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Re: 250watt solid-state flybacks? (fwd)





---------- Forwarded message ----------
Date: Tue, 12 Oct 1999 12:44:18 EDT
From: NickandSim-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: 250watt solid-state flybacks? (fwd)

Hi David,
             ditch the 2 lead acids for a start.  The power you can put into 
most flybacks at 24V would be more like 50W or 100 if you were lucky.  I 
suspect I was the guy who said you can get 250W into a flyback.  For this I 
used a 70V supply and put about 4A in but the FETs burnt at least 30-40W of 
that so cal it 250W.   
The basic system is fairly simple, a square wave oscillator, a a fet driver 
chip and a large FET or bipolar.  It is easier to use fets as they draw a lot 
less base current and make life easier for the driver.  If you use the 555 as 
your oscillator you can drive it straight into the FET as the 555 can 
sink/source 500ma, remember to put a snubber network in tp protect the 555, 
this isn't really necessary but it easier to take little peracutions that 
cost almost nothing than keep blowing chips.
I would question whether you need that much drive power as all that the 
higher power seems to do is heat up the flyback and make the sparks more 
intense.  I have tried up to 2kW into a flyback and all it did was shoot a 
huge arc then blow itself to bits leaving little more than a scorched core.  
For your application I would say that you want about a 100W or so.  Therefore 
I would have thought you could get away with about 40-50V drive depending on 
your flyback.

Have (Head Mounted) Fun
Nick Field