Noise reduction device and air conditioning device

Abstract

Improved compensation performance against common mode noise. [Solution] A noise reduction device comprising: a detection circuit (150) connected to an AC power line and detecting common mode noise generated on the power line and on the earth due to the switching operation of a power conversion circuit (30); and a reduction circuit (180) connected to the detection circuit and reducing the common mode noise, wherein the reduction circuit includes a generation unit (60) that generates a compensation signal to reduce the common mode noise based on the output voltage of the detection circuit, and an output unit (70) that outputs the compensation signal to the power line or on the earth, and the detection circuit includes a magnetic body (51) around which a main winding (53), which is part of the power line, is wound, and an auxiliary winding (52) that is wound around the magnetic body, and wherein a voltage determined by the turns ratio of the main winding and the auxiliary winding and an input voltage to the generation unit substantially match in a band of 150 kHz to 1 MHz.

Description

[Technical Field]

[0001] The present disclosure relates to a noise reduction device and an air conditioning device. [Background technology]

[0002] A noise reduction device for a power converter that converts power based on the on / off switching of switching elements is known. This noise reduction device includes a noise detection circuit that detects a common-mode noise current, and a noise compensation current supply circuit that generates a noise compensation current in the opposite direction to the noise current in response to the noise current detected by the noise detection circuit and supplies this noise compensation current to a line through which the noise current of the power converter flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-266677 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional noise reduction device, the noise compensation current supply circuit is connected to the noise detection means, and the output of the noise detection means is input to the noise compensation current supply circuit, thereby performing compensation operation based on the output of the noise detection means. However, depending on the circuit connected to the detection circuit, such as the noise detection means, the frequency characteristics of the output voltage of the detection circuit may deteriorate compared to the theoretical characteristics, and the compensation performance for common-mode noise may deteriorate.

[0005] An object of the present disclosure is to improve compensation performance against common-mode noise. [Means for solving the problem]

[0006] The first aspect is a detection circuit (150) connected to the AC power line (11) and detecting common mode noise generated in the power line and on the earth (12) in response to a switching operation of the power conversion circuit (30); a reduction circuit (180) connected to the detection circuit and configured to reduce the common mode noise; The reduction circuit a generating unit (60) that generates a compensation signal that reduces the common-mode noise based on the output voltage of the detection circuit; an output section (70) that outputs the compensation signal to the power line or the ground, The detection circuit a magnetic body (51) around which main windings (53r, 53s, 53t) that are part of the power lines are wound; an auxiliary winding (52) wound around the magnetic body, This is a noise reduction device in which the voltage (V2) determined by the turn ratio between the main winding and the auxiliary winding and the input voltage (Vd) of the generating unit substantially match in the band of 150 kHz to 1 MHz.

[0007] According to the first aspect, in the frequency band of 150 kHz to 1 MHz, there exists a band in which the input voltage (Vd) of the generating unit substantially coincides with a theoretical voltage (V2) determined by the turns ratio between the main winding and the auxiliary winding. Therefore, even if the reduction circuit (180) is connected to the detection circuit (150), the frequency characteristics of the output voltage of the detection circuit (150) are prevented from deteriorating compared to the theoretical characteristics in the frequency band of 150 kHz to 1 MHz, thereby improving compensation performance against common-mode noise.

[0008] The second aspect is a detection circuit (250) connected to the AC power line (11) and detecting common mode noise generated in the power line and on the earth (12) in response to a switching operation of the power conversion circuit (30); a reduction circuit (280) connected to the detection circuit and configured to reduce the common mode noise; The reduction circuit a generating unit (60) that generates a compensation signal that reduces the common-mode noise based on the output voltage of the detection circuit; an output section (70) that outputs the compensation signal to the power line or the ground, The detection circuit includes an impedance element (55, 56) connected between the power line and the ground; The impedance elements include a first impedance element (55) having one end connected to the power line, and a second impedance element (56) having one end connected to the other end of the first impedance element and the other end connected to the ground, This is a noise reduction device in which the voltage (V2) of the second impedance element, determined by the voltage division ratio between the first impedance element and the second impedance element, and the input voltage (Vd) of the generation unit have a band that approximately matches in the band of 150 kHz or more and 1 MHz or less.

[0009] According to the second aspect, in the band of 150 kHz to 1 MHz, there exists a band in which the input voltage (Vd) of the generating unit substantially coincides with the theoretical voltage (V2) determined by the voltage division ratio of the first impedance element and the second impedance element. Therefore, even if the reduction circuit (280) is connected to the detection circuit (250), the frequency characteristics of the output voltage of the detection circuit (250) are prevented from deteriorating compared to the theoretical characteristics in the band of 150 kHz to 1 MHz, thereby improving the compensation performance for common-mode noise.

[0010] A third aspect is the noise reduction device of the first aspect, The input impedance (Zin1) of the reduction circuit (180) has a band in which the input impedance (Zin1) is higher than the impedance (Z1) of the detection circuit (150) in the range of 150 kHz to 1 MHz, The impedance (Z1) of the detection circuit (150) may be a noise reduction device that is the impedance of the auxiliary winding when wound around the magnetic body.

[0011] According to the third aspect, a decrease in the output voltage of the detection circuit (150) is suppressed in a band where the input impedance (Zin1) of the reduction circuit (180) is higher than the impedance (Z1) of the detection circuit (150). This prevents the frequency characteristics of the output voltage of the detection circuit (150) from deteriorating compared to the theoretical characteristics, thereby improving compensation performance for common-mode noise.

[0012] A fourth aspect is the noise reduction device of the second aspect, The input impedance (Zin2) of the reduction circuit (280) has a band in which the input impedance (Zin2) is higher than the impedance (Z2) of the detection circuit (250) in the range of 150 kHz to 1 MHz, The impedance (Z2) of the detection circuit (250) may be the impedance of the second impedance element, a noise reduction device.

[0013] According to the fourth aspect, a decrease in the output voltage of the detection circuit (250) is suppressed in a band where the input impedance (Zin2) of the reduction circuit (280) is higher than the impedance (Z2) of the detection circuit (250). This prevents the frequency characteristics of the output voltage of the detection circuit (250) from deteriorating compared to the theoretical characteristics, thereby improving compensation performance for common-mode noise.

[0014] A fifth aspect is the noise reduction device of the third or fourth aspect, The reduction circuit includes a filter unit (91, 92) that attenuates a specific frequency component, The filter unit may be a noise reduction device connected between the generating unit and the output unit, between the detection circuit and the generating unit, or between both.

[0015] According to the fifth aspect, noise of a specific frequency component is attenuated, and as a result, part or all of the band of the frequency component can be excluded from the band to be compensated for by the compensation signal, and therefore the generation unit that generates the compensation signal can be simplified or made smaller.

[0016] A sixth aspect is the noise reduction device of the fifth aspect, The filter unit may be a noise reduction device connected between the generation unit and the output unit.

[0017] According to the sixth aspect, the filter unit is connected to the detection circuit via the generation unit, and therefore the effect of the connection of the filter unit on the frequency characteristics of the output voltage of the detection circuit is reduced compared to an embodiment in which the filter unit is directly connected to the detection circuit. Therefore, even if the filter unit is included in the reduction circuit, the frequency characteristics of the output voltage of the detection circuit are prevented from deteriorating from the theoretical characteristics in the frequency band of 150 kHz to 1 MHz, thereby improving compensation performance against common-mode noise.

[0018] A seventh aspect is the noise reduction device of the fifth or sixth aspect, The filter unit may be a noise reduction device that attenuates frequencies that are integer multiples of the switching frequency of the power conversion circuit and that are less than 150 kHz.

[0019] According to the seventh aspect, noise of frequency components that are out of the compensation band and are less than 150 kHz among frequencies that are integer multiples of the switching frequency of the power conversion circuit is attenuated. Because noise at integer multiples of the switching frequency of the power conversion circuit is large, attenuating the noise of frequency components that are out of the compensation band allows for simplification and miniaturization of the generation unit that generates the compensation signal.

[0020] An eighth aspect is the noise reduction device of any one of the fifth to seventh aspects, The noise reduction device includes a noise filter (40) having a common mode choke coil (41) connected to the power line and a capacitor (42) connected between the power line and the earth, The filter section may be a noise reduction device that attenuates frequencies that are integer multiples of the resonance frequency of the noise filter and that are less than 150 kHz.

[0021] According to the eighth aspect, noise of frequency components that are out of the compensation band and that are less than 150 kHz among frequencies that are integer multiples of the resonance frequency of the noise filter are attenuated. Because noise at integer multiples of the resonance frequency of the noise filter is large, attenuating the noise of frequency components out of the compensation band allows for simplification and miniaturization of the generation unit that generates the compensation signal.

[0022] A ninth aspect is an air conditioner equipped with the noise reduction device according to any one of the first to eighth aspects.

[0023] According to the ninth aspect, an air conditioner includes the noise reduction device of any one of the first to eighth aspects, and therefore it is possible to provide an air conditioner that improves compensation performance for common mode noise. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a block diagram showing a first configuration example of a noise reduction device according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a configuration of a power conversion circuit. [Figure 3] 3 is a diagram for explaining the connection configuration between a detection circuit and a reduction circuit in the noise reduction device according to the first embodiment. FIG. [Figure 4] 3 is a circuit diagram showing a first detailed configuration example of a reduction circuit in the first configuration example of the noise reduction device according to the first embodiment. FIG. [Figure 5] FIG. 3 is a block diagram showing a second configuration example of the noise reduction device according to the first embodiment. [Figure 6] 4 is a circuit diagram showing a first detailed configuration example of a reduction circuit in the second configuration example of the noise reduction device according to the first embodiment. FIG. [Figure 7] 4 is a circuit diagram showing a second detailed configuration example of the reduction circuit in the second configuration example of the noise reduction device according to the first embodiment. FIG. [Figure 8] FIG. 4 is a block diagram showing a third configuration example of the noise reduction device according to the first embodiment. [Figure 9]FIG. 10 is a block diagram showing a first configuration example of a noise reduction device according to a second embodiment. [Figure 10] 10 is a diagram for explaining the connection configuration between a detection circuit and a reduction circuit in a noise reduction device according to a second embodiment. FIG. [Figure 11] FIG. 10 is a circuit diagram showing a first detailed configuration example of a reduction circuit in a first configuration example of a noise reduction device according to a second embodiment. [Figure 12] FIG. 10 is a block diagram showing a second configuration example of a noise reduction device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Several embodiments will be described below.

[0026] Fig. 1 is a block diagram showing a first configuration example of a noise reduction device according to a first embodiment. The noise reduction device 301 shown in Fig. 1 is provided in a power conversion system 1. The power conversion system 1 performs forward conversion or frequency conversion on AC input from a power source 10, and supplies the forward converted DC or frequency converted AC to a load 21.

[0027] The power supply 10 is an AC power supply that supplies AC power. When the power supply 10 is a three-phase AC power supply, the power supply 10 supplies three-phase AC power to the power conversion system 1. The power supply 10 is, for example, a commercial power supply.

[0028] When the load 21 is a DC load, the power conversion system 1 has a converter function for converting AC power supplied from the power source 10 into DC power to be supplied to the load 21. In this case, the load 21 operates on DC power supplied from the power conversion system 1. An example of a DC load is an electronic circuit. The electronic circuit includes, for example, a control circuit that controls the power conversion circuit 30.

[0029] When the load 21 is an AC load, the power conversion system 1 has an inverter function that converts the frequency of AC power supplied from the power source 10 into AC power to be supplied to the load 21. In this case, the load 21 operates on the AC power supplied from the power conversion system 1. An example of an AC load is a motor.

[0030] The power conversion system 1 is provided, for example, in a refrigeration device 200 equipped with a load 21. The refrigeration device 200 is a refrigeration cycle device equipped with a compressor driven by an AC motor, which is an example of the load 21. An example of the refrigeration device 200 is an air conditioner that conditions the air in a target space. Note that the device in which the power conversion system 1 is provided is not limited to the refrigeration device 200, and may be other equipment requiring a power conversion function.

[0031] The load 21 may be a three-phase AC motor. A three-phase AC motor is used as an electric motor that drives a compressor provided in a refrigerant circuit of the refrigeration device 200. The three-phase AC motor is, for example, a concentrated winding motor with 4 poles and 6 slots or 6 poles and 9 slots.

[0032] The power conversion system 1 includes a power conversion circuit 30 and a noise reduction device 301 .

[0033] The power conversion circuit 30 is electrically connected to an AC power line 11. The power conversion circuit 30 is mounted on, for example, a substrate (not shown). The substrate is a circuit board such as a printed circuit board. The power conversion circuit 30 is electrically connected to a power source 10 via the power line 11.

[0034] The power line 11 is a path for supplying single-phase or three-phase AC power generated by the power source 10. When supplying three-phase AC power, the power line 11 includes three-phase (R-phase, S-phase, and T-phase) power lines 11r, 11s, and 11t. The power line 11 is a power supply line that electrically connects the power source 10 and the power conversion circuit 30.

[0035] The power conversion circuit 30 is a circuit that performs forward conversion or frequency conversion of AC power input via the power line 11. The power conversion circuit 30 is an inverter circuit that performs frequency conversion of AC power input via the power line 11 to AC power to be supplied to the load 21, or a converter circuit that performs forward conversion to DC power to be supplied to the load 21.

[0036] Fig. 2 is a diagram showing an example of the configuration of a power conversion circuit. The power conversion circuit 30 shown in Fig. 2 includes a circuit for driving a motor M. The power conversion circuit 30 is an inverter circuit that converts the frequency of three-phase AC power input via the power line 11 into three-phase AC power to be supplied to the motor M, which is an example of the load 21. The power conversion circuit 30 includes a converter 102, a DC link 103, and an inverter 104 as circuits for driving the motor M.

[0037] Converter 102 is a circuit that converts AC input via power line 11 into DC, for example, converting three-phase AC into DC. Converter 102 is, for example, a diode bridge circuit in which a plurality of (for example, six) diodes are connected in a bridge configuration. These diodes full-wave rectify the AC voltage input from power line 11 and convert it into a DC voltage. Converter 102 may also be a voltage conversion circuit with a circuit format other than a diode bridge circuit. Converter 102 supplies the converted DC power to inverter 104 via DC link 103.

[0038] The DC link 103 is a portion to which DC output from the converter 102 is supplied. The DC link 103 includes, for example, a pair of DC buses 111 and 112 connecting the converter 102 and the inverter 104, and a capacitor 113 connected between the pair of DC buses 111 and 112. A voltage Vdc of the DC link 103 is a potential difference between the pair of DC buses 111 and 112, and is approximately equal to a DC voltage generated across the capacitor 113. The DC voltage Vdc is input to the inverter 104.

[0039] The inverter 104 is a circuit that converts the DC from the DC link 103 into AC, for example, converting the DC into three-phase AC. The inverter 104 supplies the converted AC power to the motor M. The inverter 104 is, for example, a bridge circuit in which a plurality of (for example, six) switching elements 104a are connected in a bridge shape. The inverter 104 converts the DC power from the DC link 103 into AC power for the motor M by turning on or off the plurality of switching elements 104a in accordance with a command S generated by a control unit (not shown).

[0040] 1, noise reduction device 301 has the function of an active noise canceller. Noise reduction device 301 detects common mode noise generated by power conversion circuit 30, and outputs a cancellation signal generated based on the level of the detected common mode noise to power line 11 or ground 12. Outputting the cancellation signal to power line 11 or ground 12 reduces the common mode noise flowing into power supply 10 electrically connected to power line 11 and ground 12. The cancellation signal is a signal that reduces common mode noise and is also called a compensation signal.

[0041] Common mode noise generated by the power conversion circuit 30 is transmitted through the earth 12 and the power line 11 via stray capacitance between the load 21 or the power conversion circuit 30 and the earth 12. The common mode noise generated by the power conversion circuit 30 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 30. The earth 12 is grounded (connected) to the ground to which the power supply 10 is grounded (connected).

[0042] The noise reduction device 301 according to the first embodiment detects a common mode noise current Ic (common mode current), and outputs a compensation current Io generated based on the level of the detected common mode current to the power line 11 or the earth 12. The noise reduction device 301 according to the first embodiment is a current detection / current output type active noise cancellation circuit.

[0043] The common mode noise current Ic (common mode current) is an example of common mode noise generated by the power conversion circuit 30. The compensation current Io is an example of a cancellation signal that is generated based on the level of the detected common mode noise.

[0044] The noise reduction device 301 according to the first embodiment includes a detection circuit 150 and a reduction circuit 180.

[0045] The detection circuit 150 is connected to the AC power line 11 and detects common mode noise generated in the power line 11 and earth 12 due to the switching operation of the power conversion circuit 30. The detection circuit 150 detects the common mode noise current Ic flowing in the power line 11 as common mode noise generated by the power conversion circuit 30. The detection circuit 150 detects the noise current Ic on the power source 10 side of the position of the power conversion circuit 30. The detection circuit 150 detects the noise current Ic flowing in the power line 11 between the power source 10 and the power conversion circuit 30, thereby detecting the common mode noise generated by the power conversion circuit 30. The detection circuit 150 detects the noise current Ic flowing in the power line 11 between the power source 10 and the power conversion circuit 30 using a transformer, for example.

[0046] The detection circuit 150 is configured to detect the noise current Ic using a transformer, and includes, for example, a magnetic body 51 around which a main winding 53 (53r, 53s, 53t) that is part of the power line 11 is wound, and an auxiliary winding 52 that is wound around the magnetic body 51.

[0047] The reduction circuit 180 is connected to the detection circuit 150 and reduces the common mode noise. The reduction circuit 180 functions as an active noise canceller. The reduction circuit 180 includes a generation unit 60 and an output unit 70.

[0048] The generating unit 60 generates a compensation signal that reduces common-mode noise based on the output voltage of the detecting circuit 150. The compensation current Io is an example of a compensation signal that reduces common-mode noise. The generating unit 60 generates the compensation current Io to be output to the power line 11 or the earth 12 based on the voltage output from the detecting circuit 150 in accordance with the level of the noise current Ic detected by the detecting circuit 150. The output unit 70 outputs the compensation current Io generated by the generating unit 60 to the power line 11 or the earth 12. The generating unit 60 reduces the noise current Ic, for example, by injecting the compensation current Io, which has substantially the same level as the noise current Ic and is in opposite phase to the noise current Ic, into the power line 11 or the earth 12 via the output unit 70. The output unit 70 injects the compensation current Io into the power line 11 or the earth 12 via a capacitor, for example.

[0049] 3 is a diagram illustrating the connection between the detection circuit and the reduction circuit in the noise reduction device according to the first embodiment. The detection circuit 150 has a magnetic body 51, a main winding 53, and an auxiliary winding 52. The magnetic body 51 is, for example, an annular magnetic core. The main winding 53 is a primary winding wound around the primary side of the magnetic body 51. The auxiliary winding 52 is a secondary winding wound around the secondary side of the magnetic body 51. If the turns ratio between the main winding 53 and the auxiliary winding 52 is N and the primary voltage input to the main winding 53 on the primary side of the detection circuit 150 is V1, the secondary voltage V2 output from the auxiliary winding 52 on the secondary side of the detection circuit 150 is ideally approximately equal to V1×N.

[0050] The reduction circuit 180 is connected to the auxiliary winding 52 of the detection circuit 150. However, depending on the configuration of the circuit connected to the detection circuit 150, the frequency characteristics of the voltage V2 output from the auxiliary winding 52 of the detection circuit 150 may deteriorate compared to the theoretical characteristics, resulting in a decrease in compensation performance for common-mode noise. For example, depending on the configuration of the circuit connected to the detection circuit 150, a decrease in the impedance on the secondary side of the detection circuit 150 may occur, resulting in a decrease in the voltage V2 in the frequency band from 100 kHz to 1 MHz. As the voltage V2 decreases, the input voltage Vd (FIG. 1) of the generator 60 in the reduction circuit 180 also decreases, which may result in a decrease in the accuracy of compensation performance for common-mode noise. To improve compensation performance for common-mode noise, it is desirable that the voltage V2 be a theoretically ideal value (=V1×N) determined by the turns ratio N between the main winding 53 and the auxiliary winding 52, even when the reduction circuit 180 is connected to the auxiliary winding 52 of the detection circuit 150.

[0051] In the noise reduction device 301 according to the first embodiment, there is a band between 150 kHz and 1 MHz in which the voltage V2 determined by the turns ratio N between the main winding 53 and the auxiliary winding 52 and the input voltage Vd (FIG. 1) of the generation unit 60 in the reduction circuit 180 substantially coincide.

[0052] "Approximately the same" means that if the input voltage Vd is k times the theoretical voltage V2, then k is between 0.9 and 1.1, preferably between 0.95 and 1.05, more preferably between 0.98 and 1.02, and most preferably 1. k is also called the ratio (gain) of Vd to V2 (k=Vd / V2).

[0053] According to the noise reduction device 301 of the first embodiment, in the frequency band of 150 kHz to 1 MHz, there exists a band in which the input voltage Vd of the generation unit 60 substantially matches the theoretical voltage V2 determined by the turns ratio N between the main winding 53 and the auxiliary winding 52. In this case, regardless of whether or not the reduction circuit 180 and the detection circuit 150 are connected and the manner of connection, the output voltage of the detection circuit 150 in this band remains almost unchanged (is maintained) from the ideal value determined by the design based on the turns ratio N. Since a decrease in the output voltage of the detection circuit 150 is suppressed, a decrease in the input voltage Vd of the generation unit 60 is also suppressed. Therefore, even if the reduction circuit 180 is connected to the detection circuit 150, the frequency characteristics of the output voltage of the detection circuit 150 are prevented from deteriorating compared to the theoretical characteristics in the frequency band of 150 kHz to 1 MHz, thereby improving compensation performance for common-mode noise.

[0054] 3, for example, in the frequency range of 150 kHz to 1 MHz, it is preferable for the input impedance Zin1 of the reduction circuit 180 to be higher than the impedance Z1 of the detection circuit 150 in terms of improving compensation performance for common-mode noise. The input impedance Zin1 is the impedance of the reduction circuit 180 when viewed from the detection circuit 150. The impedance Z1 of the detection circuit 150 is the impedance of the auxiliary winding 52 when it is wound around the magnetic body 51.

[0055] By providing a band in which the input impedance Zin1 of reduction circuit 180 is higher than the impedance Z1 of detection circuit 150 in the range of 150 kHz to 1 MHz, a decrease in the theoretically determined voltage V2 is suppressed in this band. This prevents the frequency characteristics of the output voltage of detection circuit 150 from deteriorating compared to the theoretical characteristics, and also suppresses a decrease in input voltage Vd of generation unit 60, improving compensation performance against common-mode noise.

[0056] 4 is a circuit diagram showing a first detailed configuration example of the reduction circuit 180 in the first configuration example of the noise reduction device 301 according to the first embodiment. The reduction circuit 180 is an active noise suppression means that suppresses common-mode noise. Based on the detection signal output from the auxiliary winding 52 of the detection circuit 150, the reduction circuit 180 outputs a compensation current Io to the power line 11 or the earth 12 to suppress the common-mode noise.

[0057] The reduction circuit 180 includes a generation unit 60, an output unit 70, a power supply circuit 85, a coupling capacitor 82, and a drive power supply 81. The generation unit 60 includes an amplifier circuit 69 and a compensation circuit 87.

[0058] The amplifier circuit 69 amplifies the input voltage Vd of the generator 60. The amplifier circuit 69 includes, for example, an operational amplifier 69a for amplifying the input voltage Vd.

[0059] The power supply voltage Vcc of the generator 60 (the voltage of the drive power supply 81) is, for example, ⅔ or less of the DC link voltage (DC link voltage Vdc) of the power conversion circuit 30. The voltage Vcom of the common-mode noise source (specifically, the potential at the neutral point of the motor M, which is generated when the motor M is driven by the inverter 104 of the power conversion circuit 30) changes in increments of ⅓. Therefore, as long as the power supply voltage Vcc is within a range of ±⅓ of the DC link voltage Vdc, the common-mode noise caused by the switching operation of the inverter 104 can be canceled out without considering the relationship between the power supply voltage Vcc and impedance.

[0060] The signal output from the amplifier circuit 69 is a signal representing the waveform of the compensation current or compensation voltage, and is input to the compensation circuit 87. 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 87. For example, the signal representing the waveform of the compensation current or compensation voltage output from the amplifier circuit 69 is a current or voltage waveform signal that has the same phase for each frequency as the waveform of the compensation current or compensation voltage output from the compensation circuit 87, but has a smaller amplitude.

[0061] The compensation circuit 87 amplifies the signal output from the amplifier circuit 69 and outputs a compensation current or a compensation voltage. The compensation circuit 87 includes transistors 61 and 62, diodes 63 and 64, resistors 65 and 66, and diodes 67 and 68.

[0062] The transistor 61 is connected between one end of the drive power supply 81 and the output capacitor 71 of the output section 70. The transistor 62 is connected between the other end of the drive power supply 81 and the output capacitor 71 of the output section 70.

[0063] 4, in this example, the transistor 61 is a PNP type, the transistor 62 is an NPN type, and the transistors 61 and 62 have opposite polarities to each other. As a result, the transistors 61 and 62 form a push-pull circuit, and the push-pull circuit functions as an amplifier.

[0064] The bases of the transistors 61 and 62 are connected to one end of the auxiliary winding 52 via diodes 67 and 68 and an amplifier circuit 69, and the interconnection point of the transistors 61 and 62 is connected to the other end of the auxiliary winding 52 via the amplifier circuit 69. This causes the transistors 61 and 62 to operate in opposite directions.

[0065] Diodes 63 and 64 are connected in antiparallel to transistors 61 and 62, respectively, to protect them.

[0066] The output unit 70 is connected between the compensation circuit 87 and the ground 12, and outputs (also referred to as "injecting") the compensation current or compensation voltage output from the compensation circuit 87 to a path through which the common-mode current flows. The output unit 70 includes an output capacitor 71. The output unit 70 may include a resistor or an inductor.

[0067] The output capacitor 71 has one end connected to the junction of the transistors 61 and 62 of the compensation circuit 87 and the other end connected to ground 12 .

[0068] The power supply circuit 85 is connected to the drive power supply 81. The power supply circuit 85 includes capacitors 83 and .

[0069] The capacitors 83 and 84 are connected in series. The series connection of the capacitors 83 and 84 is connected in parallel with the drive power supply 81 and the compensation circuit 87. The midpoint (neutral point 86) of the capacitors 83 and 84 is connected to the coupling capacitor 82.

[0070] Coupling capacitor 82 has one end connected to power line 11 and the other end connected to the midpoint between capacitors 83 and 84 (neutral point 86).

[0071] The driving power supply 81 supplies DC driving power to the generating unit 60 .

[0072] The driving power supply 81 may be a DC power supply that can independently supply DC to the generating unit 60, or may be, for example, a capacitor that uses the DC voltage of the DC link 103 of the power conversion circuit 30 as a power supply voltage.

[0073] Next, the operation of the generation unit 60 will be described with reference to FIG.

[0074] The detection circuit 150 detects common-mode noise on the power line 11 and drives the transistors 61 and 62 via the amplifier circuit 69. Specifically, an input voltage Vd corresponding to a detection signal output from the auxiliary winding 52 of the detection circuit 150 is amplified by the amplifier circuit 69 and input to the bases of the transistors 61 and 62.

[0075] When the common-mode noise current Ic flows in the direction of the arrow in Fig. 4, the transistor 61 is turned on. In this case, the compensation current Io is supplied from the drive power supply 81 and flows through a path that connects the positive terminal of the drive power supply 81 to the negative terminal of the drive power supply 81 via the capacitor 84, the coupling capacitor 82, the power supply 10, the output capacitor 71, and the transistor 61. In other words, the compensation current Io flows in the direction opposite to the direction of the arrow in Fig. 4. As a result, the compensation current Io is subtracted from the common-mode current Ic, and a reduced common-mode current Ig flows to the power supply 10.

[0076] 4, the transistor 62 is turned on. In this case, the compensation current Io is supplied from the drive power supply 81 and flows through a current path that connects the positive terminal of the drive power supply 81 to the negative terminal of the drive power supply 81, passing through the transistor 62, the output capacitor 71, the power supply 10, the coupling capacitor 82, and the capacitor 83. As a result, the compensation current Io is subtracted from the common mode current Ic, and a reduced common mode current Ig flows to the power supply 10 in the opposite direction to the arrow in FIG.

[0077] As described above, the compensation current Io flows through the compensation circuit 87. Therefore, the current supplied from the drive power supply 81 when the compensation current or compensation voltage is output is larger in the compensation circuit 87 than in the amplifier circuit 69.

[0078] In this way, the generating unit 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 power supply 10. Therefore, for example, the generating unit 60 can suppress a situation in which a common mode noise current flows out to a peripheral device through the power supply 10 and affects the peripheral device.

[0079] Figure 5 is a block diagram showing a second exemplary configuration of the noise reduction device 301 according to the first embodiment. In the second exemplary configuration shown in Figure 5, the same configuration, actions, and effects as those in the above exemplary configuration will not be described by citing the above descriptions. The reduction circuit 180 in the second exemplary configuration shown in Figure 5 differs from the reduction circuit 180 in the above exemplary configuration in that it includes one or more filter units (two filter units 91 and 92 are shown in Figure 5) that attenuate specific frequency components.

[0080] The filter unit 91 is connected between the detection circuit 150 and the generation unit 60. The filter unit 92 is connected between the generation unit 60 and the output unit 70. Fig. 5 shows a configuration in which both the filter unit 91 and the filter unit 92 are present. However, only one of the filter unit 91 and the filter unit 92 may be present.

[0081] The presence of one or both of the filter units 91 and 92 attenuates noise of specific frequency components. This allows part or all of the frequency band of the frequency components to be excluded from the compensation band of the compensation signal (compensation current or compensation voltage), thereby simplifying or miniaturizing the generation unit 60 that generates the compensation signal. Reducing noise outside the compensation band (e.g., low-frequency components below 150 kHz that do not require compensation) requires an increased compensation signal, which requires the use of active elements with high withstand voltages or large current capacities in the generation unit 60. However, active elements with high withstand voltages or large current capacities generate a lot of heat due to losses when a large current flows through them, or their operating frequencies are low, limiting the band that can be compensated. Attenuating low-frequency noise components below 150 kHz that do not require compensation using one or both of the filter units 91 and 92 allows the generation unit 60 to use active elements with low withstand voltages or high operating speeds, thereby simplifying or miniaturizing the generation unit 60. Examples of the filter unit 91 or the filter unit 92 include band-pass filters and high-pass filters.

[0082] Filter unit 92 is connected between generating unit 60 and output unit 70. As a result, filter unit 92 is connected to detection circuit 150 via generating unit 60, and therefore the effect that the connection of filter unit 92 has on the frequency characteristics of the output voltage of detection circuit 150 is reduced compared to a configuration in which filter unit 92 is directly connected to detection circuit 150. Therefore, even if filter unit 92 is included in reduction circuit 180, the frequency characteristics of the output voltage of detection circuit 150 are prevented from deteriorating compared to the theoretical characteristics in the band of 150 kHz or more and 1 MHz or less, and compensation performance against common-mode noise is improved.

[0083] It is difficult to control the leakage magnetic flux of the detection circuit 150, and there is a possibility that noise may be amplified due to resonance of the filter unit 91. The presence of the filter unit 92, but not the filter unit 91, reduces the occurrence of such inconvenience.

[0084] The filter unit 91 is a circuit that passes a signal obtained by removing specific frequency components from the detection signal output from the auxiliary winding 52. The output signal from the filter unit 91 is input to the generation unit 60. The filter unit 92 is a circuit that passes a signal obtained by removing specific frequency components from the compensation signal (compensation current or compensation voltage) output from the generation unit 60. The output signal from the filter unit 92 is input to the output unit 70.

[0085] The filter unit 91 or the filter unit 92 attenuates, for example, frequencies less than 150 kHz among frequencies that are integer multiples of the switching frequency (e.g., 10 kHz) of the power conversion circuit 30. This attenuates noise of frequency components less than 150 kHz that are outside the compensation band among frequencies that are integer multiples of the switching frequency of the power conversion circuit 30. Because the noise of integer multiples of the switching frequency of the power conversion circuit 30 is large, attenuating the noise of frequency components outside the compensation band allows the generation unit 60 that generates the compensation signal to be simplified or made smaller. Since low-frequency noise components less than 150 kHz that do not need to be compensated are attenuated by one or both of the filter units 91 and 92, it is possible to use active elements with low withstand voltage or high-speed operation in the generation unit 60, allowing the generation unit 60 to be simplified or made smaller.

[0086] Fig. 6 is a circuit diagram showing a first detailed configuration example of the reduction circuit 180 in the second configuration example of the noise reduction device 301 according to the first embodiment shown in Fig. 5. The reduction circuit 180 shown in Fig. 6 includes a filter unit 91 and a filter unit 92. The filter unit 91 is connected between the auxiliary winding 52 of the detection circuit 150 and the amplifier circuit 69 of the generation unit 60. The filter unit 92 is connected between the compensation signal output point of the generation unit 60 (the interconnection point of the transistors 61 and 62) and the output capacitor 71 of the output unit 70.

[0087] Fig. 7 is a circuit diagram showing a second detailed configuration example of the reduction circuit 180 in the second configuration example of the noise reduction device 301 according to the first embodiment shown in Fig. 5. The reduction circuit 180 shown in Fig. 7 does not include the filter unit 91, but includes a filter unit 92. Note that the reduction circuit 180 may include the filter unit 91 (Fig. 6) without including the filter unit 92.

[0088] Fig. 8 is a block diagram showing a third configuration example of a noise reduction device 301 according to the first embodiment. In the third configuration example shown in Fig. 8, the same configurations, actions, and effects as those of the above-mentioned configuration examples will not be described by citing the above descriptions. The noise reduction device 301 in the third configuration example shown in Fig. 8 differs from the noise reduction device 301 in the above-mentioned configuration examples in that it includes a noise filter 40.

[0089] The noise filter 40 is a passive noise suppression means for suppressing common mode noise and includes a common mode choke coil 41 and a capacitor 42.

[0090] Common mode choke coil 41 is connected to power line 11 and acts as an inductor to suppress common mode noise current (common mode current) flowing through power line 11.

[0091] Capacitor 42 is a Y capacitor connected between power line 11 and earth 12, and serves to return the common mode current that has flowed out to earth 12 to power conversion circuit 30, which serves as a noise source. Capacitor 42 has one end connected to power line 11 and the other end connected to earth 12.

[0092] The filter unit 92 attenuates, for example, frequencies less than 150 kHz among integer multiples of the resonant frequency of the noise filter 40. This attenuates noise components of frequencies less than 150 kHz that are outside the compensation band among integer multiples of the resonant frequency of the noise filter 40. Because the noise of integer multiples of the resonant frequency of the noise filter 40 is large, attenuating the noise components of frequencies outside the compensation band allows the generation unit 60, which generates the compensation signal, to be simplified and miniaturized. Attenuating low-frequency noise components less than 150 kHz that do not require compensation by one or both of the filter units 91 and 92 allows the generation unit 60 to use active elements with low voltage resistance or high speed operation, thereby simplifying and miniaturizing the generation unit 60. The resonant frequency of the noise filter 40 is determined by the inductance of the common mode choke coil 41 and the capacitance of the capacitor 42.

[0093] The above-described filter unit 91 may be present instead of or in addition to the filter unit 92. Similar to the filter unit 92, the filter unit 91 may attenuate frequencies that are integer multiples of the resonance frequency of the noise filter 40 and that are less than 150 kHz.

[0094] 9 is a block diagram showing a first configuration example of a noise reduction device according to the second embodiment. In the second embodiment, the same configuration, actions, and effects as those of the first embodiment will not be described by citing the above description. The power conversion system 1 includes a power conversion circuit 30 and a noise reduction device 302.

[0095] 9, noise reduction device 302 has the function of an active noise canceller. Noise reduction device 302 detects common mode noise generated by power conversion circuit 30, and outputs a cancellation signal generated based on the level of the detected common mode noise to power line 11. Outputting the cancellation signal to power line 11 reduces common mode noise flowing into power supply 10, which is electrically connected to power line 11 and earth 12. The cancellation signal is a signal that reduces common mode noise and is also called a compensation signal.

[0096] The noise reduction device 302 according to the second embodiment detects a common-mode noise voltage Vc (common-mode voltage), and outputs a compensation voltage Vo generated based on the level of the detected common-mode voltage to the power line 11. The noise reduction device 302 according to the second embodiment is a voltage detection / voltage output type active noise cancellation circuit.

[0097] The common mode noise voltage Vc (common mode voltage) is an example of common mode noise generated by the power conversion circuit 30. The compensation voltage Vo is an example of a cancellation signal that is generated based on the level of the detected common mode noise.

[0098] The noise reduction device 301 according to the second embodiment includes a detection circuit 250 and a reduction circuit 280 .

[0099] The detection circuit 250 is connected to the AC power line 11 and detects common mode noise generated on the power line 11 and earth 12 due to the switching operation of the power conversion circuit 30. The detection circuit 250 detects the common mode noise voltage Vc generated on the power line 11 as common mode noise generated by the power conversion circuit 30. The detection circuit 250 detects the noise voltage Vc on the power source 10 side of the position of the power conversion circuit 30. The detection circuit 250 detects the noise voltage Vc generated on the power line 11 between the power source 10 and the power conversion circuit 30, thereby detecting the common mode noise generated by the power conversion circuit 30. The detection circuit 250 detects the noise voltage Vc, for example, using impedance elements such as a capacitor and a resistor.

[0100] The detection circuit 250 is configured to detect the noise voltage Vc using an impedance element, and includes, for example, a plurality of impedance elements 55, 56 connected in series between the power line 11 and the earth 12. The impedance elements 55, 56 are, for example, capacitors. The detection circuit 250 outputs a voltage Vc corresponding to the level of common-mode noise generated by the power conversion circuit 30 from the impedance element 56 by voltage division using the impedance elements 55, 56. The detection circuit 250 detects the magnitude of the common-mode noise voltage Vc (common-mode voltage) generated in the impedance element 56 as a voltage Vc corresponding to the level of the common-mode noise. The reduction circuit 280 then generates a compensation voltage Vo, which is a cancellation signal that reduces the common-mode noise, based on the voltage Vc corresponding to the level of the common-mode noise.

[0101] The reduction circuit 280 is connected to the detection circuit 250 and reduces common mode noise. The reduction circuit 280 functions as an active noise canceller. The reduction circuit 280 includes a generation unit 60 and an output unit 70.

[0102] The generating unit 60 generates a compensation signal that reduces common-mode noise based on the output voltage of the detecting circuit 250. The compensation voltage Vo is an example of a compensation signal that reduces common-mode noise. The generating unit 60 generates the compensation voltage Vo to be output to the power line 11 based on the voltage output from the detecting circuit 250 in accordance with the level of the noise voltage Vc detected by the detecting circuit 250. The output unit 70 outputs the compensation voltage Vo generated by the generating unit 60 to the power line 11. For example, the generating unit 60 reduces the noise voltage Vc by superimposing the compensation voltage Vo, which has substantially the same level as the noise voltage Vc, on the power line 11 in opposite phase to the noise voltage Vc, via the output unit 70. The output unit 70 outputs the compensation voltage Vo to the power line 11 via, for example, a transformer.

[0103] 10 is a diagram illustrating the connection between the detection circuit and the reduction circuit in the noise reduction device according to the second embodiment. The detection circuit 250 includes a first impedance element 55 having one end connected to the power line 11 and a second impedance element 56 having one end connected to the other end of the first impedance element 55 and the other end connected to ground 12. The impedance elements 55 and 56 are, for example, capacitors. If the voltage division ratio between the impedance elements 55 and 56 is m and the voltage generated in the impedance element 55 of the detection circuit 250 is V1, then the voltage V2 output from the impedance element 56 of the detection circuit 250 is ideally approximately equal to V1 × m.

[0104] The reduction circuit 280 is connected to the impedance element 56 of the detection circuit 250. However, depending on the configuration of the circuit connected to the detection circuit 250, the frequency characteristics of the voltage V2 output from the impedance element 56 of the detection circuit 250 may deteriorate compared to the theoretical characteristics, resulting in a decrease in the compensation performance for common-mode noise. For example, depending on the configuration of the circuit connected to the detection circuit 250, a decrease in the impedance on the output side of the detection circuit 250 may occur, resulting in a decrease in the voltage V2 in the frequency band from 100 kHz to 1 MHz. As the voltage V2 decreases, the input voltage Vd (FIG. 9) of the generation unit 60 in the reduction circuit 280 also decreases, which may result in a decrease in the accuracy of the compensation performance for common-mode noise. To improve the compensation performance for common-mode noise, it is desirable that the voltage V2 be a theoretically ideal value (=V1×m) determined by the voltage division ratio m, even when the reduction circuit 280 is connected to the impedance element 56 of the detection circuit 250.

[0105] In the noise reduction device 302 according to the second embodiment, there is a band between 150 kHz and 1 MHz in which the voltage V2 determined by the voltage division ratio m between the first impedance element 55 and the second impedance element 56 and the input voltage Vd (FIG. 9) of the generation unit 60 in the reduction circuit 280 substantially coincide.

[0106] "Approximately the same" means that if the input voltage Vd is k times the theoretical voltage V2, then k is between 0.9 and 1.1, preferably between 0.95 and 1.05, more preferably between 0.98 and 1.02, and most preferably 1. k is also called the ratio (gain) of Vd to V2 (k=Vd / V2).

[0107] According to the noise reduction device 302 of the second embodiment, in the frequency band of 150 kHz to 1 MHz, there exists a band where the input voltage Vd of the generation unit 60 substantially coincides with the theoretical voltage V2 determined by the voltage division ratio m. In this case, regardless of whether or not the reduction circuit 280 and the detection circuit 250 are connected and how they are connected, the output voltage of the detection circuit 250 remains almost unchanged (maintains) from the ideal value determined by the design based on the voltage division ratio m in that band. Since a decrease in the output voltage of the detection circuit 250 is suppressed, a decrease in the input voltage Vd of the generation unit 60 is also suppressed. Therefore, even if the reduction circuit 280 is connected to the detection circuit 250, the frequency characteristics of the output voltage of the detection circuit 250 are prevented from deteriorating from the theoretical characteristics in the frequency band of 150 kHz to 1 MHz, thereby improving compensation performance for common-mode noise.

[0108] 10, for example, in the frequency range of 150 kHz to 1 MHz, it is preferable that the input impedance Zin2 of the reduction circuit 280 be higher than the impedance Z2 of the detection circuit 250 in order to improve the compensation performance for common-mode noise. The input impedance Zin2 is the impedance of the reduction circuit 280 when viewed from the detection circuit 250. The impedance Z2 of the detection circuit 250 is the impedance of the second impedance element 56.

[0109] By providing a band in which the input impedance Zin2 of reduction circuit 280 is higher than the impedance Z2 of detection circuit 250 in the range of 150 kHz to 1 MHz, a decrease in the theoretically determined voltage V2 is suppressed in this band. This prevents the frequency characteristics of the output voltage of detection circuit 250 from deteriorating compared to the theoretical characteristics, and also suppresses a decrease in input voltage Vd of generation unit 60, improving compensation performance against common-mode noise.

[0110] 11 is a circuit diagram showing a first detailed configuration example of the reduction circuit 280 in the first configuration example of the noise reduction device 302 according to the second embodiment. In the first configuration example shown in FIG. 11, the same configurations, actions, and effects as those in the above-described configuration examples will not be described again by citing the above descriptions. The reduction circuit 280 is an active noise suppression means that suppresses common-mode noise. Based on the detection signal output from the impedance element 56 of the detection circuit 250, the reduction circuit 280 outputs a compensation voltage Vo to the power line 11 to suppress common-mode noise.

[0111] The output unit 70 connects the compensation circuit 87 and the power line 11, and outputs the compensation current or compensation voltage output from the compensation circuit 87 to a path through which the common mode current flows. The output unit 70 includes an output transformer 72.

[0112] The output transformer 72 has a primary winding and a secondary winding. One end of the primary winding is connected to the interconnection point of the transistors 61 and 62 of the compensation circuit 87, and the other end is connected to the neutral point 86 of the power supply circuit 85. The secondary windings are inserted into the power lines 11r, 11s, and 11t of each phase included in the power line 11.

[0113] Fig. 12 is a block diagram showing a second exemplary configuration of a noise reduction device 302 according to the second embodiment. In the second exemplary configuration shown in Fig. 12, the same configuration, actions, and effects as those in the above exemplary configuration will not be described by citing the above descriptions. The reduction circuit 280 in the second exemplary configuration shown in Fig. 12 differs from the reduction circuit 280 in the above exemplary configuration in that it includes one or more filter units (Fig. 12 illustrates two filter units 91 and 92) that attenuate specific frequency components.

[0114] The filter unit 91 is connected between the detection circuit 250 and the generation unit 60. The filter unit 92 is connected between the generation unit 60 and the output unit 70. Fig. 12 shows a configuration in which both the filter unit 91 and the filter unit 92 are present. However, only one of the filter unit 91 and the filter unit 92 may be present.

[0115] The configuration, operation, and effects of the filter sections 91, 92 in the second embodiment are similar to those of the filter sections 91, 92 in the above-described embodiment, and therefore detailed description thereof will be omitted.

[0116] 11, the filter unit 91 may be connected between the impedance element 56 of the detection circuit 250 and the amplifier circuit 69 of the generation unit 60. The filter unit 92 may be connected between the compensation signal output point (the interconnection point of the transistors 61 and 62) of the generation unit 60 and the output transformer 72 of the output unit 70.

[0117] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

[0118] For example, the noise reduction device is not limited to a current detection / current output type or voltage detection / voltage output type active noise cancellation circuit, but may also be a current detection / voltage output type or voltage detection / current output type active noise cancellation circuit. For example, in FIG. 1, the current detection type detection circuit 150 may be replaced with a voltage detection side detection circuit 250 (see FIG. 9), and the current output type output section 70 may be replaced with a voltage output type output section 70 (see FIG. 9). Similarly, in FIG. 9, the voltage detection type detection circuit 250 may be replaced with the current detection side detection circuit 150 (see FIG. 1), and the voltage output type output section 70 may be replaced with a current output type output section 70 (see FIG. 1). [Explanation of symbols]

[0119] 1 Power Conversion System 10 Power supply 11 Power Lines 12 Earth 21 Load 30 Power Conversion Circuit 40 Noise Filter 41 Common mode choke coil 42 Capacitor 51 Magnetic material 52 Auxiliary Winding 53,53r,53s,53t Main winding 55 First impedance element 56 Second impedance element 60 Generation part 69 Amplifier Circuit 70 Output section 71 Output capacitor 72 Output transformer 81 Drive power supply 82 Coupling capacitor 83,84 Capacitor 85 Power supply circuit 86 Neutral point 87 Compensation circuit 91,92 Filter section 150,250 detection circuit 180,280 reduction circuit 200 Refrigeration equipment 301,302 Noise reduction device

Claims

1. a detection circuit (150) connected to an AC power line (11) and detecting common mode noise generated in the power line and earth (12) due to switching operations of a power conversion circuit (30); a reduction circuit (180) connected to the detection circuit and configured to reduce the common mode noise; The reduction circuit a generating unit (60) that generates a compensation signal that reduces the common-mode noise based on the output voltage of the detection circuit; an output section (70) that outputs the compensation signal to the power line or the earth; The detection circuit a magnetic body (51) around which main windings (53r, 53s, 53t) that are part of the power lines are wound; an auxiliary winding (52) wound around the magnetic body; A noise reduction device in which a voltage (V2) determined by a turns ratio between the main winding and the auxiliary winding and an input voltage (Vd) of the generating unit substantially coincide with each other in a band of 150 kHz to 1 MHz.

2. a detection circuit (250) connected to an AC power line (11) and detecting common mode noise generated in the power line and earth (12) due to switching operations of a power conversion circuit (30); a reduction circuit (280) connected to the detection circuit and configured to reduce the common mode noise; The reduction circuit a generating unit (60) that generates a compensation signal that reduces the common-mode noise based on the output voltage of the detection circuit; an output section (70) that outputs the compensation signal to the power line or the earth; The detection circuit includes an impedance element (55, 56) connected between the power line and the ground; The impedance elements include a first impedance element (55) having one end connected to the power line, and a second impedance element (56) having one end connected to the other end of the first impedance element and the other end connected to the ground, A noise reduction device in which the voltage (V2) of the second impedance element, determined by the voltage division ratio between the first impedance element and the second impedance element, and the input voltage (Vd) of the generation unit are approximately the same in a band of 150 kHz to 1 MHz.

3. The input impedance (Zin1) of the reduction circuit (180) has a band in which the input impedance (Zin1) of the detection circuit (150) is higher than the impedance (Z1) of the detection circuit (150) in the range of 150 kHz to 1 MHz, 2. The noise reduction device according to claim 1, wherein the impedance (Z1) of the detection circuit (150) is the impedance of the auxiliary winding in a state where it is wound around the magnetic body.

4. The input impedance (Zin2) of the reduction circuit (280) has a band in which the input impedance (Zin2) of the detection circuit (250) is higher than the impedance (Z2) of the detection circuit (250) in the range of 150 kHz to 1 MHz, 3. The noise reduction device of claim 2, wherein the impedance (Z2) of the detection circuit (250) is the impedance of the second impedance element.

5. The reduction circuit includes a filter unit (91, 92) that attenuates a specific frequency component, The noise reduction device according to claim 3 , wherein the filter section is connected between the generation section and the output section, between the detection circuit and the generation section, or between both of them.

6. The noise reduction device according to claim 5 , wherein the filter unit is connected between the generation unit and the output unit.

7. The noise reduction device according to claim 5 , wherein the filter section attenuates frequencies that are integer multiples of the switching frequency of the power conversion circuit and that are less than 150 kHz.

8. The noise reduction device includes a noise filter (40) having a common mode choke coil (41) connected to the power line and a capacitor (42) connected between the power line and the earth, 6. The noise reduction device according to claim 5, wherein the filter section attenuates frequencies that are integer multiples of the resonance frequency of the noise filter and that are less than 150 kHz.

9. An air conditioner comprising the noise reduction device according to any one of claims 1 to 4.

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