Patent ID: 8310188

Claim:
A motor drive circuit comprising: an H-bridge circuit connected to a coil of a motor that is to be driven; a comparator which receives a Hall signal indicating position information of a rotor of the motor and converts the Hall signal into a rectangular signal; a pulse modulator which generates a pulse-modulated pulse signal specifying energization time of the coil of the motor; and a pre-driver which drives the H-bridge circuit based on the pulse signal and the rectangular signal; wherein: the pulse modulator is configured to enable switching between a first mode in which, after commencing starting of the motor, a duty ratio of the pulse signal is set to 100% and, after that, the duty ratio is switched to a predetermined value in accordance with rotational frequency of the motor; a second mode in which the duty ratio of the pulse signal continues to be set to 100%; and a third mode in which the duty ratio and frequency of the pulse signal are set, based on a control signal of a pulse form inputted from outside.