Filter circuit

Abstract

A filter circuit is used for improving the filtering effect of the filter circuit. The filter circuit comprises an LC resonance branch, at least one filter branch and first inductors in one-to-one correspondence with the filter branches. Each filtering branch is connected with the LC resonance branch through the corresponding first inductor, and the single filtering branch is connected with the input end of the filtering circuit or the output end of the filtering circuit. By adopting the above design, the first inductor connected between the LC resonance branch and the filtering branch enables the LC resonance branch and the filtering branch not to present a parallel relation, thereby avoiding parallel resonance of the filtering circuit, and improving the filtering effect of the filtering circuit.

Description

Technical Field

[0001] This application relates to the field of power electronics, and particularly to a filtering circuit. Background Art

[0002] In the fields of electronic signal processing and power supply, filters have always played a very important role. A filter is a device used to eliminate interference. By effectively filtering out specific frequency points or frequencies outside that frequency point through the filter, interference signals can be eliminated to ensure the quality of the signal or the power supply quality.

[0003] Currently, a trap filter is generally connected in parallel at the input end or the output end of the filter. The resonant frequency of the trap filter and the filtering frequency of the filter form a filtering interval, and the interference signals in the received signal within the above filtering interval are filtered out, so as to achieve the purpose of eliminating interference signals. In actual application, the filter may generate parallel resonance with the parallel-connected trap filter. During the above parallel resonance, it will affect the filtering effect of the device on interference signals, resulting in some signals that cannot be eliminated. Summary of the Invention

[0004] This application provides a filtering circuit for improving the filtering effect of the filtering circuit.

[0005] The specific technical solutions provided by the embodiments of this application are as follows:

[0006] The embodiments of this application provide a filtering circuit, which can be applied to an AC power supply scenario or a communication field and is used to filter interference signals on a power supply line or a signal transmission line. Among them, the filtering circuit includes an LC resonance branch, at least one filtering branch, and a first inductor corresponding to each filtering branch; each filtering branch is connected to the LC resonance branch through the corresponding first inductor, and a single filtering branch is connected to the input end of the filtering circuit or the output end of the filtering circuit. With the above design, the first inductor can isolate the LC resonance circuit and the filtering branch, so that the parallel resonance condition cannot be satisfied, thus effectively avoiding the situation where the circuit presents an open circuit state during parallel resonance and cannot filter out interference signals.

[0007] In a possible design, the LC resonance branch includes at least one second inductor and at least one first capacitor, and the at least one second inductor and the at least one first capacitor are connected in series. The series-connected inductor and capacitor can form a series resonance circuit and filter signals with a frequency of the series resonance frequency passing through the above branch.

[0008] In a possible design, the middle node of the LC resonance branch is grounded, and at least one second inductor and at least one first capacitor are connected between the middle node and each port of the LC resonance branch. By adopting the above method, the interference signal to be filtered can be transmitted to the ground wire through the middle node, thereby increasing the filtering path of the filtered signal.

[0009] In a possible design, the LC resonance branch includes at least one sub-resonance branch, each filtering branch includes a sub-filtering branch corresponding to each sub-resonance branch, each first inductor includes a first sub-inductor corresponding to each sub-filtering branch in the connected filtering branch, each sub-filtering branch is connected to the corresponding sub-resonance branch through the corresponding first sub-inductor, and the number of the sub-resonance branches is the same as the number of phase lines in the power supply connected to the input end of the filtering circuit. By adopting the above design, at least two filtering paths can be configured on each phase line in the connected power supply, and the above filtering paths can eliminate the interference signals transmitted on each connected phase line.

[0010] In a possible design, if the filtering circuit includes a first target filtering branch connected to the input end of the filtering circuit, the first end of each sub-filtering branch in the first target filtering branch is connected to a phase line in the power supply, the first end of each sub-filtering branch in the first target filtering branch is connected to one end of the corresponding sub-resonance branch through the corresponding first sub-inductor, and the second end of each sub-filtering branch in the first target filtering branch is connected to the second end of each sub-resonance branch, wherein the phase lines connected to the first ends of each sub-filtering branch in the first target filtering branch are different.

[0011] In a possible design, if the power supply connected to the filtering circuit includes a neutral line or a zero line, the second end of each sub-filtering branch in the first target filtering branch is connected to the neutral line or the zero line.

[0012] In a possible design, if the first inductor connected to the first target filtering branch is a common-mode inductor, the first inductor connected to the first target filtering branch further includes a second sub-inductor, one end of the second sub-inductor is connected to the neutral line and the second end of each sub-filtering branch in the first target filtering branch, and the other end of the second sub-inductor is connected to the second end of each sub-resonance branch, or one end of the second sub-inductor is connected to the zero line and the second end of each sub-filtering branch in the first target filtering branch, and the other end of the second sub-inductor is connected to the second end of each sub-resonance branch.

[0013] In a possible design, if the filtering circuit includes a second target filtering branch connected to the output end of the filtering circuit, the first end of each sub-filtering branch in the second target filtering branch is connected to an output port of the filtering circuit, the first end of each sub-filtering branch in the second target filtering branch is connected to one end of a corresponding sub-resonant branch through a corresponding first sub-inductor, and the second end of each sub-filtering branch in the second target filtering branch is connected to the second end of each sub-resonant branch, where the output ports connected to the first end of each sub-filtering branch in the second target filtering branch are different.

[0014] In a possible design, if the power supply connected to the filtering circuit includes a neutral line or a zero line, the second end of each sub-filtering branch in the second target filtering branch is connected to an output port of the filtering circuit, and the output port connected to the second end of each sub-filtering branch in the second target filtering branch is different from the output port connected to the first end of each sub-filtering branch in the second target filtering branch.

[0015] In a possible design, if the first inductor connected to the second target filtering branch is a common-mode inductor, the first inductor connected to the second target filtering branch further includes a second sub-inductor, one end of the second sub-inductor is connected to the second end of each sub-resonant branch, and the other end of the second sub-inductor is connected to the second end of each sub-filtering branch in the second target filtering branch. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic structural diagram of a filtering device provided by an embodiment of the present application;

[0018] Figure 2 is a schematic diagram of the filtering signal waveform of a filtering device provided by an embodiment of the present application;

[0019] Figure 3 is a schematic structural diagram of a filtering circuit provided by an embodiment of the present application Figure 1 ;

[0020] Figure 4 is a schematic structural diagram of a filtering circuit provided by an embodiment of the present application Figure 2 ;

[0021] Figure 5Structural schematic of a filtering circuit provided by an embodiment of the present application Figure 3 ;

[0022] Figure 6 Structural schematic of a filtering circuit provided by Embodiment 1 of the present application Figure 1 ;

[0023] Figure 7 Structural schematic of a filtering circuit provided by Embodiment 1 of the present application Figure 2 ;

[0024] Figure 8 Structural schematic of a filtering circuit provided by Embodiment 1 of the present application Figure 3 ;

[0025] Figure 9 Structural schematic of a filtering circuit provided by Embodiment 1 of the present application Figure 4 ;

[0026] Figure 10 Structural schematic of a filtering circuit provided by Embodiment 1 of the present application Figure 5 ;

[0027] Figure 11 Structural schematic of a filtering circuit provided by Embodiment 2 of the present application Figure 1 ;

[0028] Figure 12 Structural schematic of a filtering circuit provided by Embodiment 2 of the present application Figure 2 ;

[0029] Figure 13 Structural schematic of a filtering circuit provided by Embodiment 2 of the present application Figure 3 ;

[0030] Figure 14 Structural schematic of a filtering circuit provided by Embodiment 2 of the present application Figure 4 ;

[0031] Figure 15 Structural schematic of a filtering circuit provided by Embodiment 3 of the present application Figure 1 ;

[0032] Figure 16 Structural schematic of a filtering circuit provided by Embodiment 3 of the present application Figure 2 ;

[0033] Figure 17 Structural schematic of a filtering circuit provided by Embodiment 3 of the present application Figure 3 ;

[0034] Figure 18 Structural schematic of a filtering circuit provided by Embodiment 3 of the present applicationFigure 4 ;

[0035] Figure 19 This is a schematic diagram of the structure of a filter circuit provided in Embodiment 3 of the present application Figure 5 ;

[0036] Figure 20 This is a schematic diagram of the structure of a filter circuit provided in Embodiment 3 of the present application Figure 6 ;

[0037] Figure 21 This is a schematic diagram of the structure of a filter circuit provided in Embodiment 3 of the present application Figure 7 ;

[0038] Figure 22 This is a schematic diagram of the structure of a filter circuit provided in Embodiment 3 of the present application Figure 8 . Detailed implementation manners

[0039] Next, the embodiments of the present application will be described in detail with reference to the accompanying drawings

[0040] The terms used in the embodiments of the present application are only used to explain the specific embodiments of the present application, rather than to limit the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application

[0041] Hereinafter, some terms in the embodiments of the present application will be explained to facilitate the understanding of those skilled in the art

[0042] (1) The terms "first", "second", etc. in the embodiments of the present application are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here

[0043] (2) "Multiple" in the embodiments of the present application means two or more, and other quantifiers are similar

[0044] (3) "And / or" in the embodiments of the present application describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural

[0045] (4) The "connection" in the embodiments of the present application can be understood as electrical connection or communication connection. The electrical connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, when A is connected to B, it can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, when A is connected to B, it can also be a direct connection between A and C, and a direct connection between C and B, and the connection between A and B is realized through C. The communication connection between two electrical components is a wireless connection between the two electrical components, that is, an electromagnetic connection between the two electrical components.

[0046] The application scenarios of the technical solutions in the embodiments of the present application will be introduced below.

[0047] The solution provided by the embodiments of the present application can be applied to the power supply field or the communication field of signal transmission, and is used to meet the electromagnetic compatibility (EMC) requirements of devices. Taking the solution provided by the embodiments of the present application applied to the power supply field as an example, multiple switching devices are generally arranged in a switching power supply, and the supply voltage required by the backend connected device is output by controlling the on and off of the switching devices. However, the frequent on and off of the switching devices will generate harmonic signals of different frequencies. If these harmonic signals are transmitted to the backend connected load, it may affect the normal operation of the load, and in severe cases, it will cause load failure.

[0048] Currently, generally, a filtering device and a notch filter are used in combination to eliminate the above harmonic signals. Refer to Figure 1 As shown, it is a schematic structural diagram of a filtering device when configuring a filtering device and a notch filter. The inductor L1 and the capacitor C1 form a notch filter, and the filtering device is the filtering capacitor C2.

[0049] Among them, the inductor L1 and the capacitor C1 form an LC series resonance branch, and the resonance frequency of the LC series resonance branch is Therefore, when there are harmonic signals in the frequency range centered on f1 in the signal received by the filtering device, the LC series resonance branch presents a short-circuit state, and the signal is filtered out through the LC series resonance circuit. Therefore, the above signal cannot be transmitted to the backend connected load, and thus the interference of the above signal to the load can be eliminated.

[0050] Under normal circumstances, Figure 1The filtering device shown has frequency point 1 and frequency point 3. Frequency point 1 is the resonant frequency f1 of the above-mentioned LC series resonant branch, and frequency 2 is the center frequency corresponding to the filtering capacitor C2. The filtering device can filter out the harmonic signals of specific frequencies in the received signal based on the settings of the above two frequency points, thereby eliminating the influence of interference signals on the load. However, in actual use, there will be parasitic resistances on the LC series resonant branch, and there will be parasitic resistances and parasitic inductances on the branch where the filtering capacitor C2 is located. The above design method of the filtering device may cause the two branches corresponding to the LC series resonant branch and the filtering capacitor C2 to form a parallel resonant circuit. See Figure 2 As shown, the parallel resonant frequency corresponding to the parallel resonant circuit is frequency point 2. Since the circuit is in an open state when in parallel resonance, the harmonic signals in the harmonic interval corresponding to the center frequency of frequency point 2 in the input signal cannot be filtered out by the resonant circuit. Therefore, this signal will still be transmitted to the load connected to the back end of the filtering device and interfere with the operation of the load.

[0051] In view of this, the present application provides a filtering circuit for eliminating the generation of the parallel resonant circuit and improving the filtering effect of the filtering circuit.

[0052] The technical solution of the present application can be summarized as follows: A notch filter composed of an LC resonant branch and a filtering branch composed of a filtering capacitor or a filtering inductor are provided in the filtering circuit, and a first inductor is connected between the LC resonant branch and the filtering branch. At this time, even when the parameters of the parasitic inductances, capacitors, etc. on the filtering branch are the same on the two branches, the first inductor will isolate the two branches with filtering functions, so that the two branches with filtering functions cannot form a parallel resonant branch, thereby improving the filtering effect of the filtering circuit.

[0053] The filtering circuit provided by the embodiment of the present application can be connected to the power supply through the power supply line and can also be connected to the signal source through the signal transmission line. Among them, the power supply includes but is not limited to: single-phase AC power supply, two-phase AC power supply, and three-phase AC power supply. When the power supply is a three-phase AC power supply, according to the transmission mode of the three-phase AC power supply, the power supply line connected to the filtering circuit can be a three-phase three-wire transmission line provided with three phase lines, or a three-phase four-wire transmission line provided with three phase lines and a neutral line. It should be noted that the type of the power supply and the number of lines of the power supply line are only examples. In actual application, there can be other choices for the type of the power supply and the power supply line, and they are not listed one by one here in the present application.

[0054] In the filter circuit provided by the embodiments of the present application, the filter circuit at least includes an LC resonance branch 11, at least one filter branch 12, and a first inductor 13 corresponding to each filter branch 12 one by one. Each filter branch 12 is connected to the LC resonance branch 11 through the corresponding first inductor 13. Among them, each filter branch 12 may include a filter capacitor or a filter inductor with a filtering function, and the inductive reactance of the filter inductor or the capacitive reactance of the filter capacitor can be set according to the frequency of the interference signal to be eliminated. There is no need to introduce too much here in the present application.

[0055] In an example, if there is one filter branch 12 in the filter circuit and the filter branch 12 is connected to the input end of the filter circuit, the structural diagram of the filter circuit can be seen in Figure 3 as shown. If there is one filter branch 12 in the filter circuit and the filter branch 12 is connected to the output end of the filter circuit, the structural diagram of the filter circuit can be seen in Figure 4 as shown.

[0056] In another example, if there are two filter branches 12 in the filter circuit, the structural diagram of the filter circuit is as shown in Figure 5 as shown. See Figure 5 as shown. One of the filter branches 12 is connected to the input end of the filter circuit, and the other filter branch 12 is connected to the output end of the filter circuit. The above two filter branches 12 are both connected to the LC resonance branch 11 through a first inductor 13.

[0057] It should be understood that Figures 3 to 5 the structure of the filter circuit shown is only an example. In practical applications, the filter circuit may have more components than those shown in Figures 3 to 5 . For example, in addition to the above devices, the filter circuit may further include protection devices and voltage regulator devices. Among them, Figures 3 to 5 the various components shown can be implemented in hardware, software, or a combination of hardware and software including one or more signal processing and / or application specific integrated circuits.

[0058] In practical applications, the input end of the filter circuit can be connected to a power supply through a power supply line, and the output end of the filter circuit can be directly or through other devices connected to a load. The input end of the filter circuit can also be connected to a signal source through a signal transmission line, and the output end of the filter circuit can be directly or through other devices connected to a signal receiving device. Hereinafter, taking the input end of the filter circuit being connected to a power supply through a power supply line as an example, the working process of the filter circuit will be described.

[0059] Continue to refer to Figures 3 to 5As shown, each filtering branch 12 is connected to the LC resonance branch 11 through a first inductor 13. Therefore, the filtering branch 12 cannot be in a parallel relationship with the LC resonance branch 11. Correspondingly, the filtering branch 12 cannot form a parallel resonance circuit with the LC resonance branch 11, thereby eliminating the problem of poor filtering effect caused by parallel resonance and improving the filtering effect of the filtering circuit.

[0060] In the filtering circuit provided by the embodiment of the present application, the LC resonance branch 11 may include at least one second inductor and at least one first capacitor, and the at least one second inductor and the at least one first capacitor are connected in series. The values of the second inductor and the first capacitor can be set according to the amplitude of the device connected to the input end of the filtering circuit and the frequency of the interference signal to be eliminated. This application will not introduce too much here.

[0061] In one example, when the LC resonance branch 11 includes a plurality of second inductors and a plurality of first capacitors, the middle node of the LC resonance branch 11 is grounded, and at least one second inductor and at least one first capacitor are connected between the middle node and each port of the LC resonance branch 11. At this time, the LC resonance branch 11 can be connected to two phase lines and eliminate the interference signals on the connected phase lines respectively.

[0062] In actual use, according to the different devices connected to the input end and the output end of the filtering circuit, there may be multiple phase lines for transmitting electric energy or signals between the filtering circuit and the connected device, and each phase line has a need to eliminate interference signals. Therefore, when the input end of the filtering circuit is connected to a two-phase AC power supply or a three-phase AC power supply, the LC resonance branch 11 and each filtering branch 12 need to be configured with a filtering path for interference signals on multiple phase lines. For example, the LC resonance branch 11 may include at least one sub-resonance branch, each filtering branch 12 includes a sub-filtering branch corresponding to each sub-resonance branch, each first inductor 13 includes a first sub-inductor corresponding to each sub-filtering branch in the connected filtering branch, and each sub-filtering branch is connected to the corresponding sub-resonance branch through the corresponding first sub-inductor. Among them, the number of the sub-resonance branches is the same as the number of phase lines in the power supply connected to the input end of the filtering circuit. Each sub-resonance branch and the sub-filtering branch corresponding to the sub-resonance branch can filter the interference signals on one phase line.

[0063] Next, the structure of the filtering circuit in multiple different scenarios will be described in conjunction with embodiments.

[0064] Embodiment 1: The filtering circuit is connected to a single-phase AC power supply

[0065] The filter circuit includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. Among them, the first input terminal of the filter circuit is connected to the phase line of the single-phase AC power supply (i.e., the live wire of the single-phase AC power supply), the second input terminal of the filter circuit is connected to the neutral line of the single-phase AC power supply, the first output terminal of the filter circuit is connected to the first input terminal of the backend connection device, and the second output terminal of the filter circuit is connected to the second input terminal of the backend connection device.

[0066] In a possible implementation, as Figure 6 shown, it is a schematic structural diagram of a filter circuit provided in Embodiment 1 of the present application. The filter circuit includes a first target filter branch 12 connected to the input terminal of the filter circuit. Refer to Figure 6 shown, the LC resonance branch 11 includes a sub-resonance branch 111, the first target filter branch 12 includes a sub-filter branch 121, and the first inductor 13 includes a sub-inductor L11. Among them, the first end of the sub-resonance branch 111 is connected to the first end of the sub-filter branch 121 and the live wire of the single-phase AC power supply through a sub-inductor L11, and the second end of the sub-resonance branch 111 is connected to the second end of the sub-filter branch 121 and the neutral line of the single-phase AC power supply; the first end of the sub-resonance branch 111 is also connected to the first output terminal of the filter circuit, and the second end of the sub-resonance branch 111 is also connected to the second output terminal of the filter circuit.

[0067] It should be noted that Figure 6 in the filter circuit shown, each sub-resonance branch includes a capacitor C1 and an inductor L2, and each sub-filter circuit includes a filter capacitor C2. In actual application, the sub-resonance branch and the sub-filter branch may also include other devices, which are not limited too much here in the present application.

[0068] In a possible implementation, as Figure 7 shown, it is a schematic structural diagram of another filter circuit provided in Embodiment 1 of the present application. The filter circuit includes a second target filter branch 12 connected to the output terminal of the filter circuit. As Figure 7 shown, the LC resonance branch 11 includes a sub-resonance branch 111, the second target filter branch 12 includes a sub-filter branch 121, and the first inductor 13 includes a sub-inductor L11. Among them, the first end of the sub-resonance branch 111 is directly connected to the live wire of the single-phase AC power supply, and the second end of the sub-resonance branch 111 is connected to the neutral line of the single-phase AC power supply; the first end of the sub-resonance branch 111 is also used to be connected to the first end of the sub-filter branch 121 and the first output terminal of the filter circuit through a sub-inductor L11, and the second end of the sub-resonance branch 111 is also used to be connected to the second end of the sub-filter branch 121 and the second output terminal of the filter circuit.

[0069] In a possible implementation, asFigure 8 As shown in the figure, it is a schematic structural diagram of another filtering circuit provided by the first embodiment of the present application. The filtering circuit includes a first target filtering branch 12 connected to the input end of the filtering circuit and a second target filtering branch 12 connected to the output end of the filtering circuit. Refer to Figure 8 As shown in the figure, the LC resonance branch 11 includes a sub-resonance branch 111. Each of the two target filtering branches 12 includes a sub-filtering branch 121, and each first inductor 13 includes a sub-inductor L11. The first end of the sub-resonance branch 111 is connected to the first end of one of the sub-filtering branches 121 and the live wire of the single-phase AC power supply through a sub-inductor L11. The second end of the sub-resonance branch 111 is connected to the second end of one of the sub-filtering branches 121 and the neutral wire of the single-phase AC power supply; the first end of the sub-resonance branch 111 is connected to the first end of the other sub-filtering branch 121 and the first output end of the filtering circuit through another sub-inductor L11. The second end of the sub-resonance branch 111 is connected to the second end of the other sub-filtering branch 121 and the second output end of the filtering circuit.

[0070] In practical applications, the first inductor 13 can be a differential-mode inductor or other inductors commonly used in the industry. The first inductor can also be a common-mode inductor. Since the common-mode inductor is composed of two inductors connected in series on the same magnetic core, each first inductor includes, in addition to the above-mentioned sub-inductor L11, a sub-inductor L12. Taking the filtering circuit including two filtering branches as an example, refer to Figure 9 As shown in the figure, the first end of the sub-resonance branch 111 is connected to the first end of one of the sub-filtering branches 121 and the live wire of the single-phase AC power supply through a sub-inductor L11. The second end of the sub-resonance branch 111 is connected to the second end of one of the sub-filtering branches 121 and the neutral wire of the single-phase AC power supply through a second sub-inductor L12. The first end of the sub-resonance branch 111 is connected to the first output end of the other sub-filtering circuit 121 through a sub-inductor L11. The second end of the sub-resonance branch 111 is connected to the second end of the other sub-filtering branch 121 and the second output end of the filtering circuit through a second sub-inductor L12.

[0071] In practical applications, when a common-mode inductor is used as the first inductor, since the common-mode inductor has the advantages of small magnetic loss and leakage inductance, it is beneficial to avoid parallel resonance between the LC resonance branch and other filtering branches, thereby ensuring the filtering effect of the filtering circuit. In addition, the common-mode interference signals appearing in the circuit can also be attenuated by the common-mode inductor, which is beneficial to improving the common-mode insertion loss of the filtering circuit.

[0072] It should be noted that in the multiple filter circuit structures shown in the above Embodiment 1, each sub-filter branch 121 includes a filter capacitor C2, and each sub-resonant branch includes a capacitor C1 and an inductor L2. In actual application, other devices with filtering functions can also be used in the sub-filter branch 121. For example, the sub-filter branch 121 can include multiple serially connected filter capacitors or filter inductors.

[0073] In one example, when the sub-resonant branch 111 includes multiple inductors and multiple capacitors, the middle node of the multiple sub-resonant branches 111 can be grounded. Taking the sub-resonant branch 111 including two capacitors and two inductors as an example, the structure of the filter circuit is as Figure 10 shown. At this time, an inductor and a capacitor are connected between each line in the single-phase AC power supply and the ground wire. The inductor and capacitor connected between each line and the ground wire can both form a filter path and eliminate the interference signals transmitted on the connected line.

[0074] Referring to the Figures 6 to 10 filter circuit structure provided in Embodiment 1 of the present application, each sub-filter branch 121 in the filter circuit is connected to the sub-resonant branch 111 through an inductor L11. Therefore, the sub-filter branch 121 cannot form a parallel relationship with the sub-resonant branch 111. Correspondingly, the filter circuit provided in Embodiment 1 of the present application cannot have a parallel resonance situation, thereby ensuring the filtering effect of the filter circuit.

[0075] Embodiment 2: The filter circuit is connected to a two-phase AC power supply with a neutral line

[0076] The filter circuit includes a first input terminal, a second input terminal, a third input terminal, a first output terminal, a second output terminal, and a third output terminal. Among them, the first input terminal of the filter circuit is connected to the first phase line L1 of the two-phase AC power supply, the second input terminal of the filter circuit is connected to the neutral line N of the two-phase AC power supply, and the third input terminal of the filter circuit is connected to the second phase line L2 of the two-phase AC power supply. The first output terminal of the filter circuit is connected to the first input terminal of the backend connected device, the second output terminal of the filter circuit is connected to the second input terminal of the backend connected device, and the third output terminal of the filter circuit is connected to the third output terminal of the backend connected device.

[0077] In a possible implementation manner, referring to Figure 11 shown, it is a schematic structural diagram of a filter circuit provided in Embodiment 2 of the present application. The filter circuit includes a first target filter branch 12 connected to the input terminal of the filter circuit, as Figure 11As shown, the LC resonance branch 11 includes a first sub-resonance branch 111 and a second sub-resonance branch 112, and the first target filter branch 12 includes a first sub-filter branch 121 and a second sub-filter branch 122. Then, the first inductor 13 includes at least two sub-inductors, which are inductor L11 and inductor L12 respectively.

[0078] Specifically, the first end of the first sub-resonance branch 111 is connected to the first end of the first sub-filter branch 121 and the first phase line L1 of the two-phase AC power supply through a first sub-inductor L11. The second end of the first sub-resonance branch 111 is connected to the second end of the second sub-filter branch 122 and the neutral line N of the two-phase AC power supply. The first end of the second sub-resonance branch 112 is connected to the second phase line L2 of the two-phase AC power supply through a first sub-inductor. The second end of the second sub-resonance branch 112 is connected to the neutral line N. The first end of the first sub-resonance branch 111 is also used to be directly connected to the first output end of the filter circuit, and the second end of the first sub-resonance branch 111 is also used to be directly connected to the second output end of the filter circuit. The first end of the second sub-resonance branch 112 is also used to be directly connected to the third output end of the filter circuit, and the second end of the second sub-resonance branch 112 is also used to be directly connected to the second output end of the filter circuit.

[0079] It should be noted that Figure 11 The filter circuit shown can use a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13, and the first inductor 13 can also use a common-mode inductor. When the first inductor 13 uses a common-mode inductor, the structure of the filter circuit is as Figure 12 shown. In addition to the above-mentioned inductor L11 and inductor L12 in each first inductor 13, there is also a sub-inductor L13, which is connected between the second end of the capacitor C2 and the second end of the inductor L2. Among them, the above-mentioned inductor L11, inductor L12 and inductor L13 are three-winding common-mode inductors, that is, inductor L11, inductor L12 and inductor L13 are wound around the same magnetic core.

[0080] In a possible implementation manner, as Figure 13 shown, it is another structural schematic diagram of the filter circuit provided in the second embodiment of the present application. The filter circuit includes a second target filter branch 12 connected to the output end of the filter circuit. Refer to Figure 13 shown. The LC resonance branch 11 includes a first sub-resonance branch 111 and a second sub-resonance branch 112, and the second target filter branch 12 includes a first sub-filter branch 121 and a second sub-filter branch 122. Since the power supply connected by the filter circuit includes two phase lines, each first inductor 13 includes two sub-inductors, which are inductor L11 and inductor L12 respectively.

[0081] Specifically, the first end of the first sub-resonant branch 111 is directly connected to the first phase line L1 of the two-phase AC power supply, and the second end of the first sub-resonant branch 111 is directly connected to the neutral line N of the two-phase AC power supply; the first end of the second sub-resonant branch 112 is used to be directly connected to the second phase line L2 of the two-phase AC power supply, and the second end of the second sub-resonant branch 112 is used to be directly connected to the neutral line N; the first end of the first sub-resonant branch 111 is also used to be connected to the first end of the first sub-filter branch 121 and the first output end of the filter circuit through a first sub-inductor L11, and the second end of the first sub-resonant branch 111 is also used to be connected to the second end of the first sub-filter branch 121 and the second output end of the filter circuit; the first end of the second sub-resonant branch 112 is also used to be connected to the first end of the second sub-filter branch 122 and the third output end of the filter circuit through a first sub-inductor L12, and the second end of the second sub-resonant branch 112 is also used to be connected to the second end of the second sub-filter branch 122 and the second output end of the filter circuit.

[0082] It should be noted that Figure 13 the shown filter circuit uses a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13. When the first inductor 13 uses a common-mode inductor, the structure of the filter circuit is as Figure 14 shown. In each first inductor 13, in addition to the above-mentioned inductor L11 and inductor L12, there is also a sub-inductor L13, and this inductor L13 is connected between the second end of the capacitor C2 and the inductor L2. Among them, the above-mentioned inductor L11, inductor L12, and inductor L13 are three-winding common-mode inductors, that is, the inductor L11, inductor L12, and inductor L13 are wound around the same magnetic core.

[0083] In a possible implementation manner, as shown in Figure 15 is a schematic structural diagram of another filter circuit provided in the second embodiment of the present application. The filter circuit includes a first target filter branch 12 connected to the input end of the filter circuit and a second target filter branch 12 connected to the output end of the filter circuit. As shown in Figure 15 the LC resonant branch 11 includes a first sub-resonant branch 111 and a second sub-resonant branch 112, the two target filter branches 12 include a first sub-filter branch 121 and a second sub-filter branch 122, and each first inductor 13 includes two sub-inductors, and the two sub-inductors are respectively the inductor L11 and the inductor L12.

[0084] Specifically, the first end of the first sub-resonant branch 111 is used to connect to the first end of the first sub-filter branch 121 and the first phase line L1 of the two-phase AC power supply through a first sub-inductor L11, and the second end of the first sub-resonant branch 111 is connected to the second end of the first sub-filter branch 121 and the neutral line N of the two-phase AC power supply; the first end of the second sub-resonant branch 112 is used to connect to the first end of the second sub-filter branch 122 and the second phase line L2 of the two-phase AC power supply through a first sub-inductor L12, and the second end of the second sub-resonant branch 112 is used to connect to the second end of the second sub-filter branch 122 and the neutral line N. The first end of the first sub-resonant branch 111 is also used to connect to the first end of the first sub-filter branch 121 and the first output end of the filter circuit through a first sub-inductor L11, and the second end of the first resonant branch 111 is also used to connect to the second end of the first sub-filter branch 121 and the second output end of the filter circuit; the first end of the second sub-resonant branch 112 is also used to connect to the first end of the second sub-filter branch 122 and the third output end of the filter circuit through a first sub-inductor L12, and the second end of the second sub-resonant branch 112 is also used to connect to the second end of the second sub-filter branch 122 and the second output end of the filter circuit.

[0085] It should be noted that Figure 15 The filter circuit shown uses a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13. When the first inductor 13 uses a common-mode inductor, in addition to the above-mentioned inductors L11 and L12, each first inductor 13 also includes a sub-inductor L13. See Figure 16 As shown, each inductor L13 is connected between the inductor L2 and the second end of the filter branch 12 to which the first inductor 13 belongs. Among them, the above-mentioned inductors L11, L12, and L13 are three-winding common-mode inductors, that is, the inductors L11, L12, and L13 are wound around the same magnetic core.

[0086] Referring to the filter circuit structure provided in Embodiment 2 of the present application as Figures 11 to 16 shown, each sub-filter branch in the filter circuit is connected to the sub-resonant branch through an inductor. Therefore, the sub-filter branch cannot form a parallel relationship with the sub-resonant branch. Correspondingly, the filter circuit provided in Embodiment 2 of the present application cannot have a parallel resonance situation, thereby ensuring the filtering effect of the filter circuit.

[0087] In actual use, the present application provides in Embodiment 2 Figure 12 , Figure 14 and Figure 16In the shown filter circuit structure, a common-mode inductor is used as the first inductor. Since the common-mode inductor has the advantages of small magnetic loss and leakage inductance, it is beneficial to avoid parallel resonance between the sub-resonant branch and other filter branches outside the above-mentioned sub-filter branches, thereby ensuring the filtering effect of the filter circuit. In addition, the common-mode inductor can also be used to attenuate the common-mode interference signals that appear in the circuit, which is beneficial to improving the common-mode insertion loss of the filter circuit.

[0088] Embodiment 3: The filter circuit is connected to a three-phase AC power supply

[0089] The filter circuit includes a first input terminal, a second input terminal, a third input terminal, a first output terminal, a second output terminal, and a third output terminal. Among them, the first input terminal of the filter circuit is connected to the first phase line L1 of the three-phase AC power supply, the second input terminal of the filter circuit is connected to the second phase line L2 of the three-phase AC power supply, and the third input terminal of the filter circuit is connected to the third phase line L3 of the three-phase AC power supply. The first output terminal of the filter circuit is connected to the first input terminal of the backend connection device, the second output terminal of the filter circuit is connected to the second input terminal of the backend connection device, and the third output terminal of the filter circuit is connected to the third output terminal of the backend connection device.

[0090] In a possible implementation manner, refer to Figure 17 As shown, it is a schematic structural diagram of a filter circuit provided in Embodiment 3 of the present application. The filter circuit includes a first target filter branch 12 connected to the input terminal of the filter circuit. As Figure 17 shown, the LC resonance branch 11 includes a first sub-resonance branch 111, a second sub-resonance branch 112, and a third sub-resonance branch 113. The first target filter branch 12 includes a first sub-filter branch 121, a second sub-filter branch 122, and a third sub-filter branch 123. Each first inductor 13 includes three sub-inductors, which are inductor L11, inductor L12, and inductor L13 respectively.

[0091] Specifically, the first end of the first sub-resonant branch 111 is connected to the first end of the first sub-filter branch 121 and the first phase line L1 of the three-phase AC power supply through a first sub-inductor L11. The first end of the second sub-resonant branch 112 is connected to the first end of the second sub-filter branch 122 and the second phase line L2 of the three-phase AC power supply through a first sub-inductor L12. The first end of the third sub-resonant branch 113 is connected to the first end of the third sub-filter branch 123 and the third phase line L3 of the three-phase AC power supply through a first sub-inductor L13. The first end of the first sub-resonant branch 111 is also directly connected to the first output end of the filter circuit. The first end of the second sub-resonant branch 112 is also directly connected to the second output end of the filter circuit. The first end of the third sub-resonant branch 113 is also used to be directly connected to the third output end of the filter circuit. Wherein, the second end of the first sub-resonant branch 111 is connected to the second end of the second sub-resonant branch 112 and the second end of the third sub-resonant branch 113. The second end of the first sub-filter branch 121 is connected to the second end of the second sub-filter branch 122 and the second end of the third sub-filter branch 123.

[0092] It should be noted that Figure 17 The shown filter circuit can use a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13. The first inductor 13 can also use a common-mode inductor. When the first inductor 13 uses a common-mode inductor, the inductors L11, L12, and L13 connected between the three sub-resonant branches and the three-phase AC power supply are three-winding common-mode inductors, that is, the inductors L11, L12, and L13 are wound on the same magnetic core.

[0093] In a possible implementation, if the three-phase AC power supply transmits electrical energy in a three-phase four-wire system, that is, in addition to being connected to the above-mentioned phase lines L1, L2, and L3, the three-phase AC power supply also includes a neutral line N. Then the filter circuit also includes a fourth input end and a fourth output end. The fourth input end of the filter circuit is connected to the above-mentioned neutral line N. The fourth output end of the filter circuit is connected to the fourth input end of the load. The neutral line N is directly connected to the second ends of the above three sub-resonant branches. The fourth output end of the filter circuit is directly connected to the second ends of the above three sub-resonant branches.

[0094] In practical applications, if the first inductor 13 in the filter circuit uses a common-mode inductor, when the filter circuit is connected to a three-phase AC power supply with a neutral line N, then in addition to the above-mentioned inductors L11, L12, and L13, the first inductor 13 also includes a sub-inductor L14. See Figure 18As shown, the inductor L14 is connected between the second ends of three sub-filter branches and the inductor L2. Among them, the inductors L11, L12, L13, and L14 are four-winding common-mode inductors, that is, the inductors L11, L12, L13, and L14 are wound on the same magnetic core.

[0095] In a possible implementation, as Figure 19 shown, it is a schematic structural diagram of a filtering circuit provided in the third embodiment of the present application. The filtering circuit includes a second target filtering branch 12 connected to the output end of the filtering circuit. As Figure 19 shown, the LC resonance branch 11 includes a first sub-resonance branch 111, a second sub-resonance branch 112, and a third sub-resonance branch 113. The second target filtering branch 12 includes a first sub-filter branch 121, a second sub-filter branch 122, and a third sub-filter branch 123. Each first inductor 13 includes at least three sub-inductors, which are the inductors L11, L12, and L13 respectively.

[0096] Specifically, the first end of the first sub-resonance branch 111 is directly connected to the first phase line L1 of the three-phase AC power supply. The first end of the second sub-resonance branch 112 is directly connected to the second phase line L2 of the three-phase AC power supply. The first end of the third sub-resonance branch 113 is directly connected to the third phase line L3 of the three-phase AC power supply. The first end of the first sub-resonance branch is also used to be connected to the first end of the first sub-filter branch 121 and the first output end of the filtering circuit through a first sub-inductor L11. The first end of the second sub-resonance branch 112 is also used to be connected to the first end of the second sub-filter branch 122 and the second output end of the filtering circuit through a first sub-inductor L12. The first end of the third sub-resonance branch 113 is also used to be connected to the first end of the third sub-filter branch 123 and the third output end of the filtering circuit through a first sub-inductor L13. The second end of the first sub-resonance branch 111 is connected to the second end of the second sub-resonance branch 112 and the second end of the third sub-resonance branch 113.

[0097] It should be noted that Figure 19 the shown filtering circuit can use a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13. The first inductor 13 can also use a common-mode inductor. When the first inductor 13 uses a common-mode inductor, the inductors L11, L12, and L13 connected between the three sub-resonance branches and the three-phase AC power supply are three-winding common-mode inductors, that is, the inductors L11, L12, and L13 are wound on the same magnetic core.

[0098] In a possible implementation, if the three-phase AC power supply transmits electric energy in a three-phase four-wire system, that is, in addition to being connected to the above-mentioned phase lines L1, L2, and L3, the three-phase AC power supply also includes a neutral line N, then the filtering circuit further includes a fourth input terminal and a fourth output terminal. The fourth input terminal of the filtering circuit is connected to the neutral line N, and the fourth output terminal of the filtering circuit is connected to the fourth input terminal of the load. The neutral line N is directly connected to the second ends of the above three sub-resonant branches, and the fourth output terminal of the filtering circuit is directly connected to the second ends of the above three sub-resonant branches.

[0099] In practical applications, if the first inductor in the filtering circuit is a common-mode inductor, when the filtering circuit is connected to a three-phase AC power supply with a neutral line N, in addition to the above-mentioned inductors L11, L12, and L13, the first inductor 13 further includes a sub-inductor L14. Refer to Figure 20 As shown, this inductor L14 is connected between the second ends of the three filtering branches and the inductor L2. Among them, the inductors L11, L12, L13, and L14 are four-winding common-mode inductors, that is, the inductors L11, L12, L13, and L14 are wound around the same magnetic core.

[0100] In a possible implementation, as Figure 21 shown, it is a schematic structural diagram of another filtering circuit provided in Embodiment 3 of the present application. The filtering circuit includes a first target filtering branch 12 connected to the input terminal of the filtering circuit and a second target filtering branch 12 connected to the output terminal of the filtering circuit. Refer to Figure 21 shown, the LC resonant branch 11 includes a first sub-resonant branch 111, a second sub-resonant branch 112, and a third sub-resonant branch 113. Both target filtering branches 12 include a first sub-filtering branch 121, a second sub-filtering branch 122, and a third sub-filtering branch 123. Each first inductor 13 includes at least three sub-inductors, namely inductors L11, L12, and L13.

[0101] Specifically, the first end of the first sub-resonant branch 111 is connected to the first end of the first sub-filter branch 121 and the first phase line L1 of the three-phase AC power supply through a first sub-inductor L11. The first end of the second sub-resonant branch 112 is connected to the first end of the second sub-filter branch 122 and the second phase line L2 of the three-phase AC power supply through a first sub-inductor L12. The first end of the third sub-resonant branch 113 is connected to the first end of the third sub-filter branch 123 and the third phase line L3 of the three-phase AC power supply through a first sub-inductor L13. The first end of the first sub-resonant branch 111 is also used to be connected to the first end of the first sub-filter branch 121 and the first output end of the filter circuit through a first sub-inductor L11. The first end of the second sub-resonant branch 112 is also used to be connected to the first end of the second sub-filter branch 122 and the second output end of the filter circuit through a first sub-inductor L12. The first end of the third sub-resonant branch 113 is also used to be connected to the first end of the third sub-filter branch 123 and the third output end of the filter circuit through a first sub-inductor L13. The second end of the first sub-resonant branch 111 is connected to the second end of the second sub-resonant branch 112 and the second end of the third sub-resonant branch 113.

[0102] It should be noted that Figure 21 The shown filter circuit can use a differential-mode inductor or other inductors commonly used in the industry as the first inductor 13. The first inductor 13 can also use a common-mode inductor. When the first inductor 13 uses a common-mode inductor, the inductors L11, L12, and L13 connected between the three sub-resonant branches and the three-phase AC power supply are three-winding common-mode inductors, that is, the inductors L11, L12, and L13 are wound around the same magnetic core. And the inductors L11, L12, L13, and L14 connected between the three sub-resonant branches and the output end of the filter circuit are three-winding common-mode inductors.

[0103] In a possible implementation, if the three-phase AC power supply transmits electric energy in a three-phase four-wire system, that is, in addition to being connected to the above-mentioned phase lines L1, L2, and L3, the three-phase AC power supply also includes a neutral line N. Then the filter circuit also includes a fourth input end and a fourth output end. The fourth input end of the filter circuit is connected to the above-mentioned neutral line N. The fourth output end of the filter circuit is connected to the fourth input end of the load. The neutral line N is directly connected to the second ends of the above three sub-resonant branches. The fourth output end of the filter circuit is directly connected to the second ends of the above three sub-resonant branches.

[0104] In actual application, if the first inductor in the filter circuit uses a common-mode inductor, when the filter circuit is connected to a three-phase AC power supply with a neutral line N, in addition to the above-mentioned inductors L11, L12, and L13, the first inductor 13 also includes a sub-inductor L14. See Figure 22As shown, the inductor L14 connects the second ends of three filtering branches and the inductor L2. Among them, the inductors L11, L12, L13, and L14 are four-winding common-mode inductors, that is, the inductors L11, L12, L13, and L14 are wound on the same magnetic core.

[0105] Refer to the filtering circuit structure provided in Embodiment 3 of this application as Figures 17 to 22 shown. Each sub-filtering branch in the filtering circuit is connected to the sub-resonant branch through an inductor. Therefore, the sub-filtering branch cannot form a parallel relationship with the sub-resonant branch. Correspondingly, the filtering circuit provided in Embodiment 3 of this application cannot have a parallel resonance situation, thus ensuring the filtering effect of the filtering circuit.

[0106] In actual use, the Figure 18 、 Figure 20 and Figure 22 filtering circuit structure shown. The common-mode inductor is used as the first inductor. Since the common-mode inductor has the advantages of small magnetic loss and leakage inductance, it is beneficial to avoid parallel resonance between the sub-resonant branch and other filtering branches outside the above-mentioned sub-filtering branches, thus ensuring the filtering effect of the filtering circuit. In addition, the common-mode inductor can also be used to attenuate the common-mode interference signals that appear in the circuit, which is beneficial to improving the common-mode insertion loss of the filtering circuit.

[0107] It should be noted that the above Figures 3 to 22 filtering circuit structure shown is only for illustration. According to the number and type of devices in the filtering branch and the LC resonant branch, the filtering circuit provided in the embodiments of this application can also have other circuit structures, which are not introduced one by one in the embodiments of this application.

[0108] In actual application, the above filtering circuit can be set on a switching power supply or a signal source. The filtering circuit can also be provided with the above external interface. The power supply and other devices can be connected to the filtering circuit through the above external interface. At this time, the filtering circuit can be regarded as a device independent of the switching power supply.

[0109] Obviously, those skilled in the art can make various changes and modifications to this application without departing from the protection scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalent technologies, this application is also intended to include these changes and modifications.

Claims

1. A filtering circuit, characterized in that, Comprising: An LC resonance branch, at least one filter branch, and a first inductor corresponding to each filter branch one by one; Each filter branch is connected to the LC resonance branch through the corresponding first inductor, and a single filter branch is connected to the input end of the filter circuit or the output end of the filter circuit.

2. The filtering circuit according to claim 1, characterized in that, The LC resonance branch includes at least one second inductor and at least one first capacitor, and the at least one second inductor and the at least one first capacitor are connected in series.

3. The filtering circuit according to claim 2, characterized in that, The middle node of the LC resonance branch is grounded, and at least one second inductor and at least one first capacitor are connected between the middle node and each port of the LC resonance branch.

4. The filtering circuit according to claim 1, characterized in that, The LC resonance branch includes at least one sub-resonance branch, each filter branch includes a sub-filter branch corresponding to each sub-resonance branch one by one, each first inductor includes a first sub-inductor corresponding to each sub-filter branch in the connected filter branch one by one, each sub-filter branch is connected to the corresponding sub-resonance branch through the corresponding first sub-inductor, and the number of sub-resonance branches is the same as the number of phase lines in the power supply connected to the input end of the filter circuit.

5. The filtering circuit according to claim 4, characterized in that, If the filter circuit includes a first target filter branch connected to the input end of the filter circuit, the first end of each sub-filter branch in the first target filter branch is connected to a phase line in the power supply, the first end of each sub-filter branch in the first target filter branch is connected to one end of the corresponding sub-resonance branch through the corresponding first sub-inductor, and the second end of each sub-filter branch in the first target filter branch is connected to the second end of each sub-resonance branch, wherein the phase lines connected to the first end of each sub-filter branch in the first target filter branch are different.

6. The filtering circuit according to claim 5, characterized in that, If the power supply connected to the filter circuit includes a neutral line or a zero line, the second end of each sub-filter branch in the first target filter branch is connected to the neutral line or the zero line.

7. The filtering circuit according to claim 6, characterized in that, If the first inductor connected to the first target filter branch is a common-mode inductor, the first inductor connected to the first target filter branch further includes a second sub-inductor, one end of the second sub-inductor is connected to the neutral line and the second end of each sub-filter branch in the first target filter branch, and the other end of the second sub-inductor is connected to the second end of each sub-resonance branch, or one end of the second sub-inductor is connected to the zero line and the second end of each sub-filter branch in the first target filter branch, and the other end of the second sub-inductor is connected to the second end of each sub-resonance branch.

8. The filtering circuit according to claim 4, characterized in that, If the filter circuit includes a second target filter branch connected to the output end of the filter circuit, the first end of each sub-filter branch in the second target filter branch is connected to an output port of the filter circuit, the first end of each sub-filter branch in the second target filter branch is connected to one end of the corresponding sub-resonance branch through the corresponding first sub-inductor, and the second end of each sub-filter branch in the second target filter branch is connected to the second end of each sub-resonance branch, wherein the output ports connected to the first end of each sub-filter branch in the second target filter branch are different.

9. The filtering circuit according to claim 8, characterized in that, If the power supply connected to the filtering circuit includes a neutral line or a zero line, the second end of each sub-filtering branch in the second target filtering branch is connected to an output port of the filtering circuit, and the output port connected to the second end of each sub-filtering branch in the second target filtering branch is different from the output port connected to the first end of each sub-filtering branch in the second target filtering branch.

10. The filtering circuit according to claim 9, characterized in that, If the first inductor connected to the second target filtering branch is a common-mode inductor, the first inductor connected to the second target filtering branch further includes a second sub-inductor, one end of the second sub-inductor is connected to the second end of each sub-resonant branch, and the other end of the second sub-inductor is connected to the second end of each sub-filtering branch in the second target filtering branch.

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