• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 602 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Loosely coupled coils

Sasa Milovanovic74
Prodigy 170 points
Other Parts Discussed in Thread: TIDA-00762, BQ51013B, BQ51050B

Hi!

Wireless charging has giving me troubles lately. For my device I need to find solution for wireless charging of small LiIon battery. Supply/charging voltage is 5V and charging current is max 500mA.

Problem is in Rx coil. It has to be small to fit the device. Square coils can be up to 15x20mm, and round coils up to 10mm OD. Charging distance must be 5mm or more (there is 2mm wall thickness for charger, and another 2-3mm wall thickness of the device itself). Tx coil can be of any size as the dimensions of the charging station is not critical.

I have contacted various Asian companies that sell various Rx/Tx coils, but none seems to have an answer to my problem. I'm guessing because they are mostly re-sellers.

If anyone can appoint me in the right direction how to begin to solve this problem, I would greatly appreciate.

Creating my own pcb is also one of the possibility, but I would prefer standard solution.

Thank you in advance!

Best regards,

Sasa

  • 0
    TI__Genius 14890 points
    Sasa,

    I'm not sure of exactly you are asking. I will give some overview on coils.

    A small RX coil (10mm diameter) is very difficult to couple to. A 15x20mm coil would still be difficult, but should be achievable.
    If your system does not need to be Qi-compliant, than a smaller TX coil would help (closer to the RX coil size).
    TI devices are based on the Qi standards. Standard Qi coil-coil spacing is 5mm which is what you have noted so there should be no issues there.

    There are some TI reference designs that might help.
    Look at: TIDA-00762, TIDA-00415 and TIDA-00334 for transmitter solutions with non-Qi coils.
    Look at the bq51050B for an integrated charger solution. You would need to discuss coil options with the coil manufacturers. See the bq51013B datasheet (Table 7) for a list of manufacturers we have dealt with successfully. The table shows specific coils for 5W with Qi transmitters. Each manufacturer does have other options. See application note slua649g (bqTESLA Transmitter Coil Vendors) for direct contact information.

    Regards,

    Dick
  • 0 in reply to Dick Stacey
    Prodigy 170 points

    Dear Dick,


    Thank you for reply. I am not bound by Qi; it can be, but it's not requirement.

    I will look into reference designs you have mentioned.

    Thank you again!

    Best regards,

    Sasa