4. ### BobK

7,682
1,688
Jan 5, 2010
You could use and isolated DC-DC converter to generate -12V from the +12V or +5V.

How much current are we talking about?

Edited: Actually a buck-boost converter will give you a negative output without being isolated, this is even better.

Bob

Last edited: Feb 21, 2013
5. ### mostafa_gordy

14
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Mar 11, 2012
DC-DC converter ؟
buck-boost converter .....
more explanation....
simple way ??

6. ### BobK

7,682
1,688
Jan 5, 2010
The simple way is to buy a +- 12V power supply.

Bob

7. ### mostafa_gordy

14
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Mar 11, 2012
How much current are we talking about? I need more than 2 amper -12v and +12v for power audio Amplifier

8. ### Electrobrains

259
5
Jan 2, 2012
Of course you could use two old PC power supplies and put the 12V positive outputs in series. That would give you the +/- 12V supply at high current and low (or no) cost.

14
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Mar 11, 2012

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10. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
Be careful, the ground could be tied to mains earth.

Internally however, you could manipulate the circuit to generate a high current -12V supply if you were VERY careful.

That would make one power supply +12V on the +12V rail, and the other -12V on the +12V rail.

To do this you need to understand exactly how that power supply rectifies and filters the output and what feedback there might be from this rail.

11. ### Electrobrains

259
5
Jan 2, 2012
Steve is probably right. I measured a couple of pc supplies and they all had the minus output connected to the metal case (earth).

Your pictured circuit would work if you only supply earth to the left power supply. The metal case of the right supply would then need to be isolated, because it would be connected to -12V.

I am not allowed to officially recommend such approach though, because the pc power supplies are intended to be run with a solid earth connected (EMC and security reasons).

12. ### woodchips

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Feb 8, 2013
Possible alternative is the 12V PSUs used in the server computers, couple I saw were 40A at 12V, not bad.

Bob