EMI filter
By tilting the X capacitor to generate negative coupling flux, the problems of mutual inductance and increased size in traditional EMI filters are solved, improving performance and simplifying the modeling process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional EMI filters face challenges in reducing mutual inductance between capacitors and minimizing size, resulting in high sensitivity to design parameters and complex simulation modeling.
By tilting the first X capacitor and the second X capacitor at a certain angle relative to the axis of the common-mode inductor, negative coupling magnetic flux is generated between the capacitors, reducing mutual inductance and improving the performance of the EMI filter without the need to add additional components.
This approach achieves an overall performance improvement for EMI filters, reduces mutual inductance, simplifies the simulation modeling process, and maintains a small design size.
Smart Images
Figure CN121864046A_ABST
Abstract
Description
Technical Field
[0001] This case involves EMI filters, specifically a small-sized EMI filter. Background Technology
[0002] EMI filters contain electromagnetic interference, and the magnetic field coupling between capacitors within the filter generates mutual inductance, leading to decreased filtering performance or abnormal frequency response. To reduce mutual inductance, traditional EMI filters increase the distance between capacitors. However, because the high permeability core of the common-mode inductor (CMC) is typically positioned between two capacitors, the mutual inductance increases, thus negating the reduction achieved by increasing the distance between capacitors. This also increases the overall size of the EMI filter.
[0003] Another traditional EMI filter utilizes the wiring layout within the printed circuit board to generate negative coupling flux, thus canceling the positive coupling flux between capacitors. However, to achieve sufficient mutual inductance cancellation, traditional EMI filters require longer traces on the printed circuit board, resulting in a looser component arrangement and increased overall filter size. Furthermore, the length, width, and spacing of the traces on the printed circuit board must be precisely corrected using finite element method (FEM) simulation, complicating the manufacturing process and demanding high accuracy in capacitor modeling and software simulation. Therefore, both of these traditional EMI filters suffer from drawbacks such as increased size, high sensitivity to design parameters, and complex simulation modeling.
[0004] Therefore, it is necessary to develop an EMI filter to solve the problems faced by previous technologies. Summary of the Invention
[0005] The purpose of this invention is to provide an EMI filter in which a first X capacitor is tilted at a first angle relative to the axis of a common-mode inductor, and / or a second X capacitor is tilted at a second angle relative to the axis of a common-mode inductor, so that there is negative coupling between the parasitic inductance of the first X capacitor and the parasitic inductance of the second X capacitor, thereby generating mutual inductance, thereby improving the overall performance of the EMI filter to achieve the best results. The EMI filter of this invention does not require additional components and can simultaneously achieve the advantages of reducing mutual inductance to improve overall performance, thereby reducing the difficulty of simulation modeling and other advantages.
[0006] To achieve the above objectives, this invention provides an EMI filter comprising a circuit board, a common-mode inductor, a first X capacitor, and a second X capacitor. The common-mode inductor is disposed on the circuit board. The first X capacitor is disposed on the circuit board and located on a first side of the common-mode inductor's axial direction. The second X capacitor is disposed on the circuit board and located on a second side of the common-mode inductor's axial direction, the second side being opposite to the first side. The first X capacitor is tilted at a first angle relative to the common-mode inductor's axial direction, and / or the second X capacitor is tilted at a second angle relative to the common-mode inductor's axial direction.
[0007] In some embodiments, the first X capacitor is tilted relative to the second X capacitor at a relative angle.
[0008] In some embodiments, the relative angle is 90 degrees.
[0009] In some embodiments, the shortest distance between the first terminal of the first X capacitor and the common-mode inductor is different from the shortest distance between the second terminal of the first X capacitor and the common-mode inductor, and / or the shortest distance between the first terminal of the second X capacitor and the common-mode inductor is different from the shortest distance between the second terminal of the second X capacitor and the common-mode inductor.
[0010] In some embodiments, the first X capacitor includes a first end and a second end disposed opposite to each other, and the first X capacitor is tilted at a first angle relative to the axis of the common mode inductor with the first end or the second end approaching the common mode inductor in a direction, the first angle ranging from 0 degrees to 90 degrees; and / or the second X capacitor includes a first end and a second end disposed opposite to each other, and the second X capacitor is tilted at a second angle relative to the axis of the common mode inductor with the first end or the second end approaching the common mode inductor in a direction, the second angle ranging from 0 degrees to 90 degrees.
[0011] In some embodiments, the first X capacitor is parallel to the second X capacitor.
[0012] In some embodiments, the EMI filter further includes two first Y capacitors and two second Y capacitors. The two first Y capacitors are disposed on a circuit board and are located on opposite sides of the first X capacitor, respectively. The two second Y capacitors are disposed on a circuit board and are located on opposite sides of the second X capacitor, respectively.
[0013] In some embodiments, one of the two first Y capacitors is located between the common-mode inductor and the first X capacitor, and one of the two second Y capacitors is located between the common-mode inductor and the second X capacitor.
[0014] In some embodiments, the connection between the two first Y capacitors is perpendicular to the orientation of the first X capacitor; and / or the connection between the two second Y capacitors is perpendicular to the orientation of the second X capacitor.
[0015] In some embodiments, the EMI filter further includes two first Y capacitors and two second Y capacitors, the two first Y capacitors being located on the same side of the first X capacitor, and the first X capacitor being located between the two first Y capacitors and the common-mode inductor; and / or the two second Y capacitors being located on the same side of the second X capacitor, and the second X capacitor being located between the two second Y capacitors and the common-mode inductor.
[0016] In some embodiments, the positive connection terminals of the first X capacitor and the second X capacitor are located on opposite sides of the common-mode inductor, and the negative connection terminals of the first X capacitor and the second X capacitor are located on opposite sides of the common-mode inductor. The common-mode inductor includes a magnetic core, a first winding, and a second winding. The first winding and the second winding are wound on the magnetic core. The two ends of the first winding are respectively connected to the positive connection terminals of the first X capacitor and the second X capacitor, and the two ends of the second winding are respectively connected to the negative connection terminals of the first X capacitor and the second X capacitor.
[0017] In some embodiments, the positive connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor, and the negative connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor. The common-mode inductor includes a magnetic core, a first winding, and a second winding. The first winding and the second winding are wound on the magnetic core. The two ends of the first winding are respectively connected to the positive connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor, and the two ends of the second winding are respectively connected to the negative connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor.
[0018] In some embodiments, the first winding and the second winding are respectively wound on opposite sides of the common-mode inductor passing through the axial direction, or respectively wound on opposite sides of the common-mode inductor along the axial direction. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the structural topology of the EMI filter in the first embodiment of this case.
[0020] Figure 2 for Figure 1 The diagram shows the equivalent circuit topology of some components in the EMI filter.
[0021] Figure 3 for Figure 1 The diagram shows the arrangement of the two X capacitors in the EMI filter.
[0022] Figure 4 This is a schematic diagram of the structural topology of the EMI filter in the second embodiment of this case.
[0023] Figure 5 for Figure 4 The diagram shows the equivalent circuit topology of some components in the EMI filter.
[0024] Figure 6 This is a schematic diagram of the structural topology of the EMI filter in the third embodiment of this case.
[0025] Figure 7 This is a schematic diagram of the structural topology of the EMI filter in the fourth embodiment of this case.
[0026] Figure 8 This is a schematic diagram of the structural topology of the EMI filter in the fifth embodiment of this case.
[0027] Figure 9 This is a schematic diagram of the structural topology of the EMI filter in the sixth embodiment of this case.
[0028] Figure 10 This is a schematic diagram of the structural topology of the EMI filter in the seventh embodiment of this case.
[0029] Figure 11 This is a schematic diagram of the structural topology of the EMI filter in the eighth embodiment of this case.
[0030] List of reference numerals
[0031] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g: EMI filters
[0032] 2: Circuit board
[0033] 3: Common mode inductor
[0034] A: Axial
[0035] 31: Magnetic core
[0036] 32: First winding
[0037] 32a: First end
[0038] 32b: Second end
[0039] 33: Second winding
[0040] 33a: First end
[0041] 33b: Second end
[0042] 41: First X capacitor
[0043] 41a: First end
[0044] 41b: Second end
[0045] θ1: First angle
[0046] 42: Second X capacitor
[0047] 42a: First end
[0048] 42b: Second end
[0049] θ2: Second angle
[0050] 51: First Y capacitor
[0051] 52: Second Y capacitor
[0052] Ls1, Ls2, Ld, ESL: Inductors
[0053] EPC, Cx: Capacitors
[0054] EPR, ESR: Resistance
[0055] k: First magnetic flux
[0056] m: Second magnetic flux
[0057] Ic1, Ic2, J: Current Detailed Implementation
[0058] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different forms, all of which do not depart from the scope of this invention, and the descriptions and drawings therein are for illustrative purposes only and not for limiting this invention.
[0059] For example, different embodiments in this disclosure may use repeated reference numerals and / or designations. These repetitions are for simplification and clarity and are not intended to limit the relationships between the various embodiments and / or the described appearance structures. Furthermore, when a component is referred to as being "connected to" or "coupled to" another component, it may be directly connected to or coupled to the other component, or there may be intervening components. Additionally, it is understood that while terms such as "first," "second," and "third" may be used in the claims to describe different components, these components should not be limited by these terms, and the components described accordingly in the embodiments are represented by different component symbols. These terms are used to distinguish different components. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component without departing from the scope of the embodiments. The term "and / or" as thus used includes any or all combinations of one or more of the related listed items.
[0060] Please see Figure 1 and Figure 2 ,in Figure 1 This is a schematic diagram of the structural topology of the EMI filter in the first embodiment of this case. Figure 2 for Figure 1 The diagram shows the equivalent circuit topology of some components in the EMI filter. Figure 1As shown, the EMI filter 1 in this embodiment includes a circuit board 2, a common-mode inductor 3, a first X capacitor 41, a second X capacitor 42, two first Y capacitors 51, and two second Y capacitors 52. The common-mode inductor 3 is disposed on the circuit board 2 and has an axial direction A. In this embodiment, the common-mode inductor 3 includes a magnetic core 31, a first winding 32, and a second winding 33. The magnetic core 31 of the common-mode inductor 3 is disposed on the circuit board 2. The first winding 32 of the common-mode inductor 3 is wound on the magnetic core 31 and includes a first end 32a and a second end 32b, wherein the first end 32a and the second end 32b of the first winding 32 are opposite ends of the first winding 32. The second winding 33 of the common-mode inductor 3 is wound on the magnetic core 31, located on opposite sides of the first winding 32 and spaced apart, and includes a first end 33a and a second end 33b, wherein the first end 33a and the second end 33b of the second winding 33 are opposite ends of the second winding 33. Figure 1 In the embodiment shown, the axis A of the common mode inductor 3 is shown in a direction perpendicular to the center line of the first X capacitor 41 and the second X capacitor 42. It can be understood that the axis A of the common mode inductor 3 is not limited to this and will be adjusted accordingly as the positions of the first X capacitor 41 and the second X capacitor 42 change.
[0061] The first X capacitor 41 is disposed on the circuit board 2 and located on the first side of the common mode inductor 3, that is, on the first side of the axial direction A of the common mode inductor 3. The first X capacitor 41 includes a first end 41a and a second end 41b, which, for example, constitute the positive connection end and the negative connection end of the first X capacitor 41, respectively. The first end 41a and the second end 41b of the first X capacitor 41 are located at opposite ends of the first X capacitor 41. The first end 41a of the first X capacitor 41 is connected to the first end 32a of the first winding 32, and the second end 41b of the first X capacitor 41 is connected to the first end 33a of the second winding 33. The second X capacitor 42 is disposed on the circuit board 2 and located on the second side of the common-mode inductor 3 relative to the first side, that is, on the second side of the common-mode inductor 3 relative to the first side along the axial direction A. The second X capacitor 42 includes a first end 42a and a second end 42b, which, for example, constitute the positive connection terminal and the negative connection terminal of the second X capacitor 42, respectively. The first end 42a and the second end 42b of the second X capacitor 42 are located at opposite ends of the second X capacitor 42. The first end 42a of the second X capacitor 42 is connected to the second end 32b of the first winding 32, and the second end 42b of the second X capacitor 42 is connected to the second end 33b of the second winding 33. In this embodiment, the first end 41a (positive connection terminal) of the first X capacitor 41 and the first end 42a (positive connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3, and the second end 41b (negative connection terminal) of the first X capacitor 41 and the second end 42b (negative connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3.
[0062] The first X capacitor 41 is tilted relative to the axial direction A of the common-mode inductor 3 at a first angle θ1, with either its first end 41a or its second end 41b approaching the common-mode inductor 3. The first angle θ1 ranges from, for example, 0 degrees to 90 degrees. The shortest distance between the first end 41a of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3 is different from the shortest distance between the second end 41b of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3. For example... Figure 1 In the illustrated embodiment, the first X capacitor 41 is tilted at a first angle θ1 relative to the axial direction A of the common-mode inductor 3, with its first end 41a close to the common-mode inductor 3. The shortest distance between the first end 41a of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3 is less than the shortest distance between the second end 41b of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3. It is understood that the shortest distance between the first end 41a of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3 can also be greater than the shortest distance between the second end 41b of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3; this application does not impose limitations on this.
[0063] The second X capacitor 42 is tilted relative to the axial direction A of the common-mode inductor 3 at a second angle θ2, with either its first end 42a or its second end 42b approaching the common-mode inductor 3. The range of the second angle θ2 is, for example, 0 degrees to 90 degrees. The shortest distance between the first end 42a of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3 is different from the shortest distance between the second end 42b of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3. For example... Figure 1 In the illustrated embodiment, the second X capacitor 42 is tilted at a second angle θ2 relative to the axial direction A of the common-mode inductor 3, with its first end 42a closer to the common-mode inductor 3. The shortest distance between the first end 42a of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3 is less than the shortest distance between the second end 42b of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3. It is understood that the shortest distance between the first end 42a of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3 can also be greater than the shortest distance between the second end 42b of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3; this application does not impose limitations on this.
[0064] In other words, in this embodiment, the first X capacitor 41 is tilted relative to the second X capacitor 42 at a relative angle, preferably 90 degrees, that is, the first X capacitor 41 and the second X capacitor 42 are arranged perpendicular to each other. Of course, in some embodiments, only one of the first X capacitors 41 or the second X capacitor 42 is tilted relative to the axis A of the common mode inductor 3, and the other X capacitor can be arranged parallel to the axis A of the common mode inductor 3, and is not limited thereto.
[0065] In this embodiment, the current in the winding flows sequentially through the first end 41a of the first X capacitor 41, the first end 32a and the second end 32b of the first winding 32, the first end 42a and the second end 42b of the second X capacitor 42, the second end 33b and the first end 33a of the second winding 33, and the second end 41b of the first X capacitor 41. Thus, the first winding 32 and the second winding 33 are wound, for example, on opposite sides of the common-mode inductor 3 passing through the axial direction A; however, this application is not limited to this.
[0066] Two first Y capacitors 51 are disposed on the circuit board 2, respectively located on opposite sides of the first X capacitor 41. One of the two first Y capacitors 51 is located between the first X capacitor 41 and the common-mode inductor 3. In this embodiment, the line connecting the two first Y capacitors 51 is perpendicular to the setting direction of the first X capacitor 41. Two second Y capacitors 52 are disposed on the circuit board 2, respectively located on opposite sides of the second Y capacitor 52. One of the two second Y capacitors 52 is located between the second X capacitor 42 and the common-mode inductor 3. In this embodiment, the line connecting the two second Y capacitors 52 is perpendicular to the setting direction of the second X capacitor 42. According to the above arrangement of Y capacitors, the installation area can be reduced. Of course, the number of first Y capacitors 51 and second Y capacitors 52 is not limited to two, and can be more than two. This application does not impose any limitation.
[0067] Regarding circuit topology, such as Figure 2 As shown, inductor Ls1 forms the first winding 32 of common-mode inductor 3, inductor Ls2 forms the second winding 33 of common-mode inductor 3, inductor Ld forms the leakage inductance of common-mode inductor 3, capacitor EPC and resistor EPR form the parasitic capacitance and parasitic resistance of common-mode inductor 3, respectively, two capacitors Cx form the first X capacitor 41 and the second X capacitor 42, respectively, two resistors ESR form the parasitic resistance of the first X capacitor 41 and the second X capacitor 42, respectively, and two inductors ESL form the parasitic inductance of the first X capacitor 41 and the second X capacitor 42, respectively. According to Figure 2 It is known that the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42 (i.e., the two inductors ESL) of the EMI filter 1 are positively coupled, which reduces mutual inductance. The reduced mutual inductance between the parasitic inductances of the two X capacitors has a significant impact on the overall performance of the EMI filter 1. According to data evaluation, when the mutual inductance between the parasitic inductances of the two X capacitors is 0, the resonant frequency of the X capacitors and their parasitic inductances can reach the maximum value, thereby making the overall performance of the EMI filter 1 optimal. In other words, the EMI filter 1 can improve its overall performance by reducing the mutual inductance between the parasitic inductances of the two X capacitors.
[0068] As can be seen from the above, the first X capacitor 41 of the EMI filter 1 in this case is tilted at a first angle θ1 relative to the axis A of the common mode inductor 3, and / or the second X capacitor 42 is tilted at a second angle θ2 relative to the axis A of the common mode inductor 3. This reduces the coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42, thereby reducing mutual inductance and improving the overall performance of the EMI filter 1 to achieve the best results. Compared with traditional EMI filters, the EMI filter in this case does not require additional components and can simultaneously achieve the advantages of reducing mutual inductance to improve overall performance, thereby reducing the difficulty of simulation modeling and other advantages.
[0069] Please see Figure 3 and cooperate Figure 1 and Figure 2 ,in Figure 3 for Figure 1 The diagram shows the arrangement of the two X capacitors in the EMI filter. As shown, in this embodiment, the first X capacitor 41 and the second X capacitor 42 are perpendicular to each other. For ease of analysis, the first X capacitor 41 and the second X capacitor 42 are each divided into nine cuboid units. Figure 3 The direction of the magnetic flux generated by the current J is represented by the first magnetic flux k and the second magnetic flux m. The two cuboid units that are closest to each other in the first X capacitor 41 and the second X capacitor 42 (i.e. Figure 3 The magnetic fluxes between the cuboid units indicated by the diagonal lines are perpendicular to each other, and the loops of the first magnetic flux k and the second magnetic flux m will not intersect each other. According to the following formula (1), the mutual inductance between the first X capacitor 41 and the second X capacitor 42 is ( ) and the unit vectors of the two magnetic fluxes along their respective current density directions ( The magnetic flux coupling between the first X capacitor 41 and the second X capacitor 42 is directly proportional to the magnetic flux coupling. Therefore, when the magnetic flux coupling between the first X capacitor 41 and the second X capacitor 42 decreases, the mutual inductance between them also decreases. Furthermore, when the first X capacitor 41 and the second X capacitor 42 are positioned perpendicular to each other, e k e m =0, there is no magnetic field coupling between the first X capacitor 41 and the second X capacitor 42, thus achieving the technical effect of minimizing mutual inductance.
[0070]
[0071] According to EMI filter performance testing and evaluation, the performance of two X capacitors with negatively coupled parasitic inductances is better than that with positively coupled parasitic inductances. Furthermore, with negative coupling, a smaller absolute value of the mutual inductance achieves better performance. Please refer to [link / reference]. Figure 4 and Figure 5,in Figure 4 This is a schematic diagram of the structural topology of the EMI filter in the second embodiment of this case. Figure 5 for Figure 4 The diagram shows the equivalent circuit topology of some components in the EMI filter. Figure 4 As shown, the EMI filter 1a in this embodiment is similar to... Figure 1 The EMI filter 1 shown is compared to Figure 1 The first terminal 41a (positive connection terminal) of the first X capacitor 41 and the first terminal 42a (positive connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The second terminal 41b (negative connection terminal) of the first X capacitor 41 and the second terminal 42b (negative connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The first terminal 42a (positive connection terminal) of the second X capacitor 42 is connected to the second terminal 32b of the first winding 32, and the second terminal 42b (negative connection terminal) of the second X capacitor 42 is connected to the second terminal 33b of the second winding 33, thus creating positive coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42. In the embodiment of the EMI filter 1a, the first terminal 41a (positive connection terminal) of the first X capacitor 41 and the first terminal 42a (negative connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The second terminal 41b (negative connection terminal) of the first X capacitor 41 and the second terminal 42b (positive connection terminal) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The first terminal 42a (negative connection terminal) of the second X capacitor 42 is connected to the second terminal 33b of the second winding 33, and the second terminal 42b (positive connection terminal) of the second X capacitor 42 is connected to the second terminal 32b of the first winding 32, thereby creating negative coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42. Regarding the circuit topology, as follows... Figure 5 As shown, the second X capacitor 42 is connected to the common-mode inductor 3 in an anti-parallel manner. The current Ic1 of the first X capacitor 41 and the current Ic2 of the second X capacitor 42 are in phase but opposite in direction. According to the right-hand screw rule, the first X capacitor 41 and the second X capacitor 42 generate mutually canceling magnetic flux directions, so that the absolute value of the mutual inductance between the first X capacitor 41 and the second X capacitor 42 in this embodiment is equal to the absolute value of the mutual inductance between the first X capacitor 41 and the second X capacitor 42 in the first embodiment. Therefore, the EMI filter 1a in this embodiment can simultaneously reduce the mutual inductance between the first X capacitor 41 and the second X capacitor 42, and achieve the advantage of negative coupling between the first X capacitor 41 and the second X capacitor 42.
[0072] Of course, in some embodiments, the positions of the first Y capacitor and the second Y capacitor can be adjusted as needed. Please refer to [link / reference]. Figure 6 This is a schematic diagram of the structural topology of the EMI filter in the third embodiment of this case. Compared to Figure 1 As shown in the figure, the two first Y capacitors 51 of the EMI filter 1b in this embodiment are located on the same side of the first X capacitor 41, and the first X capacitor 41 is located between the two first Y capacitors 51 and the common mode inductor 3; the two second Y capacitors 52 are located on the same side of the second X capacitor 42, and the second X capacitor 42 is located between the two second Y capacitors 52 and the common mode inductor 3.
[0073] Of course, if the parasitic inductances of the two X capacitors are negatively coupled, the positions of the first Y capacitor and the second Y capacitor can also be adjusted as needed. Please refer to [link / reference]. Figure 7 This is a schematic diagram of the structural topology of the EMI filter in the fourth embodiment of this case. Compared to Figure 4 As shown in the figure, the two first Y capacitors 51 of the EMI filter 1c in this embodiment are located on the same side of the first X capacitor 41, and the first X capacitor 41 is located between the two first Y capacitors 51 and the common mode inductor 3; the two second Y capacitors 52 are located on the same side of the second X capacitor 42, and the second X capacitor 42 is located between the two second Y capacitors 52 and the common mode inductor 3.
[0074] Of course, in some embodiments, the positions of the first winding 32 and the second winding 33 can be adjusted as needed. Please refer to [link / reference]. Figure 6 and Figure 7 Compared to Figure 1 The first winding 32 and the second winding 33 of the EMI filter 1 shown are wound on opposite sides of the common-mode inductor 3 passing through the axial direction A, as follows: Figure 6 and Figure 7 In the embodiment shown, the current in the winding flows sequentially through the first end 41a of the first X capacitor 41, the first end 32a and the second end 32b of the first winding 32, the first end 42a and the second end 42b of the second X capacitor 42, the second end 33b and the first end 33a of the second winding 33, and the second end 41b of the first X capacitor 41. The first winding 32 and the second winding 33 of the EMI filter 1b are wound on opposite sides of the axial direction A of the common mode inductor 3, wherein the connection relationship between the first X capacitor 41 and the second X capacitor 42 and the first winding 32 and the second winding 33 is as follows: Figure 1 and Figure 4 The embodiments shown are similar.
[0075] In some embodiments, the location of the X capacitor can also be adjusted as needed. Please refer to [link / reference]. Figure 8 This is a schematic diagram of the structural topology of the EMI filter in the fifth embodiment of this case. Compared to Figure 1As shown in the figure, the second X capacitor 42 of the EMI filter 1d in this embodiment is tilted at a second angle θ2 relative to the axial direction A of the common-mode inductor 3, with its second end 42b close to the common-mode inductor 3. The shortest distance between the first end 42a of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3 is greater than the shortest distance between the second end 42b of the second X capacitor 42 and the magnetic core 31 of the common-mode inductor 3. Furthermore, the first X capacitor 41 and the second X capacitor 42 are tilted relative to the axial direction A of the common-mode inductor 3, and the first X capacitor 41 is arranged parallel to the second X capacitor 42. In this embodiment, the first end 41a (positive connection end) of the first X capacitor 41 and the first end 42a (positive connection end) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The second end 41b (negative connection end) of the first X capacitor 41 and the second end 42b (negative connection end) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The first end 41a (positive connection end) of the first X capacitor 41 is connected to the first end 32a of the first winding 32, the second end 41b (negative connection end) of the first X capacitor 41 is connected to the first end 33a of the second winding 33, the first end 42a (positive connection end) of the second X capacitor 42 is connected to the second end 32b of the first winding 32, and the second end 42b (negative connection end) of the second X capacitor 42 is connected to the second end 33b of the second winding 33. This results in positive coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42. In this embodiment, the parasitic inductance between the first X capacitor 41 and the second X capacitor 42 can also be reduced by decreasing coupling and thus reducing mutual inductance.
[0076] Please see Figure 9 This is a schematic diagram of the structural topology of the EMI filter in the sixth embodiment of this case. Compared to Figure 1As shown in the figure, the first X capacitor 41 of the EMI filter 1e in this embodiment is tilted at a first angle θ1 relative to the axial direction A of the common-mode inductor 3 with its second end 41b close to the common-mode inductor 3. The shortest distance between the first end 41a of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3 is greater than the shortest distance between the second end 41b of the first X capacitor 41 and the magnetic core 31 of the common-mode inductor 3. Furthermore, the first X capacitor 41 and the second X capacitor 42 are tilted relative to the axial direction A of the common-mode inductor 3, and the first X capacitor 41 is arranged parallel to the second X capacitor 42. In this embodiment, the first end 41a (positive connection end) of the first X capacitor 41 and the first end 42a (positive connection end) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The second end 41b (negative connection end) of the first X capacitor 41 and the second end 42b (negative connection end) of the second X capacitor 42 are located on opposite sides of the common-mode inductor 3. The first end 41a (positive connection end) of the first X capacitor 41 is connected to the first end 32a of the first winding 32, the second end 41b (negative connection end) of the first X capacitor 41 is connected to the first end 33a of the second winding 33, the first end 42a (positive connection end) of the second X capacitor 42 is connected to the second end 32b of the first winding 32, and the second end 42b (negative connection end) of the second X capacitor 42 is connected to the second end 33b of the second winding 33. This results in positive coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42. In this embodiment, the parasitic inductance between the first X capacitor 41 and the second X capacitor 42 can also be reduced by decreasing coupling and thus reducing mutual inductance.
[0077] Please see Figure 10 This is a schematic diagram of the structural topology of the EMI filter in the seventh embodiment of this case. Compared to Figure 8 As shown in the figure, in this embodiment of the EMI filter 1d, the first end 41a (positive connection end) of the first X capacitor 41 and the first end 42a (negative connection end) of the second X capacitor 42 are located on opposite sides of the common mode inductor 3. The second end 41b (negative connection end) of the first X capacitor 41 and the second end 42b (positive connection end) of the second X capacitor 42 are located on opposite sides of the common mode inductor 3. The first end 41a (positive connection end) of the first X capacitor 41 is connected to the first end 32a of the first winding 32, the second end 41b (negative connection end) of the first X capacitor 41 is connected to the first end 33a of the second winding 33, the first end 42a (negative connection end) of the second X capacitor 42 is connected to the second end 33b of the second winding 33, and the second end 42b (positive connection end) of the second X capacitor 42 is connected to the second end 32b of the first winding 32, thereby creating negative coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42.
[0078] Please see Figure 11 This is a schematic diagram of the structural topology of the EMI filter in the eighth embodiment of this case. Compared to Figure 9 As shown in the figure, in this embodiment of the EMI filter 1g, the first end 41a (positive connection end) of the first X capacitor 41 and the first end 42a (negative connection end) of the second X capacitor 42 are located on opposite sides of the common mode inductor 3. The second end 41b (negative connection end) of the first X capacitor 41 and the second end 42b (positive connection end) of the second X capacitor 42 are located on opposite sides of the common mode inductor 3. The first end 41a (positive connection end) of the first X capacitor 41 is connected to the first end 32a of the first winding 32, the second end 41b (negative connection end) of the first X capacitor 41 is connected to the first end 33a of the second winding 33, the first end 42a (negative connection end) of the second X capacitor 42 is connected to the second end 33b of the second winding 33, and the second end 42b (positive connection end) of the second X capacitor 42 is connected to the second end 32b of the first winding 32, so that there is negative coupling between the parasitic inductance of the first X capacitor 41 and the parasitic inductance of the second X capacitor 42.
[0079] In summary, the first X capacitor of the EMI filter in this case is tilted at a first angle relative to the axis of the common-mode inductor, and / or the second X capacitor is tilted at a second angle relative to the axis of the common-mode inductor. This results in negative coupling between the parasitic inductance of the first X capacitor and the parasitic inductance of the second X capacitor, generating mutual inductance. This improves the overall performance of the EMI filter to achieve optimal performance. The EMI filter in this case does not require additional components and can simultaneously reduce mutual inductance to improve overall performance, thereby reducing the difficulty of simulation modeling.
Claims
1. An EMI filter, comprising: A circuit board; A common-mode inductor is mounted on this circuit board; A first capacitor X is disposed on the circuit board and located on a first side of an axis of the common-mode inductor; and A second X capacitor is disposed on the circuit board and located on the second side of the common mode inductor along the axial direction, the second side being disposed opposite to the first side; in, The first X capacitor is tilted at a first angle relative to the axis of the common mode inductor, and / or the second X capacitor is tilted at a second angle relative to the axis of the common mode inductor.
2. The EMI filter of claim 1, wherein the first X capacitor is tilted at a relative angle relative to the second X capacitor.
3. The EMI filter as claimed in claim 2, wherein the relative angle is 90 degrees.
4. The EMI filter of claim 1, wherein the shortest distance between a first terminal of the first X capacitor and the common-mode inductor is different from the shortest distance between a second terminal of the first X capacitor and the common-mode inductor, and / or the shortest distance between a first terminal of the second X capacitor and the common-mode inductor is different from the shortest distance between a second terminal of the second X capacitor and the common-mode inductor.
5. The EMI filter of claim 1, wherein the first X capacitor includes a first end and a second end disposed opposite to each other, the first X capacitor being tilted relative to the axis of the common mode inductor at a first angle with the first end or the second end approaching the common mode inductor, the first angle ranging from 0 degrees to 90 degrees; and / or the second X capacitor includes a first end and a second end disposed opposite to each other, the second X capacitor being tilted relative to the axis of the common mode inductor at a second angle with the first end or the second end approaching the common mode inductor, the second angle ranging from 0 degrees to 90 degrees.
6. The EMI filter as claimed in claim 5, wherein the first X capacitor is parallel to the second X capacitor.
7. The EMI filter as claimed in claim 1, wherein the EMI filter further comprises two first Y capacitors and two second Y capacitors, the two first Y capacitors being disposed on the circuit board and respectively located on opposite sides of the first X capacitor, and the two second Y capacitors being disposed on the circuit board and respectively located on opposite sides of the second X capacitor.
8. The EMI filter of claim 7, wherein one of the two first Y capacitors is located between the common-mode inductor and the first X capacitor, and one of the two second Y capacitors is located between the common-mode inductor and the second X capacitor.
9. The EMI filter as claimed in claim 7, wherein the connection between the two first Y capacitors is perpendicular to the installation direction of the first X capacitor; and / or the connection between the two second Y capacitors is perpendicular to the installation direction of the second X capacitor.
10. The EMI filter of claim 1, wherein the EMI filter further comprises two first Y capacitors and two second Y capacitors, the two first Y capacitors being located on the same side of the first X capacitor, and the first X capacitor being located between the two first Y capacitors and the common-mode inductor; and / or the two second Y capacitors being located on the same side of the second X capacitor, and the second X capacitor being located between the two second Y capacitors and the common-mode inductor.
11. The EMI filter of claim 1, wherein the positive connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor, and the negative connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor, wherein the common-mode inductor includes a magnetic core, a first winding and a second winding, wherein the first winding and the second winding are wound on the magnetic core, the two ends of the first winding are respectively connected to the positive connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor, and the two ends of the second winding are respectively connected to the negative connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor.
12. The EMI filter of claim 1, wherein the positive connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor, and the negative connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor are located on opposite sides of the common-mode inductor, wherein the common-mode inductor includes a magnetic core, a first winding and a second winding, wherein the first winding and the second winding are wound on the magnetic core, the two ends of the first winding are respectively connected to the positive connection terminal of the first X capacitor and the positive connection terminal of the second X capacitor, and the two ends of the second winding are respectively connected to the negative connection terminal of the first X capacitor and the negative connection terminal of the second X capacitor.
13. The EMI filter of claim 11 or 12, wherein the first winding and the second winding are respectively wound on opposite sides of the common-mode inductor passing through the axial direction, or respectively wound on opposite sides of the common-mode inductor along the axial direction.