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I have looked at various USB power delivery (PD) adapters that supply a certain number of watts and are powered by 230V mains voltage. Always, they seem to have either a USB-C port or a full USB-C cable permanently connected to the adapter. I have never seen a USB power delivery adapter with USB-A port, so that one could use it with USB-A to USB-C cable.

Does a USB-A connector even have the pins required for negotiating power delivery (PD)? I know it can supply at least 5V voltage, but I'm not interested in that; I'm interested in power delivery standard with much higher voltages.

Wikipedia says a PD aware cable needs to be used. Can a USB-A to USB-C cable even be PD aware? If it can, is it possible in practice to find such PD aware cables in the marketplace?

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From a physical connector rating standpoint, it is possible to use a USB-A port for delivering more than the standard 5V - the quick charger for my phone (HTC brand) does just that. It can provide 5V @ 3A, 9V @1 .7A or 12V @ 1.25A when attached to the phone using a USB-A to USB-C cable.

However, that particular charger is not using USB power-delivery to do so. Instead it uses Qualcomm® Quick Charge 3 (Note 1), which is a proprietary technology that is not officially part of the USB specification. It is not the same as the USB power delivery specification.

There was a power delivery extension to USB 2.0, however that was essentially just allowing USB 2.0 ports to provide a higher current (>2A), but still not exceeding 5V. That was possible based on using resistor values on the data lines to select power delivery current levels.

As far as I'm aware using USB-A connectors to deliver (or select) higher voltages is not possible under the official USB standard, power delivery or otherwise. To do so requires some other proprietary technology that deviates from the standard.


Note 1: Other such proprietary standards exist.

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