Patent ID: 8148933

Claim:
A circuit arrangement for automatic, load-dependent control of at least one winding current of a respective motor winding of a self-timed bipolar stepper motor, the circuit arrangement comprising: a first power driver circuit for a first motor winding and a second power driver circuit for a second motor winding, each power driver circuit having a respective comparator input configured to control a predetermined current amplitude in the respective motor winding; a first XOR gate having a first encoder signal and a first phase signal as inputs, the first phase signal being derived from first encoder signal and configured to control a current direction in the first motor winding; a second XOR gate having a second encoder signal and a second phase signal as inputs, the second phase signal being derived from the second encoder signal and configured to control a current direction in the second motor winding; a first resistor connected so as to couple an output of the first XOR gate to an anode of a first diode, a cathode of the first diode being coupled to the comparator input of the first power driver circuit via a second resistor; and a third resistor connected so as to couple an output of the second XOR gate to an anode of a second diode, a cathode of the second diode being coupled to the current-controlling comparator input of the second power driver circuit via a fourth resistor, wherein a first current path defined by at least a first pull-up resistor, the first resistor, the first diode, and the second resistor is configured so that a logic high at the output of the first XOR gate sets the comparator input of the first power driver circuit at a level configured to prevent current from being supplied to the first motor winding through the first power driver circuit.