Sensing inductance change in high power (20 watts) wireless transmitter
If you make your induction coil system self oscillating then when properly set up the switching losses will be low .This means that its running at its resonant frequency .Now when your object comes near the effective circuit inductance changes .If you move your object the change in frequency will be visible on a frequency counter.I got a freq change of 8% which was adequate for running some sort of decision circuit.I know that your job is different but if you get a reasonable freq shift then you will be able to reliably detect absence or presence of the object .You could do this detection at low power and go to full power when the object is present .On my job i used buck convertor to control input to induction heater .I suppose you could strobe your system to save power .Frequency detection is easy for people to do in code these days .