Patent ID: 8836269

Claim:
A method for detecting blockages of unipolar stepper motors having one or more motor windings by analyzing the motor current supply, comprising the following method steps: impressing an operating current according to a current supply variant for the operation of the unipolar stepper motor into the one or more motor windings thereof by means of one controllable switch per motor winding connection, wherein the switch selectively connects the respective motor winding connection to a first supply voltage connection and wherein the connections of each motor winding lying at a common potential are permanently connected to a second supply voltage connection, wherein the current supply variant has phases between the switching of the motor windings, in which phases the motor winding connections of a motor winding connected to the switches are switched to high impedance, detecting the voltage at a motor winding connection switched to high impedance at least for the high-impedance phase and comparing said voltage to a threshold that is at least 1.5 times the supply voltage, detecting a time interval during which the voltage at the motor winding connection switched to high impedance is larger than the threshold, comparing the lengths of the intervals for a plurality of motor winding connections each switched to high impedance, and detecting a blockage based on the comparisons of the lengths of the intervals.