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> Date: Mon, 6 Jan 2014 16:04:07 +0100
> To: piclist@mit.edu
> From: electron2k4@infinito.it
> Subject: [EE] Boost SMPS turn-OFF best current value
>
>
> Hello,
> I'm playing with a self-made boost converter, all the logic
> is made via a PIC and its ADC's.
>
> I'd like to ask some general questions:
>
> in my first experiments, I was turning ON the transistor switch,
> then monitoring the current in the inductor, then turn OFF the
> transistor till the current reached 0, and again in a loop.
>
> My aim is to get the most possible power out of the power supply.
>
> Now I think that if I turn OFF the transistor earlier, say 100mA
> below the "OFF" threshold (maximum current), instead of reaching
> 0, then the average current will be higher, and I will get more
> power from the circuit.
>
> Is my reasoning correct?

Yes. =A0If you view the current waveform of a properly designed bucking LED=
 driver, you will see the current rising and falling, but never reaching ze=
ro. =A0Although it does not use a microcontroller, the Velleman K8071 is a =
good example.

> What is the criteria to choose the inductor? As my PIC-based
> circuit is relatively slow, I noticed that only inductors around
> 10mH work, whatever has a smaller inductance probably charges
> and discharges too quickly to work.
>
> So the best inductor I should choose is the one that has (of
> course) the least possible resistance, but an high enough
> inductance to let my slow PIC work correctly?
>
> No other recommendations?
>
> For example, don't inductors have a maximum voltage rating?

Since an inductor is just a coil of wire, there is usually only current to =
worry about. =A0The only time you have to worry about voltage is if somethi=
ng is near enough to the coil and is at such a different potential that the=
 insulation might be punctured. =A0Most of the time this is a non-issue. =
=A0Just stay below the current rating of whatever gauge wire the inductor i=
s wound with and you will be fine. 		 	   		 =20
--=20
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