[SOLVED] Dual voltage in pc psu

[thebadtall]

Hello, is it true that a common power supply of a PC has +/-12v supply instead of 12v and gnd ?
Because if so it can used as 24v for other purposes (right) ?


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also if it is true that a pc psu has +/-12v ,
is it possible to connect 2 power supplies in order to have +/-24v ?

Thank you

 

[Genovator]

Yes. I heard the same. PC SMPS have split supplies. 3.3v and 5v are used for ic's and controllers. 12v is used for motors, fans, etc.
Connecting 2 +/-12v lines in series are same as connecting two batteries in series. It should work, but I can't guarantee in switching supplies. Even, there are no two different split sources of12v available in SMPS.

 

[rfredel]

Hello thebadtall,

Normally pc pdu have +12V - Gnd - (-12V), but the negative voltage can not deliver the same current than the positive one. The negative voltage can deliver 0,5A to max. 1A, but the positive one between 5A to 20A.

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is it possible to connect 2 power supplies in order to have +/-24v ?

You can do it, but only with the max. current of the negative voltage.

Regards

Rainer

 

[tpetar]

No, you cannot use that because -12V rail is weak, just like rfredel says, its up to around 1A for negative, and positive goes 40A-50A and up for higher power PSU. 12V is divided in separated rails each around 18-20A.

One example:
Sparkle SCC-850AF Gold Series Modular Power Supply

+12V 1: 16 A
+12V 2: 16 A
+12V 3: 16 A
+12V 4: 18 A
+12V 5: 18 A
+12V Rails: 5
+3.3V: 24 A
+5V: 30 A
+5VSB: 3 A
-12V: 0.5 A
240VAC
4-Pin Floppy Connector: 3
4-Pin Peripheral Connector: 9
8-Pin PCI-Express Connector: 4
Energy Efficiency: 80 PLUS Gold
Fan: 139 mm
Form Factor: ATX
Input Voltage: 100
Modular Cabling: Yes
Motherboard Connector: 24-Pin
Motherboard Power Connector: 8 Pin MB
SATA Power Connector: 9
Wattage: 850W




:wink:

 

[thebadtall]

Aha, i see, i thought it could be symmetrical, and so, this way, i cannot use it for heavy amplifier power supply !!

But if i could it would be a nice and really cheap sollution, since the 500W Psu in Greece costs 15eur, whereas a +/-24v 100va transformer costs 35eur...

Thank you !!!

 

[tpetar]

Yes my friend its true for prices, but transformer is multi generation device and that PC PSU is several month maybe one or few years device.

Nothing cant change good transformer.

I found, some old amplifier what my uncle and my father make when they was young and students, before many years. Amplifier has been exposed to rain, humidity, and rest bad environment states over 40 years. There is three transformers, all with rusted cores, copper wires like new, isolation papers bad but dirty, all dirty. And guess what happen with transformers when I try to activate them? They works!!! Of course its just curiosity, I dont have intentions to make amplifier right next to cheap and good HiFi devices.

:grin: