Re: gEDA-user: Alarm clocks and switching regulators

[DJ Delorie <dj@xxxxxxxxxxx>]

> 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.

The switcher is a stock design from the app notes.  I included the 3uH
output filter as per the app notes.  For kicks, I put a similar filter
on the input.  It turns out that both filters really do help; they
remove some of the high frequency noise.  The caps between the filters
are tantalum; the ones outside the filters are electrolytic.

I put a copy of the power supply schematic here:
http://www.delorie.com/electronics/alarmclock/power.sch
(no, this doesn't include changes to get rid of the 12v buzzing - yet)


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