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How to parallel two SMPS?

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arvinfx

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Hi,I have two computer power supply , I need to have +12V 40A. each of them has 20A .
How can I share the current bettwen this two smps?

Somewhere I read an article about this that said we must use one of them as a master and another one as a slave but how?
 
To use one as a master and one as a slave, the master must control the switching frequency and duty-cycle for both. That means looking at and understanding the circuit schematics to understand how this would be done.

Otherwise you could try placing a small resistor in series with each output to help balance the load. A 0.01Ω resistor, which would drop about 0.1V at 10A would likely work. You could make such a resistor with about 1 foot of 20AWG copper wire.
 
Howdy, you could also run each through a schottky diode: low drop & no chance of supplies fighting each other.
The master/slave method is better, but with schottkys as well, any transformer difference is negated. G.H. <<<)))
 
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Thanks
But I have to mach this two in master/slave mode. can you give me a sample? or schematic?
I made a lot of smps .
 
Unless you have a schematic of the smps's you have that you can post, it's not really possible to give any further suggestions.
 
Power supplies that are designed to be used in parallel have extra circuitry inside to support that ability. There is usually an extra pin or two that allows the supplies to 'talk' to each other. They each make small adjustments to their own output voltage so that they each supply their share of the load current.

Otherwise, you can parallel generic PSUs with resistors or diodes but, without the extra internal circuitry, there is no way to ensure that they share the load current equally.
 
I have repaired a lot of smpses, and have made them ,If you guys give me the basics or a sample shcematic I will do it, anyway I can take a picture of them and put it for you. if it is necessary.
 
Have you tried just hooking them both up together through amp meters and putting a load on them to see if they pull down nearly equal?

If you can set their individual output voltages to within .1 -.2 volts of each other at no load the odds are their own internal resistances and line resistances will probably balance them out close enough.

I have yet to ever see a pair of matching power supplies where one was so tightly regulated that it would not share output capacity with a second one.

The other thing it that if you need 40 amps of source power I would seriously consider running three power supplies together being that pushing SWPS's designed for computers at their peak operating currents on only one output with no overhead tends to just be asking for trouble.

What do you need the 40 amps at 12 volts for?
If its for audio amplifiers or to drive servo or other electric motors you will money and problems ahead to just go out and buy a good heavy duty 40+ amp charging rated battery charger and add a few large capacitors to its output and turn it into a high current DC power source.
 
I know what you say. but heat might change my regulat.
This is for testing a power amp for car.

please look at this:


buckxcurrentxsharingxpeakxcurrentxmode.gif

Orginal site

**broken link removed**
 
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When connecting ATX power suppy, it needs a circuit which can power on / off second SMPS
ATX on off signal is on Green wire, when its pulled to GND , SMPS switches on, its by default pulled high by smps circuit.
 
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