USB C Power Delivery using below schematic?

Question

I have limited experience with USB C and I want to design a board which needs to charge both a smartphone and another subsystem which draws around 1W. I have read that by just connecting a 5.1k resistor to each CC pin of the USB C female receptacle for the power in I can "trick" the wall adapter to give me up to 15W, without using any other specialised USB Type C PD integrated circuit. Also, would the phone (which needs to connect to the "USB C TO PHONE" female USB Type C receptacle) be charged with, let's say, 14W with only the VDD and GND pins connected to its receptacle?

Also, the rest of both receptacle's pins should be left floating, right?

I'd like to mention that I need to use this configuration, with only one USB Type C for power input and the phone charged via the board.

Answer 1

No, this might potentially damage your systems, and not work even if they are protected against that damage:

The phone will want to negotiate the voltage itself, and you can't simply add another load to the USB cable. I mean, you could try, but then you really need to omit the resistors, and your secondary load needs to deal with whatever the phone negotiates - quite likely something higher than 5V, if it charges with more than 10W.

You could build a USB hub that allows for USB PD to be forwarded to the phone's port. These exist, they're commonly found in USB docking stations. But they need logic and potentially step-down conversion! Not a trivial task you'd design in an afternoon, even if you were familiar with all the tools.

Answer 2

First of all, if there is no Power Delivery communication, there is no Power Delivery levels of power available.

The system you have drawn is a DFP anf it does indicate to the UFP that it is a DFP device that requires power. However, it does not have any mechanism to detect where it is connected and how much current is available from source.

So you can't draw 3A/15W, and you can't draw 1.5A/7.5W either. And if your device is connected to a PC through a unpowered hub with a few devices, your device cannot even draw the maximum amount of 900mA for USB 3 device as it has no way of negotiating how much it needs and if it is even connected to a USB 2 port where it can only request 500mA max. And it is possible there is nothing available any more.

So, the phone cannot negotiate higher current through any means, and negotiating higher voltages would require data connection for enumeration, Battery Charging port detection, or some other Fast Charge protocol, or PD signaling from the phone to source.

The phone has been just connected with power but no signaling how much current it can take. The phone might not even detect a cable being connected so it might not see a charger even if you give the phone 5V.