Power EMI filter

Abstract

The invention relates to the technical field of filters, and provides a power EMI filter. The power EMI filter comprises a differential mode filter circuit and a common mode filter circuit. The differential mode filter circuit comprises a first-stage differential mode capacitor bank, a second-stage differential mode capacitor bank, a first differential mode inductor and a second differential mode inductor; the common-mode filter circuit comprises a first-stage common-mode capacitor bank, a second-stage common-mode capacitor bank, a first common-mode inductor and a second common-mode inductor; the first-stage differential-mode capacitor bank and the second-stage differential-mode capacitor bank are connected in parallel, the first-stage differential-mode capacitor bank is connected to the upstream of the first common-mode inductor, and the second-stage differential-mode capacitor bank is connected to the downstream of the first common-mode inductor; the first-stage common-mode capacitor bank is connected to the upstream of the second common-mode inductor, and the second-stage common-mode capacitor bank is connected to the downstream of the second common-mode inductor; the first differential mode inductor is connected with one end of the second-stage common mode capacitor bank, and the second differential mode inductor is connected with the other end of the second-stage common mode capacitor bank; the differential mode interference suppression frequency band can be effectively widened, and the suppression effect can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of filters, and more specifically, to a power supply EMI filter. Background Art

[0002] With the continuous advancement of switching power supply technology, switching power supplies are becoming more and more common in various applications. The working principle of a switching power supply is to rectify, invert, rectify and filter the industrial frequency AC power, and finally output a stable DC voltage. This process involves multiple stages, in which the semiconductor devices used (such as MOSFET and IGBT) will generate discontinuous electrical waveforms during switching operations. This discontinuity causes complex higher harmonics in the output voltage and current. Higher harmonics are waveforms with a frequency higher than the fundamental frequency. Their presence not only affects the efficiency of the power supply, but also causes electromagnetic noise. These electromagnetic noises are transmitted through near-field coupling and far-field radiation, forming conducted interference and radiated interference. Conducted interference refers to interference transmitted through conductors such as power lines, while radiated interference refers to interference signals transmitted through media such as air. The current operating frequency band of the filter is relatively narrow. When it is applied to electronic systems, the electromagnetic compatibility power supply conducted emission test will fail.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a power supply EMI filter, aiming to solve the technical problem that the operating frequency band of the filter in the related art is relatively narrow.

[0005] To achieve the above purpose, the technical solution adopted in this application is:

[0006] The present application provides a power supply EMI filter, which includes: a differential mode filter circuit and a common mode filter circuit;

[0007] The differential mode filter circuit comprises a first-stage differential mode capacitor group, a second-stage differential mode capacitor group, a first differential mode inductor and a second differential mode inductor;

[0008] The common-mode filtering circuit comprises a first-stage common-mode capacitor group, a second-stage common-mode capacitor group, a first common-mode inductor and a second common-mode inductor;

[0009] The first differential mode capacitor group and the second differential mode capacitor group are connected in parallel, the first differential mode capacitor group is connected upstream of the first common mode inductor, and the second differential mode capacitor group is connected downstream of the first common mode inductor;

[0010] The second-stage differential mode capacitor group is connected in parallel with the first-stage common mode capacitor group;

[0011] The first-stage common-mode capacitor group is connected to the upstream of the second common-mode inductor, and the second-stage common-mode capacitor group is connected to the downstream of the second common-mode inductor;

[0012] The first differential mode inductor is connected to one end of the second stage common mode capacitor group, and the second differential mode inductor is connected to the other end of the second stage common mode capacitor group.

[0013] In some implementations, the first-stage common-mode capacitor group is located downstream of the second-stage differential-mode capacitor group.

[0014] In some implementations, the first-stage differential mode capacitor group includes a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in parallel.

[0015] In some implementations, the second-stage differential mode capacitor group includes a third capacitor and a fourth capacitor, and the third capacitor and the fourth capacitor are connected in parallel.

[0016] In some implementations, the first-stage common-mode capacitor group includes a fifth capacitor and a sixth capacitor, the fifth capacitor and the sixth capacitor are connected in series, and a connection point between the fifth capacitor and the sixth capacitor is grounded.

[0017] In some implementations, the second-stage common-mode capacitor group includes a seventh capacitor and an eighth capacitor, the seventh capacitor and the eighth capacitor are connected in series, and a connection point between the seventh capacitor and the eighth capacitor is grounded.

[0018] In some implementations, the capacitance of the first capacitor is equal to the capacitance of the second capacitor, the capacitance of the third capacitor is equal to the capacitance of the fourth capacitor, and the capacitance of the first capacitor is greater than the capacitance of the third capacitor.

[0019] In some implementations, the capacitance of the fifth capacitor is equal to the capacitance of the sixth capacitor, the capacitance of the seventh capacitor is equal to the capacitance of the eighth capacitor, and the capacitance of the fifth capacitor is greater than the capacitance of the seventh capacitor.

[0020] In some implementations, the material of the magnetic core of the first differential mode inductor includes iron, nickel and molybdenum, and the material of the magnetic core of the second differential mode inductor includes iron, nickel and molybdenum;

[0021] The material of the magnetic core of the first common-mode inductor is nanocrystalline material, and the material of the magnetic core of the second common-mode inductor is nanocrystalline material.

[0022] In some implementations, the power supply EMI filter further includes a housing having a housing cavity, and the differential mode filter circuit and the common mode filter circuit are installed in the housing cavity.

[0023] The beneficial effects of the power supply EMI filter provided in this application are mainly:

[0024] The power supply EMI filter provided by the present application, using the first-stage differential mode capacitor group, the second-stage differential mode capacitor group, the first differential mode inductor and the second differential mode inductor, can effectively widen the differential mode interference suppression frequency band and improve the suppression effect, so that the differential mode insertion loss of the power supply EMI filter in the 50KHz~1MHz frequency band is as high as 60dB. And using the first-stage common mode capacitor group, the second-stage common mode capacitor group, the first common mode inductor and the second common mode inductor, the common mode insertion loss of the power supply EMI filter in the 5MHz~30MHz frequency band reaches 60dB, and the common mode insertion loss in the 20MHz~30MHz frequency band reaches up to 80dB; after being applied to the electronic system, the electronic system can pass the electromagnetic compatibility power supply conduction emission test, effectively suppress the interference signal generated by the switching power supply of the electronic system, and ensure that the interference signal generated by the electronic system cannot be transmitted to the power supply network, and prevent the interference signal in the power supply network from being transmitted into the electronic system, thereby improving the electromagnetic compatibility performance of the electronic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is a front view of the power supply EMI filter provided in an embodiment of the present application;

[0027] Figure 2 is a top view of a power supply EMI filter provided in an embodiment of the present application;

[0028] Figure 3 is a schematic diagram of the interior of a power supply EMI filter provided in an embodiment of the present application;

[0029] Figure 4 It is a circuit diagram of a power supply EMI filter provided in an embodiment of the present application.

[0030] Description of main reference numerals:

[0031] 101. housing; 102. electronic wire; 103. ground pad. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] In order to illustrate the technical solution described in this application, a detailed description is given below in conjunction with specific drawings and embodiments.

[0037] See also Figure 3 and Figure 4As shown, in one or more embodiments, the present application provides a power supply EMI (Electromagnetic An electromagnetic interference (EMI) filter, comprising: a differential mode filter circuit and a common mode filter circuit; the differential mode filter circuit comprises a first-stage differential mode capacitor group, a second-stage differential mode capacitor group, a first differential mode inductor L3 and a second differential mode inductor L4; the common mode filter circuit comprises a first-stage common mode capacitor group, a second-stage common mode capacitor group, a first common mode inductor L1 and a second common mode inductor L2; the first-stage differential mode capacitor group and the second-stage differential mode capacitor group are connected in parallel, the first-stage differential mode capacitor group is connected to the upstream of the first common mode inductor L1, and the second-stage differential mode capacitor group is connected to the downstream of the first common mode inductor L1; the second-stage differential mode capacitor group is connected in parallel with the first-stage common mode capacitor group; the first-stage common mode capacitor group is connected to the upstream of the second common mode inductor L2, and the second-stage common mode capacitor group is connected to the downstream of the second common mode inductor L2; the first differential mode inductor L3 is connected to one end of the second-stage common mode capacitor group, and the second differential mode inductor L4 is connected to the other end of the second-stage common mode capacitor group.

[0038] The power supply EMI filter provided in the embodiment of the present application has a wide operating frequency band, and its operating frequency band is 10KHz~30MHz, and the whole frequency band has high insertion loss. The power supply EMI filter uses the first-stage differential mode capacitor group, the second-stage differential mode capacitor group, the first differential mode inductor L3 and the second differential mode inductor L4 to effectively widen the differential mode interference suppression frequency band and improve the suppression effect, so that the differential mode insertion loss of the power supply EMI filter in the 50KHz~1MHz frequency band is as high as 60dB. And by using the first-stage common mode capacitor group, the second-stage common mode capacitor group, the first common mode inductor L1 and the second common mode inductor L2, the common mode insertion loss of the power supply EMI filter in the 5MHz~30MHz frequency band reaches 60dB, and the common mode insertion loss in the 20MHz~30MHz frequency band reaches up to 80dB. After being applied to electronic systems, they can enable the electronic systems to pass the electromagnetic compatibility power supply conducted emission test, solve the problem of the electronic systems exceeding the limit of the electromagnetic compatibility CE102 test, and focus on the design of the 20MHz~30MHz frequency band to solve the problem of exceeding the limit of the electromagnetic compatibility RE102 test in this band; the power supply EMI filter can effectively suppress the interference signal generated by the switching power supply of the electronic system, ensuring that the interference signal generated by the electronic system cannot be transmitted to the power supply network, and preventing the interference signal in the power supply network from being transmitted into the electronic system, thereby improving the electromagnetic compatibility performance of the electronic system.

[0039] See also Figure 3 and Figure 4As shown, in some embodiments, one end of the first differential mode capacitor group is connected to the positive input end of the power supply EMI filter, and the other end of the first differential mode capacitor group is connected to the negative input end of the power supply EMI filter. One end of the first differential mode capacitor group is connected to the first end of the first common mode inductor L1, and the other end of the first differential mode capacitor group is connected to the second end of the first common mode inductor L1. One end of the second differential mode capacitor group is connected to the third end of the first common mode inductor L1, and the other end of the second differential mode capacitor group is connected to the fourth end of the first common mode inductor L1. One end of the second differential mode capacitor group is connected to one end of the first common mode capacitor group, and the other end of the second differential mode capacitor group is connected to the other end of the first common mode capacitor group. One end of the first common mode capacitor group is connected to the first end of the second common mode inductor L2, and the other end of the first common mode capacitor group is connected to the second end of the second common mode inductor L2. One end of the second-stage common-mode capacitor group is connected to the third end of the second common-mode inductor L2, and the other end of the second-stage common-mode capacitor group is connected to the fourth end of the second common-mode inductor L2. One end of the first differential-mode inductor L3 is connected to one end of the second-stage common-mode capacitor group, and the other end of the first differential-mode inductor L3 is connected to the positive output end of the power supply EMI filter. One end of the second differential-mode inductor L4 is connected to one end of the second-stage common-mode capacitor group, and the other end of the second differential-mode inductor L4 is connected to the negative output end of the power supply EMI filter. Through two common-mode inductors and two differential-mode inductors, the power supply EMI filter has a three-stage filtering structure, thereby widening the filtering frequency band.

[0040] See also Figure 3 and Figure 4 As shown, in some embodiments, the first-stage common-mode capacitor group is located downstream of the second-stage differential-mode capacitor group, so that the upstream and downstream of the first common-mode inductor L1 are the first-stage differential-mode capacitor group and the second-stage differential-mode capacitor group, respectively, and the upstream and downstream of the second common-mode inductor L2 are the first-stage common-mode capacitor group and the second-stage common-mode capacitor group, respectively, which is beneficial to ensure the power supply EMI filter's ability to suppress low-frequency differential-mode interference and high-frequency common-mode interference, and improve the performance and stability of the circuit.

[0041] See also Figure 3 and Figure 4As shown, in some embodiments, the first differential mode capacitor group includes a first capacitor C1 and a second capacitor C2, and the first capacitor C1 and the second capacitor C2 are connected in parallel, so that the first capacitor C1 and the second capacitor C2 are used to process the differential mode signal. Exemplarily, one end of the first capacitor C1 is connected to the positive input end of the power supply EMI filter, and the other end of the first capacitor C1 is connected to the negative input end of the power supply EMI filter; one end of the second capacitor C2 is connected to one end of the first capacitor C1, and the other end of the second capacitor C2 is connected to the other end of the first capacitor C1; one end of the second capacitor C2 is connected to the first end of the first common mode inductor L1, and the other end of the second capacitor C2 is connected to the second end of the first common mode inductor L1.

[0042] In some embodiments, the capacitance of the first capacitor C1 is 4.7μF to 12μF, and the capacitance of the second capacitor C2 is 4.7μF to 12μF. Exemplarily, the capacitance of the first capacitor C1 is 4.7μF, 8.5μF, 10μF or 12μF; the capacitance of the second capacitor C2 is 4.7μF, 8.5μF, 10μF or 12μF.

[0043] In some embodiments, the capacitance of the first capacitor C1 is equal to the capacitance of the second capacitor C2 . For example, the capacitance of the first capacitor C1 and the capacitance of the second capacitor C2 are both 10 μF.

[0044] See also Figure 3 and Figure 4 As shown, in some embodiments, the second-stage differential mode capacitor group includes a third capacitor C3 and a fourth capacitor C4, and the third capacitor C3 and the fourth capacitor C4 are connected in parallel, so that the first capacitor C1 and the second capacitor C2 are used to process the differential mode signal. In addition, the third capacitor C3 and the fourth capacitor C4 are located downstream of the first common mode inductor L1, so that the common mode signal is suppressed while processing the differential mode signal. Exemplarily, one end of the third capacitor C3 is connected to the third end of the first common mode inductor L1, the other end of the third capacitor C3 is connected to the fourth end of the first common mode inductor L1, one end of the fourth capacitor C4 is connected to one end of the third capacitor C3, and the other end of the fourth capacitor C4 is connected to the other end of the third capacitor C3.

[0045] In some embodiments, the capacitance of the third capacitor C3 is 680nF to 2.2μF, and the capacitance of the fourth capacitor C4 is 680nF to 2.2μF. Exemplarily, the capacitance of the third capacitor C3 is 680nF, 1μF, 1.4μF or 2μF; the capacitance of the fourth capacitor C4 is 680nF, 1μF, 1.4μF or 2μF.

[0046] In some embodiments, the capacitance of the third capacitor C3 is equal to that of the fourth capacitor C4, the capacitance of the first capacitor C1 is greater than that of the third capacitor C3, and the capacitance of the second capacitor C2 is greater than that of the third capacitor C3. For example, the capacitance of the third capacitor C3 and the capacitance of the fourth capacitor C4 are both 1 μF.

[0047] See also Figure 3 and Figure 4 As shown, in some embodiments, the first-stage common-mode capacitor group includes a fifth capacitor C5 and a sixth capacitor C6, the fifth capacitor C5 and the sixth capacitor C6 are connected in series, and the connection between the fifth capacitor C5 and the sixth capacitor C6 is grounded, so that the fifth capacitor C5 and the sixth capacitor C6 cooperate with the first common-mode inductor L1 to suppress the common-mode signal. Exemplarily, one end of the fifth capacitor C5 is connected to the first end of the second common-mode inductor L2, and one end of the sixth capacitor C6 is connected to the second end of the second common-mode inductor L2; the other end of the fifth capacitor C5 is connected to the other end of the sixth capacitor C6, and the common point where the two are connected is grounded.

[0048] In some embodiments, the capacitance of the fifth capacitor C5 is 100nF to 680nF, and the capacitance of the sixth capacitor C6 is 100nF to 680nF. Exemplarily, the capacitance of the fifth capacitor C5 is 100nF, 390nF, 470nF or 680nF; the capacitance of the sixth capacitor C6 is 100nF, 390nF, 470nF or 680nF.

[0049] In some embodiments, the capacitance of the fifth capacitor C5 is equal to the capacitance of the sixth capacitor C6. For example, the capacitance of the fifth capacitor C5 and the capacitance of the sixth capacitor C6 are both 470 nF.

[0050] See also Figure 3 and Figure 4 As shown, in some embodiments, the second-stage common-mode capacitor group includes a seventh capacitor C7 and an eighth capacitor C8, the seventh capacitor C7 and the eighth capacitor C8 are connected in series, and the connection between the seventh capacitor C7 and the eighth capacitor C8 is grounded, so that the common-mode signal can be further suppressed. Exemplarily, one end of the seventh capacitor C7 is connected to the third end of the second common-mode inductor L2, one end of the eighth capacitor C8 is connected to the fourth end of the second common-mode inductor L2, the other end of the seventh capacitor C7 is connected to the other end of the eighth capacitor C8, and the common point where the two are connected is grounded. One end of the first differential-mode inductor L3 is connected to one end of the seventh capacitor C7. One end of the second differential-mode inductor L4 is connected to one end of the eighth capacitor C8.

[0051] In some embodiments, the capacitance of the seventh capacitor C7 is 1nF to 10nF, and the capacitance of the eighth capacitor C8 is 1nF to 10nF. Exemplarily, the capacitance of the seventh capacitor C7 is 1nF, 5nF, 6nF or 10nF; the capacitance of the eighth capacitor C8 is 1nF, 5nF, 6nF or 10nF.

[0052] In some embodiments, the capacitance of the seventh capacitor C7 is equal to the capacitance of the eighth capacitor C8. For example, the capacitance of the seventh capacitor C7 and the capacitance of the eighth capacitor C8 are both 1 nF.

[0053] In some embodiments, the capacitance of the fifth capacitor C5 is greater than the capacitance of the seventh capacitor C7, and the capacitance of the sixth capacitor C6 is greater than the capacitance of the seventh capacitor C7.

[0054] In some embodiments, the material of the magnetic core of the first differential mode inductor L3 includes iron, nickel and molybdenum, and the material of the magnetic core of the second differential mode inductor L4 includes iron, nickel and molybdenum. In this way, the magnetic core of the first differential mode inductor L3 and the second differential mode inductor core are both iron-nickel-molybdenum material cores with high saturation flux density. At the same time, the first-stage differential mode capacitor group and the second-stage differential mode capacitor group are cooperated to achieve low-frequency differential mode interference, and can effectively widen the differential mode interference suppression frequency band and improve the suppression effect, so that the differential mode insertion loss of the power supply EMI filter in the 50KHz~1MHz frequency band is as high as 60dB.

[0055] In some embodiments, the material of the magnetic core of the first common-mode inductor L1 is nanocrystalline material, and the material of the magnetic core of the second common-mode inductor L2 is nanocrystalline material, so that the first common-mode inductor L1 and the second common-mode inductor L2 are both nanocrystalline material cores with high magnetic permeability, and are combined with the first-stage common-mode capacitor group and the second-stage common-mode capacitor group, so that the common-mode insertion loss of the power supply EMI filter in the 5MHz~30MHz frequency band reaches 60dB, and the common-mode insertion loss in the 20MHz~30MHz frequency band is as high as 80dB.

[0056] In some embodiments, the positive input terminal, the negative input terminal, the positive output terminal, and the negative output terminal of the power EMI filter are all in the form of electronic wires 102 .

[0057] In some embodiments, the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, the sixth capacitor, the seventh capacitor and the eighth capacitor may all be ceramic capacitors.

[0058] Combination Figures 1 to 3As shown, in some embodiments, the power supply EMI filter also includes a shell 101, the shell has a shell cavity, the differential mode filter circuit and the common mode filter circuit are installed in the shell cavity, and a grounding pad 103 is arranged inside the shell 101, so that the other end of the fifth capacitor C5, the other end of the sixth capacitor C6, the other end of the seventh capacitor C7, and the other end of the eighth capacitor C8 are respectively connected to the grounding pad 103 to achieve grounding, so that the power supply EMI filter can guide the electromagnetic interference of the electronic system to the ground through the common mode capacitor.

[0059] In the embodiment of the present application, the power EMI filter is a DC filter with a rated voltage of 200VDC. When in use, the power EMI filter is applied to the power port of the electronic system, that is, installed at the front end of the power module of the electronic system, so that the electronic system can pass the electromagnetic compatibility power conduction emission test, effectively suppress the interference signal generated by the switching power supply, play a bidirectional filtering role, filter out the electromagnetic interference transmitted from the power grid to the electronic system and the electromagnetic interference sent by the electronic system to the power grid, that is, to ensure that the interference signal generated inside the electronic system cannot be transmitted to the power network, and prevent the interference signal in the power network from being transmitted into the electronic system, thereby improving the electromagnetic compatibility performance of the entire electronic system.

[0060] The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A power supply EMI filter, characterized in that: include: A differential mode filter circuit, the differential mode filter circuit comprising a first-stage differential mode capacitor group, a second-stage differential mode capacitor group, a first differential mode inductor and a second differential mode inductor; as well as A common-mode filter circuit, the common-mode filter circuit comprising a first-stage common-mode capacitor group, a second-stage common-mode capacitor group, a first common-mode inductor and a second common-mode inductor; The first differential mode capacitor group and the second differential mode capacitor group are connected in parallel, the first differential mode capacitor group is connected upstream of the first common mode inductor, and the second differential mode capacitor group is connected downstream of the first common mode inductor; The second-stage differential mode capacitor group is connected in parallel with the first-stage common mode capacitor group; The first-stage common-mode capacitor group is connected to the upstream of the second common-mode inductor, and the second-stage common-mode capacitor group is connected to the downstream of the second common-mode inductor; The first differential mode inductor is connected to one end of the second stage common mode capacitor group, and the second differential mode inductor is connected to the other end of the second stage common mode capacitor group.

2. The power supply EMI filter according to claim 1, characterized in that: The first-stage common-mode capacitor group is located downstream of the second-stage differential-mode capacitor group.

3. The power supply EMI filter according to claim 1 or 2, characterized in that: The first-stage differential mode capacitor group includes a first capacitor and a second capacitor, and the first capacitor and the second capacitor are connected in parallel.

4. The power supply EMI filter according to claim 3, characterized in that: The second-stage differential mode capacitor group includes a third capacitor and a fourth capacitor, and the third capacitor and the fourth capacitor are connected in parallel.

5. The power supply EMI filter according to claim 1 or 2, characterized in that: The first-stage common-mode capacitor group includes a fifth capacitor and a sixth capacitor, the fifth capacitor and the sixth capacitor are connected in series, and a connection point between the fifth capacitor and the sixth capacitor is grounded.

6. The power supply EMI filter according to claim 5, characterized in that: The second-stage common-mode capacitor group includes a seventh capacitor and an eighth capacitor, the seventh capacitor and the eighth capacitor are connected in series, and a connection point between the seventh capacitor and the eighth capacitor is grounded.

7. The power supply EMI filter according to claim 4, characterized in that: The capacitance of the first capacitor is equal to the capacitance of the second capacitor, the capacitance of the third capacitor is equal to the capacitance of the fourth capacitor, and the capacitance of the first capacitor is greater than the capacitance of the third capacitor.

8. The power supply EMI filter according to claim 6, characterized in that: The capacitance of the fifth capacitor is equal to the capacitance of the sixth capacitor, the capacitance of the seventh capacitor is equal to the capacitance of the eighth capacitor, and the capacitance of the fifth capacitor is greater than the capacitance of the seventh capacitor.

9. The power supply EMI filter according to claim 1 or 2, characterized in that: The material of the magnetic core of the first differential mode inductor includes iron, nickel and molybdenum, and the material of the magnetic core of the second differential mode inductor includes iron, nickel and molybdenum; The material of the magnetic core of the first common-mode inductor is nanocrystalline material, and the material of the magnetic core of the second common-mode inductor is nanocrystalline material.

10. The power supply EMI filter according to claim 1 or 2, characterized in that: The power supply EMI filter further comprises a shell having a shell cavity, wherein the differential mode filter circuit and the common mode filter circuit are installed in the shell cavity.

Images