On Tuesday 01 April 2003 10:00 am, Gregory A. Pruden wrote:
> Thanks Ned,
> You are right I looked at the current in the cap and the simulation
> shows between 12A and 42A depending on the ESR.
>
> Could you point me to an example, or suggest the movement of the
> components, for the buck DC-DC circuit?
>
> Gregory
>

A quick Google search for "buck converter" theory got:
http://www.ipes.ethz.ch/ipes/e_index.html

There are also a number of app notes at Linear Tech, ON Semi, and TI
about these.

> -----Original Message-----
> From: Ned Konz [mailto:ned@BIKE-NOMAD.COM]
> Sent: Tuesday, April 01, 2003 12:32 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE] Filtering for a tec
>
> On Tuesday 01 April 2003 09:02 am, Gregory A. Pruden wrote:
> > I tried moving the cap
> > to the drain of the MOSFET as this looked more like the examples
> > that I had seen.  I also added a second cap on the back as it
> > appeared to help.  This raised the current to 2.6A but the cap
> > closest to the drain of the mosfet either bakes or explodes.
> > This cap is circled red in the attached schematic.
> >
> > I have this circuit modeled in spice (SwitchCadIII) and it
> > appears to do exactly as I hoped but alas in practice it smokes.
> > As an aside using very low esr caps really seem to help the
> > overall operation in the simulation.
>
> You probably don't want a filter here. If you're using an inductor,
> you should probably set it up as a buck DC-DC converter. This will
> be much more efficient. Same components but arranged differently.
>
> Anyway, if you look at the current through the capacitors, you'll
> see why your cap is exploding.
>
> --
> Ned Konz
> http://bike-nomad.com
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