Patent ID: 8618763

Claim:
A motor drive circuit comprising: a drive voltage generation circuit generating a drive voltage corresponding to a target rotation speed of a motor, the driving voltage being continuous between a predetermined minimum voltage and a predetermined maximum voltage; a first pulse generation circuit generating a first pulse signal having a first logic level and a second logic level, a duty ratio of the first logic level of the first pulse signal continuously increasing as the drive voltage increases; a second pulse generation circuit generating a second pulse signal having the first logic level and the second logic level, a duty ratio of the first logic level of the second pulse signal being different from the duty ratio of the first pulse signal; and a drive control circuit supplying a drive current to a coil of the motor at the duty ratio of the second pulse signal so as to start a rotation of the motor that is not rotating and supplying a drive current to the coil at the duty ratio of the first pulse signal after a predetermined time from the start of the rotation of the motor in response to a rotation signal corresponding to the rotation of the motor, wherein the first and second pulse generation circuits are connected between the drive voltage generation circuit and the drive control circuit so that the first and second pulse generation circuits receive the drive voltage generated by the drive voltage generation circuit.