Wireless Charger

Thread Starter

mamakuxa

Joined Oct 5, 2015
5
Hello,

I am currently working on a wireless charger project, where I am to use a 120/24V transformer as a power source to create a wireless charger module for a regular 5V/<1A USB output plug. I have attached my transmitter circuit below. I am using a colpitts oscillator using a pair of 0.1uF caps and a 100uH inductor to produce a 73 kHz frequency. I am also getting a 11.4Vpp output. I have a couple questions if anyone can help.

1) Where would I connect the other end of my transmitter coil? I get a output from the oscillator circuit but I dont know where to connect the other end to.

2) Is 11.4Vpp enough to power my charger at the transmitter side? It is going through a bridge rectifier to a 5V regulator to a female usb plug.

3) Anyone have a suggestion to improve this circuit? I heard a MOSFET would help in place of the BJT but how would taht affect my circuit?

Thank you for the help in advance! I am working solo on this and any help would be appreciated
 

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Thread Starter

mamakuxa

Joined Oct 5, 2015
5
Thank you, @ronv. This helped a lot with the science background of it. I am still curious about what I can fix with my current circuit. I unfortunately, dont have enough time to completely rebuild my circuit right now. I have made some changes using the write up! Thanks!
 

ronv

Joined Nov 12, 2008
3,770
Thank you, @ronv. This helped a lot with the science background of it. I am still curious about what I can fix with my current circuit. I unfortunately, dont have enough time to completely rebuild my circuit right now. I have made some changes using the write up! Thanks!
One of the most important things is that the transmitter resonant frequency be the same as the circuit driving it. So the transmitter needs to be a series resonant circuit at the same frequency as your oscillator. I don't think you can drive it directly with your oscillator.
The bad news is you need to start over. :(
 

Thread Starter

mamakuxa

Joined Oct 5, 2015
5
Can you elaborate of that statement? :/ I am assuming that the components R,L and C must have a special correlation like the "Q" factor. I read into the problem and seem I have a lot of work to do to fix these components. However, would it still be possible, after fixing these components, to drive a wireless transmitter with this "colpitts oscillator"

btw, thank you so much for your continuous help.
 
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