초록 ▼

A converter circuit for converting an output voltage from an AC power supply includes a rectifier circuit for rectifying the output voltage of the AC power supply; first and second capacitors connected in series, for smoothing the output of the rectifier circuit; and a switch circuit for switching t

A converter circuit for converting an output voltage from an AC power supply includes a rectifier circuit for rectifying the output voltage of the AC power supply; first and second capacitors connected in series, for smoothing the output of the rectifier circuit; and a switch circuit for switching the connections between the respective capacitors and the AC power supply so that the output voltage of the AC power supply is applied to each of the respective capacitors at a cycle that is shorter than the cycle of the AC power supply.

대표청구항 ▼

What is claimed is: 1. A motor driving apparatus receiving an output voltage of an AC power supply, converting the output voltage of the AC power supply into a driving voltage, and outputting the driving voltage to a motor, said apparatus comprising: a converter circuit having a pair of input termi

What is claimed is: 1. A motor driving apparatus receiving an output voltage of an AC power supply, converting the output voltage of the AC power supply into a driving voltage, and outputting the driving voltage to a motor, said apparatus comprising: a converter circuit having a pair of input terminals and a pair of output terminals, and boosting the output voltage of the AC power supply; an inverter circuit for converting an output voltage of the converter circuit into a three-phase AC voltage, and outputting the three-phase AC voltage as a driving voltage to the motor; and said converter circuit comprising a rectifier circuit for rectifying the output voltage of the AC power supply, which is applied to the input terminals, and outputting the rectified voltage to the output terminals, plural capacitors connected in series between the output terminals, and a switch circuit for switching the connections between the respective capacitors and the AC power supply so that the output voltage of the AC power supply is applied to each of the plural capacitors at a cycle shorter than the cycle of the AC power supply; wherein said plural capacitors are first and second capacitors connected in series; and said switch circuit comprises first and second switching elements connected in series, first and second diodes connected in series, which are connected in parallel to the switching elements connected in series, third and fourth diodes connected in series, which are connected in parallel to the switching elements connected in series, a connection node of the first and second diodes being connected to one of the input terminals, a connection node of the third and fourth diodes being connected to the other input terminal, and a connection node of the both switching elements being connected to a connection node of the both capacitors. 2. A motor driving apparatus as defined in claim 1 wherein said switch circuit repeatedly turns on and off the first and second switching elements alternately so that the first and second capacitors are alternately charged, and the capacitances of the first and second capacitors are set to such large values that the terminal voltages of the first and second capacitors do not drop to zero during one switching period of the switching elements when the motor is at the maximum output. 3. A motor driving apparatus as defined in claim 1 wherein said switch circuit repeatedly turns on and off the first and second switching elements alternately so that the first and second capacitors are alternately charged; and the switching cycle of the switching elements is set to such a short period that the terminal voltages of the first and second capacitors do not drop to zero when the motor is at the maximum output. 4. A motor driving apparatus as defined in claim 1 wherein said switch circuit stops the on-off operations of the first and second switching elements when the torque of the motor satisfies a required torque. 5. A motor driving apparatus as defined in claim 4 wherein said switch circuit judges whether the torque of the motor is excessive or deficient, on the basis of the voltage supplied to the motor. 6. A motor driving apparatus as defined in claim 4 wherein said switch circuit judges whether the torque of the motor is excessive or deficient, on the basis of an ordered rpm and an actual rpm of the motor. 7. A motor driving apparatus as defined in claim 4 wherein said switch circuit judges whether the torque of the motor is excessive or deficient, on the basis of the amplitude of a current supplied to the motor. 8. A motor driving apparatus as defined in claim 1 wherein said switch circuit uses a power supply for driving the inverter circuit, as a power supply for driving the first and second switching elements. 9. A motor driving apparatus as defined in claim 8 wherein a power supply for driving a lower-potential-side element between the first and second switching elements comprises a DC power supply for driving the inverter, a diode having an anode connected to a higher-potential-side terminal of the DC power supply, and a capacitor connected between a cathode of the diode and a lower-potential end of the lower-potential-side switching element; and a power supply for driving a higher-potential-side element between the first and second switching elements comprises a diode having an anode connected to the cathode of the diode which is a component of the driving power supply for driving the lower-potential-side element, and a capacitor connected between a cathode of the diode and a connection node of the two switching elements. 10. A motor driving apparatus as defined in claim 1 wherein said switch circuit changes the switching cycle for turning on and off the first and second switching elements, according to the output of the motor. 11. A motor driving apparatus as defined in claim 1 wherein the switching cycle for turning on and off the first and second switching elements is equal to the switching cycle for turning on and off the switching elements which are components of the inverter circuit. 12. A motor driving apparatus as defined in claim 1 wherein said switch circuit turns on and off the first and second switching elements so that harmonic components of the current inputted to the converter circuit are decreased. 13. A motor driving apparatus as defined in claim 1 wherein the diodes as components of the rectifier circuit have an inverse recovery time as short as that of the diodes constituting the switch circuit. 14. A motor driving apparatus as defined in claim 1 wherein said converter circuit includes a capacitor for charging a regenerative current that occurs when the motor is stopped, said capacitor being connected to the output end of the converter circuit. 15. A motor driving apparatus as defined in claim 1 wherein said switch circuit is a switching module which is obtained by modularizing the first to fourth diodes, and the first and second switching elements. 16. A motor driving apparatus as defined in claim 15 wherein said switching module is operated with a driving signal that is supplied from an inverter drive unit for driving the inverter circuit. 17. A motor driving apparatus as defined in claim 1 wherein said converter circuit includes a reactor for cuffing off noises that occur in the switch circuit included in the converter circuit, said reactor being connected to the input end of the converter circuit. 18. A motor driving apparatus as defined in claim 17 wherein said switch circuit turns on and off the first and second switching elements so that the on periods of the both elements are overlapped, thereby to boost the output voltage of the converter circuit to a double or more of the output voltage of the AC power supply. 19. A motor driving apparatus as defined in claim 1 wherein said inverter circuit controls a supply current to the motor so as to increase the power factor of the current inputted to the converter circuit. 20. A motor driving apparatus as defined in claim 1 wherein said switch circuit turns on and off the first and second switching elements so as to increase the power factor of the current inputted to the converter circuit. 21. A compressor receiving a voltage from an AC power supply, comprising: a motor; a motor driving apparatus for driving the motor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 22. An air conditioner receiving a voltage from an AC power supply, and having a compressor, comprising: a motor driving apparatus for driving a motor of the compressor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 23. A refrigerator receiving a voltage from an AC power supply, and having a compressor, comprising: a motor driving apparatus for driving a motor of the compressor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 24. An electric washing machine receiving a voltage from an AC power supply, comprising: a motor; a motor driving apparatus for driving a motor of the compressor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 25. An air blower receiving a voltage from an AC power supply, comprising: a motor; a motor driving apparatus for driving the motor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 26. An electric vacuum cleaner receiving a voltage from an AC power supply, comprising: a motor; a motor driving apparatus for driving the motor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 27. A heat-pump type hot-water supply unit receiving a voltage from an AC power supply, and having a compressor, comprising: a motor driving apparatus for driving a motor of the compressor; and said motor driving apparatus being a motor driving apparatus as defined in claim 1. 28. A motor driving apparatus receiving an output voltage of an AC power supply, converting the output voltage of the AC power supply into a driving voltage, and outputting the driving voltage to a motor, said apparatus comprising: a converter circuit having a pair of input terminals and a pair of output terminals, and boosting the output voltage of the AC power supply; an inverter circuit for converting an output voltage of the converter circuit into a three-phase AC voltage, and outputting the three-phase AC voltage as a driving voltage to the motor; and said converter circuit comprising a rectifier circuit for rectifying an output voltage of an AC power supply, which is applied to the input terminals, and outputting the rectified voltage to the output terminals; a first capacitor connected between the output terminals; a second capacitor having an end connected to one of the output terminals; and a switch circuit for switching the connections between the following connections: the other end of the second capacitor to the one input terminal; and the other end of the second capacitor to the other input terminal, so that the output voltage of the AC power supply is applied to the second capacitor, while a sum voltage of the terminal voltage of the second capacitor and the output voltage of the AC power supply is applied to the first capacitor, at a cycle shorter than the cycle of the AC power supply; and said switch circuit comprising: first and second switching elements connected in series, first and second diodes connected in series, which are connected in parallel to the switching elements connected in series, third and fourth diodes connected in series, which are connected in parallel to the switching elements connected in series, a connection node of the first and second diodes being connected to one of the input terminals, a connection node of the third and fourth diodes being connected to the other input terminal, and a connection node of the both switching elements being connected to the other end of the second capacitor.