I got a little lost in the circuit description, however ringing is normal.
It is caused by the fast switch transition, layout and other unknown
parasitic elements. Exceeding component ratings (both forward and reverse)
and EMI are the major issues.

A traditional RC snubber circuit could be used if needed, however it will
introduce some losses. You could also use a passive lossless snubber but
that is more difficult to design.

-Ken
=20
-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Electron
Sent: Monday, December 26, 2011 1:01 PM
To: microcontroller discussion list - Public.
Subject: [EE] Boost SMPS ringing, maybe it's normal


Is it normal?

Clearly it has to settle someway from the high voltage spike to the normal
input waveform, once the energy is vanished.. but where does the (40 KHz by
the way) ringing come from? 3.3 uF capacitor and 1215 mH secondary of
transformer? The numbers (resonance of LC circuit) say it's not the cap and
the secondary that are resonating, or I would get 80 Hz ringing, not 43 KHz=
..
:P
Probably it's the secondary and.. a 11 pf capacitor, which can be only
parasitic.

Maybe it's even the very 10x oscilloscope probe that is causing it!!

Do I have to live happy with this little and supposedly harmless ringing
(which amplitude is contained within the limits of the waveform, and quickl=
y
damped in 2-3 cycles), or should I fight it like a brave warrior 'till it
dies? :P

Cheers,
Mario


--=20
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