Patent attributes
A step motor drive circuit has a first transistor pair having first and transistors, a second transistor pair having third and fourth transistors, and fifth and sixth transistors connected in parallel with the first and third transistors, respectively. A driving circuit alternately drives the first transistor pair and the second transistor pair to an ON state in a state of rotating the motor (first stated), and shortcircuits drive terminals of the motor by driving the first and third transistors to an ON state and driving the second and the fourth transistors to an OFF state in a state of braking the motor (second state). The driving circuit drives the fifth transistor to an ON state when the first transistor is driven to the ON state in the second state of the motor, drives the sixth transistor to an ON state when the third transistor is driven to the ON state in the first state of the motor, and drives the sixth transistor to an OFF state when the third transistor is driven to an ON state in the second state of the motor. The fifth transistor and the sixth transistor function as protecting transistors that protect the first to fourth transistors by increasing the electrostatic resistance thereof.
