Re: No More USB-A Ports

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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