Dave Dilatush wrote:
>
> Roman Black wrote...
>
> [snip]
>
> >Please argue, I appreciate anyone who has made SMPS's for
> >25 years, as I know that you learned X things in those
> >years and I learned Y things in those years and it sure
> >beats arguing the football scores... :o)
>
> Roman, this circuit is like one of those "Roach Motel" thingies:
> energy can check into that inductor, but it can't check out.  Under no
> circumstances does ANY of the energy stored in the inductor EVER find
> its way to the output circuit.  Nary so much as a picojoule.

Understood. The energy doesn't have to GO anywhere,
it just needs to be NOT wasted...

> Going back over my previous post, I don't see how I could clarify my
> explanation any; it seems pretty straightforward.

OK. :o)

>
> As a thought experiment you could try the following: assume the
> inductor and the diode across it are both perfect, so that when Q1 is
> off, the inductor current doesn't decay at all.  In other words,
> whatever current was flowing through the inductor at the end of the
> last pulse, is still flowing through it at the beginning of the next.
> And each pulse will increment that current by V * dT / L, where V is
> the voltage across the inductor and dT is the duration of Q1's ON
> time.  Thus each pulse delivers a bigger and bigger shot of current
> into the output capacitor than the one before, which recharges the
> output capacitor back to the threshold level faster and faster, and
> the pulses get steadily more brief- and intense- as time goes by.

Not quite. I think once the inductor is "charged",
ie, it's field is established, the current fed in is
transferred to the output. So each time Q1 turns on,
the current is fed straight to the output, and the
output is at 5vdc, and the inductor maintains its field.
Current by definition follows the water analogy, it flows
in one end and comes out somewhere else.


> Ask yourself, what is there to limit this pernicious process?
>
> No, don't tell me.  Rather than perpetuate this debate and getting all
> vehement about it or anything, why not let's agree wholeheartedly with
> one another (heft a pint with me, here) that regardless of what either
> of us says, the circuit itself will be the final judge.

Heck this weekend I had more than a pint!! :o)

> You've proposed it, now it's time to build and test it.  I look
> forward to seeing your results.

Well, I haven't tested THIS circuit, but I have a few
stepper circuits, that supply 1.0v 5.0A across the motor
(through the motor??) and only draw 24v 0.3A from the
supply. Efficiency is what we are arguing. :o)

So where does the wasted energy go??? If the inductor
is kept "charged" because there is a virtual short
circuit across the coil, the energy is kept WITHIN
the magnetic field, and every SMPS cycle the energy
is still there, it's not wasted. The waste can only
occur when the field collapses and needs to be
re-established.

Hey, this is a good argument! It would be cool if some
others added their 2c worth??
-Roman

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