Wouter van Ooijen wrote:
>
> Looking at how a (unipolar) stepper driver works I have always wondered:
> couldn't the EMF from the coil that is switched off be used to supply an
> (initial) high voltage to the coil that is switched on?


With an appropriate sized main filter cap and
the typical 4 unipolar flyback diodes, the flyback
from each step will "pump" the main PSU voltage
at the cap. "Jones on steppers" covers this principle
under "electrical resonance" along with a couple of
methods if my memory serves. It's all dark ages stuff
really and relies on tuned motor speeds etc, not like
the good all-round performance from constant current
drivers. :o)
-Roman

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