Method for measuring winding electrical parameters in bipolar stepper motors during hold condition

A stepper motor driver for controlling a bipolar stepper motor, the stepper motor driver comprising:

• a control logic unit;
• a digital-to-analog converter (DAC);
• two H-bridge circuits for controlling first and second windings of the bipolar stepper motor;
• sense resistors coupled to the H-bridge circuits;
• and
• wherein the control logic unit is configured to:
• determine desired current signals for the first and second windings based on a given rotational position of the bipolar stepper motor;
• convert the desired current signals into analog reference voltages using the DAC;
• generate pre-drive signals based on the analog reference voltages;
• control the two H-bridge circuits using the pre-drive signals to regulate currents through the first and second windings;
• and
• monitor voltage drops across the sense resistors to provide feedback for adjusting the pre-drive signals;
• wherein the desired current signals are determined by generating time-varying periodic current patterns for the first and second windings, wherein the current pattern for the second winding is phase-shifted relative to the current pattern for the first winding, and wherein both current patterns are dependent on a step frequency of the bipolar stepper motor.