Power conversion device, motor drive device, and equipment for refrigeration cycle applications

Abstract

A power conversion device (50) includes a converter (3) that converts an alternating current to a direct current and outputs the direct current to a load (130) and a microcomputer (14) that controls the converter (3). A reference potential of converter control signals (S1-S6) for controlling the converter (3) is a potential of an emitter or a source of a lower element of a plurality of semiconductor elements (Q1-Q6) provided in the converter (3), and the emitter or the source and the microcomputer (14) are connected without through a component that generates a potential difference.

Description

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

[0001] The present disclosure relates to a power conversion device including a converter that converts AC to DC and outputs the DC to a load, a motor drive device including a power conversion device, and refrigeration cycle equipment.

[0002] Power supply current, which is the current supplied from an AC power supply, contains harmonic currents. Harmonic currents are frequency components with frequencies higher than the fundamental frequency. To suppress interference caused by harmonic currents, international regulations have been established for electronic devices that generate harmonic currents. To comply with these regulations, converters take measures to suppress the harmonic currents contained in the power supply current by chopping AC (Alternating Current) or DC (Direct Current).

[0003] Patent Document 1 listed below discloses a power conversion device equipped with a three-phase PWM (Pulse Width Modulation) converter. The three-phase PWM converter is a converter that performs chopping in AC. The use of any converter, not limited to a three-phase PWM converter, controls the power supply current to a sinusoidal waveform, making it possible to suppress power supply harmonics, which are harmonic currents contained in the power supply current.

[0004] Japanese Patent Application Laid-Open No. 2005-151755

[0005] Unlike rectifier circuits, converters are equipped with one or more semiconductor elements. The on / off of the semiconductor elements is controlled by a control signal generated by a microcomputer, which serves as a control means. However, to properly suppress power supply harmonics, precise control of the conduction of the semiconductor elements is required. Generally, a microcomputer generates a control signal based on its own reference potential. However, if the reference potential on the microcomputer side differs from the reference potential on the semiconductor element side, the control signal becomes unstable, and the timing at which the semiconductor element turns on may deviate from the intended timing.

[0006] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can stabilize a control signal generated by a microcomputer.

[0007] To solve the above-mentioned problems and achieve the object, a power conversion device according to the present disclosure includes a converter that converts AC to DC and outputs the DC to a load, and a first microcomputer that controls the converter. A reference potential of a converter control signal that controls the converter is set to the potential of the emitter or source of a lower element among a plurality of first semiconductor elements provided in the converter, and the emitter or source of the lower element and the first microcomputer are connected without passing through a component that generates a potential difference.

[0008] The power conversion device according to the present disclosure has the advantage of being able to stabilize the control signal generated by the microcomputer.

[0009] FIG. 1 is a diagram showing an example of the configuration of a motor drive device including a power conversion device according to embodiment 1; FIG. 2 is a diagram showing the operating waveforms of the main parts of the power conversion device according to embodiment 1; FIG. 3 is a diagram showing an undesirable connection configuration of the first microcomputer provided in the power conversion device according to embodiment 1 as a comparative example; FIG. 4 is a diagram showing the relationship between the reference potential of the converter control signal, the gate-on start potential, and the emitter-side potential of the converter in the connection configuration shown in FIG. 3; FIG. 5 is a diagram showing the relationship between the reference potential of the converter control signal, the gate-on start potential, and the emitter-side potential of the converter in the connection configuration shown in FIG. 5;

[0010] 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 accompanying drawings.

[0011] First Embodiment Fig. 1 is a diagram showing an example of the configuration of a motor drive device 100 including a power conversion device 50 according to a first embodiment. The power conversion device 50 according to the first embodiment is a power conversion device that converts AC voltage output from a three-phase power supply 110, which is a three-phase AC power supply, into DC voltage and applies the DC voltage to a load 130. The motor drive device 100 according to the first embodiment is also a drive device that converts DC power output from the power conversion device 50 into AC power and supplies the converted AC power to a motor 120 to drive the motor 120. As shown in the figure, the phases of the three-phase power supply 110 are represented by R, S, and T, and are referred to as the "R phase," the "S phase," and the "T phase," respectively.

[0012] 1, the power conversion device 50 according to the first embodiment includes a converter 3, a capacitor 4, a shunt resistor 7 for current detection, a current detection unit 10, a voltage detection unit 11, a microcomputer 14 which is a first microcomputer, and a drive circuit 16 which is a first drive circuit. The motor drive device 100 according to the first embodiment includes the power conversion device 50, and further includes a noise filter 1, a reactor 2, current detectors 5a and 5b, a phase voltage detection unit 6, a microcomputer 15 which is a second microcomputer, and a load 130, as shown in FIG.

[0013] The load 130 includes a shunt resistor 8 for current detection, an inverter 9, a current detection unit 12, a drive circuit 17 which is a second drive circuit, current detectors 18a and 18b, and a motor 120. Of the components of the load 130, the shunt resistor 8, the inverter 9, the current detection unit 12, the drive circuit 17, and the current detectors 18a and 18b, excluding the motor 120, are components of the motor drive device 100.

[0014] The noise filter 1 is disposed between the three-phase power supply 110 and the reactor 2. The noise filter 1 operates to reduce noise currents flowing in and out of the power conversion device 50. The reactor 2 is disposed between the noise filter 1 and the power conversion device 50. The reactor 2 is a device including circuit elements that temporarily store electrical energy supplied from the three-phase power supply 110. The reactor 2 also operates to reduce noise currents flowing in and out of the power conversion device 50.

[0015] The current detectors 5a and 5b detect the power supply current, which is an AC current flowing between the three-phase power supply 110 and the power conversion device 50, and output the detected values ​​of the power supply current to the microcomputer 14. An example of the current detectors 5a and 5b is an ACCT (Alternating Current Transformer). While FIG. 1 illustrates an example in which the current detector 5a detects the R-phase current Ir and the current detector 5b detects the T-phase current It, this example is not limiting. The current detectors 5a and 5b only need to detect the currents of any two of the three phases; the currents of the remaining phases can be calculated by utilizing the fact that the power supply currents are three-phase balanced. The phase voltage detector 6 detects the phase voltages of the three phases output by the three-phase power supply 110, which are the R-phase voltage Vr, the S-phase voltage Vs, and the T-phase voltage Vt, and outputs the detected values ​​to the microcomputer 14.

[0016] The converter 3 converts the AC voltage output from the three-phase power supply 110 into a DC voltage and outputs it to DC buses 19a and 19b. The DC buses 19a and 19b are electrical wiring that connect the converter 3 to the load 130. The voltage between the DC buses 19a and 19b is called the "bus voltage."

[0017] The output voltage of the converter 3 is applied across the capacitor 4. The capacitor 4 is connected to the DC buses 19a and 19b. Therefore, in the configuration of FIG. 1 , the capacitor voltage, which is the voltage across the capacitor 4, is equal to the bus voltage. The capacitor 4 smoothes the output voltage of the converter 3. The voltage smoothed by the capacitor 4 is applied to the inverter 9.

[0018] The voltage detection unit 11 detects the bus voltage Vdc and outputs the detected value of the bus voltage Vdc to the microcomputers 14 and 15. A converter current I1 flows through the shunt resistor 7. The converter current I1 is a current that flows in and out of the converter 3. The current detection unit 10 converts a voltage value generated when the converter current I1 flows through the shunt resistor 7 into a current value and outputs the current value to the microcomputer 14.

[0019] The converter 3 includes six semiconductor elements Q1 to Q6 that are connected in a three-phase bridge configuration. The semiconductor elements Q1 and Q2 are connected in series in this order, and a connection point 3a between the semiconductor elements Q1 and Q2 is electrically connected to the R phase of the three-phase power supply 110. The semiconductor elements Q3 and Q4 are connected in series in this order, and a connection point 3b between the semiconductor elements Q3 and Q4 is electrically connected to the S phase of the three-phase power supply 110. The semiconductor elements Q5 and Q6 are connected in series in this order, and a connection point 3c between the semiconductor elements Q5 and Q6 is electrically connected to the T phase of the three-phase power supply 110.

[0020] In this paper, the semiconductor elements Q1, Q3, and Q5 arranged on the upper side of the circuit diagram may be referred to as "upper elements," and the semiconductor elements Q2, Q4, and Q6 arranged on the lower side of the circuit diagram may be referred to as "lower elements." Also, in this paper, the side of the three-phase power supply 110 where connection points 3a to 3c are located, as viewed from the converter 3, may be referred to as the "AC side," and the side of the load 130 may be referred to as the "DC side."

[0021] The semiconductor elements Q1 to Q6 each include a diode D1 to D6 connected in parallel. The diodes D1 to D6 are connected so that their anodes are located on the AC side and their cathodes are located on the DC side. While FIG. 1 illustrates a case where the semiconductor elements Q1 to Q6 are IGBTs (insulated gate bipolar transistors), MOSFETs (metal oxide semiconductor field effect transistors) may be used instead of IGBTs. Note that, because MOSFETs have a built-in parasitic diode due to their structure, a configuration in which the diodes D1 to D6 are not connected in parallel may also be employed.

[0022] The inverter 9 converts DC to AC. More specifically, the inverter 9 converts the DC voltage output from the power conversion device 50 into AC voltage to be applied to the motor 120 and outputs the AC voltage. An example of an apparatus in which the motor 120 is mounted is a blower or compressor in an air conditioner. The air conditioner is an example of an apparatus that applies a refrigeration cycle.

[0023] An inverter current I2 flows through the shunt resistor 8. The inverter current I2 is a current that flows in and out of the inverter 9. The current detection unit 12 converts a voltage value generated when the inverter current I2 flows through the shunt resistor 8 into a current value and outputs the current value to the microcomputer 15.

[0024] The inverter 9 includes six semiconductor elements Q21 to Q26 that are connected in a three-phase bridge configuration. The semiconductor elements Q21 and Q22 are connected in series in this order, with a connection point 9a between the semiconductor elements Q21 and Q22 electrically connected to the U-phase of the motor 120. The semiconductor elements Q23 and Q24 are connected in series in this order, with a connection point 9b between the semiconductor elements Q23 and Q24 electrically connected to the V-phase of the motor 120. The semiconductor elements Q25 and Q26 are connected in series in this order, with a connection point 9c between the semiconductor elements Q25 and Q26 electrically connected to the W-phase of the motor 120. Note that, from the perspective of the inverter 9, the side of the converter 3 is the DC side, and the side of the motor 120 where the connection points 9a to 9c are located is the AC side. In this paper, in order to distinguish between the semiconductor elements Q1 to Q6 provided in the converter 3 and the semiconductor elements Q21 to Q26 provided in the inverter 9 without using symbols, the former may be referred to as the "first semiconductor elements" and the latter as the "second semiconductor elements."

[0025] The semiconductor elements Q21 to Q26 each include a diode D21 to D26 connected in parallel. The diodes D21 to D26 are connected so that their cathodes are on the DC side and their anodes are on the AC side. While FIG. 1 shows a case where the semiconductor elements Q21 to Q26 are IGBTs, MOSFETs may be used instead of the IGBTs. Note that, in the case of MOSFETs, a parasitic diode is built into the structure, so a configuration in which the diodes D21 to D26 are not connected in parallel may also be employed. Furthermore, an IGCT (Integrated Gate Commutated Thyristor) may be used instead of the IGBTs.

[0026] The semiconductor elements Q1 to Q6 can be modularized in units of one or more elements, or all of the elements may be housed in a single package and modularized. The same applies to the semiconductor elements Q21 to Q26. That is, the semiconductor elements Q21 to Q26 may be modularized in units of one or more elements, or all of the elements may be housed in a single package and modularized.

[0027] Current detectors 18a and 18b detect three-phase motor currents flowing between inverter 9 and motor 120 and output the detected motor current values ​​to microcomputer 15. An example of current detectors 18a and 18b is an ACCT. Note that while FIG. 1 shows an example in which current detector 18a detects U-phase motor current Iu and current detector 18b detects W-phase motor current Iw, this example is not limiting. Current detectors 18a and 18b only need to detect currents in any two of the three phases, and the currents in the remaining phases can be calculated by utilizing the fact that motor currents are three-phase balanced.

[0028] The microcomputer 14 generates converter control signals S1 to S6 for controlling the bus voltage to a desired voltage while controlling the power supply current to a sinusoidal wave based on the detection values ​​of the current detectors 5a and 5b, the detection value of the phase voltage detection unit 6, the detection value of the current detection unit 10, and the detection value of the voltage detection unit 11. The converter control signals S1 to S6 are control signals for controlling the semiconductor elements Q1 to Q6 of the converter 3, respectively. The converter control signals S1 to S6 generated by the microcomputer 14 are input to the drive circuit 16.

[0029] Furthermore, the microcomputer 15 generates inverter control signals S21 to S26 for rotating the motor 120 at a desired rotation speed based on the detection values ​​of the voltage detection unit 11, the current detection unit 12, and the current detectors 18a and 18b. The inverter control signals S21 to S26 are control signals for controlling the semiconductor elements Q21 to Q26 of the inverter 9, respectively. The inverter control signals S21 to S26 generated by the microcomputer 15 are input to the drive circuit 17.

[0030] Drive circuit 16 generates drive pulses G1 to G6 based on converter control signals S1 to S6. Semiconductor elements Q1 to Q6 of converter 3 perform switching operations in response to drive pulses G1 to G6. Drive circuit 17 generates drive pulses G21 to G26 based on inverter control signals S21 to S26. Semiconductor elements Q21 to Q26 of inverter 9 perform switching operations in response to drive pulses G21 to G26.

[0031] 1, the microcomputer 14 is a component of the power conversion device 50, but the present invention is not limited to this configuration. The microcomputer 14 may be provided outside the power conversion device 50 as a component of the motor drive device 100.

[0032] Next, the configuration and key points of operation of the power conversion device 50 according to the first embodiment will be described. Fig. 2 is a diagram showing the operational waveforms of the main parts of the power conversion device 50 according to the first embodiment. Fig. 2 shows, from top to bottom, the waveforms of the phase voltages of each of the three phases, the phase currents of each of the three phases, and the bus voltage Vdc. The horizontal axis of Fig. 2 represents time.

[0033] The upper part of FIG. 2 shows the waveforms of the R-phase voltage Vr, the S-phase voltage Vs, and the T-phase voltage Vt, which are sinusoidal voltage waveforms. The middle part of FIG. 2 shows the waveforms of the R-phase current Ir, the S-phase current Is, and the T-phase current It, which are sinusoidal current waveforms. These sinusoidal current waveforms are obtained by PWM control of the semiconductor elements Q1 to Q6 of the converter 3. By making the R-phase current Ir, the S-phase current Is, and the T-phase current It sinusoidal, power supply harmonics are suppressed. The lower part of FIG. 2 shows the waveform of the bus voltage Vdc, which is controlled to be approximately constant. By controlling the bus voltage Vdc to be constant, it is possible to stably drive the load 130. Note that in the first embodiment, the bus voltage Vdc does not necessarily have to be controlled to be constant.

[0034] Fig. 3 is a diagram showing, as a comparative example, an undesirable connection configuration of the microcomputer 14 provided in the power conversion device 50 according to embodiment 1. Fig. 3 shows the converter 3, capacitor 4, shunt resistors 7 and 8, drive circuit 16, and microcomputer 14 extracted from Fig. 1, as well as a power supply 72 that supplies operating power to the microcomputer 14.

[0035] 4 is a diagram showing the relationship between the reference potential of the converter control signals S1 to S6 in the connection configuration shown in Fig. 3, the gate-on start potential, and the emitter potential of the converter 3. When the semiconductor elements Q1 to Q6 are MOSFETs, the emitter potential of the converter 3 is the source potential of the converter 3.

[0036] 3, the reference potential of the converter control signals S1 to S6 is set to the low potential side of the capacitor 4. Furthermore, during powering to drive the load 130, a current flows through the shunt resistor 7 in the direction shown in FIG. 3, i.e., a current flows toward the converter 3. Therefore, when the converter 3 is in powering operation, the emitter potential of the converter 3 becomes negative due to the voltage drop across the shunt resistor 7.

[0037] Here, for example, if a sudden current flows through converter 3, the emitter potential of converter 3 also drops suddenly due to the current. Therefore, as shown in FIG. 4, the reference potential of converter control signals S1 to S6 may become higher than the gate-on start potential of semiconductor elements Q1 to Q6. Vth is the threshold voltage at which semiconductor elements Q1 to Q6 conduct. For this reason, in the connection configuration shown in FIG. 3, semiconductor elements Q1 to Q6 may erroneously turn on.

[0038] Therefore, in the first embodiment, the microcomputer 14 is connected as shown in Fig. 5. Fig. 5 is a diagram showing a preferred connection configuration of the microcomputer 14 provided in the power conversion device 50 according to the first embodiment. Fig. 6 is a diagram showing the relationship between the reference potentials of the converter control signals S1 to S6, the gate-on start potential, and the emitter potential of the converter 3 in the connection configuration shown in Fig. 5.

[0039] 5, the reference potential of the converter control signals S1 to S6 is the emitter potential of the converter 3. In this connection, the microcomputer 14 is connected to the emitter potential of the converter 3 without passing through the shunt resistor 7, which is a component that generates a potential difference. Therefore, the reference potential of the converter control signals S1 to S6 is the emitter potential of the converter 3. Therefore, when the converter 3 is performing powering operation, the reference potential of the converter control signals S1 to S6 does not rise to the positive side with respect to the emitter potential of the converter 3, and the possibility of the semiconductor elements Q1 to Q6 being erroneously turned on can be extremely reduced.

[0040] As described above, the power conversion device according to the first embodiment includes a converter that converts AC to DC and outputs the converted DC to a load, and a first microcomputer that controls the converter. The reference potential of a converter control signal that controls the converter is set to the potential of the emitter or source of a lower element among a plurality of first semiconductor elements included in the converter. The emitter or source of the lower element is connected to the first microcomputer without any component that generates a potential difference. With this power conversion device configured in this manner, the reference potential of the converter control signal is set to the emitter or source potential of the lower element of the converter, thereby enabling the converter control signal generated by the first microcomputer to be stabilized.

[0041] In the power conversion device according to the first embodiment, the first semiconductor elements included in the converter may all be housed in a single package and modularized. In a configuration in which all elements are housed in a single package, the physical distance between the semiconductor elements is shortened, which significantly reduces the potential difference between the semiconductor elements. This reduces the difference in gate-on start potential between the semiconductor elements. This allows for further stabilization of the converter control signal generated by the first microcomputer.

[0042] Second Embodiment In a second embodiment, a description will be given of the configuration and main points of operation of the motor drive device 100 shown in Fig. 1. Fig. 7 is a diagram showing a preferred connection configuration of the microcomputer 15 provided in the motor drive device 100 according to the second embodiment.

[0043] 7, the same circuitry as in Fig. 5 is shown to the left of the capacitor 4. Also, to the right of the capacitor 4, the inverter 9, shunt resistor 8, drive circuit 17, and microcomputer 15, which are extracted from Fig. 1, are shown, as well as a power supply 74 that supplies operating power to the microcomputer 15.

[0044] 7, the reference potential of the inverter control signals S21 to S26 is set to the low potential side of the capacitor 4. Furthermore, during powering to drive the motor 120, a current flows through the shunt resistor 8 in the direction shown in FIG. 3, i.e., a current flows from the inverter 9 toward the capacitor 4. Therefore, when the inverter 9 is operating in powering mode, the emitter potential of the inverter 9 becomes positive due to the voltage drop across the shunt resistor 8.

[0045] Here, for example, if a sudden current flows through inverter 9, there will be a sudden change in the potential difference between the emitter potential of inverter 9 and the potential on the low potential side of capacitor 4. In this case, if the reference potential of inverter control signals S21 to S26 is the potential on the low potential side of capacitor 4, there is a possibility that semiconductor elements Q21 to Q26 will be erroneously turned off, contrary to the case of FIG.

[0046] On the other hand, in the connection configuration of Figure 7, the reference potential of the inverter control signals S21 to S26 is the emitter side potential of the inverter 9, so that when the inverter 9 is operating in power running mode, the possibility of the semiconductor elements Q21 to Q26 being turned off by mistake can be reduced.

[0047] In the motor drive device 100 described in the first and second embodiments, the converter 3 and the inverter 9 are not controlled by a common microcomputer, but rather by different microcomputers 14 and 15, respectively, which enables the connection configuration shown in Figure 7. Note that if the resistance value of the shunt resistor 8 is small, the voltage drop due to the shunt resistor 8 is small, reducing the possibility of the semiconductor elements Q21 to Q26 being turned off erroneously. Therefore, if the resistance value of the shunt resistor 8 is small, the reference potential of the inverter control signals S21 to S26 can be set to the potential on the low potential side of the capacitor 4.

[0048] As described above, the motor drive device according to the second embodiment includes the power conversion device according to the first embodiment, an inverter that converts the output voltage of the power conversion device into an AC voltage and applies the AC voltage to a motor provided as a load, and a second microcomputer that controls the inverter. The reference potential of the inverter control signal that controls the inverter is the potential of the emitter or source of a lower element among a plurality of second semiconductor elements provided in the inverter. The emitter or source of the lower element is connected to the second microcomputer without any component that generates a potential difference. According to the motor drive device according to the second embodiment, when at least the converter is operating, the reference potential of the converter control signal and the reference potential of the inverter control signal are different potentials. Furthermore, according to the motor drive device according to the second embodiment, the reference potential of the converter control signal is the emitter potential or source potential of the lower element of the converter, and the reference potential of the inverter control signal is the emitter potential or source potential of the lower element of the inverter or the potential on the low-potential side of capacitor 4. This power conversion device configured in this manner makes it possible to stabilize both the converter control signal and the inverter control signal generated by the first and second microcomputers.

[0049] In the motor drive device according to the second embodiment, the second semiconductor elements included in the inverter may all be housed in a single package and modularized. In a configuration in which all elements are housed in a single package, the physical distance between the semiconductor elements is shortened, which significantly reduces the potential difference between the multiple semiconductor elements, thereby reducing the difference in gate-on start potential between the multiple semiconductor elements. This allows for further stabilization of the inverter control signal generated by the second microcomputer.

[0050] Embodiment 3. Figure 8 is a diagram showing an example of the configuration of an air conditioner 300 according to embodiment 3. The air conditioner 300 according to embodiment 3 is an example of a refrigeration cycle-applied device, and includes the motor drive device 100 and motor 120 described in embodiment 1. The air conditioner 300 also includes a compressor 81, a four-way valve 82, an outdoor heat exchanger 83, an expansion valve 84, an indoor heat exchanger 85, and refrigerant piping 86.

[0051] The air conditioner 300 may be a separate type air conditioner in which the outdoor unit is separated from the indoor unit, or an integrated type air conditioner in which the compressor 81, indoor heat exchanger 85, and outdoor heat exchanger 83 are provided within a single housing.

[0052] The compressor 81 contains a compression mechanism 87 that compresses the refrigerant and a motor 120 that operates the compression mechanism 87. The motor 120 is driven by a motor drive device 100. In the air conditioner 300, a refrigeration cycle is formed by circulating the refrigerant through the compressor 81, the four-way valve 82, the outdoor heat exchanger 83, the expansion valve 84, the indoor heat exchanger 85, and the refrigerant piping 86.

[0053] The components of the air conditioner 300 can also be applied to appliances such as refrigerators or freezers equipped with a refrigeration cycle. In addition, in the third embodiment, the motor 120 is used as the drive source for the compressor 81, but the motor 120 may also be used as the drive source for an indoor unit blower and an outdoor unit blower (not shown) instead of the compressor 81. Alternatively, the motor 120 may be used as the drive source for each of the indoor unit blower, the outdoor unit blower, and the compressor 81, and these three motors 120 may be driven by the motor drive device 100.

[0054] The air conditioner 300 according to the third embodiment is configured to include the motor drive device 100 according to the first embodiment, and therefore can stabilize the control signal generated by the microcomputer provided in the power conversion device, thereby enabling accurate conduction control of the semiconductor elements and appropriate suppression of power supply harmonics.

[0055] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0056] REFERENCE SIGNS LIST 1 noise filter, 2 reactor, 3 converter, 3a to 3c, 9a to 9c connection points, 4 capacitor, 5a, 5b, 18a, 18b current detector, 6 phase voltage detector, 7, 8 shunt resistor, 9 inverter, 10, 12 current detector, 11 voltage detector, 14, 15 microcomputer, 16, 17 drive circuit, 19a, 19b DC bus, 50 power converter, 72, 74 power supply, 81 compressor, 82 four-way valve, 83 outdoor heat exchanger, 84 expansion valve, 85 indoor heat exchanger, 86 refrigerant piping, 87 compression mechanism, 100 motor drive device, 110 three-phase power supply, 120 motor, 130 load, 300 air conditioner, D1 to D6, D21 to D26 diodes, Q1 to Q6, Q21 to Q26 Semiconductor element.

Claims

1. A power conversion device including a converter that converts AC into DC and outputs the converted DC to a load, and a first microcomputer that controls the converter, a reference potential of a converter control signal for controlling the converter is set to a potential of an emitter or a source of a lower element among a plurality of first semiconductor elements provided in the converter; The emitter or source of the lower element and the first microcomputer are connected without any component that generates a potential difference. Power conversion device.

2. The plurality of first semiconductor elements are all housed in a single package and modularized. The power conversion device according to claim 1 .

3. The power conversion device according to claim 1 or 2; an inverter that converts the output voltage of the power conversion device into an AC voltage and applies the AC voltage to a motor provided in the load; a second microcomputer that controls the inverter; Equipped with At least when the converter is operating, the reference potential of the converter control signal and the reference potential of the inverter control signal that controls the inverter are at different potentials. Motor drive device.

4. The plurality of second semiconductor elements provided in the inverter are all housed in a single package and modularized. The motor drive device according to claim 3 .

5. A refrigeration cycle device comprising the motor drive device according to claim 3.

6. The power conversion device according to claim 1 or 2; an inverter that converts the output voltage of the power conversion device into an AC voltage and applies the AC voltage to a motor provided in the load; a second microcomputer that controls the inverter; Equipped with a reference potential of an inverter control signal that controls the inverter is set to an emitter or a source of a lower element among a plurality of second semiconductor elements included in the inverter; The emitter or source of the lower element of the plurality of second semiconductor elements is connected to the second microcomputer without any component that generates a potential difference. Motor drive device.

7. A refrigeration cycle device comprising the motor drive device according to claim 6.