Good way to create + and -  DC voltage from a single DC supply? - Page 1
Forum section: electronics / beginners

author: pendoric
author_rank: Contributor
timestamp: December 15, 2020, 09:14:17 pm
content: I am trying to find good solutions for creating + and - supply from a single DC supply. (Not a bench supply this will be a PSU in my device).For example if I have a DC 12V (rated 3.7A) supply. How could I get -6V GND +6V? Also could I get -12V GND +12V? Obviously at less AMPs as the total potential will now be 24V.I can and do understand how to use say two floating bench DC bench supplies in series to do this. I also can see how to use the secondary transformer winding in AC with 2 taps and rectify from there but what If I already have a single 12V DC supply I need to use?I also thought of just putting in a voltage divider and using the center of that as some sort of 'fake' ground but i'm a) not sure that would work well and b) I think it would be forever consuming current. Would that even remain at the constant voltage mid point as it sinks current sent to it? How would I determine resistance values?Anyway would love some pointers on good ways to do this.I have dug in the forums, online and even YouTube and I just keep confusing myself more and more.Thanks in advance.

author: TimFox
author_rank: Super Contributor
timestamp: December 15, 2020, 09:21:08 pm
content: If your current draws on the positive and negative outputs are almost equal, then a "rail splitter" circuit can be handy. For very low currents, a simple op-amp circuit would suffice, so long as the difference in currents (i.e., the current in the "ground" wire) is within the capability of the op amp. Some interesting suggestions are found inhttps://www.tubecad.com/2018/02/blog0412.htm

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2020, 09:26:31 pm
content: There are lots of off the shelf DC-DC converter modules that will do what you want. I used one most recently to get +/-15V rails for some op-amps from a single 3.3V supply.

author: ledtester
author_rank: Super Contributor
timestamp: December 15, 2020, 09:29:59 pm
content: QuoteHow much power do you need on those rails?For smaller amounts a charge pump circuit might work for you:https://youtu.be/a0pVLbtLWmY

author: msat
author_rank: Regular Contributor
timestamp: December 16, 2020, 12:07:10 am
content: Do you definitely need dual rails? Can you shift your signal(s) up so that they reside between VDD and VSS?

author: pendoric
author_rank: Contributor
timestamp: December 16, 2020, 12:31:47 am
content: Im just musing ideas but currently looking to power a small audio amp from it so it will need at least a moderate current.Its not like its for a stage show but needs to be fairly loud and driving only a 8 Ohm.Thehttps://www.tubecad.com/2018/02/blog0412.htmlink looks promising. As a noob it will take me some time for digestion but a quick skim seems to involve amp examples also.The follow on would be to read in multiple microphones and connect to a micro controller over I2S or similar, I dont think i need split rails for that or the microcontroller.

author: james_s
author_rank: Super Contributor
timestamp: December 16, 2020, 03:06:31 am
content: Have you considered a class D amplifier? There are some really inexpensive chips now, you can even get a complete board for not much money that will run off 12V and produce room filling volume. I think the one I have is 2x10W or something like that, cost just a few dollars and with reasonably efficient speakers it gets louder than I'd likely ever want it.

author: TimFox
author_rank: Super Contributor
timestamp: December 16, 2020, 03:37:44 am
content: If you run an audio amplifier from a single power supply, you can connect the speaker load after a large (polarized) capacitor (roughly 2000 uF for an 8 ohm speaker, or 4000 uF for 4 ohms).