Patent ID: 8368332

Claim:
A motor driving circuit comprising: a plurality of output transistors configured to supply driving currents to driving coils of a plurality of phases in a motor; a first comparator circuit configured to compare a voltage of each of the phases of the driving coils of the plurality of phases, with a voltage of a neutral point of the driving coils of the plurality of phases; a position detecting circuit configured to detect a position of a rotor of the motor based on a comparison result obtained by the first comparator circuit; a switching control circuit configured to generate switching signals which are pulse-amplitude-modulated according to the position of the rotor, and to supply the switching signals to the plurality of output transistors; and a current limiting circuit configured to determine whether or not the motor is rotating at a speed higher than or equal to a predetermined reference rotation speed based on a position of the rotor, the predetermined reference rotation speed being lower than or equal to a target rotation speed, limit the driving currents to a first current value so that the motor rotates at the target rotation speed when the current limiting circuit determines that the motor is rotating at a speed higher than or equal to the predetermined reference rotation speed, and limit the driving currents to a second current value smaller than the first current value when the current limiting circuit determines that the motor is not rotating at the speed higher than or equal to the predetermined reference rotation speed.