Low power stepper motor drive system and method

A stepper motor drive system, comprising;

• a stepper motor having a rotor, and a plurality of windings corresponding to a plurality of motor phases;
• means for providing a drive power and applying said drive power to said windings to step said rotor, said means maintaining a different one of said windings deenergized during each step;
• an amplitude and polarity detector and pulse discriminator and selection logic means for detecting a pulse induced into said deenergized winding, and comparing an amplitude and polarity of said detected pulse to a reference amplitude and polarity resulting from stepping said motor in a desired direction of rotation, and for responsively providing an output signal of a first logic level when said amplitude and polarity of said received pulse both correspond to said reference, and an output pulse of a second logic level when at least one of said amplitude and polarity does not correspond to said reference;
• an up/down signal ramping means coupled to receive said output signal and to provide a substantially linearly decreasing ramp signal in response to an output signal of said first logic level, and a substantially linearly increasing ramp signal in response to an output signal of said second logic level, and to apply said ramp signal to said means for providing said drive power.

A stepper motor drive system, comprising:

• a stepper motor having a rotor, and a plurality of windings corresponding to a plurality of motor phases;
• means for providing a drive power and applying said drive power to said windings to step said rotor, said means maintaining a different one of said windings deenergized during each step;
• an amplitude and polarity detector and pulse discriminator and selection logic means for detecting a pulse induced into said deenergized winding, and comparing an amplitude and polarity of said detected pulse to a reference amplitude and polarity resulting from stepping said motor in a desired direction of rotation, and for responsively providing an output signal of a first logic level when said amplitude and polarity of said received pulse both correspond to said reference, and an output pulse of a second logic level when at least one of said amplitude and polarity does not correspond to said reference;
• a history register means for receiving and storing a predetermined number of consecutive output signals of said first and second level and providing an output signal of a first logic level when all the stored signal levels indicate stepping in a desired direction, and an output signal of a second logic level, when at least one of said stored logic levels does not indicate stepping in a desired direction;
• and
• an up/down signal ramping means coupled to receive said output signal from said history register means and to provide a substantially linearly decreasing ramp signal in response to said received first logic level signal, and a substantially linearly increasing ramp signal in response to said received second logic level and to apply said ramp signal to said means for providing said drive power.