On 10/14/2015 2:06 PM, Bob Blick wrote:
> ...
> The current will start at exactly what it was right before turning off,
> and drop off quickly.
Bam!  This is what I have been unaware of.   Enlightening!

> Since the time is very short, long term dissipation will be a secondary
> consideration.
Okay.

> You might look at using TVS diodes if you are pushing high currents.
> Even tiny ones have a peak power rating of 300 watts.
>
> But thinking back in this thread, you were originally talking about PWM
> on the injectors after the initial opening. In that case, you'd probably
> be back to using a freewheel diode, not one of these higher voltage
> snubbing methods.
I read something online where someone was doing some experiments with=20
these, and found that with just the freewheeling diode, it would take=20
several (IIRC around 10 ms) to dissipate the energy. That's significant=20
for an injector, so I like the zener idea better -- either across the=20
transistor or together with the freewheeling diode as Isaac suggested. =20
But I've also been trying to figure out why the zener specified in the=20
example circuit for the LM1949 is *seemingly* so small (power rating).

Cheers,
-Neil

--=20
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