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From: Theo <theom+news@chiark.greenend.org.uk>
Newsgroups: comp.misc
Subject: Re: No More USB-A Ports
Date: 17 Jun 2024 17:37:52 +0100 (BST)
Organization: University of Cambridge, England
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Dan Purgert <dan@djph.net> wrote:
> 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.

A number of things which charge at medium speeds - 20-45W use the 9 or 12v
rails.

I have a Dell 130W USB-C charger which doesn't do full PD - it's only 5V or
20V (at 6.5A each).  They skip the 9V and 15V modes because their laptops
only really care about 20V (and they provide 5V because that's compulsory). 
However that will only slow charge a Pixel phone (which fast charges on a
45W brick).

The reasoning is that you get 3A out of the 5/9/15V rails, so the Dell
charger is only able to provide max 15W, meanwhile the 45W charger can do
3A@9V (=27W) and 3A@15V (45W).  The phone is I think selecting the 9V rail
to charge faster, and presumably can't handle the 20V input.

Theo