GTrusted
An advantage of using USB Type-C docks like the Plugable USB-C Docking Station is they use USB Power Delivery to quickly charge certain notebook computers like the recent Windows based Microsoft Surface Book 2.
Using Granite River Labs GRL-USB-PD-A1 power analyzer, we are able to see how the Plugable USB-C Docking Station negotiates over USB Power Delivery to charge the Microsoft Surface Book 2 from a 30% full battery when directly connected using a compliant USB Type-C to Type-C cable.
We first observe Vendor Defined Messages initially happen to adjust voltage and current before the Plugable USB-C Docking Station with Power Delivery begins USB Power Delivery communications by declaring to support only one 15 watts (5 volts @ 3 amps) power profile.
Initially, the Microsoft Surface Book 2 doesn’t seem to agree with this single 15W offering to instead request 0 watts (5 volts @ 0 amps) which is still accepted by the Plugable charger.
We then see a Power Role Swap and soft reset happening to again adjust voltage and current over Vendor Defined Messages, after which the Plugable USB-C Docking Station gets to advertise its full power range of 15 watts (3 amps @ 5 volts), 36 watts (3 amps @ 12 volts), and 60 watts (3 amps @ 20 volts).
The Microsoft Surface Book 2 then goes ahead to make a 39 watts (20 volts @ 1.95 amps) power deal with Plugable and gets approved.
The power delivery protocol negotiation can next be seen to cycle through the same voltage and current adjustment followed by multiple strings of Vendor Defined Messages that also indicate the DP Alt Mode being supported by the charger and PC.
Here we can actually confirm that the Microsoft Surface Book 2 starts pulling current only later in the above power delivery negotiation when it starts to exchange Vendor Defined Messages with the Plugable charger.
Upon initial plugin, we can see the Microsoft Surface Book 2 charges with the Plugable USB-C Docking Station by drawing around a stable 37.8 watts (19.9 volts @ 1.9 amps) power, while the PC is 30% charged and powered on.
The Plugable USB-C Docking Station with Power Delivery uses USB Power Delivery well to be able to quickly charge the Microsoft Surface Book 2 over USB Type-C as expected of the PC’s own performance using the Microsoft’s original Surface power adapter.
