Placement of wireless receiver charging coil

Dinesh,

A good wireless power RX coil will have a shield that captures the magnetic field from the TX. This opens up the area directly behind the coil for the full RX solution.

There are several good suppliers for RX coils.  I suggest you look at table 7 in the bq51013B datasheet for a list of vendors that we have evaluated.  This is not an exhaustive list, there are other good coil manufacturers.

Searching through their web pages will show you their products including size of the coils including the thickness.  They will all ship with the coil + shield and the datasheets will include the shield thickness.

Regards,

Dick

Dear Dick,

Thank you for your soonest feedback!!!

1)Can we place the passive or active components near to wireless coil? if yes how much will be the min clearance between them.?

Because I have placed some LDO and Wireless receiver circuitry near to wireless RX coil ,so I would like to know about PCB layout guidelines

2)Need to have detailed design requirements for wireless Charging coil.

- What could be the plastic thickness in that region ?
- Any plastic material constraint ?
- What would be allowable air gap ? Is there any such consideration ?
- What would be maximum temperature coil can attain ?

Looking forward for your positive response!!!

Thanks and Warm regards

Dinesh Katkar

Dinesh,

1) The bq51003 has some layout recommendations.  The discussion does not review the relationship between the wireless coil and the circuitry.  Use the shield of the coil to protect as much of the circuitry as possible (in particular, metal objects that may interfere with the magnetic field). The FOD calibration can be used to help account for some friendly metals near the coil.  

2) The WPC specification is for the total distance from TX coil to RX coil of 5mm.  That space is usually filled with the transmitter casing (in general plastic) and the receiver casing (generally plastic or glass).  The only constraints would be on material that would interfere with the magnetic field used for power transfer.

If your coil temperature is how hot will a coil get, that is based on the DCR of the coil.  The power drop across the coil will heat the it.  Getting a low DCR coil helps reduce the heat.  A good coil will some heating, but not much.

The WPC has specifications on how hot the surface of the product can get, but does not specifically address the coil temperature.

Regards,

Dick

Dear Dick,

Thank you for your soonest feedback!!!

I would like to know about FOD calibration means what? I think wireless coils have shield around it by structure ,so no need to put shield again around the wireless RX coil.

Distance from TX coil to RX coil of 5mm is ok ,but we need the mechanical constraints like if we are going for product design and molding of parts ,then for molding temperature can wireless RX coil sustain.

Thanks

Dinesh Katkar

Dinesh,

Go to ti.com/wirelesspower.  There is a very good overview of a topics.  For FOD, go to the "Getting started" tab and go to the Foreign Object Detection section in the table of contents.  Additional information can be found on the bq51003 web folder under the "Tools & software" tab.  At that tab is a GUI on FOD calibration, which contains a detailed User Guide.  Finally, at the "Support & training" tab, there are videos on FOD and other topics.

The coil around the shield is generally enough protection.  The FOD calibration allows you to account for "friendly metals" in your system.

The temperature of the wireless coil for production building needs to come from the coil vendor.

Regards,

Dick