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

Abstract

The invention belongs to the technical field of power electronics, and relates to a common-mode and differential-mode attenuation adjustable CM-DM integrated active EMI filter, which comprises a first noise attenuation circuit and a second noise attenuation circuit, each of the first noise attenuation circuit and the second noise attenuation circuit consists of a detection link, an amplification link and an injection link; according to the invention, the negative bus is taken as a reference, the two operational amplifiers use the same power supply system, common-mode and differential-mode noise can be effectively attenuated at the same time by constructing a proper compensation current path, and common-mode and differential-mode insertion loss can be respectively changed by changing gains of the first and second noise attenuation circuits; therefore, respective adjustment of common-mode and differential-mode noise attenuation capabilities is realized.

Description

Technical Field

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

[0002] With the widespread use of electronic devices and the continuous increase in operating frequencies, electromagnetic interference (EMI) problems are becoming increasingly serious. The popularity of high-frequency switching circuits and the trend of miniaturization of electronic components have significantly increased the intensity and complexity of electromagnetic interference. These interferences not only affect the normal operation of the equipment, but may also cause serious interference to surrounding equipment and systems. Especially in grid-connected applications, excessive electromagnetic interference may even threaten the stability and security of the power grid. How to effectively suppress EMI has become a key technical problem that needs to be solved urgently in the electronics industry.

[0003] In the process of solving EMI problems, EMI filters have received widespread attention as an important means of suppression. Traditional passive EMI filters are widely used due to their simple structure and high stability, but they are large in size and have limited ability to suppress low-frequency interference, making it difficult to meet the needs of miniaturization and high performance of modern electronic equipment. In contrast, active EMI filters have gradually become a hot spot for research and application due to their excellent low-frequency suppression effect, smaller size and adjustable performance. With the advancement of control algorithms and power device technology, active EMI filters have shown higher integration and broader application prospects while improving filtering performance, becoming an important solution to the increasingly severe EMI problem.

[0004] Active EMI filter (AEF) is mainly composed of three parts: noise detection, noise amplification and noise compensation. The noise detection part has two methods: current detection and voltage sampling. The noise compensation part and current sampling also have two methods: current compensation and voltage compensation. Therefore, according to the difference between the detection part and the compensation part, the active EMI filter can be divided into current-sensing current-compensating (CSCC), current-sensing voltage-compensating (CSVC), voltage-sensing current-compensating (VSCC), and voltage-sensing voltage-compensating (VSVC). Since current detection requires the use of current transformers and voltage compensation requires the use of transformers, both of which require a large volume, the use of voltage-sensing current-compensating active EMI filters can achieve a smaller volume.

[0005] Active EMI filters are divided into common-mode AEF and differential-mode AEF according to the type of attenuated noise. Their working principles and design methods are basically similar, but the specific compensation paths are different. In the traditional AEF topology, the common-mode AEF is mainly referenced to the earth GND, and the differential-mode AEF is mainly referenced to the negative bus. Because the reference settings of the common-mode and differential-mode AEF are different, if there are both common-mode and differential-mode AEF in the circuit, two power supply systems are required. This will greatly increase the volume of the AEF system. The specific working principle of the existing integrated AEF circuit is to detect the positive / negative bus noise and inject it back into the positive / negative bus. This topology uses the earth GND as a reference, and the attenuation effect of the common-mode and differential-mode noise cannot be adjusted separately.

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

[0007] Therefore, a method or device is needed to simultaneously attenuate both common-mode noise and differential-mode noise and to be adjustable to solve the above technical problems. Summary of the invention

[0008] The technical solution adopted by the present invention to solve the technical problem is: a CM-DM integrated active EMI filter with adjustable common-differential mode attenuation, 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 the common-differential mode noise can be adjusted respectively;

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

[0010] The first noise attenuation circuit includes: a first detection resistor, a first operational amplifier, a first amplifying resistor, a first integral capacitor, and a first injection resistor; the electrical connection method of the first noise attenuation circuit includes: one end of the first detection resistor is connected to the ground, the other end of the first detection resistor is connected to the inverting input terminal of the first operational amplifier, the non-inverting input terminal of the first operational amplifier is connected to the negative bus between the LISN and the EUT, the output terminal of the first operational amplifier is connected to the first injection resistor, and the other end of the first injection resistor is connected to the ground; one end of the first amplifying resistor connected in parallel with the first integral capacitor is connected to the inverting input terminal of the first operational amplifier, and the other end of the first amplifying resistor connected in parallel with the first integral capacitor is connected to the output terminal of the first operational amplifier; the reference ground between the positive and negative poles of the power supply system of the first operational amplifier is connected to the negative bus between the LISN and the EUT;

[0011] The second noise attenuation circuit includes: a detection capacitor, an injection capacitor, a second detection resistor, a second operational amplifier, a second amplifying resistor, a second integrating capacitor, and a second injection resistor; the electrical connection mode of the second noise attenuation circuit includes: one end of the detection capacitor is connected to the positive bus between the LISN and the 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 terminal of the second operational amplifier, the non-inverting input terminal of the second operational amplifier is connected to the negative bus between the LISN and the EUT, the output terminal 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 the EUT; one end of the second amplifying resistor connected in parallel with the second integrating capacitor is connected to the inverting input terminal of the second operational amplifier, and the other end of the second amplifying resistor connected in parallel with the second integrating capacitor is connected to the output terminal of the second operational amplifier; the reference ground between the positive and negative poles of the power supply system of the second operational amplifier is connected to the negative bus between the LISN and the EUT.

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

[0013]

[0014] In formula (1), I p represents the current flowing through the LISN, Z s-LISN It 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 target circuit during EMI testing. V out2 and Z out2 denote the output voltage and output impedance of the operational amplifier of the second noise attenuation circuit, Z inj2 represents the impedance of the injection link of the second noise attenuation circuit;

[0015] The differential mode noise current passing through LISN is:

[0016]

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

[0018]

[0019] In formula (2) and formula (3), Z DM ,I DM represents the equivalent differential mode noise source based on the Norton principle, G s2 represents the overall 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]

[0022] In formula (4), I q It represents the negative bus current flowing through LISN, Z N-LISN It represents the impedance of a branch of the linear impedance stabilization network that needs to be added between the power supply and the target circuit during EMI testing. V out1 and Z out1 denote the output voltage and output impedance of the operational amplifier of the first noise reduction circuit, R inj1 represents the resistance value of the injection resistor in the injection link of the first noise attenuation circuit;

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

[0024]

[0025] In formula (4), Z N ,I N It represents the equivalent negative bus noise source based on Norton principle, G s1 represents an overall gain of the first noise attenuation circuit system;

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

[0027]

[0028] The common mode insertion loss is:

[0029]

[0030] In formula (6) and formula (7), I CM Represents the original CM noise current of the EUT, I DM Indicates the original DM noise current of the EUT.

[0031] The beneficial effects of the present invention are:

[0032] The present 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, the common-mode and differential-mode noise can be effectively attenuated at the same time, and the common-mode and differential-mode insertion losses can be changed respectively by changing the gains of the first and second noise attenuation circuits; therefore, the present invention realizes the separate adjustment of the common-mode and differential-mode noise attenuation capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a circuit structure diagram of a CM-DM integrated active EMI filter with adjustable common-differential mode attenuation according to the present invention;

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

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

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

[0037] Figure 5 This is an equivalent negative bus-to-ground EMI noise model diagram 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 The present invention is when R s1 =1kΩ, R f1 Common mode insertion loss curve for different values;

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

[0041] Fig. 9 The present invention is when R s2 =1kΩ, R f2 Common mode insertion loss curve for different values;

[0042] Fig.10 The present invention is when R s2 =1kΩ, R f2 Differential mode insertion loss curve for different values;

[0043] Fig.11 It is a circuit diagram of the present invention;

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

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

[0046] In the figure, 101 is a LISN; 102 is an EUT; 103 is a first detection resistor; 104 is a first operational amplifier; 105 is a first amplifying resistor; 106 is a first integrating capacitor; 107 is a first injection resistor; 108 is a detection capacitor; 109 is an injection capacitor; 110 is a second detection resistor; 111 is a second operational amplifier; 112 is a second amplifying resistor; 113 is a second integrating capacitor; 114 is a second injection resistor. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technologies in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] refer to Figures 1 to 13 In this embodiment, the biggest 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, wherein 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.

[0049] The detection link of the first noise attenuation circuit is composed of a first detection resistor 103 for detecting the voltage of the earth. One end of the first detection resistor 103 is connected to the earth GND, and the other end is connected to the inverting input end of the first operational amplifier 104.

[0050] The amplification link of the first noise attenuation circuit is composed of a first operational amplifier 104, a first amplifying resistor 105 and a first integrating capacitor 106; wherein the first operational amplifier 104 and the first amplifying resistor 105 are used to reversely amplify the voltage across the first detection resistor 103; the first integrating capacitor 106 is used to enhance the stability of the first noise attenuation circuit. The first operational amplifier 104 has a non-inverting input terminal connected to the negative bus between the LISN 101 and the EUT 102, an inverting input terminal connected to the first detection resistor 103, the first amplifying resistor 105 and the first integrating capacitor 106, a reference ground between the positive and negative poles of the power supply system connected to the negative bus between the LISN 101 and the EUT 102, and an output terminal connected to the first injection resistor 107, the first amplifying resistor 105 and the first integrating capacitor 106. The first amplifying resistor 105 and the first integrating capacitor 106 are both connected across the inverting input terminal and the output terminal of the first operational amplifier 104.

[0051] The injection link of the first noise attenuation circuit is composed 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 into the ground GND. One end of the first injection resistor 107 is connected to the output end of the first operational amplifier 104, and the other end is connected to the ground GND.

[0052] The detection link of the second noise attenuation circuit is composed of a detection capacitor 108 and a second detection resistor 110, which are used to detect the noise voltage of the positive bus. One end of the detection capacitor 108 is connected to the positive bus between the LISN 101 and the EUT 102, 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 terminal of the second operational amplifier 111.

[0053] The amplification link of the second noise attenuation circuit is composed of a second operational amplifier 111, a second amplifying resistor 112 and a second integrating capacitor 113; wherein the second operational amplifier 111 and the second amplifying resistor 112 are used to reversely amplify the voltage across the second detection resistor 110; the second integrating capacitor 113 is used to enhance the stability of the second noise attenuation circuit. The in-phase input terminal of the second operational amplifier 111 is connected to the negative bus between the LISN 101 and the EUT 102, the inverting input terminal is connected to the second detection resistor 110, the second amplifying resistor 112 and the second integrating capacitor 113, the reference ground between the positive and negative poles of the power supply system is connected to the negative bus between the LISN 101 and the EUT 102, that is, the same power supply system is used as the first operational amplifier 104 of the first noise attenuation circuit, and the output terminal is connected to the second injection resistor 114, the second amplifying resistor 112 and the second integrating capacitor 113. The second amplifying resistor 112 and the second integrating capacitor 113 are both connected across the inverting input terminal and the output terminal of the second operational amplifier 111.

[0054] The injection link of the second noise attenuation circuit is composed 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 and inject it back into the positive bus. One end of the second injection resistor 114 is connected to the output end 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 the LISN 101 and the EUT 102.

[0055] The function of the first noise attenuation circuit is to attenuate the common mode noise of EUT102. The detection link of the first noise attenuation circuit is to detect the voltage of the earth GND. Since the first operational amplifier 104 uses the negative bus as a reference, the signal amplified by the amplification link 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, which can offset the noise signal on the negative bus. The injection capacitor 106 can increase the phase margin of the entire first noise attenuation circuit system, eliminate high-frequency ringing, and thus improve the stability of the system.

[0056] The function of the second noise attenuation circuit is to attenuate the common mode noise and differential mode noise of EUT102. The detection link of the second noise attenuation circuit is to form a high-pass filter through the second detection resistor 110 and the detection capacitor 108 to detect the noise voltage of the positive bus. Since the second operational amplifier 111 uses the negative bus as a reference, the signal amplified in the amplification link 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, which can offset the differential mode noise between the positive and negative buses. Among them, the injection capacitor 113 can increase the phase margin of the entire second noise attenuation circuit system, eliminate high-frequency ringing, and thus improve the stability of the system.

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

[0058] Next, from the perspective of small signal analysis, the differential mode insertion loss and common mode insertion loss formulas of the CM-DM integrated active EMI filter with adjustable common and differential mode attenuation will be derived. First, the differential mode insertion loss formula will be derived. Figure 3 The equivalent differential mode EMI noise model of the CM-DM integrated active EMI filter with adjustable common and differential mode attenuation is shown. DM ,I DM is an equivalent differential mode noise source based on the Norton principle. Since the detection and injection links of the first noise attenuation circuit are both related to the ground GND, the first noise attenuation circuit does not exist in the differential mode equivalent circuit. The model of the second noise attenuation circuit has been marked in the figure. s-LISN For EMI testing, it is necessary to add the series impedance of the two branches of the linear impedance stabilization network between the power supply and the target circuit. s2 represents the total gain of the second noise attenuation circuit system, V out2 and Z out2 are the output voltage and output impedance of the operational amplifier of the second noise attenuation circuit, respectively. inj2 is the impedance of the injection link of 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 diagram is as follows: Figure 4 shown.

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

[0060]

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

[0062]

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

[0064]

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

[0066] Next, the common-mode insertion loss formula is derived. Figure 5 The equivalent negative bus-to-ground EMI noise model of the CM-DM integrated active EMI filter with adjustable common-differential mode attenuation is shown. N ,I N is the equivalent negative bus-to-ground noise source based on the Norton principle. Since the detection and injection links of the second noise attenuation circuit are both related to the positive bus, there is no second noise attenuation circuit in the negative bus-to-ground equivalent circuit. The model of the first noise attenuation circuit has been marked in the figure. N-LISN For EMI testing, it is necessary to add the impedance of a branch of the linear impedance stabilization network between the power supply and the target circuit. s1 represents the total gain of the first noise attenuation circuit system, V out1 and Z out1 are the output voltage and output impedance of the operational amplifier of the first noise reduction circuit, respectively. inj1 is the resistance of the injection resistor in the injection link 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 shown.

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

[0068]

[0069] according to Figure 6 The signal flow diagram shown can be used to deduce that after adding the CM-DM integrated active EMI filter with adjustable common-differential mode attenuation, the negative bus noise current passing through the LISN is:

[0070]

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

[0072]

[0073] So the common mode insertion loss is:

[0074]

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

[0076] It can be seen from formula (7) that 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 common-differential mode attenuation adjustable CM-DM integrated active EMI filter has the following characteristics:

[0078] 1. The reference of the op amp is set 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. 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.

[0082] This embodiment verifies the adjustable common and differential mode noise attenuation capability of the designed integrated active EMI filter in simulation. Figure 7 and Figure 8 The changes in common-mode insertion loss and differential-mode insertion loss when only the gain of the first noise attenuation circuit is changed are shown respectively. It can be found from the figure that when the amplification factor of the first noise attenuation circuit is changed, the common-mode insertion loss increases with the increase of the amplification factor in a wide frequency range, while the differential-mode insertion loss does not change. This shows that the common-mode insertion loss can be changed by changing the gain of the first noise attenuation circuit. Fig. 9 and Fig.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 respectively. It can be found that when the amplification factor of the second noise attenuation circuit is changed, the common-mode insertion loss will increase with the increase of the amplification factor within a wide frequency band, and the differential-mode insertion loss will also increase with the increase of the amplification factor. This shows that the gain of the second noise attenuation circuit is related to both the common-mode insertion loss and the differential-mode insertion loss. The common-mode insertion loss and the differential-mode insertion loss can be changed by changing the gain of the second noise attenuation circuit. It can be seen that when you want to change the common-mode insertion loss, you can change the gain of the first noise attenuation circuit, and when you want to change the differential-mode insertion loss, you can change the gain of the second noise attenuation circuit. In this way, the common-mode and differential-mode noise attenuation capabilities are adjusted separately.

[0083] The following is the design of the parameters in the common-differential mode attenuation adjustable CM-DM integrated active EMI filter. For the first noise attenuation circuit, the amplification factor of its amplification link is mainly related to the detection resistor R s1 With the amplifier resistor R f1 The integral 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 the detection link and the injection link are high-pass filters composed of RC. Its cut-off frequency should be lower than the first peak frequency of the noise in the conduction frequency band. As with the first noise attenuation circuit, the amplification factor of its amplification link is mainly related to the detection resistor R s2 With the amplifier resistor R f2 The integral capacitor C f2 It should be a capacitor of pF level to eliminate high frequency ringing and improve the phase margin of the system. Table 1 shows the specific parameters and models of the components in the CM-DM integrated active EMI filter with adjustable common-differential mode attenuation. Fig.11 The actual picture is made according to the parameters in Table 1. It can be seen that the size of the actual object is very small, and it can be made even smaller if the terminal is removed.

[0085] Table 1

[0086]

[0087] Next, the CM-DM integrated active EMI filter with adjustable common-differential mode attenuation is tested in an actual noise environment. In the actual circuit test, this example first uses the relatively new four-switch buck-boost circuit (FSBB). The working condition of this DC-DC circuit is 48Vdc to 48Vdc, the output current is 1A, and the power is 48W. The switching frequency is about 200kHz. The supply voltage of T-AEF is ±5V, which is provided by an additional DC power supply. A noise separator is used to convert the noise on the power line into common-mode or differential-mode noise. The test results of common-mode noise are shown in the figure. Fig.12 As shown in the figure, it can be seen that after adding the integrated AEF, the common mode noise in the low frequency band below 1MHz is attenuated by 20-30dB. The test results of differential mode noise are as follows Fig.13 As shown, it can be seen that after adding the integrated AEF, the differential mode noise in the wide frequency band is attenuated by 20-30dB.

[0088] The abbreviations in this embodiment include:

[0089] LISN Line Impedance Stabilization Network Line Impedance Stabilization Network

[0090] EUT Equipment Under Test

[0091] In summary, the present invention uses the negative bus as a reference, and two operational amplifiers use the same power supply system. By constructing an appropriate compensation current path, the common and differential mode noises can be effectively attenuated at the same time, and the common mode and differential mode insertion losses can be changed respectively by changing the gains of the first and second noise attenuation circuits; therefore, the present invention realizes the separate adjustment of the common and differential mode noise attenuation capabilities. Therefore, the present invention has a wide application prospect in the attenuation effect adjustment of active EMI filters.

[0092] It should be emphasized that the above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Any simple modification of the above embodiments based on the technical essence of the present invention also falls within the protection scope of the present invention. Other equivalent changes and modifications still fall 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 effects of common and differential mode noise can be adjusted respectively; The integrated active EMI filter comprises: 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 first noise attenuation circuit comprises: a first detection resistor (103), a first operational amplifier (104), a first amplifying resistor (105), a first integrating capacitor (106), and a first injection resistor (107); the electrical connection method of the first noise attenuation circuit comprises: one end of the first detection resistor (103) is connected to the ground, the other end of the first detection resistor (103) is connected to the inverting input end of the first operational amplifier (104), the non-inverting input end of the first operational amplifier (104) is connected to the negative bus between the LISN (101) and the EUT (102), and the first operational amplifier (104) is connected to the ground. The output end of the amplifier (104) is connected to a first injection resistor (107), and the other end of the first injection resistor (107) is connected to the ground; one end of the first amplifying resistor (105) connected in parallel with the first integrating capacitor (106) is connected to the inverting input end of the first operational amplifier (104), and the other end of the first amplifying resistor (105) connected in parallel with the first integrating capacitor (106) is connected to the output end of the first operational amplifier (104); the reference ground between the positive and negative electrodes of the power supply system of the first operational amplifier (104) is connected to the negative bus between the LISN (101) and the EUT (102); The second noise attenuation circuit comprises: 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 integration capacitor (113), and a second injection resistor (114); the electrical connection method of the second noise attenuation circuit comprises: one end of the detection capacitor (108) is connected to the positive bus between the LISN (101) and the 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 end of the second operational amplifier (111), and the non-inverting input end of the second operational amplifier (111) is connected to the positive bus between the LISN (101) and the EUT (102). The output end 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 bus between the LISN (101) and the EUT (102); one end of the second amplifying resistor (112) and the second integrating capacitor (113) connected in parallel is connected to the inverting input end of the second operational amplifier (111), and the other end of the second amplifying resistor (112) and the second integrating capacitor (113) connected in parallel is connected to the output end of the second operational amplifier (111); and the reference ground between the positive and negative poles of the power supply system of the second operational amplifier (111) is connected to the negative bus between the LISN (101) and the EUT (102).

2. The CM-DM integrated active EMI filter with adjustable common-differential 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: In formula (1), I p represents the current flowing through the LISN, Z s-LISN It 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 target circuit during EMI testing. V out2 and Z out2 denote the output voltage and output impedance of the operational amplifier of the second noise attenuation circuit, Z inj2 represents the impedance of the injection link of the second noise attenuation circuit; The differential mode noise current passing through LISN is: The insertion loss of differential mode noise is: In formula (2) and formula (3), Z DM ,I DM represents the equivalent differential mode noise source based on the Norton principle, G s2 represents the overall gain of the second noise attenuation circuit system.

3. The CM-DM integrated active EMI filter with adjustable common-differential 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: In formula (4), I q It represents the negative bus current flowing through LISN, Z N-LISN It represents the impedance of a branch of the linear impedance stabilization network that needs to be added between the power supply and the target circuit during EMI testing. V out1 and Z out1 denote the output voltage and output impedance of the operational amplifier of the first noise reduction circuit, R inj1 represents the resistance value of the injection resistor in the injection link of the first noise attenuation circuit; The negative bus noise current through the LISN is: In formula (4), Z N ,I N It represents the equivalent negative bus noise source based on Norton principle, G s1 represents an overall gain of the first noise attenuation circuit system; The common-mode noise current through LISN is: The common mode insertion loss is: In formula (6) and formula (7), I CM Represents the original CM noise current of the EUT, I DM Indicates the original DM noise current of the EUT.

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