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From: Dan Purgert <dan@djph.net>
Newsgroups: comp.misc
Subject: Re: No More USB-A Ports
Date: Mon, 17 Jun 2024 12:00:22 -0000 (UTC)
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On 2024-06-16, Computer Nerd Kev wrote:
> Dan Purgert <dan@djph.net> wrote:
>> On 2024-06-08, Computer Nerd Kev wrote:
>>> The USB-PD standards are interesting. Upon first reading about them
>>> I was keen to find/design a device to just break out the outputs
>>> and have a mini variable power supply for general use, even battery
>>> powered from one of those power bank devices. But as with most
>>> things USB3/C it turns out the power supplies that are actually
>>> available only implement the bare minimum range of voltage outputs
>>> that the manufacturers think most people will need.
>> 
>> 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?
All of my "5v(tm) devices" are certainly running lower voltages inside
-- batteries are only 3.7 to 4.2 volts (or thereabouts) anyway, and I
know my phone has a lot of 1.8 volt things inside.

I was more saying that I couldn't really think of anything that'd take
the middle voltages, given what I'm familiar with.

>
> But really what excited me were the newer PPS power supplies (USB-C
> 3.0 PD PPS, to use their full title). These are supposed to supply
> a requested voltage in 20mV steps between 3.3V and 21V+. The idea
> is to allow optimised battery charging by supplying a charge
> voltage/current specific to the state of charge that the battery is
> in. I just liked the idea of completely universal plugpacks, but
> when I went shopping for them (and granted they're quite new to the
> market in Australia) the models on offer had a much more limited
> voltage/current range.
>
>> Bear in mind that it's ONE output, and you negotiate the voltage on the
>> wire as part of the connection handshaking (IIRC CC1/2 or maybe
>> something more active later on, been a bit since I read up on how PD
>> works)
>
> 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?

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