Filter circuit and filter

Abstract

The invention discloses a filter circuit and a filter. The filter circuit comprises a first filter module, a common mode inductor and a second filter module; the first filtering module, the common mode inductor and the second filtering module are connected in sequence and are connected between the input and the output of the filtering circuit; at least one of the first filtering module and the second filtering module includes an attenuation element and a capacitor connected in series. According to the technical scheme provided by the embodiment of the invention, the resistor and the inductor in the equivalent circuit structure of the attenuation element can form a new LC filtering structure and a new RC filtering structure with the capacitor in the first filtering module or the capacitor in the second filtering module respectively; and a plurality of different cut-off frequencies are additionally generated at different frequency points, so that conducted interference and radiated interference are weakened, and the filtering effect of the filter circuit is improved.

Description

Technical Field

[0001] The present invention relates to the field of filtering technology, and in particular to a filtering circuit and a filter. Background Art

[0002] At present, many power supplies and power generation equipment have relatively high switching frequencies, ranging from several thousand Hz to several hundred kHz. With the increase in electrical equipment, almost all countries have mandatory electromagnetic interference requirements for equipment connected to the power grid. There are two types of electromagnetic interference: conducted interference and radiated interference. Conducted interference is mainly caused by interference signals generated by electronic equipment interfering with each other through conductive media or public power lines, and its test frequency is about 150K-30MHZ; radiated interference refers to the interference signal generated by electronic equipment being transmitted to another electrical network or electronic equipment through spatial coupling. Existing power supply equipment usually uses filters to filter electromagnetic interference, and its test frequency is about 30M-1GHZ, but the existing filters have poor overall filtering effect on electromagnetic interference and cannot take into account both conducted interference and radiated interference. Summary of the invention

[0003] The present invention provides a filtering circuit and a filter to improve the filtering effect of the filtering circuit and take into account the filtering effects of conducted interference and radiated interference.

[0004] According to one aspect of the present invention, there is provided a filtering circuit, comprising: a first filtering module, a common mode inductor, and a second filtering module;

[0005] The first filter module, the common mode inductor, and the second filter module are connected in sequence and connected between the input and output of the filter circuit; at least one of the first filter module and the second filter module includes an attenuation element and a capacitor connected in series.

[0006] Optionally, the first filtering module includes a first filtering unit and a second filtering unit, the first filtering unit and the second filtering unit are connected in parallel, and the first filtering unit and the second filtering unit both include an attenuation element and a capacitor connected in series.

[0007] Optionally, the first filtering unit includes a first magnetic bead and a first capacitor, and the second filtering unit includes a second magnetic bead, a second capacitor and a third capacitor;

[0008] The first magnetic bead is connected in series with the first capacitor, the second capacitor is connected in series with the third capacitor, one end of the second magnetic bead is connected to a node between the second capacitor and the third capacitor, and the other end of the second magnetic bead is grounded.

[0009] Optionally, the second filtering module includes a third filtering unit and a fourth filtering unit, the third filtering unit and the fourth filtering unit are connected in parallel, and the third filtering unit and the fourth filtering unit both include an attenuation element and a capacitor connected in series.

[0010] Optionally, the third filtering unit includes a third magnetic bead and a fourth capacitor, and the fourth filtering unit includes a fourth magnetic bead, a fifth capacitor and a sixth capacitor;

[0011] The third magnetic bead and the fourth capacitor are connected in series, the fifth capacitor and the sixth capacitor are connected in series, one end of the fourth magnetic bead is connected to the node between the fifth capacitor and the sixth capacitor, and the other end of the fourth magnetic bead is grounded.

[0012] Optionally, the first magnetic bead, the second magnetic bead, the third magnetic bead and the fourth magnetic bead are resistive-inductive elements.

[0013] Optionally, the impedance values ​​of the first magnetic beads, the second magnetic beads, the third magnetic beads and the fourth magnetic beads are adjustable.

[0014] Optionally, the capacitance values ​​of the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor are adjustable.

[0015] Optionally, the common mode inductor is detachably connected.

[0016] According to another aspect of the present invention, a filter is provided, comprising the filter circuit described in any embodiment of the present invention.

[0017] The technical solution provided by the embodiment of the present invention connects the first filter module, the common-mode inductor and the second filter module in series between the input and output of the filter circuit in sequence to form a π-type filter circuit. The common-mode inductor can respectively form an LC filter structure with the capacitor in the first filter module or the second filter module, so that the filter circuit generates multiple cut-off frequencies and filters out the conducted interference and radiated interference at the input and output ends of the filter circuit. The resistor and inductor in the equivalent circuit structure of the attenuation element can respectively form a new LC filter structure and RC filter structure with the capacitor in the first filter module or the second filter module, without affecting the original filtering effect. On the basis of generating multiple different cut-off frequencies at different frequency points, the conducted interference and radiated interference are weakened, and the overall filtering effect of the filter circuit is improved.

[0018] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a structural schematic diagram of a filter circuit in the related art;

[0021] Figure 2 A schematic diagram of the structure of a filter circuit provided according to an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of the structure of another filter circuit provided according to an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the structure of another filter circuit provided according to an embodiment of the present invention;

[0024] Figure 5 The figure is a schematic diagram of the structure of another filter circuit provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of 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 should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] Figure 1 This is a schematic diagram of the structure of a filter circuit in the related art. Figure 1The inventors have found that the existing filter circuit has the following problems in the filtering process: during the conduction test, the values ​​of capacitor Cx, capacitor Cy and inductor L0 are adjusted according to the test conduction result and frequency point to change the cutoff frequency of the filter circuit. The change of the cutoff frequency will make the filter circuit's filtering effect on radiation interference worse while improving the filter circuit's filtering effect on conducted interference; and the cutoff frequency of the filter circuit is changed by adjusting the values ​​of capacitor Cx, capacitor Cy and inductor L0 according to the test radiation result and frequency point. The change of the cutoff frequency will make the filter circuit's filtering effect on conducted interference worse while improving the filter circuit's filtering effect on radiation interference, and the filtering requirements cannot be met. Adjusting the values ​​of capacitor Cx, capacitor Cy and inductor L0 will theoretically change the cutoff frequency, thus affecting the frequency of conducted interference or radiated interference. When the adjustment is difficult to affect some frequencies, it may be that the high-frequency signal bypasses the filter through the ground signal, and the interference of the input part goes directly to the ground, and is transmitted back to the output port through the capacitor Cy of the input port or the capacitor Cy of the output port. When returning to the output port through the capacitor Cy of the output end, the inductor L0 will also be bypassed. Therefore, it is difficult to weaken the conducted interference and radiated interference at certain frequencies by adjusting the values ​​of capacitor Cx, capacitor Cy and inductor L0, and the filtering requirements cannot be met. In addition, during the conduction test, the signal interference output at both ends of capacitor Cx differs greatly. By increasing the capacitance value of capacitor Cx, the difference in the output signal interference at both ends of capacitor Cx can be reduced to make it close to the same, but it will make the output signals at both ends of capacitor Cx worse, and reduce the filtering effect at both ends of capacitor Cx as a whole.

[0028] Based on the above problems, the present invention provides a filter circuit. Figure 2 FIG. 1 is a schematic diagram of a filter circuit according to an embodiment of the present invention. Figure 2 The filter circuit includes: a first filter module 100, a common-mode inductor L, and a second filter module 200; the first filter module 100, the common-mode inductor L, and the second filter module 200 are connected in sequence and connected between the input and output of the filter circuit; at least one of the first filter module 100 and the second filter module 200 includes an attenuation element 300 and a capacitor C connected in series.

[0029] Specifically, the first filter module 100, the common mode inductor L and the second filter module 200 are sequentially connected in series between the input and output of the filter circuit to form a π-type filter circuit. The π-type filter circuit can filter out the conducted interference and radiated interference of the signal between the input and output of the filter circuit. The attenuation element 300 and the capacitor C connected in series included in the first filter module 100 and the second filter module 200 can be connected in a variety of ways. For example, Figure 1As shown, the connection mode of the attenuation element 300 and the capacitor C can be a mode in which a capacitor C is connected in series with an attenuation element 300. In other embodiments, the connection mode of the attenuation element 300 and the capacitor C can also be a connection mode in which two capacitors C are connected in series, one end of the attenuation element 300 is connected to the node between the two capacitors C, and the other end of the attenuation element 300 is grounded. The connection mode of the attenuation element 300 and the capacitor C can also be a combination of the above two connection modes. The common mode inductor L can be a common mode choke. The common mode inductor L can respectively form an LC filter structure with the capacitor C in the first filter module 100 or the second filter module 200, so that the filter circuit generates multiple cut-off frequencies, and the cut-off frequency is the frequency at which a certain frequency signal begins to be attenuated. The cut-off frequency f can be calculated by the formula f=1 / (2*π*√LC), where L is the common mode inductance value and C is the capacitance value. The attenuation element 300 has a resistance-inductance characteristic, and its equivalent circuit can be a series structure of a resistor and an inductor. The resistor and inductor in the equivalent circuit structure of the attenuation element 300 can form a new LC filter structure and an RC filter structure with the capacitor C in the first filter module 100 or the second filter module 200, respectively, so as to generate multiple different cutoff frequencies at different frequency points without affecting the original filtering effect, thereby simultaneously improving the filtering effect of the filter circuit on the conducted interference and the radiated interference, and improving the overall filtering effect of the filter circuit. Figure 1 As shown, when the attenuation element 300 and the capacitor C are connected in series with one capacitor C and one attenuation element 300, the equivalent inductance and equivalent resistance in the equivalent circuit structure of any attenuation element 300 at the input end or the output end can form a new LC and RC filter structure with the capacitor C connected in series with the attenuation element 300, thereby filtering out the interference signal energy at the corresponding frequency point. When the signal is at a low frequency, the inductance value of the attenuation element 300 is small, which basically does not affect the filtering effect of the original π-type filter circuit on the conducted interference, and a new filtering frequency point can be added to the original filter circuit to simultaneously weaken the radiated interference. When the attenuation element 300 and the capacitor C are connected in series with two capacitors C, one end of the attenuation element 300 is connected to the node between the two capacitors C, and the other end of the attenuation element 300 is grounded, the equivalent inductance and equivalent resistance in the equivalent circuit structure of any attenuation element 300 at the input end or the output end can form a new LC and RC filter structure with the capacitor C connected to the attenuation element 300, thereby filtering out the interference signal energy at the corresponding frequency point. When the signal is at a low frequency, the inductance of the attenuation element 300 is small, which basically does not affect the cutoff frequency of the radiation of the original π-type filter circuit, and does not affect the original filtering effect. A new filtering frequency point can be added to the original filter circuit to simultaneously weaken the conducted interference and the radiated interference.

[0030] The technical solution provided by the embodiment of the present invention connects the first filter module, the common-mode inductor and the second filter module in series between the input and output of the filter circuit to form a π-type filter circuit. The common-mode inductor can form an LC filter structure with the capacitor in the first filter module or the second filter module, respectively, so that the filter circuit generates multiple cut-off frequencies and filters out the conducted interference and radiated interference at the input and output ends of the filter circuit. The resistor and inductor in the equivalent circuit structure of the attenuation element can form a new LC filter structure and RC filter structure with the capacitor in the first filter module or the second filter module, respectively, without affecting the original filtering effect, and additionally generate multiple different cut-off frequencies at different frequency points, weakening the conducted interference and radiated interference, and improving the overall filtering effect of the filter circuit.

[0031] Optionally, Figure 3 FIG. 1 is a schematic diagram of a structure of another filter circuit provided according to an embodiment of the present invention. Figure 3 The first filtering module 100 includes a first filtering unit 110 and a second filtering unit 120 , which are connected in parallel. The first filtering unit 110 and the second filtering unit 120 both include an attenuation element 300 and a capacitor C connected in series.

[0032] Specifically, in one embodiment, the first filter unit 110 can be configured as a capacitor Cx1 connected in series with an attenuation element 300, and the second filter unit 120 can be configured as two capacitors Cy1 and Cy2 connected in series with an attenuation element 300. One end of the attenuation element 300 provided in the second filter unit 120 is connected to the node between the capacitor Cy1 and the capacitor Cy2, and the other end of the attenuation element 300 is grounded. The capacitor Cx1 can be used to perform differential mode filtering on the signal at the input end. The new LC filter structure and RC filter structure formed by the series connection of the attenuation element 300 and the capacitor Cx1 can improve the effect of differential mode filtering, make the signals passing through the two ends of the first filter unit 110 close to each other and reduce the signal amplitude, thereby improving the filtering effect on the conducted interference. Capacitor Cy1 and capacitor Cy2 can be used to perform common-mode filtering on the signal at the input end. One end of the attenuation element 300 is connected to the node between capacitor Cy1 and capacitor Cy2, and the other end of the attenuation element 300 is grounded, so that capacitor Cy1 and capacitor Cy2 can form a new LC filter structure and RC filter structure with the attenuation element 300, which can improve the effect of common-mode filtering, bypass the interference signal passing through the second filter unit 120 to the ground, thereby improving the filtering effect of radiation interference. In addition, for traditional filter circuits, electrical components are usually set in the LC main loop of the LC filter circuit to improve the filtering effect of the filter circuit. Compared with the traditional LC filter circuit, the technical solution provided by the embodiment of the present invention is to set the attenuation element 300 on the branch where the capacitor Cx1 is located or the branch composed of capacitor Cy1 and capacitor Cy2. When the attenuation element 300 is set on the branch of capacitor Cx1, the differential mode filtering effect of the capacitor Cx1 branch can be improved; when the attenuation element 300 is set on the branch composed of capacitors Cy1 and Cy2, the differential mode filtering effect of the branch composed of capacitors Cy1 and Cy2 can be improved.

[0033] Optionally, Figure 4 FIG. 1 is a schematic diagram of a structure of another filter circuit provided according to an embodiment of the present invention. Figure 3 and Figure 4 The first filtering unit 110 includes a first magnetic bead FB1 and a first capacitor C1, and the second filtering unit 120 includes a second magnetic bead FB2, a second capacitor C2 and a third capacitor C3; the first magnetic bead FB1 is connected in series with the first capacitor C1, the second capacitor C2 is connected in series with the third capacitor C3, one end of the second magnetic bead FB2 is connected to the node between the second capacitor C2 and the third capacitor C3, and the other end of the second magnetic bead FB2 is grounded.

[0034] Specifically, the attenuation element 300 can be a magnetic bead, which can have a high resistivity and magnetic permeability, and can be equivalent to a series structure of an inductor and a resistor, and the inductance value and the resistance value can change with the frequency. Compared with ordinary inductors, magnetic beads have better high-frequency filtering characteristics, and are resistive at high frequencies, so they can maintain a high impedance in a fairly wide frequency range, thereby improving the frequency modulation filtering effect. Magnetic beads can be used to eliminate high-frequency noise existing in transmission line circuits. High-frequency energy is an AC sinusoidal wave component superimposed on a DC transmission level. The DC component is a useful signal required, while the radio frequency energy is useless, and electromagnetic interference is transmitted and radiated along the line. To eliminate these unwanted signal energies, magnetic beads can be used to play the role of high-frequency resistors. The magnetic beads allow DC signals to pass through and filter out AC signals. The high-frequency signal can be a signal with a frequency of more than 30MHz. The magnetic bead type can be a chip magnetic bead. By arranging different magnetic beads at different positions of the filter circuit, the corresponding technical problems in the related art can be solved. The first magnetic bead FB1 and the second magnetic bead FB2 can be resistive-inductive elements. In the first filtering unit 110, the first magnetic bead FB1 is connected in series with the first capacitor C1, and the equivalent resistance and inductance of the first magnetic bead FB1 can form an RC filtering structure and an LC filtering structure with the first capacitor C1, respectively, so as to filter out and weaken the interference signal energy of the corresponding frequency point. When the signal is at a low frequency, the inductance of the first magnetic bead FB1 is small, which basically does not affect the filtering effect of the original π-type filter circuit on the conducted interference. A new filtering frequency point can be added to the original filter circuit to simultaneously weaken the radiated interference. The equivalent resistance of the first magnetic bead FB1 and the first capacitor C1 can form an RC filtering structure, forming a new cutoff frequency point on the high-frequency side, and dissipating the high-frequency interference signal through the first magnetic bead FB1 in the form of heat. The new cutoff frequency f can be obtained by the formula f=1 / (2*π*√RC), where R is the equivalent resistance value of the first magnetic bead FB1, and C is the capacitance value of the first capacitor C1. At the same time, the equivalent inductance of the first magnetic bead FB1 and the first capacitor C1 can form a new LC filtering structure. The equivalent inductance value of the first magnetic bead FB1 is much smaller than the inductance value of the common mode inductor L, thereby forming a new cutoff frequency point on the low-frequency side. On the basis of not affecting the original conducted interference filtering effect, the filtering effect on the radiated interference is simultaneously improved.

[0035] In the second filtering unit 120, the inductance equivalent to the second magnetic bead FB2 can form a new LC filter structure with the second capacitor C2 and the third capacitor C3 respectively, so that the interference signal energy of the corresponding frequency point can be filtered out. When the signal is at low frequency, the inductance value of the second magnetic bead FB2 is small, which does not affect the cut-off frequency of the radiation of the original π-type filter circuit substantially, does not affect the original filtering effect, and can add a new filtering frequency point to the original filtering circuit, and synchronously weaken the conducted interference and the radiated interference. At the same time, the second magnetic bead FB2 is connected in series between the second capacitor C2 and the third capacitor C3 and the ground, and the inductance characteristics of the magnetic bead can be used to hinder some frequencies, greatly weakening the energy of some frequencies. After adjustment, the interference signal at the output end during conduction and testing will not be affected by the pollution of the input part, avoiding the filter circuit from being bypassed, and playing a filtering role. And the grounding points of the input part of the filter circuit are more, so the improvement of the filtering effect by arranging the magnetic bead at the port of the π-type filter circuit will be better and the cost is lower. The equivalent resistance of the second magnetic bead FB2 can form an RC filter structure with the second capacitor C2 and the third capacitor C3 respectively, forming a new cutoff frequency point on the high-frequency side, and one end of the second magnetic bead FB2 is grounded, which can simultaneously improve the filtering effect of radiated interference and conducted interference. The new filtering structure formed by the equivalent inductance and equivalent resistance of the first magnetic bead FB1 and the second magnetic bead FB2 and the capacitors on their respective branches can enable the filter circuit to generate multiple cutoff frequency points. Compared with changing the cutoff frequency of the filter circuit by adjusting the capacitance value and the common-mode inductance value, setting the cutoff frequency points added by the first magnetic bead FB1 and the second magnetic bead FB2 can cover a wider frequency range, thereby improving the filtering effect.

[0036] Optionally, Figure 5 FIG. 1 is a schematic diagram of a structure of another filter circuit provided according to an embodiment of the present invention. Figure 5 The second filtering module 200 includes a third filtering unit 210 and a fourth filtering unit 220, which are connected in parallel. The third filtering unit 210 and the fourth filtering unit 220 both include an attenuation element 300 and a capacitor C which are connected in series.

[0037] Specifically, in one embodiment, the third filter unit 210 can be configured as a capacitor Cx2 connected in series with an attenuation element 300, and the fourth filter unit 220 can be configured as two capacitors Cy3 and Cy4 connected in series with an attenuation element 300. One end of the attenuation element 300 provided in the fourth filter unit 220 is connected to the node between the capacitor Cy3 and the capacitor Cy4, and the other end of the attenuation element 300 is grounded. The capacitor Cx2 can be used to perform differential mode filtering on the signal at the input end, and the new LC filter structure and RC filter structure formed by the series connection of the attenuation element 300 and the capacitor Cx2 can improve the effect of differential mode filtering, make the signals passing through the two ends of the third filter unit 210 close to each other and reduce the signal amplitude, thereby improving the filtering effect on the conducted interference. Capacitor Cy3 and capacitor Cy4 can be used to perform common-mode filtering on the signal at the output end. One end of the attenuation element 300 is connected to the node between capacitor Cy3 and capacitor Cy4, and the other end of the attenuation element 300 is grounded, so that capacitor Cy3 and capacitor Cy4 can form a new LC filter structure and RC filter structure with the attenuation element 300 to improve the effect of common-mode filtering, so that the interference signal passing through the fourth filter unit 220 is bypassed to the ground, thereby improving the filtering effect of radiation interference. The attenuation element 300 of the third filter unit 210 and the attenuation element 300 of the fourth filter unit 220 can effectively prevent the output end of the filter circuit from being affected by the interference signal of the grounded input end, and prevent the π-type filter circuit from being bypassed.

[0038] Optionally, based on the above embodiment, continue to refer to Figure 4 and Figure 5 The third filtering unit 210 includes a third magnetic bead FB3 and a fourth capacitor C4, and the fourth filtering unit 220 includes a fourth magnetic bead FB4, a fifth capacitor C5, and a sixth capacitor C6; the third magnetic bead FB3 and the fourth capacitor C4 are connected in series, the fifth capacitor C5 and the sixth capacitor C6 are connected in series, one end of the fourth magnetic bead FB4 is connected to the node between the fifth capacitor C5 and the sixth capacitor C6, and the other end of the fourth magnetic bead FB4 is grounded.

[0039] Specifically, the third magnetic bead FB3 and the fourth magnetic bead FB4 can be resistive-inductive elements. In the third filtering unit 210, the third magnetic bead FB3 is connected in series with the fourth capacitor C4, and the equivalent resistance and inductance of the third magnetic bead FB3 can form an RC filtering structure and an LC filtering structure with the fourth capacitor C4, respectively, so as to filter out and weaken the interference signal energy of the corresponding frequency point. When the signal is low-frequency, the inductance value of the third magnetic bead FB3 is small, which basically does not affect the filtering effect of the original π-type filter circuit on the conducted interference. A new filtering frequency point can be added to the original filter circuit to simultaneously weaken the radiated interference. The equivalent resistance of the third magnetic bead FB3 and the fourth capacitor C4 can form an RC filtering structure, forming a new cutoff frequency point on the high-frequency side, and dissipating the high-frequency interference signal through the third magnetic bead FB3 in the form of heat. At the same time, the equivalent inductance of the third magnetic bead FB3 and the fourth capacitor C4 can form a new LC filtering structure. The equivalent inductance value of the third magnetic bead FB3 is much smaller than the inductance value of the common mode inductor L, thereby forming a new cutoff frequency point on the low-frequency side. Without affecting the original conducted interference filtering effect, the filtering effect of the output end on the radiated interference is simultaneously improved.

[0040] In the fourth filtering unit 220, the inductance equivalent to the fourth magnetic bead FB4 can form a new LC filtering structure with the fifth capacitor C5 and the sixth capacitor C6 respectively, so that the interference signal energy of the corresponding frequency point can be filtered out. When the signal is at a low frequency, the inductance value of the fourth magnetic bead FB4 is small, which does not substantially affect the cut-off frequency of the radiation of the original π-type filter circuit, does not affect the original filtering effect, and can add a new filtering frequency point to the original filtering circuit to simultaneously weaken the conducted interference and the radiated interference. At the same time, the fourth magnetic bead FB4 is connected in series between the fifth capacitor C5 and the sixth capacitor C6 and the ground, and the inductance characteristics of the magnetic bead can be used to hinder some frequencies, greatly weakening the energy of some frequencies. After adjustment, the interference signal at the output end during conduction and testing will not be affected by the pollution of the input part, avoiding the filter circuit from being bypassed, and playing a filtering role. And there are many grounding points in the input part of the filter circuit, so the improvement of the filtering effect by arranging magnetic beads at the port of the π-type filter circuit will be better and less costly. The equivalent resistance of the fourth magnetic bead FB4 can form an RC filter structure with the fifth capacitor C5 and the sixth capacitor C6 respectively, forming a new cut-off frequency point on the high-frequency side, and one end of the fourth magnetic bead FB4 is grounded, which can simultaneously improve the filtering effect of the output end of the filter circuit on the radiated interference and the conducted interference. At the same time, the new filtering structure formed by the third magnetic bead FB3 and the fourth magnetic bead FB4 set at the output end of the filter circuit can effectively prevent the output end of the filter circuit from being affected by the interference signal of the grounded input end, prevent the first magnetic bead FB1, the second magnetic bead FB2 and the common mode inductor L set at the input end of the filter circuit from being bypassed, and avoid the first magnetic bead FB1 and the second magnetic bead FB2 set at the input end of the filter circuit from failing; the new filtering structure formed by the first magnetic bead FB1 and the second magnetic bead FB2 set at the input end of the filter circuit can also effectively prevent the input end of the filter circuit from being affected by the interference signal of the grounded output end, prevent the third magnetic bead FB3, the fourth magnetic bead FB4 and the common mode inductor L set at the output end of the filter circuit from being bypassed, and avoid the third magnetic bead FB3 and the fourth magnetic bead FB4 set at the output end of the filter circuit from failing. Therefore, the technical solution provided by the embodiment of the present invention, the third magnetic bead FB3 and the fourth magnetic bead FB4 set at the output end of the π-type filter circuit can synergistically influence each other with the first magnetic bead FB1 and the second magnetic bead FB2 set at the input end to ensure the stability of the filtering effect between each other, thereby improving the filtering effect of the filter circuit.

[0041] Optionally, based on the above embodiment, continue to refer to Figure 4 The impedance values ​​of the first magnetic bead FB1, the second magnetic bead FB2, the third magnetic bead FB3 and the fourth magnetic bead FB4 are adjustable.

[0042] Specifically, the first magnetic bead FB1, the second magnetic bead FB2, the third magnetic bead FB3 and the fourth magnetic bead FB4 are small in size, and the impedance value can be easily adjusted. The first magnetic bead FB1, the second magnetic bead FB2, the third magnetic bead FB3 and the fourth magnetic bead FB4 can be set in a setting mode in which the impedance at the corresponding frequency point is inconsistent. In this way, the cutoff frequency formed by the new RC filter structure formed by the magnetic beads and the capacitor and the new LC filter structure can be adjusted, thereby improving the filtering effect of the filter circuit on signals in different frequency bands.

[0043] Optionally, based on the above embodiment, continue to refer to Figure 4 The capacitance values ​​of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5 and the sixth capacitor C6 are adjustable.

[0044] Specifically, the capacitance values ​​of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5 and the sixth capacitor C6 can be appropriately adjusted, so that the cut-off frequency formed by the new RC filter structure and the new LC filter structure formed by adjusting the first magnetic bead FB1, the second magnetic bead FB2, the third magnetic bead FB3 and the fourth magnetic bead FB4 can be coordinated, so that the filter circuit can cover more cut-off frequencies. Appropriately adjusting the capacitance values ​​of the first capacitor C1 and the fourth capacitor C4 can also play the effect of adjusting the differential mode filtering, and on the basis of reducing the difference in the output signal interference at both ends of the first capacitor C1 and the difference in the output signal interference at both ends of the fourth capacitor C4, the overall filtering effect at both ends of the first capacitor C1 and the fourth capacitor C4 is guaranteed.

[0045] Optionally, based on the above embodiment, continue to refer to Figure 4 and Figure 5 The common mode inductor L can be detachably connected.

[0046] Specifically, one end of the common-mode inductor L can be connected to the first filter unit 110, and the other end of the common-mode inductor L is connected to the third filter unit 210. Most of the current of the input signal needs to pass through the common-mode inductor L, and its wire diameter is large and the adjustable range of the inductance value is small. Setting the common-mode inductor L to be detachable allows the common-mode inductor L to be replaced, thereby increasing the adjustment range of the inductance value of the common-mode inductor L, so that the cutoff frequency of the filter circuit can cover a wider frequency range, and further improving the filtering effect of the filter circuit on signals in different frequency bands.

[0047] An embodiment of the present invention further provides a filter, which includes the filter circuit provided by any embodiment of the present invention and has the same beneficial effects as the filter circuit provided by any of the above embodiments, which will not be elaborated here.

[0048] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0049] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A filter circuit, characterized in that: include: A first filtering module, a common mode inductor, and a second filtering module; The first filter module, the common mode inductor, and the second filter module are connected in sequence and connected between the input and output of the filter circuit; at least one of the first filter module and the second filter module includes an attenuation element and a capacitor connected in series.

2. The filter circuit according to claim 1, characterized in that: The first filtering module includes a first filtering unit and a second filtering unit, the first filtering unit and the second filtering unit are connected in parallel, and the first filtering unit and the second filtering unit each include an attenuation element and a capacitor connected in series.

3. The filter circuit according to claim 2, characterized in that: The first filtering unit includes a first magnetic bead and a first capacitor, and the second filtering unit includes a second magnetic bead, a second capacitor and a third capacitor; The first magnetic bead is connected in series with the first capacitor, the second capacitor is connected in series with the third capacitor, one end of the second magnetic bead is connected to a node between the second capacitor and the third capacitor, and the other end of the second magnetic bead is grounded.

4. The filter circuit according to claim 3, characterized in that: The second filtering module includes a third filtering unit and a fourth filtering unit, the third filtering unit and the fourth filtering unit are connected in parallel, and the third filtering unit and the fourth filtering unit each include an attenuation element and a capacitor connected in series.

5. The filter circuit according to claim 4, characterized in that: The third filtering unit includes a third magnetic bead and a fourth capacitor, and the fourth filtering unit includes a fourth magnetic bead, a fifth capacitor and a sixth capacitor; The third magnetic bead and the fourth capacitor are connected in series, the fifth capacitor and the sixth capacitor are connected in series, one end of the fourth magnetic bead is connected to the node between the fifth capacitor and the sixth capacitor, and the other end of the fourth magnetic bead is grounded.

6. The filter circuit according to claim 5, characterized in that: The first magnetic bead, the second magnetic bead, the third magnetic bead and the fourth magnetic bead are resistive-inductive elements.

7. The filter circuit according to claim 6, characterized in that: The impedance values ​​of the first magnetic beads, the second magnetic beads, the third magnetic beads and the fourth magnetic beads are adjustable.

8. The filter circuit according to claim 5, characterized in that: The capacitance values ​​of the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor and the sixth capacitor are adjustable.

9. The filter circuit according to claim 1, characterized in that: The common mode inductor is detachably connected.

10. A filter, characterized in that: The filter circuit comprises the filter circuit described in any one of claims 1 to 9.

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