CN220210240U - Filter circuit and switching power supply - Google Patents

Abstract

A filter circuit and a switching power supply are used for increasing the filter range of the filter circuit and reducing the cost of the filter circuit. The harmonic circuit comprises a first filtering branch, a second filtering branch and a third filtering branch. The first end of the first filtering branch is connected with the first input end of the filtering circuit, and the second end of the first filtering branch is connected with the second input end of the filtering circuit; the second filtering branch is connected with the first filtering branch in parallel, the first end of the second filtering branch is connected with the first output end of the filtering circuit, and the second end of the second filtering branch is connected with the second output end of the filtering circuit; the third filter branch is connected between the intermediate nodes of the first filter branch and the second filter branch in a bridging way. When an input signal enters the filter circuit, besides the first filter branch and the second filter branch can be used as filter paths to realize a filter function, the third filter branch can be combined with the first filter branch and the second filter branch to form a plurality of filter paths and realize the filter function, so that the filter range is enlarged, and the cost of the filter circuit is reduced.

Description

Filter circuit and switching power supply

Technical Field

The present disclosure relates to the field of power, and in particular, to a filter circuit and a switching power supply.

Background

The resonator has the advantages of high performance, small volume and strong power tolerance, and is widely applied to electronic equipment such as mobile phones and the like as a filter device to eliminate harmonic signals with specific frequencies. With the development of electronic devices, harmonic signals that need to be filtered are increasing.

The resonator commonly used at present is an LC resonator, the circuit structure of which can be seen in fig. 1, and the LC is connected in series to form a resonant path, and the input signal is frequency f after passing through the resonant path _c1 To f _c2 The harmonic signals between the two are filtered out, so that the harmonic signal suppression effect is realized. Wherein the resonant frequency of the LC resonator shown in FIG. 1 is f ₀ The harmonic signal suppression waveform can be seen in fig. 2. In practical use, the resonator can only inhibit harmonic signals with specific frequencies, and has difficulty in inhibiting devices with harmonic signals with various frequencies, so that the problem needs to be solved.

Disclosure of Invention

The application provides a filter circuit and a switching power supply, which are used for improving the harmonic suppression range of a resonant circuit and reducing the cost of the resonant circuit.

The specific technical scheme provided by the embodiment of the application is as follows:

in a first aspect, the present application provides a filter circuit, where the filter circuit may be connected to an electronic device and is configured to eliminate a harmonic signal of a specific frequency in the electronic device. Specifically, the filter circuit at least comprises a first filter branch, a second filter branch and a third filter branch. The first end of the first filtering branch is connected with the first input end of the filtering circuit, and the second end of the first filtering branch is connected with the second input end of the filtering circuit; the second filtering branch is connected with the first filtering branch in parallel, the first end of the second filtering branch is connected with the first output end of the filtering circuit, and the second end of the second filtering branch is connected with the second output end of the filtering circuit; the first end of the third filtering branch is connected with the middle node of the first filtering branch, and the second end of the third filtering branch is connected with the middle node of the second filtering branch.

By adopting the filter circuit structure, the first filter branch and the second filter circuit are connected between the input end and the output end of the filter circuit, and when the input end of the filter circuit receives an input signal, the first filter branch and the second filter branch are respectively used as a harmonic signal filtering path and filter harmonic signals with specific frequency in the input signal. Meanwhile, as the third filtering branch is bridged between the middle node of the first filtering branch and the middle node of the second filtering branch, part of devices of the first filtering branch, the third filtering branch and part of devices of the second filtering branch can form a harmonic signal filtering path, and part of devices of the second filtering branch, the third filtering branch and part of devices of the first filtering branch can form a new harmonic signal filtering path and filter harmonic signals with different frequencies in input signals respectively. Therefore, harmonic signal filtering paths exceeding the number of the filtering branches can be generated in the filtering circuit through the third filtering branches which are connected in a bridging way, so that the cost of the filtering circuit can be reduced while the filtering range of the filtering circuit is enlarged.

In one possible design, the first filter leg comprises a first capacitance and a first inductance, and the second filter leg comprises a second capacitance and a second inductance.

The first end of the first capacitor is connected with the first input end of the filter circuit, and the second end of the first capacitor is connected with the first end of the first inductor; the first end of the first inductor is an intermediate node of the first filtering branch, and the second end of the first inductor is connected with the second input end of the filtering circuit; the first end of the second capacitor is connected with the first end of the first capacitor and the first output end of the filter circuit, and the second end of the second capacitor is connected with the first end of the second inductor; the first end of the second inductor is an intermediate node of the second filtering branch, and the second end of the second inductor is connected with the second end of the first inductor and the second output end of the filtering circuit.

By adopting the circuit, the inductance device and the capacitance device are arranged in the first filtering branch and the second filtering branch, and the filtering function of the filtering circuit can be realized through the LC resonance principle. In addition, the inductance devices and the capacitance devices in the two filtering branches can select different parameters, so that harmonic signals with different frequencies are filtered, and the filtering range of the filtering circuit is enlarged.

In one possible design, the first filter branch comprises a third inductance and a third capacitance, and the second filter branch comprises a fourth inductance and a fourth capacitance.

The first end of the third inductor is connected with the first input end of the filter circuit, and the second end of the third inductor is connected with the first end of the third capacitor; the first end of the third capacitor is an intermediate node of the first filtering branch, and the second end of the third capacitor is connected with the second input end of the filtering circuit; the first end of the fourth inductor is connected with the first end of the third inductor and the first output end of the filter circuit, and the second end of the fourth inductor is connected with the first end of the fourth capacitor; the first end of the fourth capacitor is an intermediate node of the second filtering branch, and the second end of the fourth capacitor is connected with the second end of the third capacitor and the second output end of the filtering circuit.

In one possible design, the third filter branch comprises a fifth capacitor, a first end of which is connected to the intermediate node of the first filter branch, and a second end of which is connected to the intermediate node of the second filter branch.

By adopting the filter circuit structure, the fifth capacitor is bridged between the first filter branch and the second filter branch, and can form a plurality of filter paths with part of devices of the first filter branch and part of devices of the second filter branch, and each filter path can carry out filter processing on harmonic signals with specific frequency, so that the filter range of the filter circuit is enlarged.

In one possible design, the third filter branch comprises a fifth inductance, a first end of which is connected to the intermediate node of the first filter branch, and a second end of which is connected to the intermediate node of the second filter branch.

By adopting the filter circuit structure, the fifth inductor is bridged between the first filter branch and the second filter branch, and can form a plurality of filter paths with part of devices of the first filter branch and part of devices of the second filter branch, and each filter path can carry out filter processing on harmonic waves with specific frequency, so that the filter range of the filter circuit is enlarged.

In one possible design, the filter circuit further comprises: at least one fourth filtering branch and at least one fifth filtering branch.

Wherein, at least one fourth filtering branch is in one-to-one correspondence with at least one fifth filtering branch. Each fourth filtering branch is connected with the first filtering branch and the second filtering branch in parallel; the first end of each fifth filtering branch is connected with the middle node of the corresponding fourth filtering branch, the second end of each fifth filtering branch is connected with the middle node of any filtering branch except the corresponding fourth filtering branch in the filtering circuit, and the filtering branch connected with the second end of each fifth filtering branch is connected with the corresponding fourth filtering branch in parallel. By adopting the filter circuit structure, the first filter branch, the second filter branch and the third filter branch can form an H-shaped filter framework, and harmonic signals in a fixed frequency interval are filtered. The fourth filtering branch, the fifth filtering branch and the other filtering path in the circuit can form a new H-shaped filtering framework, and the newly added H-shaped filtering framework can increase the filtering range of the filtering circuit, so that the filtering requirement of equipment is met.

In one possible design, at least one sixth filter branch is further connected in series between the first filter branch and the second access end of the filter circuit, at least one seventh filter branch is further connected in series between the second filter branch and the second output end of the filter circuit, wherein the at least one sixth filter branch corresponds to the at least one seventh filter branch one to one, and the first end of each sixth filter branch is connected with the first end of the corresponding seventh filter branch through one eighth filter branch.

By adopting the filter circuit structure, the first filter branch, the second filter branch and the third filter branch can form an H-shaped filter framework to filter harmonic signals in a fixed frequency interval. When a large number of harmonic signals with different frequencies exist in the equipment connected with the filter circuit, the eighth filter branch and the ninth filter branch can form a new filter path, and the filtering of the harmonic signals is realized, so that the filtering requirement of the equipment is met.

In one possible design, the first filtering branch and/or the second filtering branch further comprises: at least one first switch and at least one sixth capacitor.

Wherein, at least one first switch and at least one sixth electric capacity one-to-one. The first end of each first switch is connected with the first end of a capacitor in the filter branch, and the second end of each first switch is connected with the first end of a corresponding sixth capacitor; the second end of each sixth capacitor is connected with the second end of the capacitor in the filter branch.

By adopting the filter circuit structure, the filter circuit realizes the filter function through the LC resonance principle, and when the first switch is turned off, only one capacitor is arranged in the filter branch. When the first switch is turned on, the plurality of capacitors in the filtering branch are connected in parallel. Therefore, the total capacitance of the filtering branch can be adjusted through the on and off of the first switch, so that the filtering frequency of the filtering path where the filtering branch is located is adjusted.

In one possible design, the first filtering branch and/or the second filtering branch further comprises: at least one second switch and at least one sixth inductance.

Wherein, at least one second switch and at least one sixth inductance are in one-to-one correspondence. The first end of each second switch is connected with the first end of the inductor in the filter branch, and the second end of each second switch is connected with the first end of the corresponding sixth inductor; the second end of each sixth inductor is connected with the second end of the inductor in the filter branch.

By adopting the filter circuit structure, the filter circuit realizes the filter function through the LC resonance principle, and when the second switch is turned off, only one inductor is arranged in the filter branch. When the second switch is turned on, the plurality of inductors in the filtering branch are connected in parallel. Therefore, the total inductance of the filtering branch circuit can be adjusted through the on and off of the second switch, so that the filtering frequency of the filtering path where the filtering branch circuit is located is adjusted.

In one possible design, the filter circuit further includes a controller for controlling on or off of the switches in the filter branches to adjust the total inductance or total capacitance in the filter branches.

By adopting the filter circuit structure, the controller can be connected with the switch in the filter branch, and the on or off of the switch is controlled by providing a driving signal for the switch, so that the filter range of the filter circuit is controlled.

In a second aspect, embodiments of the present application provide a switching power supply that may include a switching circuit and a filter circuit provided in the first aspect of embodiments of the present application and in any of the designs.

The first end of the switching circuit is used for being connected with a power supply, the second end of the switching circuit is connected with the filter circuit, and the switching circuit is used for converting the voltage output by the power supply into a first voltage; the filter circuit is used for being connected with a load, filtering the first voltage and outputting the first voltage to the load, wherein the rated voltage of the load is the first voltage.

In addition, the technical effects of any possible design in the second aspect may be referred to as technical effects of different designs in the first aspect of the embodiments of the present application, which are not described herein.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of an LC resonator according to an embodiment of the present application;

fig. 2 is a schematic diagram of a filtering waveform of an LC resonator according to an embodiment of the present application;

fig. 3 is a schematic diagram of a filter circuit according to an embodiment of the present application;

fig. 4 is a schematic diagram of a second structure of a filtering circuit according to an embodiment of the present application;

fig. 5 is a schematic diagram III of a structure of a filtering circuit according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of a third filtering branch according to an embodiment of the present application;

fig. 7 is a schematic diagram of a filtering waveform of a filtering circuit according to an embodiment of the present application;

fig. 8 is a schematic structural diagram ii of a third filtering branch according to an embodiment of the present application;

fig. 9 is a schematic structural diagram III of a third filtering branch according to an embodiment of the present application;

Fig. 10 is a schematic structural diagram of a third filtering branch according to an embodiment of the present application;

fig. 11 is a schematic structural diagram of a filtering circuit according to an embodiment of the present application;

fig. 12 is a schematic diagram of a filter circuit according to an embodiment of the present disclosure;

fig. 13 is a schematic diagram sixth of a structure of a filtering circuit according to an embodiment of the present application;

fig. 14 is a schematic diagram of a filter circuit according to an embodiment of the present application.

Detailed Description

Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

The terminology used in the description section of the present application is for the purpose of describing particular embodiments of the present application only and is not intended to be limiting of the present application. It will be apparent that the described embodiments are merely some, but not all embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

In the following, some terms in the embodiments of the present application are explained for easy understanding by those skilled in the art.

(1) The terms "first," "second," and the like in embodiments of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the present application described herein may be implemented in sequences other than those illustrated or otherwise described herein.

(2) The term "plurality" in the embodiments of the present application means two or more, and other adjectives are similar thereto.

(3) In the embodiment of the application, "and/or" describing the association relationship of the association object, three relationships may exist, for example, a and/or B may represent: a alone, a and B together, and B alone, wherein a, B may be singular or plural.

(4) "connected" in embodiments of the present application may be understood as electrically connected or communicatively connected. The electrical connection of two electrical components may be a direct or indirect connection between two electrical components. For example, a may be directly connected to B, or indirectly connected to B through one or more other electrical components, for example, a may be directly connected to B, or directly connected to C, and C may be directly connected to B, where a and B are connected through C. The communication connection of the two electrical components is a wireless connection between the two electrical components, i.e. an electromagnetic connection of the two electrical components.

(5) The switching device in the embodiments of the present application may be one or more of various types of switching transistors such as a relay, a metal oxide semiconductor field effect transistor (metal oxide semiconductor field effect transistor, MOSFET), a bipolar junction transistor (bipolar junction transistor, BJT), an insulated gate bipolar transistor (insulated gate bipolartransistor, IGBT), a silicon carbide (SiC) transistor, a silicon controlled rectifier (silicon controlled rectifier, SCR), and the like, which are not further listed herein. The package form of each switch tube can be single tube package or multi-tube package, and the embodiment of the application does not limit the package form. Each switching tube can comprise a first end, a second end and a control end, wherein the control end can control the switching tube to be turned on or off according to the received PWM signal. When the switching tube is turned on, current can be transmitted between the first end and the second end of the switching tube, and when the switching tube is turned off, current cannot be transmitted between the first end and the second end of the switching tube. Taking a MOSFET as an example, the control end of the switching tube is a gate, the first end of the switching tube may be a source, the second end may be a drain, or the first end may be a drain, and the second end may be a source.

It should be noted that, SCR can only realize unidirectional transmission of current, and unidirectional transmission of current can only be realized when no diode is configured at two ends of MOSFET, so two SCR or two MOSFET are generally adopted to realize bidirectional transmission of current.

The application scenario of the technical solution in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. The scheme provided by the embodiment of the application can be applied to electronic equipment with a plurality of frequency harmonic signals. Taking electronic equipment as a switching power supply for example, a plurality of switching devices are generally arranged in the switching power supply, voltage regulation processing is carried out on voltage output by a power supply through controlling on and off of the switching devices, but harmonic signals with different frequencies can be generated by frequent on and off of the switching devices, if the harmonic signals are transmitted to a load connected with the rear end, normal operation of the load can be affected, and load faults can be caused when serious.

Wherein the electronic device includes but is not limited to: switching power supplies, receivers, transmitters, systems configured with any of the above, and the like. The system configuring any of the above devices may be, but is not limited to: wireless base stations, navigation systems, satellite communications, and the like.

The embodiment of the application provides a filter circuit and a switching power supply, which are used for increasing the filter range of the filter circuit and reducing the cost of the filter circuit.

The inventive concept of the present application can be summarized as follows: a third filtering branch carrying a filtering device can be bridged between intermediate nodes of the first filtering branch and the second filtering branch, the third filtering branch can be respectively combined with the first filtering branch and the second filtering branch to form a plurality of filtering paths, and each filtering path can respectively filter harmonic signals in a specific frequency range. Therefore, a plurality of filtering paths can be generated by adding a third filtering branch, so that the filtering range of the filtering circuit is enlarged, and the cost of the filtering circuit is reduced.

Fig. 3 is a schematic structural diagram of a filter circuit according to an embodiment of the present application, where the filter circuit includes at least a first filter branch, a second filter branch, and a third filter branch.

It should be understood that the filter circuit shown in fig. 3 is only one example, and that the filter circuit may have more or fewer components than shown in fig. 3, may combine two or more components, or may have a different configuration of components. The various components shown in fig. 3 may be implemented in hardware, software, or a combination of hardware and software, including one or more signal processing and/or application specific integrated circuits.

Referring to fig. 3, a first end of the first filtering branch is connected to a first input end of the filtering circuit, and a second end of the first filtering branch is connected to a second input end of the filtering circuit; the second filtering branch is connected with the first filtering branch in parallel, the first end of the second filtering branch is connected with the first output end of the filtering circuit, and the second end of the second filtering branch is connected with the second output end of the filtering circuit; the first end of the third filter branch is connected with the middle node N1 of the first filter branch, and the second end of the third filter branch is connected with the middle node N2 of the second filter branch.

In practical application, the first input end of the filter circuit may be the end of the filter circuit receiving the high-level signal, and the second input end is the end of the filter circuit receiving the low-level signal. The second input end of the filter circuit may be an end receiving a high level signal, and the first input end may be an end receiving a low level signal. Referring to fig. 3, since the first input terminal is connected to the first output terminal and the second input terminal is connected to the second output terminal, when the first input terminal is the end receiving the high level signal and the second output terminal is the end receiving the low level signal, the first output terminal is the end outputting the high level signal in the filter circuit, and the second output terminal is the end outputting the low level signal in the filter circuit.

It should be noted that the low level and the high level in the present application do not refer to a fixed voltage, but merely indicate that the voltage amplitude of the high level is higher than the voltage amplitude of the low level.

Next, the operation of the filter circuit of the present application will be described by taking the first input terminal of the filter circuit as an end that receives the high-level signal as an example.

In general, a second input end of the filter circuit, which receives a low-level signal, is grounded or connected to a ground line of the electronic device, so that when an input signal reaches the filter circuit through the input end of the filter circuit, the first filter branch and the second filter branch respectively form a filter path for the input signal to reach the ground line, and each filter path can filter out a harmonic signal in a specific frequency range in the input signal, thereby realizing a filtering function of the filter circuit. In addition to the two filtering paths, the filtering circuit in the present application further includes at least two filtering paths. Referring to fig. 3, the first filtering branch and the second filtering branch include an upper half portion and a lower half portion, where the upper half portion of the filtering branch is a device between a first end and a middle node of the filtering branch, and the lower half portion of the filtering branch is a device between a middle node and a ground line of the filtering branch, and since the third filtering branch is bridged between the middle node N1 of the first filtering branch and the middle node N2 of the second filtering branch, the upper half portion of the first filtering branch, the third filtering branch and the lower half portion of the second filtering branch may form a filtering path, and the upper half portion of the second filtering branch, the third filtering branch and the lower half portion of the first filtering branch may also form a filtering path, and the two filtering paths may also filter harmonic signals in a specific frequency interval in the input signal and implement a filtering function. Therefore, a plurality of filtering paths can be generated by arranging a third filtering branch, and the cost of the filtering circuit is reduced while the filtering range of the filtering circuit is enlarged.

In practical application, the filter circuit can filter harmonic signals by adopting an LC resonance principle, namely, inductance and capacitance are selected as filter devices. Since the first filtering branch and the second filtering branch can be used as a filtering path, at least one inductor and at least one capacitor are required to be configured in the first filtering branch and the second filtering branch. The third filtering branch and the first filtering branch and the second filtering branch form a filtering path together, and as the filtering devices are already arranged in the first filtering branch and the second filtering branch, only one filtering device can be arranged in the third filtering branch for reducing the filtering cost of the filtering circuit and used for adjusting the frequency of harmonic signals filtered by the filtering path.

The filtering process of the filtering circuit will be described below by taking an example in which the first filtering branch and the second filtering branch include an inductor and a capacitor.

In one possible implementation, the first filtering branch may include a first capacitor C1 and a first inductor L1, and the second filtering branch includes a second capacitor C2 and a second inductor L2.

Referring to fig. 4, a first end of a first capacitor C1 is connected to a first input terminal vin+ of the filter circuit, and a second end of the first capacitor C1 is connected to a first end of a first inductor L1; the first end of the first inductor L1 is an intermediate node N1 of the first filtering branch, and the second end of the first inductor L1 is connected with the second input end Vin-of the filtering circuit; the first end of the second capacitor C2 is connected with the first end of the first capacitor C1 and the first output end Vout+ of the filter circuit, and the second end of the second capacitor C2 is connected with the first end of the second inductor L2; the first end of the second inductor L2 is an intermediate node N2 of the second filtering branch, and the second end of the second inductor L2 is connected with the second end of the first inductor L1 and the second output end Vout of the filtering circuit.

In practical application, in the structures of the first filtering branch and the second filtering branch shown in fig. 4, the resonant frequency of the first filtering branch isThe harmonic signal of the frequency interval with the center frequency f1 can be filtered. The resonance frequency of the second filter branch is +.>The harmonic signal of the frequency interval with the center frequency f2 can be filtered. After an input signal enters the filter circuit through the input end of the filter circuit, when the input signal passes through the first filter branch and the second filter branch, harmonic signals in two frequency intervals with the center frequency of f1 and f2 in the input signal can be filtered to a ground wire, so that the filter function of the filter circuit is realized.

In another possible implementation, the first filtering branch includes a third inductance L3 and a third capacitance C3, and the second filtering branch includes a fourth inductance L4 and a fourth capacitance C4.

Referring to fig. 5, a first end of a third inductor L3 is connected to the first input terminal vin+ of the filter circuit, and a second end of the third inductor L3 is connected to a first end of a third capacitor C3; the first end of the third capacitor C3 is an intermediate node N1 of the first filtering branch, and the second end of the third capacitor C3 is connected with the second input end Vin-of the filtering circuit; the first end of the fourth inductor L4 is connected with the first end of the third inductor L3 and the first output end Vout+ of the filter circuit, and the second end of the fourth inductor L4 is connected with the first end of the fourth capacitor C4; the first end of the fourth capacitor C4 is an intermediate node N2 of the second filtering branch, and the second end of the fourth capacitor C4 is connected with the second end of the third capacitor C3 and the second output end Vout of the filtering circuit.

In practical application, in the structures of the first filtering branch and the second filtering branch shown in fig. 5, the resonant frequency of the first filtering branch isCan filter harmonic signals in a frequency interval with the center frequency f1Number (x). The resonance frequency of the second filter branch is +.>The harmonic signal of the frequency interval with the center frequency f2 can be filtered. Therefore, after the input signal enters the filter circuit through the input end of the filter circuit, when the input signal passes through the first filter branch and the second filter branch, harmonic signals in two frequency intervals with the center frequency of f1 and f2 in the input signal can be respectively filtered to the ground wire, so that the filter function of the filter circuit is realized.

It should be understood that, although the first filtering branch and the second filtering branch shown in fig. 4 and fig. 5 use the same filtering device, and only the positions of the capacitor and the inductor are replaced, the filtering devices used for forming a new filtering path by the filtering branch and the third filtering branch are different, and correspondingly, the filtering ranges of the filtering paths are also different.

Next, the filtering ranges of the filtering circuits under the structures of the first filtering branch and the second filtering branch shown in fig. 4 and fig. 5 are described with reference to the structure of the third filtering branch.

Referring to fig. 6, taking the first filtering branch and the second filtering branch shown in fig. 4 as an example, a fifth capacitor C5 may be included in the third filtering branch. The first end of the fifth capacitor C5 is connected to the intermediate node N1 of the first filtering branch, and the second end of the fifth capacitor C5 is connected to the intermediate node N2 of the second filtering branch.

With continued reference to fig. 6, the third filtering branch, the first filtering branch and the second filtering branch may form two filtering paths, where the first filtering path is formed by a first capacitor C1, a fifth capacitor C5 and a second inductor L2, and the resonant frequency of the filtering paths isThe harmonic signal of the frequency interval with the center frequency f3 can be filtered. The second filter path is composed of a second capacitor C2, a fifth capacitor C5 and a first inductor L1, and the resonance frequency of the second filter path isThe harmonic signal of the frequency interval with the center frequency f4 can be filtered. Therefore, when the input signal passes through the filter circuit, not only the harmonic signals of the two frequency intervals with the center frequencies f1 and f2, but also the harmonic signals of the two frequency intervals with the center frequencies f3 and f4 can be filtered, so that the purpose of increasing the filter range of the filter circuit is realized. The harmonic signal waveform filtered by the filter circuit can be seen in fig. 7.

In practical application, the filter circuit shown in fig. 6 increases the filter range by bridging a capacitor between two filter branches, and since the filter circuit adopts LC resonance principle to realize the filter function, the filter range of the filter circuit can also be increased by bridging an inductor between two filter branches. For example, referring to fig. 8, a fifth inductor L5 may be included in the third filtering branch, where a first end of the fifth inductor L5 is connected to the intermediate node N1 of the first filtering branch, and a second end of the fifth inductor L5 is connected to the intermediate node N2 of the second filtering branch.

With continued reference to fig. 8, the third filtering branch, the first filtering branch and the second filtering branch may form two filtering paths, where the first filtering path is formed by a first capacitor C1, a fifth inductor L5 and a second inductor L2, and the resonant frequency of the filtering paths isThe harmonic signal of the frequency interval with the center frequency f3 can be filtered. The second filtering path is composed of a second capacitor C2, a fifth inductor L5 and a first inductor L1, and the resonant frequency of the second filtering path isThe harmonic signal of the frequency interval with the center frequency f4 can be filtered. Therefore, when the input signal passes through the filter circuit, not only the harmonic signals of the two frequency intervals with the center frequencies f1 and f2, but also the harmonic signals of the two frequency intervals with the center frequencies f3 and f4 can be filtered, so that the effect of increasing the filter range of the filter circuit is realized.

Fig. 6 to 8 are filter paths and filter ranges generated by the third filter branch and the other two filter branches under the first filter branch and the second filter branch shown in fig. 4. Next, taking the first filtering branch and the second filtering branch shown in fig. 5 as an example, different filtering paths and different filtering ranges generated by the third filtering branch and the other two filtering branches will be described.

Referring to fig. 9, taking the first filtering branch and the second filtering branch shown in fig. 5 as an example, a fifth capacitor C5 may be included in the third filtering branch, where a first end of the fifth capacitor C5 is connected to the intermediate node N1 of the first filtering branch, and a second end of the fifth capacitor C5 is connected to the intermediate node N2 of the second filtering branch.

Referring to fig. 9, the third filtering branch, the first filtering branch and the second filtering branch may form two filtering paths, the first filtering path is formed by a third inductor L3, a fifth capacitor C5 and a fourth capacitor C4, and the resonant frequency of the filtering paths isThe harmonic signal of the frequency interval with the center frequency f3 can be filtered. The second filtering path is composed of a fourth inductor L4, a fifth capacitor C5 and a third capacitor C3, and the resonant frequency of the second filtering path is The harmonic signal of the frequency interval with the center frequency f4 can be filtered. Therefore, when the input signal passes through the filter circuit, not only the harmonic signals of the two frequency intervals with the center frequencies f1 and f2, but also the harmonic signals of the two frequency intervals with the center frequencies f3 and f4 can be filtered, so that the purpose of increasing the filter range of the filter circuit is realized.

In practical application, the filter circuit shown in fig. 9 increases the filtering range by bridging a capacitor between two filter branches, and since the filter circuit adopts LC resonance to realize the filtering function, the filter circuit can also increase the filtering range by bridging an inductor between two filter branches. For example, referring to fig. 10, the third filtering branch may include a fifth inductor L5, where a first end of the fifth inductor L5 is connected to the intermediate node N1 of the first filtering branch, and a second end of the fifth inductor L5 is connected to the intermediate node N2 of the second filtering branch.

Referring to fig. 10, the third filtering branch, the first filtering branch and the second filtering branch may form two filtering paths, the first filtering path is formed by a third inductor L3, a fifth inductor L5 and a fourth capacitor C4, and the resonant frequency of the filtering paths is The harmonic signal of the frequency interval with the center frequency f3 can be filtered. The second filtering path is composed of a fourth inductor L4, a fifth inductor L5 and a third capacitor C3, and the resonance frequency of the second filtering path is +.>The harmonic signal of the frequency interval with the center frequency f4 can be filtered. Therefore, when the input signal passes through the filter circuit, not only the harmonic signals of the two frequency intervals with the center frequencies f1 and f2, but also the harmonic signals of the two frequency intervals with the center frequencies f3 and f4 can be filtered, so that the effect of increasing the filter range of the filter circuit is realized.

In practical application, referring to fig. 6 to 10, the structure of the filter circuit is similar to an H-type filter architecture, and if harmonic signals exceeding the filter range exist in the electronic device, the filter range of the filter circuit can be further increased by adopting a cascade connection manner of a plurality of H-type filter architectures, so as to meet the filter requirement of the electronic device.

Next, a mode in which the H-type filter architecture cascade increases the filter range of the filter circuit will be described with reference to an embodiment.

Example 1

In the filtering circuit, at least one fourth filtering branch and at least one fifth filtering branch may be further included in addition to the first filtering branch, the second filtering branch and the third filtering branch. Wherein, at least one fourth filtering branch is in one-to-one correspondence with at least one fifth filtering branch. Each fourth filtering branch is connected in parallel with the first filtering branch and the second filtering branch. The first end of each fifth filtering branch is connected with the middle node of the corresponding fourth filtering branch, the second end of each fifth filtering branch is connected with the middle node of any filtering branch except the corresponding fourth filtering branch in the filtering circuit, and the filtering branch connected with the second end of each fifth filtering branch is connected with the corresponding fourth filtering branch in parallel.

It should be appreciated that the fourth filtering branch is connected in parallel with the first filtering branch and the second filtering branch and can be used as a filtering path alone, so that the fourth filtering branch at least comprises an inductor and a capacitor. In addition, the fifth filtering branch is bridged between the intermediate nodes of the two filtering branches and forms a filtering path with the two bridged filtering branches, and the two bridged filtering branches are provided with filtering devices, so that the fifth filtering branch can only comprise a capacitor or an inductor in order to reduce the cost of the filtering circuit.

In practical application, each fifth filtering branch is bridged between the corresponding fourth filtering branch and the middle node of the other filtering branch, and the three filtering branches can form an H-shaped filtering framework, and harmonic signals with specific frequency in input signals are filtered by configuring parameters of filtering devices in the filtering branches, so that the filtering range of the filtering circuit is enlarged. In addition, a plurality of H-shaped filter structures can also form a new filter path. For example, referring to fig. 11, each fourth filtering branch includes an inductor and a capacitor, and each fifth filtering branch includes a capacitor. The structures of the first filtering branch, the second filtering branch and the third filtering branch can be seen in fig. 9.

With continued reference to fig. 11, taking the fourth filtering branch formed by the inductor L6 and the capacitor C4 and the fifth filtering branch formed by the capacitor C7 as an example, besides the four filtering paths corresponding to the H-type filtering structure, the third inductor L3, the fifth capacitor C5, the capacitor C7 and the capacitor C6 may also form a new filtering path, and the inductor L6, the capacitor C7, the fifth capacitor C5 and the third capacitor C3 may also form a new filtering path. It should be noted that, the two filtering paths are formed by two H-type filtering architectures, and three or more H-type filtering architectures may be adopted to form more filtering paths, which are not described in the embodiments of the present application.

It should be noted that, fig. 11 is an example of a topology structure of a filter circuit under an H-filter architecture cascade, and in practical application, the filter circuit may have a plurality of circuit topologies according to selection and connection positions of capacitance and inductance devices in the filter branches, which is not described herein.

Example two

In the filter circuit, besides the first filter branch, the second filter branch and the third filter branch, at least one sixth filter branch is connected in series between the first filter branch and the second access end of the filter circuit, at least one seventh filter branch is connected in series between the second filter branch and the second output end of the filter circuit, wherein the at least one sixth filter branch corresponds to the at least one seventh filter branch one by one, and the first end of each sixth filter branch is connected with the first end of the corresponding seventh filter branch through one eighth filter branch.

Specifically, the sixth filtering branch is connected in series with the first filtering branch and forms a filtering path reaching the ground line, and the seventh filtering branch is connected in series with the second filtering branch and forms a filtering path reaching the ground line, and in order to reduce the cost of the filtering circuit, the sixth filtering branch and the seventh filtering branch can only comprise one capacitor or one inductor because the capacitors and the inductors are already included in the first filtering branch and the second filtering branch. In addition, the eighth filtering branch is bridged between the first end of the sixth filtering branch and the first end of the seventh filtering branch, and because the plurality of sixth filtering branches and the plurality of seventh filtering branches are connected in series, one end of the eighth filtering branch can be regarded as being connected to the intermediate node of two adjacent sixth filtering branches, and the other end of the eighth filtering branch is connected to the intermediate node of two adjacent seventh filtering branches, and an H-shaped filtering architecture is formed.

In practical application, the same filter device or different filter devices can be adopted in two adjacent sixth filter branches. In order to increase the filtering range of the filtering circuit, in the embodiment of the present application, different filtering devices are preferably selected from the two adjacent sixth filtering branches. Similarly, the same filter device or different filter devices may be used in two adjacent seventh filter branches. In order to increase the filtering range of the filtering circuit, in the embodiment of the present application, different filtering devices are preferably selected from the two adjacent seventh filtering branches.

Next, a description will be given of a filter path of the filter circuit taking an example in which two adjacent sixth filter branches and seventh filter branches respectively include different filter devices.

In an example, referring to fig. 12, a first filter branch includes a first capacitor C1 and a first inductor L1, a second filter branch includes a second capacitor C2 and a second inductor L2, and a third filter branch includes a fifth capacitor C5. In addition to the three filtering branches, the filtering circuit further includes a sixth filtering branch, a plurality of seventh filtering branches, and a plurality of eighth filtering branches. The first sixth filtering branch connected in series with the first filtering branch comprises a capacitor C6, the first seventh filtering branch connected in series with the second filtering branch comprises a capacitor C7, and an eighth filtering branch formed by a capacitor C8 is connected between the first end of the capacitor C6 and the first end of the capacitor C7 in a bridging mode. The second filtering branch connected in series with the first filtering branch comprises an inductor L6, the second seventh filtering branch connected in series with the second filtering branch comprises an inductor L7, and an eighth filtering branch formed by a capacitor C9 is connected between the first end of the inductor L6 and the first end of the inductor L7 in a bridging mode. And the like until the last sixth filtering branch is connected in series between the first filtering branch and the second input end of the filtering circuit, and the last seventh filtering branch is connected in series between the second filtering branch and the second output end of the filtering circuit.

With continued reference to fig. 12, the first capacitor C1 and the first inductor L1 in the first filtering branch may form a filtering path with a plurality of sixth filtering branches connected in series, and the second capacitor C2 and the plurality of inductors L2 in the second filtering branch may form a filtering path with a plurality of seventh filtering branches connected in series. The second filter leg and the eighth filter leg may form a plurality of filter paths with other filter legs. For example, the fifth capacitor C5 may form a filtering path with the first capacitor C1, the second inductor L2 and a plurality of seventh filtering branches connected in series, and the second capacitor C2, the fifth capacitor C5, the first inductor L1 and a plurality of sixth filtering branches connected in series form a filtering path. In addition to the above filtering paths, the fifth capacitor C5 may be combined with a capacitor bridged in the eighth filtering branch to form a new filtering path, for example, the first capacitor C1, the fifth capacitor C5, the second inductor L2, the eighth capacitor C8, and the plurality of serially connected sixth filtering branches form a filtering path, and the first capacitor C1, the fifth capacitor C5, the second inductor L2, the eighth capacitor C8, the sixth capacitor C6, the ninth capacitor C9, the seventh inductor L7, and the plurality of seventh filtering branches form a new filtering path. It should be noted that the filter circuit in the present application further has a plurality of filter paths, which are not described herein.

It should be noted that, fig. 12 is an example of a topology structure of a filter circuit under an H-type filter architecture cascade, and in practical application, the filter circuit may have a plurality of electrical topology structures according to the configuration of capacitance and inductance devices in the filter branch and the connection positions of the filter devices, which is not described herein.

In combination with the above description, for a plurality of filtering topological structure diagrams in the filtering circuit, when in practical application, after each filtering device in the filtering branch is configured, the filtering range of the filtering circuit is fixed. When the frequency of harmonic signals to be filtered changes due to the application scene change of electronic equipment connected with the filter circuit, the filter circuit cannot meet the filter requirement of the electronic equipment.

In practical application, the filtering circuit provided by the application realizes the filtering function through the LC resonance principle, so that the change of inductance and capacitance in the filtering circuit can realize the adjustment of the filtering range of the filtering circuit.

In one possible implementation, the adjusting of the filtering range of the filtering circuit may be achieved by adjusting a capacitance in the filtering path, in particular the first filtering branch and/or the second filtering branch may further comprise at least one first switch and at least one sixth capacitance.

Wherein, at least one first switch and at least one sixth electric capacity one-to-one. The first end of each first switch is connected with the first end of a capacitor in the filter branch, and the second end of each first switch is connected with the first end of a corresponding sixth capacitor; the second end of each sixth capacitor is connected with the second end of the capacitor in the filter branch.

The process of adjusting the filtering range of the filtering circuit will be described below by taking the first filtering branch including a first switch and a sixth capacitor as an example.

Referring to fig. 13, the first filtering branch includes a first switch K1 and a sixth capacitor C6 in addition to the first capacitor C1 and the first inductor L1, where the first switch K1 is connected in series with the sixth capacitor C6 and then connected in parallel with the first capacitor C1.

Referring to fig. 13, when the first switch K1 is turned off, the capacitance in the first filtering branch is C1. When the first switch K1 is turned on, the total capacitance in the first filter branch is C1// C6. Therefore, the capacitance value in the first filtering branch can be adjusted by controlling the on and off of the first switch K1, so as to adjust the resonance frequency of the filtering path and further change the filtering range of the filtering circuit.

It should be noted that, the filter circuit shown in fig. 13 is only illustrative, and a plurality of sixth capacitors and a first switch connected in series with the sixth capacitors may be disposed in the filter circuit, where each sixth capacitor selects the same or different capacitance value, and the filter range of the filter circuit is adjusted by controlling on or off of the first switch connected in series with the sixth capacitor.

In another possible implementation, adjusting the filtering range of the filtering circuit may be achieved by adjusting the inductance in the filtering path. In particular, the first filtering branch or the second filtering branch may further comprise at least one second switch and at least one sixth inductance.

Wherein, at least one second switch and at least one sixth inductance are in one-to-one correspondence. The first end of each second switch is connected with the first end of the inductor in the filter branch, and the second end of each second switch is connected with the first end of the corresponding sixth inductor; the second end of each sixth inductor is connected with the second end of the inductor in the filter branch.

The process of adjusting the filtering range of the filtering circuit will be described below by taking the first filtering branch including a first switch and a sixth inductor as an example.

Referring to fig. 14, the first filtering branch includes a second switch K2 and a sixth inductor L6 in addition to the first capacitor C1 and the first inductor L1, where the second switch K2 is connected in series with the sixth inductor L6 and then connected in parallel with the first inductor L1. When the second switch K2 is turned off, the inductance in the first filtering branch is L1. When the second switch K2 is turned on, the total inductance in the first filtering branch is L1// L6. Therefore, the inductance value in the first filtering branch circuit can be adjusted by controlling the on and off of the second switch K2, so that the resonance frequency of the filtering path is adjusted, and the filtering range of the filtering circuit is further changed.

It should be noted that, the filter circuit shown in fig. 14 is only schematic, and a plurality of sixth inductors and a second switch connected in series with the sixth inductors may be disposed in the filter circuit, where each sixth inductor has the same or different inductance value, and the filter range of the filter circuit is adjusted by controlling on or off of the second switch connected in series with the sixth inductor.

Based on the same conception, the embodiment of the application also provides a switching power supply, which comprises a switching circuit and the filtering circuit.

The first end of the switch circuit is connected with an external power supply, and the second end of the switch circuit is connected with the filter circuit. The filter circuit is used for being connected with a load, filtering the first voltage and outputting the first voltage to the load, wherein the rated voltage of the load is the first voltage.

In practical application, one or more switching devices are configured in a general switching circuit, and the power supply needs of the load are met by controlling the on or off of the switching devices to convert the alternating current or direct current output by the power supply into the first voltage required by the load. The switching device is frequently turned on and off to generate a plurality of harmonic signals with different frequencies, taking the power frequency alternating current of 50Hz as an example, the turning on and off of the switching device can lead to the generation of high-frequency signals with the frequency exceeding 50Hz in the output first voltage, and in order to eliminate the influence of the high-frequency signals on the normal work of a load, a filter circuit connected between the switching circuit and the load in a bridging way can carry out filter processing on the first voltage output by the switching circuit, so that the high-frequency signals carried in the first voltage are eliminated, and the normal operation of the load is ensured.

In an example, to control on and off of the switching device in the switching circuit, the switching circuit provided in the embodiment of the present application further includes a controller, where the controller is connected to the switching device in the switching circuit, and controls on and off of the switching device by providing a driving signal to the switching device.

In practice, the controller in the embodiments of the present application may be a central processing unit (CentralProcessing Unit, CPU), but also other general purpose processors, digital signal processors (DigitalSignal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field programmable gate arrays (Field Programmable Gate Array, FPGA) or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof.

It should be noted that, the filter circuit and the switching power supply in the embodiments of the present application may be implemented by separate devices, and may also be implemented by an integrated chip.

In the various embodiments of the application, if there is no specific description or logical conflict, terms and/or descriptions between the various embodiments are consistent and may reference each other, and features of the various embodiments may be combined to form new embodiments according to their inherent logical relationships.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.

Claims (11)

1. A filter circuit, comprising: the first filtering branch, the second filtering branch and the third filtering branch;

the first end of the first filtering branch is connected with the first input end of the filtering circuit, and the second end of the first filtering branch is connected with the second input end of the filtering circuit;

the second filtering branch is connected with the first filtering branch in parallel, the first end of the second filtering branch is connected with the first output end of the filtering circuit, and the second end of the second filtering branch is connected with the second output end of the filtering circuit;

the first end of the third filtering branch is connected with the middle node of the first filtering branch, and the second end of the third filtering branch is connected with the middle node of the second filtering branch.

2. The circuit of claim 1, wherein the first filtering leg comprises a first capacitance and a first inductance, and the second filtering leg comprises a second capacitance and a second inductance;

The first end of the first capacitor is connected with the first input end of the filter circuit, and the second end of the first capacitor is connected with the first end of the first inductor;

the first end of the first inductor is an intermediate node of the first filtering branch, and the second end of the first inductor is connected with the second input end of the filtering circuit;

the first end of the second capacitor is connected with the first end of the first capacitor and the first output end of the filter circuit, and the second end of the second capacitor is connected with the first end of the second inductor;

the first end of the second inductor is an intermediate node of the second filtering branch, and the second end of the second inductor is connected with the second end of the first inductor and the second output end of the filtering circuit.

3. The circuit of claim 1, wherein the first filtering leg comprises a third inductance and a third capacitance, and the second filtering leg comprises a fourth inductance and a fourth capacitance;

the first end of the third inductor is connected with the first input end of the filter circuit, and the second end of the third inductor is connected with the first end of the third capacitor;

the first end of the third capacitor is an intermediate node of the first filtering branch, and the second end of the third capacitor is connected with the second input end of the filtering circuit;

The first end of the fourth inductor is connected with the first end of the third inductor and the first output end of the filter circuit, and the second end of the fourth inductor is connected with the first end of the fourth capacitor;

the first end of the fourth capacitor is an intermediate node of the second filtering branch, and the second end of the fourth capacitor is connected with the second end of the third capacitor and the second output end of the filtering circuit.

4. A circuit according to claim 2 or 3, wherein the third filter branch comprises a fifth capacitor, a first end of the fifth capacitor being connected to the intermediate node of the first filter branch, and a second end of the fifth capacitor being connected to the intermediate node of the second filter branch.

5. A circuit according to claim 2 or 3, wherein the third filter leg comprises a fifth inductance, a first end of which is connected to the intermediate node of the first filter leg, and a second end of which is connected to the intermediate node of the second filter leg.

6. A circuit according to any one of claims 1 to 3, wherein the filter circuit further comprises: at least one fourth filtering branch and at least one fifth filtering branch; wherein the at least one fourth filtering branch corresponds to the at least one fifth filtering branch one-to-one:

Each fourth filtering branch is connected in parallel with the first filtering branch and the second filtering branch;

the first end of each fifth filtering branch is connected with the middle node of the corresponding fourth filtering branch, the second end of each fifth filtering branch is connected with the middle node of any filtering branch except the corresponding fourth filtering branch in the filtering circuit, and the filtering branch connected with the second end of each fifth filtering branch is connected with the corresponding fourth filtering branch in parallel.

7. A circuit according to any one of claims 1 to 3, wherein at least one sixth filtering branch is further connected in series between the first filtering branch and the second access terminal of the filtering circuit, and at least one seventh filtering branch is further connected in series between the second filtering branch and the second output terminal of the filtering circuit, wherein the at least one sixth filtering branch is in one-to-one correspondence with the at least one seventh filtering branch, and the first end of each sixth filtering branch is connected to the first end of the corresponding seventh filtering branch through an eighth filtering branch.

8. A circuit according to claim 2 or 3, wherein the first filtering branch and/or the second filtering branch further comprises: at least one first switch and at least one sixth capacitance; wherein the at least one first switch and the at least one sixth capacitor are in one-to-one correspondence:

The first end of each first switch is connected with the first end of a capacitor in the filter branch, and the second end of each first switch is connected with the first end of a corresponding sixth capacitor;

the second end of each sixth capacitor is connected with the second end of the capacitor in the filter branch.

9. A circuit according to claim 2 or 3, wherein the first filtering branch and/or the second filtering branch further comprises: at least one second switch and at least one sixth inductance; wherein the at least one second switch and the at least one sixth inductor are in one-to-one correspondence:

the first end of each second switch is connected with the first end of the inductor in the filter branch, and the second end of each second switch is connected with the first end of the corresponding sixth inductor;

the second end of each sixth inductor is connected with the second end of the inductor in the filter branch.

10. The circuit of claim 8 or 9, wherein the filter circuit further comprises a controller for controlling the on or off of a switch in a filter leg to adjust the total inductance or total capacitance in the filter leg.

11. A switching power supply, comprising: a switching circuit and a filter circuit as claimed in any one of claims 1 to 10;

The first end of the switching circuit is used for being connected with a power supply, the second end of the switching circuit is connected with the filter circuit, and the switching circuit is used for converting the voltage output by the power supply into a first voltage;

the filter circuit is used for being connected with a load, filtering the first voltage and outputting the first voltage to the load, and rated voltage of the load is the first voltage.