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Flybacks (was To Kevin)




From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Monday, September 15, 1997 8:03 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Flybacks (was To Kevin)

Hi Alfred,
           A comment on your comment on my comment :)
 
> From:   Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
> Sent:   Sunday, September 14, 1997 1:28 PM
> To:     Tesla List
> Subject:    Re: To Kevin
> 
> On Sunday, September 14, 1997 5:14 PM Malcolm Watts
> [SMTP:MALCOLM-at-directorate.wnp.ac.nz] wrote;
> 
> > My opinion for what it's worth:
<megasnip>

> > I think the flyback is fundamentally an induction coil. It works by 
> > storing energy in the core, then releasing it from core to the load. 
> > The TC we know and love on the other had is a cap discharge device 
> > and is tuned to boot.
> 
> I fundamentaly agree with Malcolm, a flyback transformer CAN NOT 
> function without its ferrite core, by contrast a ferrite core would
> destroy a Tesla coils operation. I do differ with Malcom though on
> the issue of "tuned", typicaly flyback transformers are also tuned, 
> in fact they are designed to resonate at about twice the horizontal 
> oscillator's frequency roughly 30 KHz.

Flyback is a SMPS topology. It is not a requirement of a flyback 
supply that any part of it be tuned. You are talking about one 
designed for a particular application. The one I am building for 
powering my coils is untuned but still a flyback nonetheless. 
Moreover, a core is not a requirement for flyback operation. The only 
thing that differentiates a flyback power supply from a forward one 
is the use of a steering diode on the output side so that the switch 
doesn't directly feel the load. In doing this, turns ratio doesn't 
count in having a say in final output voltage. The only thing 
governing output voltage in a flyback topology is the energy stored in
the coupled pri-sec inductors and the load on either or both coils if
coupling is tight. You can achieve pretty respectable coupling k > 0.9 
in an air-cored transformer. You can do better by confining the flux 
to an airgap with a core.

IMHO,
Malcolm