How the Meizu Pro 7 Plus AC Charger and Cable Applies USB Power Delivery Over USB Type-A with the Xiaomi Mi 6 Phone
The Meizu Pro 7 Plus's own AC charger has a special way of implementing USB Power Delivery based communications over its USB Type-A port using Meizu's proprietary mCharge 4.0 charging scheme. For this to work, the charger needs to connect to the USB Type-A to Type-C cable accessory made specially by Meizu to the phone. While the Meizu charger can deliver over 23W of fast charging to the Meizu Pro 7 Plus, it also offers 10W to charge other non-mCharge enabled mobiles like the Mi 6 by Xiaomi.
Since the Mi 6 supports USB Power Delivery 3.0 as well as Qualcomm Quick Charge 3.0 technology over its USB Type-C connector (that should work on the Qualcomm Quick Charge 4+ platform), the phone should be able to work with the Meizu charger using USB Power Delivery. Here we try connecting the Mi 6 to the charger over the Meizu USB Type-A to Type-C cable and observe the charging activity through the Granite River Labs GRL-USB-PD-A1 test software.
We can see that the Meizu charger initiates USB Power Delivery negotiations by continuously promoting 10 watts (5 volts @ 2 amps) and variable 4.98 to 9.96 watts (3-6 volts @ 1.66 amps) when the Mi 6 is at 2% battery. A hard reset then prompts the charger to again display its source capabilities of the same power profiles.
The Mi 6 then proceeds to request to charge at an initial 10 watts (5 volts @ 2 amps) which the Meizu charger agrees to provide.
The charger is next seen to initiate several Vendor Defined requests of Discover Identity and SVIDs with which the phone also complies.
The power graph shows that the Mi 6 actually gets about 10.9 watts (5.2 volts @ 2.1 amps) of charging from the Meizu charger while the phone is switched on at 2% battery charge.
Upon initial plugin, we can see that the voltage goes to 5.2 volts as the phone starts pulling around 1.8 amps after the first power request. As Vendor Defined Messages are exchanged, the current rapidly drops to near zero but quickly picks up again to settle at about 2.1 amps @ 5.2 volts.
Fortunately, the Mi 6 is able to charge with the Meizu Pro 7 Plus charger at around the max 10 watts offered by the charger using USB Power Delivery, while being connected with the Meizu's supplied USB Type-A to Type-C cable. While 10W is lower the maximum 18W offered by the phone's original Qualcomm Quick Charge 3.0 charger, the Meizu charger can still act as a replacement power supply for the Mi 6 when the Xiaomi charger happens to be unavailable. However make sure to use the Meizu USB Type-A to Type-C cable along with the Meizu charger to enable USB Power Delivery charging over USB Type-A.