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BQ51050B: Abnormal termination of charging process

LiJia Pei
Prodigy 40 points
Part Number: BQ51050B
Other Parts Discussed in Thread: BQ500212A

Currently, I use BQ51050B as the receiver for wireless charging, but now I have a problem that I cannot solve.Each charging process will be interrupted, and the transmitter failure indicator lights up, and can not be restored. According to RLIM, the charging current is set to about 1A.

My battery capacity is 1800 mah, Everything was fine when you started charging, When the battery voltage rises to about 3.7V, current 800 ma, Transmitter Failure Light on, and has no automatic recovery,The coil can only be removed from the transmitter and placed again on the transmitter to continue charging to 4.2V (or occasionally stop charging).I don't know what reason is this, below is the failure, VRECT voltage (yellow).At present, the coil I use is TDK wr483265-15f5-g 13.3uH. The transmitter is samsung ep-pn920. I really hope to get help.

Normal charging （VRECT）

abnormal VRECT

Total stop VRECT

What is the cause of this?

Please help me find out the problem as soon as possible.

thanks

  • 0
    TI__Guru* 75806 points
    Hi
    A couple of things to try:
    1.) The stop charging with TX turning off could be FOD fault (Remove RX to reset). Try Removing R35, Increase R-FOD and decrease R-ILIM. This should result in RX reporting more received power and giving better FOD results.
    2.) To get started testing a better TX to use is the TYLT VU Solo, Amazon has them for $10. It is based on the BQ500212A. It behavior is better understood which help troubleshooting.
    3.) Coil and tuning are OK. What is your coil to coil distance?
  • 0 in reply to Bill Johns
    Prodigy 40 points
    HI,Thank you for your reply,

    1.)I have tried according to your description, changing R38 to 10 and increasing R39 to 300. I found that there was no effect and the charging process would still stop suddenly.Do I need to keep increasing the value of R39?Please give us your suggestion again.
    2.)The buying cycle is too long in my area.
    3.)The current coil distance is 4mm, because I have tried many times without any effect, so please give me the specific tuning parameters.

    thanks.
  • 0 in reply to LiJia Pei
    TI__Guru* 75806 points
    Hi
    1.) Do I need to keep increasing the value of R39? -- Higher value of R39 would not hurt, OK to try.
    2.) The current coil distance is 4mm -- Bill J - OK, so please give me the specific tuning parameters.-- Bill J - The coil tuning looks OK, 13.3uH with 68nF/68nF/47nF is close.

    In the scope capture "Total stop VRECT" -- Is this typically what you see during fault?
    It looks like the RX sends a packet then the TX turns off.
  • 0 in reply to Bill Johns
    Prodigy 40 points
    HI

    1)Because the first half of the charging process is not abnormal, I think it should not be a problem of tuning parameters,
    If the tuning parameters are not correct, it may cause the coil to not work at all. The phenomenon observed at present is that it can work steadily. I think the correct alignment of coils will be much more useful. Is my understanding correct?

    2)"In the scope capture "Total stop VRECT" -- Is this typically what you see during fault?"
    Yes,This is the voltage value of VRECT before each charge stops,And every time before charging stops, VRECT traffic can suddenly increase.
    I suspect it may be an EPT from FOD anomaly,
    Can I disable RFOD by setting it? How do you do it?
    Or what kind of problem do you think it is?

    3)Increasing R39 will significantly reduce the charging current, but I will try to increase it for verification.

    Please provide some more suggestions,
    thanks.
  • 0 in reply to LiJia Pei
    TI__Guru* 75806 points
    Hi
    2)"In the scope capture "Total stop VRECT" -- Is this typically what you see during fault?"
    Yes,This is the voltage value of VRECT before each charge stops,And every time before charging stops, VRECT traffic can suddenly increase.
    I suspect it may be an EPT from FOD anomaly, --- Bill J -- No FOD EPT.

    Can I disable RFOD by setting it? -- Bill J - I know how to do this on the TI TX, not the one you are using.

    How do you do it? --- Bill J - The TX will make the FOD fault decision. All the RX does is report how much power it has received. This is set up with the FOD resistor that is a sample of output current that is a proxy for received power. Larger R-FOD higher the received power and less chance of an FOD issue.

    Or what kind of problem do you think it is? Bill J - It is hard to say, all the common problem have been ruled out. If the RX is heating up it will send a thermal fault (EPT) and turn TX off. That is something to check.
  • 0 in reply to Bill Johns
    TI__Guru* 75806 points
    Hi
    Any update on this problem?
  • 0 in reply to Bill Johns
    TI__Guru* 75806 points
    Hi
    We have not received a reply and I am closing this thread.