Linear Bench PSU - Page 1
Forum section: electronics / beginners

author: D_Money22
author_rank: Newbie
timestamp: March 06, 2017, 03:35:25 pm
content: So, I have been fiddling around with various ideas recently and have begun work on what seems like a fun project idea, building my own lab bench psu. I know there are a bunch of topics on this already, and I have been trying to read through alot of them (they have been extremely helpful as far as brainstorming goes) however I'm not totally sure what I should work towards for this. I don't necessarily need it to reach 0V, nor do I need it to go much higher than 12V, and about 1A should be plenty. I would rather design the specific circuits myself, as this project is aimed at learning, but what I'm not sure about is what I need as far as protection goes. What elements would you recommend for my psu? I want low noise, so no tracking preregulator, but like what elements should I use for protection or other necessary or handy features? I've seen designs discussed ranging from little more than an lm317 circu it to circuits whose designs are even more impressive than even commercial PSUs, and am just unsure what I really need for my design.Thanks,Daniel

author: MarkF
author_rank: Super Contributor
timestamp: March 06, 2017, 03:58:56 pm
content: You might take a look at Peter Oakes power supply design for some ideas.

author: grifftech
author_rank: Frequent Contributor
timestamp: March 06, 2017, 10:00:23 pm
content: will a multi fixed rail work?http://griffinsworkshop.blogspot.com/2016/12/homemade-bench-power-supply.html(this one is mine),(I added a power switch after I wrote this blog post)

author: Cliff Matthews
author_rank: Unknown
timestamp: March 07, 2017, 03:14:59 am
content: Hello new member! LM317 circuits abound, so pick one maybe with another 317 cascaded to do basic current limiting. What puzzles is the use of the word "protection". I'd ask from what, but since you're learning stay away from open power transformers and mains voltages until you gain more experience.As a safe source (with fire "protection" and good isolation), use a class-2 wall adapter with an AC output so later you can regulate down to 0 volts:https://www.amazon.com/Hammond-Manufacturing-BPE2G-Transformer-limiting/dp/B005T7RT9E/ref=sr_1_1?s=industrial&ie=UTF8&qid=1488855221

author: eugenenine
author_rank: Frequent Contributor
timestamp: March 07, 2017, 03:16:57 am
content: Quote from: MarkF on March 06, 2017, 03:58:56 pmI can't find a link to the actual end product on his site, no schematic or anything.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 07, 2017, 10:35:12 am
content: @eugenenine - Peter Oaks is not selling a product, he is giving a lecture series if I recall correctly.

author: eugenenine
author_rank: Frequent Contributor
timestamp: March 07, 2017, 11:49:51 am
content: I'm meaning like a completed schematic of the power supply, or a picture of the finished one he built.

author: Avacee
author_rank: Unknown
timestamp: March 07, 2017, 12:44:41 pm
content: Peter Oakes has a playlist dedicated to that power supply and a DC Load sub-project he made so he could test the power supply.https://www.youtube.com/playlist?list=PL_atu5RtEPi4aNzoMtZ5_S6ruhFR98T_pThere is a schematic shown within the videos and on the element14 website (one of his sponsors)https://www.element14.com/community/groups/test-and-measurement/blog/2014/09/15/the-modular-bench-power-system-the-essential-diy-build-for-every-ee-student-and-old-timer-alike

author: D_Money22
author_rank: Newbie
timestamp: March 07, 2017, 05:20:10 pm
content: Thanks guys, this looks like basically the very thing I've been looking for. I tried to follow Dave's psu series, but quite frankly he went from 0 to 60 between episode 4 and 5 and I got kind of lost.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 07, 2017, 06:12:25 pm
content: The series from Peter Oaks linked here is also a little confusing / tricky with the speed. I only did a quick view over much of it, but from what I saw the initial part is really slow and at a very low level so easy to understand, but not much information. The really tricky part for the supply comes in the last part putting everything together and especially the late changes to the circuit to speed up the response. So something like 6 hours getting very little and the last 20 minutes for the residual 90%.There are still a few points missing, that need to be checked: Stability with difficult loads, transients on turn on and cross over between CC and CV mode. At least chances are good is will perform well at these points too.At least the shown circuit can reasonably work. The transient response is still relatively slow and thus a large output capacitor is needed. The MOSFET chosen (IRFP064) is not that suitable for more than about 15 V: it's a rather modern 60 V type and thus can have thermal stability problems. The DS does not show a DC SOA - so it is a little guess work on how high the voltage may be to make sure it does not blow up from thermal instability similar to 2nd breakdown. Chances are it will blow at 1 A and more than 30-40 V. A more suitable type would be a IRFP250. Though the power is limited - so no 5 A at 30 V, more like 2.5 at 30 V as the limit.