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

A motor drive control device comprising:

• a control circuit configured to generate a drive control signal being a PWM signal for driving a motor including a coil of at least one phase;
• and
• a drive circuit including a high side switch and a low side switch, the high side switch and the low side switch being connected in series to each other and provided to correspond to the coil of each phase of the motor, the drive circuit being configured to alternately turn on and off the high side switch and the low side switch according to the drive control signal to switch an energizing direction of the coil of the corresponding phase, wherein
• the control circuit includes
• a target point determination unit configured to determine a target point of zero crossing of a coil current of a predetermined phase based on a position detection signal synchronized with an induced voltage of the coil of the predetermined phase of the motor and corresponding to a rotational position of a rotor of the motor,
• a current zero crossing point estimation unit configured to estimate a zero crossing point of the coil current of the predetermined phase by detecting a change in a current direction of the coil current of the predetermined phase at a predetermined timing in every cycle of the PWM signal,
• an adjustment instruction signal generation unit configured to generate at least one of a phase adjustment instruction signal for instructing phase adjustment of the coil current and a frequency adjustment instruction signal for instructing frequency adjustment of the PWM signal according to a phase difference between the target point determined by the target point determination unit and the zero crossing point estimated by the current zero crossing point estimation unit such that the phase difference is within a predetermined range, and
• a drive control signal generation unit configured to generate the drive control signal based on at least one of the phase adjustment instruction signal and the frequency adjustment instruction signal generated by the adjustment instruction signal generation unit.