Topics Topics Edit Profile Profile Help/Instructions Help Member List Member List  
Search Last 1|3|7 Days Search Search Tree View Tree View  

Center Zero Bench Power Supply?

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Chat Zone » Archive through 26 November, 2016 » Center Zero Bench Power Supply? « Previous Next »

  Thread Last Poster Posts Pages Last Post
  ClosedClosed: New threads not accepted on this page        

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

mikeohagan
Just joined
Username: mikeohagan

Post Number: 1
Registered: 11-2016

Rating: N/A
Votes: 0 (Vote!)

Posted on Tuesday, 22 November, 2016 - 02:58 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi,

I have been following EPE, "Compact Hybrid Switchmode 100W Bench Supply articles (Sep to Nov-2016) with interest and have been looking at bench power supplies in Maplin & on-line.
They all seem to lack an option for a center zero supply - for example EPE, Dec-2016, page 58, Audio Out, fig 2, has an amplifier circuit with a +38>0>-38 volt DC power supply and don't many op amps like +15>0>-15 volt supplies?
My interest at the moment is digital but I don't want to invest quite a lot of time &/or money in a supply that might not support analogue amplifier circuits.
Some of the bench supplies I have seen have more than one output - can these be used together to give a center zero supply?
Is there a trick of the trade to produce a virtual center zero? (I've an idea that a resistive divider will not be good enough?) Am I failing to understand something obvious?

Many thanks,

Mike O'Hagan
Top of pagePrevious messageNext messageBottom of page Link to this message

741
Frequent Contributor
Username: 741

Post Number: 841
Registered: 08-2005


Rating: N/A
Votes: 0 (Vote!)

Posted on Tuesday, 22 November, 2016 - 04:16 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Assuming the PSU itself has good performance, I wouldn't really want to go to the trouble of making, say an op-amp plus power output stages add-on to get a split supply. Also, you compromise the PSU accuracy that way.

For a cheap PSU though, it could be a useful project.

To be able to chain PSU outputs then I think you need so-called "floating" outputs. Probably higher-end commercial PSUs allow this - but in that case the manual would expressly mention this.

Op-amps come in a huge range of supply specs.

All they care about is PSU polarity and not exceeding the max P.D. But a circuit application often uses a mid-rail potential to the non-inverting input.

Mostly a low-power circuit that uses split power rails would do the splitting on-board, maybe with a TLE2426, for lowish voltages.

A PSU is an investment, and I agree one has to think about the requirements, like noise, carefully.
Top of pagePrevious messageNext messageBottom of page Link to this message

dave_g
Frequent Contributor
Username: dave_g

Post Number: 915
Registered: 05-2005

Rating: N/A
Votes: 0 (Vote!)

Posted on Tuesday, 22 November, 2016 - 08:01 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Mike, have a look at Monster Bench PSU in the archives to Feb 2016 on CZ.

This is a serious beast, cost a fair bit and took months to build, although that included software design. I seem to get more noise that I should but have not yet had the time to investigate.

Looking at your post, you could copy me with effectively two linear regulated supplies, which can be coupled +ve to -ve to provide a + 0 - supply. My design uses a lot of automation to provide a digital reference, which is opto-isolated for each supply so they can be connected in this way. If you're happy to have two potentiometers, one for each supply, then just use or adapt my regulator design, it might at least give you food for thought.

Pictures of the finished beast are in that original post.
application/pdf
Livewire - Controller PSU.pdf (7.9 k)
application/pdf
Livewire - Earth Lift Relay and Aux Control.pdf (10.2 k)
application/pdf
Livewire - Regulator 20160214.pdf (17.6 k)
application/pdf
Livewire - Rotary Encoders.pdf (6.7 k)
application/pdf
Livewire - V1.pdf (15.5 k)
Top of pagePrevious messageNext messageBottom of page Link to this message

hackinblack
Frequent Contributor
Username: hackinblack

Post Number: 728
Registered: 09-2006

Rating: N/A
Votes: 0 (Vote!)

Posted on Friday, 25 November, 2016 - 04:30 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

heres a few examples of ways to make a virtual ground for a split-rail supply;using fairly common parts:-

http://www.goldpt.com/virtual_ground_circuit.html

Administration Administration Log Out Log Out   Previous Page Previous Page Next Page Next Page