Switch mode power supply and virtual ground

mrkva

Hi guys,

I am planning on building a little box with bunch of oscillators as addition to my modular setup. I am considering use of switch mode power supply from laptop (I am planning to travel a lot and transformers are just too heavy).

So I want to make this right, and as clean as possible. Any ideas? I have 20V supply, so I'll be creating +/- 10V supply with virtual ground. If you have ideas how to improve virtual ground creation, I want to hear them.

I saw something like this:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

, I understand it helps to compensate for instabilities. I would add a bit more filtering to it (pair of 2200uF caps)... what else?

Thanks,
Jonas

JovianPyx · Posted: Sat Jan 12, 2013 9:11 am Post subject:

I haven't seen this circuit before, but it looks like a kind of regulator. The transistors are capable of as much as 100 mA through collector-emitter. This may be beefy enough for what you want to do. Seems a bit more capable than the typical opamp fortified virtual ground.

The bottom line for virtual ground is current. The virtual ground must be able to source and sink current as well as a real ground in order for the virtual ground to stay quiet. If the demands of the circuit are more than the virtual ground can handle, it will become noisey and make a mess of your signals. The more oscillators (and other stuff) you add, the closer you come to the point of "not working well enough".

I always recommend not using virtual grounds, but given your requirments, there may not be an alternative. I would give this a shot on the bench and see what happens. It would be a good idea to have a good bench supply handy so that if you suspect the virtual gound as a problem at some point, you can power with a good/proper PSU and see if the problem goes away.

mrkva · Posted: Sat Jan 12, 2013 9:19 am Post subject:

Thank you. Yeah, I would also rather use a transformer and proper ground. But on the other hand, I am sick of carrying heavy cases to performances where 80% of the weight is transformer. I know TipTop audio provides this module, which apparently can do the trick from regular laptop supply. Some people on muffwiggler mentioned it is quite nice even for sensitive stuff.