Swend
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UF1007 breakdown voltage is a sufficient reason to get not more than 2000 V output from your circuit. You may evaluate this point by reducing the DC input voltage.
In addition it's not clear how the measurement loads the circuit. I'm stumbling upon the term "ground clip", there should be a fully differential high impedance probe.
you can fake a differential probe by measuring the voltage at each end and subtracting
if your 'scope has two probes, it may do the math for you
both probes must be referenced at the same point
I agree it can't work. They claimed the circuit could be extended, apparently without ever checking it. Lesson learnt!So this design will not work for additional stages. And user Easy Peasy warned me against believing everything on the internet, but I thought I was safe this time because it was a IEEE paper.
Why are there so many switching elements in your circuit ? It should be a straightforward RC network with a single switching power source.
If I understand right, the circuit worked in your simulation, thus there's obviously a problem with the implementation, either actual circuit or control pattern.
i guess i missed it
please show how the capacitors get charged, as the only path through the caps is the discharge path
My few bits... I could be totally wrong here, but thought to mention anyhow. Maybe it'll trigger some ideas somewhere.
1) Would it be feasible to share your gate drive circuitry ? It seems to me that in your discharge cycle, in the later stages the IGBT's emitter/ collector will be raised to ever higher voltages. How do you drive the gate in such a scenario ? Some error there vis-a-vis higher voltage operation might explain why each stage works independently but fails when cascaded.
2) What is the 'delay' time in your commutation ? Maybe that's too small - not enough time for some of the charge IGBT's to switch off fully & hence shorting out one complete stage.
3) The voltage drop across Discharge IGBT should surely be lesser than the diode drop in the following stage ? If not, then again this would short out an entire stage during discharge. Maybe put in 2x diodes in series to ensure ?
Do let me know if these are obvious/ irrelevant points, and I'll go back to spectator status.
opcorn:
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And oh !! What about that free-wheeling diode in the IGBT's ? Doesn't that come into the picture somewhere ?
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