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Let's take my 30W USB-C Apple power supply as an example: https://www.apple.com/shop/product/MR2A2LL/A/30w-usb-c-power-adapter. Printed on it are 4 outputs:

  • 20V / 1.5A
  • 15V / 2A
  • 9V / 3A
  • 5V / 3A

Are these fundamentally discrete charging profiles between which the power supply can switch or is its output a continuous spectrum of voltage and amperage determined by the device drawing the power and the printed outputs are examples of possible output profiles?

user2990590
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  • Note that these are not charging profiles, they are just fixed voltage outputs. You can't connect these voltages directly to a battery and expect it to charge properly. – Elliot Alderson Jan 21 '19 at 20:06

1 Answers1

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Best to read a summary of USB-C Power Delivery spec.

These are discrete voltage output levels. The amount of available current is specified for each discrete voltage setting.

Note that the default voltage / current is 5V @ whatever current is specified. Higher voltage output is negotiated when the power supply is connected to the device being powered.

[Edit]

Here is a link to a ST PDF file that talks about USB-C and Power Delivery (PD) ST PDF file

Dwayne Reid
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  • OK so it sounds like if it is plugged into a "dumb" non-USB-3.0 device, it will default to charge at 5V and whatever current is drawn by the device. But if it is plugged into a USB-3.0 capable device, then the device can request one of those discrete higher voltage profiles? Correct me if I'm wrong about any of that. – user2990590 Jan 22 '19 at 15:23
  • Close. I do not believe that USB-3.x can request any higher voltage above 5 Vdc. I think that only USB-C can request the higher voltages. That said: I could easily be wrong. Bottom line is that the power brick defaults to a voltage that won't damage anything. – Dwayne Reid Jan 22 '19 at 23:35