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Can't get more than 700-800 mA battery charge current

Ernst Ditges
Prodigy 10 points
Other Parts Discussed in Thread: BQ51050B

Hi, 

in our new product we're using the BQ51050B receiver to charge a 6Ah LiPo battery. The Qi transmitter is a OEM off the shelf product .

Our aim is to get the maximum 1.5A charge current, but we don't manage to get more than 700-800 mA.

RILIM = 210R (R1=10R, RFOD=200R).

RTERM=2.4k

TS/CTRL pulled to GND via 10k resistor to disable TS function.

Signals VRECT and TS/CTRL look like expected.

Any idea what might be my issue?

Thanks in advance

Ernst

  • 0
    TI__Genius 14890 points

    Ernst,

    Please verify the power delivery specification for the Qi transmitter.  I have seen some that do limit the power earlier than expected.

    There are a few things to look at to get some background.

    The RX coil is key to the power transfer.  Are the Cs and Cd capacitance values set correctly for the coil?  Is there excessive heating on the coil or on the Cs capacitors?

    What is the frequency at AC1?  The Qi system operates between 110kHz and 205kHz.  If the AC1 frequency measures 110kHz, then the transmitter is sending all th power it can.  Can you determine the efficiency during your testing?  The peak to peak signal levels on AC1 is also of interest.

    What is the battery voltage during your testing?  

    Did you look at FOD calibration to determine the value of Ros (RECT to FOD resistance)?

    Regards,

    Dick