Isolated transformer ground doubts

Question

I've been designing a power supply for an audio system and for the new version I was thinking of doing that with the transformers totally isolated.

Can I connect the grounds like I drew it in the picture?

The transformer normal is the usual one that I'm familiar to, the transformer is what I want to make for the new version and the question is if I can joint the GND as you can see in the picture.

Thanks in advance for any kind of suggestion

That's fine for electrical safety and functionality. Remember though that audio systems are very unforgiving of ground loops, when trying to get the hum level inaudible. You may need to experiment with where you take that ground point, and your audio input and output grounds, to a common ground. — Neil_UK, Mar 17 '23 at 11:25

score 4 · Answer 1 · answered Mar 17 '23 at 11:41

Yes that is the way you do it.

If you want a +/- 24 VDC supply with common ground you must connect the grounds anyway.

It likely does not make much difference if you use two separate secondaries, or a single center tapped secondary, or use a transformer with two separate secondaries and connect them like it was a single center tapped secondary.

So the two completely separate secondaries separatelty rectified is possible but it might be simpler and cheaper to use it as center tapped secondary.

score 4 · Answer 2 · answered Mar 17 '23 at 14:52

You can connect them this way, but there's little point to doing so. It is counterproductive by any imaginable measure. It degrades performance. You're adding effectively two high peak current diode drops into the supply, so the voltage from "+24V" to "-24V" rail will be about 2V lower, and there's more power dissipation in the bridges.

Instead, I'd suggest using a center-tapped output and a half-bridge for each rail - either with a transformer with a center tap, or connecting two secondary winding ends together to form such a center tap.

score 3 · Answer 3 · answered Mar 17 '23 at 11:06

the question is if I can joint the GND as you can see in the picture

Yes you can do this. The two secondary windings are totally galvanically isolated and, they won't care how you make a single connection between them. Here's an example from this question: -

score 3 · Answer 4 · answered Mar 17 '23 at 11:47

Not only can you connect the positive and negative supplies like that, you need to if you want a bipolar supply. Where exactly they connect is going to matter as far as ground loops are concerned.

Another way to do it would be to connect the two secondaries together as a center-tap and use one bridge rectifier with the center-tap as ground. The drawback to that is that the rectifier needs to handle twice the voltage.

Where you might use dual secondaries with no common ground connection is if you were having a separate supply for each channel.

Isolated transformer ground doubts

4 Answers4