Hi I have recently received some sample BQ51050b wireless power rxr ics. I have built a couple of prototype boards.
I am using a couple of bought in QI compliant power transmitter chargers to test the boards. The boards operate properly in fast charge mode and in current regulation mode. There however seems to be an issue when transiting from the fast charge mode to the taper mode. The power output oscillates and causes the transmitter chargers to beep.
Please see the following screen shots:-
2766.FaultyTransitionFromFastChargeToTaper.tiff
CH1 shows Vrect, CH2 shows VBat
The same is shown on a longer 500ms time base here :-
1780.FaultyTransitionFromFastChargeToTaper_TB500ms.tiff
I also checked the TS/CTRL line :-
5417.TS_CTRL op during FaultyFastChargeToTaper_TB500ms.tiff
The fast charge current is set to around 200mA and was measured as 218mA. The current termination setting is set to approx. 10% and during testing this was 28mA.
So every thing seems to be fine apart from the transition from fast charge to taper mode.
The circuit is shown below
Any advice on what might be the problem, would gratefully be received
Best Regards,
Gareth