Re: Isolated FET/IGBT Pulse Driver for HV Applications ...

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Original poster: Sparktron01@xxxxxxxxxxx 

Hi Rajesh
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>
> The zetex FETs are not available in my place. Can I replace those
> FETs with IRF540 or IRF9540 ? Those transistors are easily available
> in my place.
>
> Has anyone tried the same circuit using some other FETs ?
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<SNIP>

In short, I don't know.  Comparing the ZETEX vs IRF
parts, the IRF parts have 60 times (P channel) or ~100
times (N channel) higher total gate capacitance of
ZETEX parts; this usually equates to higher charge
(CV) to operate gates and thereby slower slew rates
(t ~ CV/I)

The circuit may still work, but satisfactorily only at
lower frequencies (<100kHz) due to gate capacitive
loading effects.  You will have SIGNIFICANT drive
capability as an offsetting benefit, however
 (17A, 19A IRF versus ~+/- 2A ZETEX).
That capability would clearly drive the largest IGBT
"brick" one could imagine.

There may be a higher current buffer available to
drive the circuit (maybe like a small gate drive
transformer/FET driver like the TI UCC37322,37321 series)
to drive the differentiators versus using the CD4049's,
which even paralleled are little "wimpy" for my liking.
470pF coupling capacitors will have to be size adjusted
larger to allow enough charge transfer to keep
gating speed up.  If you use "amp capable" drivers
in place of the '4049 inverters, the switching diodes
(1N4148) would need to be uprated to 1N5819 (1A)
or 1N5822 (3A) schottky diodes I would think to handle
available switching current(s).

Build it and let us know how it performs with higher
power parts...        :^)

Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA