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It might best explained with a diagram.

  • I currently have the V+/V- supply in the diagram.
  • I need to tap into the transformer to power up another circuit (lower portion of the diagram with the bridge rectifier)
  • The transformer that I'm using has two secondaries connected in series. The connected wires become my center-tap ground.

Is this possible? If yes, what changes do I need (if any) to make it work?

PS. apologies for the quality of the diagram. It's a mash-up I made using MS Paint.

Edit1: the existing supply is a regulated +/- 12V. The new supply will give me more than +12V.

Edit2: The 2 grounds are not connected.

Edit3: 0V in the first supply is ground

enter image description here

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    \$\begingroup\$ To be tested. Don't understand the wiring. Is 0 V ... the ground? \$\endgroup\$
    – Antonio51
    Nov 12, 2022 at 13:22
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    \$\begingroup\$ It depends if the node with ground symbol is connected to the node with 0V symbol. If not, it will work, but the extra circuit will just be comparable to the existing +V and -V nodes, so you lose the reference to existing 0V. So the problem is not can you do what you drew, the problem is, for what do you intend to use the additional output and how. \$\endgroup\$
    – Justme
    Nov 12, 2022 at 14:37
  • \$\begingroup\$ Hi mrjayviper, Your Edit 1 reads, 'The new supply will give me more than +12V'. It should read 'The new supply will give me more than 24 V'. \$\endgroup\$
    – vu2nan
    Nov 13, 2022 at 4:19

3 Answers 3

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Here's the appropriate schematic.

enter image description here

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  • \$\begingroup\$ I edited my original post. Does it change anything on your answer? I think your answer is no but just want to confirm. thank you. \$\endgroup\$
    – mrjayviper
    Nov 13, 2022 at 3:29
  • \$\begingroup\$ Hi mrjayviper, No, it does not change anything. \$\endgroup\$
    – vu2nan
    Nov 13, 2022 at 4:18
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Your circuit will work fine, and as it stands the two DC supplies will not interfere with each other. Of course, you must ensure that any power you derive from your additional supply does not overload the transformer. Any current you draw from your second supply is increasing the current through the transformer, over and above the amount that the first supply drew on its own.

The biggest issue you face may have to do with how the systems you connect to those two sources interact. You now have two ground points, the original labelled '0V', and your new one with a ground symbol, bottom right.

These are not the same, and by measuring the AC voltage between them, you will find a significant potential difference.

Consequently, any signal derived from a circuit connected to your new second supply will be relative its own particular ground, and in relation to the other supply's ground, it will look like a mess of noise and AC. You cannot solve this problem by connecting the two grounds to each other, because that will cause diodes to be short-circuited, and smoke to happen.

In other words, this arrangement will only be of any use to you if there will be absolutely no communication (or any kind of connection) between the circuitry on each DC supply. If all you want is to power a completely independent system from the second DC source, you are good to go. Otherwise you can expect serious complications.

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  • \$\begingroup\$ All that said, I am not sure why you would actually want to though. If they need to be kept independent anyways, you might as well just wiring off of the original +V and -V since that would accomplish the same thing and you just keep all that independent of anything else that uses the 0V. Still subject to the same restrictions but you don't need to go to the effort of wiring up a redundant rectifier. \$\endgroup\$
    – DKNguyen
    Nov 13, 2022 at 5:33
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You can double or triple the voltage by connecting another bridge rectifier. However, while voltage multipliers can increase the voltage, they only supply a lower current to the load. In this way, an additional 24 V power supply or a 36 V power supply can be easily made.

Voltage doubler circuit: enter image description here enter image description here Voltage tripler circuit: enter image description here enter image description here

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