Guidance for DIY Bench PSU - Page 1
Forum section: electronics / projects

author: D_Money22
author_rank: Newbie
timestamp: March 06, 2017, 04:49:49 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. If anyone has any ideas/advice or can point me towards any resources that would be awesome.Thanks,Daniel

author: ZeTeX
author_rank: Frequent Contributor
timestamp: March 06, 2017, 07:11:55 pm
content: Quote from: D_Money22 on March 06, 2017, 04:49:49 pmSounds like bullshit because every PSU thread at least mentions if the PSU has adjustable current limiting or no, and you didn't specify if you want current limiting or no. literally you see it on every thread.So, if you want adjustable current limiting the best topology is something like this:its from HP E3620 manual, you can pretty much copy the schematic onto a perfboard and it will work but it can be improved.notice you must have duel secondary transformer for this or use a galvanic isolated DC/DC converter. (costs like 1$ on eBay).

author: D_Money22
author_rank: Newbie
timestamp: March 06, 2017, 07:59:14 pm
content: I know about current limiting and I have a copy of the hp handbook thing, I do plan on implementing that in any final design. What I was looking for was more of clarification on what a psu really should include. I've seen some threads discussing these monster designs that have features I don't even understand how to use much less design, and then others are some barebones designs relying on a basic linear regulator ic. I don't plan on using an ic, all my current plans are based around an op-amp solution, but what I'm wondering is, aside from the typical voltage regulation and current limiting, what features are worth putting into a typical bench psu. For example, what safety features should I include, aside from fusing and some form of overvoltage protection?Thanks,-Daniel

author: Kleinstein
author_rank: Super Contributor
timestamp: March 06, 2017, 08:31:29 pm
content: It might be a good idea to have some protection from over-temperaure, as power supplies tend to get quite hot.With only 12 V and 1 A this might not be needed. The same is true for switching of transformer taps.Some supplies have a crow bar circuit, to short the output in case of an over-voltage - it might be a good idea in some cases (e.g. powering an digital circuit), but also can be a disaster (when charging a large accumulator).Another feature sometimes found are external sense wires, to sense the voltage closer to the target. This is somewhat needed for ultimate precision - however it adds complexity and often is difficult to combine with a fast transient response. External sense wires also allow more user errors.Some supplies are capably to operate 2 or even 4 quadrants - that is also sink current in a controlled manor - depending on the circuit used the effort for 2 quadrant operation might no be so large.Depending on the metering circuit one could have extra outputs, like peak currents, RMS values for AC current. With digital control there is the option to have such things as controlled (slow) ramps and maybe even a slow kind of AWG functionality.

author: D_Money22
author_rank: Newbie
timestamp: March 06, 2017, 08:49:37 pm
content: Awesome, those are some great ideas. Since the primary focus of this project is the learning from the development and circuit design, even if I don't end up incorporating an idea the process of brainstorming and design is very helpful.