RE: SSTC bridge driver

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

Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com> 

Interesting. I wonder if this would have helped some situations I have
seen leading to blown FETs. Dan's tests and Sims are great, but while
under audio mod you can get some nasties from Fr instability (how can
you be right on tune with loud music?). The feedback control may lag? I
personally can't see what's wrong with a added snubber circuit, yes it
does increase complexity and component count, but...

Thanks,

David Trimmell



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, February 01, 2004 4:51 PM
To: tesla-at-pupman-dot-com
Subject: Re: SSTC bridge driver

Original poster: "Shaun Epp" <scepp-at-mts-dot-net>

David,

The snubber circuit was an addition, I left the 1kohm in place.
The ringing on my board was so bad that it fired the mosfets on and off.
To
see if you board does this, scope the output and use a light bulb as the
load.  If you see sharp spikes on the waveform then it's a problem.  The
snubbers fix this.

On another post, and where I've read elsewhere was that the leakage
inductance is the
culprit, but I twisted my three wires together before I wound them on
the
core and I kept the leads short as possible to the circuit board.  I
don't
think that that was the problem.  I also increased the value of the
coupling
capacitor from the driver chips to the gate transformer.  I went from
0.1 uF
to 1.0 uF polypropylene.  I did this after playing with the snubbers, It
makes the waveform look more square and clean.

Shaun

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, February 01, 2004 7:54 AM
Subject: RE: SSTC bridge driver


  > Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com>
  >
  >
  > Shaun, so you replaced R5-8 (1K) (PlasmaSonic II) with series 51K and
  > 1nF cap? Or was this in addition to?
  >
  > Thanks,
  >
  > David Trimmell
  >
  >
  > From: Tesla list [mailto:tesla-at-pupman-dot-com]
  > Sent: Saturday, January 31, 2004 4:57 PM
  > To: tesla-at-pupman-dot-com
  > Subject: Re: SSTC bridge driver
  >
  > Original poster: "Shaun Epp" <scepp-at-mts-dot-net>
  >
  > I've got the answer to the ringing problem.  SNUBBER circuit!  I use
a
  > 51
  > ohm 1/4 watt resistor in series with a 1 nF capacitor. I put this
combo
  > across the gate transformer outputs and it gives a good response.
On
  > my
  > plasmasonic board I'm running at 240 khz and the ringing was about
  > 13Mhz.
  >
  > I hope this helps,
  >
  > Shaun Epp
  >
  >  >>>Snip<<<<<<<<<<
  >