Re: SSTC probs

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

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

In a message dated 11/25/01 12:22:40 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

<< I know what it's like to cook lots of MOSFETS..
 
 I'm not sure what you mean by the diode between the coil and the MOSFET, 
 I'd need a circuit diagram. With only one MOSFET it sounds a little weird, 
 are you running it in the flyback configuration? If so, I'd suggest two 
 MOSFETS in a half bridge with a high current capacitor to block DC, 
 otherwise you will dissipate a fair amount of heat in your diodes due to 
 flyback pulses, to say the least.
 
 If the heatsink is getting really hot, and the above isn't the main 
 problem, then I'd say your gate drive is too weak. You need a low impedance 
 source with the right ringing suppression. All of this needs a CRO or you 
 won't have any idea how you're going.
 
 Good luck, I've had some fun with my SSTC, but it's shelved because I took 
 out two 900V MOSFETS.. I've gone through too many of them to try again =)
 
 >Matt
 
 Have fun,
 Darren Freeman
 
  >>
I tried a higher voltage supply to power the 555 and it SEEMS to help.I did 
get twice the output but that quickly left.I was back at normal output with 
occasional better output.I think that the MOSFET is taking too much CEMF.How 
can I block it completely?My circuit is just a plain simple 555 pulsinga 
MOSFET.The MOSFEt is directly driving the primary.

Matt