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I bought a new laptop, the Xidu Tour Pro. It came with a quite bulky 19V 2.1A power supply that I'd like to replace. One review at a respectable site claims that the computer charges just fine through its USB C port, even though the product has no explicitly stated support for USB PD.

My question to you is how bad things could get if I tried this myself. Of course anything could happen depending on how they designed the circuit, but if we assume that all relevant standards relating to USB-C, but not USB PD, are fulfilled, does this mean that nothing bad happen?

I would assume, or at least hope, that the people behind the standards thought of the possibility of people plugging in USB PD chargers in any USB-C port they encounter, regardless of whether it makes sense or not. If not adults, then it would be a nice game for children...

A. Drott
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  • What connector does original the charger use? - is it a round thing, or USB-C – Jasen Слава Україні Feb 15 '20 at 11:28
  • The original charger comes with a very thin barrel connector, possibly 3.5mm. For sure, this is the recommended way of charging, but I did read a few times in reviews and on StackExchange that some laptops support USB PD charging even though as an undocumented feature. – A. Drott Feb 24 '20 at 20:05
  • a 40W power supply is going to be about the same size whichever plug it has on the cable. are you wanting to replace the power supply with one that is equally bulky? – Jasen Слава Україні Feb 24 '20 at 21:55

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They go through a configuration process,

The USB Type-C receptacle, plug and cable solution incorporates a configuration process to detect a downstream facing port to upstream facing port (Source-to-Sink) connection for VBUS management and host-to-device connected relationship determination.

The USB Type-C port configuration process is used for the following:

  • Source-to-Sink attach/detach detection
  • Plug orientation/cable twist detection
  • Initial power (Source-to-Sink) detection and establishing the data (Host-to- Device) relationship
  • Detect if cable requires VCONN
  • USB Type-C VBUS current detection and usage
  • USB PD communication
  • Discovery and configuration of functional extensions

Two pins on the USB Type-C receptacle, CC1 and CC2, are used for this purpose. Within a standard USB Type-C cable, only a single CC pin position within each plug of the cable is connected through the cable. (p32-33)

So any compliant plug/port combination should negotiate proper voltage and current levels before providing them. If your laptop doesn't agree with the charger it may not do anything. This may not include knockoff chargers. USB PD can provide a higher voltage and thereby charge faster, provide more power, at a lower relative current but it needs to be activated through this communication first.

USB Type-C receptacle to USB legacy adapters are explicitly not defined or allowed. Such adapters would allow many invalid and potentially unsafe cable connections to be constructed by users. (p32)

So adapters could prevent the required communication and cause problems.

Quotes from the Universal Serial Bus Type-C Cable and Connector Specification

jmb2341
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