Converter control device and air conditioner including converter control device

#1. Field of the Invention

#The present invention relates to a converter control device that controls a highly-efficient converter installed in an air conditioner and an air conditioner including the converter control device.

#2. Description of the Related Art

#FIG. 1 is a diagram showing a configuration of a converter control device according to a first embodiment of the present invention;

#FIG. 2 is a chart showing a correspondence relationship between a power-source voltage phase and a frequency of a fundamental switching signal in the first embodiment;

#FIG. 3 is an illustration showing a waveform example of a reference voltage Ea, a fundamental switching signal Sc and a PWM signal Sp in the first embodiment;

#FIG. 1 is a diagram showing a system configuration of an air conditioner including a converter control device 10 according to a first embodiment of the present invention. As shown in FIG. 1, a converter main circuit 7 is constructed of a rectifying circuit 2, a reactor 3, a switching unit 4, a smoothing capacitor 5, and a back-flow preventing diode 6. The rectifying circuit 2 has four diodes connected in a bridge configuration for full-wave-rectifying an alternate-current voltage supplied from an alternate-current power source 1. The reactor 3 has a first end and a second end, of which the first end is connected to a positive output side of the rectifying circuit 2, and smoothes a current. The switching unit 4 is connected between the second end of the reactor 3 and a negative output side of the rectifying circuit 2, and performs switching between direct-current bus lines. The smoothing capacitor 5 is connected between the second end of the reactor 3 and the negative output side of the rectifying circuit 2, and smoothes a direct-current bus-line voltage. The back-flow preventing diode 6 is connected between the second end of the reactor 3 and a positive electrode side of the smoothing capacitor 5, and prevents a back flow of the current from the smoothing capacitor 5 to the rectifying circuit 2. A semiconductor switch such as an insulated gate bipolar transistor (IGBT) or a MOSFET is used as the switching unit 4. An output voltage of the alternate-current power source 1 is a sinusoidal-wave signal having a constant frequency.

#An inverter circuit 8 is connected to the smoothing capacitor 5 in parallel and makes rotary drive of the motor 9. Although a compressor driving motor installed in the air conditioner, a fan driving motor installed in an outdoor unit or the like may be used as the motor 9, a compressor driving motor is explained here as the motor 9.

#A configuration of the converter control device 10 that controls the converter main circuit 7 is explained next. A bus-line-voltage detection unit 11 measures a bus line voltage that is a voltage between the terminals of the smoothing capacitor 5, and outputs a bus-line voltage value. A power-source-current detection unit 12 measures a bus line current, and outputs a power-current current amplitude value. The current detection is performed using a shunt resistor, a current transformer, or the like. A voltage-zero-cross detection unit 13 detects a timing at which a phase of a voltage signal of the alternate-current power source 1 is 0 degree, as a voltage zero-cross.