USB-PD and V charging confusion



Talking about Qualcom Quickcharge:

Because of that the Qualcom Ports are often very easy to distinguish:


As per my thread and battery monitor, my same charger charges the DVT3 with 17W (16.5 to 17W) at low current capacity.

It’s also worth mentioning the official prototype charger is rated 5V@3A (actually it’s likely USB-PD compliant)


People still buy cables from aliexpress etc which have no real way to know if they are adhering the usb-c spec


And also this page:


Yes, and that’s why we need to make sure everyone knows the danger.


Yes but everyone warns about the charger which are less likely to fail than the cables!
Buying a cheap cable or charger can more likely result in some damage but if you buy chargers and cable from e.g. Anker there is nothing to fear.
But that is not more or less than with every other electronic device. The V is not special about that.

It’s likely? What is printed on it? There should be some evidence that it increases voltage on it.



That means it is an USB-PD charger but deliveres Voltages/Currents which are not in the official specifications (I could find):



The newest specifications are here, but I cannot download it right now since the server is very slow…


Haven’t @Konstantinos mentioned that the “new” V charger would charge with 36W but according to your 2nd picture it’s not permitted.


The USB 3.1 Specifications are now donloaded and there are these Informations:

Source USB_PD_R3_0 V1.1 20170112 - redline.pdf

Therefore more Voltages should be possible


The second picture lists permitted and not permitted combos for examples of power values.
36W would be possible with 12V @ 3V as mentioned in the first picture (named profile 3).


The second picture was just from a draft of specification 2.0 maybe it was changed.
The last picture is from the official USB 3.1 Specification from
But I did not read the whole 600+ page document, I just searched for some specification of voltage and current of USB-PD


Regardless it’s still strange and confusing because as you said in the first pic (from 2012) the 36W - 12v@3A is listed but in the 2nd pic (from 2015) the 36W - 12v@3A is not permitted.


It’s not permitted for a 27W device / power adapter


That could it be! But thats somehow strange, because why should a 27W Adapter offer 36W?


Because it can offer 12V (12V @ 2.25A) and it can offer 3A (9V @ 3A) - why shouldn’t it offer 12V@3A also?
Answer is: Because it is only a 27W adapter. More than 27W can harm the adapter and/or the device. Therefore the adapter has limit not only current and voltages but also the combo of both dependent on its power rating.


Not only 5V, it also says 12V/2A, which is 24W.
@Alexander_Halbarth it’s very simple, 27W adapters support 12V operation but only up to a certain current limit (2.25A). The chart is just warning you that you can’t source the maximum PD current (3A) from a 27W charger on 12V, one of its supported voltages.


@pauliunas @s.auler I understood it I just mentioned that it is strange to write that in 27W mode the charger cannot output 36W.
Thats like saying you can drive with this wheel 130kph, but you cannot drive it at 160kph. Its just somehow redundant.


@Alexander_Halbarth, it should express the type of communication, the charger needs to take care of.
Example of a 27W charger:
Device: Hey, I want to be charged.
Charger: OK, here are 5V. I can deliver up to 3A.
Device: Gimme more…
Charger: OK, here are 9V. I can deliver up to 3A.
Device: Gimme more…
Charger: OK, here are 12V. I can deliver up to 2.25A.
Device: Hey, are you kidding? You just told me you can deliver up to 3A. Gimme that…

Good Charger: Nope. Just take what you get.
Bad Charger: OK, here are 12V and 3A… I’m gonna smoke now…

You just have to keep in mind, the tables above are written for engineers designing USB devices, not for customers.


I think @s.auler put it very well. It’s just a thing to keep in mind, because 3A is supported in all voltages except this one. So it’s a sort of exception for this one voltage.