Abstract: An air conditioner is provided that reduces user discomfort due to vibrations and noises at a compressor, piping, and the like such as of an air conditioner. To achieve this, an air conditioner includes: a compressor (10) that has a motor (12) and a compression mechanism (14) driven by the motor (12); a speed detector (43) that detects a rotation speed of the motor (12); a drive mode controller (48) that controls a drive mode of the motor (12); and refrigerant piping that is connected to the compression mechanism (14) and allows a refrigerant to flow therethrough, wherein the drive mode controller (48), for stopping the motor (12), decelerates the motor (12) to a rotation speed equal to or lower than a resonance frequency between the compression mechanism (14) and the refrigerant piping.

Abstract: An air conditioner is provided that reduces user discomfort due to vibrations and noises at a compressor, piping, and the like such as of an air conditioner. To achieve this, an air conditioner includes: a compressor (10) that has a motor (12) and a compression mechanism (14) driven by the motor (12); a speed detector (43) that detects a rotation speed of the motor (12); a drive mode controller (48) that controls a drive mode of the motor (12); and refrigerant piping that is connected to the compression mechanism (14) and allows a refrigerant to flow therethrough, wherein the drive mode controller (48), for stopping the motor (12), decelerates the motor (12) to a rotation speed equal to or lower than a resonance frequency between the compression mechanism (14) and the refrigerant piping.

Abstract: A DC power supply unit is provided that allows for improving efficiency and reducing harmonic currents. A DC power supply unit includes: a bridge rectification circuit having diodes and MOSFETs; a reactor that is arranged between the AC power supply and the bridge rectifier circuit; a smoothing capacitor that is connected to an output side of the bridge rectifier circuit and smoothes a voltage; and a converter control unit that executes, based on predetermined threshold values, a diode rectification control that uses diodes and parasitic diodes of the MOSFETs, a synchronous rectification control that switches the MOSFETs in synchronization with a polarity of the voltage of the AC power supply, a partial switching control that repeats partially short-circuiting the reactor multiple times in a half cycle of the AC power supply, or a fast switching control that short-circuits the reactor at a predetermined frequency over a full AC cycle.

Abstract: A DC power supply unit is provided that allows for improving efficiency and reducing harmonic currents. A DC power supply unit includes: a bridge rectification circuit having diodes and MOSFETs; a reactor that is arranged between the AC power supply and the bridge rectifier circuit; a smoothing capacitor that is connected to an output side of the bridge rectifier circuit and smoothes a voltage; and a converter control unit that executes, based on predetermined threshold values, a diode rectification control that uses diodes and parasitic diodes of the MOSFETs, a synchronous rectification control that switches the MOSFETs in synchronization with a polarity of the voltage of the AC power supply, a partial switching control that repeats partially short-circuiting the reactor multiple times in a half cycle of the AC power supply, or a fast switching control that short-circuits the reactor at a predetermined frequency over a full AC cycle.