Author Topic: How is shielding done on wireless charging products?  (Read 246 times)

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Offline MrOmnos

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How is shielding done on wireless charging products?
« on: April 06, 2020, 06:17:34 pm »
Hi folks, I was thinking of implementing wireless charging in one of my projects using QI standard. I was going through WPC specification on wireless charging and where they mentioned shielding but don't really much about its done. I have a device that requires regular charging I don't have space for conventional connectors on it and decided wireless charging was the way to go. Initially I thought I was going to design a PCB which receive coil on one side of PCB and QI charging circuit on the other side of PCB using one of TIs QI chips. But now I am wondering if I do so, wouldn't the traces on on the other side and other non charging circuit and traces will have eddy current induced in them and heat them out. This could possibly set fire to my device. How do smartphones and smart watches and other devices get around this problem?
 

Offline MrOmnos

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Offline jmelson

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Re: How is shielding done on wireless charging products?
« Reply #2 on: April 07, 2020, 02:06:19 am »
How is shielding done on wireless charging products?
Well, the last one I looked at, it WASN'T!  And, an AM radio anywhere in the room was totally blanked out.  An FM radio was clearly interfered with when close to the charger.  This was on something that a guy was going to have manufactured for use by the police.  I told him if it blanked out the radios at the police station, they were not going to be real happy (not to mention the FCC).

Jon
 

Offline Marco

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Re: How is shielding done on wireless charging products?
« Reply #3 on: April 07, 2020, 11:07:24 am »
Assuming for a moment it's being driven by a decent sinusoidal signal without too much harmonics it's almost purely a magnetic field, the coil is too small to be an efficient antenna. The magnetic field will induce bugger all in a trace. As for eddy currents losses in bigger pieces of metal like the ground plane or casing, just cost of doing business.

They do kW charging of cars, it doesn't burn the paint off.
 


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