DIY Dual Power Supply - Page 1
Forum section: electronics / projects

author: Sp4wi
author_rank: Newbie
timestamp: April 27, 2015, 07:29:15 pm
content: Hi Guys!I got my Hands on a nice 39V, 440VA Toroid and i would like to make it into a variable Dual Power Supply. Does anybody have a project on that? I am thankful for any kind of help.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 27, 2015, 07:50:29 pm
content: 440 VA sound like rather high power. At this level one usually does not use just a simple linear regulator, but something like multiple transformer ranges or a pre-regulator.A dual supply often needs 2 separate windings.Is it just one Winding 39 V or are there other voltages available ?

author: SeanB
author_rank: Super Contributor
timestamp: April 27, 2015, 07:55:31 pm
content: This was discussed here recently. Good as a start.http://electronics-lab.com/projects/power/001/

author: rdl
author_rank: Super Contributor
timestamp: April 27, 2015, 08:20:38 pm
content: As already mentioned, It really depends on how your transformer is made. Does it have a single secondary or does it have dual windings? If dual, are they separate or center tapped?A good place to start would be to download and read the free pdf which contains the table of contents and the complete chapter 9 of the Art of Electronics, third edition. That sample chapter is over 100 pages and is all about power supplies. I think the link in this blog post is still good. If not, it still shouldn't be too hard to find.http://www.wisewarthog.com/electronics/horowitz-hill-the-art-of-electronics-3rd-edition.html

author: Sp4wi
author_rank: Newbie
timestamp: April 27, 2015, 09:00:11 pm
content: Thanks for the suggestions so far. The transformer has two 39V Windings and is center tapped. I was thinking of controlling DC-DC converter with a microcontroller. Any ideas on that? Is this even viable at a few amps?

author: atferrari
author_rank: Frequent Contributor
timestamp: April 27, 2015, 10:46:10 pm
content: Quote from: Sp4wi on April 27, 2015, 09:00:11 pmWith much less current capability I got a transformer that under an almost 3 A load ensures to supply steady 35 Volts on each rail.Using a small micro I managed to vary the output of a pair LM337 / LM317. The opamps in place were something like MC33??? able to take the high voltages as power supply. I abandoned the project when I confirmed again that I do not know how to avoid oscillations / unstability.Also I learnt that having a switching preregulator, makes your life easier.Still in my to-do list.Interested on all this.

author: atferrari
author_rank: Frequent Contributor
timestamp: April 27, 2015, 10:49:29 pm
content: Quote from: rdl on April 27, 2015, 08:20:38 pmMy stupid Win XP insists in telling that the site above has invalid certificates. Could anyone help me by getting that chapter so I can download it from another "potable" site?

author: edavid
author_rank: Super Contributor
timestamp: April 28, 2015, 01:54:04 am
content: Quote from: atferrari on April 27, 2015, 10:49:29 pmFirefox on Win XP has no problem downloading the file from Dropbox.

author: prasimix
author_rank: Unknown
timestamp: April 28, 2015, 06:16:59 am
content: Quote from: Sp4wi on April 27, 2015, 09:00:11 pmOf course that is viable.Hereis my current project and it's tested with up to 3A or up to 5A with lower voltage (in the range of 30V that is close to your transformer). Two main goals of the project is to have completely silent PSU (no fan) and due to that is used SMPS pre-regulator (I'll also test a blackdog'smosfet pre-regulator). Another goal is possibility to control main functions manually or via MCU (currently Atmega32u4 programmed using Arduino IDE).

author: dom0
author_rank: Super Contributor
timestamp: April 28, 2015, 07:43:59 am
content: Quote from: Sp4wi on April 27, 2015, 09:00:11 pmHP E3630A. Switch ranges with the center taps.