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Re: Solid State coils.

At 08:30 AM 4/22/96 +0700, you wrote:
>>From 100624.504-at-CompuServe.COM Fri Apr 19 20:12 MDT 1996
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<tesla-at-grendel.objinc-dot-com>; Fri, 19 Apr 1996 17:50:29 -0600
>Date: 19 Apr 96 19:46:55 EDT
>From: Alan Sharp <100624.504-at-CompuServe.COM>
>To: "INTERNET:tesla-at-grendel.objinc-dot-com" <tesla-at-grendel.objinc-dot-com>
>Subject: Re: Solid State coils.
>
>Greetings,
>
>Ive had fun, and smoked a lot of FETs
>driving my primary coil. But I think I
>need another approach. 


>My present circuit is essentially a big
>flyback transformer. Set up a current in the
>primary, switch it off and in theory the energy
>has no where to go but into the secondary.
>In practice, very high voltages appear in the
>primary, with unfortunate effects on the
>electronics!!! It runs better clamped but
>it looses a lot of voltage. 

>I may in time try a full bridge but I havent
>tried driving high side FETs.

Those things run on smoke 
thats why if you let the smoke out 
they quit working ;)

>Im going to go to bottom feeding.
>I have ordered a transformer (ETD 49).
>Im planning to drive it in push pull, I
>think I know how to do this.

>Could an electronics wizard tell me
>if Ive got all this right:

>1. Abandon the strip board for a double
>sided PCB. One side devoted to ground
>(ground plane). Power connections at
>least 1cm wide, hot shoe the FETs.
>Short path to gates, snubbers

 Use two small boards one for FETS other for 
 drive circuit. Use one ferrite transformer (donut type), 
 primary/ two secondaries for push-pull (One for each FET)
 one secondary for flyback type drive, to isolate between
 FETS and drive circuit. Use as few turns on primary as
 possible 10 or less. Don't be afraid to shoot for 200KHZ
 I think faster is better as far as air-cores go. 
 use feedback to sincronize your driver. 
 
 Get an O-scope if you dont have one. 
 20MHZ 2channel $400 

>2. 2 IRF740s on each side, mounted
>on a 2 c/w heatsink have handled
>2A -at- 150v, 200kHz continuous.Ill
>use 4 to allow more power later.

Im working on one that is push-pull driven series LC 
primary using 10 IRF630's  20A continous at  150-170V
3KW more or less.