Wireless power transfer choosing of mosfets
Any help would be appreciated


The most significant recommendation I can give is to simulate the set up. This starts fairly easily with a transmit coil driven by a sinusoidal voltage source coupled to a receive coil that is resonant tuned. The coupling is dictated by the dimensions of the coils and this, in turn can be calculated by first understanding the top picture below (the transmitter): -



Previous answer where the diagram came from.

The receive coil can be assumed to be at point P and therefore it will collect a total flux of approximately B x Area and, knowing frequency of the field you can calculate induced voltage.

So develop some math that gives you induced voltage against the diameters of the coils. What you will always find is that bigger diameter coils makes the problem of distance easier.

Develop your coil size this way and then work out what the coupling factor is at the maximum distance you want.

Then go to a proper circuit simulator (I use micro-cap) and model the circuit using the coupling factor k. You will also need to add a bridge rectifier to the receiver along with smoothing capacitor and simulated load (representing the power consumed).

You can then see how much drive voltage is needed on your transmit coil to get the power output. You will also need to model coil losses (series resistance) for both transmit and receive ends. These will act against you.

At that point you will probably want to figure out how you will resonate your transmit coil and, if you are using a H bridge then series resonance is a likely candidate. Any driving circuit that produces "hard" voltages will need to be loaded by a series resonant circuit. A class A stage would be parallel resonant.

Practical advice: you might consider using ferrite plates behind the Rx coil to reduce the field travelling further and upsetting your laptop. And you will definitely not want your receive coil brought into close contact with your transmit coil because the total induced voltage might by hundreds of volts and blow up your charger circuits.