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long distance between coils?

Ling Wang
Prodigy 20 points
Other Parts Discussed in Thread: BQ500110, BQ500210, BQ51013, BQ51051B

Is it possible to bypass the WPC standard in any design with bq series?

I also find the 5 mm limit is very annoying in most applications. I would like to have it transfer energy in 20-40mm range @ 1%-10% efficiency (10-50mA). From the file attached to this forum it seems physically possible. However, you said the WPC prevents this. Then is it possible to bypass the communication controlling the power output. For our design the energy efficiency is the least concern.

Thanks

Ling

  • 0
    TI__Guru* 75656 points

    Hi Ling

    The WPC standard can be bypassed if your design is NOT WPC certified and is considered a proprietary design.  In this design your RX will only be used with your TX.

    At a current level of 10-50mA and low efficiency increased distance may be possible.

    The bq500110 (bq500210 may be better) and bq51013 require communications to operate correctly and establish power transfer.

    The first problem that you will encounter is TX having difficulty detecting the RX.  Load placed on the TX coil by RX coil may not be enough for the analog ping to detect the RX.  This is a short pulse the TX sends out every 400mS.  But the TX also sends out a digital ping every 15 sec, which is a long pulse, intended to power up the RX and allows it to respond.  The digital ping has the greatest chance of detecting an RX a long distances. But time for the TX to detect the RX will be longer.

    A larger RX coil will also perform better, you could start testing with the standard bq51013EVM-725 coil, which is 40mm X 30mm.

    Standard EVMs could be used to evaluate the performance with your application.

    Best Regards

    Bill

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Dear Bill,

    Thanks for your quick response. Is it possible to let the power transmission always ON without detect anything? If it is possible, that will be the easiest way to solve this problem.

    Thanks a lot,

    Ling

  • 0 in reply to Ling Wang
    TI__Guru* 75656 points

    Hi Ling

    No-This is not possible. 

    The transmitter will have to identify a valid receiver is present before power transfer will start. 

    During power transfer the transmitter must receive information from the receiver. 

     The transmitter will turn off after 1.5sec if it does not receive info from the receiver.

    Bill

  • 0 in reply to Bill Johns
    Prodigy 30 points

    Hello,

    I am also in need of a high range wireless charger using bq51051b IC. I want to increase the range to 2cm - 5cm , size is not a constraint in Tx but should be <= 6cm in Rx.  So from Qi Specifications of good efficiency, I tried to calculate the diameter of Tx & Rx Coils and I found if I will use 20cm Diameter coil in Tx and 6cm Diameter coil in Rx it can give 2cm range if Q is 100. I got it theoretically but do you think that it can work or any other way to increase the range to  5cm.

     How to calculate energy efficiency any formula or can test only after making it? . 

    What are the materials from which I can make the cover which will be in contact of both coils?

    Thanks

    Kunal

  • 0 in reply to Kunal Gupta
    TI__Guru* 75656 points

    The bqTESLA products that we support are designed to meet the WPC distance requirement of 5mm.

    To go to 200mm or 500mm may be possible but this is not and application TI will endorse or support.