Motor drive control device, motor unit, and motor drive control method

A motor drive control method for controlling a drive of a motor by a motor drive control device, the method comprising:

• a first step of setting, by the motor drive control device, as a commutation mode, either
• a first commutation mode for commutating a coil according to a detection result of a zero crossing of a back electromotive voltage of the coil of a motor, based on a rotation speed of the motor, or
• a second commutation mode for commutating the coil according to a target energization period;
• a second step of generating, by the motor drive control device, a drive control signal configured to control a drive of the motor;
• a third step of setting, by the motor drive control device, a current limit value as a reference for limiting a current flowing through the coil;
• and
• a fourth step of generating, by the motor drive control device, the drive control signal configured to stop excitation of the coil when the current flowing through the coil reaches the current limit value, wherein
• the third step includes
• a fifth step of setting, by the motor drive control device, the current limit value to a first value during a period with the commutation mode being the first commutation mode, and
• a sixth step of setting, by the motor drive control device, the current limit value to a second value smaller than the first value during at least a part of the period in the second commutation mode.