# How does wireless charging works?

Discussion in 'Electronic Design' started by [email protected], Jun 2, 2013.

1. ### Guest

Hello there,

I live in India, currently studying electronics..

I would love to learn and create on of wireless charges for mobile phone like Nexus and samsung.

May anybody please tell me guide , basic info and instruction to pursue my journey?

2. ### JamieGuest

School projects must be in again.

http://en.wikipedia.org/wiki/Helmholtz_coil

Jamie

3. ### PercivalGuest

It's basically transformer technology with the primary winding in the
charger and the secondary winding (and rectifiers and other conditioning
circuitry) in the device being charged.

Transformers can be better than 99% efficient but that assumes very
close coupling between primary and secondary, so most "wireless" systems
use "tricks" like running at high frequency and making both windings
resonant at that frequency to cut losses.

This is (unusually for Wikipedia) a pretty good overview of the topic:

http://en.wikipedia.org/wiki/Inductive_charging

I always recommend taking what Wikipedia says with a grain of salt,
and checking the listed references and external links at the end for
more in-depth information.

Mark L. Fergerson

Induction.

5. ### Robert MacyGuest

select operating frequency on the highest [within practical limits,
skin effect will eat you alive] allowed by regulatory agency, probably
9.999kHz, but you may be able to go up as high as near 150kHz..

For the Tx, think 'make a field' related to diameter AND current.
Sometimes tuning the Tx makes high current easier, too.
For the Rx, think intercept as much field as possible and 'high Q
tuned to resonate' related to accessible energy 'tapping' that energy,
when I say high Q, I mean at least 150, probably more than 200. If you
can get 400-600, celebrate!

You'll find that large diameter, closely coupled coils work the best.
Foget using any metal - no advantage and usually gets in the way.

Remember magnetic fields are a bit like sound in that once created
they are difficult to get rid of. They penetrate, reflect, and bounce
everywhere. But there in lies an advantage too. The penetrate means
the Rx coil can be hidden. Reflect means the energy is around
somewhere.

For receiver regulation think in terms of LOW impedance, not HIGH
impedance. So to shut off the spigot of power coming in, you SHORT the
input, do not OPEN the input like you do with a voltage power supply.
For example, if you want to lower power coming in from the Rx coil,
place an impedance across the coil, de-Q'ing the receiver and you'll
get less power. Short the coil completely and in a loosely coupled
transformer system; you'll get almost NO power. If in trying to lower
power you instead try opening up the receiver system, you'll find some
excitingly HIGH voltages! The concepts are reversed of what we're use
to, so simply turn your thinking 'inside out'.

To optimize components and structures, use femm 4.2, octave, and
LTspice [all free software tools] Don't know how to use each? join
their groups, they are VERY helpful.

There are more 'tricks' but you'll learn those as you proceed.

When you're done, share what you learned and ship one to Jim Thompson
for his phone and I'll consider my 'consulting fee' paid..