Electronic – Does USB power delivery support arbitrary voltages

powerpower supplyusbusb-c

I'm looking for a USB power delivery power adapter to charge my Canon EOS RP camera via its USB-C port. Canon sells its own adapter for insane prices, and the Canon adapter is apparently nothing but a USB power delivery adapter, so according to my logic, a cheaper adapter should work.

One adapter (90 W) I'm looking at says in the specs:

  • 5-18 V / 5 A, 19-20 V / 4,5 A

Another adapter (65 W) I'm looking at says in the specs:

  • 5 V / 3 A, 9 V / 3 A, 12 V / 3 A, 20 V / 3,25 A

The adapter with only 5V, 9V, 12V and 20V is significantly cheaper.

According to Wikipedia, USB power delivery supports 5V, 9V, 12V, 15V and 20V in its different versions. Wikipedia doesn't say anything about adjustable voltage. The cheaper adapter entirely lacks 15V.

Because of the adjustable voltage, the 5-18V, 19-20V adapter seems like a better purchase. But, does USB power delivery actually support freely adjustable voltage? Or is the freely adjustable voltage of the more expensive adapter just a marketing trick?

The higher power of the first adapter doesn't matter to me as charging a feeble 7.4V 1040mAh battery doesn't require that much power.

Edit:

A report on the 'net says:

Just incase anybody was wondering… I got the official Canon PD-E1 USB-C adapter (it's included with the battery grip) and the output listed on it is 5V/3A and 9V/3A.

…so I guess the 65W adapter should work.

Best Answer

Ok, actually reading the Wikipedia a second time answered my question:

The USB Power Delivery specification revision 3.0 defines a programmable power supply protocol that allows granular control over VBUS power in 20 mV steps to facilitate constant current or constant voltage charging. Revision 3.0 also adds extended configuration messages, fast role swap, and deprecates the BFSK protocol.

So, apparently the adjustable voltage power supply supports USB power delivery version 3.0 whereas the cheaper power supplies support only older versions of USB power delivery.

I think for future-proofing my purchase, I will select the adjustable voltage power supply. There may be some need for using the PSU with future devices that expect revision 3.0 support.

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