Motor driving device and motor system

A motor system comprising:

• a disk to store data;
• a motor to rotate the disk;
• and
• a motor driving device to drive the motor with three-phase sine waves,
• wherein the motor driving device comprises:
• an inverter which includes a plurality of high-side transistors and low-side transistors respectively coupled to a driving terminal of three phases of the motor and which applies a drive voltage to the motor based on a PWM signal;
• a back EMF (electromotive force) phase detector which detects a reference voltage phase used as a phase of a back electromotive force of the motor;
• a drive current phase detector which detects a reference current phase used as a phase of a drive current of the motor;
• a PWM controller which receives an energization control timing synchronized with the reference voltage phase and generates the PWM signal to control the drive voltage to a sine wave shape;
• and
• a drive voltage phase generator which determines a first phase used as the phase of the drive voltage necessary to set the phase difference between the reference voltage phase and the reference current phase to a prescribed value, and which directs the PWM controller to shift the energization control timing based on the first phase,
• wherein the drive voltage phase generator comprises:
• a phase arithmetic unit which calculates a second phase used as a phase of the drive voltage to reduce the phase difference between the reference voltage phase and the reference current phase to zero substantially, based on an arithmetic expression using a current value of the drive current, an angular frequency of the motor, and a predetermined characteristic constant of the motor;
• and
• a phase correction unit which determines the first phase by adding a correction value to the second phase, and which inputs the reference voltage phase and the reference current phase to update the magnitude of the correction value by a feedback control so as to converge the phase difference between the reference voltage phase and the reference current phase to the prescribed value.