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How to detect receiver with a wireless charger transmitter?

vforvoila

Oct 8, 2022
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Oct 8, 2022
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My end goal is to build a circuit with a wireless charger transmitter module and a led indicator that turns on when the receiver is detected and wireless charging is occurring.

I’ve been reading about the analog pings the TX uses to detect RX, Foreign Object Detection (FOD), Q-factor measurement… But I feel I’m nowhere nearer to the actual circuit that can implement this. I have a wireless charger that I opened out of curiosity. Its base lights up blue when plugged in and red if an object is charging on top of it. So basically, exactly the functionality I would like to replicate. I could clearly see a micro-controller in the PCB, and that’s where my reverse-engineering skills stopped! :’)
I couldn't find online a circuit of a transmitter with a micro-controller that measures loss in Q-factor or FOD so any tips or resources on how I can achieve this are highly appreciable!
 

kellys_eye

Jun 25, 2010
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Google for Wireless Charger Control IC and you'll find loads (at the likes of Mouser etc) where their datasheets are filled with information on how those devices work. Developing your own outside an already-available integrated solution is a fruitless exercise so relying on various manufacturers (who also publish application notes on how to use them) is the usual way forward.
 

Harald Kapp

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Nov 17, 2011
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You can simply measure the power consumption of the high-frequency drive circuit.
Without a load to charge, power consumption is very low.
With a load atop the charger, power is transferred from the charger to the load and power consumption of the high-frequency driver circuit increases proportionally to the power transferred to the load.
 
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