Methods and apparatus to sense changes in a load of a stepper motor

At least one non-transitory computer readable storage medium comprising instructions that, when executed, cause programmable circuitry to at least:

• determine a first duty cycle of power transferred to a stepper motor during an operation of the stepper motor, the first operation to supply power using currents of a target magnitude;
• determine an average duty cycle from previous duty cycles of power transferred to the stepper motor during previous operations of the stepper motor, the previous operations to supply power using currents of the target magnitude;
• and
• determine changes in a mechanical load applied to the stepper motor responsive to a comparison of the first duty cycle to the average duty cycle.

An apparatus comprising:

• duty cycle determination circuitry capable of:
• determining a first duty cycle of power transferred to a stepper motor during an operation of the stepper motor, the operation to supply power using currents of a target magnitude;
• and
• determining an average duty cycle from previous duty cycles of previous operations of the stepper motor, the previous operations to supply power using currents of the target magnitude;
• an error amplifier capable of comparing the first duty cycle to the average duty cycle;
• and
• peak current control circuitry capable of adjusting a peak current of the supply of power responsive to a comparison of the first duty cycle to the average duty cycle.