Re: [TCML] Gate Drive Waveforms Ringing

[Joshua Johnson <jjohnson98@xxxxxxxxx>]

I had the same problem and it was because I used a different scope probe
that was uncalibrated.
Calibrate the probe and it may fix the issue.
Just a thought.

Josh

On Tue, Aug 18, 2009 at 7:55 PM, Brian <brianv@xxxxxxxx> wrote:

> Hi Guys,
>
>
>
> I have questions for the SSTC people out there, I have some ringing on my
> gate drives and for the life of me I cannot seem to get rid of it. The
> signal used to be as clean as can be and now it has developed a ringing
> that
> has me totally befuddled.  I rewound the GDT and changed the IGBT so they
> are all good, the GDT used to have a really nice looking waveform. I have
> also changed the lead lengths going back to the control board and nothing
> seems to change. I have uploaded a few images so you can see what it looked
> like and what it looks like now. I have also uploaded the H-Bridge output
> waveform and you can see it has a large amount of ringing at the beginning
> of each transition. Also the other thing I should mention is when only 1 of
> the GDT are connected the signal is very clean again, it makes no
> difference
> which one is connected the signal is good, the moment the second GDT is
> connected the ringing begins.
>
>
>
> Here are the links for the waveforms:
>
>
>
> The Good waveform:
> http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing001.jpg
>
>
>
> The waveform now:
> http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing005.jpg
>
>
>
> H-Bridge output waveform:
> http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing004.jpg
>
>
>
> I did add additional gate resistance and it helped somewhat in fact I added
> until I was way over damped and it of course it began to distort the
> waveform.  But anyway I am not sure why this just all of a sudden showed
> up,
> so I thought I would post it here and see if anyone has a similar issue and
> what they did to correct it.
>
>
>
> Thanks Much
>
>
>
> BrianV
>
>
>
>
>
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