On 10/14/2015 2:45 PM, Isaac Marino Bavaresco wrote:
> In an inductor you cannot force a current step (that is, the current
> cannot change in zero time, it must follow a curve, or in other words,
> the graph line cannot be vertical).
This I was unaware of.
> In the instant following the transistor turn off, the current stays the
> same as it was when the transistor was on, but now we have a very large
> resistance (ideally infinite) due to the transistor being off. To keep
> the same current, the inductor creates a voltage enough to force that
> current through the new high resistance.
Bingo!  This I did not know.  Awesome.

> Ideally that voltage could be infinite but in our real world that cannot
> be, but it can be very high.
> In practice, the finite resistance of the transistor and other parasitic
> capacitances and resistances prevent the voltage from becoming
> unrealistically high, but expect some hundreds of volts.
>
> The inductor stores a finite amount of energy. The higher the produced
> voltage, the higher the power and less time it take to spend that
> energy, and faster the current drops to zero.

Consider me quite enlightened at this point.  Much thanks.

Cheers,
-Neil.


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