Power conversion device, motor drive device, and refrigeration cycle application equipment

Abstract

A power conversion device (1) is provided with: a single-transistor boost-type AC-DC converter (150) having a rectifier circuit (130) and a single-transistor boost circuit (140); a capacitor (210); an inverter (310); a voltage detection unit (501) that detects a post-rectification voltage downstream of the rectifier circuit (130); a current detection unit (502) that detects a post-rectification current downstream of the rectifier circuit (130); a voltage detection unit (503) that detects a bus voltage upstream of the inverter (310); a current detection unit (504) that detects a current flowing into the inverter (310) upstream of the inverter (310); and a control unit (400) that uses the detected values to control the operation of a switching element (142) provided in the single-transistor boost-type AC-DC converter (150) and a switching element (311) provided in the inverter (310). The reference potential of the voltage detection units (501, 503) and the current detection units (502, 504) is a bus N line (600b).

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device that performs power conversion, a motor drive device, and a refrigeration cycle application device.

[0002] Conventionally, some power conversion devices include an AC (Alternating Current)-DC (Direct Current) converter that converts AC power into DC power, i.e., an AC-DC converter. For example, Patent Document 1 discloses technology for a power conversion device that can reduce losses in a configuration including a single-transistor boost AC-DC converter. The power conversion device described in Patent Document 1 detects input voltage and input current from an AC power source, output voltage and output current from a smoothing capacitor to a DC load, and the like, and uses these detected values ​​to control the operation of switching elements in the AC-DC converter. The detection unit for detecting the detected values ​​can be, for example, an ACCT (Alternating Current Transformer) or a DCCT (Direct Current Transformer).

[0003] Patent No. 7109688

[0004] In general, using resistors as detectors is less expensive than using ACCTs, DCCTs, etc. However, when using resistors, the reference potential of each detector becomes an issue. If the reference potentials of the detectors used to detect each detection value are not uniform, stable control requires the addition of circuits such as differential amplifiers and isolation circuits to align the reference potentials in the control unit that controls the operation of the switching elements of the AC-DC converter. This increases the circuit size and costs, which is a problem.

[0005] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can perform stable control while suppressing an increase in circuit size.

[0006] In order to solve the above-mentioned problems and achieve the object, a power conversion device according to the present disclosure includes a single-transistor boost AC / DC converter having a rectifier circuit that rectifies a first AC voltage supplied from an AC power source and outputs the rectified voltage, and a single-transistor boost circuit that boosts the rectified voltage and outputs a first DC voltage, a capacitor that smoothes the first DC voltage to a second DC voltage, an inverter that converts the second DC voltage to a second AC voltage and outputs the second AC voltage to a load, a first voltage detection unit that is located downstream of the rectifier circuit and outputs a detected value of the rectified voltage, and a first current detection unit that is located downstream of the rectifier circuit and outputs a detected value of the rectified current output from the rectifier circuit. a first voltage detection unit that outputs a detection value of a second DC voltage, which is a bus voltage between the bus P line and the bus N line, in a stage preceding the inverter; a second current detection unit that outputs a detection value of a current flowing into the inverter, which is a current used in a stage preceding the inverter to estimate a current flowing from the inverter to a load; and a control unit that controls the operation of a switching element provided in the single-transistor step-up AC-DC converter and a switching element provided in the inverter using the detection value, and the reference potential of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit is the bus N line.

[0007] The power conversion device according to the present disclosure has an advantage that it is possible to suppress an increase in circuit size while performing stable control.

[0008] FIG. 1 shows an example of the configuration of a power conversion device according to embodiment 1. FIG. 2 shows an example of the low-pass filter connected to the detection resistor provided in the power conversion device according to embodiment 1. FIG. 3 shows an example of the low-pass filter connected to the detection resistor provided in the power conversion device according to embodiment 1. FIG. 4 shows an example of the low-pass filter connected to the detection resistor provided in the power conversion device according to embodiment 1. FIG. 5 shows an example of the hardware configuration for realizing the control unit provided in the power conversion device according to embodiment 1. FIG. 6 shows an example of the configuration of a refrigeration cycle application device according to embodiment 2.

[0009] Hereinafter, a power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] First Embodiment. FIG. 1 is a diagram illustrating an example of the configuration of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to an AC power supply 110 and a motor 314. The power conversion device 1 converts a first AC voltage, a power supply voltage Vs, supplied from the AC power supply 110, such as a commercial power supply, into a second AC voltage having a desired amplitude and phase, and supplies the second AC voltage to the motor 314. In the example of FIG. 1 , the AC power supply 110 is a single-phase AC power supply, but it may also be a three-phase AC power supply. The power conversion device 1 includes a single-transistor step-up AC / DC converter 150, a capacitor 210, an inverter 310, a control unit 400, a DC / DC converter 410, voltage detection units 501 and 503, current detection units 502 and 504, detection resistors 501a, 502a, 503a, and 504a, and voltage-dividing resistors 501b and 503b. The power conversion device 1 and the motor 314 constitute a motor drive device 2.

[0011] The single-transistor step-up AC / DC converter 150 includes a rectifier circuit 130 and a single-transistor step-up circuit 140 .

[0012] The rectifier circuit 130 rectifies the first AC voltage supplied from the AC power supply 110 and outputs the rectified voltage to the single-transistor boost circuit 140. When the AC power supply 110 is a single-phase AC power supply as shown in FIG. 1 , the rectifier circuit 130 is a bridge circuit configured by four rectifier elements 131.

[0013] The single-transistor boost circuit 140 boosts the rectified voltage output from the rectifier circuit 130 and outputs a first DC voltage to the capacitor 210. The single-transistor boost circuit 140 includes a reactor 141, a switching element 142, a freewheeling diode 143, and a diode 144. The switching element 142 is turned on and off under the control of the control unit 400. The switching element 142 is operable under the control of the control unit 400. The switching element 142 may be, for example, an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar transistor, or the like, but is not limited to these. The DC voltage rectified by the rectifier circuit 130, boosted by the single-transistor boost circuit 140, and output to the capacitor 210 is the first DC voltage.

[0014] The capacitor 210 is connected in parallel to the output terminal of the single-transistor boost circuit 140 and smoothes the first DC voltage into a second DC voltage. The capacitor 210 is, for example, an electrolytic capacitor or a film capacitor.

[0015] The inverter 310 is a power converter connected in parallel across the capacitor 210. The inverter 310 includes six switching elements 311 and six freewheeling diodes 312. The control unit 400 controls the switching elements 311 to turn on and off, converting the second DC voltage into a second AC voltage having a desired amplitude and phase, i.e., generating the second AC voltage, and outputting it to the motor 314, which is a load. The switching elements 311 are, for example, but not limited to, IGBTs, MOSFETs, bipolar transistors, etc. The circuit configuration of the inverter 310 is not particularly limited and may be a full-bridge circuit, a single-phase bridge circuit, a half-bridge circuit, etc.

[0016] The voltage detection unit 501 is a first voltage detection unit that detects the rectified voltage at a subsequent stage of the rectifier circuit 130. The voltage detection unit 501 is connected to a detection resistor 501a, and estimates the rectified voltage by measuring the voltage across the detection resistor 501a, which is divided by the detection resistor 501a and the voltage dividing resistor 501b. Although not shown, the voltage detection unit 501 outputs the detected value of the rectified voltage, i.e., the voltage value, to the control unit 400. In the following description, the voltage detection unit 501 may be simply referred to as a detection unit.

[0017] The current detection unit 502 is a first current detection unit that detects the rectified current output from the rectification circuit 130 at a stage subsequent to the rectification circuit 130. The current detection unit 502 is connected to a detection resistor 502a and detects the rectified current by measuring the current flowing through the detection resistor 502a. Although not shown, the current detection unit 502 outputs the detected value of the rectified current, i.e., the current value, to the control unit 400. In the following description, the current detection unit 502 may be simply referred to as a detection unit.

[0018] The voltage detection unit 503 is a second voltage detection unit that detects a second DC voltage, which is a bus voltage between the bus P line 600a and the bus N line 600b, in the upstream stage of the inverter 310. The voltage detection unit 503 is connected to the detection resistor 503a, and estimates the second DC voltage by measuring the voltage across the detection resistor 503a, which is divided by the detection resistor 503a and the voltage dividing resistor 503b. Although not shown in the figure, the voltage detection unit 503 outputs a detected value of the second DC voltage, i.e., a voltage value, to the control unit 400. In the following description, the voltage detection unit 503 may be simply referred to as a detection unit.

[0019] The current detection unit 504 is a second current detection unit that detects the current flowing through the inverter 310, which is used to estimate the current flowing from the inverter 310 to the motor 314, which is a load, in the upstream stage of the inverter 310. The current detection unit 504 is connected to a detection resistor 504a, and detects the current flowing through the inverter 310 by measuring the current flowing through the detection resistor 504a. Although not shown in the figure, the current detection unit 504 outputs the detection value of the current flowing through the inverter 310, i.e., the current value, to the control unit 400. In the following description, the current detection unit 504 may be simply referred to as a detection unit.

[0020] The DC-DC converter 410 generates a power supply voltage for operating the control unit 400. In general, the power supply voltage of the control unit 400 is lower than the drive voltage for driving the switching element 311 of the inverter 310. Therefore, the DC-DC converter 410 steps down the second DC voltage from the capacitor 210 to generate the power supply voltage for the control unit 400.

[0021] The control unit 400 acquires detection values ​​from the voltage detection units 501 and 503 and the current detection units 502 and 504. Using the acquired detection values, the control unit 400 controls the operation of the switching element 142 included in the single-transistor boost circuit 140 of the single-transistor boost type AC-DC converter 150 and the switching element 311 included in the inverter 310. In other words, the control unit 400 performs control calculations to control the on / off of the switching elements 142 and 311.

[0022] Here, the control unit 400 estimates the AC voltage and AC current supplied from the AC power supply 110 based on the detection values ​​of the voltage detection unit 501 and the current detection unit 502. FIG. 2 is a diagram illustrating an example of the AC voltage before rectification by the rectifier circuit 130 and the rectified voltage after rectification of the power conversion device 1 according to the first embodiment. The rectified voltage after rectification by the rectifier circuit 130 has a waveform in which the negative portion is inverted to the positive side compared to the AC voltage before rectification by the rectifier circuit 130. Therefore, the control unit 400 can estimate the waveform shape of the AC voltage before rectification shown in FIG. 2 from the waveform shape of the rectified voltage shown in FIG. 2, except for the phase relationship. Note that although a method for estimating the AC voltage from the rectified voltage has been described above, the control unit 400 can also estimate the AC current before rectification by the rectifier circuit 130 from the rectified current after rectification by the rectifier circuit 130 using a similar method.

[0023] Furthermore, the control unit 400 estimates the current flowing from the inverter 310 to the motor 314 using the current value detected by the current detection unit 504, i.e., the current value flowing through the inverter 310. As described above, the control unit 400 controls the on / off of each switching element 311 of the inverter 310, and therefore knows the on / off timing of each switching element 311 of the inverter 310. Therefore, by using the on / off timing of each switching element 311 and the current value detected by the current detection unit 504, the control unit 400 can estimate how much current is flowing through each phase of the three-phase connecting line connecting the inverter 310 and the motor 314. Since a general method may be used to estimate the current flowing through the motor 314 from the current value detected by the current detection unit 504, a detailed description thereof will be omitted.

[0024] Next, features of the power conversion device 1 according to this embodiment will be described. In this embodiment, the voltage detection unit 501, the current detection unit 502, the voltage detection unit 503, and the current detection unit 504 all share a common reference potential, which is the bus N line 600b. In the example of FIG. 1 , the reference potentials of the detection units are represented by black squares. Because there is no variation in the reference potentials of the voltage detection unit 501, the current detection unit 502, the voltage detection unit 503, and the current detection unit 504, i.e., the respective detection units, and the reference potentials of the respective detection units are uniform, the control unit 400 can utilize the detection values ​​acquired from the respective detection units without using additional circuits, such as a differential amplifier circuit or an isolation circuit, for adjusting the detection values ​​acquired from the respective detection units. This allows the power conversion device 1 to perform stable control while suppressing an increase in circuit size and cost.

[0025] 1, the reference potential of the power supply voltage of the control unit 400 is also the bus N line 600b. As a result, in the power conversion device 1, the reference potential of the power supply voltage of the control unit 400 is aligned with the reference potential of each detection unit, so that a differential amplifier circuit, an insulating circuit, or the like for aligning the reference potential of the power supply voltage of the control unit 400 with the reference potential of each detection unit is not required, and more stable control can be performed.

[0026] Furthermore, the upper limit voltages of the output voltages of voltage detection unit 501, current detection unit 502, voltage detection unit 503, and current detection unit 504 are set to be equal to or lower than the power supply voltage of control unit 400. The output voltages of voltage detection unit 501, current detection unit 502, voltage detection unit 503, and current detection unit 504 are, for example, the output voltages when voltage detection unit 501, current detection unit 502, voltage detection unit 503, and current detection unit 504 output their detection values ​​to control unit 400. This allows power conversion device 1 to avoid a situation in which control unit 400 breaks down due to overvoltage. Furthermore, power conversion device 1 does not require the addition of a voltage range conversion circuit or the like between control unit 400 and each detection unit.

[0027] In the power conversion device 1, a two- or more-stage low-pass filter may be connected to the second end of each detection resistor connected to each detection unit, the second end being opposite the first end connected to the bus N line 600b. Because the connection pattern of the low-pass filters for the detection resistors 501a, 502a, 503a, and 504a is the same, the detection resistor 501a will be described as an example. FIG. 3 is a first diagram illustrating an example of a low-pass filter 550 connected to the detection resistor 501a included in the power conversion device 1 according to the first embodiment. In this manner, the two-stage low-pass filter 550 is connected to the second end of the detection resistor 501a, the second end being opposite the first end connected to the bus N line 600b. In the example of FIG. 3, the low-pass filter 550 is configured with one resistor and one capacitor, but the configuration of the low-pass filter 550 is not limited to the example of FIG. 3. The same applies to the configuration of the low-pass filter 550 shown in the subsequent figures.

[0028] If the reference potential of each detector is set to the bus N line 600b, the influence of parasitic impedance may cause slight differences in potential at certain locations on the bus N line 600b. In such cases, slight differences in potential may be superimposed on the detector as noise. In the power conversion device 1, noise components are high-frequency and can be removed by the low-pass filter 550. However, by increasing the number of stages of the low-pass filter 550 to two or more and increasing the high-order attenuation rate, the influence of noise can be reduced, even when the reference potentials are uniform, enabling appropriate detection of the detected value. Furthermore, by increasing the number of stages of the low-pass filter 550 to two or more and increasing the high-order attenuation rate, the operational stability of the single-transistor boost AC / DC converter 150, the inverter 310, and the like can be improved.

[0029] Furthermore, in the power conversion device 1, among the detection resistors connected to the respective detection units, a single-stage low-pass filter 550 may be connected to the second end of each of the detection resistors connected to the voltage detection unit 501 and the voltage detection unit 503, opposite the first end connected to the bus N line 600b, and a two- or more-stage low-pass filter 550 may be connected to the second end of each of the detection resistors connected to the current detection unit 502 and the current detection unit 504, opposite the first end connected to the bus N line 600b. The connection pattern of the two- or more-stage low-pass filters 550 to the detection resistors 502a and 504a is the same as the connection pattern in FIG. 3 . Since the connection pattern of the low-pass filters 550 to the detection resistors 501a and 503a is the same, the connection pattern of the detection resistor 501a will be described as an example. FIG. 4 is a second diagram showing an example of the low-pass filter 550 connected to the detection resistor 501a included in the power conversion device 1 according to the first embodiment. In this manner, the one-stage low-pass filter 550 is connected to the second end of the detection resistor 501a opposite to the first end connected to the bus N line 600b.

[0030] The reason for the different number of stages of the low-pass filter 550 for the voltage detection units 501 and 503 and the current detection units 502 and 504 is that, generally, voltage detection handles larger voltages and therefore produces less noise, while current detection handles smaller currents and therefore prevents the current from being buried in noise. Furthermore, while both the single-transistor boost AC / DC converter 150 and the inverter 310 require highly accurate control based on the detected current, control based on the detected voltage can be performed with lower accuracy. Therefore, the power conversion device 1 uses a single-stage low-pass filter 550 for the voltage detection units 501 and 503, which require low accuracy, and two or more stages for the current detection units 502 and 504, which require high accuracy. This allows for noise countermeasures and uniform reference potentials for the detection units with minimal increase in cost and circuit size.

[0031] Furthermore, in the power conversion device 1, the filtering process by the second and subsequent low-pass filters 550 of the two- or more-stage low-pass filters 550 may be performed by software processing in the control unit 400. FIG. 5 is a third diagram showing an example of the low-pass filter 550 connected to the detection resistor 501a included in the power conversion device 1 according to the first embodiment. In this manner, the power conversion device 1 may have the low-pass filter 550 connected to the detection resistor 501a and the control unit 400 connected as a subsequent stage of the low-pass filter 550. Note that the example in FIG. 5 shows an example in which the control unit 400 performs filtering processing by software processing, but this is not limiting. In the power conversion device 1, a configuration that performs arithmetic processing other than the control unit 400 may perform filtering processing by software processing.

[0032] If the power conversion device 1 can implement the low-pass filter 550 through software processing in the control unit 400, the number of circuit components can be reduced by the amount of the implemented low-pass filter 550, which can contribute to reducing the circuit size and costs.

[0033] Here, on a board on which the voltage detection unit 501, the current detection unit 502, the voltage detection unit 503, the current detection unit 504, etc. are mounted, wiring on the reference potential side of the voltage detection unit 501, the current detection unit 502, the voltage detection unit 503, and the current detection unit 504 is connected to a single-point ground. Fig. 6 is a diagram showing a portion of a pattern layout when each component of the power conversion device 1 according to the first embodiment is mounted on a board. Fig. 6 simplifies the illustration, but shows a state in which a wiring 610b of the bus N line 600b is connected at a single point to a wiring 601 connected to a first end of a detection resistor 501a connected to the voltage detection unit 501, a wiring 602 connected to a first end of a detection resistor 502a connected to the current detection unit 502, a wiring 603 connected to a first end of a detection resistor 503a connected to the voltage detection unit 503, and a wiring 604 connected to a first end of a detection resistor 504a connected to the current detection unit 504.

[0034] By connecting the wiring 610b of the bus N line 600b to the wirings 601, 602, 603, and 604 at a single point, the power conversion device 1 can eliminate the common impedance that exists in common for multiple detection units, allowing each detection unit to operate without being affected by the operation of others, and enabling operation with reduced noise.

[0035] Next, a description will be given of the hardware configuration of the control unit 400 included in the power conversion device 1. Fig. 7 is a diagram showing an example of a hardware configuration that realizes the control unit 400 included in the power conversion device 1 according to embodiment 1. The control unit 400 is realized by a processor 91 and a memory 92.

[0036] The processor 91 is a CPU (Central Processing Unit, also called a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Examples of memory 92 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). Memory 92 is not limited to these, and may also be a magnetic disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0037] As described above, according to this embodiment, the reference potential of the voltage detection unit 501, the current detection unit 502, the voltage detection unit 503, and the current detection unit 504 is all common to the bus N line 600b in the power conversion device 1. This enables the power conversion device 1 to perform stable control while suppressing an increase in circuit size and also suppressing an increase in costs.

[0038] Second Embodiment Fig. 8 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to a second embodiment. The refrigeration cycle-applied device 900 according to the second embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied device 900 according to the second embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 8, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0039] The refrigeration cycle application equipment 900 includes a compressor 315 incorporating the motor 314 in embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0040] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant and a motor 314 that operates the compression mechanism 904 are provided.

[0041] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is variably controlled in speed.

[0042] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 904.

[0043] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0044] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0045] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0046] REFERENCE SIGNS LIST 1 Power conversion device, 2 Motor drive device, 91 Processor, 92 Memory, 110 AC power supply, 130 Rectifier circuit, 131 Rectifier element, 140 Single-transistor boost circuit, 141 Reactor, 142, 311 Switching element, 143, 312 Freewheel diode, 144 Diode, 150 Single-transistor boost AC / DC converter, 210 Capacitor, 310 Inverter, 314 Motor, 315 Compressor, 400 Control unit, 410 DC / DC converter, 501, 503 Voltage detection unit, 502, 504 Current detection unit, 501a, 502a, 503a, 504a Detection resistor, 501b, 503b Voltage dividing resistor, 550 Low-pass filter, 600a Bus P line, 600b Bus N line, 601, 602, 603, 604, 610b wiring, 900 refrigeration cycle applicable equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A single-stage boost type AC-DC converter having a rectifier circuit that rectifies a first AC voltage supplied from an AC power supply and outputs a rectified voltage, and a single-stage boost circuit that boosts the rectified voltage and outputs a first DC voltage; a capacitor that smoothes the first DC voltage into a second DC voltage; an inverter that converts the second DC voltage into a second AC voltage and outputs it to a load; a first voltage detection unit that outputs a detected value of the rectified voltage at a subsequent stage of the rectifier circuit; a first current detection unit that outputs a detected value of a rectified current output from the rectifier circuit at a subsequent stage of the rectifier circuit; a second voltage detection unit that outputs a detected value of the second DC voltage, which is a bus voltage between a bus P line and a bus N line, at a previous stage of the inverter; a second current detection unit that outputs a detected value of a current flowing through the inverter, which is a current used to estimate a current flowing from the inverter to the load, at a previous stage of the inverter; and a control unit that controls operations of switching elements included in the single-stage boost type AC-DC converter and switching elements included in the inverter using the detected values. The reference potential of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit is the bus N line. A power conversion device.

2. Each of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit is connected to a detection resistor, and a low-pass filter of two or more stages is connected to a second end opposite to a first end connected to the bus N line in each detection resistor. The power conversion device according to claim 1.

3. Each of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit is connected to a detection resistor. A single-stage low-pass filter is connected to a second end opposite to a first end connected to the bus N line in each detection resistor connected to the first voltage detection unit and the second voltage detection unit, and a low-pass filter of two or more stages is connected to a second end opposite to a first end connected to the bus N line in each detection resistor connected to the first current detection unit and the second current detection unit. The power conversion device according to claim 1.

4. In the power conversion device according to claim 2 or 3, the filtering process by the low-pass filter after the second stage among the two or more stages of low-pass filters is performed by software processing of the control unit.

5. In the power conversion device according to any one of claims 1 to 4, the reference potential of the power supply voltage of the control unit is the bus N line.

6. In the power conversion device according to claim 5, the upper limit voltage of the output voltages of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit is equal to or lower than the power supply voltage of the control unit.

7. Connect the wirings on the reference potential side of the first voltage detection unit, the first current detection unit, the second voltage detection unit, and the second current detection unit to a single-point ground.

8. A motor drive device including the power conversion device according to any one of claims 1 to 7.

9. A refrigeration cycle application device including the power conversion device according to any one of claims 1 to 7.

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