boylesg
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I ended up getting a 12V/5W zener diode and soldered in parallel with the TC4422 ans it seems to work well at protecting the TC4422.
However I seem to have developed a new problem in that I am apparently getting massive currents through the mosfet and primary coil from a new car battery.
The maximum rating of the mosfet I was using is 7A and when you bring the HV and ground close together, such that the resistance drops, there is a good chance that the amps going through the mosfet exceeds 7A. At any rate the mosfet seems to have died and my 4-5A fuse now blows as soon as I connect the circuit up to the car battery.
The TC4422 etc is still OK however as I can still see oscillation through by diagnostic LED.
But some how I need to limit the current to perhaps 3-4A.
I could do it with a resistor easy enough, however the best I have salvaged from tvs are 10W resistors from 2-4R. Some of these are about right but the power that they will have to disipate will be well in excess of 10W.
With a bit of mucking around and arranging a variety of these 10W resistors in parallel and series I managed to get about 4R and about 40W.
I have a 2.2R, 2.2R, 270R and 6.8R in parallel, and then all of this in series with a 2.7R. All that adds up to between 3-4R.
But it is very cumbersome and a pain to adjust if I want more or less current.
What about a ballast inductor? That way I wouldn't need to worry about heat disipation.
But how do you go about calculating the inductance value you need? I haven't been able to find any appropriate online calculators. Do you know of any?
