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How to choose the resonant frequency for Rx?

Fan Yang22
Intellectual 390 points

Dear TIers:

I am a bit confused about how to choose the resonant frequency for the Rx an Tx? and why we need to do the load-line analysis when we want to design the coil for the receiver side? 

When I read the forum, a lot people just say they set the resonant frequency as 100KHZ, but why in the load line analysis we need to choose different frequency?

Best regards,

Yang Fan

  • 0
    TI__Genius 14890 points
    Yang,

    The WPC specification requires that the resonant frequency be set to 100kHz for both the RX and the TX.
    The load line analysis shows the resulting rectifier voltage based on the frequency and load current. This is important to understand how the coil responds to loads at each frequency. Note that the resonant frequencies on the TX and RX are still set to 100kHz. The operating frequency is changed, not the resonant frequency. Figure 11 that you included in your post shows a good coil. The frequency lines run fairly parallel to each other for the full load. A bad coil will have some overlap between the different frequencies and the rectifier voltage.

    A good system always has higher frequencies for lighter loads and lower frequencies for higher loads with no overlap.

    The resonant frequency (100kHz) is set outside the operating frequency (110kHz to 205kHz) to ensure the relationship between frequency and power level.

    Regards,

    Dick