Noise suppression circuit and air conditioner

Abstract

Provided is a technique capable of suppressing breakdown of a semiconductor element of a noise suppression circuit. A power conversion system 1 according to an embodiment of the present disclosure comprises: an amplifier circuit 62 that includes an operational amplifier 621 to which a detection signal, which is output from a noise detection means 50 for detecting common mode noise of a propagation path including a power line PL1 connecting an AC power supply 10 and a power conversion device 30, or a signal derived from the detection signal is input, and outputs a signal representing the waveform of a compensation current or a compensation voltage for suppressing the common mode noise on the basis of the signal input to the operational amplifier 621; a compensation circuit 63 that outputs the compensation current or the compensation voltage to the propagation path on the basis of the output of the amplifier circuit 62; and a circuit breaker 67 that is provided on the signal line between the noise detection means 50 and the operational amplifier 621 and blocks the input of the detection signal or the signal derived from the detection signal from the noise detection means 50 to the amplifier circuit 62.

Description

Noise suppression circuits, air conditioners

[0001] The present disclosure relates to noise suppression circuits and the like.

[0002] Conventionally, a noise suppression technique has been known that detects common-mode noise and outputs a compensating current or voltage to a path through which the detected common-mode noise flows, thereby reducing the common-mode noise (see, for example, Patent Document 1).

[0003] Patent No. 3044650

[0004] However, for example, if a detection signal from the common mode noise detection means or a signal derived from that detection signal is applied to a semiconductor element of the noise suppression circuit when there is no power supply from the drive power supply to the noise suppression circuit, the semiconductor element may be destroyed.

[0005] An object of the present disclosure is to provide a technique capable of suppressing damage to semiconductor elements in a noise suppression circuit.

[0006] A first aspect of the present disclosure provides a noise suppression circuit comprising: a generation circuit including a semiconductor element to which a detection signal output from a detection means for detecting common mode noise in a propagation path including a power line connecting a first electric device and a second electric device, or a signal derived from the detection signal, is input, and which outputs a signal representing a waveform of a compensation current or a compensation voltage for suppressing the common mode noise based on the signal input to the semiconductor element; a compensation circuit which outputs the compensation current or the compensation voltage to the propagation path based on the output of the generation circuit; and a blocking means provided on a signal line between the detection means and the semiconductor element, which blocks the input of the detection signal from the detection means to the generation circuit.

[0007] According to this aspect, the noise suppression circuit can, for example, by shutting off the cutoff means when there is no power supply from the drive power supply to the noise suppression circuit, shut off the input of the detection signal from the detection means to the semiconductor element of the generation circuit and the signal derived from the detection signal, thereby preventing damage to the semiconductor element of the generation circuit when there is no power supply from the drive power supply to the noise suppression circuit.

[0008] Furthermore, in a second aspect of the present disclosure, based on the first aspect described above, the blocking means may block the input of the detection signal from the detection means to the generation circuit when a voltage equal to or greater than the drive voltage is not applied to the generation circuit.

[0009] Furthermore, in a third aspect of the present disclosure, based on the second aspect described above, the blocking means may pass the detection signal from the detection means to the generation circuit when a voltage equal to or greater than the drive voltage is applied to the generation circuit.

[0010] Furthermore, in a fourth aspect of the present disclosure, based on any one of the first to third aspects described above, the semiconductor element may be an operational amplifier.

[0011] In addition, in a fifth aspect of the present disclosure, based on any one of the first to third aspects described above, the semiconductor element may be a microcomputer.

[0012] Furthermore, in a sixth aspect of the present disclosure, based on the second or third aspect described above, the drive voltage may be a minimum value in a range of power supply voltages for the semiconductor element.

[0013] Furthermore, in a seventh aspect of the present disclosure, based on the third aspect described above, the blocking means may switch between a state in which the detection signal is passed and a state in which the detection signal is blocked depending on the presence or absence of a signal corresponding to the voltage applied to the generation circuit being equal to or higher than the drive voltage.

[0014] In addition, in an eighth aspect of the present disclosure, based on any one of the first to seventh aspects described above, the first electric device may be an AC power supply, and the second electric device may be a power conversion device.

[0015] In addition, in a ninth aspect of the present disclosure, based on any one of the first to seventh aspects described above, the first electric device may be a power conversion device, and the second electric device may be a motor.

[0016] In addition, in a tenth aspect of the present disclosure, based on the eighth or ninth aspect described above, the power conversion device may include a switching element, and a wide bandgap semiconductor may be used for the switching element.

[0017] An eleventh aspect of the present disclosure provides an air conditioner including the noise suppression circuit according to any one of the first to tenth aspects.

[0018] According to the above-described embodiment, it is possible to prevent damage to the semiconductor elements of the noise suppression circuit.

[0019] It is a diagram showing an example of a power conversion system.It is a diagram showing another example of a power conversion system.It is a diagram showing an example of a refrigerant circuit of an air conditioner.

[0020] Hereinafter, an embodiment will be described with reference to the drawings.

[0021] [Configuration of an Example of a Power Conversion System] With reference to FIG. 1, a configuration of an example of a power conversion system 1 according to this embodiment will be described.

[0022] FIG. 1 is a diagram illustrating an example of a power conversion system 1. As shown in FIG.

[0023] As shown in FIG. 1 , a power conversion system 1 drives a motor 20 using power supplied from an AC power supply 10 .

[0024] The AC power supply 10 supplies AC to the power conversion system 1. In this example, the AC power supply 10 supplies three-phase AC, i.e., R-phase, S-phase, and T-phase, to the power conversion system 1.

[0025] The motor 20 is driven by the three-phase AC output from the power conversion system 1. The motor 20 is, for example, a DC (Direct Current) brushless motor. Alternatively, the motor 20 may be a motor driven by another three-phase AC.

[0026] The power conversion system 1 includes a power line PL1 , a power line PL2 , a power conversion device 30 , a noise filter 40 , a noise detection means 50 , an active noise canceller 60 , and a drive power supply 70 .

[0027] Power line PL1 electrically connects AC power supply 10 and power conversion device 30 by three power lines of R phase, S phase, and T phase. Power line PL1 includes power lines PL11 to PL13.

[0028] The power line PL2 electrically connects the power conversion device 30 and the motor 20 by three power lines of U-phase, V-phase, and W-phase.

[0029] The power line PL11 connects the AC power supply 10 and the coil 51 by three power lines of R phase, S phase, and T phase. The power line PL12 connects the coil 51 and the common mode choke coil 41 of the noise filter 40 by three power lines of R phase, S phase, and T phase. The power line PL13 connects the common mode choke coil 41 and the power conversion device 30 by three power lines of R phase, S phase, and T phase.

[0030] The power conversion device 30 converts the AC supplied through the power line PL1 into three-phase AC of a predetermined frequency and a predetermined voltage, and outputs the converted AC to the motor 20 through the power line PL2, thereby driving the motor 20.

[0031] The power conversion device 30 includes, for example, a power conversion circuit 30C including a rectifier circuit 31 and an inverter circuit 32 , and a control circuit 33 .

[0032] The rectifier circuit 31 converts three-phase AC of R phase, S phase, and T phase supplied through the power line PL13 into DC and outputs the DC to a DC (Direct Current) link (also referred to as a "direct current link"). The rectifier circuit 31 is, for example, a three-phase full-wave rectifier circuit using diodes.

[0033] The inverter circuit 32 converts the direct current input from the DC link between the rectifier circuit 31 and itself into three-phase alternating current of a predetermined frequency and a predetermined voltage, specifically, alternating current of U-phase, V-phase, and W-phase, and outputs the converted direct current. The inverter circuit 32 includes, for example, switching elements, and converts the direct current into three-phase alternating current of a predetermined frequency and a predetermined voltage through the switching operation of the switching elements, and outputs the converted three-phase alternating current to the power line PL2.

[0034] The switching element is, for example, an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a high electron mobility transistor (HEMT). The switching element is, for example, mainly made of silicon (Si). The switching element may also be, for example, mainly made of a wide bandgap semiconductor material. The wide bandgap semiconductor material is, for example, silicon carbide (SiC), gallium nitride (gallium nitride), or gallium oxide (GaO). ２ O ３ ), carbon (diamond: C), etc. In addition to the switching element, the inverter circuit 32 may include a semiconductor freewheel diode connected in parallel with the switching element.

[0035] The control circuit 33 performs control processing related to the power conversion circuit 30C.

[0036] The control circuit 33 may also perform other processes related to the power conversion system 1 .

[0037] For example, the control circuit 33 performs processing for diagnosing an abnormality in the active noise canceller 60 (hereinafter referred to as "abnormality diagnosis"). The abnormality diagnosis includes, for example, diagnosing the presence or absence of an abnormality. The abnormality diagnosis may also include diagnosing the presence or absence of signs of an abnormality and diagnosing the degree of the abnormality (abnormality level).

[0038] The functions of the control circuit 33 may be realized by only the hardware (circuit) of the hardware and software, or may be realized by a combination of hardware (for example, an integrated circuit (IC)) and software. In the latter case, for example, the control circuit 33 is mainly configured with a microcomputer including a CPU (Central Processing Unit), a memory device, an auxiliary storage device, an input / output interface, etc.

[0039] The noise filter 40 is a passive noise suppression device that suppresses common mode noise.

[0040] Common mode noise is generated in association with the switching operation of the switching elements of the inverter circuit 32. Specifically, common mode noise is generated when noise accompanying the switching operation of the switching elements leaks to the ground GL through the stray capacitance of the motor 20 or the stray capacitance between the switching elements (not shown) of the power conversion device 30 and the heat sink.

[0041] The noise filter 40 includes a common mode choke coil 41 and a Y capacitor 42 .

[0042] The common mode choke coil 41 acts as an inductor to suppress a common mode noise current (common mode current) flowing through the power line PL1.

[0043] The Y capacitor 42 has a function of returning the common mode current that has flowed out to the ground GL to the inverter circuit 32, which is a noise source. One end of the Y capacitor 42 is connected to the power line PL13, and the other end is connected to the ground GL.

[0044] The ground GL is earthed, for example, the housing of a device including the power conversion system 1. Alternatively, the ground GL may be a dedicated reference potential line.

[0045] The noise detection means 50 detects a common mode noise current (common mode current) or a noise voltage (common mode voltage). For example, as shown in Fig. 1, the noise detection means 50 detects a common mode current in the power line PL1. The noise detection means 50 includes a primary circuit including a coil 51 and a secondary circuit including a coil 52.

[0046] The coils 51 are provided for the R-phase, S-phase, and T-phase of the power line PL1, respectively.

[0047] Coil 52 is provided so as to be magnetically coupled to coil 51. Coil 52 outputs a detection signal corresponding to common mode noise on power line PL1.

[0048] Coils 51 and 52 are wound around the same magnetic core and are arranged to have opposite polarities, as indicated by the dots "." in Fig. 1. The magnetic core around which coils 51 and 52 are wound is, for example, a toroidal core, and the magnetic material is, for example, ferrite or permilo. For example, when current flows to the right in coil 51 in the figure, current flows to the left in coil 52. In other words, the polarity indicated by the dots "." in Fig. 1 corresponds to the direction in which current flows.

[0049] For example, when a common mode current flows through the coil 51, a current proportional to the common mode current is induced in the coil 52. As a result, the coils 51 and 52 function as a current detection transformer that detects the common mode current. The noise detection unit 50 may also detect common mode noise from the ground GL.

[0050] The active noise canceller 60 outputs a compensation current or a compensation voltage for suppressing common mode noise to the power line PL1, the power line PL2, or the ground GL based on the detection signal output from the coil 52 of the noise detection means 50. The active noise canceller 60 includes a noise suppression circuit 60C including a filter circuit 61, an amplifier circuit 62, a compensation circuit 63, an output unit 64, a power supply circuit 65, a coupling capacitor 66, and a circuit breaker 67, and a control circuit 68.

[0051] The filter circuit 61 passes a detection signal output from the coil 52 after removing specific frequency components from the detection signal. The output signal from the filter circuit 61 is input to the amplifier circuit 62 .

[0052] The amplifier circuit 62 amplifies the signal output from the filter circuit 61. The amplifier circuit 62 includes, for example, an operational amplifier 621 as a semiconductor element (semiconductor device).

[0053] The power supply voltage of the operational amplifier 621 is, for example, ⅔ or less of the DC link voltage (DC link voltage) Vdc of the power conversion circuit 30C. Because the voltage Vcom of the common-mode noise source (specifically, the potential of the neutral point of the motor 20 generated when the motor 20 is driven by the inverter circuit 32) changes by ⅓, if the power supply voltage of the operational amplifier 621 is within a range of ±⅓ of the DC link voltage Vdc, it is possible to cancel out the common-mode noise caused by the switching operation of the inverter circuit 32 without considering the relationship between the voltage Vcc and the impedance.

[0054] The signal output from the amplifier circuit 62 is a signal representing the waveform of the compensation current or compensation voltage, and is input to the compensation circuit 63. The signal representing the waveform of the compensation current or compensation voltage is a signal indicating the amplitude and phase for each frequency of the waveform of the compensation current or compensation voltage output from the compensation circuit 63. For example, the signal representing the waveform of the compensation current or compensation voltage output from the amplifier circuit 62 is a current or voltage waveform signal that has the same phase for each frequency as the waveform of the compensation current or compensation current output from the compensation circuit 63 and a smaller amplitude.

[0055] The compensation circuit 63 amplifies the signal output from the amplifier circuit 62 and outputs a compensation current or a compensation voltage. The compensation circuit 63 includes transistors Tr1 and Tr2 and diodes D1 and D2.

[0056] The transistor Tr1 is connected between one end of the drive power supply 70 and the output capacitor Co of the output section 64. The transistor Tr2 is connected between the other end of the drive power supply 70 and the output capacitor Co of the output section 64.

[0057] 1, in this example, the transistor Tr1 is a PNP type, the transistor Tr2 is an NPN type, and the transistors Tr1 and Tr2 have opposite polarities to each other. As a result, the transistors Tr1 and Tr2 form a push-pull circuit, which functions as an amplifier.

[0058] The bases of the transistors Tr1 and Tr2 are connected to one end of the coil 52 via an amplifier circuit 62 and a filter circuit 61, and the interconnection point of the transistors Tr1 and Tr2 is connected to the other end of the coil 52 via the amplifier circuit 62 and the filter circuit 61. This causes the transistors Tr1 and Tr2 to perform operations inverse to each other.

[0059] Diodes D1 and D2 are connected in antiparallel to the transistors Tr1 and Tr2, respectively, to protect them.

[0060] The output unit 64 connects the compensation circuit 63 to the ground GL, and outputs (also referred to as "injecting") the compensation current or compensation voltage output from the compensation circuit 63 to a path through which the common mode current flows. The output unit 64 includes an output capacitor Co.

[0061] One end of the output capacitor Co is connected to the interconnection point of the transistors Tr1 and Tr2 of the compensation circuit 63, and the other end is connected to the ground GL.

[0062] The power supply circuit 65 is connected to a drive power supply 70. The power supply circuit 65 includes capacitors C1 and C2.

[0063] The capacitors C1 and C2 are connected in series. The series connection of the capacitors C1 and C2 is connected in parallel with the drive power supply 70 and the compensation circuit 63. The midpoint between the capacitors C1 and C2 is connected to the coupling capacitor 66.

[0064] Coupling capacitor 66 has one end connected to power line PL12 and the other end connected to the midpoint between capacitors C1 and C2.

[0065] The circuit breaker 67 is provided on the signal line between the noise detection means 50 and the filter circuit 61. The circuit breaker 67 can switch between a connection state that passes a detection signal from the noise detection means 50 to the filter circuit 61 via the signal line and a cut-off state that cuts off the detection signal. The circuit breaker 67 is, for example, a relay. Alternatively, the circuit breaker 67 may be a semiconductor switch.

[0066] The circuit breaker 67 is in a cut-off state, for example, when power is not being supplied from the drive power supply 70 to the amplifier circuit 62 of the active noise canceller 60. This makes it possible to prevent a situation in which, for example, a signal output from the noise detection means 50 passes through the filter circuit 61 and the signal that has passed through the filter circuit 61 is input to the operational amplifier 621 of the amplifier circuit 62 when power is not being supplied to the amplifier circuit 62. This makes it possible to prevent a situation in which a signal is applied to the operational amplifier 621 based on the signal output from the noise detection means 50 when power is not being supplied to the operational amplifier 621, thereby destroying the operational amplifier 621. A situation in which power is not being supplied from the drive power supply 70 to the amplifier circuit 62 and compensation circuit 63 of the active noise canceller 60 occurs, for example, when the power supply to the active noise canceller 60 is not turned on.

[0067] The control circuit 68 performs control processing related to the active noise canceller 60 .

[0068] The control circuit 68 may also perform processing for diagnosing abnormalities in the active noise canceller 60 .

[0069] The functions of the control circuit 68 may be realized by only the hardware (circuit) of the hardware and software, or may be realized by a combination of hardware (for example, an integrated circuit) and software, etc. In the latter case, for example, the control circuit 68 is configured mainly by a microcomputer including a CPU, a memory device, an auxiliary storage device, an input / output interface, etc.

[0070] The drive power supply 70 supplies DC drive power to the active noise canceller 60 .

[0071] The drive power supply 70 may be a DC power supply that can supply DC to the active noise canceller 60 on its own, or may be, for example, a capacitor that uses the DC voltage of the DC link between the rectifier circuit 31 and the inverter circuit 32 of the power conversion circuit 30C as its power source.

[0072] [Configuration of Second Example of Power Conversion System] Next, a configuration of a second example of the power conversion system 1 will be described with reference to FIG.

[0073] Hereinafter, in this example, the same symbols are used for configurations that are the same as or correspond to those in the first example described above, and the explanation will focus on the parts that are different from the first example described above, and explanations of the parts that are the same as or correspond to those in the first example described above may be omitted.

[0074] FIG. 2 is a diagram illustrating a second example of the power conversion system 1. As shown in FIG.

[0075] As shown in FIG. 2, the power conversion system 1 according to this embodiment differs from the first embodiment mainly in that a generating circuit 62A is provided instead of the amplifier circuit 62.

[0076] The generating circuit 62A is connected to the filter circuit 61 via a signal line, and receives a signal output from the filter circuit 61. The generating circuit 62A outputs a compensation current or a signal representing the waveform of the compensation current based on the signal input from the filter circuit 61, for example, by software processing. The signal output from the generating circuit 62A is input to the compensation circuit 63. The generating circuit 62A includes, for example, a microcomputer 621A as a semiconductor element (semiconductor device).

[0077] The power supply voltage of the microcomputer 621A is, for example, ⅔ or less of the DC link voltage Vdc of the power conversion circuit 30C (DC link voltage).

[0078] In this way, in this example, the power conversion system 1 can use the microcomputer 621A to generate a signal representing the waveform of the compensation current or compensation voltage and input it to the compensation circuit 63.

[0079] [Operation of Active Noise Canceller] Next, the operation of the active noise canceller 60 will be described with reference to FIGS.

[0080] In the following, for simplicity, the present example will be described ignoring the effect of the noise filter 40 in suppressing the common-mode current Ic.

[0081] The noise detection means 50 detects common mode noise on the power line PL1 and drives the transistors Tr1 and Tr2 via a filter circuit 61 and an amplifier circuit 62 or a generator circuit 62A. Specifically, when a detection signal output from the coil 52 of the noise detection means 50 is input to the bases of the transistors Tr1 and Tr2 via the filter circuit 61 and the amplifier circuit 62 or the generator circuit 62A, the detection signal is amplified by the transistors Tr1 and Tr2.

[0082] 1 , transistor Tr1 is turned on. In this case, compensation current Io is supplied from drive power supply 70 and flows through a path connecting the positive terminal of drive power supply 70 to the negative terminal of drive power supply 70 via capacitor C2, coupling capacitor 66, AC power supply 10, output capacitor Co, and transistor Tr1. As a result, compensation current Io is subtracted from common mode current Ic, and a reduced common mode current Ig flows through AC power supply 10.

[0083] Furthermore, when the common mode current Ic flows in the direction opposite to the direction of the arrow in Fig. 1, the transistor Tr2 is turned on. In this case, the compensation current Io is supplied from the drive power supply 70 and flows through a current path that connects the positive terminal of the drive power supply to the negative terminal of the drive power supply 70, via the transistor Tr2, the output capacitor Co, the AC power supply 10, the coupling capacitor 66, and the capacitor C1. In other words, the compensation current Io flows in the direction opposite to the direction of the arrow in Fig. 1. As a result, the compensation current Io is subtracted from the common mode current Ic, and a reduced common mode current Ig flows in the direction opposite to the direction of the arrow in Fig. 1 to the AC power supply 10.

[0084] As described above, the compensation current Io flows through the compensation circuit 63. Therefore, when a compensation current or a compensation voltage is output, the current supplied from the drive power supply 70 is larger in the compensation circuit 63 than in the amplifier circuit 62 or the generation circuit 62A.

[0085] In this way, the active noise canceller 60 outputs the compensation current Io to the path through which the common mode current Ic flows, thereby suppressing the common mode current Ig flowing through the AC power supply 10. Therefore, for example, the active noise canceller 60 can suppress a situation in which the common mode noise current flows out to and affects peripheral devices through the AC power supply 10.

[0086] [Method of Switching Between Connected State and Disconnected State of Circuit Breaker] Next, a method of switching between the connected state and disconnected state of the circuit breaker 67 will be described.

[0087] The circuit breaker 67 is switched from a connected state to a disconnected state in response to, for example, an externally input signal. Alternatively, the circuit breaker 67 may be switched from a disconnected state to a connected state in response to an externally input signal.

[0088] For example, the control circuit 68 monitors whether or not power is being supplied from the drive power supply 70 to the amplifier circuit 62 and the generation circuit 62A. Specifically, the control circuit 68 may monitor the voltage applied to the active noise canceller 60 from the drive power supply 70, and determine that power is being supplied if the applied voltage is equal to or greater than a predetermined drive voltage, and determine that power is not being supplied if the applied voltage is less than the predetermined drive voltage. The predetermined drive voltage may be, for example, the minimum value of the range of the power supply voltage of the operational amplifier 621 and the microcomputer 621A. When the amplifier circuit 62 and the generation circuit 62A transition from a state in which power is being supplied from the drive power supply 70 to a state in which power is not being supplied, the control circuit 68 may output a control command to the circuit breaker 67 to switch the circuit breaker 67 from a connected state to a disconnected state. As a result, the circuit breaker 67 automatically interrupts the input of the detection signal from the noise detection means 50 to the filter circuit 61 in accordance with the transition to a state in which power is not being supplied to the amplifier circuit 62 and the generation circuit 62A, and maintains that state. Furthermore, when the amplifier circuit 62 and the generation circuit 62A transition from a state where no power is supplied from the drive power supply 70 to a state where power is being supplied, the control circuit 68 may output a control command to the circuit breaker 67 to cause the circuit breaker 67 to transition from a disconnected state to a connected state. This allows the circuit breaker 67 to automatically return to a state where it passes a detection signal from the noise detection means 50 to the filter circuit 61, in line with the transition to a state where power is being supplied to the amplifier circuit 62 and the generation circuit 62A.

[0089] In addition, when the voltage applied to the amplifier circuit 62 or the generation circuit 62A is equal to or greater than the drive voltage, a signal corresponding to the voltage applied to the amplifier circuit 62 or the generation circuit 62A being equal to or greater than a predetermined drive voltage may be input to the circuit breaker 67.

[0090] The signal corresponding to the voltage applied to the amplifier circuit 62 or the generator circuit 62A being equal to or greater than a predetermined drive voltage is, for example, an H (High) signal output from a comparator that compares the applied voltage of the amplifier circuit 62 or the generator circuit 62A with a reference voltage corresponding to the predetermined drive voltage. Specifically, the comparator receives the applied voltage of the amplifier circuit 62 or the generator circuit 62A, and outputs an H (High) signal when the input voltage is equal to or greater than the reference voltage, and outputs an L (Low) signal when the input voltage is less than the reference voltage. This allows the circuit breaker 67 to switch between a connected state and a disconnected state such that the circuit breaker 67 is in a connected state when an H signal is input from the comparator, and in a disconnected state when an H signal is not input from the comparator (i.e., when an L signal is input).

[0091] Furthermore, there are cases where the power-on (i.e., activation) and power-off (i.e., shutdown) of the power conversion device 30 are linked to the power-on (activation) and power-off (shutdown) of the active noise canceller 60. For example, as described above, this is the case when the drive power supply 70 uses the DC link voltage of the power conversion circuit 30C. In this case, the circuit breaker 67 may transition from the disconnected state to the connected state in response to the power-on of the power conversion device 30, and transition from the connected state to the disconnected state in response to the power-off of the power conversion device 30. For example, the circuit breaker 67 transitions from the connected state to the disconnected state in response to a control command input from the control circuit 33 of the power conversion device 30 via a predetermined communication line in response to the power-off of the power conversion device 30. Furthermore, the circuit breaker 67 may transition from the disconnected state to the connected state in response to a control command input from the control circuit 33 of the power conversion device 30 in response to the power-on of the power conversion device 30.

[0092] Furthermore, the circuit breaker 67 may be manually switched between a connected state and a disconnected state by a user, worker, or the like who can confirm whether the voltage applied to the amplifier circuit 62 or the generation circuit 62A is equal to or greater than the drive voltage. For example, a user, worker, or the like of the power conversion system 1 may manually switch the circuit breaker 67 from a connected state to a disconnected state upon confirming that the voltage applied to the amplifier circuit 62 or the generation circuit 62A has transitioned from a state where it is equal to or greater than the drive voltage to a state where it is not equal to or greater than the drive voltage. For example, a user, worker, or the like can confirm that, by shutting off the power supply to the active noise canceller 60, the voltage applied to the amplifier circuit 62 or the generation circuit 62A has transitioned from a state where it is equal to or greater than the drive voltage to a state where it is not equal to or greater than the drive voltage. Similarly, a user, worker, or the like may manually switch the circuit breaker 67 from a disconnected state to a connected state upon confirming that the voltage applied to the amplifier circuit 62 or the generation circuit 62A has transitioned from a state where it is not equal to or greater than the drive voltage to a state where it is equal to or greater than the drive voltage. For example, a user or worker can confirm that when the active noise canceller 60 is powered on, the voltage applied to the amplifier circuit 62 and the generation circuit 62A has transitioned from a state where it is equal to or greater than the drive voltage to a state where it is not equal to or greater than the drive voltage.

[0093] As described above, in this example, the circuit breaker 67 can automatically or manually switch between a connected state and a disconnected state depending on whether a voltage equal to or greater than the drive voltage is being applied to the amplifier circuit 62 or the generation circuit 62A. Therefore, the circuit breaker 67 can maintain the disconnected state when a voltage equal to or greater than the drive voltage is not being applied to the amplifier circuit 62 or the generation circuit 62A. Therefore, the circuit breaker 67 can prevent a situation in which a signal is input from the filter circuit 61 to the operational amplifier 621 or the microcomputer 621A and the operational amplifier 621 or the microcomputer 621A is damaged when a voltage equal to or greater than the drive voltage is not being applied to the amplifier circuit 62 or the generation circuit 62A.

[0094] [Another Example of Power Conversion System] Next, another example of the power conversion system 1 will be described.

[0095] The configuration, operation, etc. of the power conversion system 1 according to the above-described embodiment may be modified or changed as appropriate. Hereinafter, examples in which the configuration, operation, etc. of the power conversion system 1 according to the above-described embodiment are modified or changed will be referred to as "variant examples" for convenience.

[0096] For example, in the power conversion system 1 of the above-described embodiment, the AC power supply 10 may supply single-phase AC to the power conversion system 1 instead of three-phase AC.

[0097] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the power conversion circuit 30C may be provided in the DC link between the rectifier circuit 31 and the inverter circuit 32 and may have a smoothing circuit including a smoothing capacitor, a smoothing inductor, etc.

[0098] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the functions of the control circuit 33 may be realized by a plurality of circuits. For example, among the functions of the control circuit 33, the function of performing processing for diagnosing an abnormality in the active noise canceller 60 may be realized by a diagnostic circuit separate from the control circuit 33. Furthermore, some or all of the functions of the control circuit 33 may be transferred to outside the power conversion device 30.

[0099] In the power conversion system 1 of the above-described embodiment and its modified examples, the noise filter 40 may be omitted.

[0100] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the coil 51 may be omitted, and the harness corresponding to the power line PL1 may simply be inserted into the toroidal core around which the coil 52 is wound. In this case, the harness corresponding to the power line PL1 is inserted into the toroidal core with the same polarity as in Fig. 1, specifically, with a polarity such that a current flows in the coil 52 in the opposite direction to the direction of the current flowing in the power line PL1 in the figure.

[0101] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the noise detection means 50 may apply a known method (see, for example, Japanese Patent No. 5,528,543 and Japanese Patent No. 7,309,067) to detect common-mode noise via a capacitor.

[0102] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the noise detection means 50 may include the function of the filter circuit 61. In this case, the filter circuit 61 is omitted, and the filter circuit in the noise detection means 50 outputs a detection signal from which specific frequency components have been removed, and the detection signal is input to the operational amplifier 621 of the amplifier circuit 62 and the microcomputer 621A of the generation circuit 62A.

[0103] In the power conversion system 1 of the above-described embodiment and its modified examples, the filter circuit 61 may be omitted. In this case, the detection signal output from the noise detection means 50 is input to the operational amplifier 621 of the amplifier circuit 62 and the microcomputer 621A of the generation circuit 62A.

[0104] In the second example of the power conversion system 1 of the above-described embodiment and its modified example, the function of the generating circuit 62A may be realized by the control circuit 68 including a microcomputer. In this case, the generating circuit 62A is omitted.

[0105] Furthermore, in the power conversion system 1 of the above-described embodiment and its modifications, the functions of the amplifier circuit 62 and the generation circuit 62A may be transferred to outside the active noise canceller 60. In this case, the amplifier circuit 62 and the generation circuit 62A are omitted. For example, a detection signal from the noise detection means 50 or a signal output from the filter circuit 61 is input to the control circuit 33 of the power conversion device 30 via a predetermined communication line. Then, the control circuit 33 generates a signal representing the waveform of a compensation current or a compensation voltage based on the input signal and transmits it to the active noise canceller 60 via the predetermined communication line. The signal representing the waveform of the compensation current or the compensation voltage is input to the compensation circuit 63.

[0106] In the power conversion system 1 of the above-described embodiment and its modified example, the diodes D1 and D2 of the compensation circuit 63 may be omitted.

[0107] In the power conversion system 1 of the above-described embodiment and its modified examples, either the amplifier circuit 62 or the compensation circuit 63 may be omitted.

[0108] In the power conversion system 1 of the above-described embodiment and its modified examples, the output unit 64 may have, in addition to the output capacitor Co, a resistor connected in series thereto.

[0109] In the power conversion system 1 of the above-described embodiment and its modified examples, the output capacitor Co of the output unit 64 may be omitted. In this case, the output unit 64 may connect the compensation circuit 63 to the ground GL via a resistor, or may connect the compensation circuit 63 directly to the ground GL.

[0110] In the power conversion system 1 of the above-described embodiment and its modifications, the output unit 64 may be configured to output a compensation current or a compensation voltage to the power line PL12.

[0111] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the output unit 64 may apply a known method (see, for example, Japanese Patent No. 5528543 or Japanese Patent No. 7309067) to output a compensation current or a compensation voltage to the power line PL1 by magnetic coupling. In this case, the output unit 64 includes a primary coil that is magnetically coupled to a harness corresponding to the power line PL1 or the ground GL, and a toroidal core around which the primary coil is wound, and the harness corresponding to the power line PL1 or the ground GL is inserted through the toroidal core. Furthermore, the harness corresponding to the power line PL1 or the ground GL may have a coil wound around the toroidal core.

[0112] Furthermore, in the power conversion system 1 of the above-described embodiment and its modified examples, the output unit 64 may apply a known method (see, for example, Japanese Patent No. 5248713) to output a compensation current or a compensation voltage to the power line PL1 via a capacitor. In this case, the output unit 64 includes a capacitor having one terminal connected to the power line PL1 and an impedance having one terminal grounded and the other terminal connected to the other terminal of the capacitor, and the output line of the compensation circuit 63 is connected to the midpoint between the capacitor and the impedance.

[0113] In the power conversion system 1 of the above-described embodiment and its modified examples, the circuit breaker 67 may be provided in a signal line between the filter circuit 61 and the amplifier circuit 62 or the generation circuit 62A. The circuit breaker 67 may also be provided in a signal line upstream of the operational amplifier 621 in the amplifier circuit 61 or a signal line upstream of the microcomputer 621A in the generation circuit 62A. Specifically, for example, the amplifier circuit 61 includes, in addition to the operational amplifier 621, other components (e.g., an impedance circuit for increasing the input impedance of the operational amplifier 621) provided upstream of the operational amplifier 621, and the circuit breaker 67 is provided in a signal line between the other upstream circuit and the operational amplifier 621. Similarly, for example, the generation circuit 62A includes, in addition to the microcomputer 621A, other circuits provided upstream of the microcomputer 621A, and the circuit breaker 67 is provided in a signal line between the other circuits and the operational amplifier 621. That is, the circuit breaker 67 may be appropriately arranged on the signal line between the noise detection means 50 (specifically, the coil 52) and the operational amplifier 621 in the amplifier circuit 62 or the microcomputer 621A in the generation circuit 62A.

[0114] Furthermore, in the power conversion system 1 of the above-described embodiment and its modifications, the active noise canceller 60 may be provided so that the compensation current Io flows between the DC link of the power conversion circuit 30C and the ground GL. For example, as described above, when the drive power supply 70 uses the DC voltage of the DC link of the power conversion circuit 30C, the compensation current Io flows between the DC link and the ground GL through the power path. In this case, the noise detection means 50 may be provided so as to detect common-mode noise on the power line PL1, or so as to detect common-mode noise in the DC link of the power conversion circuit 30C.

[0115] Furthermore, in the power conversion system 1 of the above-described embodiment and its modifications, the active noise canceller 60 may be provided so that the compensation current Io flows between the power line PL2 between the power conversion device 30 and the motor 20 and the ground GL. For example, one end of the coupling capacitor 66 is connected to each of the U-phase, V-phase, and W-phase power lines of the power line PL2. In this case, the noise detection means 50 may be provided so as to detect the common mode noise of the power line PL1 or so as to detect the common mode noise of the power line PL2.

[0116] In the power conversion system 1 of the above-described embodiment and its modified examples, the drive power supply 70 may be included in the active noise canceller 60 .

[0117] [Application Example of Power Conversion System] Next, an application example of the power conversion system 1 according to this embodiment will be described with reference to Fig. 3. Specifically, an air conditioner 100 in which the power conversion system 1 according to this embodiment is mounted will be described.

[0118] FIG. 3 is a diagram showing an example of a refrigerant circuit of the air conditioner 100.

[0119] 3, the air conditioner 100 includes an outdoor unit 110, an indoor unit 120, and refrigerant paths 130 and 140. The air conditioner 100 operates a refrigeration cycle made up of the outdoor unit 110, the indoor unit 120, and the refrigerant paths 130 and 140, etc., to adjust the temperature, humidity, etc., of the room in which the indoor unit 120 is installed.

[0120] The outdoor unit 110 is placed outside a building whose temperature and other conditions are to be regulated. The outdoor unit 110 is connected to one end of each of the refrigerant paths 130 and 140, and draws in refrigerant from one of the refrigerant paths 130 and 140 and discharges the refrigerant to the other.

[0121] The indoor unit 120 is placed in a room of a building whose temperature and other conditions are to be adjusted. The indoor unit 120 is connected to the other end of each of the refrigerant paths 130 and 140, and draws in refrigerant from one of the refrigerant paths 130 and 140 and discharges the refrigerant to the other.

[0122] The refrigerant paths 130 and 140 are, for example, configured by pipes, and connect the outdoor unit 110 and the indoor unit 120 so that the refrigerant can circulate between the outdoor unit 110 and the indoor unit 120 .

[0123] The outdoor unit 110 includes refrigerant paths L1 to L6, oil paths L7 and L8, a four-way switching valve 111, an accumulator 112, a compressor 113, an oil separator 114, an outdoor heat exchanger 115, an outdoor expansion valve 116, and a fan 117.

[0124] The refrigerant paths L1 to L6 are configured as, for example, pipes.

[0125] The refrigerant path L1 connects one end of the refrigerant path 130 outside the outdoor unit 110 to the four-way switching valve 111 .

[0126] The refrigerant path L2 connects the four-way switching valve 111 and the inlet of the compressor 113. The refrigerant path L2 includes refrigerant paths L21 and L22.

[0127] The refrigerant path L21 connects the four-way switching valve 111 and the accumulator 112. The refrigerant path L22 connects the accumulator 112 and the inlet of the compressor 113.

[0128] The refrigerant path L3 connects the four-way switching valve 111 and the outlet of the compressor 113. The refrigerant path L3 includes refrigerant paths L31 and L32.

[0129] The refrigerant path L31 connects the outlet of the compressor 113 and the oil separator 114. The refrigerant path L32 connects the four-way switching valve 111 and the oil separator 114.

[0130] The refrigerant path L4 connects the four-way switching valve 111 and the outdoor heat exchanger 115.

[0131] The refrigerant path L5 connects the outdoor heat exchanger 115 and the outdoor expansion valve 116 .

[0132] The refrigerant path L6 connects one end of the refrigerant path 140 outside the outdoor unit 110 to the outdoor expansion valve 116 .

[0133] The oil path L7 is configured as, for example, a pipe line, and is used to allow the oil separated by the oil separator 114 to flow into the refrigerant path L22 and return the oil to the compressor 113 through the refrigerant path L22.

[0134] The oil passing through the oil path L7 may contain, for example, a liquid refrigerant (hereinafter referred to as "liquid refrigerant"). In other words, not only oil but also liquid refrigerant flows through the oil path L7.

[0135] The oil path L8 is configured as, for example, a pipe line, and is used to allow oil containing liquid refrigerant separated by the accumulator 112 to flow into the refrigerant path L22 and return it to the compressor 113 through the refrigerant path L22.

[0136] The four-way switching valve 111 reverses the flow of circulating refrigerant when the air conditioner 100 is in cooling operation and when it is in heating operation.

[0137] During cooling operation of the air conditioner 100, the four-way switching valve 111 connects the paths indicated by the solid lines in Fig. 3. Specifically, during cooling operation of the air conditioner 100, the four-way switching valve 111 connects refrigerant path L1 to refrigerant path L2, and refrigerant path L3 to refrigerant path L4.

[0138] On the other hand, when the air conditioner 100 is in heating operation, the four-way switching valve 111 connects the paths indicated by the dotted lines in Fig. 3. Specifically, when the air conditioner 100 is in heating operation, the four-way switching valve 111 connects the refrigerant path L4 to the refrigerant path L2, and the refrigerant path L1 to the refrigerant path L3.

[0139] The accumulator 112 separates the liquid refrigerant contained in the refrigerant drawn from the refrigerant path L21 and discharges the refrigerant from which some or all of the liquid refrigerant has been removed to the refrigerant path L22. The liquid refrigerant separated in the accumulator 112 contains oil. The accumulator 112 is provided with an oil discharge port connected to the oil path L8, and the separated oil containing the refrigerant flows out into the oil path L8 through the oil discharge port and is returned to the compressor 113 through the oil path L8 and the refrigerant path L22.

[0140] The compressor 113 is driven by the motor 20, draws in refrigerant from the refrigerant path L22, compresses it to a high pressure, and discharges it into the refrigerant path L31. In this way, the power conversion system 1 can control the operation of the compressor 113 by driving the motor 20.

[0141] During cooling operation of the air conditioner 100, high-temperature, high-pressure refrigerant compressed by the compressor 113 flows into the outdoor heat exchanger 115 via refrigerant paths L3 and L4.

[0142] On the other hand, during heating operation of the air conditioner 100, the high-temperature, high-pressure refrigerant compressed by the compressor 113 flows through refrigerant path L3 and refrigerant path L1 into refrigerant path 130 outside the outdoor unit 110. The high-temperature, high-pressure refrigerant then flows into the indoor unit 120 through refrigerant path 130.

[0143] The oil separator 114 separates oil from the refrigerant flowing in from the refrigerant path L31, and discharges the refrigerant from which some or all of the oil has been separated and removed into the refrigerant path L32. The oil separator 114 is also provided with an oil outlet connected to the oil path L7, and the oil separated from the refrigerant flows into the oil path L7 through the oil outlet and is returned to the compressor 113 through the oil path L7 and the refrigerant path L22.

[0144] The outdoor heat exchanger 115 exchanges heat between the outside air and the refrigerant passing through it. Specifically, the outdoor heat exchanger 115 is provided with a fan 117, and the outdoor heat exchanger 115 exchanges heat between the outside air blown by the fan 117 and the refrigerant flowing through it.

[0145] When the air conditioner 100 is operating in cooling mode, the outdoor heat exchanger 115 causes the high-temperature, high-pressure refrigerant compressed by the compressor 113, which flows in from the refrigerant path L4, to radiate heat to the outside air, and then causes the condensed and liquefied refrigerant (liquid refrigerant) to flow into the refrigerant path L5.

[0146] Furthermore, during heating operation of the air conditioner 100, the outdoor heat exchanger 115 causes the low-temperature, low-pressure liquid refrigerant flowing in from the refrigerant path L5 to absorb heat from the outside air, and causes the evaporated refrigerant to flow into the refrigerant path L4.

[0147] The outdoor expansion valve 116 is closed to a predetermined opening degree during heating operation of the air conditioner 100, and reduces the pressure of the refrigerant (liquid refrigerant) flowing in from refrigerant path L6 to a predetermined pressure. On the other hand, during cooling operation of the air conditioner 100, the outdoor expansion valve 116 is fully open, and allows the refrigerant (liquid refrigerant) to pass from refrigerant path L5 to refrigerant path L6. The outdoor expansion valve 116 is, for example, a solenoid valve.

[0148] The indoor unit 120 includes an indoor expansion valve 121 , an indoor heat exchanger 122 , and a fan 123 .

[0149] During cooling operation of the air conditioner 100, the indoor expansion valve 121 is closed to a predetermined opening degree and reduces the pressure of the supercooled liquid refrigerant flowing in from the refrigerant path 140 to a predetermined pressure. On the other hand, during heating operation of the air conditioner 100, the indoor expansion valve 121 is fully open and allows the refrigerant (liquid refrigerant) flowing out from the indoor heat exchanger 122 to pass toward the refrigerant path 140. The indoor expansion valve 121 is, for example, a solenoid valve.

[0150] The indoor heat exchanger 122 exchanges heat between the indoor air and the refrigerant passing through it. Specifically, the indoor air passes around the indoor heat exchanger 122 by the action of the fan 123 mounted in the indoor unit 120, promoting heat exchange with the refrigerant inside the indoor heat exchanger 122. Then, by the action of the fan 123, the indoor air that has exchanged heat with the refrigerant inside the indoor heat exchanger 122 is sent out to the outside of the indoor unit 120, thereby realizing cooling or heating of the room.

[0151] When the air conditioner 100 is in cooling operation, the indoor heat exchanger 122 causes the low-temperature, low-pressure liquid refrigerant decompressed by the indoor expansion valve 121 to absorb heat from the indoor air, thereby lowering the temperature of the indoor air.

[0152] On the other hand, during heating operation of the air conditioner 100, the indoor heat exchanger 122 causes the high-temperature, high-pressure refrigerant flowing in from the outdoor unit 110 through the refrigerant path 130 to radiate heat to the indoor air, thereby raising the temperature of the indoor air.

[0153] In this way, in this example, the power conversion system 1 according to this embodiment is applied to the air conditioner 100 by being mounted on the air conditioner 100 .

[0154] The power conversion system 1 according to this embodiment may be applied to a refrigeration device other than the air conditioner 100 .

[0155] [Operation] Next, the operation of the noise suppression circuit and the air conditioner according to this embodiment will be described.

[0156] In a first aspect of this embodiment, the noise suppression circuit includes a generation circuit, a compensation circuit, and a cutoff means. The noise suppression circuit is, for example, the noise suppression circuit 60C described above. The generation circuit is, for example, the amplifier circuit 62 or the generation circuit 62A described above. The compensation circuit is, for example, the compensation circuit 63 described above. The cutoff means is, for example, the circuit breaker 67 described above. Specifically, the generation circuit includes a semiconductor element to which the detection signal output from detection means that detects common-mode noise in a propagation path including a power line connecting a first electric device and a second electric device, or a signal derived from the detection signal, is input, and the generation circuit outputs a signal representing a waveform of a compensation current or a compensation voltage for suppressing the common-mode noise based on the signal input to the semiconductor element. The signal representing the waveform of the compensation current or the compensation voltage is a signal that indicates the amplitude and phase for each frequency of the waveform of the compensation current or the compensation voltage output from the compensation circuit. The signal representing the waveform of the compensation current or compensation voltage is, for example, a current or voltage waveform signal having the same phase at each frequency and a smaller amplitude than the compensation current or compensation current waveform output from the compensation circuit. The first electric device and the second electric device may be, for example, the AC power supply 10 and the power conversion device 30 described above, respectively, and the power line may be, for example, the power line PL1 described above. The first electric device and the second electric device may be, for example, the power conversion device 30 and the motor 20 described above, respectively, and the power line may be, for example, the power line PL2 described above. The detection means may be, for example, the noise detection means 50 described above. The semiconductor element may be, for example, the operational amplifier 621 or the microcomputer 621A described above. The signal derived from the detection signal is, for example, a signal output from the filter circuit 61 described above. The compensation circuit outputs the compensation current or the compensation voltage to the propagation path based on the output of the generation circuit. The cutoff means is provided on a signal line between the detection means and the semiconductor element, and cuts off input of the detection signal or a signal derived from the detection signal from the detection means to the generation circuit.

[0157] As a result, when, for example, there is no power supply from the drive power supply to the noise suppression circuit, the cutoff means is brought into a cutoff state, thereby cutting off the input of the detection signal from the detection means and the signal derived from the detection signal to the semiconductor element of the generation circuit, and therefore the noise suppression circuit can suppress damage to the semiconductor element of the generation circuit when there is no power supply from the drive power supply to the noise suppression circuit.

[0158] In addition, in a second aspect of this embodiment, based on the first aspect described above, the blocking means may block the input of the detection signal from the detection means to the generation circuit when a voltage equal to or greater than the drive voltage is not applied to the generation circuit.

[0159] As a result, when it is determined that the generation circuit is not receiving power from the drive power supply, the noise suppression circuit can use the cut-off means to automatically cut off the input of the detection signal from the detection means and the signal derived from that detection signal to the generation circuit.

[0160] Furthermore, in a third aspect of this embodiment, based on the second aspect described above, the blocking means may pass the detection signal from the detection means to the generation circuit when a voltage equal to or greater than the drive voltage is applied to the generation circuit.

[0161] This allows the noise suppression circuit to automatically transition from a state of blocking the input of the detection signal of the detection means and the signal derived from that detection signal to the generation circuit to a state of passing it when it can determine that the generation circuit is receiving power from the drive power supply.

[0162] In a fourth aspect of the present embodiment, based on any one of the first to third aspects, the semiconductor element may be an operational amplifier. The operational amplifier is, for example, the operational amplifier 621 described above.

[0163] This allows the noise suppression circuit to prevent damage to the operational amplifier when no power is supplied to the noise suppression circuit from the drive power supply.

[0164] In addition, in a fifth aspect of the present embodiment, based on any one of the first to fourth aspects, the semiconductor device may be a microcomputer. The microcomputer may be, for example, the microcomputer 621A described above.

[0165] This allows the noise suppression circuit to prevent damage to the microcomputer when power is not supplied to the noise suppression circuit from the drive power supply.

[0166] In addition, in a sixth aspect of this embodiment, on the premise of the second or third aspect described above, the drive voltage may be the minimum value of the range of the power supply voltage of the semiconductor element.

[0167] As a result, when the semiconductor element is not supplied with power at a drive voltage equal to or greater than the minimum value of the power supply voltage range, the noise suppression circuit can use the cut-off means to suppress the input of the detection signal of the detection means and signals derived from that detection signal to the semiconductor element.

[0168] Furthermore, in a seventh aspect of this embodiment, based on the third aspect described above, the blocking means may switch between a state in which the detection signal is passed and a state in which the detection signal is blocked depending on the presence or absence of a signal corresponding to the voltage applied to the generation circuit being equal to or higher than the drive voltage.

[0169] This allows the noise suppression circuit to automatically switch between a state in which the detection signal is passed and a state in which the detection signal is blocked, in conjunction with the voltage applied to the generation circuit.

[0170] In an eighth aspect of the present embodiment, based on any one of the first to seventh aspects, the first electric device may be an AC power supply, and the second electric device may be a power conversion device. The AC power supply is, for example, the AC power supply 10 described above. The power conversion device is, for example, the power conversion device 30 described above.

[0171] As a result, the noise suppression circuit can suppress common mode noise caused by the switching operation of the power conversion device, and can suppress the common mode noise from leaking from the AC power supply to the outside.

[0172] In a ninth aspect of the present embodiment, based on any one of the first to seventh aspects, the first electric device may be a power converter, and the second electric device may be a motor. The power converter is, for example, the power converter 30 described above. The motor is, for example, the motor 20 described above.

[0173] As a result, the noise suppression circuit can suppress common mode noise caused by the switching operation of the power conversion device, and can suppress leakage of common mode noise from the motor to the power supply side through stray capacitance.

[0174] In addition, in a tenth aspect of this embodiment, based on the eighth or ninth aspect described above, the power conversion device may include a switching element, and a wide bandgap semiconductor may be used for the switching element.

[0175] This allows the noise suppression circuit to suppress common mode noise caused by the switching operation of the wide bandgap semiconductor.

[0176] In an eleventh aspect of the present embodiment, an air conditioner may include the noise suppression circuit of any one of the first to tenth aspects described above. The air conditioner is, for example, the air conditioner 100 described above.

[0177] As a result, the noise suppression circuit can be applied to an air conditioner and can suppress common mode noise during operation of the motor that drives the air conditioner.

[0178] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0179] Finally, this application claims priority based on Japanese Patent Application No. 2024-058262, filed on March 29, 2024, the entire contents of which are incorporated herein by reference.

[0180] REFERENCE SIGNS LIST 1 Power conversion system 10 AC power supply 20 Motor 30 Power conversion device 30C Power conversion circuit 31 Rectifier circuit 32 Inverter circuit 33 Control circuit 40 Noise filter 41 Common mode choke coil 42 Y capacitor 50 Noise detection means 51 Coil 52 Coil 60 Active noise canceller 60C Noise suppression circuit 61 Filter circuit 62 Amplifier circuit 62A Generation circuit 63 Compensation circuit 64 Output section 65 Power supply circuit 66 Coupling capacitor 67 Circuit breaker 68 Control circuit 70 Drive power supply 100 Air conditioner 621 Operational amplifier 621A Microcomputer C1, C2 Capacitor Co Output capacitor D1, D2 Diode GL Ground PL1, PL2 Power line PL11, PL12, PL13 Power line Tr1, Tr2 transistors

Claims

1. A noise suppression circuit comprising: a generation circuit (62, 62A) including a semiconductor element (621, 621A) to which a detection signal output from a detection means for detecting common mode noise in a propagation path including a power line (PL1, PL2) connecting a first electric device (10, 30) and a second electric device (30, 20) or a signal derived from the detection signal is input, the generation circuit (62, 62A) outputting a signal representing a waveform of a compensation current or a compensation voltage for suppressing the common mode noise based on the signal input to the semiconductor element (621, 621A); a compensation circuit (63) outputting the compensation current or the compensation voltage to the propagation path based on the output of the generation circuit (62, 62A); and a blocking means (67) provided on a signal line between the detection means and the semiconductor element (621, 621A) for blocking input of the detection signal or a signal derived from the detection signal from the detection means to the generation circuit (62, 62A).

2. The noise suppression circuit according to claim 1, wherein the cutoff means (67) cuts off the input of the detection signal from the detection means to the generation circuit (62, 62A) when a voltage equal to or greater than the drive voltage is not applied to the generation circuit (62, 62A).

3. The noise suppression circuit according to claim 2, wherein the cutoff means (67) passes the detection signal from the detection means to the generation circuit (62, 62A) when a voltage equal to or greater than the drive voltage is applied to the generation circuit (62, 62A).

4. The noise suppression circuit according to any one of claims 1 to 3, wherein the semiconductor element (621, 621A) is an operational amplifier (621).

5. The noise suppression circuit according to any one of claims 1 to 3, wherein the semiconductor element (621, 621A) is a microcomputer (621A).

6. The noise suppression circuit according to claim 2 or 3, wherein the drive voltage is the minimum value of the range of power supply voltages of the semiconductor elements (621, 621A).

7. The noise suppression circuit according to claim 3, wherein the blocking means (67) switches between a state in which the detection signal is passed and a state in which the detection signal is blocked depending on the presence or absence of a signal corresponding to the voltage applied to the generation circuit (62, 62A) being equal to or higher than the drive voltage.

8. The noise suppression circuit according to any one of claims 1 to 7, wherein the first electric device (10, 30) is an AC power supply (10), and the second electric device (30, 20) is a power conversion device (30).

9. The noise suppression circuit according to any one of claims 1 to 7, wherein the first electric device (10, 30) is a power conversion device (30), and the second electric device (30, 20) is a motor (20).

10. The noise suppression circuit according to claim 8 or 9, wherein the power conversion device (30) includes a switching element, and a wide bandgap semiconductor is used for the switching element.

11. An air conditioner comprising a noise suppression circuit (60C) according to any one of claims 1 to 10.

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