wagiminator
commented
1 year ago Hi, I don't think this is a reasonable replacement for a lab power supply (nor should it be). On the one hand, the selection of output voltages is limited, and on the other hand, it has no current limit or robust short-circuit protection.
elektrinis
I have a 30V5A "analogue" lab PSU that's 20 years old and is bulky, inconvenient to store and a pain to hook up every once in a while I use it. By "lab PSU" it means that it has a really fast current limiting: for example, if set to 30V and 2A, and suddenly connected to a 12V battery, it limits the current properly (without overshoot), and it keeps working, charging the battery.
Knowing about QC3 and above versions ability to set voltage, I started my search for a smart QC decoy that would act as a smart lab PSU and I could store it in my small drawer, where I keep my TS80P (USB) soldering iron as well. An I have landed on this project. It is the closest thing I've found so far, but not quite there yet.
Some devices have appeared recently, like this one, but after testing a couple of chinese units (not the one from my link, but I don't expect anything else) I quickly realized they are not capable of doing proper current limiting - they just crash if sudden current spike happens (i.e. in above example). From your experience, can a standard 65-100W laptop brick limit the current, and be FAST at it?
And I think we would need QC5 to get >100W? Are there any chips for that, or perhaps it is possible to emulate the commands in software, like some keyboard and serial AVR solutions were done back in the day? For example there is arduino code for QC3, so the chinese chip could probably be discarded.
An alternative would be to add a couple of opamps and a beefy bipolar transistor and run it in linear mode, with the USB PSU running just a tad higher than set voltage, to keep the BJT from overheating. Then, if current limiting is detected, the PSU should be commanded to lower its voltage quickly to keep the BJT happy. This is how some old school "efficient" audio amplifiers worked before class D took over.
Anyone looking, or even found a thing like this I could just buy? Or we could just go in to developing this. I have enough knowledge to do it all, but I'm short on time, big time. If someone would be willing to do the firmware and routing, I could come up with the analog power stage to make this happen.