Active filter device and electric compressor equipped with same

Abstract

To provide an active filter device capable of effectively reducing common mode noise and differential mode noise to optimize filter characteristics.SOLUTION: An active filter device includes an inverting amplifier circuit 37 for inverting and amplifying a common mode voltage and a differential amplifier circuit 64 for differentially amplifying a differential mode voltage. An output voltage of the inverting amplifier circuit 37 is applied to Y capacitors 21 and 22 as a common mode compensation voltage. An output obtained by amplifying voltage of a power supply line 11 on a positive side of the differential amplifier circuit 64 is applied to an X capacitor 42 on a negative side as a differential mode compensation voltage. An output obtained by amplifying voltage of a power supply line 12 on a negative side of the differential amplifier circuit 64 is applied to an X capacitor 41 on a positive side as the differential mode compensation voltage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an active filter device for suppressing common mode noise and differential 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 and 3). [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. 5528543 [Patent Document 4] Japanese Patent Application Publication No. 2019-205286 Summary of the Invention [Problem to be solved by the invention]

[0006] However, all of the above documents require a common mode transformer for detecting and compensating for common mode noise, which increases the size of the active filter device, and therefore improvements have been desired.

[0007] Furthermore, in actual circuits, differential mode noise increases due to mode conversion caused by circuit imbalance in the differential mode path, etc. Passive differential mode noise filters designed to reduce this differential mode noise consist of an X capacitor connected between a pair of power supply lines and normal mode choke coils connected to each of the pair of power supply lines (see, for example, Patent Document 4), but there has been a demand for the development of an active filter device that can reduce this differential mode noise as well as the aforementioned common mode noise.

[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 can effectively reduce common mode noise and differential mode noise and optimize filter characteristics, and an electric compressor equipped with the same. [Means for solving the problem]

[0009] The active filter device of the present invention comprises a common mode choke coil inserted in a pair of positive and negative power supply lines, a normal mode choke coil connected to the pair of power supply lines or one of them, a detection unit that detects the voltage of the pair of power supply lines, an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detection unit, Y capacitors connected between the output of the inverting amplifier circuit and the pair of power supply lines, a differential amplifier circuit that differentially amplifies the differential mode voltage between the pair of power supply lines detected by the detection unit, and X capacitors connected between the output of the differential amplifier circuit and the pair of power supply lines, and is characterized in that the output voltage of the inverting amplifier circuit is applied to the Y capacitor, the output voltage of the differential amplifier circuit obtained by amplifying the voltage of the positive power supply line is applied to the X capacitor connected to the negative power supply line, and the output voltage of the differential amplifier circuit obtained by amplifying the voltage of the negative power supply line is applied to the X capacitor connected to the positive power supply line.

[0010] The active filter device of the invention of claim 2 is characterized in that in the above invention, the differential amplifier circuit has a positive-side amplifier, the voltage of the positive-side power supply line detected by the detection unit being input to the non-inverting input terminal as a differential input signal, and a negative-side amplifier, the voltage of the negative-side power supply line detected by the detection unit being input to the non-inverting input terminal as a differential input signal, and the X capacitor connected to the negative-side power supply line is connected to the output of the positive-side amplifier, and the X capacitor connected to the positive-side power supply line is connected to the output of the negative-side amplifier.

[0011] The active filter device of the invention of claim 3 is characterized in that in each of the above inventions, a voltage detected by a single detection unit composed of a pair of voltage detection capacitors is input to an inverting amplifier circuit and a differential amplifier circuit.

[0012] The active filter device of the invention of claim 4 is characterized in that in the invention of claim 1 or claim 2, the detection section is provided for each of the inverting amplifier circuit and the differential amplifier circuit.

[0013] The active filter device of the present invention according to claim 5 is characterized in that in each of the above inventions, the ground path of the detection unit and the ground path of the inverting amplifier circuit are connected to the circuit ground separately.

[0014] The electric compressor of the invention of claim 6 is characterized in that the active filter device of each of the above inventions and the inverter device are provided integrally with the housing.

[0015] The electric compressor of the invention of claim 7 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]

[0016] The active filter device of the present invention includes a common mode choke coil inserted in a pair of positive and negative power supply lines, a normal mode choke coil connected to the pair of power supply lines or one of the pair of power supply lines, a detection unit that detects the voltage of the pair of power supply lines, an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detection unit, Y capacitors connected between the output of the inverting amplifier circuit and the pair of power supply lines, a differential amplifier circuit that differentially amplifies the differential mode voltage between the pair of power supply lines detected by the detection unit, and X capacitors connected between the output of the differential amplifier circuit and the pair of power supply lines, and the output voltage of the inverting amplifier circuit is applied to the Y capacitor, and the output voltage obtained by amplifying the voltage of the positive power supply line of the differential amplifier circuit is applied to the X capacitor connected to the negative power supply line, and the output voltage obtained by amplifying the voltage of the negative power supply line of the differential amplifier circuit is applied to the X capacitor connected to the positive power supply line.

[0017] This causes the apparent capacitance of the Y capacitor to increase according to the gain of the inverting amplifier circuit. 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.

[0018] Furthermore, the apparent capacitance of the X capacitor also increases according to the gain of the differential amplifier circuit. This increase in the apparent capacitance of the X capacitor makes it possible to increase the return flow of noise current and reduce the differential mode current leaking to the power supply without using a large-capacity X capacitor or a large normal mode choke coil.

[0019] Furthermore, it can be applied to a conventional passive noise filter consisting of a common mode choke coil, a normal mode choke coil, a Y capacitor, and an X capacitor to improve the attenuation characteristics of common mode noise and differential mode noise, making it highly versatile.

[0020] In particular, because the compensation voltage output gains of the inverting amplifier circuit and the differential amplifier circuit can be set separately, it is possible to optimize the filter characteristics by selecting and combining filter circuit elements (Y capacitors, X capacitors, common mode choke coils, normal mode choke coils) according to the differences in EMI characteristics depending on the mode.

[0021] In this case, as in the invention of claim 2, the differential amplifier circuit is actually composed of a positive amplifier, whose non-inverting input terminal receives the voltage of the positive power supply line detected by the detection unit as a differential input signal, and a negative amplifier, whose non-inverting input terminal receives the voltage of the negative power supply line detected by the detection unit as a differential input signal, and the X capacitor connected to the negative power supply line is connected to the output of the positive amplifier, and the X capacitor connected to the positive power supply line is connected to the output of the negative amplifier, thereby increasing the apparent capacitance value of the X capacitor.

[0022] Furthermore, as in the invention of claim 3, by configuring the voltage detected by a single detection unit consisting of a pair of voltage detection capacitors to be input to an inverting amplifier circuit and a differential amplifier circuit, the circuit configuration of the detection unit can be simplified.

[0023] On the other hand, if a detection unit is provided for each of the inverting amplifier circuit and the differential amplifier circuit as in the invention of claim 4, there is an advantage that noise voltage detection characteristics according to the frequency characteristics of the common mode and differential mode can be obtained.

[0024] Furthermore, as in the invention of claim 5, 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.

[0025] 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 sixth invention.

[0026] Furthermore, as in the invention of claim 7, 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 eliminate 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]

[0027] [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] 3 is an equivalent circuit diagram relating to common-mode voltage compensation of the active filter device of FIG. 2. FIG. [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] 1A and 1B are diagrams illustrating the common-mode noise reduction effect of the active filter device of the present invention. [Figure 6] FIG. 3 is an equivalent circuit diagram relating to differential mode voltage compensation of the active filter device of FIG. 2. [Figure 7] FIG. 10 is a diagram showing the impedance characteristics of an X capacitor for explaining the differential mode noise reduction effect of the active filter device of the present invention. [Figure 8] 1 and an electric circuit of a power supply path to the electric compressor according to another embodiment (Embodiment 2). [Figure 9] 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

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0029] Fig. 1 shows an electric compressor 2 according to one embodiment to which an active filter device 1 of the present invention is applied, and an electrical circuit diagram of the power supply path to the electric compressor 2, and Fig. 2 shows an electrical circuit diagram of the electric compressor 2. The electric compressor 2 of the embodiment is mounted on a vehicle such as an electric vehicle or hybrid vehicle and forms part of a refrigerant circuit of a vehicle air conditioner that conditions the interior of the vehicle, and an inverter device (PWM inverter) 3 and the active filter device 1 of the present invention are provided integrally with a housing 18 of the electric compressor 2, which will be described later. In other words, the electric compressor 2 of the embodiment is an inverter-integrated electric compressor.

[0030] 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 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 and differential mode noise generated in the inverter device 3.

[0031] (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.

[0032] 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.

[0033] The active filter device 1 of the embodiment includes a dual-mode active filter compensation circuit 23 and Y capacitors (C Y ) 21, 22, and X capacitor (C X ) 41, 42, and voltage detection capacitors 26, 27 (C sense: constituting the detection unit 29 in the present invention), a common mode choke coil (CMCC) 28 inserted in the pair of power supply lines 11, 12 on the high-voltage battery 7 side as viewed from the Y capacitors 21, 22, X capacitors 41, 42, dual mode active filter compensation circuit 23, and voltage detection capacitors 26, 27, and normal mode choke coils (NMCC) 43, 44 respectively connected to the pair of power supply lines 11, 12 on the smoothing capacitor 13 (inverter device 3) side as viewed from the Y capacitors 21, 22, X capacitors 41, 42, dual mode active filter compensation circuit 23, and voltage detection capacitors 26, 27.

[0034] In this case, for the Y capacitors 21, 22, the dual mode active filter compensation circuit 23 is connected between the Y capacitors 21, 22 and the housing 18 (ground potential). On the other hand, for the X capacitors 41, 42, the dual mode active filter compensation circuit 23 is inserted between the X capacitors 41, 42. Also, in the embodiment, the normal mode choke coils 43, 44 are connected to the pair of power supply lines 11, 12, respectively, but it is also possible to connect either one of the normal mode choke coils 43, 44 to only one of the power supply lines 11, 12.

[0035] (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.

[0036] (2-1) Dual-mode active filter compensation circuit 23 2 also shows details of the dual-mode active filter compensation circuit 23 of the active filter device 1. The dual-mode active filter compensation circuit 23 of the embodiment constitutes the main components of the common-mode voltage compensation section 52 and the differential-mode voltage compensation section 53.

[0037] (2-2) Common mode voltage compensation unit 52 Of these, the common mode voltage compensation unit 52 includes an amplifier 32 and a negative feedback resistor (R f _ com ) 33, and a power supply circuit (V CC , V EE ) 34 (which is included in the dual mode active filter compensation circuit 23), the Y capacitors 21 and 22, and the common mode choke coil 28.

[0038] The amplifier 32, the negative feedback resistor 33, and the common mode voltage detection resistor 36 constitute an inverting amplifier circuit 37 (gain G1) of the present invention. One end of the voltage detection capacitors 26 and 27 is connected to the pair of power supply lines 11 and 12, respectively, and the other end of the voltage detection capacitors 26 and 27 is connected to the voltage detection voltage dividing resistor (R div1 )56 and (R div2 ) 57, and both are connected to the common mode voltage detection resistor (R sense ) 36. These two sets of voltage detection voltage dividing resistors 56 and 57 and the common mode voltage detection resistor 36 together with the voltage detection capacitors 26 and 27 constitute the detection unit 29.

[0039] The other end of this common-mode voltage detection resistor 36 is connected to the inverting input terminal (-) of the amplifier 32. In this embodiment, the non-inverting input terminal (+) of the amplifier 32 is connected to the circuit ground 30 via a ground path 38. This ground path 38 serves as the ground path for the detection unit 29. The circuit ground 30 is connected to the housing 18, which is at ground potential.

[0040] Meanwhile, one ends of the aforementioned Y capacitors 21 and 22 are connected to the pair of power supply lines 11 and 12, respectively. The other ends of these Y capacitors 21 and 22 are both connected to the output terminal of amplifier 32. In this embodiment, a ground path 39 of power supply circuit 34 of amplifier 32 is connected to circuit ground 30 separately from ground path 38. This ground path 39 is the ground path of inverting amplifier circuit 37. As a result, each of Y capacitors 21 and 22 is connected between the pair of power supply lines 11 and 12 and housing 18 (ground potential) via amplifier 32 of inverting amplifier circuit 37, and the output voltage of inverting amplifier circuit 37 (amplifier 32) is applied to Y capacitors 21 and 22 as a common-mode compensation voltage.

[0041] (2-3) Differential mode voltage compensation unit 53 On the other hand, the differential mode voltage compensation unit 53 includes two amplifiers 58 and 59 on the positive and negative sides, and feedback resistors (R f _ dif1 ) 61 and a feedback resistor (R f _ dif2 ) 62, and a power supply circuit (V CC , V EE ) 63 (these are included in the dual mode active filter compensation circuit 23), the above-mentioned X capacitors 41 and 42, and normal mode choke coils 43 and 44. Amplifiers 58 and 59 and feedback resistors 61 and 62 constitute a differential amplifier circuit (differential input differential amplifier circuit) 64 (gain G2) of the present invention.

[0042] The voltage between voltage detection voltage divider resistors 56 and 57 connected to voltage detection capacitor 26 connected to positive power supply line 11 is input as a differential input signal to the non-inverting input terminal (+) of amplifier 58 (positive side amplifier), and the voltage between voltage detection voltage divider resistors 56 and 57 connected to voltage detection capacitor 27 connected to negative power supply line 12 is input as a differential input signal to the non-inverting input terminal (+) of amplifier 59 (negative side amplifier).

[0043] On the other hand, one end of each of the X capacitors 41 and 42 is connected to a pair of power supply lines 11 and 12, respectively. The other end of the X capacitor 41 (positive-side X capacitor) connected to the positive-side power supply line 11 is connected to the output terminal of the negative-side amplifier 59, and the other end of the X capacitor 42 (negative-side X capacitor) connected to the negative-side power supply line 12 is connected to the output terminal of the positive-side amplifier 58.

[0044] As a result, differential amplifier circuit 64 is inserted between X capacitors 41 and 42, and the output of positive-side amplifier 58 of differential amplifier circuit 64 (positive-side differential amplification output) is applied as a differential mode compensation voltage to X capacitor 42 (negative-side X capacitor) connected to negative-side power supply line 12, and the output of negative-side amplifier 59 of differential amplifier circuit 64 (negative-side differential amplification output) is applied as a differential mode compensation voltage to X capacitor 41 (positive-side X capacitor) connected to positive-side power supply line 11.

[0045] (3) Function (operation) of the active filter device 1 With the above configuration, the operation (performance) of the active filter device 1 of this embodiment will now be described with reference to Figures 2 to 7. In Figures 3 to 7, the same reference numerals as in Figures 1 and 2 denote the same parts.

[0046] (3-1) Function (operation) of the common mode voltage compensator 52 First, the function (operation) of the common mode voltage compensating section 52 will be described with reference to Figs. 3 to 5. Fig. 3 shows an equivalent circuit of the common mode voltage compensating section 52 of the active filter device 1. In an actual circuit, the Y capacitors 21 and 22 have a parasitic inductance 51 (L stray _ Cy ) (FIG. 3). In the following explanation, the resistance of the voltage division detection resistors 56 and 57 is the same as the resistance value R of the common mode voltage detection resistor 36. sense shall be considered to be included in the above.

[0047] The common mode voltage (HV common mode voltage) appearing on the power supply lines 11 and 12 is v HV _ com , the common mode 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 formula (I): sense is the resistance value of the common-mode voltage detection resistor 36, C sense is the capacitance value of the 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 _ com / R sense This R f _ com is the resistance value of the negative feedback resistor 33.

[0048] 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 capacitors 21 and 22, and C Y (×2) means the combined capacitance value of these. CY is the current flowing through the Y capacitors 21 and 22.

[0049]

number

[0050] From the formula (I), the following formula (II) is established.

[0051]

number

[0052] The impedance of the Y capacitors 21 and 22 due to the compensation of the inverting amplifier circuit 37 of the dual mode active filter compensation circuit 23 is Z Cy Then, the impedance Z Cy is expressed by the following mathematical formula (III).

[0053]

number

[0054] Using formulas (I) to (III), impedance Z Cy The combined capacitance value of the voltage detection capacitors 26 and 27 is C sense (×2), resistance value R of common mode voltage detection resistor 36 sense , the combined capacitance value C of the Y capacitors 21 and 22 Y (×2), inductance value L of parasitic inductance 51 stray _ Cy This is expressed as the following mathematical formula (IV).

[0055]

number

[0056] Here, in the high frequency range, the capacitance value C of the voltage detection capacitors 26 and 27 is set so that the impedance of the 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 senseBy selecting the above, the formula (IV) can be regarded as the following formula (V).

[0057]

number

[0058] This formula (V) means that it is equivalent to connecting a (1+G1)-fold Y capacitor. That is, due to the compensation by the inverting amplifier circuit 37 of the dual-mode active filter compensation circuit 23, the capacitance values ​​of the Y capacitors 21 and 22 appear to increase by a factor of (1+G1). Furthermore, the inductance value of the parasitic inductance 51 is equivalently reduced (1 / (1+G1)).

[0059] As described above, the common mode voltage v detected by the detector 29 HV _ com The output voltage of the inverting amplifier circuit 37 is converted into a common mode compensation voltage v comp _ com is applied to the Y capacitors 21 and 22, the apparent capacitance values ​​of the Y capacitors 21 and 22 increase (by (1+G1) times) in accordance with the gain G1 of the inverting amplifier circuit 37.

[0060] The dashed line in FIG. 4 indicates the impedance characteristics of the Y capacitor of a normal passive noise filter, and the solid line indicates the impedance characteristics of the Y capacitor of the active filter device 1 of the present invention. 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 the Y capacitor apparently increases, and the impedance Z Cy decreases according to the value of gain G1 more than in a normal passive noise filter (Figure 4 shows the change in impedance when G1=3).

[0061] By increasing the apparent capacitance values ​​of the Y capacitors 21 and 22, it becomes possible to increase the return flow of the common-mode noise current indicated by the dashed arrow in FIG. 2, reduce the common-mode current leaking to the power supply side, and reduce the common-mode noise, without using a large-capacity Y capacitor or a large common-mode choke coil.

[0062] 5, the black areas indicate the common-mode noise level of a conventional passive noise filter, and the shaded areas indicate the common-mode noise level of the active filter device 1 of the present invention. As is clear from this figure, the common-mode noise level of the active filter device 1 of the present invention is lower than that of a conventional passive noise filter in accordance with the decrease in the impedance of the Y capacitor.

[0063] In particular, by adding the dual mode active filter compensation circuit 23 to a normal passive noise filter consisting of a common mode choke coil 28 and Y capacitors 21 and 22, the attenuation characteristics of common mode noise can be improved, making it highly versatile.

[0064] (3-2) Function (operation) of differential mode voltage compensator 53 Next, the operation of the differential mode voltage compensator 53 will be described with reference to Figures 6 and 7. Figure 6 shows an equivalent circuit of the differential mode voltage compensator 53 of the active filter device 1. In an actual circuit, the X capacitors 41 and 42 have a parasitic inductance 66 (L stray _ CX ) (Figure 6).

[0065] The differential mode voltage (HV differential mode voltage) appearing between the power supply lines 11 and 12 is defined as v HV _ dif , the voltage between the output terminal of the positive amplifier 58 and the output terminal of the negative amplifier 59 of the differential amplifier circuit 64 is a differential mode compensation voltage v comp _ difThen, the differential mode compensation voltage v comp _ dif and the differential mode voltage v HV _ dif can be expressed by the following mathematical formulas (VI) and (VIII).

[0066]

number

[0067]

number

[0068] In addition, R div1 , R div2 , is the resistance value of the voltage detection voltage divider resistors 56 and 57, C sense is the capacitance value of the voltage detection capacitors 26 and 27. G2 is the gain of the differential amplifier circuit 64, and is expressed by the formula (VII). stray _ CX is the inductance value of the parasitic inductance 66, and C X is the capacitance value of the X capacitors 41 and 42. Furthermore, I CX is the current flowing through the X capacitors 41 and 42.

[0069] From equation (VI), the differential mode voltage (HV differential mode voltage) between the positive power supply line 11 and the negative power supply line 12 is v HV _ dif If the voltage detected as is zero, the difference between the output of the positive amplifier 58 and the output of the negative amplifier 59 also disappears, and the differential mode compensation voltage v comp _ dif becomes zero, in which case it is equivalent to two X capacitors 41 and 42 connected in series.

[0070] On the other hand, when a voltage difference occurs as a differential mode voltage between the positive power supply line 11 and the negative power supply line 12, for example, when the voltage of the positive power supply line 11 rises by "1" and the voltage of the negative power supply line 12 falls by "1", the differential mode compensation voltage v comp _ dif becomes "2", the output voltage of the positive side amplifier 58 is applied to the X capacitor 42 connected to the negative side power supply line 12, and the output voltage of the negative side amplifier 59 is applied to the X capacitor 41 connected to the positive side power supply line 11, thereby acting to reduce (compensate for) the voltage difference between both power supply lines 11, 12.

[0071] From the above formula (VIII), the following formula (IX) is established.

[0072]

number

[0073] The impedance of the X capacitors 41 and 42 due to the compensation of the differential amplifier circuit 64 of the dual mode active filter compensation circuit 23 is Z CX Then, the impedance Z CX is expressed as the following formula (X).

[0074]

number

[0075] Using equations (VI) to (IX), impedance Z CX The capacitance value of the voltage detection capacitors 26 and 27 is C sense , the resistance value R of the voltage detection voltage divider resistors 56 and 57 div1 , R div2 , X, the capacitance value C of the capacitors 41 and 42 X , the inductance value L of the parasitic inductance 66 stray _ CX This is expressed as the following formula (XI).

[0076]

number

[0077] Here, in the high frequency range, the capacitance value C of the voltage detection capacitors 26 and 27 is set so that the impedance of the voltage detection capacitors 26 and 27 can be ignored compared to the impedance of the voltage detection voltage dividers 56 and 57. sense and the resistance value R of the voltage detection voltage divider resistors 56 and 57 div1 , R div2 By selecting the above, the formula (XI) can be regarded as the following formula (XII).

[0078]

number

[0079] Here, the voltage division ratio of the voltage detection voltage dividing resistors 56 and 57 is given by the following formula (XIV), so formula (XII) becomes the following formula (XIII) and further becomes formula (XV).

[0080]

number

[0081]

number

[0082] This formula (XV) is expressed as follows: X capacitors 41 and 42 (C X This means that in a configuration in which two X capacitors 41 and 42 are connected in series, the capacitance of the X capacitors 41 and 42 is equivalent to being (1+K·G2) times greater. In other words, due to compensation by the differential amplifier circuit 64 of the dual-mode active filter compensation circuit 23, the capacitance of the X capacitors 41 and 42 appears to be increased by (1+K·G2) times. Furthermore, the inductance value of the parasitic inductance 66 is equivalently reduced (1 / (1+K·G2)).

[0083] As described above, the differential mode voltage v detected by the detector 29 HV _dif The output voltage of the differential amplifier circuit 64 is converted into a differential mode compensation voltage v comp _ dif By applying the positive and negative voltages to the X capacitors 41 and 42 in reverse order, the apparent capacitance values ​​of the X capacitors 41 and 42 increase (by a factor of (1+K·G2)) in accordance with the gain G2 of the differential amplifier circuit 64.

[0084] The wide dashed line in FIG. 7 indicates the impedance characteristics of the X capacitor of a normal passive noise filter, and the solid line and the thin dashed line indicate the impedance characteristics of the X capacitor of the active filter device 1 of the present invention. CX is the impedance of the X capacitor, the solid line indicates the case where (1 + K·G2) = 2, and the fine dashed line indicates the case where (1 + K·G2) = 3. As is clear from this figure, according to the active filter device 1 of the present invention, the capacitance value of the X capacitor apparently increases, and the impedance Z CX is reduced in proportion to the gain G2 value compared to a normal passive noise filter.

[0085] By increasing the apparent capacitance of the X capacitors 41 and 42, it is possible to increase the reflux of the differential mode noise current indicated by the dashed-dotted arrow in FIG. 2, reduce the differential mode current leaking to the power supply, and reduce the differential mode noise, without using a large-capacity X capacitor or a large normal mode choke coil.

[0086] In addition, in the embodiment, the voltage detected by a single detection unit 29 consisting of a pair of voltage detection capacitors 26, 27 is input to an inverting amplifier circuit 37 and a differential amplifier circuit 64, so that the circuit configuration of the detection unit 29 can be simplified.

[0087] Furthermore, in this embodiment, the ground path 38 of the detection unit 29 and the ground path 39 of the inverting amplifier circuit 37 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 circuit 37 have on the detection of the common-mode voltage by the detection unit 29. [Example]

[0088] Next, Fig. 8 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 29C and 29D) are provided for the inverting amplifier circuit 37 and the differential amplifier circuit 64 of the dual-mode active filter compensation circuit 23, respectively.

[0089] In this case, the detection unit 29C for the inverting amplifier circuit 37 is made up of common-mode voltage detection capacitors 26C and 27C, one end of which is connected to the power supply lines 11 and 12, respectively, and the common-mode voltage detection resistor 36 (FIG. 2) connected to the other end of each capacitor, and the detection unit 29D for the differential amplifier circuit 64 is made up of differential-mode voltage detection capacitors 26D and 27D, one end of which is connected to the power supply lines 11 and 12, respectively, and the voltage detection voltage-dividing resistors 56 and 57 (FIG. 2) connected to the other end of each capacitor.

[0090] In this way, by providing the detectors 29C and 29D for the inverting amplifier circuit 37 and the differential amplifier circuit 64, respectively, there is an advantage that noise voltage detection characteristics according to the frequency characteristics of the common mode and differential mode can be obtained. [Example]

[0091] Next, Figure 9 shows the 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 path 38 of the detection unit 29 is directly connected to the housing 18 (ground potential), and the ground path 39 of the power supply circuit 34 of the amplifier 32 (ground path of the inverting amplifier circuit 37) is connected to the circuit ground 30 as described above.

[0092] As in this embodiment, by setting the housing 18 to ground potential, connecting the circuit ground 30 to the housing 18, connecting the ground path 38 of the detection unit 29 to the housing 18, and connecting the ground path 39 of the inverting amplifier circuit 37 to the circuit ground 30, it is possible to eliminate detection errors of the detection unit 29 due to fluctuations in the potential of the circuit ground 30 caused by the operating current of the inverting amplifier circuit 37.

[0093] 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 5 is not limited to this, and the present invention is effective for various home / commercial appliances that require reduction of common mode noise and differential mode noise. [Explanation of symbols]

[0094] 1. Active filter device 2 Electric compressor 3. Inverter device 7 High voltage battery (DC power supply) 8 motors 11, 12 Power lines 15 Switching element 18. Cabinet 20 Control circuit 21, 22 Y capacitor 23 Dual-mode active filter compensation circuit 26, 27, 26C, 27C, 26D, 27D Voltage detection capacitors 28 Common mode choke coil 29 Detector 30 Circuit Ground 32, 58, 59 Amplifiers (op-amps alone or op-amps with current amplifiers at the output) 33 Negative feedback resistor 36 Common mode voltage detection resistor 37 Inverting amplifier circuit 38 Grand Path 41, 42 x capacitors 43, 44 Normal mode coil 52 Common mode voltage compensation section 53 Differential mode voltage compensation section 56, 57 Voltage detection voltage divider resistor 61, 62 Feedback resistor 64 Differential Amplifier Circuit

Claims

1. a common mode choke coil inserted into a pair of positive and negative power supply lines; a normal mode choke coil connected to the pair of power supply lines or one of the pair of power supply lines; a detection unit that detects the voltage of the pair of power supply lines; an inverting amplifier circuit that inverts and amplifies the common mode voltage detected by the detector; Y capacitors connected between the output of the inverting amplifier circuit and the pair of power supply lines, respectively; a differential amplifier circuit that differentially amplifies the differential mode voltage between the pair of power supply lines detected by the detection unit; X capacitors are connected between the output of the differential amplifier circuit and the pair of power supply lines, The output voltage of the inverting amplifier circuit is applied to the Y capacitor, an output voltage obtained by amplifying the voltage on the positive power supply line of the differential amplifier circuit is applied to the X capacitor connected to the negative power supply line, and an output voltage obtained by amplifying the voltage on the negative power supply line of the differential amplifier circuit is applied to the X capacitor connected to the positive power supply line.

2. the differential amplifier circuit includes a positive amplifier, the voltage of which on the positive power supply line detected by the detection unit is input as a differential input signal to a non-inverting input terminal thereof, and a negative amplifier, the voltage of which on the negative power supply line detected by the detection unit is input as a differential input signal to a non-inverting input terminal thereof; 2. The active filter device according to claim 1, wherein the X capacitor connected to the negative power supply line is connected to the output of the positive amplifier, and the X capacitor connected to the positive power supply line is connected to the output of the negative amplifier.

3. 3. The active filter device according to claim 1, wherein a voltage detected by a single detection unit composed of a pair of voltage detection capacitors is input to the inverting amplifier circuit and the differential amplifier circuit.

4. 3. The active filter device according to claim 1, wherein the detection unit is provided for each of the inverting amplifier circuit and the differential amplifier circuit.

5. 5. 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.

6. 6. 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.

7. The housing is set to a ground potential, and a circuit ground is connected to the housing; 7. The electric compressor according to claim 6, 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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