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BQ51050B: BQ51050B stops charging

Andre T
Prodigy 10 points
Part Number: BQ51050B

Hi,

Just wondering if anyone can help a problem I'm having with the BQ51050B wireless charging IC.

The issue is that when the unit is placed onto a charger pad it begins to charge the battery until full (as expected) and then switches off. The problem is that the battery will then start to deplete while on the charger and will not start charging again unless I physically lift the unit off the charging pad and place again. If I don’t lift it off the pad the battery will completely go flat and still will not restart charging.

Just wondering if there is any option I can do with the IC that allows for charging to restart on its own when the battery voltage starts to drop (when left on the charger). A micro controller currently is measuring the battery voltage therefore can use one of its GPIOs if needed.

Thanks for any help or suggestion you may have.

- Andre

  • 0
    TI__Guru* 75906 points

    Hi Andre

    The BQ51050B is sending a charge complete command to the TX and it shuts down.  But the TX is configured to not power up the RX check if it needs to be charged again.  It will check if it has been moved by pinging the RX but this is not enough power for it to turn back on.

    Do you have the option to add external circuits? 

    If the Comm1 / Comm2 caps are pulsed it looks like the RX has been moved and TX may restart.

  • 0 in reply to Bill Johns
    Prodigy 10 points

    Hi Bill,

    Thank you for replying so quickly (and yes the other post is from the same design, sorry that 2 of us posted without realising).

    Looks like I got more information about the matter. Some further research says that the wireless pad (TX) is in control of whether or not the charging starts on its own again. Some chargers check the battery level of the device being charged (RX) every 5 seconds after charge is complete, some check after 15 minutes and some never check again unless removed from the wireless pad and put back on.

    So naturally I got another wireless pad to test on and this wireless pad restarts the charge on its own as the battery voltage goes down.

    is my findings above correct? If so i can simply recommend to our customer to use a charger that automatically restarts on its own as the product will be sold with a wireless charger.

    if this is not an option for our customer then yes we can add additional circuitry to modify the COMM1/COMM2 caps. Would you have a recommendation on this approach?

    Thanks again.

  • +1 in reply to Andre T
    TI__Guru* 75906 points

    Hi Andre

    Your test results with other TX (charging Pads) sounds correct.  All are required to turn off when the receiver sends and End Power Transfer (EPT).  Charge complete is EPT01.  But when the TX tries to restart and power the receiver is not defined and varies from Manufacture to Manufacture.

    An external circuit to consider if needed.  MCU that would drive MOSFETs in parallel with COMM1 and COMM2 pins.  When recharge is needed the MCU could drive the MOSFET with a low freq square wave.  The TX will see this as a different receiver and restart power transfer.