Re: No More USB-A Ports

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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