wireless power transfer low efficiency issue

Thread Starter

farzad latifeh

Joined Oct 3, 2017
Hello everyone
There is a free project for wireless power transfer below for charging cell phones I used for my project which is not phone charging, anyway,
I put transmitter image here

As you can see it has used one 555 timer to alternate current via N channel MOSFET IRF540N
Then via L1,C1,C2 it's made Magnetic flux with specific frequency to transfer power wirelessly (around 26 kHz)
Everything here is clear until now, but there are some questions for a dummy like me
1- why do we need a MOSFET driver (BC547 Tr) generally here? actually I cannot get it why not using MOSFET directly from 555 timer like the image below: (what I made is the following image, also L1 and L2 are hand made with ratio around 1:2 to increase Voltage at the receiver point with a ferrite core)

2- what is the reason for using C1,2 to specify transfer frequency?
actually I tried a Potentiometer instead of R3,4 to change 555 frequency then I fond around 82K Ohms for R3 and 12K for R4 (around 1KHz) the current flow reach its Maximum however more than that or less than that the current in the receiver will drop, I cannot figure it out what is happening here about frequency of 555 and L1,2 frequency!!!! and how it affect transfer efficiency in general, on the other hand the frequency of L1 and L2 with distance will vary from 14KHz to 5KHz!!!! what is that even mean? is that because I did not use C1 and 2 ??? higher frequency means less efficiency???

3- any idea how I can increase efficiency of circuit by increasing voltage and or current ??? at this point the 1.2 amps current flows from L1 so it means around 14 Watts but only 137 milliamps (Shorted) I can get from receiver and 160 Volts when the circuit is open, also the voltage drops to 2 Volts just with a simple Red LED.
please kindly correct me, thanks.


Joined Aug 27, 2009