Active filter device and electric air compressor provided with same

Abstract

[Problem] To provide an active filter device that can solve problems with so-called π-type noise filters and yield satisfactory noise reduction effects spanning from low-frequency to high-frequency regions. [Solution] An active filter device 1 is provided with: a common-mode choke coil 28 inserted in a pair of power-supply lines 11, 12; pre-stage Y capacitors 61, 62 on the common-mode choke coil 28; an active feedback compensation-voltage output circuit 23 having a detection unit 29 that detects a common mode voltage, and an inverting amplifier circuit 37 that inverts and amplifies the common mode voltage detected in the detection unit; and post-stage Y capacitors 21, 22 between the output from the inverting amplifier circuit and the common-mode choke coils. The output voltage of the inverting amplifier circuit is applied to the post-stage Y capacitors as a compensation voltage.

Description

Active filter device and electric compressor equipped with same

[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.

[0002] A passive common mode noise filter intended to reduce common mode noise is a so-called L-type passive noise filter that is composed of a common mode choke coil inserted into a pair of power supply lines and Y capacitors connected between the pair of power supply lines and the ground potential downstream of the common mode choke coil (the output side of the common mode choke coil) (see, for example, Patent Document 1).

[0003] However, the L-type passive filter has a problem in that the noise attenuation performance deteriorates in the high frequency range above the resonance frequency of the capacitance of the Y capacitor and the parasitic inductance.

[0004] On the other hand, there is also a passive type so-called Π type noise filter in which a Y capacitor is connected between a pair of power supply lines and a ground potential in the upstream stage of the common mode choke coil (the input side of the common mode choke coil) (see, for example, Patent Document 2).

[0005] Various common mode noise filters that employ an active system have also been developed (see, for example, Patent Documents 3 and 4).

[0006] Japanese Patent Application Laid-Open No. 2008-78844 Japanese Patent Application Laid-Open No. 2020-516169 Japanese Patent Application Laid-Open No. 2011-135684 Japanese Patent Application Laid-Open No. 2002-204189

[0007] The passive Π-type noise filter has the advantage over the L-type passive filter of reducing the common mode impedance in the high frequency range above the resonant frequency of the Y capacitor, but conversely, the common mode impedance increases in the low frequency range, resulting in a problem of reduced noise attenuation performance.

[0008] 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 solves the problems of so-called Π-type noise filters and can obtain a good noise reduction effect from low to high frequency ranges, and an electric compressor equipped with the same.

[0009] The active filter device of the present invention comprises a common mode choke coil inserted into a pair of power supply lines, front-stage Y capacitors connected between a circuit ground and the pair of power supply lines on the input side of the common mode choke coil, an active feedback compensation voltage output circuit having a detection unit that detects common mode voltage and an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detection unit, and rear-stage Y capacitors connected between the output of the inverting amplifier circuit and the pair of power supply lines on the output side of the common mode choke coil, and the output voltage of the inverting amplifier circuit is applied as a compensation voltage to the rear-stage Y capacitor.

[0010] The active filter device of the present invention according to claim 2 comprises front-stage and rear-stage active feedback compensation voltage output circuits, each having a common mode choke coil inserted in a pair of power supply lines, a detector for detecting a common mode voltage, and an inverting amplifier circuit for inverting and amplifying the common mode voltage detected by the detector; front-stage Y capacitors connected between the output of the inverting amplifier circuit of the front-stage active feedback compensation voltage output circuit and the pair of power supply lines on the input side of the common mode choke coil; and rear-stage Y capacitors connected between the output of the inverting amplifier circuit of the rear-stage active feedback compensation voltage output circuit and the pair of power supply lines on the output side of the common mode choke coil, wherein the output voltage of the inverting amplifier circuit of the front-stage active feedback compensation voltage output circuit is applied as a compensation voltage to the front-stage Y capacitor, and the output voltage of the inverting amplifier circuit of the rear-stage active feedback compensation voltage output circuit is applied as a compensation voltage to the rear-stage Y capacitor.

[0011] The electric compressor of the present invention is characterized in that the active filter device of each of the above-mentioned inventions and the inverter device are provided integrally with the housing.

[0012] The electric compressor of the present invention according to claim 4 is characterized in that in the above invention, the active filter device is configured on a board different from that of the inverter device.

[0013] The electric compressor of the present invention according to claim 5 is characterized in that in the above invention, the active filter device is shielded from the inverter device.

[0014] The active filter device of the present invention comprises a common mode choke coil inserted into a pair of power supply lines, front-stage Y capacitors connected between the circuit ground and the pair of power supply lines on the input side of the common mode choke coil, an active feedback compensation voltage output circuit having a detection unit that detects common mode voltage and an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detection unit, and rear-stage Y capacitors connected between the output of the inverting amplifier circuit and the pair of power supply lines on the output side of the common mode choke coil, and the output voltage of the inverting amplifier circuit is applied to the rear-stage Y capacitors as a compensation voltage, so that the configuration of a so-called Π-type noise filter reduces common mode impedance in the high frequency range above the resonant frequency of the Y capacitor, compared to an L-type passive filter.

[0015] On the other hand, by using a Π-type noise filter configuration, the common mode impedance would increase in the low frequency range below the resonant frequency of the Y capacitor compared to an L-type passive filter if left as is. However, in the present invention, the output voltage of the inverting amplifier circuit of the active feedback compensation voltage output circuit is applied as a compensation voltage to the Y capacitor in the subsequent stage, so that the apparent capacitance value of the Y capacitor in the subsequent stage increases in accordance with the gain of the inverting amplifier circuit.

[0016] By increasing the apparent capacitance of the Y capacitor in this manner, it becomes possible to reduce the common-mode impedance, 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, thereby reducing common-mode noise across the entire measurement frequency range.

[0017] Furthermore, it can be applied to a conventional passive Π-type noise filter consisting of a common mode choke coil and front- and rear-stage Y capacitors to improve the attenuation characteristics of common mode noise, making it highly versatile.

[0018] Here, if the output voltage of the inverting amplifier circuit of the active feedback compensation voltage output circuit is applied as a compensation voltage only to the Y capacitor in the front stage, rather than to the Y capacitor in the rear stage, the common mode impedance will be further reduced in the high frequency range, but the common mode impedance will still increase in the low frequency range.

[0019] Furthermore, according to the active filter device of the present invention, in addition to the features of the first aspect, the output voltage of the inverting amplifier circuit of the active feedback compensation voltage output circuit of the preceding stage is also applied as a compensation voltage to the preceding stage Y capacitor, thereby further reducing the common mode impedance over the entire measurement frequency range and making it possible to reduce common mode noise even more effectively.

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

[0021] In this case, by configuring the active filter device on a substrate different from that of the inverter device, as in the fourth aspect of the present invention, it becomes possible to easily change the filter characteristics to any desired ones according to the specifications.

[0022] Furthermore, by shielding the active filter device from the inverter device as in the fifth aspect of the invention, the influence of the noise source (inverter device) can be suppressed, and the intended noise attenuation effect can be achieved.

[0023] 1 is an electrical circuit diagram of an electric compressor according to an embodiment to which the active filter device of the present invention is applied, and a power supply path to the electric compressor. FIG. 1 is an electrical circuit diagram of the electric compressor of FIG. 1 (Embodiment 1). FIG. 2 is a schematic cross-sectional view of an inverter accommodating portion of the electric compressor of FIG. 1. FIG. 3 is an equivalent circuit diagram of the active filter device of FIG. 2. FIG. 4 is a diagram explaining changes in common mode impedance due to a filter configuration. FIG. 5 is a diagram explaining changes in common mode impedance due to the capacity ratio of the Y capacitors in the front and rear stages of the active filter device of FIG. 1. FIG. 6 is an electrical circuit diagram of an electric compressor according to another embodiment to which the active filter device of the present invention is applied, and a power supply path to the electric compressor (Embodiment 2). FIG. 7 is a diagram explaining changes in common mode impedance due to a filter configuration including FIG.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0025] FIG. 1 shows an electric circuit diagram of an electric compressor 2 according to one embodiment to which the active filter device 1 of the present invention is applied, and a power supply path to the electric compressor 2. FIG. 2 shows an electric circuit diagram of the electric compressor 2. FIG. 3 shows a schematic cross-sectional view of an inverter accommodating section 4 that accommodates an inverter device 3 of the electric compressor 2.

[0026] 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 with this electric compressor 2. In other words, the electric compressor 2 of the embodiment is an inverter-integrated electric compressor.

[0027] The inverter device 3 converts DC voltage from a high-voltage battery 7 (HV, e.g., DC 350 V) mounted on the vehicle as a DC power source into AC voltage of a desired 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 by the inverter device 3.

[0028] (1) Power Supply Path of Electric Compressor 2 In Fig. 1, inverter device 3 is composed of a power supply line 11 connected to the positive side of high-voltage battery 7 and a plurality of switching elements (IGBTs; Fig. 3) 15 connected to a power supply line 12 connected to the negative side. Reference numeral 20 in Fig. 1 denotes a control circuit, and each switching element 15 of 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.

[0029] Reference numeral 14 denotes a vehicle ECU, and 16 denotes a low-voltage battery (12V DC). Based on instructions from the ECU 14, 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.

[0030] Reference numeral 18 denotes a housing (made of die-cast aluminum) of the electric compressor 2. Furthermore, the electric compressor 2 is connected to the high-voltage battery 7 via 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. As a result, the housing 18 is at ground potential and serves as the circuit ground.

[0031] The active filter device 1 of the embodiment includes a common mode choke coil (CMCC) 28 inserted in a pair of power supply lines 11 and 12, and a front-stage Y capacitor (C Y1 ) 61, 62, and a downstream Y capacitor (C Y2 ) 21, 22, and an active feedback compensation voltage output circuit 23 connected between the Y capacitors 21, 22 and the housing 18 (ground potential, circuit ground). The active feedback compensation voltage output circuit 23 also includes common mode voltage detection capacitors 26, 27 (C sense(which constitutes the detection unit 29 in the present invention).

[0032] As described above, the active filter device 1 of the present invention has the common mode choke coil 28, the front-stage Y capacitors 61 and 62, and the rear-stage Y capacitors 21 and 22, and is configured as a so-called Π-type noise filter to which the active feedback compensation voltage output circuit 23 is applied.

[0033] (2) Electrical 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 components. 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 indicated by 31 in Figure 2. A noise current flows through this stray capacitance 31, generating common mode noise.

[0034] 2 also shows details of the active feedback compensation voltage output circuit 23 of the active filter device 1. The active feedback compensation voltage output circuit 23 of the embodiment includes an amplifier 32 and a negative feedback resistor (R f ) 33, 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 sense ) 36. That is, the detection unit 29 is also included in the active feedback compensation voltage output circuit 23.

[0035] The amplifier 32, negative feedback resistor 33, and common-mode voltage detection resistor 36 constitute an inverting amplifier circuit 37 (gain G1) of the present invention. One ends of the common-mode voltage detection capacitors 26 and 27 are connected to a pair of power supply lines 11 and 12 on the output side of the common-mode choke coil 28, respectively, and the other ends of the common-mode voltage detection capacitors 26 and 27 are both connected to one end of the common-mode voltage detection resistor 36. The other end of the common-mode voltage detection resistor 36 is connected to the inverting input terminal (-) of the amplifier 32. The non-inverting input terminal (+) of the amplifier 32 is connected to the casing 18 (ground potential), which serves as the circuit ground, via a ground path 38. This ground path 38 serves as the ground path for the detection unit 29.

[0036] Meanwhile, one ends of the Y capacitors 21 and 22 in the latter stage are connected to a pair of power supply lines 11 and 12 on the output side of the common mode choke coil 28, respectively. The other ends of the Y capacitors 21 and 22 in the latter stage are both connected to the output terminal of the amplifier 32 (the output of the inverting amplifier circuit 37). In this embodiment, the ground path 39 of the power supply circuit 34 of the amplifier 32 is connected to the casing 18 (ground potential), which is the circuit ground, via a ground path 38. This ground path 39 is the ground path of the inverting amplifier circuit 37.

[0037] As a result, each of the Y capacitors 21, 22 in the subsequent stage is connected between the pair of power supply lines 11, 12 on the output side of the common mode choke coil 28 and the housing 18 (ground potential), which is the circuit ground, via the amplifier 32 of the active feedback compensation voltage output circuit 23, and the output voltage of the inverting amplifier circuit 37 (amplifier 32) is applied to the Y capacitors 21, 22 in the subsequent stage as a compensation voltage.

[0038] (3) Structure of Electric Compressor 2 (Inverter Accommodating Section 4) Fig. 3 shows a schematic cross-sectional view of the electric compressor 2. The motor 8 and the compression mechanism driven by the motor 8 are housed in an aluminum die-cast housing 18 shown in Fig. 3. In this embodiment, the high-voltage circuit 41 (Fig. 3) including the inverter device 3, smoothing capacitor 13, etc., and the low-voltage circuit 42 (Fig. 3) including the control circuit 20, etc., are mounted on a control board 43 as shown in Fig. 3.

[0039] On the other hand, the active filter device 1, which is composed of the active feedback compensation voltage output circuit 23, the front-stage Y capacitors 61 and 62, the rear-stage Y capacitors 21 and 22, and the aforementioned common mode choke coil 28, is configured to be provided on an HV filter board 44 that is provided separately from the control board 43.

[0040] As shown in Fig. 3, the control board 43 and HV filter board 44 are disposed in the inverter accommodating section 4 formed at one end of the housing 18 of the electric compressor 2. In this case, the inside of the inverter accommodating section 4 is divided into a first accommodating chamber 4A and a second accommodating chamber 4B by a partition wall 46 formed in the housing 18, with the control board 43 provided in the first accommodating chamber 4A and the HV filter board 44 provided in the second accommodating chamber 4B (Fig. 3). This allows the active filter device 1 to be shielded from the high-voltage circuit 41 including the inverter device 3 and the like and the low-voltage circuit 42 including the control circuit 20 and the like.

[0041] 3, reference numeral 47 denotes an HV connector for connecting the high-voltage battery 7 and the active filter device 1. Reference numeral 48 denotes a bus bar for connecting the wiring of the inverter device 3, the control circuit 20, and the active filter device 1, and has a structure molded from hard synthetic resin. The switching element 15 (IGBT) described above is disposed in the housing 18 so as to dissipate heat, and is connected to the inverter device 3 (high-voltage circuit 41) through the bus bar 48.

[0042] (4) Function (operation) of the active filter device 1 With the above configuration, the function (operation) of the active filter device 1 of this embodiment will be described with reference to Figs. 2 and 4. In Fig. 4, the same reference numerals as in Figs. 1 to 3 denote the same components. Fig. 4 shows an equivalent circuit of the active filter device 1. In an actual circuit, the Y capacitors 61 and 62 in the front stage have a parasitic inductance 63 (L straycy1 ), and the Y capacitors 21 and 22 in the subsequent stage also have a parasitic inductance 51 (L straycy2 ) (Figure 4).

[0043] The common mode voltage (HV common mode voltage) appearing on the power supply lines 11 and 12 is V HVcom , the compensation voltage of the inverting amplifier circuit 37 is v compcom 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 HVcom can be expressed by the following formula (I): sense is the resistance value of the common mode voltage detection resistor 36, 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. G1 is the gain of the inverting amplifier circuit 37, and G1 = R f / R sense This R f is the resistance value of the negative feedback resistor 33.

[0044] Also, L straycy2 is the inductance value of the parasitic inductance 51, and L straycy2 (×1 / 2) means the combined inductance value. Y2 is the capacitance value of the Y capacitors 21 and 22 in the subsequent stage, and C Y2 (×2) means the combined capacitance value of these. Cy2 is the current flowing through the Y capacitors 21 and 22 in the subsequent stage.

[0045] In addition, in FIG. straycy1 is the inductance value of the parasitic inductance 63, and L straycy1(×1 / 2) means the combined inductance value. Y1 is the capacitance value of the Y capacitors 61 and 62 in the preceding stage, and C Y1 (×2) means the combined capacitance value of these. Cy1 is the current flowing through the Y capacitors 61 and 62 in the preceding stage.

[0046]

[0047] From the formula (I), the following formula (II) is established.

[0048]

[0049] The impedance of the Y capacitors 21 and 22 in the subsequent stage due to the compensation of the active feedback compensation voltage output circuit 23 is Z Cy2 Then, the impedance Z Cy2 is expressed by the following formula (III).

[0050]

[0051] Using equations (I) to (III), impedance Z Cy2 The combined capacitance value C of the common mode voltage detection capacitors 26 and 27 sense (x2), the resistance value R of the common mode voltage detection resistor 36 sense , the combined capacitance value C of the Y capacitors 21 and 22 in the subsequent stage Y2 (x2), the inductance value L of the parasitic inductance 51 straycy2 This is expressed as the following formula (IV).

[0052]

[0053] 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 36. sense and the resistance value R of the common mode voltage detection resistor 36 sense By selecting the above, the formula (IV) can be regarded as the following formula (V).

[0054]

[0055] This formula (V) means that it is equivalent to connecting a (1+G1)-fold Y capacitor. That is, due to the compensation by the active feedback compensation voltage output circuit 23, the capacitance values ​​of the subsequent Y capacitors 21 and 22 appear to be increased by a factor of (1+G1). Furthermore, the inductance value of the parasitic inductance 51 is equivalently reduced (1 / (1+G1)).

[0056] As described above, the common mode voltage v detected by the detector 29 HVcom The output voltage of the inverting amplifier circuit 37 is converted into a compensation voltage v compcom is applied to the Y capacitors 21 and 22 in the subsequent stage, the apparent capacitance values ​​of the Y capacitors 21 and 22 in the subsequent stage increase (by (1+G1) times) in accordance with the gain G1 of the inverting amplifier circuit 37.

[0057] The common mode impedance Z of the active filter device 1 of this embodiment com The frequency characteristic of the active filter device 1 is shown by a thick dotted line (Π-Active (rear)) in FIG. com is the common mode voltage v that appears after passing through the active filter device 1. HVcomIN The current I flowing through the Y capacitors 61 and 62 in the preceding stage Cy1 and the current I flowing through the subsequent Y capacitors 21 and 22 Cy2 and is defined by the following formula (VI).

[0058]

[0059] 5, for comparison, the case of the passive L-type noise filter (L-Passive) described above is shown by a thin solid line, and the case of the passive Π-type noise filter (Π-Passive) is shown by a thin dotted line. Here, the total capacitance of the Y capacitors in each type is the same at 9.2 nF, and in the Π-type noise filters, including the active filter device 1 of the embodiment, the capacitance values ​​(composite capacitance value; the same applies below) of the Y capacitors in the front and rear stages of the common mode choke coil are set to the same 4.6 nF.

[0060] Comparing the Π-type noise filter (thick dotted line and thin dotted line) in FIG. 5 with the passive L-type noise filter (thin solid line), the Π-type noise filter (thick dotted line and thin dotted line) has a lower common mode impedance Z than the passive L-type noise filter (thin solid line) in the high frequency range above the resonant frequency due to the action of the Y capacitor in the front stage (Y capacitors 61 and 62 in the embodiment of the present invention shown by the thick dotted line). com It can be seen that is decreasing.

[0061] However, in the passive Π-type noise filter (thin dotted line), the common mode impedance is conversely greater in the low frequency range than the passive L-type noise filter (thin solid line).

[0062] On the other hand, according to the active filter device 1 of the present invention, the apparent capacitance value of the Y capacitors 21 and 22 in the subsequent stage increases ((1+G1) times) as described above, and the impedance Z Cy2 decreases in accordance with the value of the gain G1 compared to a normal passive Π type noise filter. Due to the increase in the apparent capacitance of the Y capacitors 21 and 22 in the subsequent stage, the common mode impedance Z com As shown by the thick dotted line in FIG. 5, is reduced compared to the case of the passive L-type noise filter (thin solid line) (FIG. 5).

[0063] Here, FIG. 6 shows the common mode impedance Z when the capacitance values ​​of the Y capacitors 61 and 62 in the front stage and the Y capacitors 21 and 22 in the rear stage of the active filter device 1 of the present invention are changed. comThe figure also shows the frequency characteristics of a passive L-type noise filter (L-Passive). The thin dotted line represents the case where the combined capacitance of the front-stage and rear-stage Y capacitors 61, 62, 21, and 22 is the same at 4.6 nF. The thick solid line represents the case where the combined capacitance of the front-stage Y capacitors 61 and 62 is 8.2 nF (large) and the combined capacitance of the rear-stage Y capacitors 21 and 22 is 1 nF (small). The thick dotted line represents the case where the combined capacitance of the front-stage Y capacitors 61 and 62 is 1 nF (small) and the combined capacitance of the rear-stage Y capacitors 21 and 22 is 8.2 nF (large).

[0064] As is clear from this figure, in the case of the active filter device 1 of the present invention, by changing the capacitance values ​​of the Y capacitors 61, 62, 21, and 22 in the front and rear stages, the common mode impedance Z com For example, in the case of the thick solid line (the combined capacitance of the Y capacitors 61 and 62 in the front stage is 8.2 nF (large) and the combined capacitance of the Y capacitors 21 and 22 in the rear stage is 1 nF (small)), the common mode impedance Z is larger in the high frequency range than in the case of the thin dotted line (the combined capacitance of the Y capacitors 61, 62, 21, and 22 in the front and rear stages is the same, 4.6 nF). com Although there are some areas where the noise level is low, in the low frequency range it tends to increase more than with other methods.

[0065] In addition, in the case of the thick dotted line (the combined capacitance of the front-stage Y capacitors 61 and 62 is 1 nF (small), and the combined capacitance of the rear-stage Y capacitors 21 and 22 is 8.2 nF (large)), the common mode impedance Z is larger in the higher frequency range and the lower frequency range than in the case of the thin dotted line (the combined capacitance of the front-stage and rear-stage Y capacitors 61, 62, 21, and 22 is the same 4.6 nF in both the front and rear stages). com Although there are some points where the frequency is low, it tends to increase in the intermediate frequency range including the resonance point.

[0066] Therefore, the capacitance values ​​of the Y capacitors 61 and 62 at the front stage and the Y capacitors 21 and 22 at the rear stage of the active filter device 1 should be selected according to the device to be used, that is, the frequency of the common mode noise to be reduced.

[0067] As described above, according to the active filter device 1 of the present invention, the common mode impedance Z is low in a high frequency range above the resonant frequency of the Y capacitor due to the configuration of a so-called Π type noise filter. com On the other hand, by configuring the Π-type noise filter, the common mode impedance Z com However, in the present invention, the output voltage of the inverting amplifier circuit 37 of the active feedback compensation voltage output circuit 23 is applied as a compensation voltage to the Y capacitors 21 and 22 in the subsequent stage, so that the apparent capacitance values ​​of the Y capacitors 21 and 22 in the subsequent stage increase in accordance with the gain of the inverting amplifier circuit 37.

[0068] By increasing the apparent capacitance of the Y capacitors 21 and 22 in the subsequent stage, the common mode impedance Z com This reduces the common mode noise across the entire measurement frequency range, increasing the return flow of noise current and reducing the common mode current leaking to the power supply.

[0069] Furthermore, it can be applied to a normal passive Π-type noise filter consisting of a common mode choke coil 28 and front-stage and rear-stage Y capacitors 61, 62, 21, 22 to improve the attenuation characteristics of common mode noise, making it highly versatile.

[0070] The active filter device 1 of the present invention is extremely suitable when it is integrally provided in the housing 18 of the electric compressor 2 together with the inverter device 3, as in the embodiment. In this case, in the embodiment, the active filter device 1 is configured on the HV filter board 44, which is different from the control board 43 on which the inverter device 3 is provided, and therefore the filter characteristics can be easily changed to any desired value depending on the specifications.

[0071] Furthermore, in this embodiment, the HV filter board 44 (active filter device 1) is shielded by a partition wall 46 from the control board 43 on which the inverter device 3 is mounted, thereby suppressing the influence of the noise source (inverter device 3) and achieving the intended noise attenuation effect.

[0072] Next, an active filter device 1 according to another embodiment of the present invention will be described with reference to Figures 7 and 8. In each figure, components denoted by the same reference numerals as those in Figures 1 to 6 have the same or similar functions. In addition to the configuration of the above-described embodiment (Embodiment 1), the active filter device 1 of this embodiment includes another active feedback compensation voltage output circuit 23A.

[0073] In this embodiment, the active feedback compensation voltage output circuit 23 in the previously described embodiment is the subsequent active feedback compensation voltage output circuit of the present invention, and the active feedback compensation voltage output circuit 23A added in this embodiment is the subsequent active feedback compensation voltage output circuit of the present invention. Also, the previous active feedback compensation voltage output circuit 23A has the same configuration as the previous active feedback compensation voltage output circuit 23.

[0074] In this embodiment, the Y capacitor (C Y1 ) 61, 62 are connected between a pair of power supply lines 11, 12 on the input side of the common mode choke coil 28 and the output of the preceding active feedback compensation voltage output circuit 23A, respectively.

[0075] In this case as well, each of the Y capacitors 61, 62 in the preceding stage is connected between the pair of power supply lines 11, 12 and the housing 18 (ground potential), which is the circuit ground, via the amplifier 32 of the preceding active feedback compensation voltage output circuit 23A, and the output voltage of the inverting amplifier circuit 37 (amplifier 32) of the preceding active feedback compensation voltage output circuit 23A is applied to the preceding Y capacitors 61, 62 as a compensation voltage.

[0076] The action of the front-stage active feedback compensation voltage output circuit 23A on the front-stage Y capacitors 61, 62 is similar to the action of the rear-stage active feedback compensation voltage output circuit 23 on the rear-stage Y capacitors 21, 22 described above, so a detailed explanation will be omitted, but in this embodiment as well, the capacitance values ​​of the front-stage Y capacitors 61, 62 appear to increase due to the front-stage active feedback compensation voltage output circuit 23A.

[0077] 8 shows the common mode impedance Z in the case where the subsequent active feedback compensation voltage output circuit 23 is connected only to the subsequent Y capacitors 21 and 22 as in the first embodiment, the case where the previous active feedback compensation voltage output circuit 23A is connected only to the previous Y capacitors 61 and 62, and the case where the previous active feedback compensation voltage output circuit 23A and the subsequent active feedback compensation voltage output circuit 23 are connected to the previous Y capacitors 61 and 62 and the subsequent Y capacitors 21 and 22, respectively as in the second embodiment. com The frequency characteristics of

[0078] In this figure, the thin solid line indicates the case of a passive L-type noise filter (L-Passive). The thin dotted line indicates the case of a passive Π-type noise filter (Π-Passive). The thick dotted line indicates the case where the rear-stage active feedback compensation voltage output circuit 23 is connected only to the rear-stage Y capacitors 21 and 22 (Π-Active (rear)), as in Example 1. The dash-dot line indicates the case where the front-stage active feedback compensation voltage output circuit 23A is connected only to the front-stage Y capacitors 61 and 62 (Π-Active (front)). The thick solid line indicates the case where the front-stage active feedback compensation voltage output circuit 23A and the rear-stage active feedback compensation voltage output circuit 23 are connected to the front-stage Y capacitors 61 and 62 and the rear-stage Y capacitors 21 and 22, respectively (Π-Active (both)), as in Example 2. In this case, the total capacitance of the Y capacitors is also set to 9.2 nF, and the combined capacitance of the front and rear Y capacitors in the Π type is also set to 4.6 nF.

[0079] As is clear from this figure, when the preceding active feedback compensation voltage output circuit 23A is connected only to the preceding Y capacitors 61 and 62 (dotted line in FIG. 8), the common mode impedance Z is lower in the lower frequency range than in the case of the passive L-type noise filter (thin solid line in FIG. 8) or the passive Π-type noise filter (thin dotted line in FIG. 8). com is increasing.

[0080] On the other hand, when the front-stage active feedback compensation voltage output circuit 23A and the rear-stage active feedback compensation voltage output circuit 23 are connected to the front-stage Y capacitors 61 and 62 and the rear-stage Y capacitors 21 and 22, respectively, as in Example 2 (thick solid line in FIG. 8), the common mode impedance Z is lower than in Example 1 (thick dotted line in FIG. 8) in the low frequency range. com It can be seen that the common mode noise can be further reduced.

[0081] That is, in addition to applying the output voltage of the inverting amplifier circuit 37 of the active feedback compensation voltage output circuit 23A of the subsequent stage to the subsequent stage Y capacitors 21 and 22 as a compensation voltage as in this embodiment, if the output voltage of the inverting amplifier circuit 37 of the active feedback compensation voltage output circuit 23A of the previous stage is also applied to the previous stage Y capacitors 61 and 62 as a compensation voltage, the common mode impedance Z com This reduces the common mode noise and makes it possible to reduce the common mode noise even more effectively.

[0082] In each 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 conditioner, but the inventions of claims 1 and 2 are not limited to this, and the present invention is effective in various home and commercial appliances that require reduction of common mode noise.

[0083] REFERENCE SIGNS LIST 1 active filter device 2 electric compressor 3 inverter device 4 inverter housing 7 high-voltage battery (DC power supply) 8 motor 11, 12 power supply line 15 switching element 18 housing (circuit ground) 20 control circuit 21, 22 subsequent stage Y capacitor 23 active feedback compensation voltage output circuit (subsequent stage active feedback compensation voltage output circuit) 23A previous stage active feedback compensation voltage output circuit 26, 27 common mode voltage detection capacitor 28 common mode choke coil 29 detection unit 32 amplifier 36 common mode voltage detection resistor 37 inverting amplifier circuit 38, 39 ground path 43 control board 44 HV filter board 46 partition wall 61, 62 previous stage Y capacitor

Claims

1. An active filter device comprising: a common mode choke coil inserted into a pair of power supply lines; a front-stage Y capacitor connected between a circuit ground and the pair of power supply lines on the input side of the common mode choke coil; an active feedback compensation voltage output circuit having a detection unit that detects common mode voltage and an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detection unit; and a rear-stage Y capacitor connected between the output of the inverting amplifier circuit and the pair of power supply lines on the output side of the common mode choke coil, wherein the output voltage of the inverting amplifier circuit is applied to the rear-stage Y capacitor as a compensation voltage.

2. An active filter device comprising: a common mode choke coil inserted between a pair of power supply lines; front-stage and rear-stage active feedback compensation voltage output circuits each having a detection unit which detects a common mode voltage and an inverting amplifier circuit which inverts and amplifies the common mode voltage detected by the detection unit; a front-stage Y capacitor connected between the output of the inverting amplifier circuit of the front-stage active feedback compensation voltage output circuit and the pair of power supply lines on the input side of the common mode choke coil; and a rear-stage Y capacitor connected between the output of the inverting amplifier circuit of the rear-stage active feedback compensation voltage output circuit and the pair of power supply lines on the output side of the common mode choke coil, wherein the output voltage of the inverting amplifier circuit of the front-stage active feedback compensation voltage output circuit is applied as a compensation voltage to the front-stage Y capacitor, and the output voltage of the inverting amplifier circuit of the rear-stage active feedback compensation voltage output circuit is applied as a compensation voltage to the rear-stage Y capacitor.

3. An electric compressor comprising the active filter device according to claim 1 or 2 and an inverter device, which are integrally provided with a housing.

4. The electric compressor according to claim 3, wherein the active filter device is configured on a substrate different from that on which the inverter device is configured.

5. The electric compressor according to claim 4, wherein the active filter device is shielded from the inverter device.

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