Linear or Switch Mode Power supply for PWM Driven Stepper Motors?

Yes, it can work for servo-motors as well.  There are a few ways to achieve this result.  I am a stinker to use the abbreviation 'CCS' because it literally stands for 'constant current source,' when I mean 'constant current sink.'  In Si, electrons are a little lighter and faster than holes.  So if a circuit could use either an N-type or a P-type power switch, we choose the N-type.

The principle is simple.  Nature provides us with potential ('voltage') sources more often than current sources.  Energy stored in a coil is LII/2.  That energy, in the case of our motor, goes mostly into magnetizing the core.  We would like to energize our motor with a constant current  source, since then our magnetic flux would be established immediately and our motor could then go really, really fast.  Current sources, alas, don't really exist, we have to simulate them.  Here, momentarily, our CCS would have to be able to source nearly infinite potential!  Nature, of course does not supply us with either an ideal current source nor an ideal voltage source.  This shows us, once again, the good grace of the almighty:  If V=IR and Power = IV, crowbar-ing a voltage source or leaving a current source open would destroy the universe, obviating whatever purpose our project entailed.  Batteries are ideal voltage sources coupled with intrinsic, series (Thevenin) resistors.  Current sources would have intrinsic shunt (Norton) resistors, keeping our world intact.  It is equivalent, and maybe a bit more ingenuous to state that current-sources have a 'voltage-compliance-limit.'

What happens in real life is that a super-voltage is temporarily applied to our coil when we want to start it up or change its direction.  Back emf provided by our load temporarily makes it seem to be a more resistive load than it really is, momentarily, until the core saturates.  Once it does, we often want to reduce our current, in the case of a stepper, down to an amount that represents 'holding torque,' rather than an attempt to further turn the rotor.

Current is sensed, somehow, the simplest method being a current-sensing resistor.  This is used as the sensor in a negative-feedback loop that either modulates the conductance of, or chops the power switch, simulating a current source.

Physically, now our (stepping motor) has an extra spurt of power when beginning to transition.  Since I have reached my majority, I seem to fart when I de-couch.  The kids around here refer to this as turbo-assist.  I am not always that good with analogy.

Sometimes, we need to use Ohm's law to infer coil current from published potentials and coil resistances.  This is usually with small motors.

Yes, it can work for servo-motors as well.  There are a few ways to achieve this result.  I am a stinker to use the abbreviation 'CCS' because it literally stands for 'constant current source,' when I mean 'constant current sink.'  In Si, electrons are a little lighter and faster than holes.  So if a circuit could use either an N-type or a P-type power switch, we choose the N-type.

The principle is simple.  Nature provides us with potential ('voltage') sources more often than current sources.  Energy stored in a coil is LII/2.  That energy, in the case of our motor, goes mostly into magnetizing the core.  We would like to energize our motor with a constant current  source, since then our magnetic flux would be established immediately and our motor could then go really, really fast.  Current sources, alas, don't really exist, we have to simulate them.  Here, momentarily, our CCS would have to be able to source nearly infinite potential!  Nature, of course does not supply us with either an ideal current source nor an ideal voltage source.  This shows us, once again, the good grace of the almighty:  If V=IR and Power = IV, crowbar-ing a voltage source or leaving a current source open would destroy the universe, obviating whatever purpose our project entailed.  Batteries are ideal voltage sources coupled with intrinsic, series (Thevenin) resistors.  Current sources would have intrinsic shunt (Norton) resistors, keeping our world intact.  It is equivalent, and maybe a bit more ingenuous to state that current-sources have a 'voltage-compliance-limit.'

What happens in real life is that a super-voltage is temporarily applied to our coil when we want to start it up or change its direction.  Back emf provided by our load temporarily makes it seem to be a more resistive load than it really is, momentarily, until the core saturates.  Once it does, we often want to reduce our current, in the case of a stepper, down to an amount that represents 'holding torque,' rather than an attempt to further turn the rotor.

Current is sensed, somehow, the simplest method being a current-sensing resistor.  This is used as the sensor in a negative-feedback loop that either modulates the conductance of, or chops the power switch, simulating a current source.

Physically, now our (stepping motor) has an extra spurt of power when beginning to transition.  Since I have reached my majority, I seem to fart when I de-couch.  The kids around here refer to this as turbo-assist.  I am not always that good with analogy.

Sometimes, we need to use Ohm's law to infer coil current from published potentials and coil resistances.  This is usually with small motors.