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wireless charger distance

yo kay
Prodigy 85 points
Other Parts Discussed in Thread: BQ51003

 I use the EVM board to test. When the  distance between RX-COIL and TX-COIL is about 1.5mm or little than 2mm, it can not charge. Even when I close the FOD function.

The EVM board is BQ500212A-EVM.But the receiver is our product. The RX coil is TDK's  WR221230-36M8-G, and the TX coil is custom-made(φ30.0).The tx coil is bigger than rx coil. And the rx coil is rectangle.

  • 0
    TI__Genius 12485 points

    Hi Yo,

    Do you see any voltage induced on the receiver coil when you describe no charge? 

    Did you try an off-shelf Qi transmitter? What receiver chip are you using?

    Regards,

    Gautham Ramachandran

    Apps. Engineer- EMT.

  • 0 in reply to Gautham
    Prodigy 85 points

    Gautham

    Thanks for your reply.

    (1)No charge means no current, no voltage on the output.

    (2)I used BQ51003 as the receiver chip. But my coil is custom-made.The tx coil is circle, and the rx coil is rectangle.

     

    Hi Gautham.

    I got a reason. I found the Vrect was 15V above the Vrect-ovp. So BQ51003 protected. So how to solve this satuation?

  • 0 in reply to yo kay
    TI__Genius 12485 points
    Yo,

    Could you please get me scope captures of VRECT, VOUT and the RX coil AC lines?

    Regards,
    Gautham
  • 0 in reply to Gautham
    Prodigy 85 points

    Gautham

    Hi.

    The Vrect is normal when I descrease the Vin to 4.5V . But the input is USB-power. So Vin will not be 4.5V in practice.

    If increase the distance, the Vrect is also normal, but the efficiency will decrease.

    I think the strengh of magnetic field is so big that the Vrect over-voltage.

    So is there any way to decrease the strength, or decrease the current in the coil, or the voltage ?