Stepper motor - Unipolar drive
In a unipolar motor, all stator windings share a common terminal, and the free terminal of each winding is connected to a separate power switch and the current is allowed to flow in one direction through the motor windings.
A stepper motor driver typically works in switch mode and includes a current control circuit allowing the current in the windings to be controlled in such a way that it follows a predetermined profile. In half- and full-step modes, the current profile is rectangular, while in micro-step mode it is nearly sinusoidal.
An array of switches is sufficient to drive unipolar stepper motors
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