Active filter device and this comprehensive electrically driven compressor

Abstract

An active filter device is provided that solves the problems of the so-called Π-noise filter and can achieve good noise suppression from the low-frequency range to the high-frequency range. An active filter device 1 comprises a common-mode choke 28 inserted into a pair of power supply lines 11, 12, Y-capacitors 61, 62 of the front stage of the common-mode choke 28, an active feedback compensation voltage output circuit 23 comprising a detection unit 29 that detects the common-mode voltage, and an inverting amplification circuit 37 that inverts and amplifies the common-mode voltage detected at the detection unit, and Y-capacitors 21, 22 of the rear stage between the output of the inverting amplification circuit and the common-mode choke, wherein the output voltage of the inverting amplification circuit is applied to the Y-capacitors of the rear stage as a compensation voltage.

Description

TECHNICAL AREA

[0001] The present invention relates to an active filter device for suppressing common-mode noise and an electrically driven compressor comprising this active filter device. STATE OF THE ART

[0002] A passive common-mode noise filter for reducing common-mode noise is a so-called L-noise filter, which consists of a common-mode choke inserted into a pair of power supply lines and Y-capacitors connected at a rear stage of the common-mode choke (on the output side of the common-mode choke) between the two power supply lines and a ground potential (see, for example, patent document 1).

[0003] However, the problem is that the noise reduction performance of the passive L-filter decreases in a high-frequency range at or above a resonant frequency of a capacitance component of the Y-capacitors and a parasitic inductance.

[0004] There is also a passive so-called Π noise filter, in which the Y capacitors are also connected at the front stage of the common-mode choke (on the input side of the common-mode choke) between the two power supply lines and the ground potential (see, for example, patent document 2).

[0005] Several approaches have also been disclosed in which an active filter is used as a common-mode noise filter (see, for example, patent document 3 and patent document 4). LIST OF REFERENCE DOCUMENTS PATENT DOCUMENTS Patent Document 1: JP 2008-78844 A Patent Document 2: JP 2020-516169 A Patent Document 3: JP 2011-135684 A Patent Document 4: JP 2002-204189 A BRIEF SUMMARY OF THE INVENTIONAL TASKS OF THE INVENTION

[0006] According to the passive Π noise filter, there is indeed an advantage over the passive L noise filter in that the common-mode impedance decreases in the high-frequency range at or above the resonant frequency of the Y capacitors, but the problem is that the common-mode impedance increases in the low-frequency range and the noise suppression performance decreases.

[0007] The present invention was made to solve these problems of the prior art, and its objective is to provide an active filter device that can solve the problems of the so-called Π noise filter and achieve good noise suppression from the low-frequency range to the high-frequency range, and an electrically driven compressor comprising this device. SOLUTION OF THE TASKS

[0008] An active filter device of the present invention is characterized by a common-mode choke inserted into a pair of power supply lines, front-stage Y-capacitors each connected between a circuit ground and the pair of power supply lines on the input side of the common-mode choke, an active feedback compensation voltage output circuit comprising a detection unit that detects common-mode voltage and an inverting amplification circuit that inverts the common-mode voltage detected at the detection unit, and rear-stage Y-capacitors each connected between the output of the inverting amplification circuit and the pair of power supply lines on the output side of the common-mode choke, wherein the output voltage of the inverting amplification circuit is applied to the rear-stage Y-capacitors as a compensation voltage.

[0009] An active filter device of the invention of claim 2 is characterized by a common-mode choke coil inserted into a pair of power supply lines, active feedback compensation voltage output circuits of the front stage and the rear stage, each comprising a detection unit that detects the common-mode voltage and an inverting amplification circuit that inverts the common-mode voltage detected at the detection unit, Y-capacitors of the front stage, each connected between the output of the inverting amplification circuit of the active feedback compensation voltage output circuit of the front stage and the pair of power supply lines on the input side of the common-mode choke coil, and Y-capacitors of the rear stage.which are each connected between the output of the inverting gain circuit of the active feedback compensation voltage output circuit of the rear stage and the pair of power supply lines on the output side of the common-mode choke, wherein the output voltage of the inverting gain circuit of the active feedback compensation voltage output circuit of the front stage is applied as a compensation voltage to the Y capacitors of the front stage and the output voltage of the inverting gain circuit of the active feedback compensation voltage output circuit of the rear stage is applied as a compensation voltage to the Y capacitors of the rear stage.

[0010] An electrically driven compressor of claim 3 is characterized in that the active filter device of the above inventions and an inverter device are provided in one piece in a housing body.

[0011] An electrically driven compressor of claim 4 is characterized in that the active filter device of the above invention is designed on a circuit board other than an inverter device.

[0012] An electrically driven compressor of an invention of claim 5 is characterized in that, in the above invention, the active filter device is shielded from the inverter device. EFFECTS OF THE INVENTION

[0013] According to the active filter device of the present invention, this comprises a common-mode choke inserted into a pair of power supply lines, front-stage Y-capacitors each connected between a circuit ground and the pair of power supply lines on the input side of the common-mode choke, an active feedback compensation voltage output circuit comprising a detection unit that detects common-mode voltage and an inverting amplification circuit that inverts the common-mode voltage detected at the detection unit, and rear-stage Y-capacitors each connected between the output of the inverting amplification circuit and the pair of power supply lines on the output side of the common-mode choke, wherein the output voltage of the inverting amplification circuit is applied to the rear-stage Y-capacitors as a compensation voltage.This explains why, by designing a so-called Π-noise filter compared to an L-noise filter, the common-mode impedance in the high-frequency range decreases to or above the resonant frequency of the Y-capacitors.

[0014] Due to the design as a Π-noise filter, without further measures compared to the L-noise filter, there is an increase in the common-mode impedance in the low-frequency range below the resonant frequency of the Y-capacitors, but since in the present invention the output voltage of the inverting amplification circuit of the active feedback compensation voltage output circuit is applied as a compensation voltage to the Y-capacitors of the rear stage, the apparent capacitance value of the Y-capacitors of the rear stage increases according to the gain of the inverting amplifier circuit.

[0015] This increase in the apparent capacitance of the rear-stage Y-capacitors makes it possible to lower the common-mode impedance, increase noise current feedback, and reduce common-mode current leakage to the power supply side without using large-capacitance Y-capacitors and a large common-mode choke. In this way, common-mode noise can be reduced across the entire measured frequency range.

[0016] Since applying this to a typical passive Π-noise filter with common-mode choke and Y-capacitors of the front and rear stages improves the suppression performance for differential-mode noise, it offers high universal applicability.

[0017] If the output voltage of the inverting amplification circuit of the active feedback compensation voltage output circuit is applied only to the Y capacitors of the front stage, but not to the Y capacitors of the rear stage as a compensation voltage, the common-mode impedance is further reduced in the high-frequency range, but the common-mode impedance ultimately increases in the low-frequency range.

[0018] Since, according to the active filter device of claim 2, in addition to the invention of claim 1, the output voltage of the inverting amplification circuit of the active feedback compensation voltage output circuit of the front stage is also applied as a compensation voltage to the Y capacitors of the front stage, the common-mode impedance can be further reduced over the entire measured frequency range and differential-mode noise can be reduced even more effectively.

[0019] The active filter device of the above inventions is extremely advantageous when, as in the invention of claim 3, it is provided in one piece in a housing of an electrically driven compressor together with an inverter device.

[0020] In this case, by designing the active filter device on a different circuit board than the inverter device, as in the invention of claim 4, the filter characteristics can be easily changed as desired according to the specifications.

[0021] Furthermore, by shielding the active filter device from the inverter device as in claim 5 of the invention, the influence of the noise source (inverter device) can be limited and the noise suppression effect can be achieved as intended. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is an electrical circuit diagram of an electrically driven compressor of an embodiment to which the active filter device of the present invention has been applied, and of a power supply path to the electrically driven compressor. Fig. Figure 2 is an electrical circuit diagram of the electrically driven compressor. Fig. 1 (Example 1). Fig. Figure 3 is a schematic sectional view of a part of the electrically driven compressor made of Fig. 1 with an inverter mounting section. Fig. Figure 4 is an equivalent circuit diagram of an active filter device made of Fig. 2. Fig. Figure 5 is an explanatory view of the change in common-mode impedance due to the filter configuration. Fig. Figure 6 is an explanatory view of the change in common-mode impedance due to the capacitance ratio of the Y capacitors of the front and rear stages of the active filter device. Fig. 1. Fig. Figure 7 is an electrical circuit diagram of an electrically driven compressor to which the active filter device of a further embodiment of the present invention has been applied, and of a power supply path to the electrically driven compressor (embodiment 2). Fig. Figure 8 is an explanatory view of the change in common-mode impedance due to the filter configuration, which Fig. 7 includes. DESCRIPTION OF THE EXECUTION FORMS

[0022] An embodiment of the present invention is described in detail below, based on the accompanying figures. Example 1

[0023] Fig. Figure 1 is an electrical circuit diagram of an electrically driven compressor 2 of an embodiment to which an active filter device 1 of the present invention has been applied, and of a power supply path to the electrically driven compressor 2. Fig. 2 is an electrical circuit diagram of the electrically driven compressor 2 and Fig. Figure 3 is a schematic sectional view of a part of the electrically driven compressor 2 with an inverter mounting section 4 in which an inverter device 3 is mounted.

[0024] The electrically driven compressor 2 of the exemplary embodiment forms, for example, part of a refrigerant circuit of a vehicle air conditioning system installed in a vehicle such as an electric vehicle, hybrid vehicle, or the like, and which air-conditions a passenger compartment, wherein an inverter device (PWM inverter) 3 and the active filter device 1 of the present invention are integrally provided with the electrically driven compressor 2. Thus, the electrically driven compressor 2 of the exemplary embodiment is an electrically driven compressor of the inverter type.

[0025] The inverter device 3 converts direct current from a high-voltage battery 7 (HV, for example 350 V DC) installed as a direct current supply in the vehicle into alternating current of any frequency and applies it to a motor 8 of the electrically driven compressor 2 to operate it, wherein the active filter device 1 of the present invention is provided to reduce common-mode noise generated at the inverter device 3. (1) Power supply path of the electrically driven compressor 2

[0026] In Fig. 1 is the inverter device 3 by several switching elements (IGBT, Fig. 3) 15 formed, which are connected to a positive-side power supply line 11 and a negative-side power supply line 12 of the high-voltage battery 7. Reference numeral 20 in Fig. Reference numeral 1 denotes a control circuit, and the switching of the switching elements 15 of the inverter device 3 is controlled by this control circuit 20 (PWM control). Reference numeral 13 denotes a smoothing capacitor connected between the two power supply lines 11 and 12.

[0027] Reference numeral 14 denotes an ECU of the vehicle and 16 a low-voltage battery (12 V DC), wherein the control circuit 20, based on a command from the ECU 14, controls the switching of the switching elements 15 of the inverter device 3 with the low-voltage battery 16 as the power supply.

[0028] Reference numeral 18 designates a housing (manufactured by aluminum die-casting) of the electrically driven compressor 2. Furthermore, the electrically driven compressor 2 is connected to the high-voltage battery 7 by a shielded high-voltage cable harness 25 (which forms the two power supply lines 11, 12), and the housing 18 of the electrically driven compressor 2 is fixed directly to the vehicle body. In this way, the housing 18 serves as the ground potential and the circuit ground.

[0029] The active filter device 1 of the exemplary embodiment consists of a common-mode choke coil (CMCC) 28, which is inserted into the pair of power supply lines 11, 12, Y-capacitors 61, 62 of the front stage (C Y1), which are each connected between the housing body 18 (circuit ground) and the pair of power supply lines 11, 12 on the input side (side of the high-voltage battery 7) of the common-mode choke coil 28, Y-capacitors 21, 22 of the rear stage (C Y2 ), which are each connected between the output of an active feedback compensation voltage output circuit 23 and the pair of power supply lines 11, 12 on the output side (side of the inverter device 3) of the common-mode choke coil 28, and the active feedback compensation voltage output circuit 23, which is connected between the Y capacitors 21, 22 of the rear stage and the chassis 18 (ground potential, circuit ground). The active feedback compensation voltage output circuit 23 has common-mode voltage detection capacitors 26, 27 (C sense, forming the detection unit 29 of the present invention) which are each connected between the pair of power supply lines 11, 12.

[0030] Since the active filter device 1 has, as described above, the common-mode choke coil 28, the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage, the form of application of the active feedback compensation voltage output circuit 23 results in a so-called Π noise filter configuration. (2) Electrical circuit of the electrically driven compressor 2

[0031] Fig. Figure 2 shows exclusively the electrical circuit of the electrically driven compressor 2. The reference symbols are the same as in... Fig. The elements marked with 1 are identical. Although insulating paper, refrigerant, and oil are present between a winding 8C of the motor 8 and the housing body 18, reference numeral 31 in Fig. 2 between the winding 8C of the motor 8 and the housing 18 is designated as a stray capacitance. Noise current flows through this stray capacitance 31, thereby generating common-mode noise.

[0032] In Fig. Figure 2 shows the 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 exemplary embodiment comprises an amplifier 32 and a negative feedback resistor (R) connected between the inverting input terminal (-) and the output terminal of the amplifier 32. f ) 33, a power supply circuit (V) connected between the positive supply terminal and the negative supply terminal of the amplifier 32 CC , V EE ) 34, the common-mode voltage detection capacitors 26, 27 and a common-mode voltage detection resistor (R sense) 36, which together with the common-mode voltage detection capacitors 26, 27 forms the detection unit 29. The detection unit 29 is therefore also included in the active feedback compensation voltage output circuit 23.

[0033] The inverting amplifier circuit 37 (gain G1) of the present invention is formed by the amplifier 32, the feedback resistor 33, and the common-mode voltage detection resistor 36. One end of the common-mode voltage detection capacitors 26, 27 is each connected to the pair of power supply lines 11, 12 on the output side of the common-mode choke 28, and the other end of the common-mode voltage detection capacitors 26, 27 is 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 a ground path 38 with the housing 18 (ground potential), which is the circuit ground. The ground path 38 is the ground path of the detection unit 29.

[0034] One end of the Y-capacitors 21, 22 of the rear stage discussed above is each connected to the pair of power supply lines 11, 12 on the output side of the common-mode choke 28. The other ends of the Y-capacitors 21, 22 of the rear stage are connected together to the output terminal (output of the inverting amplifier circuit 37) of the amplifier 32. In this embodiment, a ground path 39 of the power supply circuit 34 of the amplifier 32 is connected via ground path 38 to the chassis 18 (ground potential), which is the circuit ground. Ground path 39 is the ground path of the inverting amplifier circuit 37.

[0035] In this way, a form is obtained in which the Y-capacitors 21, 22 are each connected via the amplifier 32 of the active feedback compensation voltage output circuit 23 between the pair of power supply lines 11, 12 on the output side of the common-mode choke coil 28 and the chassis 18 (ground potential), which is the circuit ground, so that the output voltage of the inverting amplification circuit 37 (of the amplifier 32) is applied as a compensation voltage to the Y-capacitors 21, 22 of the rear stage. (3) Structure of the electrically driven compressor 2 (inverter mounting section 4)

[0036] Fig. Figure 3 is a schematic sectional view of the electrically driven compressor 2. The one in Fig. The housing body 18 shown, manufactured by aluminum die-casting, houses the motor 8 and a compression mechanism driven by the motor 8. A high-voltage circuit 41 of the inverter device 3, the smoothing capacitor 13 and the like ( Fig. 3) and a low-voltage circuit 42 of the control circuit 20 and the like ( Fig. 3) are, as in Fig. 3 shown, provided on a control board 43.

[0037] In contrast, the active filter device 1, consisting of the active feedback compensation voltage output circuit 23, the Y capacitors 61, 62 of the front stage, the Y capacitors 21, 22 of the rear stage and the common-mode choke 28 discussed above, is provided on an HV filter board 44 separately from the control board 43.

[0038] The control board 43 and the HV filter board 44 are, as in Fig. 3 shown, arranged in an inverter receiving section 4, which is formed on an end section of the housing body 18 of the electrically driven compressor 2. In the inverter receiving section 4, a first receiving chamber 4A and a second receiving chamber 4B are separated by a partition 46 formed on the housing body 18, with the control board 43 being provided in the first receiving chamber 4A and the HV filter board 44 being provided in the second receiving chamber 4B ( Fig. 3) This results in a shape for the active filter device 1 in which the high-voltage circuit 41, which includes the inverter device 3 and the like, is shielded from the low-voltage circuit 42, which includes the control circuit 20 and the like.

[0039] Reference numeral 47 in Fig. Reference numeral 3 designates an HV connector for connecting the high-voltage battery 7 and the active filter device 1. Reference numeral 48 designates a busbar for wiring the inverter device 3, the control circuit 20, and the active filter device 1 with a structure made of molded hard plastic. The switching elements 15 (IGBT = Insulated-Gate Bipolar Transistor) discussed above are arranged to dissipate heat to the housing 18 and are connected to the inverter device 3 (high-voltage circuit 41) via the busbar 48. (4) Mode of operation of the active filter device 1

[0040] With reference to Fig. Sections 2 to 4 now describe the operating mode of the active filter device 1 of the exemplary embodiment. The same reference numerals are used as in Fig. 1 and Fig. 3 provided elements in Fig. Four of them are identical. Fig. Figure 4 shows an equivalent circuit diagram of the active filter device 1. In an actual circuit, the Y capacitors 61, 62 of the front stage exhibit a parasitic inductance 63 (L straycy1 ) and the Y-capacitors 21, 22 of the rear stage a parasitic inductance 51 (L straycy2 ) on ( Fig. 4).

[0041] If the common-mode voltage (HV common-mode voltage) occurring on the power supply lines 11, 12 is equal to v HVcom and the compensation voltage of the inverting amplifier circuit 37 with v compcom As shown, the input terminal of the inverting amplifier circuit 37, to which the common-mode voltage detection resistor 36 is connected, is a virtual ground, which is why the common-mode voltage (HV common-mode voltage) v HVcom can be represented by the following formula (I). Where R sense the resistance value of the common-mode voltage detection resistor 36 and Csense the capacitance value of the common-mode voltage detection capacitors 26, 27, while C sense (×2) denotes the combined capacitance of the two capacitors. G1 is the gain of the inverting amplifier circuit 37, where G1 = R f / R sense . R f The resistance value of the negative feedback resistor is 33.

[0042] L straycy2 is the inductance value of the parasitic inductance 51, where L straycy2 (× 1 / 2) denotes the composite inductance value. C Y2 is the capacitance value of the Y capacitors 21, 22 of the rear stage, where C Y2 (×2) denotes the combined capacity value of the two. I Cy2 This in turn is the current flowing in the Y-capacitors 21, 22 of the rear stage.

[0043] In Fig. 4 is L straycy1 the inductance value of the parasitic inductance 63, where L straycy1 (×1 / 2) denotes the composite inductance value. CY1 is the capacitance value of the Y capacitors 61, 62 of the front stage, where C Y1 (×2) denotes the combined capacity value of the two. I Cy1 is the current flowing in the Y capacitors 61, 62 of the front stage. [Expression 1] vHVcom=(1jωCY2(×2)+jωLstraycy2(×1 / 2))⋅Icy2−G1⋅(vHVcom⋅RsenseRsense+1 / jωCsense(×2))

[0044] Formula (I) yields the following formula (II). [Expression 2] vHVcom=(Rsense+1 / jωCsense(×2))⋅(1 / jωCY2(×2)+jωLstraycy2(×1 / 2))(1+G1)⋅Rsense+1 / jωCsense(×2)⋅ICy2

[0045] If the impedance of the Y capacitors 21, 22 of the rear stage is due to the compensation by the active feedback compensation voltage output circuit 23 Z Cy2 If so, then the impedance Z Cy2 given by the following formula (III). [Expression 3] ZCy2=vHVcomICy2

[0046] If the impedance Z Cy2 using formulas (I) to (III) through the composite capacity value C sense (×2) of the common-mode voltage detection capacitors 26, 27, the resistance value R sense of the common-mode voltage detection resistor 36, the composite capacitance value C Y2 (×2) of the Y capacitors 21, 22 of the rear stage and the inductance value L straycy2 The parasitic inductance 51 is represented, resulting in the following formula (IV). [Expression 4] Zcy2=Rsense+1 / jωCsense(×2)(1+G1)⋅Rsense+1 / jωCsense(×2)⋅(1jωCY2(×2)+jωLstraycy2(×1 / 2))

[0047] By the capacity value C sense the common-mode voltage detection capacitors 26, 27 and the resistance value R senseIf the common-mode voltage detection resistor 36 is selected such that in the high-frequency range the impedance of the common-mode voltage detection capacitors 26, 27 can be ignored with respect to the impedance of the common-mode voltage detection resistor 36, formula (IV) can be interpreted as the following formula (V). [Expression 5] Zcy2=11+G1⋅(1jωCY2(×2)+jωLstraycy2(×1 / 2))

[0048] This formula (V) states that it corresponds to connecting (1+G1)-fold Y-capacitors. Thus, by compensating the active feedback compensation voltage output circuit 23, the capacitance value of the Y-capacitors 21, 22 of the rear stage appears to increase by a factor of (1+G1). The inductance value of the parasitic inductance 51 is reduced equivalently (1 / (1+G1)).

[0049] As described above, the inverting amplifier circuit 37 is provided, which amplifies the common-mode voltage v detected by the detection unit 29. HVcom inverting amplification, and the output voltage of the inverting amplifier circuit 37 as common-mode compensation voltage v compcom When a voltage is applied to the Y-capacitors 21, 22 of the rear stage, the apparent capacitance value of the Y-capacitors 21, 22 of the rear stage is increased according to the gain G1 of the inverting amplifier circuit 37 (by a factor of (1+G1)).

[0050] The frequency response of the common-mode impedance Z com the active filter device 1 is in Fig. 5 is indicated by a bold dotted line (Π active (rear)). The common-mode impedance Z com The active filter device 1 is a ratio of the sum of the current I flowing in the Y capacitors 61, 62 of the front stage. Cy1and current I flowing in the Y capacitors 21, 22 of the rear stage Cy2 to the common-mode voltage v HVcomIN , which occurs after the active filter device 1, and is defined by the following formula (VI). [Expression 6] Zcom=VHVcomIN / (ICy1+ICy2)

[0051] For comparison purposes, in Fig. Figure 5 shows the case of the passive L-noise filter (L passive) discussed above with a thin solid line and the case of the passive Π-noise filter (Π passive) with a thin dotted line. For all designs, the capacitance value of the sum of the Y-capacitors is 9.2 nF, whereby for Π-noise filters including the active filter device 1 of the exemplary embodiment, the capacitance value of the Y-capacitors of the front stage and the rear stage of the common-mode choke coil is set at 4.6 nF (composite capacitance value, hereinafter also referred to as such).

[0052] A comparison of the Π noise filters (bold dotted line and thin dotted line) and the passive L noise filter (thin solid line) from Fig. 5 shows that the common-mode impedance Z com in the Π noise filters (bold dotted line and thin dotted line) the effect of the Y capacitors of the front stage (in the embodiment of the present invention with the bold dotted line of the Y capacitors 61 and 62) in the high frequency range at or above the resonance frequency is reduced compared to the passive L noise filter (thin solid line).

[0053] However, in the passive Π noise filter (thin dotted line), the common-mode impedance is increased in the low-frequency range compared to the passive L noise filter (thin solid line).

[0054] In contrast, in the active filter device 1 of the present invention, as discussed above, the apparent capacitance value of the Y capacitors 21, 22 of the rear stage is increased (by a factor of (1+G1)), while the impedance Z Cy2 compared to the usual passive Π-noise filter, the gain is reduced according to the gain value G1. This increase in the apparent capacitance of the Y capacitors 21, 22 of the rear stage reduces the common-mode impedance Z. com the active filter device 1 also in the low frequency range, as in Fig. 5 shown by the bold dotted line, reduced compared to the passive L-noise filter (thin solid line) ( Fig. 5).

[0055] Fig. Figure 6 shows the frequency response of the common-mode impedance Z. comwith a changed capacitance value of the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage of the active filter device 1. In this case too, the thin solid line indicates the passive L-noise filter (L-passive).The thin dotted line indicates the case where the combined capacitance of the Y capacitors 61, 62, 21, 22 of the front and rear stages is the same for both stages, namely 4.6 nF; the thick solid line indicates that the combined capacitance of the Y capacitors 61, 62 of the front stage is 8.2 nF (large) and the combined capacitance of the Y capacitors 21, 22 of the rear stage is 1 nF (small); and the thick dotted line indicates that the combined capacitance of the Y capacitors 61, 62 of the front stage is 1 nF (small) and the combined capacitance of the Y capacitors 21, 22 of the rear stage is 8.2 nF (large).

[0056] As can be clearly seen from the diagram, in the case of the active filter device 1, changing the capacitance value of the Y capacitors 61, 62, 21, 22 of the front stage and the rear stage changes the frequency response of the common-mode impedance Z. com In the case of the bold solid line, for example (the combined capacitance of the Y capacitors 61, 62 of the front stage is 8.2 nF (is large) and the combined capacitance of the Y capacitors 21, 22 of the rear stage is 1 nF (is small)), there exists in the high-frequency range a point where the common-mode impedance Z com is lower than in the case of the thin dotted line (the combined capacitance value of the Y capacitors 61, 62, 21, 22 of the front stage and the rear stage is 4.6 nF for both the front and rear stages), but conversely, it tends to be higher in the low frequency range than in the other approaches.

[0057] In the case of the bold dotted line (the combined capacitance of the Y capacitors 61, 62 of the front stage is 1 nF (is small) and the combined capacitance of the Y capacitors 21, 22 of the rear stage is 8.2 nF (is large)), there is also a point in the higher frequency range and in the lower frequency range where the common-mode impedance Z com is lower than in the case of the thin dotted line (the combined capacitance value of the Y capacitors 61, 62, 21, 22 of the front stage and the rear stage is 4.6 nF for both the front and rear stages), but it tends to be higher in the mid-frequency range, which includes the resonance point.

[0058] The capacitance value of the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage of the active filter device 1 can thus be selected according to the device used, i.e. the frequency of the common-mode noise to be reduced.

[0059] According to the active filter device 1 of the present invention, as described above, the common-mode impedance Z decreases due to its design as a so-called Π-noise filter. com at or above the resonant frequency of the Y capacitors in the high-frequency range. In contrast, the common-mode impedance Z increases. comDue to its design as a Π-noise filter, the noise level in the low-frequency range extends beyond the resonance frequency without further measures. However, since in the present invention the output voltage of the inverting amplification circuit 37 of the active feedback compensation voltage output circuit 23 is applied as a compensation voltage to the Y-capacitors 21, 22 of the rear stage, the apparent capacitance value of the Y-capacitors 21, 22 of the rear stage increases according to the amplification of the inverting amplification circuit 37.

[0060] This increase in the apparent capacitance value of the Y capacitors 21, 22 of the rear stage makes it possible to reduce the common-mode impedance Z without using large-capacitance Y capacitors and a large common-mode choke. comto lower the noise current, increase the regenerative braking of noise current, and reduce the flow of common-mode current to the power supply side. In this way, common-mode noise can be reduced across the entire measured frequency range.

[0061] Since the suppression performance for differential-mode noise can be improved by applying it to a conventional passive Π-noise filter with common-mode choke 28 and Y-capacitors 61, 62, 21, 22 of the front stage and the rear stage, a high universal applicability results.

[0062] The active filter device 1 of the present invention is extremely advantageous when, as in the exemplary embodiment, it is provided integrally in the housing 18 of the electrically driven compressor 2 together with an inverter device 3. Since, in this case, the active filter device 1 is formed on the HV filter board 44 and not on the control board 43 on which the inverter device 3 is provided, the filter characteristics can be easily changed as desired according to the specifications.

[0063] Furthermore, since in the exemplary embodiment the HV filter board 44 (active filter device 1) is shielded from the control board 43, on which the inverter device 3 is provided, by the partition 46, the influence of the noise source (inverter device 3) can be limited and the noise suppression effect can be achieved as intended. Example 2

[0064] Next, with reference to Fig. 7 and Fig. 8 describes an active filter device 1 according to a further embodiment of the present invention. Using the same reference numerals as in Fig. The elements designated 1 to 6 in these figures have the same or a similar mode of operation. In addition to the configuration of the embodiment described above (Embodiment 1), the active filter device 1 of this embodiment includes a further active feedback compensation voltage output circuit 23A.

[0065] In this embodiment, the active feedback compensation voltage output circuit 23 of the embodiment described above is the active feedback compensation voltage output circuit of the rear stage of the present invention, while the active feedback compensation voltage output circuit 23A added in this embodiment is the active feedback compensation voltage output circuit of the front stage of the present invention. The active feedback compensation voltage output circuit 23A of the front stage has the same configuration as the active feedback compensation voltage output circuit 23 of the rear stage discussed above.

[0066] In this embodiment, the Y capacitors 61, 62 of the front stage (C Y1) each between the pair of power supply lines 11, 12 on the input side of the common-mode choke coil 28 and the output of the active feedback compensation voltage output circuit 23A of the front stage.

[0067] In this case, too, a form results in which the Y-capacitors of the front stage 61, 62 are connected via the amplifier 32 of the active feedback compensation voltage output circuit 23A of the front stage between the pair of power supply lines 11, 12 and the housing body 18 (ground potential), which is the circuit ground, wherein the design is such that the output voltage of the inverting amplification circuit 37 (of the amplifier 32) of the active feedback compensation voltage output circuit 23A of the front stage is applied as compensation voltage to the Y-capacitors 61, 62 of the front stage.

[0068] The effect of the active feedback compensation voltage output circuit 23A of the front stage on the Y capacitors 61, 62 of the front stage is the same as the effect of the active feedback compensation voltage output circuit 23 of the rear stage on the Y capacitors 21, 22 of the rear stage discussed above, which is why its detailed description is omitted, and in this embodiment as well, the apparent capacitance value of the Y capacitors 61, 62 of the front stage increases due to the active feedback compensation voltage output circuit 23A of the front stage.

[0069] Fig. Figure 8 shows the frequency response of the common-mode impedance Z comfor the case that, as in embodiment 1, the active feedback compensation voltage output circuit 23 of the rear stage is connected only to the Y capacitors 21, 22 of the rear stage, the case that the active feedback compensation voltage output circuit 23A of the front stage is connected only to the Y capacitors 61, 62 of the front stage, and the case that, as in embodiment 2, the active feedback compensation voltage output circuit 23A of the front stage and the active feedback compensation voltage output circuit 23 of the rear stage are each connected to the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage.

[0070] In this case as well, the thin solid line indicates the passive L-noise filter (L passive). The thin dotted line indicates the passive Π-noise filter (Π passive).The thick dotted line indicates the case where, as in embodiment 1, the active feedback compensation voltage output circuit 23 of the rear stage is connected only to the Y capacitors 21, 22 of the rear stage (Π active (rear)), the line with a dot indicates the case where the active feedback compensation voltage output circuit 23A of the front stage is connected only to the Y capacitors 61, 62 of the front stage (Π active (front)), and the thick solid line indicates the case where, as in embodiment 2, the active feedback compensation voltage output circuit 23A of the front stage and the active feedback compensation voltage output circuit 23 of the rear stage are each connected to the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage, respectively (Π active (both)).In this case too, the total capacitance value of the Y capacitors is the same at 9.2 nF, and in the case of the Π design, the combined capacitance value for the Y capacitors of the front stage and the rear stage is also the same at 4.6 nF each.

[0071] As can be clearly seen from the view, the common-mode impedance Z com in the event that the active feedback compensation voltage output circuit 23A of the front stage is only connected to the Y capacitors 61, 62 of the front stage (with a dot dashed line in Fig. 8) higher in the lower frequency range than with the passive L-noise filter (thin solid line in Fig. 8) and the passive Π noise filter (thin dotted line in Fig. 8).

[0072] If, on the other hand, as in embodiment 2, the active feedback compensation voltage output circuit 23A of the front stage and the active feedback compensation voltage output circuit 23 of the rear stage are each connected to the Y capacitors 61, 62 of the front stage and the Y capacitors 21, 22 of the rear stage (bold solid line in Fig. 8), shows that in the lower frequency range the common-mode impedance Z com compared to embodiment 1 (bold dotted line in Fig. 8) can be further reduced and common-mode noise further reduced.

[0073] Therefore, if, as in this embodiment, in addition to the output voltage of the inverting gain circuit 37 of the active feedback compensation voltage output circuit 23 of the rear stage being applied as a compensation voltage to the Y capacitors 21, 22 of the rear stage, the output voltage of the inverting gain circuit 37 of the active feedback compensation voltage output circuit 23A of the front stage being applied as a compensation voltage to the Y capacitors 61, 62 of the front stage, the common-mode impedance Z can be reduced across the entire measured frequency range. com further reduced and differential noise even more effectively reduced.

[0074] In the exemplary embodiments, the active filter device 1 of the present invention is applied to the electrically driven compressor 2, which forms a refrigerant circuit of a vehicle air conditioning device, but the inventions of claims 1 and 2 are not limited thereto, and the invention is also useful for various household / commercial appliances where there is a need to reduce common-mode noise. LIST OF REFERENCE MARKS 1 active filter device 2 electrically driven compressors 3 Inverter device 4 Inverter mounting section 7 High-voltage battery (DC power supply) 8 engine 11, 12 Power supply line 15 switching element 18 Housing body (circuit ground) 20 Control circuit 21, 22 Y-capacitor of the rear stage 23 Active feedback compensation voltage output circuit (active feedback compensation voltage output circuit of the rear stage) 23A Active feedback compensation voltage output circuit of the front stage 26, 27 Common-mode voltage detection capacitor 28 Common-mode choke coil 29 recording units 32 amplifiers 36 Common-mode voltage detection resistor 37 inverting amplification circuit 38, 39 Mass path 43 Control board 44 HV filter board 46 Partition wall 61, 62 Y -front stage capacitor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2008-78844 A

[0005] JP 2020-516169 A

[0005] JP 2011-135684 A

[0005] JP 2002-204189 A

[0005]

Claims

[1] Active filter device, characterized by : a common-mode choke coil inserted into a pair of power supply lines, Front-stage Y-capacitors, each connected between a circuit ground and the pair of power supply lines on the input side of the common-mode choke, an active feedback compensation voltage output circuit comprising a detection unit that detects common-mode voltage and an inverting amplification circuit that inverts the common-mode voltage detected at the detection unit, and Y-capacitors of the rear stage, each connected between the output of the inverting amplification circuit and the pair of power supply lines on the output side of the common-mode choke, where the output voltage of the inverting amplification circuit is applied as a compensation voltage to the Y capacitors of the rear stage. [2] Active filter device, characterized by : a common-mode choke inserted into a pair of power supply lines, active feedback compensation voltage output circuits of the front stage and the rear stage, each comprising a detection unit that detects common-mode voltage and an inverting amplification circuit that inverts the common-mode voltage detected at the detection unit, Y-capacitors of the front stage, each connected between the output of the inverting gain circuit of the active feedback compensation voltage output circuit of the front stage and the pair of power supply lines on the input side of the common-mode choke, and Y-capacitors of the rear stage, each connected between the output of the inverting gain circuit of the active feedback compensation voltage output circuit of the rear stage and the pair of power supply lines on the output side of the common-mode choke, wherein the output voltage of the inverting gain circuit of the active feedback compensation voltage output circuit of the front stage is applied as compensation voltage to the Y capacitors of the front stage and the output voltage of the inverting gain circuit of the active feedback compensation voltage output circuit of the rear stage is applied as compensation voltage to the Y capacitors of the rear stage. [3] Electrically driven compressor, characterized by that the active filter device according to claim 1 or 2 and an inverter device are provided integrally with a housing body. [4] Electrically driven compressor according to claim 3, characterized by that the active filter device is mounted on a different circuit board than the inverter device. [5] Electrically driven compressor according to claim 4, characterized by that the active filter device is shielded from the inverter device.

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