The control circuit includes a current detecting part detecting a driving current of the motor, a set duty generating part generating a set duty for outputting the driving control signal based on the speed command information and the actual rotational frequency information, a limit value determining part determining a current limit value based on the set duty and an instructed duty corresponding to the speed command information and a limiting part limiting the driving current of the motor based on the driving current of the motor detected by the current detecting part and the current limit value determined by the limit value determining part.