Parallel switching power supply

Question

How to paralleling switching power supply? I want parallel my 5 x 30a switching psu so i can get 150a in total, I need completed diagram for to do it,help me, thx

geralds · Answer

Hi, yaps ---- it is 2070 watt (13,8V), or what I think it's for a battery voltage used in a car, isn't it? - then you have 14,4V_Batt. - then you get 2160 watt. hot. hot, hot...! I would suggest you buy a power supply with such power, because paralleling 5x PSU is absolutely not easy.. ..--for this you need double power reserve and you need use it at 50%. For example: https://www.artesyn.com/power-supplies/websheet/622/lcm3000-series It is not only the difference of the source impedances, and / or voltages, the max. source currents of each PSU. It is also the switching frequency, the thermal behaver in ambient and that of the machines. And so on. Then it is also the kind of loads, clear Ohm (pure resistor), or komplex impedances, xC, xL, jC, jL, or much more komplex, or dynamics of the sinks, and so on.... What kind of load do you use for these 150A? Is it for professional, or private usage? Best Regards Gerald ---

shabaz · Answer

Hi Dany,

As John says, there's a few issues to explore, such as failures, and the problem of different voltages from each supply.

I think it's going to be extremely difficult to achieve it anyway. Even 1 milliohm resistance will result in more than 20W of power being dissipated, so I can't see how you're going to construct this. What's the purpose of this supply, and why does it need to sustain 150A at 5V?

If you build a circuit for this, I don't think a normal PCB and connectors can be used. You'll have to start doing things like have copper bus-bars maybe, and special connectors.

If you look at Linear Technology website or search for 'load sharing' you'll find ICs that do a similar thing, and you can examine how they achieve it. Implementing that for 150A is probably a major task.

EDIT: just noticed you're asking about 12V, not 5V. That's into the kilowatts...

jw0752 · Answer

Hi Dany, You can probably hook the 5 units up by connecting the 5 positive wires and the 5 negative wires. Remember that the wire leading from the connection point to the load has to be heavy enough gauge to handle the extra amperage. If it was my set up I would put a 10 amp load on the parallel units and then use an ammeter one by one on each individual unit to see if it is contributing approximately 2 amps to the system. If you find that one unit is contributing 3 amps and another one is only contributing 1 amp you may have a balancing problem. Some switch mode supplies have a voltage trimmer that could be used to balance the system. If you open any of the power supplies use extreme caution as there is lethal voltage inside that may remain even after the units are unplugged. Depending on the type of load that you are going to put on the 5 power supplies another problem that you may have is start up over load. This would occur if one or more of the power supplies came on line quicker than the others. This quick power supply would try to supply the higher current and would shut down due to overload before the other supplies could come on line. Most Switching supplies have over load protection that causes them to shut down if they are forced to exceed their capacity. If you are really planning to power a load that will be drawing 150 Amps make certain that your power supplies are rated at 30 Amps continuous duty. Without more information on the voltage and the application will be needed to give you better advice. John

dany_76* · Answer

Hi john thanks for answer, yes my switching psu have trimmer for adjust voltage 12-13,8 i think, but what do you mean balancing the system? You mean i set all each psu on 12 volt same exactly? I just got other reference if i must put resistor in low ohm(mili ohm) and high wattage and diode in series to terminal output, also install voltage correction modul. But i am still not clearly because dont get diagram in detail with value also series/type of each komponen should i use.

jw0752 · Answer

Hi Dany, If you can change the power supplies to different voltages they will all have to be on the same but that isn't the trimmer I was talking about. A trimmer would allow us to adjust the voltages a fraction of a volt on either side of the designated voltage. Suppose we had one PS with a voltage of 12.2 Volts and another with 11.9 Volts. If these were hooked in parallel the one with the 12.2 volts would have to do more work than the 11.9 volt one. Trimmers would allow us to adjust both units to 12.0 volts. You are right, adding a low resistance in line with the power supplies will help with the balancing problem and the addition of diodes on each supply will protect them against failures in other power supplies. If you want touse these devices they will have to be properly sized. For example you should over size them. The diodes should be able to handle 40 Amps each. Note you will loose about 0.75 volts across the diode and at 30 Amps this will probably require the diode to be heat sunk. If you use a 0.01 Ohm resistor in series with each supply it will need to be able to dissipate 9 Watts but should be sized to at least 12 Watts and may also need to be heat sunk. About 0.3 Volts will be lost in the resistor so combined with the diode you will have 11 volts across your load. There are too many variables for me to say that this is the best way to do this with your power supplies. If I was in your place I would have to do some experiments and take some measurements. 150 Amps at 12 volts is a lot of power and frankly I have not had a lot of experience building in this power range. John

Parallel switching power supply

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