Re: SSTC FET drive xfrmr

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "robert & june heidlebaugh by way of Terry Fritz <teslalist-at-qwest-dot-net>" <rheidlebaugh-at-desertgate-dot-com>

Sean: yes your coupeling could cause waveshape problems. Your use of
"zipcord" is not a good choice. In the same light the band width of your
coil is not good because your interwinding capacitance is high. With only 15
turns your base frenquency is probibly about 30 Mhz. I would recomend about
27 turns  of good wire best being bi filer wound, but not required. Even the
use of 2 strands of ribbon cable would be better than zip cord. Your circuit
requires low frequency pass and high frequency for wave shape. A good coil
should pass from 5 Mhz to 150 Mhz flat. Even that is not ideal on the low
end.
    Robert  H
-- 


 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > Date: Wed, 19 Mar 2003 17:09:28 -0700
 > To: tesla-at-pupman-dot-com
 > Subject: SSTC FET drive xfrmr
 > Resent-From: tesla-at-pupman-dot-com
 > Resent-Date: Wed, 19 Mar 2003 18:52:35 -0700
 >
 > Original poster: "Sean Taylor by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > <seantaylor-at-attbi-dot-com>
 >
 > Hi all,
 > I'm trying to make a FET drive transformer, and so far I'm not too
 > successful.  Right now it's just 15 turns of 22 gauge zip cord on a ferrite
 > core.  The input and output waveforms can be seen at:
 > http://hot-streamer-dot-com/temp/fetdrv.bmp
 >
 > The top trace is the input to the tranformer, the bottom trace is the GE
 > junction of my IGBT.  I know the capacitance changes with the CE bias, but
 > it was just for testing.  I also simulated the junction with a capacitor to
 > see if it would act the same, and it did.  Anyway, as you can see, the rise
 > time is horrible on the IGBT side of the transformer.  Is this just because
 > the coupling between the winding is too low, ie the two windings aren't
 > wound around each other first?  The drive is a TC4421, and I have a couple
 > bypass caps in series for DC blocking, cause right how it's only operating
 > SE, but eventually the driver will be a full bridge.  Thanks for any help!
 >
 > Sean Taylor
 >
 >