Power transfer based stall detection techniques for stepper motor

A circuit adapted to be coupled to a coil of a motor via an H-bridge circuit, the circuit comprising:

• a duty sensor coupled to the coil and configured to provide raw run duty data responsive to a coil current through the coil;
• a first subtractor coupled to the duty sensor and configured to provide a differential duty signal responsive to a stall duty signal and a run duty signal based on the raw run duty data, the differential duty signal having a first duty subset signal and a second duty subset signal, wherein the first duty subset signal corresponds to a first quadrant of a half-cycle of the coil current and the second duty subset signal corresponds to a second quadrant of the half-cycle adjacent to the first quadrant;
• a second subtractor coupled to the first subtractor and configured to deduct the second duty subset signal from the first duty subset signal to provide a quadrant differential duty signal;
• and
• a comparator coupled to the second subtractor and configured to provide a stall signal responsive to the quadrant differential duty signal and a threshold value.

A stepper motor driver adapted to be coupled to a coil of a stepper motor, the stepper motor driver comprising:

• an H-bridge circuit connected to the coil and operable to provide a coil current to the coil;
• a gate driver coupled to the H-bridge circuit and operable to control the H-bridge circuit by providing a pulse modulated signal to the H-bridge circuit;
• and
• a stall detection circuit coupled to the coil and configured to monitor power transferred to the stepper motor through a duty cycle of the pulse modulation signal, the stall detection circuit including:
• a duty sensor coupled to the coil and configured to provide raw duty data responsive to the coil current;
• and
• a comparator coupled to the duty sensor and configured to provide a stall signal indicative of an operating condition of the stepper motor based on the raw duty data.