Hello,
we have depolyed in the field more than 40.000 bracelt using your BQ51051BYFPR as Qi receiver. The charger was a commercial model, produced by a Chinease manufacturer based on a custom ST CPU based solution (designed by the manufacturer).
All of a sudden the charger manufacturer changed its schematic, claiming that the charger is now "better". Actually it looks better, now the charging solution is based on Injonic chip IP6806.
Unfortunatelt the system (charger + our device) is not working anymore.
The charging process starts, but it quits after few seconds.
If we remove the plastic enclosure of our device, closing the two coils by approax 1mm, the system works, but in the final configuration, with the plastic enclosure as it must be, of course, it doesn't.
Please note that with the previous charger we had a lot of margin with the previous charger, with the new one it doesn't work.
We have analyzed what is going on using the Avid Qi sniffer and it looks that it is a communication problem.
The received sends its packet to regulate the charging frequency, the frequency correctly change and we quickly arrive to the 0% control error phase, with a frequency of around 159Khz.
All of a sudden (in a matter of 1-2 seconds) the quality of the communication link deteriorates and the field is loss.
Looking with the analyzer the packets transmitted we see the while COMM1 its always perfectly shaped, the analyzer gets a COMM2 signal extremely poor, very different from how it should be. This happens just before the field loss signaling.
Immediately after the disconnectio, the first contract is sent again and the procedure starts over. Eventually the battery it is recharged, but we need 10 - 15 hours instead of the usual 2.
As we have seen this difference between COMM1 and COMM2 we have tried to change something on the capacitor connecting COMM2 to the coil (C4 in the schematic below) doubling its value, but nothing changed.
We would like to know your thoughts and advices.
Thanks!
Andrea
