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BQ51013B audio noise and current ripple

Victorien v
Intellectual 520 points
Other Parts Discussed in Thread: BQ51013B

Hi,

I'm testing a wireless power RX module based on BQ51013B and I see some dysfunctions :

- I heard a noise like this : .

- I have a current ripple onthe power supply of Tx Module. For exemple, the current is 0,57A and each 1.5 / 2 seconds, the current inscrease to 0,62A.

Then I have some questions :

- How can I test if coil is well tune ?

- Is it only the ceramic capacitor which generate the sound ?

- I see this signal on RECT pin on BQ51013B, is it correct ?

Thanks

  • 0
    TI__Genius 14890 points

    Victorien,

    Using the overall efficiency of the TX DC input to the RX DC output is the best way to evaluate the coil tuning.  Calculate and install the optimum Cs capacitance and measure the efficiency across your expected load range.  Details of the Cs capacitors is based on the inductance of the coil and can be found in the datasheet.

    Key to this is to measure the efficiency in the expected positioning of the end product (matching TX and RX as expected).  The next step would be to change the capacitance by +10% and measure the efficiency again.  Repeat at -10% and you will have a good idea of your optimized capacitance.

    The ceramic capacitors on the TX are the generators of the audible noise.

    The figure you attached showing the "pulses" on the RECT pin are expected.  These are an indication of the communication from the RX to the TX.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Intellectual 520 points
    Thanks for this answer.
    And about the current ripple, that I see, is it normal ?
  • 0 in reply to Victorien v
    TI__Genius 14890 points

    Victorien,

    I did not see any current ripple on the included plot.  However, depending on many factors, the communication impact shown on the RECT pin can be seen on the OUT pin and therefore the output current.

    Regards,

    Dick