Re: S.s. MOSFET-driving

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

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

I have used a variety of opto-isolators. I have used commercial IC's and I
make my own out of parts from old slopy disk drives I junk out. I have glued
a LED end to end with a photo diode and I have cut (sanded) the end off
metal transistors and mounted a LED in the end with cleer epoxi. In high
voltage I prefer my homemade ones to the commercial. 1/4 in seperation stops
a lot of high voltage problems, and black paint stops light.
  Robert  H

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Sun, 30 Dec 2001 11:53:54 -0700
> To: tesla-at-pupman-dot-com
> Subject: Re: S.s. MOSFET-driving
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Sun, 30 Dec 2001 15:21:10 -0700
> 
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> Hi Ken,
> 
> You may want to see Marco's discussion of IGBT drive problems and fixes at:
> 
> http://personal.inet.fi/atk/dncmrc/
> 
> I found that I needed series resistance (100 ohms) to slow down the IC's
> switching speed or they would blow the IGBTs.  The IC designers wanted to
> force
> the gate capacitance to the voltage they want instantly and they did a bit
> "too" good of a job ;-))  That is the only trouble I ran into but I don't
have
> transformers and such (fiber optic).
> 
> Cheers,
> 
> Terry
> 
> 
> At 01:31 PM 12/30/2001 -0500, you wrote:
>> 
>> There's been mention made recently of the IR2110-series ICs for driving
>> Tesla-coil MOSFETs.  A long while back I had intractable trouble using those
>> ICs, seemingly because the very high-impedance voltage-translating circuitry
>> within the IC was being affected by the coil's electric field.  I had to get
>> rid of the IC-drive scheme and go to discrete-component drivers + isolating
>> transformers.  For the latter, I just use readily-available common-mode
>> chokes (2 windings on a toroid) connected as 1:1 transformers.
>> 
>> And as to the transformer-drive...I additionally found a problem in that,
>> every time drive was cut off at the termination of a spark-event, the
>> transformer's flux would have to reset to 0 and that would cause the MOSFETs
>> to turn on spuriously.  I had to add additional circuitry to eliminate that
>> turn-on.
>> 
>> Ken Herrick
> 
> 
> 
>