Re: U.S. Pat 6,366,028 LED Flashlight Circuit

"Mark Zenier" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> In article <[EMAIL PROTECTED]>,
> Robert Monsen <[EMAIL PROTECTED]> wrote:
> >I believe the thing that was happening with the LEDs that I have is that
> >there was some capacitance across the LED. When I put the diode in
series,
> >it stopped behaving badly, and the efficiency of the simulated circuit
> >doubled.
> >
> >Also, oddly enough, the voltage between the LED and the diode got 'pumped
> >up' similarly to what would happen if you had a cap/resistor in parallel
in
> >place of the LED.
> >
> >This may just be some artifact of the blue LEDs I'm using (and simulating
> >with.)
>
> I've not looked at your circuit, but it might be "reverse recovery time".
> where a diode looks like a short circuit for a microsecond or so after
> the applied voltage changes, until the charge carriers get swept out
> of the diode junction (or something like that).  It depends on the
> size/construction of the diode and small signal diodes are supposed to
> avoid or minimize it.
>
> Or it could be the reverse breakdown voltage.
>
> I don't trust a simulator get get either of these correct, off the shelf.
>
> Mark Zenier  [EMAIL PROTECTED]  Washington State resident
>

Out of curiosity, I built a shunt around the diode controlled by a
pushbutton, and scoped the junction at the inductor. With the diode, the
scope looks just like the simulation. Without the diode, the scope looks
completely different. So I'm guessing that, as you said, the LED simulation
is simply wrong. On the scope, the only real difference is that the peak is
higher with the diode, which makes sense, since the inductor has to bring up
the voltage to cross two diode junctions instead of one.

Thanks for looking at this.

Regards,
 Bob Monsen