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BQ51050B: Coil free space inductance's

Christophe Tagneres
Prodigy 10 points
Part Number: BQ51050B

Hello,
i have an issue with the coil free space inductance measurement Ls. I don't really get what it represents and how to proceed for measuring it.
I'm using this coil : WR221230-36M8-G from TDK
The given inductance is the Ls' value at 1Vrms and 100kHz equal to 27.9uH. That leads to C1=93nF. And now i'm stuck with the Ls value for C2.
Best regards

  • 0
    TI__Guru 65716 points
    The coil L value will change due to metal around it. Ls is free space with no metals around the coil while Ls’ is value when the coil is on a TX coil. Ls’ represents inductance during power transfer and is used to tune the Cs capacitor, main power path.

    For WR221230-36M8-G the Ls value is 27.9uH and Ls’ is needs to be determined.

    Ls is used to tune the detection capacitors (Cd). This is used for a moving coil TX that locates the RX uses an X – Y grid to ping the Cd capacitors at 1MHz. See WPC type A2 Transmitter or Panasonic QE-TM101-K wireless charging pad.