Converter control device and air conditioner including converter control device

• US 8,941,347 B2
• Filed: 03/18/2013
• Issued: 01/27/2015
• Est. Priority Date: 04/12/2012
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Saito, Katsuhiko, Fukuda, Masahiro, Otorii, Yu
• Primary Examiner(s): Ip, Paul
• Application Number:
  US13/845,286
• Publication Number:
  US 20140225553A1
• Time in Patent Office: 680 Days
• Field of Search: 318/139, 318/722, 318/400.13, 318/400.3, 363/34, 363/40, 363/89
• US Class Current: 318/722
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A converter control device comprises: a voltage-zero-cross detection unit detecting zero cross of the alternate-current voltage and outputting a voltage zero-cross signal; a power-source-current detection unit detecting a power source current of the alternate-current power source; a bus-line-voltage detection unit detecting a bus-line voltage between terminals of the smoothing capacitor; a PWM-signal generation unit generating a PWM-signal for on/off-controlling the switching unit, based on the power-source current, the bus-line voltage and a bus-line-voltage command value as a target voltage of the bus-line voltage; a power-source voltage-state detection unit detecting a signal state of the alternate-current voltage based on the voltage zero-cross signal; and a fundamental-switching-frequency selection unit selecting a fundamental switching frequency of the PWM-signal based on the signal state of the alternate-current voltage. The PWM-signal generation unit generates the PWM-signal based on a fundamental switching signal having a fundamental switching frequency selected by the fundamental-switching-frequency selection unit.

Claims

1. A converter control device controlling a converter main circuit that includes:

a rectifying circuit that rectifies an alternate-current voltage from an alternate-current power source and outputs a direct-current voltage between direct-current bus lines;

a smoothing capacitor that smoothes the direct-current voltage;

a switching unit that is made from a semiconductor element and provided between the direct-current bus lines on a side closer to the power source than the smoothing capacitor;

a reactor that is provided in the direct-current bus line on a side closer to the power source than the switching unit; and

a back-flow preventing diode that is provided in the direct-current bus line between the smoothing capacitor and the switching unit, and prevents a back flow from the smoothing capacitor to a side of the power source,

the converter control device comprising;

a voltage-zero-cross detection unit that detects a zero cross of the alternate-current voltage and outputs a voltage zero-cross signal;

a power-source-current detection unit that detects a power source current of the alternate-current power source;

a bus-line-voltage detection unit that detects a bus line voltage that is a voltage between terminals of the smoothing capacitor;

a pulse width modulation (PWM) signal generation unit that generates a PWM signal for on/off controlling the switching unit, based on the power source current, the bus line voltage and a bus-line-voltage command value that is a target voltage of the bus line voltage;

a power-source voltage-state detection unit that detects a signal state of the alternate-current voltage based on the voltage zero-cross signal; and

a fundamental-switching-frequency selection unit that selects a fundamental switching frequency of the PWM signal based on the signal state of the alternate-current voltage,

wherein the PWM signal generation unit generates the PWM signal based on a fundamental switching signal having a fundamental switching frequency selected by the fundamental-switching-frequency selection unit.

2. The converter control device according to claim 1, wherein

the power-source voltage-state detection unit calculates a voltage phase of the alternate-current power source based on the voltage zero-cross signal, as the signal state of the alternate-current voltage, and

the fundamental-switching-frequency selection unit selects a fundamental switching frequency of the PWM signal based on the voltage phase.

3. The converter control device according to claim 1, wherein

the power-source voltage-state detection unit calculates a voltage cycle number of the alternate-current power source based on the voltage zero-cross signal, as the signal state of the alternate-current voltage, and

the fundamental-switching-frequency selection unit selects a fundamental switching frequency of the PWM signal based on the voltage cycle number.

4. The converter control device according to claim 1, wherein the switching unit is formed by a wide bandgap semiconductor element.

5. The converter control device according to claim 4, wherein a material of the wide bandgap semiconductor element is silicon carbide (SiC), gallium nitride (GaN)-based material, or diamond.

6. An air conditioner comprising:

the converter control device according to claim 1;

a converter main circuit that is controlled by the converter control device; and

an inverter that converts direct-current power outputted from the converter main circuit into alternate-current power to drive a motor.