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A motor driving apparatus includes an inverter circuit for converting an output of a rectifier circuit connected to a single-phase AC power supply into a driving voltage, and outputting the driving voltage to a brushless motor, and an inverter control unit for controlling the amplitude value of the

A motor driving apparatus includes an inverter circuit for converting an output of a rectifier circuit connected to a single-phase AC power supply into a driving voltage, and outputting the driving voltage to a brushless motor, and an inverter control unit for controlling the amplitude value of the voltage outputted from the inverter to the brushless motor so as to minimize a difference between a command rpm indicated by an external command signal and an actual rpm derived from an estimated phase of the rotor, wherein the command rpm is set to an rpm outside a predetermined range of rpms.

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What is claimed is: 1. A motor driving apparatus for driving a brushless motor on a basis of a command revolution speed of the brushless motor, said motor driving apparatus comprising: an inverter circuit operable to convert an output voltage of a DC power supply into a driving voltage, and to outp

What is claimed is: 1. A motor driving apparatus for driving a brushless motor on a basis of a command revolution speed of the brushless motor, said motor driving apparatus comprising: an inverter circuit operable to convert an output voltage of a DC power supply into a driving voltage, and to output the driving voltage to the brushless motor; and a control unit operable to control said inverter circuit so that an actual revolution speed of the brushless motor reaches the command revolution speed, wherein said control unit controls said inverter circuit so as to vary the actual revolution speed of the brushless motor immediately when the actual revolution speed reaches the command revolution speed, in a state where the command revolution speed of the brushless motor is equal to a specific revolution speed that is determined according to a variable frequency of a voltage output from the DC power supply. 2. A motor driving apparatus as defined in claim 1, wherein the specific frequency includes a frequency that is an integral multiple of the variable frequency of the voltage output from the DC power supply and its vicinity. 3. A motor driving apparatus as defined in claim 1, wherein the brushless motor is a three-phase brushless motor; and wherein the specific frequency is an integral multiple of a frequency that is obtained by multiplying the variable frequency of the voltage output from the DC power supply by ⅙. 4. A motor driving apparatus for driving a brushless motor on a basis of a first command revolution speed of the brushless motor, said motor driving apparatus comprising: an inverter circuit operable to convert an output voltage of a DC power supply into a driving voltage, and to output the driving voltage to the brushless motor; a command revolution speed conversion unit operable to convert the first command revolution speed into a second command revolution speed that continuously varies with the first command revolution speed as its center; and a control unit operable to vary a duty ratio of a control signal which is input to said inverter circuit so that an actual revolution speed of the brushless motor reaches the second command revolution speed. 5. A motor driving apparatus as defined in claim 4, wherein the frequency of the output current of said inverter circuit varies at random. 6. A motor driving apparatus as defined in claim 1, wherein said DC power supply comprises a single-phase AC power supply and a rectifier circuit having an input connected to the single-phase AC power supply; and wherein a capacitor for charging a regenerative current from the brushless motor is connected to an upstream side of said inverter circuit. 7. A motor driving apparatus as defined in claim 1, wherein said DC power supply comprises a single-phase AC power supply and a rectifier circuit having an input connected to the single-phase AC power supply; and wherein an inductor for cutting noise that occurs in said inverter circuit is connected between said inverter circuit and the DC power supply. 8. A motor driving apparatus as defined in claim 1, wherein said DC power supply comprises a three-phase AC power supply and a three-phase rectifier circuit having an input connected to the three-phase AC power supply; and wherein said inverter circuit converts an output voltage of the three-phase rectifier circuit into a driving voltage, and outputs the driving voltage to the brushless motor. 9. A motor driving apparatus for driving a brushless motor on a basis of a command revolution speed of the brushless motor, said motor driving apparatus comprising: a cycloconverter circuit operable to convert an output voltage of a single-phase AC power supply into a driving voltage, and to output the driving voltage to the brushless motor; and a control unit operable to control said cycloconverter circuit so that an actual revolution speed of the brushless motor reaches the command revolution speed, wherein said control unit controls said cycloconverter circuit so as to vary the actual revolution speed of the brushless motor immediately when the actual revolution speed reaches the command revolution speed, in a state where the command revolution speed of the brushless motor is equal to a specific revolution speed that is determined according to a frequency of a voltage output from the single-phase AC power supply. 10. A compressor having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 11. An air conditioner having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 12. A refrigerator having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 13. An electric washing machine having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 14. An air blower having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 15. An electric vacuum cleaner having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 16. An electric dryer having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 17. A heat pump type hot-water supply unit having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 1. 18. A motor driving apparatus as defined in claim 4, wherein said DC power supply comprises a single-phase AC power supply and a rectifier circuit having an input connected to the single-phase AC power supply; and wherein a capacitor for charging a regenerative current from the brushless motor is connected to an upstream side of said inverter circuit. 19. A motor driving apparatus as defined in claim 4, wherein said DC power supply comprises a single-phase AC power supply and a rectifier circuit having an input connected to the single-phase AC power supply; and wherein an inductor for cutting noise that occurs in said inverter circuit is connected between said inverter circuit and the DC power supply. 20. A motor driving apparatus as defined in claim 4, wherein the DC power supply comprises a three-phase AC power supply and a three-phase rectifier circuit having an input connected to the three-phase AC power supply; and wherein said inverter circuit converts an output voltage of the three-phase rectifier circuit into a driving voltage, and outputs the driving voltage to the brushless motor. 21. A motor driving apparatus for driving a brushless motor on a basis of a first command revolution speed of the brushless motor, said motor driving apparatus comprising: a cycloconverter circuit operable to convert an output voltage of a single-phase AC power supply into a driving voltage, and to output the driving voltage to the brushless motor; a command revolution speed conversion unit operable to convert the first command revolution speed into a second command revolution speed that continuously varies with the first command revolution speed as its center; and a control unit operable to vary a duty ratio of a control signal which is input to said cycloconverter circuit so that an actual revolution speed of the brushless motor reaches the second command revolution speed. 22. A compressor having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 23. An air conditioner having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 24. A refrigerator having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 25. An electric washing machine having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 26. An air blower having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 27. An electric vacuum cleaner having a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 28. An electric dryer having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4. 29. A heat pump type hot-water supply unit having a compressor including a brushless motor, and a motor driving apparatus for driving the brushless motor, said motor driving apparatus being a motor driving apparatus as defined in claim 4.