GTrusted
The Plugable USB-C 3-Port Hub with Pass-Through Charging enables pass-through charging from other chargers supporting the USB Power Delivery to a computer or phone. Let's see what happens when it is used with the Belkin USB-C Car Charger + Cable to charge the Microsoft Lumia 950.
Using the software from Granite River Labs, first we look at the USB Power Delivery negotiation between the Belkin USB-C Car Charger + Cable and the Plugable USB-C 3-Port Hub.
We find that the Belkin Charger provides the following power profiles:15 watts (5 volts @ 3 amps) and 27 watts (9 volts @ 3 amps) to the Plugable USB-C Hub.
The Plugable USB-C Hub initially requests 5 volts @ 3 amps from the Belkin Charger.
The Belkin Charger provides this power but the Plugable USB-C Hub again requests 5 volts @ 3 amps from the charger which then again complies.
If we look at the transactions between the Plugable USB-C 3-Port Hub and the Microsoft Lumia 950, we first see their consumer roles.
The Plugable USB-C 3-Port Hub then indicates the supported power profiles that pass through from the Belkin USB-C Car Charger + Cable. Note that the currents are lower than what the Belkin Charger provides to the Plugable USB-C Hub (which is reduced by 12.5 watts for the 5 volt rail, and 5 watts for the other rail due to the power consumed by the hub or provided to the Type-A ports downstream of the hub).
The Microsoft Lumia 950 only requests 5 volts @ .5 amps from the Plugable USB-C 3-Port Hub.
You can see how the Microsoft Lumia 950 (UFP Sink) communicates with the Plugable USB-C 3-Port Hub (DFP Source). Once the Data role swap happens, the Microsoft Lumia 950 which acts as a DFP Sink sends the VDM (Vendor Defined Message) messages to the Plugable USB-C 3-Port Hub. Below also shows that the Microsoft Lumia 950 supports the DP Alt mode via VDM messages.
The Microsoft Lumia 950 also declares its own power capabilities at the very end.
By supporting USB Power Delivery, the Plugable USB-C 3-Port Hub is able to successfully pass through a complex USB Power Delivery negotiation sequence and can intelligently pass-through power from the Belkin USB-C Car Charger to the Microsoft Lumia 950.
Meanwhile other hubs like the Marsboy 2 USB 3.0 Type-C Charging Hub does not support USB Power Delivery which makes it challenging to work with external USB Power Delivery-based chargers.
