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I currently have a 24V - 5A power supply in a commercial product that may require upwards of 8A from the load. Ideally, I would just hook up another 24V - 5A power supply in parallel and not worry about the overcurrent. However, I know that this is an issue because of the slight differences in voltage from each power supply (they will fight til one dies).

Is there any way for me to boost the amperage available of this power supply safely without completely replacing it? Footprint is an issue since this is a commercial system, I have about 4" x 2" of space in my box.

For background, I am a degreed electrical engineer, but did not focus on circuit theory (went more of the emag/nuclear route).

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  • \$\begingroup\$ Pretty much all power supplies won't actively 'pull down' overvoltage on the output. They are all one-directional devices that can only pump energy into the load. They will not 'fight' for control. What can happen, though, is current mismatch between the two supplies which lowers the maximum allowable current to some value under 2x the nominal output. \$\endgroup\$
    – user36129
    Mar 7, 2014 at 17:59

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If the power supply outputs can be put in series (i.e. their 0V ends can be "lifted" from ground) then you get 48V @5A and you can probably get a cheap off-the-shelf buck regulator that will convert down to 24V @9A. If you were designing from scratch I'd consider this part: -

enter image description here

The above circuit is shown generating a 12V output from inputs ranging from 15V to 60V. If both power supplies are connectable to produce one at 48V then the above circuit, with ratio modification to the two resistors in the red box will easily produce 24V. However, I'm sure you could pick something up from a chines source or ebay for ~$10.

If they both have to be grounded then you could use a H-bridge driver chip where one half of the H bridge is powered from one supply whilst the other half is powered from the other 24 v supply. Maybe something like this.

Or you could have both supplies individually driving their own 12V flyback converters and wire the outputs in series (transformer outputs are used in flyback converters). This will work too.

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  • \$\begingroup\$ Thanks for that quick answer! By no grounding issues, do you mean ground-loops? I would be grounding all of the supplies to a common chassis. Are buck converters controlled via a POT or something similar? How do you get the right voltage and current out of it? \$\endgroup\$
    – jareddbh
    Mar 7, 2014 at 17:32
  • \$\begingroup\$ Can one of the two 24V power supplies be "lifted" (or raised) from ground to be put in series with the other power supply. \$\endgroup\$
    – Andy aka
    Mar 7, 2014 at 17:37
  • \$\begingroup\$ This shouldn't be a problem. they have ground pins available, so I do not have to directly ground to the chassis. One could go to the chassis and the other could go to the positive lead of the other power supply. \$\endgroup\$
    – jareddbh
    Mar 7, 2014 at 17:46
  • \$\begingroup\$ OK then take a look at the change to my answer. You should be able to buy something off-the-shelf though. \$\endgroup\$
    – Andy aka
    Mar 7, 2014 at 17:55
  • \$\begingroup\$ Couldn't be more helpful. I would upvote if I could, but I'm a new user! Thanks! \$\endgroup\$
    – jareddbh
    Mar 7, 2014 at 18:24
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Some power supplies are designed to allow paralleling. We have a 300A/28V supply that consists of three 100A 28V supplies in parallel.

Note that it should explicitly say that paralleling is allowed in the datasheet or manual, otherwise your instincts about it being a Bad Thing are probably on the mark.

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  • \$\begingroup\$ Thanks for this. I will check into that and/or possibly get parallel friendly power supplies for future projects. \$\endgroup\$
    – jareddbh
    Mar 7, 2014 at 18:28

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