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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: My flyback experiment is on the web
References: <3DAA0563.9040507@BOGUS.earthlink.net> <email@example.com> <3DAB8ABA.4030602@BOGUS.earthlink.net> <firstname.lastname@example.org> <3DAC188B.7D82A78E@rica.net> <3DAC2D91.email@example.com> <3DAC688E.9C870D83@rica.net> <firstname.lastname@example.org>
Date: Wed, 16 Oct 2002 00:07:58 GMT
NNTP-Posting-Date: Tue, 15 Oct 2002 20:07:58 EDT
John Larkin wrote:
> On Tue, 15 Oct 2002 19:12:16 GMT, John Popelish
> >I disagree with you and Fred. The ringing should be a damped
> >sinusoid, not a series of fractional sine pulses if it were just
> It can't make a damped sine because of the fet substrate diode. This
> waveform is characteristic of drain circuit ringing.
I understand how the stray (inductor, wiring and drain) capacitance
charged up to output voltage will drain through supply voltage and
thus charge up the inductor with current which then drives the voltage
below zero (assuming that output voltage is more than twice supply
voltage). But that current is drained to zero through the diode, and
then the capacitance is charged again towards supply voltage which
runs the inductor current up the other way enough to drive the
capacitance up to twice the supply voltage. But then all subsequent
ringing should be centered on supply voltage, and not ever forward
bias the diode. The rest of the wave should be a damped sinusoid
centered around the supply voltage. This is not at all the waveform
shown. I see signs of repeated turn on of the fet.
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