10 August 2015


Is there a way of protecting a typical MOSFET driver IC from being
taken out by a MOSFET failure in a Class E LF amp?

I was experimenting with drive level into my G3YXM 1kW 136 kHz amp and
managed to blow 2 of the 4 IRFP450 MOSFET's and half the TC4426 driver
chip.

I also came to realize that I did not follow my car engineering
knowledge, and built the thing with little regard to servicing it,
changing the devices was surgically challenging (read a PITA...) and I
should perhaps have put them on PCB screw type connector blocks in a
more accessible position. If I build another that would be my main
change, making repair access far easier!


As an aside why would reducing drive to the amp perhaps cause MOSFET
failure when TX'ing into a dummy load?


I am still trying to find a way to set the over current trip on this,
it's by means of a Hall effect sensor looking at the south pole of the
ferrite choke CH1. The thing draws 12.5 amps tops when TX'ing into a
dummy load, and even with the Hall sensor against the face of the
ferrite (and I am sure I have the south pole end, and the correct face
of the Hall sensor together), it doesn't trip, diagram at
http://www.chriswilson.tv/schematic_modified_2.jpg

Am I going to have to put some stonking big resistor on the output end
of the choke and try and make it draw more current momentarily?

Thanks, and thanks for a most entertaining "LF Weekend" sadly I was
not able to get an antenna sorted in time.




-- 


Best regards,
 Chris                            mailto:[email protected]