High voltage high power NFET switch controlled by ignition switch

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Zac1

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Long story short, I have built "Spark switch" that is floating around the internet to be used with battery and ESC controllers and it works. Now what i did not realized (or somehow missed) is that switch works in reverse and IMO this isn't particularly safe (in case of cutting wires). It means if physical switch if OFF (wires are NC) switch turns ON.

I've been trying to reverse that logic but it proved to be non trivial problem (LT spice shows gigantic (700+MW) spikes). My main concern is reliability. So my question is, what would be correct way to approach this?

Schematic:

PCB, nothing fancy, mosfets are suppose to be cooled and from the other side but for tests i couldn't bother:
 

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Hi,

I´d say I´m quite experienced with reading schematics.
But I totally miss any information about working principle, timing, voltages, currents....

You make it really hard to help you.

The only value I see is "700 + MW" .. I can only imagine that it means "more than 700MW" which is huge. It equals the power of a small nuclear power plant.
It makes no sense.

I guess I just should not respond to such posts. But then the OP never will know that there is a reason why there is "no response".

Klaus
 

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KlausST said:
The only value I see is "700 + MW" .. I can only imagine that it means "more than 700MW" which is huge. It equals the power of a small nuclear power plant.
It makes no sense.
Click to expand...
Exactly, it makes no sense not matter what i try in LTspice. So long story short, all ideas I had were kinda nonsensical, as a last ditch effort i made a "simple" sim with octocoupler:

Problem is, it still wastes quite a lot of power during startup and shutdown (~160W for about 1s) i am not sure how big of a problem will it be)

So I am asking what would be best solution for this?

 

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Hi,
Zac1 said:
So I am asking what would be best solution for this?
Click to expand...
What solution for what problem? You are talking in riddles.

Still missing any useful circuit description and specifying values.
I better leave the thread instead of annyoing you by asking for the same basinc informations again.

Good luck
Klaus
 

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KlausST said:
Still missing any useful circuit description and specifying values.
Click to expand...
What do you mean specifying values? Operating parameters? 30-180V up to 0-200A. There is kind of a reason why i have chosen 1M resistors and 4x IRF200P222
Its a switch that is suppose to work with batteries and ESC.

But then again, that isn't a big problem here, Im fairly sure it is almost irrelevant to problem at hand which is:

How to drive a mosfet gate efficiently enough as a switch so it doesn't burn out with unknown variable voltage source?

I don't know what else do you want me to say? Its simply suppose to be a universal "High voltage high power NFET switch"

Here is what i mean by reaching absurd power losses:
 
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