If I wanted to make a USB desk fan from a spare CPU fan (input: 12V, 0.15A), could I just solder a resistor to the positive lead of the USB wire? I plan on getting an adjustable voltage booster, but I was curious if this was possible. I think I would need a 13 ohm resistor for USB 3.0.
12v is not mandatory in the latest PD standard but it is still allowed and many PSUs implement it. I got a few inexpensive USB C connectors wich negotiate 12V out of compatible blocks specifically to convert to PD 12v devices like my shaver.
I try to shy away from recommending anything that’s not explicitly called out in a standard for that reason… quite a lot of chargers or PC motherboards do support both QC and USB-PD, but many also don’t, and you’ll always land on the wrong side of Murphy’s Law trying to rely on manufacturers supporting both.
That’s not what I was saying, PD included 12v up to 2.0 (I am going from memory) so it’s not multi standard support but retrocompatibility from modern PD to the older version
Edit: I checked and the requirement was removed from rev 1 to rev 2 so now it’s optional