Active filter device and electric compressor equipped with same

Abstract

To provide an active filter device capable of improving attenuation characteristics of a passive-type common mode noise filter in a high frequency region without using a common mode transformer or significantly increasing a volume and a weight of the common mode noise filter.SOLUTION: An active filter device 1 comprises: a common mode choke coil 28 inserted into a pair of power supply lines 11 and 12; a detection unit 29 that detects a common mode voltage; inverting amplifier circuits 37 and 57 that invert and amplify the common mode voltage detected by the detection unit 29, and two pairs of Y capacitors 21, 22, 41, and 42 having different capacitance values and connected between respective outputs of the inverting amplifiers and the respective pair of power source lines 11 and 12. Output voltages of the inverting amplifiers 37 and 57 are applied to the respective Y capacitors 21, 22, 41, and 42 as compensation voltages.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an active filter device for suppressing common-mode noise, and to an electric compressor equipped with the active filter device. [Background technology]

[0002] Passive common mode noise filters (passive filters) designed to reduce common mode noise consist of Y capacitors connected between a pair of power supply lines and a ground potential, and a common mode choke coil inserted into the pair of power supply lines (see, for example, Patent Document 1).

[0003] However, in the case of an inverter device that drives the motor of an electric compressor, for example, if a Y capacitor, which is a component, is used to improve the attenuation characteristics of a passive common mode noise filter, there are restrictions on the capacitance value from a safety standpoint due to an increase in leakage current, and it becomes necessary to use an unrealistic capacitance value. Also, even if a common mode choke coil is used, there are issues with the dimensions of the coil that can be implemented.

[0004] Therefore, various common mode noise filters that employ an active system have been developed (see, for example, Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-78844 [Patent Document 2] Patent No. 3044650 [Patent Document 3] Patent No. 2863833 [Patent Document 4] Patent No. 5528543 Summary of the Invention [Problem to be solved by the invention]

[0006] However, all of the above documents require a common-mode transformer to detect and compensate for common-mode noise, which increases the size of the active filter device, leaving room for improvement. Furthermore, while it is possible to reduce common-mode noise impedance by increasing the capacitance of the Y capacitor, there is also the issue that an increase in the capacitance of the Y capacitor reduces the resonant frequency with the parasitic inductance, thereby reducing noise reduction performance in the high-frequency range.

[0007] The present invention has been made to solve the above-mentioned conventional technical problems, and has an object to provide an active filter device that can improve the attenuation characteristics of a common mode noise filter in the high frequency range without using a common mode transformer and without significantly increasing the volume or weight compared to passive common mode noise filters, and an electric compressor equipped with the same. [Means for solving the problem]

[0008] The active filter device of the present invention comprises a plurality of sets of Y capacitors, each having one end connected to a pair of power supply lines, a common mode choke coil inserted into the pair of power supply lines, a detection unit that detects common mode voltages, and a plurality of inverting amplifier circuits provided corresponding to each set of Y capacitors that invert and amplify the common mode voltage detected by the detection unit, wherein the capacitance value of the Y capacitors is set to a different value for each set, the output of each inverting amplifier circuit is connected to the other end of each set of Y capacitors, and the output voltage of each inverting amplifier circuit is applied as a compensation voltage to each set of Y capacitors.

[0009] The active filter device of the present invention according to claim 2 is characterized in that in the above invention, a common-mode voltage detected by a single detection unit composed of a pair of common-mode voltage detection capacitors is input to each inverting amplifier circuit.

[0010] The active filter device according to the invention of claim 3 is characterized in that a detection section is provided for each inverting amplifier circuit.

[0011] The active filter device of the invention according to claim 4 is characterized in that the ground path of the detection section and the ground path of the inverting amplifier circuit are connected to the circuit ground separately.

[0012] The electric compressor of the invention of claim 5 is characterized in that the active filter device of each of the above inventions and an inverter device are provided integrally with a housing.

[0013] The electric compressor of the invention of claim 6 is characterized in that in the above invention, the housing is at ground potential, the circuit ground is connected to the housing, the ground path of the detection unit is connected to the housing, and the ground path of the inverting amplifier circuit is connected to the circuit ground. [Effects of the Invention]

[0014] The active filter device of the present invention comprises multiple sets of Y capacitors, one end of which is connected to a pair of power supply lines, a common mode choke coil inserted into the pair of power supply lines, a detection unit that detects the common mode voltage, and multiple inverting amplifier circuits that are provided corresponding to each set of Y capacitors and invert and amplify the common mode voltage detected by the detection unit. The capacitance value of the Y capacitors is set to a different value for each set, and the output of each inverting amplifier circuit is connected to the other end of each set of Y capacitor, respectively. The output voltage of each inverting amplifier circuit is applied to each set of Y capacitor as a compensation voltage, so that the apparent capacitance value of each set of Y capacitor increases in accordance with the gain of each inverting amplifier circuit.

[0015] This increase in the apparent capacitance of the Y capacitor makes it possible to increase the return flow of noise current and reduce the common mode current leaking to the power supply without using a large-capacity Y capacitor or a large common mode choke coil.In addition, it can be applied to a normal passive noise filter consisting of a common mode choke coil and Y capacitor to improve the attenuation characteristics of common mode noise, making it highly versatile.

[0016] In particular, this invention provides multiple sets of Y capacitors and multiple corresponding inverting amplifier circuits, with the capacitance value of the Y capacitors set to a different value for each set, and connects the output of each inverting amplifier circuit to the other end of each set of Y capacitors, respectively, and applies the output voltage of each inverting amplifier circuit as a compensation voltage to each set of Y capacitors, thereby suppressing the increase in common-mode noise impedance in the high-frequency range caused by the resonant frequency of the Y capacitors and more effectively improving the attenuation characteristics of common-mode noise.In addition, by individually selecting the gain value of each inverting amplifier circuit according to the purpose of use, the frequency characteristics of the common-mode impedance can be adjusted to match the EMI noise characteristics.

[0017] In this case, as in the invention of claim 2, the common-mode voltage detected by a single detection unit composed of a pair of common-mode voltage detection capacitors can be input to each inverting amplifier circuit, thereby simplifying the circuit configuration of the detection unit.

[0018] On the other hand, if a detector is provided for each inverting amplifier circuit as in the invention of claim 3, there is an advantage that common mode noise voltage detection characteristics according to the frequency characteristics of each inverting amplifier circuit can be obtained.

[0019] Furthermore, as in the invention of claim 4, by connecting the ground path of the detection unit and the ground path of the inverting amplifier circuit to the circuit ground separately, it is possible to reduce the adverse effect that voltage fluctuations with respect to the circuit ground caused by the operating current of the inverting amplifier circuit have on the detection of the common-mode voltage by the detection unit.

[0020] The active filter device of each of the above inventions is extremely suitable when it is integrally provided in the housing of the electric compressor together with the inverter device, as in the fifth invention.

[0021] Furthermore, as in the invention of claim 6, by setting the housing to ground potential, connecting the circuit ground to the housing, connecting the ground path of the detection unit to the housing, and connecting the ground path of the inverting amplifier circuit to the circuit ground, it is possible to reduce detection errors in the detection unit due to fluctuations in the potential of the circuit ground caused by the operating current of the inverting amplifier circuit. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an electrical circuit diagram of an electric compressor according to an embodiment of the present invention, to which an active filter device is applied, and a power supply path to the electric compressor. [Figure 2] FIG. 2 is an electric circuit diagram of the electric compressor of FIG. 1 (first embodiment). [Figure 3] FIG. 3 is an equivalent circuit diagram of the active filter device of FIG. 2. [Figure 4] FIG. 10 is a diagram showing the impedance characteristics of a Y capacitor for explaining the common-mode noise reduction effect of the active filter device of the present invention. [Figure 5] 1 and an electric circuit of a power supply path to the electric compressor according to another embodiment (Embodiment 2). [Figure 6] FIG. 3 is a diagram showing another embodiment of the electric circuit of the electric compressor of FIG. 2 (Embodiment 3). DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0024] FIG. 1 shows an electric circuit diagram of an electric compressor 2 according to an embodiment of the present invention, to which an active filter device 1 is applied, and a power supply path to the electric compressor 2, and FIG. 2 shows an electric circuit diagram of the electric compressor 2.

[0025] The electric compressor 2 of the embodiment is mounted on a vehicle such as an electric vehicle or a hybrid vehicle and forms part of a refrigerant circuit of a vehicle air conditioner that conditions the interior of the vehicle, and the inverter device (PWM inverter) 3 and the active filter device 1 of the present invention are provided integrally in a housing 18 (described later) of the electric compressor 2. In other words, the electric compressor 2 of the embodiment is an inverter-integrated electric compressor.

[0026] The inverter device 3 converts DC voltage from a high voltage battery 7 (HV, for example, DC 350 V) mounted on the vehicle as a DC power source into AC voltage of a given frequency and supplies it to the motor 8 of the electric compressor 2 to operate it. The active filter device 1 of the embodiment of the present invention is provided to reduce common mode noise generated in the inverter device 3.

[0027] (1) Power supply path for electric compressor 2 In Fig. 1, the inverter device 3 is composed of a plurality of switching elements (IGBTs) 15 connected to a positive power supply line 11 and a negative power supply line 12 of a high-voltage battery 7. Reference numeral 20 in Fig. 1 denotes a control circuit, and each switching element 15 of the inverter device 3 is subjected to switching control (PWM control) by this control circuit 20. Reference numeral 13 denotes a smoothing capacitor connected between the pair of power supply lines 11 and 12.

[0028] Reference numeral 14 denotes the vehicle's ECU, 16 a low-voltage battery (DC 12V), and a control circuit 20 controls the switching of each switching element 15 of the inverter device 3 using the low-voltage battery 16 as a power source based on commands from the ECU 14. Reference numeral 18 denotes a housing (made of aluminum die-cast) of the electric compressor 2. Furthermore, the electric compressor 2 is connected to the high-voltage battery 7 by a shielded HV harness 25 (which constitutes a pair of power supply lines 11, 12), and the housing 18 of the electric compressor 2 is directly fixed to the body of the vehicle. This sets the housing 18 at ground potential.

[0029] The active filter device 1 of the embodiment includes a first set of Y capacitors (C Y1 ) 21, 22 (first Y capacitors), and a second set of Y capacitors (C Y2 ) 41, 42 (second Y capacitors), an active filter compensation circuit 23 connected between these two sets of Y capacitors 21, 22, 41, 42 and the housing 18 (ground potential), and a pair of common mode voltage detection capacitors 26, 27 (C sense : constituting the detection unit 29 in the present invention), and a common mode choke coil (CMCC) 28 inserted in a pair of power supply lines 11, 12 on the high-voltage battery 7 side as viewed from these Y capacitors 21, 22, 41, 42, active filter compensation circuit 23, and common mode voltage detection capacitors 26, 27.

[0030] (2) Electric circuit of electric compressor 2 Next, Figure 2 shows only the electrical circuit of the electric compressor 2. In this figure, the same reference numerals as in Figure 1 denote the same things. Insulating paper, refrigerant, and oil are present between the winding 8C of the motor 8 and the housing 18, and the stray capacitance between the winding 8C of the motor 8 and the housing 18 is shown as 31 in Figure 2. A noise current flows through this stray capacitance 31, generating common mode noise.

[0031] 2 also shows details of the active filter compensation circuit 23 of the active filter device 1. The active filter compensation circuit 23 of the embodiment includes amplifiers 32 and 52 and negative feedback resistors (R f _ com1 ) 33, negative feedback resistor (R f _ com2 ) 53, and a power supply circuit (V CC , V EE ) 34, the common mode voltage detection capacitors 26 and 27, and the common mode voltage detection resistor (R sense1 ) 36 and common-mode voltage detection resistor (R sense2 )56.

[0032] The amplifier 32, negative feedback resistor 33, and common-mode voltage detection resistor 36 constitute a first inverting amplifier circuit 37 (first inverting amplifier circuit: gain G1) of the present invention. The amplifier 52, negative feedback resistor 53, and common-mode voltage detection resistor 56 constitute a second inverting amplifier circuit 57 (second inverting amplifier circuit: gain G2) of the present invention. One ends of the common-mode voltage detection capacitors 26 and 27 are connected to the pair of power supply lines 11 and 12, respectively, and the other common ends of the common-mode voltage detection capacitors 26 and 27 are connected to one ends of the common-mode voltage detection resistors 36 and 56, respectively.

[0033] The other end of common mode voltage detection resistor 36 is connected to the inverting input terminal (-) of amplifier 32, and the other end of common mode voltage detection resistor 56 is connected to the inverting input terminal (-) of amplifier 52. The non-inverting input terminals (+) of amplifiers 32 and 52 are connected to circuit ground 30 in this embodiment via ground paths 38 and 58, respectively. These ground paths 38 and 58 serve as the ground paths of detection unit 29. The circuit ground 30 is connected to the housing 18, which is at ground potential.

[0034] Meanwhile, one ends of the aforementioned Y capacitors 21 and 22 are connected to a pair of power supply lines 11 and 12, respectively, and one ends of the Y capacitors 41 and 42 are also connected to a pair of power supply lines 11 and 12. The other ends of the Y capacitors 21 and 22 are both connected to the output terminal of the amplifier 32 (the first output of the active filter compensation circuit 23), and the other ends of the Y capacitors 41 and 42 are both connected to the output terminal of the amplifier 52 (the second output of the active filter compensation circuit 23).

[0035] In this embodiment, the ground path 39 of the power supply circuit 34 of the amplifiers 32 and 52 is connected to the circuit ground 30 separately from the ground paths 38 and 58. This ground path 39 is the ground path of the inverting amplifier circuits 37 and 57.

[0036] As a result, Y capacitors 21 and 22 are connected between the pair of power supply lines 11 and 12 and the housing 18 (ground potential) via amplifier 32 of active filter compensation circuit 23, and Y capacitors 41 and 42 are connected between the pair of power supply lines 11 and 12 and the housing 18 (ground potential) via amplifier 52 of active filter compensation circuit 23, so that the output voltage of inverting amplifier circuit 37 (amplifier 32) is applied to Y capacitors 21 and 22 as a compensation voltage, and the output voltage of inverting amplifier circuit 57 (amplifier 52) is applied to Y capacitors 41 and 42 as a compensation voltage.

[0037] (3) Function (operation) of the active filter device 1 Next, the operation (performance) of the active filter device 1 of this embodiment, configured as described above, will be described with reference to FIGS. 2 to 4. In FIGS. 3 and 4, the same reference numerals are used to designate the same elements as in FIGS. 1 and 2. FIG. 3 shows an equivalent circuit of the active filter device 1. In FIG. 3, the reference numerals are used to designate the elements related to the inverting amplifier circuit 37, but the same applies to the other inverting amplifier circuit 57. That is, in the case of the inverting amplifier circuit 57 shown in FIG. 3, Y capacitors 21 and 22 are replaced with Y capacitors 41 and 42, amplifier 37 is replaced with amplifier 57, negative feedback resistor 33 is replaced with negative feedback resistor 53, and common-mode voltage detection resistor 36 is replaced with common-mode resistance detection resistor 56.

[0038] Regarding the parasitic inductance 51 described below, it is assumed that the parasitic inductances of the Y capacitors 41 and 42 are placed in the same positions as in FIG. 3, with different inductance values. That is, in an actual circuit, the Y capacitors 21 and 22 have a parasitic inductance 51 (L stray _ Cy ) (The Y capacitors 21 and 22 actually have an inductance value L stray _ Cy1 In Figure 3, the common mode voltage (HV common mode voltage) appearing on the power supply lines 11 and 12 is expressed as v HV _ com , the compensation voltage of the inverting amplifier circuit 37 is v comp _ com Since the input terminal of the inverting amplifier circuit 37 to which the common mode voltage detection resistor 36 is connected is a virtual ground, the common mode voltage (HV common mode voltage) v HV _ com can be expressed by the following mathematical formula (I).

[0039] In addition, R sense is the resistance value of the common-mode voltage detection resistor, and for a common-mode voltage detection resistor of 36, R sense1 is substituted (same below). Also, C sense is the capacitance value of the common-mode voltage detection capacitors 26 and 27, and C sense(×2) means the combined capacitance value of these. Furthermore, G1 is the gain of the inverting amplifier circuit 37, and G1=R f _ com / R sense This R f _ com is the resistance value of the negative feedback resistor, and in the case of negative feedback resistor 33, R f _ com1 is assigned.

[0040] Also, L stray _ Cy is the inductance value of the parasitic inductance 51, and L stray _ Cy (×1 / 2) means the combined inductance value. C Y is the capacitance value of the Y capacitor, C Y (×2) means the combined capacitance value of these, and in the case of the Y capacitors 21 and 22, C Y1 , C Y1 (×2) is substituted respectively (the same applies below). Furthermore, I CY is the current flowing through the Y capacitor, and the current flowing through the Y capacitors 21 and 22 is I CY1 This becomes:

[0041]

number

[0042] From the formula (I), the following formula (II) is established.

[0043]

number

[0044] The impedance of the Y capacitor due to the compensation of the active filter compensation circuit 23 is Z Cy Then, the impedance Z Cy is expressed by the following formula (III).

[0045]

number

[0046] Using formulas (I) to (III), impedance Z Cy The combined capacitance value of the common mode voltage detection capacitors 26 and 27 is C sense (×2), resistance value R of common mode voltage detection resistor sense , the combined capacitance value of the Y capacitors C Y (×2), inductance value L of parasitic inductance 51 stray _ Cy This is expressed as the following mathematical formula (IV).

[0047]

number

[0048] Here, in the high frequency range, the capacitance value C of the common mode voltage detection capacitors 26 and 27 is set so that the impedance of the common mode voltage detection capacitors 26 and 27 can be ignored compared to the impedance of the common mode voltage detection resistor. sense and the resistance value of the common mode voltage detection resistor R sense By selecting the above, the formula (IV) can be regarded as the following formula (V).

[0049]

number

[0050] Here, in the present invention, the capacitance value C of the Y capacitors 21 and 22 Y1 The capacitance value C of the Y capacitors 41 and 42 Y2 In this embodiment, the capacitance values ​​C of the Y capacitors 41 and 42 are different from Y2 The capacitance value C of the Y capacitors 21 and 22 Y1 The value selected is 1 / 10 of the value of

[0051] And the impedance Z of the Y capacitors 21 and 22 Cy1 From equation (V), the following equation (VI) is obtained, and the impedance Z of the Y capacitors 41 and 42 is Cy2In the formulas (VI) and (VII), the inductance value of the parasitic inductance of the Y capacitors 21 and 22 is L stray _ Cy1 The gain of the inverting amplifier circuit 37 is represented by G1, and the inductance value of the parasitic inductance of the Y capacitors 41 and 42 is represented by L stray _ Cy2 The gain of the inverting amplifier circuit 57 is indicated by G2.

[0052]

number

[0053]

number

[0054] The above formula (VI) means that it is equivalent to connecting (1+G1) times the number of Y capacitors, and the above formula (VII) means that it is equivalent to connecting (1+G2) times the number of Y capacitors. That is, due to the compensation by the active filter compensation circuit 23, the capacitance values ​​of the Y capacitors 21 and 22 apparently increase by (1+G1) times, and the capacitance values ​​of the Y capacitors 41 and 42 apparently increase by (1+G2) times. Furthermore, the inductance value of the parasitic inductance 51 is equivalently reduced (1 / (1+G1), 1 / (1+G2)).

[0055] As described above, the common mode voltage v detected by the detector 29 HV _ com The output voltages of the inverting amplifier circuits 37 and 57 are converted into a compensation voltage v comp _ com1 , v comp _ com2are applied to the Y capacitors 21, 22 and the Y capacitors 41, 42, respectively, so that the apparent capacitance values ​​of the Y capacitors 21, 22 increase ((1+G1) times) in accordance with the gain G1 of the inverting amplifier circuit 37, and the apparent capacitance values ​​of the Y capacitors 41, 42 increase ((1+G2) times) in accordance with the gain G2 of the inverting amplifier circuit 57.

[0056] The rough dashed line in Figure 4 represents the Y capacitor (capacitance C Y1 ) of the active filter device 1, and the thinnest dashed line indicates the impedance characteristics of the Y capacitors 21 and 22 (capacitance C Y1 ) of the active filter device 1, and the dashed line in the middle indicates the impedance characteristics of the Y capacitors 41 and 42 (capacitance C Y2 ) of the active filter device 1 of the present invention. Y1 ), and Y capacitors 41 and 42 (capacitance C Y2 ) in parallel.

[0057] Furthermore, Z Cy is the impedance of the Y capacitor. As is clear from this figure, according to the active filter device 1 of the present invention, the capacitance value of each of the Y capacitors 21 and 22 appears to increase, and the impedance Z Cy decreases according to the value of gain G1 compared to a conventional passive noise filter (the thinnest dashed line in Figure 4).

[0058] By increasing the apparent capacitance values ​​of the Y capacitors 21 and 22, it is possible to increase the return flow of noise current indicated by the dashed arrow in FIG. 2, reduce the common mode current leaking to the power supply side, and reduce common mode noise, without using a large-capacity Y capacitor or a large common mode choke coil.

[0059] On the other hand, in the case of only the Y capacitors 21 and 22 and the inverting amplifier circuit 37, the inductance component becomes dominant at frequencies higher than the resonance frequency due to resonance with the parasitic inductance of the Y capacitors 21 and 22. As shown by the thinnest dashed line in the figure, the impedance Z Cy On the other hand, as in the present invention, by connecting Y capacitors 41 and 42 having a capacitance value 1 / 10 (in the embodiment) of the Y capacitors 21 and 22, and further using an inverting amplifier circuit 57 with a gain G2 (the gains G1 and G2 can be set individually), the impedance Z in the frequency range higher than the resonant frequency becomes Cy The increase in

[0060] In other words, this invention suppresses the increase in common-mode noise impedance in the high-frequency range caused by the resonant frequency of the Y capacitor, making it possible to more effectively improve the attenuation characteristics of common-mode noise. Furthermore, the gain values ​​(G1, G2) of each inverting amplifier circuit 37, 57 are individually selected depending on the intended use. This makes it possible to adjust the frequency characteristics of the common-mode impedance to match the EMI noise characteristics.

[0061] Furthermore, according to the present invention, by adding an active filter compensation circuit 23 to a conventional passive noise filter consisting of a common mode choke coil and a Y capacitor, the attenuation characteristics of common mode noise can be improved, making the filter highly versatile.

[0062] In the embodiment, the common mode voltage v detected by a single detection unit 29 composed of a pair of common mode voltage detection capacitors 26 and 27 is HV _ com are input to the inverting amplifier circuits 37 and 57, the circuit configuration of the detector 29 can be simplified.

[0063] The active filter device 1 of the present invention is extremely suitable when it is provided integrally with the inverter device 3 in the housing 18 of the electric compressor 2 as in the embodiment.

[0064] Furthermore, in this embodiment, the ground paths 38, 58 of the detection unit 29 and the ground paths 39 of the inverting amplifier circuits 37, 57 are connected separately to the circuit ground 30, which reduces the adverse effect that voltage fluctuations with respect to the circuit ground 30 caused by the operating current of the inverting amplifier circuits 37, 57 have on the detection of the common-mode voltage by the detection unit 29. [Example]

[0065] Next, Fig. 5 shows an electric circuit diagram of an electric compressor 2 and a power supply path to the electric compressor 2 according to another embodiment of the present invention. In this figure, the same reference numerals as in Fig. 1 denote the same or similar functions. In this embodiment, detection units (indicated by reference numerals 29A and 29B) are provided for the inverting amplifier circuit 37 and the inverting amplifier circuit 57 of the active filter compensation circuit 23, respectively.

[0066] In this case, the detection unit 29A for the inverting amplifier circuit 37 includes first common mode voltage detection capacitors 26A and 27A (C sense1 ) and the common mode voltage detection resistor 36 (FIG. 2) connected to the other end of each of them, and the detection unit 29B for the inverting amplifier circuit 57 is composed of second common mode voltage detection capacitors 26B, 27B (C sense2 ) and the common mode voltage detection resistor 56 (FIG. 2) connected to the other end of each of them.

[0067] In this way, by providing detectors 29A and 29B for inverting amplifier circuit 37 and inverting amplifier circuit 57, respectively, there is an advantage that common-mode noise voltage detection characteristics according to the frequency characteristics of each inverting amplifier circuit 37 and 57 can be obtained. [Example]

[0068] Next, Figure 6 shows an electric circuit of another embodiment of the electric compressor 2 of the present invention. In this figure, the same reference numerals as in Figures 1 and 2 denote the same parts. In this embodiment, the ground paths 38, 58 of the detection unit 29 are directly connected to the housing 18 (ground potential), and the ground path 39 of the power supply circuit 34 of the amplifiers 32, 52 (the ground path of the inverting amplifier circuits 37, 57) is connected to the circuit ground 30 as described above.

[0069] As in this embodiment, by setting the housing 18 to ground potential, connecting the circuit ground 30 to the housing 18, connecting the ground paths 38, 58 of the detection unit 29 to the housing 18, and connecting the ground paths 39 of the inverting amplifier circuits 37, 57 to the circuit ground 30, it is possible to reduce the detection error of the detection unit 29 caused by fluctuations in the potential of the circuit ground 30 due to the operating current of the inverting amplifier circuits 37, 57.

[0070] In the embodiment, two sets of Y capacitors (21, 22, 41, 42) are connected, and an inverting amplifier circuit (37, 57) is provided for each set of Y capacitors. However, more sets of Y capacitors may be connected, the capacitance values ​​of the Y capacitors may be different for each set, and more inverting amplifier circuits may be provided for each set of Y capacitors.

[0071] Furthermore, in the embodiment, the active filter device 1 of the present invention is applied to the electric compressor 2 that constitutes the refrigerant circuit of a vehicle air conditioning system, but the invention of claims 1 to 4 is not limited to this, and the present invention is effective for various home / commercial appliances that require reduction of common mode noise. [Explanation of symbols]

[0072] 1. Active filter device 2 Electric compressor 3. Inverter device 4 Inverter housing 7 High voltage battery (DC power supply) 8 motors 11, 12 Power lines 15 Switching element 18 Case 20 Control circuit 21, 22, 41, 42 Y capacitors 23 Active filter compensation circuit 26, 27, 26A, 27A, 26B, 27B Common mode voltage detection capacitors 28 Common mode choke coil 29, 29A, 29B detection unit 30 Circuit Ground 32, 52 amplifier (op-amp alone or op-amp with current amplifier at output) 36, 56 Common mode voltage detection resistor 37, 57 Inverting amplifier circuit 38, 39, 58 Grand Route

Claims

1. a plurality of sets of Y capacitors, one end of each of which is connected to a pair of power supply lines; a common mode choke coil inserted between the pair of power supply lines; a detection unit for detecting a common mode voltage; a plurality of inverting amplifier circuits provided corresponding to the respective sets of Y capacitors, for inverting and amplifying the common mode voltage detected by the detection unit; The capacitance value of the Y capacitor is set to a different value for each set, an output of each of the inverting amplifier circuits connected to the other end of each of the sets of Y capacitors, and an output voltage of each of the inverting amplifier circuits applied as a compensation voltage to each of the sets of Y capacitors.

2. 2. The active filter device according to claim 1, wherein the common-mode voltage detected by the single detector, which is composed of a pair of common-mode voltage detection capacitors, is input to each of the inverting amplifier circuits.

3. 2. The active filter device according to claim 1, wherein the detection unit is provided for each of the inverting amplifier circuits.

4. 4. The active filter device according to claim 1, wherein a ground path of the detection unit and a ground path of the inverting amplifier circuit are connected to a circuit ground separately.

5. 5. An electric compressor comprising: an active filter device according to claim 1; and an inverter device, the active filter device being integrally provided with a housing.

6. The housing is set to a ground potential, and a circuit ground is connected to the housing; 6. The electric compressor according to claim 5, wherein a ground path of the detection unit is connected to the housing, and a ground path of the inverting amplifier circuit is connected to the circuit ground.

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