Re: gEDA-user: Alarm clocks and switching regulators

[Randall Nortman <geda-lists@xxxxxxxxxxxxxxx>]

On Mon, Sep 24, 2007 at 11:25:01AM -0400, DJ Delorie wrote:
> 
> > DJ -- I notice from looking at your alarm clock boards that you seem
> > to have tried something like this.  Would you care to share your
> > approach and results?  I'd greatly appreciate it.  Looks like you
> > have a diode in there too -- for preventing resonance?
> 
> Yes, the diode is for limiting resonance, and also (in my thinking at
> least) to prevent the other regulators and circuits from leaching off
> the switcher's input filter.

I wonder what would really happen if that diode weren't there?  This
is where I start bumping into the limits of my analog design
knowledge.  With your design, when the diode is reverse biased and
shuts off, there doesn't seem to be any conduction path for the
inductor -- wouldn't this cause the voltage across the inductor to
spike and eventually hit the breakdown voltage of the diode, so that
it conducts in reverse?  And wouldn't that eventually wear out a diode
not designed for it?

If these are stupid newbie questions, my apologies.  I am really a
software guy, and much of these analog stuff is black magic to me.

-- 
Randall


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