Christian SeligDec 28, 2024

Maybe dumb question: I have a USB-A (not C) port on a powerbank that can output 5V 3A *or* 12V 1.5A. I have a little monitor that only accepts 12V (and consumes max 0.8A)

This powerbank's USB-A port would be great in a pinch to power the monitor (via a trigger board or something) but the port seems to default to outputting 5V, is there an adapter or trigger board (or something!) that I could get that would make it output the 12V?

Show threadZimmieDec 28, 2024
@christianselig It depends on what the power bank uses to select the voltage. Is it expecting USB-PD negotiation and the monitor is expecting 12v with no negotiation? If so, you could probably make a device which negotiates USB-PD with configurable voltage (compiled in, set by jumpers, whatever) and spits it out as DC.
Show threadChristian SeligDec 28, 2024
@bob_zim On the USB-A ports it can't be expecting PD negotiation, can it? That's why I assumed it was QC if it was able to output 12V
Show threadZimmieDec 28, 2024

@christianselig USB-PD is just a negotiation protocol. It’s rare, but it can run on Type-A, especially if you don’t need the data lines to do anything.

Though now that I think about it, USB-PD can only do 5v, 9v, 15v, 20v, 28v, 36v, and 48v. There’s no option for 12v, suggesting the power bank is using another protocol.

Show threadChristian SeligDec 28, 2024
@bob_zim 12V is an optional part of the PD protocol, but pretty much everyone implements it
Show threadScott Gruby
@christianselig @bob_zim In the handful of USB-C chargers I have, only 3 support 12V. The rest (3 or 4 of them) do 5V and 9V, some do 15V and 20V. I thought USB-C solved everything. (I just got a USB-C to 12V barrel connector for some radios that only outputs 12V with those 3 chargers).
Dec 29, 2024 at 12:46amMona for iPad
Show threadChristian SeligDec 29, 2024
@sgruby @bob_zim USB-C is kind of a mix of "it depends" 😛 If you want further fun look into the optional PPS part of the PD protocol and you can get virtually any voltage you want between 3 and 24V!