Patent ID: 6914407

Claim:
A step motor control device for controlling operation of a step motor, the step motor control device comprising: first and second switch elements connected to each other in series; third and fourth switch elements connected to each other in series; a coil of a step motor, the coil being connected between a connection point of the first and second switch elements and a connection point of the third and fourth switch elements; a first series circuit having a first detection element and a fifth switch element connected in parallel with the first switch element; a second series circuit having a second detection element and a sixth switch element connected in parallel with the third switch element; a control means for controlling an on/off operation of the first to fourth switch elements in response to a supplied drive pulse to allow a current to flow in the coil to rotationally drive the step motor, and for controlling an on/off operation of the first, third, fifth and sixth switch elements in response to a rotation detection control pulse supplied during a rotation detection period immediately after the rotational drive of the step motor in accordance with the supplied drive pulse is completed; and detecting means for detecting the presence/absence of the rotation of the step motor in accordance with a comparison result obtained by comparing a threshold voltage with a voltage generated between the coil and the first detection element of the first series circuit and with a voltage generated between the coil and the second detection element of the second series circuit, wherein the control means controls the on/off operation of the third switch element at a given frequency after a given period has elapsed in a state where the fourth and fifth switch elements are turned on, or controls the on/off operation of the first switch element at a given frequency after a given period has elapsed in a state where the third and sixth switch elements are turned on; and wherein the detecting means detects the presence/absence of the rotation of the step motor when the control means controls the on/off operation of the third switch element or the fourth switch element at a given frequency.