A CM-DM integrated active EMI filter with adjustable common-differential mode attenuation

Abstract

The application belongs to the technical field of power electronics, and relates to a CM-DM integrated active EMI filter with adjustable common-mode and differential-mode attenuation, comprising: a first noise attenuation circuit and a second noise attenuation circuit; the first noise attenuation circuit and the second noise attenuation circuit are both composed of a detection link, an amplification link and an injection link; the application takes a negative bus as a reference, two operational amplifiers use the same power supply system, and common-mode and differential-mode noises can be simultaneously and effectively attenuated through constructing a proper compensation current path, and common-mode and differential-mode insertion losses can be respectively changed by changing the gains of the first and second noise attenuation circuits; therefore, the application realizes the separate adjustment of common-mode and differential-mode noise attenuation capabilities.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology and relates to a CM-DM integrated active EMI filter with adjustable common-differential mode attenuation. Background Technology

[0002] With the widespread application of electronic devices and the continuous increase in operating frequencies, electromagnetic interference (EMI) has become an increasingly serious problem. The prevalence of high-frequency switching circuits and the miniaturization trend of electronic components have significantly increased the intensity and complexity of EMI. This interference not only affects the normal operation of equipment but can also cause serious interference to surrounding equipment and systems. Especially in grid-connected applications, excessive EMI can even threaten the stability and security of the power grid. How to effectively suppress EMI has become a key technical challenge that the electronics industry urgently needs to solve.

[0003] In addressing EMI issues, EMI filters have garnered significant attention as a crucial suppression method. Traditional passive EMI filters are widely used due to their simple structure and high stability; however, their large size and limited ability to suppress low-frequency interference make them unsuitable for the miniaturization and high-performance requirements of modern electronic devices. In contrast, active EMI filters, with their superior low-frequency suppression, smaller size, and adjustable performance, have gradually become a research and application hotspot. With advancements in control algorithms and power device technology, active EMI filters are demonstrating higher integration and broader application prospects while improving filtering performance, making them a vital solution to the increasingly severe EMI problems.

[0004] An active EMI filter (AEF) mainly consists of three parts: noise detection, noise amplification, and noise compensation. The noise detection section has two methods: current sensing and voltage sampling. Similarly, the noise compensation section, like current sampling, also has two methods: current compensation and voltage compensation. Therefore, based on the differences in the detection and compensation sections, active EMI filters can be classified into current-sensing current-compensating (CSCC), current-sensing voltage-compensating (CSVC), voltage-sensing current-compensating (VSCC), and voltage-sensing voltage-compensating (VSVC). Since current sensing requires a current transformer and voltage compensation requires a transformer, both of which require a larger size, using a voltage-sensing current-compensating active EMI filter allows for a smaller size.

[0005] Active EMI filters are further divided into common-mode AEF and differential-mode AEF based on the type of noise attenuation. Their working principles and design methods are basically similar, but the specific compensation paths differ. In traditional AEF topologies, the common-mode AEF primarily uses ground (GND) as a reference, while the differential-mode AEF primarily uses the negative bus as a reference. Because the reference settings for common-mode and differential-mode AEFs are different, two power supply systems are required if the circuit contains both common-mode and differential-mode AEFs. This significantly increases the size of the AEF system. The existing integrated AEF circuits work by detecting noise on the positive / negative buses and injecting it back to the positive / negative buses. This topology uses ground (GND) as a reference and cannot adjust the attenuation effect of common-mode and differential-mode noise separately.

[0006] However, there is currently no integrated AEF circuit that can effectively attenuate both common-mode and differential-mode noise while using the same power supply system, and the attenuation effect of common-mode and differential-mode noise can be adjusted separately.

[0007] Therefore, a method or apparatus that can simultaneously attenuate and adjust both common-mode noise and differential-mode noise is needed to solve the above-mentioned technical problems. Summary of the Invention

[0008] The technical solution adopted by the present invention to solve the technical problem is: a common-differential mode attenuation adjustable CM-DM integrated active EMI filter, the integrated active EMI filter takes the negative bus as a reference, the two operational amplifiers use the same power supply system, and the attenuation effect of common-differential mode noise can be adjusted separately;

[0009] The integrated active EMI filter includes a first noise attenuation circuit and a second noise attenuation circuit; both the first noise attenuation circuit and the second noise attenuation circuit consist of a detection stage, an amplification stage, and an injection stage.

[0010] The first noise attenuation circuit includes: a first detection resistor, a first operational amplifier, a first amplification resistor, a first integrating capacitor, and a first injection resistor. The electrical connections of the first noise attenuation circuit include: one end of the first detection resistor is connected to ground, the other end of the first detection resistor is connected to the inverting input of the first operational amplifier, the non-inverting input of the first operational amplifier is connected to the negative bus between the LISN and EUT, the output of the first operational amplifier is connected to the first injection resistor, and the other end of the first injection resistor is connected to ground; one end of the first amplification resistor and the first integrating capacitor connected in parallel is connected to the inverting input of the first operational amplifier, and the other end of the first amplification resistor and the first integrating capacitor connected in parallel is connected to the output of the first operational amplifier; the reference ground between the positive and negative terminals of the first operational amplifier power supply system is connected to the negative bus between the LISN and EUT.

[0011] The second noise attenuation circuit includes: a detection capacitor, an injection capacitor, a second detection resistor, a second operational amplifier, a second amplification resistor, a second integrating capacitor, and a second injection resistor. The electrical connections of the second noise attenuation circuit are as follows: one end of the detection capacitor is connected to the positive bus between the LISN and EUT; the other end of the detection capacitor is connected to the second detection resistor; the other end of the second detection resistor is connected to the inverting input of the second operational amplifier; the non-inverting input of the second operational amplifier is connected to the negative bus between the LISN and EUT; the output of the second operational amplifier is connected to the second injection resistor; the other end of the second injection resistor is connected to the injection capacitor; and the other end of the injection capacitor is connected to the positive bus between the LISN and EUT. The second amplification resistor and the second integrating capacitor are connected in parallel, with one end connected to the inverting input of the second operational amplifier and the other end connected to the output of the second operational amplifier. The reference ground between the positive and negative terminals of the second operational amplifier's power supply system is connected to the negative bus between the LISN and EUT.

[0012] Preferably, in the second noise attenuation circuit, the compensation current generated by the second attenuation circuit is:

[0013] (1)

[0014] In equation (1), I p Z represents the current flowing through LISN. s-LISN This represents the series impedance of the two branches of the linear impedance stabilization network that needs to be added between the power supply and the circuit being tested during EMI testing. (V) out2 and Z out2 Z represents the output voltage and output impedance of the operational amplifier in the second noise attenuation circuit, respectively. inj2 This represents the impedance of the injection stage in the second noise attenuation circuit.

[0015] The differential-mode noise current after LISN is:

[0016] (2)

[0017] The insertion loss of the differential mode noise is:

[0018] (3)

[0019] In equations (2) and (3), Z DM I DM G represents the equivalent differential-mode noise source based on Norton's principle. s2 This represents the total gain of the second noise attenuation circuit system.

[0020] More preferably, in the first noise attenuation circuit, the compensation current generated by the first attenuation circuit is:

[0021] (4)

[0022] In equation (4), I q Z represents the negative bus current flowing through LISN. N-LISN This represents the impedance of one branch of the linear impedance stabilization network that needs to be added between the power supply and the circuit being tested during EMI testing; V out1 and Z out1 R represents the output voltage and output impedance of the operational amplifier in the first noise attenuation circuit, respectively. inj1 This indicates the resistance value of the injection resistor in the injection stage of the first noise attenuation circuit;

[0023] The negative bus noise current passing through LISN is:

[0024] (5)

[0025] In equation (4), Z N I N G represents the equivalent negative bus noise source to ground based on Norton's principle. s1 This represents the total gain of the first noise attenuation circuit system;

[0026] The common-mode noise current after LISN is:

[0027] (6)

[0028] The common-mode insertion loss is:

[0029] (7)

[0030] In equations (6) and (7), I CM I represents the original CM noise current of the EUT. DM This represents the original DM noise current of the EUT.

[0031] The beneficial effects of this invention are:

[0032] This invention uses the negative bus as a reference, and the two operational amplifiers use the same power supply system. By constructing an appropriate compensation current path, common-mode noise can be effectively attenuated simultaneously. Furthermore, the common-mode and differential-mode insertion losses can be changed separately by altering the gains of the first and second noise attenuation circuits. Therefore, this invention achieves separate adjustment of the common-mode noise attenuation capability. Attached Figure Description

[0033] Figure 1 This is a circuit diagram of a common-mode attenuation adjustable CM-DM integrated active EMI filter according to the present invention.

[0034] Figure 2This is a schematic diagram of the flow path of the compensation current in this invention;

[0035] Figure 3 This is the equivalent differential-mode EMI noise model of the present invention;

[0036] Figure 4 This is the equivalent differential-mode EMI noise signal flow graph of the present invention;

[0037] Figure 5 This is a diagram of the equivalent negative busbar to ground EMI noise model of the present invention;

[0038] Figure 6 This is the equivalent negative bus to ground EMI noise signal flow diagram of the present invention;

[0039] Figure 7 This invention is when R s1 =1kΩ, R f1 Common-mode insertion loss curves for different values;

[0040] Figure 8 This invention is when R s1 =1kΩ, R f1 Differential mode insertion loss curves for different values;

[0041] Figure 9 This invention is when R s2 =1kΩ, R f2 Common-mode insertion loss curves for different values;

[0042] Figure 10 This invention is when R s2 =1kΩ, R f2 Differential mode insertion loss curves for different values;

[0043] Figure 11 This is a circuit diagram of the present invention;

[0044] Figure 12 This is a diagram showing the common-mode noise suppression effect of the present invention on FSBB;

[0045] Figure 13 This is a diagram showing the differential mode noise suppression effect of the present invention on FSBB.

[0046] In the figure, 101, LISN; 102, EUT; 103, first detection resistor; 104, first operational amplifier; 105, first amplification resistor; 106, first integrating capacitor; 107, first injection resistor; 108, detection capacitor; 109, injection capacitor; 110, second detection resistor; 111, second operational amplifier; 112, second amplification resistor; 113, second integrating capacitor; 114, second injection resistor. Detailed Implementation

[0047] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] refer to Figures 1-13 In this embodiment, the most significant feature of the CM-DM integrated active EMI filter (integrated AEF) with adjustable common-differential mode attenuation is that it uses the negative bus as a reference, the two operational amplifiers use the same power supply system, and the attenuation effect of common-differential mode noise can be adjusted separately. Its structure is as follows: Figure 1 The circuit shown includes a first noise attenuation circuit and a second noise attenuation circuit. Both the first and second noise attenuation circuits consist of a detection stage, an amplification stage, and an injection stage.

[0049] The detection stage of the first noise attenuation circuit consists of a first detection resistor 103, which is used to detect the voltage to ground. One end of the first detection resistor 103 is connected to ground (GND), and the other end is connected to the inverting input of the first operational amplifier 104.

[0050] The amplification stage of the first noise attenuation circuit consists of a first operational amplifier 104, a first amplification resistor 105, and a first integrating capacitor 106. The first operational amplifier 104 and the first amplification resistor 105 amplify the voltage across the first detection resistor 103 in reverse. The first integrating capacitor 106 enhances the stability of the first noise attenuation circuit. The non-inverting input of the first operational amplifier 104 is connected to the negative bus between LISN101 and EUT102, and the inverting input is connected to the first detection resistor 103, the first amplification resistor 105, and the first integrating capacitor 106. The reference ground between the positive and negative terminals of the power supply system is connected to the negative bus between LISN101 and EUT102. The output is connected to the first injection resistor 107, the first amplification resistor 105, and the first integrating capacitor 106. Both the first amplification resistor 105 and the first integrating capacitor 106 are connected across the inverting input and output of the first operational amplifier 104.

[0051] The injection stage of the first noise attenuation circuit consists of a first injection resistor 107, which is used to convert the voltage signal output by the first operational amplifier 104 into a compensation current and inject it back to ground GND. One end of the first injection resistor 107 is connected to the output terminal of the first operational amplifier 104, and the other end is connected to ground GND.

[0052] The detection stage of the second noise attenuation circuit consists of a detection capacitor 108 and a second detection resistor 110; it is used to detect the noise voltage on the positive bus. One end of the detection capacitor 108 is connected to the positive bus between LISN101 and EUT102, and the other end is connected to the second detection resistor 110. One end of the second detection resistor 110 is connected to the detection capacitor 108, and the other end is connected to the inverting input of the second operational amplifier 111.

[0053] The amplification stage of the second noise attenuation circuit consists of a second operational amplifier 111, a second amplification resistor 112, and a second integrating capacitor 113. The second operational amplifier 111 and the second amplification resistor 112 amplify the voltage across the second detection resistor 110 in reverse. The second integrating capacitor 113 enhances the stability of the second noise attenuation circuit. The non-inverting input of the second operational amplifier 111 is connected to the negative bus between LISN101 and EUT102, and the inverting input is connected to the second detection resistor 110, the second amplification resistor 112, and the second integrating capacitor 113. The reference ground between the positive and negative terminals of the power supply system is connected to the negative bus between LISN101 and EUT102, meaning it uses the same power supply system as the first operational amplifier 104 of the first noise attenuation circuit. The output is connected to the second injection resistor 114, the second amplification resistor 112, and the second integrating capacitor 113. The second amplification resistor 112 and the second integrating capacitor 113 are both connected across the inverting input and output of the second operational amplifier 111.

[0054] The injection stage of the second noise attenuation circuit consists of a second injection resistor 114 and an injection capacitor 109; it is used to convert the voltage signal output by the second operational amplifier 111 into a compensation current injected back to the positive bus. One end of the second injection resistor 114 is connected to the output terminal of the first operational amplifier 104, and the other end is connected to the injection capacitor 109. One end of the injection capacitor is connected to the second injection resistor 114, and the other end is connected to the positive bus between LISN101 and EUT102.

[0055] The function of the first noise attenuation circuit is to attenuate the common-mode noise of EUT102. The detection stage of the first noise attenuation circuit detects the voltage at ground (GND). Since the first operational amplifier 104 uses the negative bus as a reference, the signal amplified in the amplification stage is actually the voltage signal on the negative bus. The amplified voltage signal is converted into a current signal after passing through the first injection resistor 107 and injected back into the negative bus, thus canceling the noise signal on the negative bus. The injection capacitor 106 increases the phase margin of the entire first noise attenuation circuit system, eliminates high-frequency ringing, and thus improves system stability.

[0056] The function of the second noise attenuation circuit is to attenuate the common-mode and differential-mode noise of EUT102. The detection stage of the second noise attenuation circuit uses a high-pass filter composed of the second detection resistor 110 and the detection capacitor 108 to detect the noise voltage on the positive bus. Since the second operational amplifier 111 uses the negative bus as a reference, the signal amplified in the amplification stage is actually the differential-mode signal generated by the EUT. After the amplified voltage signal passes through the high-pass filter composed of the injection resistor 109 and the injection capacitor 109, it is converted into a current signal and injected back into the positive bus, thus canceling the differential-mode noise between the positive and negative buses. The injection capacitor 113 increases the phase margin of the entire second noise attenuation circuit system, eliminates high-frequency ringing, and thus improves the system stability.

[0057] Figure 2 The diagram shows the compensation current flow path of the CM-DM integrated active EMI filter with adjustable common-mode attenuation. The light-colored dashed line represents the compensation current flow path of the first noise attenuation circuit. It can be seen that compensation current 1 flows directly from ground through the LISN into the negative bus. Ideally, compensation current 1 equals the amplitude of the negative system differential-mode noise current. The dark-colored dashed line represents the compensation current flow path of the second noise attenuation circuit. It can be seen that compensation current 2 flows from the positive bus through the LISN back to the negative bus. Ideally, compensation current 2 equals the system common-mode noise current minus the differential-mode noise current.

[0058] Next, from the perspective of small-signal analysis, we will derive the formulas for the differential-mode insertion loss and common-mode insertion loss of the CM-DM integrated active EMI filter with adjustable common-mode attenuation. First, we will derive the formula for differential-mode insertion loss. Figure 3 The equivalent differential-mode EMI noise model of a CM-DM integrated active EMI filter with adjustable common-mode attenuation is shown. DM I DM This is an equivalent differential-mode noise source based on Norton's principle. Since the detection and injection stages of the first noise attenuation circuit are both related to ground (GND), the first noise attenuation circuit does not exist in the differential-mode equivalent circuit. The model of the second noise attenuation circuit is shown in the figure. s-LISN For EMI testing, the series impedance of the two branches of a linear impedance stabilizing network needs to be added between the power supply and the circuitry being tested. G s2 V represents the total gain of the second noise attenuation circuit system. out2 and Z out2 Z represents the output voltage and output impedance of the operational amplifier in the second noise attenuation circuit. inj2 This is the impedance of the injection stage in the second noise attenuation circuit. The current flowing through the LISN is I. p The compensation current generated by the second noise attenuation circuit is I. offset2 The equivalent differential-mode EMI noise signal flow graph is as follows: Figure 4 As shown.

[0059] Based on this model, the compensation current generated by the second attenuation circuit can be obtained as follows:

[0060] (1)

[0061] according to Figure 4 The signal flow graph shown can be used to derive the differential-mode noise current after passing through the LISN after adding a CM-DM integrated active EMI filter with adjustable common-differential-mode attenuation:

[0062] (2)

[0063] The insertion loss of the differential mode noise is:

[0064] (3)

[0065] As can be seen from equation (3), the differential mode insertion loss is only related to the second noise attenuation circuit. The differential mode insertion loss of the integrated AEF can be adjusted by adjusting the gain of the second attenuation circuit.

[0066] Next, we will derive the formula for common-mode insertion loss. Figure 5 The equivalent negative bus-to-ground EMI noise model of the CM-DM integrated active EMI filter with adjustable common-mode attenuation is shown. N I N This represents the equivalent negative bus-to-ground noise source based on Norton's principle. Since the detection and injection stages of the second noise attenuation circuit are both related to the positive bus, there is no second noise attenuation circuit in the equivalent negative bus-to-ground circuit. The model of the first noise attenuation circuit is shown in the figure. Z N-LISN This refers to the impedance of one branch of a linear impedance stabilizing network that needs to be added between the power supply and the circuitry being tested for EMI. s1 V represents the total gain of the first noise attenuation circuit system. out1 and Z out1 R represents the output voltage and output impedance of the operational amplifier in the first noise attenuation circuit, respectively. inj1 This is the resistance value of the injection resistor in the injection stage of the first noise attenuation circuit. The negative bus current flowing through the LISN is I. q The compensation current generated by the first noise attenuation circuit is I. offset1 The equivalent negative bus to ground EMI noise signal flow diagram is as follows: Figure 6 As shown.

[0067] Based on this model, the compensation current generated by the first attenuation circuit can be obtained as follows:

[0068] (4)

[0069] according to Figure 6 The signal flow graph shown can be used to derive the negative bus noise current after adding a CM-DM integrated active EMI filter with adjustable common-differential mode attenuation:

[0070] (5)

[0071] The common-mode noise current passing through the LISN is the sum of the differential-mode noise current passing through the LISN and the negative bus noise current. Therefore, the common-mode noise current passing through the LISN is:

[0072] (6)

[0073] Therefore, the common-mode insertion loss is:

[0074] (7)

[0075] Among them I CM I represents the original CM noise current of the EUT. DM This is the original DM noise current of the EUT.

[0076] As can be seen from equation (7), the common-mode insertion loss is related to both the first noise attenuation circuit and the second noise attenuation circuit. The common-mode insertion loss of the integrated AEF can be adjusted by adjusting the gain of the first noise attenuation circuit or the second attenuation circuit.

[0077] The CM-DM integrated active EMI filter with adjustable common-mode attenuation has the following characteristics:

[0078] 1. The op-amp's reference setting is on the negative bus.

[0079] 2. The two operational amplifiers use the same power supply system, which greatly reduces the size of the filter.

[0080] 3. The common-mode and differential-mode insertion losses can be adjusted separately.

[0081] 4. It can significantly attenuate both common-mode noise and differential-mode noise simultaneously.

[0082] This embodiment verifies the adjustable common-mode noise attenuation capability of the designed integrated active EMI filter in simulation. Figure 7 and Figure 8The graphs show the changes in common-mode insertion loss and differential-mode insertion loss when only the gain of the first noise attenuation circuit is changed. It can be observed that when the gain of the first noise attenuation circuit is changed, the common-mode insertion loss increases with increasing gain over a wide frequency range, while the differential-mode insertion loss remains unchanged. This demonstrates that the common-mode insertion loss can be altered by changing the gain of the first noise attenuation circuit. Figure 9 and Figure 10 The changes in common-mode insertion loss and differential-mode insertion loss when only the gain of the second noise attenuation circuit is changed are shown. It can be observed that when the amplification factor of the second noise attenuation circuit is changed, the common-mode insertion loss increases with increasing amplification factor over a wide frequency range, and the differential-mode insertion loss also increases with increasing amplification factor. This indicates that the gain of the second noise attenuation circuit is related to both common-mode and differential-mode insertion losses. Therefore, the common-mode and differential-mode insertion losses can be changed by altering the gain of the second noise attenuation circuit. Consequently, to change the common-mode insertion loss, the gain of the first noise attenuation circuit can be changed; to change the differential-mode insertion loss, the gain of the second noise attenuation circuit can be changed. This allows for separate adjustment of the common-mode and differential-mode noise attenuation capabilities.

[0083] The following describes the parameter design for a common-mode attenuation adjustable CM-DM integrated active EMI filter. For the first noise attenuation circuit, the amplification factor of its amplification stage is mainly related to the sensing resistor R. s1 With amplification resistor R f1 The ratio is related. Integrating capacitor C f1 It should be a capacitor in the pF range to eliminate high-frequency ringing and improve the phase margin of the system.

[0084] For the second noise attenuation circuit, both its detection and injection stages are high-pass filters composed of RC resistors. Its cutoff frequency should be lower than the first peak frequency of the noise in the conducted frequency band. Similar to the first noise attenuation circuit, the amplification factor of its amplification stage is mainly related to the detection resistor R. s2 With amplification resistor R f2 The ratio is related. Integrating capacitor C f2 A pF-level capacitor should be used to eliminate high-frequency ringing and improve the system's phase margin. Table 1 shows the specific parameters and models of the components in the CM-DM integrated active EMI filter with adjustable common-mode attenuation. Figure 11 The image shows the actual product manufactured according to the parameters in Table 1. As you can see, the actual size is very small; it could be made even smaller if the terminals were removed.

[0085]

[0086] Next, the common-mode attenuation adjustable CM-DM integrated active EMI filter was tested in a real-world noise environment. In the actual circuit test, this example first used a relatively new four-switch buck-boost circuit (FSBB). This DC-DC circuit operates at 48Vdc to 48Vdc, with an output current of 1A and a power of 48W. The switching frequency is approximately 200kHz. The T-AEF is supplied with ±5V from an external DC power supply. A noise separator was used to convert noise on the power line into common-mode or differential-mode noise. The common-mode noise test results are as follows: Figure 12 As shown, after adding the integrated AEF, the common-mode noise in the low-frequency band below 1MHz is attenuated by 20-30dB. The differential-mode noise test results are as follows. Figure 13 As shown, after adding the integrated AEF, the differential mode noise is attenuated by 20-30dB across a wide frequency range.

[0087] The abbreviations in this embodiment include:

[0088] LISN Line Impedance Stabilization Network

[0089] EUTEquipment Under Test (Equipment Under Test)

[0090] In summary, this invention, by using the negative bus as a reference and employing the same power supply system for both operational amplifiers, and by constructing appropriate compensation current paths, can simultaneously and effectively attenuate common-mode noise. Furthermore, the common-mode and differential-mode insertion losses can be altered separately by changing the gains of the first and second noise attenuation circuits; therefore, this invention achieves separate adjustment of the common-mode noise attenuation capability. Consequently, this invention has broad application prospects in adjusting the attenuation effect of active EMI filters.

[0091] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications made to the above embodiments based on the technical essence of the present invention are also within the protection scope of the present invention. Other equivalent changes and modifications are still within the scope of the technical solution of the present invention.

Claims

1. A CM-DM integrated active EMI filter with adjustable common-differential mode attenuation, characterized in that, The integrated active EMI filter uses the negative bus as a reference, the two operational amplifiers use the same power supply system, and the attenuation effect of common-differential mode noise can be adjusted separately. The integrated active EMI filter includes: a first noise attenuation circuit and a second noise attenuation circuit; both the first noise attenuation circuit and the second noise attenuation circuit consist of a detection stage, an amplification stage, and an injection stage; The first noise attenuation circuit includes: a first detection resistor (103), a first operational amplifier (104), a first amplification resistor (105), a first integrating capacitor (106), and a first injection resistor (107); the electrical connection of the first noise attenuation circuit includes: one end of the first detection resistor (103) is connected to ground, the other end of the first detection resistor (103) is connected to the inverting input terminal of the first operational amplifier (104), the non-inverting input terminal of the first operational amplifier (104) is connected to the negative bus between LISN (101) and EUT (102), and the first operational amplifier... The output terminal of the device (104) is connected to the first injection resistor (107), and the other end of the first injection resistor (107) is connected to ground; one end of the first amplification resistor (105) and the first integrating capacitor (106) connected in parallel is connected to the inverting input terminal of the first operational amplifier (104), and the other end of the first amplification resistor (105) and the first integrating capacitor (106) connected in parallel is connected to the output terminal of the first operational amplifier (104); the reference ground between the positive and negative terminals of the power supply system of the first operational amplifier (104) is connected to the negative bus between LISN (101) and EUT (102); The second noise attenuation circuit includes: a detection capacitor (108), an injection capacitor (109), a second detection resistor (110), a second operational amplifier (111), a second amplification resistor (112), a second integrating capacitor (113), and a second injection resistor (114); the electrical connection of the second noise attenuation circuit includes: one end of the detection capacitor (108) is connected to the positive bus between LISN (101) and EUT (102), the other end of the detection capacitor (108) is connected to the second detection resistor (110), the other end of the second detection resistor (110) is connected to the inverting input terminal of the second operational amplifier (111), and the non-inverting input terminal of the second operational amplifier (111) is connected between LISN (101) and EUT (102). The negative busbar, the output terminal of the second operational amplifier (111) is connected to the second injection resistor (114), the other end of the second injection resistor (114) is connected to the injection capacitor (109), and the other end of the injection capacitor (109) is connected to the positive busbar between LISN (101) and EUT (102); the second amplification resistor (112) and the second integrating capacitor (113) are connected in parallel, one end of which is connected to the inverting input terminal of the second operational amplifier (111), and the other end of which is connected in parallel is connected to the output terminal of the second operational amplifier (111); the reference ground between the positive and negative terminals of the power supply system of the second operational amplifier (111) is connected to the negative busbar between LISN (101) and EUT (102).

2. The CM-DM integrated active EMI filter with adjustable common-mode attenuation according to claim 1, characterized in that, In the second noise attenuation circuit, the compensation current generated by the second attenuation circuit is: (1) In equation (1), I p Z represents the current flowing through LISN. s-LISN This represents the series impedance of the two branches of the linear impedance stabilization network that needs to be added between the power supply and the circuit being tested during EMI testing. (V) out2 and Z out2 Z represents the output voltage and output impedance of the operational amplifier in the second noise attenuation circuit, respectively. inj2 This represents the impedance of the injection stage in the second noise attenuation circuit. The differential-mode noise current after LISN is: (2) The insertion loss of the differential mode noise is: (3) In equations (2) and (3), Z DM G represents the equivalent differential-mode noise source based on Norton's principle. s2 I represents the total gain of the second noise attenuation circuit system. DM This represents the original DM noise current of the EUT.

3. The CM-DM integrated active EMI filter with adjustable common-mode attenuation according to claim 2, characterized in that, In the first noise attenuation circuit, the compensation current generated by the first attenuation circuit is: (4) In equation (4), I q Z represents the negative bus current flowing through LISN. N-LISN This represents the impedance of one branch of the linear impedance stabilization network that needs to be added between the power supply and the circuit being tested during EMI testing; V out1 and Z out1 R represents the output voltage and output impedance of the operational amplifier in the first noise attenuation circuit, respectively. inj1 This indicates the resistance value of the injection resistor in the injection stage of the first noise attenuation circuit; The negative bus noise current passing through LISN is: (5) In equation (4), Z N G represents the equivalent negative bus noise source to ground based on Norton's principle. s1 This represents the total gain of the first noise attenuation circuit system; The common-mode noise current after LISN is: (6) The common-mode insertion loss is: (7) In equations (6) and (7), I CM I represents the original CM noise current of the EUT. DM This represents the original DM noise current of the EUT.

Images