Re: SSTC bridge driver

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

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

Oops, I just noticed that someone replied back and said the snubber was 51K
in series with 1 nF.  NO!, that won't do anything!

Use 51 ohms in series with 1 nF for the snubbers.

Shaun


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, February 02, 2004 8:56 AM
Subject: RE: SSTC bridge driver


 > 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<<<<<<<<<<
 >   >
 >