Power conversion device and refrigeration cycle device comprising same

Abstract

This power conversion device comprises: an electric power conversion circuit that converts electric power which is input from a power supply via a power supply line into electric power which is supplied to a load; and an active noise cancellation circuit that outputs, to the power supply line, a cancellation current which reduces noise flowing from the electric power conversion circuit to the power supply line. The active noise cancellation circuit has a protection part that reduces the cancellation current upon a rise in temperature.

Description

Power conversion device and refrigeration cycle device equipped with the same

[0001] The present disclosure relates to a power conversion device to which power is supplied from a power source and a refrigeration cycle device including the same.

[0002] Conventionally, noise from an inverter that drives a compressor installed in an air conditioner flows into a power line. To suppress this noise, a noise filter composed of passive elements is used. However, when a noise filter is composed only of passive elements, the frequency band of noise that can be suppressed is limited. To address this issue, a power conversion device has been proposed that detects common-mode noise current flowing in a power line supplied with AC and suppresses the common-mode noise current using active elements (see, for example, Patent Document 1).

[0003] The power conversion device disclosed in Patent Document 1 includes a suppression unit that functions as an active conductive noise suppression circuit. The suppression unit has a first coil unit that detects common-mode noise current, a second coil unit that passes a current that suppresses the common-mode noise current through a power line, and a current supply unit that is provided between the first coil unit and the second coil unit and functions as a current source for supplying a current to the second coil unit.

[0004] Japanese Patent Application Laid-Open No. 2018-191443

[0005] The current supply unit disclosed in Patent Document 1 includes an amplifier circuit composed of relatively low-durability components such as an operational amplifier or a transistor. Therefore, when an excessive current flows from the first coil unit into the amplifier circuit, the amplifier circuit attempts to amplify the input current, causing the temperature of the operational amplifier or the transistor to rise, which may result in destruction by heat. For example, when an excessive current is input into the amplifier circuit due to a lightning surge, the amplification action causes the temperature of the operational amplifier or the transistor to rise, which may result in destruction of the amplifier circuit by heat.

[0006] The present disclosure has been made to solve the above-mentioned problems, and provides a power conversion device that prevents a noise suppression circuit from being destroyed even when an excessive current is detected, and a refrigeration cycle device equipped with the same.

[0007] The power conversion device according to the present disclosure comprises a power conversion circuit that converts power input from a power source via a power line into power to be supplied to a load, and an active noise cancellation circuit that outputs a cancellation current to the power line that reduces noise flowing from the power conversion circuit to the power line, and the active noise cancellation circuit has a protection section that reduces the cancellation current when the temperature rises.

[0008] A refrigeration cycle device according to the present disclosure includes a refrigerant circuit including a compressor, and the above-described power conversion device that supplies power to the compressor to drive the electric motor of the compressor.

[0009] According to the present disclosure, an active noise cancellation circuit is provided with a protection unit that reduces the cancellation current when the temperature rises. Therefore, even if an excessive current flows into the active noise cancellation circuit, the increase in the cancellation current is suppressed, and the temperature rise of the active noise cancellation circuit is suppressed. As a result, the active noise cancellation circuit can be prevented from being destroyed by heat.

[0010] Fig. 7 is a refrigerant circuit diagram showing an example of the configuration of a refrigeration cycle device including a power conversion device according to embodiment 1. Fig. 8 is a circuit diagram showing an example of the configuration of a power conversion device according to embodiment 1. Fig. 9 is a circuit diagram showing an example of the configuration of the power conversion circuit shown in Fig. 2. Fig. 10 is a circuit diagram showing an example of the configuration of an ANC shown in Fig. 2. Fig. 11 is a circuit diagram showing the configuration of an ANC in a power conversion device according to modification 1. Fig. 12 is a circuit diagram showing the configuration of an ANC in a power conversion device according to modification 2. Fig. 13 is a circuit diagram showing an example of the configuration of an ANC in a power conversion device according to modification 3. Fig. 14 is a circuit diagram showing an example of the configuration of the TSD circuit shown in Fig. 7. Fig. 15 is a circuit diagram showing the configuration of an ANC in a power conversion device according to modification 4.

[0011] Embodiments of a power conversion device according to the present disclosure will be described with reference to the drawings. The power conversion device according to the present disclosure is not limited to the embodiments described below. In addition, in the following embodiments, electrical connections will be simply referred to as "connections."

[0012] Embodiment 1. The configuration of a refrigeration cycle device equipped with a power conversion device according to Embodiment 1 will be described. In Embodiment 1, the refrigeration cycle device will be described as an air conditioner, but the refrigeration cycle device is not limited to air conditioners. Fig. 1 is a refrigerant circuit diagram showing an example of the configuration of a refrigeration cycle device equipped with a power conversion device according to Embodiment 1.

[0013] The refrigeration cycle apparatus 10 has a heat source side unit 20 and a load side unit 30. The heat source side unit 20 has a compressor 21, a four-way valve 22, a heat source side heat exchanger 23, an expansion valve 24, an outdoor fan 25, and a controller 26. The compressor 21 is provided with the power conversion device 1 of the first embodiment. The power conversion device 1 supplies power to the compressor 21 to drive an electric motor (not shown) of the compressor 21. The load side unit 30 has a load side heat exchanger 31 and an indoor fan 32. The load side unit 30 is provided with a room temperature sensor 33 that detects the temperature of the air in a room that is a space to be air-conditioned by the load side unit 30.

[0014] The compressor 21, the heat source-side heat exchanger 23, the expansion valve 24, and the load-side heat exchanger 31 are connected by a refrigerant pipe 34 to form a refrigerant circuit 35 in which the refrigerant circulates. The power conversion device 1, the four-way valve 22, the expansion valve 24, the outdoor fan 25, the indoor fan 32, and the room temperature sensor 33 are each connected to the controller 26 via a signal line (not shown). The room temperature sensor 33 detects the room temperature at regular intervals and transmits information about the detected room temperature to the controller 26.

[0015] The compressor 21 draws in refrigerant, compresses the drawn refrigerant, and discharges high-temperature, high-pressure refrigerant. The compressor 21 is an inverter compressor whose capacity can be changed by controlling its operating frequency. The four-way valve 22 switches the flow direction of the refrigerant circulating through the refrigerant circuit 35 according to the operating mode of the refrigeration cycle apparatus 10. The operating modes include, for example, heating operation, cooling operation, and defrosting operation. When the operating mode of the refrigeration cycle apparatus 10 is cooling operation, the interior of the four-way valve 22 shown in FIG. 1 has a flow path indicated by a solid line. When the operating mode of the refrigeration cycle apparatus 10 is heating operation, the interior of the four-way valve 22 shown in FIG. 2 has a flow path indicated by a dashed line.

[0016] The outdoor fan 25 draws in outside air and sends it to the heat source-side heat exchanger 23. The heat source-side heat exchanger 23 is a heat exchanger that exchanges heat between the outside air and the refrigerant. The expansion valve 24 reduces the pressure of the refrigerant to expand it. The expansion valve 24 is, for example, an electronic expansion valve. The indoor fan 32 draws in air from the room and sends it to the load-side heat exchanger 31. The load-side heat exchanger 31 is a heat exchanger that exchanges heat between the indoor air and the refrigerant. The heat source-side heat exchanger 23 and the load-side heat exchanger 31 are, for example, fin-and-tube heat exchangers having heat transfer tubes (not shown) and multiple heat dissipation fins (not shown).

[0017] The controller 26 is, for example, a microcomputer. The controller 26 controls the operation of the refrigeration cycle apparatus 10. Specifically, the controller 26 controls the four-way valve 22 in accordance with an operation mode set by a user of the refrigeration cycle apparatus 10. The controller 26 controls the operating frequency of the compressor 21, the opening of the expansion valve 24, and the rotation speed of the outdoor fan 25 so that the detection value of the room temperature sensor 33 matches a preset set temperature. The controller 26 controls the rotation speed of the indoor fan 32 in accordance with the air volume set by the user.

[0018] 2 is a circuit diagram showing an example of the configuration of a power conversion device according to the first embodiment. The power conversion device 1 of the first embodiment includes a power conversion circuit 2 that converts power input from a power source 9 via a power line 15 into power to be supplied to a load 4, and an active noise cancellation circuit 3. Hereinafter, the active noise cancellation circuit will be referred to as an ANC (Active Noise Canceller). In the first embodiment, the load 4 is an electric motor that drives the compressor 21 shown in FIG. 1. The load 4 is an electric motor that has a rotor (not shown) and a stator (not shown), and the stator has a U-phase winding Ur, a V-phase winding Vr, and a W-phase winding Wr.

[0019] FIG. 3 is a circuit diagram showing an example configuration of the power conversion circuit shown in FIG. 2 . The power conversion circuit 2 includes a rectifier circuit 16, a smoothing circuit 17, and an inverter circuit 18. The inverter circuit 18 is connected to the load 4 via a power line 47. The rectifier circuit 16 converts AC voltage supplied from the power source 9 via the power line 15 into DC voltage. The rectifier circuit 16 includes six backflow prevention elements 41. The backflow prevention elements 41 are diode elements that rectify the current flow in one direction. The smoothing circuit 17 includes a reactor 42 that smooths the current output from the rectifier circuit 16 and a smoothing capacitor 43 that smooths the voltage output from the rectifier circuit 16. The smoothing circuit 17 outputs a stable DC power supply voltage to the inverter circuit 18.

[0020] The inverter circuit 18 has six switching elements 45a to 45f and six freewheeling diodes 46a to 46f, each connected in parallel to one switching element. The switching elements 45a and 45b are connected to a U-phase winding Ur of the load 4 via a power line 47. The switching elements 45c and 45d are connected to a V-phase winding Vr of the load 4 via a power line 47. The switching elements 45e and 45f are connected to a W-phase winding Wr of the load 4 via a power line 47. The gate electrodes of the switching elements 45a to 45f are connected to the controller 26 via signal lines (not shown). The controller 26 controls the switching between the ON state and the OFF state of each of the switching elements 45a to 45f. The controller 26 controls the ON state and the OFF state of the switching elements, thereby controlling the path of the current flowing from the power conversion circuit 2 to the load 4.

[0021] The switching elements 45a to 45f are semiconductor elements such as, for example, an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), or a high electron mobility transistor (HEMT).

[0022] Next, the configuration of the ANC 3 shown in Fig. 2 will be described. Fig. 4 is a circuit diagram showing an example configuration of the ANC shown in Fig. 2. As shown in Fig. 2, the ANC 3 is provided on the power supply line 15 between the power conversion circuit 2 and the power supply 9. As shown in Figs. 2 and 4, the ANC 3 has an input circuit 5, an output circuit 6, an amplifier circuit 7, and a protection unit 8.

[0023] ANC 3 outputs a canceling current to power line 15 to reduce noise flowing from power conversion circuit 2 to power line 15. Input circuit 5 has a detection passive element 11, which is a passive element that detects noise flowing in power line 15. Output circuit 6 has an injection passive element 12, which is a passive element that injects a canceling current into power line 15. Protection unit 8 has an input protection element 13 connected between input circuit 5 and amplifier circuit 7, and an output protection element 14 connected between output circuit 6 and amplifier circuit 7.

[0024] The input protection element 13 and the output protection element 14 function to reduce the cancellation current output from the amplifier circuit 7 when their temperatures rise. In the configuration example shown in Fig. 4, the input protection element 13 and the output protection element 14 are, for example, PTC (Positive Temperature Coefficient) thermistors. A PTC thermistor is a resistive element whose resistance value increases as the temperature rises. The input protection element 13 and the output protection element 14 have a positive temperature characteristic in which their impedance increases as the temperature rises.

[0025] Assuming that the impedance at 20°C is Z1, it is desirable that the impedance at 80°C be at least twice the impedance Z1 in the temperature characteristics of the input protection element 13 and the output protection element 14. This is because it is assumed that the temperature at which an abnormality occurs in the ANC is 80°C, and therefore it is desirable that the protection unit 8 have temperature characteristics that result in a sufficiently high resistance value at 80°C. If the input protection element 13 and the output protection element 14 are PTC thermistors, the temperature characteristics of each element are, for example, 300 Ω / °C at 20°C and 1000 Ω / °C at 80°C.

[0026] Amplifier circuit 7 generates a cancellation current corresponding to the noise detected by input circuit 5, and outputs the generated cancellation current to power supply line 15 via output circuit 6. As shown in Fig. 4, amplifier circuit 7 has an amplifier 50 that inverts and amplifies the signal input from input circuit 5, a resistive element 51 provided at one of the two terminals on the input side of amplifier 50, and a resistive element 52 provided in the negative feedback connection wiring.

[0027] Next, the operation of the power conversion device 1 of the first embodiment will be described with reference to Fig. 2. When noise generated from the power conversion circuit 2 flows into the power supply line 15, the noise is detected by the detection passive element 11 provided in the input circuit 5. The noise detected by the detection passive element 11 is input to the amplifier circuit 7 via the input protection element 13. When noise is input from the input protection element 13, the amplifier circuit 7 generates a canceling current that reduces the noise. The amplifier circuit 7 then outputs the generated canceling current to the power supply line 15 via the output protection element 14 and the injection passive element 12. By injecting the canceling current into the power supply line 15, the current caused by the noise flowing through the power supply line 15 is reduced.

[0028] Consider a case where an excessive current flows through power line 15 due to a phenomenon such as a lightning surge. When an excessive current flows through power line 15, the temperature of input protection element 13 rises via detection passive element 11, increasing the impedance of input protection element 13. The increased input impedance of amplifier circuit 7 suppresses the increase in the cancellation current output from amplifier circuit 7, thereby suppressing the temperature increase of amplifier circuit 7. It is also possible that when an excessive current flows through power line 15, the temperature of output protection element 14 rises via injection passive element 12. In this case, the impedance of output protection element 14 increases. The increased output impedance of amplifier circuit 7 suppresses the increase in the cancellation current output from amplifier circuit 7, thereby suppressing the temperature increase of amplifier circuit 7. In this way, even if an excessive current flows through power line 15, the temperature increase of amplifier circuit 7 is suppressed, preventing the amplifier circuit 7 from being destroyed by overheating.

[0029] In the first embodiment, the case where both the input protection element 13 and the output protection element 14 are provided in the protection unit 8 has been described, but it is sufficient if at least one of the input protection element 13 and the output protection element 14 is provided.

[0030] 2 and 4 show the case where the detection passive element 11 and the injection passive element 12 are coils, but the elements are not limited to coils. The detection passive element 11 is an element that detects noise flowing in the power supply line 15, and the injection passive element 12 is an element that can inject a canceling current that reduces noise into the power supply line 15. For example, one or both of the detection passive element 11 and the injection passive element 12 may be a capacitor.

[0031] Furthermore, the ANC 3 in the power conversion device 1 of the first embodiment is not limited to the configuration shown in Fig. 2 and Fig. 4. Modifications 1 to 4 of the ANC 3 will be described below. In Modifications 1 to 4, the same components as those described with reference to Figs. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0032] (Modification 1) Fig. 5 is a circuit diagram showing the configuration of an ANC in a power conversion device according to Modification 1. As shown in Fig. 5, in an ANC 3a, a protection unit 8a has an input protection element 13a and an output protection element 14a. The input protection element 13a and the output protection element 14a are coils whose magnetic permeability increases with increasing temperature. Fig. 5 shows a configuration in which the input protection element 13a and the output protection element 14a are provided in the ANC 3a, but it is sufficient if at least one of the input protection element 13a and the output protection element 14a is provided.

[0033] If the inductance of the coil is L [H] and the magnetic permeability is μ, the inductance L is proportional to the magnetic permeability μ. The impedance of the coil is proportional to the inductance L. Therefore, the impedance of the input protection element 13a and the output protection element 14a increases as the temperature increases. In this modification 1, if the input protection element 13a is provided in the ANC 3a, when an excessive current flows through the power line 15, the temperature of the input protection element 13a increases via the detection passive element 11, and the impedance of the input protection element 13a increases. By increasing the input impedance of the amplifier circuit 7, the increase in the cancel current output from the amplifier circuit 7 is suppressed, and the temperature increase of the amplifier circuit 7 can be suppressed. In this modification 1, if the output protection element 14a is provided in the ANC 3a, the impedance of the output protection element 14a increases as the temperature of the output protection element 14a increases. By increasing the output impedance of the amplifier circuit 7, the increase in the cancel current output from the amplifier circuit 7 is suppressed, and the temperature increase of the amplifier circuit 7 can be suppressed.

[0034] (Modification 2) Fig. 6 is a circuit diagram showing the configuration of an ANC in a power conversion device according to Modification 2. As shown in Fig. 6, in an ANC 3b, a protection unit 8b has an input protection element 13b and an output protection element 14b. The input protection element 13b and the output protection element 14b are capacitors whose dielectric constant decreases as the temperature rises. Fig. 6 shows a configuration in which the input protection element 13b and the output protection element 14b are provided in the ANC 3b, but it is sufficient if at least one of the input protection element 13b and the output protection element 14b is provided.

[0035] If the capacitance of a capacitor is C [F] and the dielectric constant is ε, the capacitance C is proportional to the dielectric constant ε. The impedance of a capacitor is inversely proportional to the capacitance C. Therefore, the impedance of the input protection element 13b and the output protection element 14b increases as the temperature increases. In this modification 2, if the input protection element 13b is provided in the ANC 3b, when an excessive current flows through the power supply line 15, the temperature of the input protection element 13b increases via the detection passive element 11, and the impedance of the input protection element 13b increases. By increasing the input impedance of the amplifier circuit 7, the increase in the cancel current output from the amplifier circuit 7 is suppressed, and the temperature increase of the amplifier circuit 7 can be suppressed. In this modification 2, if the output protection element 14b is provided in the ANC 3b, the impedance of the output protection element 14b increases as the temperature of the output protection element 14b increases. By increasing the output impedance of the amplifier circuit 7, the increase in the cancel current output from the amplifier circuit 7 is suppressed, and the temperature increase of the amplifier circuit 7 can be suppressed.

[0036] (Modification 3) Fig. 7 is a circuit diagram showing the configuration of an ANC in a power conversion device according to Modification 3. An ANC 3c of Modification 3 has a configuration in which a thermal shutdown (TSD) circuit 60 functioning as a protection unit 8 is provided in an amplifier circuit 7a. The TSD circuit 60 is a circuit that supplies an operating voltage Vd to the amplifier 50. Fig. 8 is a circuit diagram showing an example configuration of the TSD circuit shown in Fig. 7.

[0037] 8, the TSD circuit 60 includes a bipolar transistor 61 and resistor elements 62 to 64. The bipolar transistor 61 is a transistor in which the voltage Vbe between the base electrode and the emitter electrode exhibits a negative temperature characteristic. The bipolar transistor 61 maintains an OFF state when the temperature of the amplifier circuit 7a is equal to or lower than a predetermined threshold temperature Tth, and switches from the OFF state to the ON state when the temperature of the amplifier circuit 7a is higher than the threshold temperature Tth. The threshold temperature Tth is, for example, 100°C.

[0038] Resistor elements 62 and 63 divide the power supply voltage Vcc and apply a constant base voltage Vb to the base electrode of bipolar transistor 61. If the resistance value of resistor element 62 is R1 and the resistance value of resistor element 63 is R2, then the base voltage Vb is expressed as Vb = Vcc × {R1 / (R1 + R2)}. Resistor element 64 serves to drop the power supply voltage Vcc to the operating voltage Vd.

[0039] The operation of the TSD circuit 60 will now be briefly described. When the temperature of the amplifier circuit 7a is equal to or lower than the threshold temperature Tth, the bipolar transistor 61 remains in the off state, and the operating voltage Vd is applied to the amplifier 50. On the other hand, when the temperature of the amplifier circuit 7a rises and exceeds the threshold temperature Tth, the bipolar transistor 61 switches from the off state to the on state, and the operating voltage Vd is no longer applied to the amplifier 50. As a result, the operation of the amplifier 50 stops. Note that, in the third modification, the case has been described in which the TSD circuit 60 stops supplying the operating voltage Vd to the amplifier 50 when the temperature of the amplifier circuit 7a exceeds the threshold temperature Tth. However, the TSD circuit 60 may also have a function to reduce the amplification factor of the amplifier 50.

[0040] In the third modification, too, when the temperature of amplifier 50 rises due to an excessive current flowing through power supply line 15, it is possible to suppress the temperature rise of amplifier circuit 7. Furthermore, in the third modification, there is no need to provide protection unit 8 between input circuit 5 and amplifier circuit 7 and between output circuit 6 and amplifier circuit 7.

[0041] (Variation 4) In this variation 4, one or both of the detection passive element 11 and the injection passive element 12 function as elements that determine the noise cancellation performance. Fig. 9 is a circuit diagram showing the configuration of an ANC in a power conversion device according to variation 4. In an ANC 3d shown in Fig. 9, the detection passive elements 11a and 12a are elements with positive temperature characteristics in which the impedance increases as the temperature rises.

[0042] The detection passive element 11a is, for example, any one of the input protection elements 13, 13a, and 13b. The injection passive element 12a is, for example, any one of the output protection elements 14, 14a, and 14b. In the configuration example shown in FIG. 9 , if the detection passive element 11a is provided in the input circuit 5, the injection passive element 12 may be provided in the output circuit 6 instead of the injection passive element 12a. In the configuration example shown in FIG. 9 , if the injection passive element 12a is provided in the output circuit 6, the detection passive element 11 may be provided in the input circuit 5 instead of the detection passive element 11a. In the case of the present modification 4, one or both of the detection passive element 11a and the injection passive element 12a serve as the protection unit 8, so there is no need to provide a protection unit 8 separately from the input circuit 5 and the output circuit 6.

[0043] The power conversion device 1 of the first embodiment includes a power conversion circuit 2 that converts power input from a power source 9 via a power line 15 into power to be supplied to a load 4, and an ANC 3 that outputs a canceling current to the power line 15 to reduce noise flowing from the power conversion circuit 2 to the power line 15. The ANC 3 includes a protection unit 8 that reduces the canceling current when the temperature rises.

[0044] According to the first embodiment, the ANC 3 is provided with a protection unit 8 that reduces the cancel current when the temperature rises. Therefore, even if an excessive current flows into the ANC 3 due to a phenomenon such as a lightning surge, the increase in the cancel current is suppressed, and the temperature rise of the ANC 3 is suppressed. As a result, the ANC 3 can be prevented from being destroyed by heat. Conventionally, there has been a problem in that the output setting of the amplifier circuit changes due to changes such as an increase in the resistance value of the detection passive element 11. To address this problem, the first embodiment changes the gain of the amplifier circuit 7 in consideration of changes such as an increase in the resistance value of the detection passive element 11, thereby suppressing changes in the cancel current.

[0045] For example, if an input protection element 13 is provided on the input side of the amplifier circuit 7 and the input protection element 13 is a PTC thermistor, when an excessive current flows through the input protection element 13 and causes it to overheat, the impedance of the input protection element 13 increases. Because the input impedance of the amplifier circuit 7 increases, the current amplified by the amplifier circuit 7 decreases, and the canceling current injected into the power supply line 15 decreases. In this way, the canceling current decreases when the temperature of the ANC 3 rises, preventing the temperature of the ANC 3 from rising excessively.

[0046] In the first embodiment, the power conversion device 1 is described as being provided in the refrigeration cycle device 10, but the device in which the power conversion device 1 is provided is not limited to a refrigeration cycle device. Also, in the first embodiment, the load 4 connected to the power conversion device 1 is the motor of the compressor 21, but the load 4 connected to the power conversion device 1 is not limited to the motor of the compressor.

[0047] In addition, in each of the protection unit 8 shown in Fig. 4, the protection unit 8a shown in Fig. 5, and the protection unit 8b shown in Fig. 6, the input protection element and the output protection element are the same type of passive element, but the types of these passive elements may be different. For example, in the protection unit 8 shown in Fig. 4, output protection element 14 may be replaced with output protection element 14a or 14b.

[0048] 1 Power conversion device, 2 Power conversion circuit, 3, 3a to 3d Active noise cancellation circuit (ANC), 4 Load, 5 Input circuit, 6 Output circuit, 7, 7a Amplification circuit, 8, 8a, 8b Protection unit, 9 Power supply, 10 Refrigeration cycle device, 11, 11a Detection passive element, 12, 12a Injection passive element, 13, 13a, 13b Input protection element, 14, 14a, 14b Output protection element, 15 Power line, 16 Rectification circuit, 17 Smoothing circuit, 18 Inverter circuit, 20 Heat source side unit, 21 Compressor, 22 Four-way valve, 23 Heat source side heat exchanger, 24 Expansion valve, 25 Outdoor fan, 26 Controller, 30 Load side unit, 31 Load side heat exchanger, 32 Indoor fan, 33 Room temperature sensor, 34 Refrigerant piping, 35 Refrigerant circuit, 41 Reverse current prevention element, 42 reactor, 43 smoothing capacitor, 45a to 45f switching elements, 46a to 46f freewheeling diodes, 47 power line, 50 amplifier, 51, 52 resistive element, 60 thermal shutdown (TSD) circuit, 61 bipolar transistor, 62 to 64 resistive element, Ur, Vr, Wr winding.

Claims

1. a power conversion circuit that converts power input from a power source via a power line into power to be supplied to a load; an active noise cancellation circuit that outputs a cancellation current to the power supply line to reduce noise flowing from the power conversion circuit to the power supply line; and The active noise cancellation circuit an input circuit including a detection passive element that is a passive element that detects the noise flowing in the power supply line; an output circuit including an injection passive element that is a passive element that injects the cancel current into the power supply line; an amplifier circuit that generates the canceling current corresponding to the noise detected by the input circuit and outputs the generated canceling current to the power supply line via the output circuit; a protection unit that reduces the cancel current when the temperature rises, the protection unit is one or both of the detection passive element and the injection passive element, the protection unit has a positive temperature characteristic in which impedance increases as the temperature increases; Power conversion device.

2. The protection section has an impedance at 80°C that is at least twice as large as the impedance at 20°C. The power conversion device according to claim 1 .

3. The protection unit is a thermistor whose resistance value increases as the temperature increases. The power conversion device according to claim 1 or 2.

4. The protective part is a coil whose magnetic permeability increases as the temperature increases. The power conversion device according to claim 1 or 2.

5. the protection unit is a capacitor whose dielectric constant decreases as the temperature increases; The power conversion device according to claim 1 or 2.

6. a refrigerant circuit including a compressor; The power conversion device according to claim 1 or 2, which supplies electric power to the compressor to drive an electric motor of the compressor; A refrigeration cycle device comprising: