The Cyber-Spy.Com Usenet Archive Feeds Directly From The Open And Publicly Available Newsgroup Sci.Electronics.Design
This Group And Thousands Of Others Are Available On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic, Opinions Or Content Posted To This Or Any Other Newsgroup. This Web Archive Of The Newsgroup And Posts Are For Informational Purposes Only.
From: Uwe Zimmermann
Newsgroups: sci.electronics.design
Subject: Re: My flyback experiment is on the web
Date: Mon, 14 Oct 2002 15:16:40 +0200
Organization: Royal Institute of Technology, Stockholm, Sweden
Message-ID: <3DAAC3B8.E25D3718@imit.kth.se>
References: <3DAA6CED.40BE9278@imit.kth.se> <20021014042934.11436.00001540@mb-me.aol.com>
NNTP-Posting-Host: bb-62-5-38-147.bb.tninet.se
Mime-Version: 1.0
NNTP-Posting-Date: Mon, 14 Oct 2002 13:17:33 +0000 (UTC)
X-Mailer: Mozilla 4.79 [en]C-CCK-MCD {SillyDog} (Windows NT 5.0; U)
X-Accept-Language: en,de,sv,ru
Gibbo wrote:
>
> Uwe Zimmermann uwe@imit.kth.se wrote:
>
> > Uo = (T/toff) * Ui
> >
> >in your case
> >
> > T/toff = Uo/Ui = 11
> >
>
> This equation assumes a perfect world with no parasitics and no losses. In
> practice it's far from ideal and will result in a much lower than required
> output voltage.
> >the current should flow through the inductor only during 1/11th of the
> >pulse period (=1/fswitch)
it was only my fault, the duty cycle according to this equation has of
course to be 10/11 and not 1/11 as stated in my original reply.
This is consistent with the short duration of the drain voltage peak
as seen in Chris' scope images.
In my experience using using appropiate inductors, this comes quite
close to reality...
>
> This will then force the unit to run with a low output voltage and too close
> (perhaps even into) continuous mode.
>
> I think you're right that at 50KHz the inductor is a bit low in value but 330uH
> is too high.
>
> None of this explains the poor efficiency which seems to be losses in the core.
>
Uwe.
Go Back To The Cyber-Spy.Com Usenet Web Archive Index Of The sci.electronics.design Newsgroup
|