Re: gEDA-user: Switching regulator question

[Steven Michalske <smichalske@xxxxxxxxx>]

On Jun 18, 2007, at 11:33 AM, Randall Nortman wrote:

> On Mon, Jun 18, 2007 at 10:46:31AM -0700, Steven Michalske wrote:
>> Putting a LC filter on the output of the bridge rectifier will help
>> you out.
>
> I looked briefly at LC filters to handle 120Hz ripple.  Requires some
> pretty large, expensive inductors if I'm not mistaken.  Seems cheaper
> in both board space and money to have more capacitance.
>

toroidial inductors work best here.  you don't need full filtering  
here, i'll go dig up some old papers i have on this and get back to  
you laters


>
>> Be careful with over sizing switching power supplies,  what is the
>> minimum operating current of your design?
>
> My understanding is that with low currents that switcher will enter
> discontinuous mode (where inductor current goes to zero at the end of
> each cycle), and this will cause higher output ripple at the switching
> frequency and more overshoot on the voltage.  This is not a big
> problem in my application.  Is there something else that I need to be
> aware of?

Make sure the switching regulator  is designed for it

>
> I haven't calculated minimum current, but I'm guessing 50mA.  (Peak is
> around 350mA, designing for 1.5A. so that's a big range.)
>
>
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