QI at small currents 10mA

Hi,

I have device that needs only 10mA charging current. It working with stndard receiver coil. Question is can coil be much smaller with dimension and thickness because I do not need big currents?

This is useful as my device is very small to.

Thanks

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0 dougw over 10 years ago

Hi Miroslav,
The simple answer is yes, you can design a coil smaller than normal dimensions to work with Qi standard.
You can use the following articles to get some idea of how to design a coil for your requirements:
http://www.how2power.com/newsletters/1107/articles/H2PToday1107_design_TI_Sengupta&Johns.pdf
http://www.ti.com/lit/an/slyt479/slyt479.pdf
If you use reasonable assumptions you may also be able to find an adequate solution by trial and error, especially if you have the ability to measure to coil output. I have used a simple square spiral trace on a PCB with tuning capacitor to get useful results. Of course you will also need a Qi chip to perform communications and control.
Doug
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0 dougw over 10 years ago

Hi Miroslav,
The simple answer is yes, you can design a coil smaller than normal dimensions to work with Qi standard.
You can use the following articles to get some idea of how to design a coil for your requirements:
http://www.how2power.com/newsletters/1107/articles/H2PToday1107_design_TI_Sengupta&Johns.pdf
http://www.ti.com/lit/an/slyt479/slyt479.pdf
If you use reasonable assumptions you may also be able to find an adequate solution by trial and error, especially if you have the ability to measure to coil output. I have used a simple square spiral trace on a PCB with tuning capacitor to get useful results. Of course you will also need a Qi chip to perform communications and control.
Doug
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