Patent ID: 6861817

Claim:
An apparatus for detecting a stall condition of a stepping motor of the type which includes at least first and second coils and a rotor having a plurality of magnetic poles therearound, said apparatus comprising: a control circuit; a current generator comprising a first switching circuit coupled to the control circuit and controlled thereby, the current generator for alternately supplying drive currents to said first and second coils causing the rotor to step, each of said first and second coils generating signals of alternating polarity when transitioning from a driven state to a non-driven state, said signals resulting from motion of said rotor; a rectifying circuit coupled to the control circuit, the rectifying circuit for correcting the polarity of said signals; a blanking circuit for masking an initial portion of each of said signals; an integrator having an input coupled to receive said polarity corrected signals from the rectifying circuit and for generating an integrated version thereof; and a comparator coupled to said integrator for comparing said integrated version with a predetermined threshold to detect the stall condition.