Posted by : AVINASH CHAKRAVARTHI Sunday, 17 March 2013

Its no more science came into exist...we need to know how it rules our future & how it works????
million of answers available in internet for the question " how it works?"..
thousands of videos on YouTube demonstrates the  wireless charging..
yet.....there is a question" how it actually works ?"
here we go...i will promise u ." u will learn at least 5 % on  how it works and u will make u r own wireless charger for u r gadgets .."

1.what is wireless charging?


      2. how it works?

     Wireless charging, also known as inductive charging, is based on a few simple principles. The technology     requires two coils: a transmitter and a receiver. An alternating current is passed through the transmitter coil, generating a magnetic field. This in turn induces a voltage in the receiver coil; this can be used to power a mobile device or charge a battery.
    •     explanation with block diagram

             both transmitter (TX) and receiver (Rx) coils are made up of copper coil.
             rectifier is used to convert the ac signal to dc signals.

    3basic principle and it's efficiency  factors:-

        As i already told u ,the principle is mutual induction between the TX and receiver coil
        let the induction of TX coil is L1  ,
                   inductance of RX coil is Rx,
                  distance between the coils are Z,
                  diameter of TX and RX coil be D1 and D2.
    •   the efficiency of the wireless power transmission depends on the  1, coupling factor
                                                                                                                                 2, quality factor
     The coupling is determined by the distance between the inductors (z) and the relative size (D2 /D1). The coupling is further determined by the shape of the coils and the angle between them 
    • The efficiency drops dramatically at larger distance (z/D > 1) or at a large size difference of the coil (D2/D1 < 0.3)
    • A high efficiency (>90%) can be achieved at close distance (z/D < 0.1) and for coils of similar size (D2/D = 0.5..1)

    The ratio of the inductance L to the resistance R of a coil remains constant for different winding arrangements in the same volume and shape. It makes sense to define this value as a figure of merit to distinguish different coil structures. The quality factor Q is defined by this ratio.The voltage, which is induced by the same current in an inductor scales with the frequency f and thus the apparent power in the device.

    The general definition of the quality factor is based on the ratio of apparent power to the power losses in a device

    Remember quality factor is not under our control it is designed by the manufacturer  
     the value of quality factor will be 0 to infinity,For mass production you may expect values around 100

    4. calculation for getting max efficiency:-

    The power losses while transmission can be expressed as loss factor

    which is the sum of all losses related to the transferred power. A deeper analysis results in an minimum loss factor, which can be achieved by a given wireless power system, if it is proper matched to load and generator:

    Which can be reduced to:

    The equation is only dependent on the two basic parameters of the wireless power system: The coupling factor k between the receiver and transmitter coil and the system quality factor Q. The system quality factor is the geometrical average of the transmitter’s and receiver’s quality factors.

    • This means, that the system quality factor and the coupling factor determine the performance in an equivalent way. A worse coupling can be linearly compensated by a better quality factor and vice versa.

    BLAH BLAH BLAH......... there is no end to learning , it goes stop it ..just apply the knowledge what u have learned so far....

    5.circuit diagram:- 


     in the first section, ac 220v and 50 Hz is converted in to 12v and 40 kHz .u can also use frequency generator (usually available in all electrical labs) to achieve this purpose. 

    these transmitter coils is resonated with the receiver coil  where these ac current is converted into dc current by using bridge rectifiers and filter capacitors , to run  the dc load (here i used a dc fan (5v)) wireless better than wired????

    please give u r feed back...

    { 3 comments... read them below or Comment }

    1. The article that you shared was very helpful and especially it was quite understandable. But I didn't really understand how you use the transmitter and receiver, okay, let's say the receiver is the mobile operator, and what about transmitter, how do you get to use that? Could you elaborate on that part, please?

    2. I've another idea regarding this. I may not be the first one to think this way after reading this article but I guess we could integrate wireless charging into WiFi standards. I don't know if this is within our reach, but with more powerful, higher frequency bands in routers, we could create something that provides you with internet and power at the same time. What do you say?

    3. both transmitter and receiver coils are copper coils but they differ in there values of induction (receiver with less induction value compare to transmitter).As i have mentioned in efficiency factors (diameter of the receiver coil/transmitter coil )< 0.3, in order to get max efficiency .

      transmitter will be connected to ac current, as we know dc current will results in 0 resistance (zl=wl ; in dc w=0 so zl=0; w is frequency ,l is induction coil,zl is impedance of coil)

      as u know receiver is connected to the battery of the mobile with some filter capacitors to reduce the fluctuations in current and some bridge rectifier to convert it in to dc ,as mobile is dc load.

      I'll reply to your second comment soon!!please fell free to ask any questions.


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