Re: TESTED works, Flyback driver plans

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Justin,
           Have you put a scope probe on the MOSFET drain to see what 
kind of flyback voltage is appearing across the primary? I suspect 
the substrate zener in the MOSFET is saving it from destruction and 
is probably dissipating a lot of the power which is warming up the 
heatsink. ?

Regards,
malcolm

On 15 Oct 2001, at 7:19, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Pyrotrons-at-aol-dot-com>
> 
> Hi All.
> 
> I have been experimenting with MOSFET flyback drivers heavily for the past 
> several weeks. 
> 
> Think I got a design DOWN now. Works great. Will drive a flyback up to 3.5" 
> arcs, yet I've not killed a MOSFET rated 100V. I'm still using the original 
> one (IRF540) that I started with....even through testing and prototype,
which 
> is rare.
> 
> Thanks to Jan Wagner for helping me solve the "my 555 keeps dying!!" problem 
> ; ) I haven't killed a single chip since that electrolytic went in across V+ 
> and ground at the chip (which was Jan's advice).
> 
> Using an IRF840 or similar (500V MOSFET) the circuit would be bulletproof. 
> The only thing that dies is the flyback, because I drive them at about 10 
> times they're rated power for fun ; )
> 
> To quote Aron, "the whole thing glows purple" and "it eats itself from the 
> outside in".
> 
> It's late at night right now, I could have screwed up somehow with the 
> website. I've triple checked everything, it should be good. Please, someone 
> let me know if they find a significant error.
> 
> Take care, I do hope someone enjoys this. 
> 
> Justin Hays
> KC5PNP
> G-3 #1150
> Email: pyrotrons-at-aol-dot-com
> Website: www.hvguy-dot-com
> 
> 
> 
>