Motor drive device and method for driving motor

A motor drive device that drives a motor to rotate comprising:

• at least one processor or one circuitry which functions as:
• a detecting unit configured to detect a rotational position of a rotor;
• a generating unit configured to generate a drive waveform to be output to the motor;
• a control unit configured to perform control that synchronizes a phase of the rotational position and a phase of the drive waveform;
• and
• a phase difference setting unit configured to set a phase difference between the rotational position and the drive waveform in a state in which the phase of the rotational position and the phase of the drive waveform are synchronized,
• wherein the detecting unit comprises:
• a first calculating unit configured to calculate a first count values based on a plurality of signals that change with the rotation of the rotor;
• a second calculating unit configured to acquire the first count values and calculate a second count values having a first upper limit value;
• and
• a third calculating unit configured to acquire the second count values, perform a process that multiplies the second count values by a conversion ratio that has been set, and calculate a third count values having a second upper limit value.