Motor drive controller and method for detecting rotation state

1. A motor drive controller for controlling a motor having multiple phases, the motor drive controller comprising:

a comparison reference voltage generator that generates a predetermined constant voltage as a comparison reference voltage;

a counter-electromotive voltage comparator that compares the comparison reference voltage with a counter-electromotive voltage of each phase of the motor; and

a rotation state detector that detects a rotation state of the motor based on positive/negative polarities of counter-electromotive voltages of other phases with respect to the comparison reference voltage at the time of an occurrence of a zero cross between the counter-electromotive voltage of any one phase and the comparison reference voltage,

wherein the number of the phase of the motor is three, and

wherein the rotation state detector detects that the motor is in forward rotation at a predetermined speed or higher in a case where, when a zero cross between the rise of the counter-electromotive voltage of any one phase and the comparison reference voltage occurs, the counter-electromotive voltage of another phase leading the phase is positive with respect to the comparison reference voltage, and the counter-electromotive voltage of another phase retarding the phase is negative with respect to the comparison reference voltage.

2. The motor drive controller according to claim 1 ,

wherein the comparison reference voltage generator sets the comparison reference voltage based on an amplitude of the counter-electromotive voltage generated in each phase when the motor rotates at a predetermined speed.

3. A method for detecting rotation state of a three-phase motor, the method comprising:

generating a predetermined constant voltage as a comparison reference voltage;

comparing the comparison reference voltage with a counter-electromotive voltage of each phase of the motor;

detecting a rotation state of the motor based on positive/negative polarities of the counter-electromotive voltages of the other phases with respect to the comparison reference voltage at the time of an occurrence of a zero cross between the counter-electromotive voltage of any one phase and the comparison reference voltage; and

detecting that the motor is in forward rotation at a predetermined speed or higher in a case where, when a zero cross between the rise of the counter-electromotive voltage of any one phase and the comparison reference voltage occurs, the counter-electromotive voltage of another phase leading the phase is positive with respect to the comparison reference voltage, and the counter-electromotive voltage of another phase retarding the phase is negative with respect to the comparison reference voltage.

4. A method for detecting rotation state of a three-phase motor, the method comprising:

generating a predetermined constant voltage as a comparison reference voltage;

comparing the comparison reference voltage with a counter-electromotive voltage of each phase of the motor;

detecting a rotation state of the motor based on positive/negative polarities of the counter-electromotive voltages of the other phases with respect to the comparison reference voltage at the time of an occurrence of a zero cross between the counter-electromotive voltage of any one phase and the comparison reference voltage; and

detecting that a rotation speed of the motor is less than a predetermined speed in a case where, when a zero cross between the rise of the counter-electromotive voltage of any one phase and the comparison reference voltage occurs, both the counter-electromotive voltage of another phase leading the phase and the counter-electromotive voltage of another phase retarding the phase have a same sign with respect to the comparison reference voltage.

5. A motor drive controller for controlling a motor having multiple phases, the motor drive controller comprising:

a comparison reference voltage generator that generates a predetermined constant voltage as a comparison reference voltage;

a counter-electromotive voltage comparator that compares the comparison reference voltage with a counter-electromotive voltage of each phase of the motor; and

a rotation state detector that detects a rotation state of the motor based on positive/negative polarities of counter-electromotive voltages of other phases with respect to the comparison reference voltage at the time of an occurrence of a zero cross between the counter-electromotive voltage of any one phase and the comparison reference voltage,

wherein the number of the phase of the motor is three, and

wherein the rotation state detector detects that a rotation speed of the motor is less than a predetermined speed in a case where, when a zero cross between the rise of the counter-electromotive voltage of any one phase and the comparison reference voltage occurs, both the counter-electromotive voltage of another phase leading the phase and the counter-electromotive voltage of another phase retarding the phase have a same sign with respect to the comparison reference voltage.

6. The motor drive controller according to claim 5 ,

wherein the comparison reference voltage generator sets the comparison reference voltage based on an amplitude of the counter-electromotive voltage generated in each phase when the motor rotates at a predetermined speed.