Re: S.s. MOSFET-driving

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Ken,

Richie has a bunch of tips for protecting TC FETs too at:

http://www.richieburnett.co.uk/mosfail.html

Cheers,

        Terry

At 12:43 PM 12/31/2001 -0500, you wrote: 

>
>>
>> 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
>>
>>
>
>
>
> Terry-
>
> Thanks for the tip; I'll check it out.  It's likely that the 100 ohm resistor
> damps out destructive oscillation, which will occur when the low-Z and very
> fast drive signal meets up with the MOSFET's gate capacitance.
>
> Ken