Message-ID: <6670c7c1@news.ausics.net>
From: not@telling.you.invalid (Computer Nerd Kev)
Subject: Re: No More USB-A Ports
Newsgroups: comp.misc
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Dan Purgert <dan@djph.net> wrote:
> On 2024-06-16, Computer Nerd Kev wrote:
>> Dan Purgert <dan@djph.net> wrote:
>>> Mine here are all 5/9/15/20V.  I "think" they're missing only 1 or 2
>>> voltages, but that's enough for my laptops and cell phones.  Not really
>>> sure what'd ask for 9 or 15 volts ... 
>>
>> 9V plugpacks are pretty common for stuff I use, it's typical for
>> devices that reduce that to 5V internally. Similarly 5V devices
>> generally use 3.3V internally. My laptop's power supply is 16V, so
>> 15V might work.
> 
> Not sure what a "9v plugpack" is -- maybe something leaning a little
> more "professional grade", like what photographers tend to carry about?

As Rich suggests others call them wall warts, though I thought
plugpack was actually the more universal term for them. Power
supplies with a mains connector built into the enclosure, including
USB ones. Not only supplied with things that charge batteries or
perform computer functions.

>> Yes it's all rather complicated, but in theory a device to allow
>> manual control of the output could be quite cheap because there
>> are chips designed for doing that in relatively dumb USB-C-powered
>> devices. However I found a project online from someone who'd tried
>> making a bench power supply adapter from a wide-range USB-PD PPS
>> power supply and they found the outputs were so far off what was
>> requested that they ended up setting it to a fixed output and used
>> another regulator for the final output. So not using the voltage
>> programming ability of the USB power supply after all. I realised
>> then that I was probably wasting my time - it's a standard for a
>> perfect power supply, which might only be used to make
>> barely-good-enough-to-sell power supplies. I shouldn't really have
>> been surprised.
> 
> Happen to have a link to the project?  Or was it something you came
> across ages ago?

It was a while ago and if it's the one I found now in my bookmarks
then it's not clear if they were actually using a PPS USB supply
anyway. I've probably been mis-remebering again:
https://tokarski.dev/posts/bench-power-supply-usb-c/

Likely it was just the limited specs of the PPS power supplies
available in Australia put me off the idea, but that was probably
at least six months ago so I should look again.

This article describes charging Li-Ion cells by using a USB-C
development/testing tool to control a PPS one:
https://ripitapart.com/2022/12/31/directly-charging-li-ion-batteries-with-a-usb-c-pd-tester/

That does suggest their current regulation can't be relied on:

"Although the PPS specification allows a device to set a maximum 
 current level, my own testing revealed that there was too much 
 variation amongst all my different adapters that I could not rely 
 on the hardware to perform the constant-current regulation with 
 enough precision for my liking"

But it seems the voltage regulation from the ones he tested was
acceptable.

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