Swend
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By trying a while longer I managed to make a workable simulation (in theory). Although this thread has the name Marx generator, the topology (switching capacitors between H-bridges) appears to be a circuit which I first saw named a Nakagome charge pump. Thus the name on my screenshot.
I didn't see the connection between charge pump and marx generator, but now you say it - I can see it, interesting.
There are no rogue or backward current flows.
I want to see your rogue or backward current flows and try your latest simulation, so I wanted to try your simulator at falstad.com, but falstad seems to be down today.
Since high voltage is present, mosfets are not the right device to use.
I don't understand why you say that? There are much more high-voltage high-current mosfet's available than there are BJT's
To provide bias there may be a suitable node which produces the right voltage at the right time. It may be a supply wire, or a ground wire, or another leg of the same transistor. Sometimes a transistor is not needed because a diode can do the job.
An alternate switching device might be SCR's. They continue to conduct as long as capacitors are charging. As charge current declines to zero, SCR's turn off. This simplifies clocking.
It doesn't sound like a reliable bias to me in this application, especially when the load could be a spark gap, then the circuit will resonate like the church bells of Notre Dame when Quasimodo gives them a spin.
Speaking of spark gaps, you say that in order for a Nakagome charge pump to charge it has to be connected to the load, that would mean it will not function as a real marx generator, if that still holds true in your topology.
The problem with SCR's is their slow turn on/off times, so they are not very suitable for fast switching. What you need is something that is half mosfet and half transistor - the IGBT, then you also get your PN/NP junctions.
BTW, I finally found a spice model for my IGBT's that works in ltspice, so now I can make a better simulation when I put it together in ltspice tomorrow I hope..