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Sharing 0V DC ground of linear and switching power supply?

bh
Prodigy 30 points

Hi Guys, first time poster here.

I have 2 power supplies I need to integrate to operate one machine, was wondering if they could share DC ground (0V) on their outputs. They will also share their AC ground (green wire to metal cases) but I'm talking about sharing their isolated output grounds.

Supply 1 is a linear bipolar regulated +/-24VDC

Supply 2 is a switching +48VDC


Both supplies outputs are iolated (floating from AC chassis ground), with a cap from the switching DC output ground to AC chassis ground. The linear supply DC ground also is iso from AC chassis ground but I dont know how, if its a cap from ground or what. Im wondering if I can safely share their DC iso grounds. Besides safety, Im also worried about possible noise from one supply getting into the other riding it's common DC ground rail (this power supply is for sensitive audio equipment).

I hope I was clear, as Im not an EE but a tech.

Thanks,

Bob H

  • 0
    TI__Genius 9130 points
    Bob,

    Can you post schemetics or a block diagram showing how each power supply is powered from the AC input, and how the outputs are generated in each case?

    This will help us to understand your configuration better, and advise you accordingly.

    I would initially say that if you can keep the output ground rails separat, it's possibly better for noise etc. What benefit do you get, or what is the motivation to tie the grounds together?


    Thanks,
    Bernard
  • 0 in reply to Bernard Keogh
    Prodigy 30 points

    Hi Bernard,

    Thanks for answering. I will try and find schematics of the 2 supplies to post pics of here, but so far all I have is a block diagram of the switching supply. The linear bipolar is an old 80s "Power One" brand module, very popular for diy projects. The switching supply is a "Mean Well" RS-15-48. Block Diagram pic attached. The reason they need to share output ground is the supplies are externally mounted in a remote box, with a hardwired 4 pin cable to audio unit already wired for shared common ground throughout, so all I have is 4 pins to work with common 0V, +24, -24, +48.

    Thanks Bernard. I will try and find the block diag or schem for the linear "power one" bipolar next.

    Bob

  • 0 in reply to bh
    Prodigy 30 points
    OK just following up to my original post. I connected both the linear and switching power supply output 0v DC "grounds" together, and that worked to supply the unit voltages, but because this is to power sensitive audio equipment, it did produce audible high frequency noise bleed into the audio, which is what I feared it might from past experience with switching power supplies and audio, unless properly filtered out, create such an issue, but in higher end audio, switching supplies have been properly integrated without noise in some of the worlds finest and highest pricest audiophile amps, recording studio gear, and concert hall power amplifiers, so it's a matter of design and cost, as this is a $10 power supply, so not filtered enough for audio use. So I removed the switching supply and use a linear one along with the original linear and will have no problems.