Filter circuit and filter

Abstract

The embodiment of the utility model provides a filter circuit and a filter. The filter circuit comprises a first common mode inductor and a first capacitor, the first common-mode inductor comprises a first coil and a second coil which are wound on a first magnetic core, the first end of the first coil is connected with the first input port, the second end of the first coil is connected with the first end of the first capacitor and the first end of the second coil, and the second end of the second coil is connected with the first output port; the second end of the first capacitor is connected with the second input port and the second output port. The size and weight of the filter circuit can be reduced, and the cost of the filter circuit is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a filtering circuit and a filter. Background Art

[0002] Differential-mode inductors are generally used to remove high-frequency electromagnetic interference components in the output current, stabilize the output voltage, and reduce the voltage ripple at the output end. When designing differential-mode inductors, it is important to prevent the occurrence of DC magnetic flux saturation. In order to prevent DC magnetic flux saturation in differential-mode inductors, a larger magnetic core needs to be designed, which means that the volume and weight of the inductor need to be increased, and the cost will also increase accordingly. Utility Model Content

[0003] The embodiments of the present application provide a filter circuit and a filter, which can reduce the volume and weight of the filter circuit and reduce the cost of the filter circuit.

[0004] A first aspect of an embodiment of the present application provides a filtering circuit, including a first common-mode inductor and a first capacitor; the first common-mode inductor includes a first coil and a second coil wound on a first magnetic core, the first end of the first coil is connected to a first input port, the second end of the first coil is connected to a first end of the first capacitor and a first end of the second coil, the second end of the second coil is connected to a first output port, and the second end of the first capacitor is connected to a second input port and a second output port.

[0005] In the embodiment of the present application, the first common-mode inductor is used to replace the differential-mode inductor. When the current flows through the first common-mode inductor, the DC component in the current generates opposite magnetic fields in the first coil and the second coil to offset the first part. The first common-mode inductor is not prone to DC magnetic flux saturation. Compared with the differential-mode inductor, the first magnetic core can be designed to be smaller, thereby reducing the volume and weight of the first common-mode inductor and reducing the cost of the filter circuit. In addition, the first capacitor causes a deviation between the current flowing through the first coil and the current flowing through the second coil, thereby allowing the first common-mode inductor to produce a filtering effect and realize the filtering function.

[0006] Optionally, the first common-mode inductor further includes a third coil wound on the first magnetic core, and the second end of the second coil is connected to the first output port through the third coil.

[0007] In the embodiment of the present application, a third coil is added, and the DC component in the current will not be completely offset in the first coil, the second coil and the third coil. The DC component will not be completely offset, and the number of turns of the third coil can be designed according to the output requirements of the output port.

[0008] Optionally, the filtering circuit also includes a second capacitor, the second end of the second coil is connected to the first end of the second capacitor and the first end of the third coil, the second end of the third coil is connected to the first output port, and the second end of the second capacitor is connected to the second end of the first capacitor.

[0009] In the embodiment of the present application, two capacitors can be connected to the first common-mode inductor, so that the filter circuit can filter out ripples of different frequencies and amplitudes.

[0010] Optionally, the sum of the number of turns of the second coil and the number of turns of the third coil is equal to the number of turns of the first coil.

[0011] In the embodiment of the present application, a first common-mode inductor is used to replace a differential-mode inductor. When current flows through the first common-mode inductor, the sum of the number of turns of the second coil and the number of turns of the third coil is equal to the number of turns of the first coil. Since the winding direction of the third coil and the second coil is the same, which is opposite to the winding direction of the first coil, the DC component in the current generates a magnetic field in the first coil and generates opposite magnetic fields in the second coil and the third coil, which completely cancel each other out. There is no need to worry about DC flux saturation in the first common-mode inductor. Compared with the differential-mode inductor, the first magnetic core can be designed to be smaller, thereby reducing the volume and weight of the first common-mode inductor and reducing the cost of the filter circuit.

[0012] Optionally, the filtering circuit also includes a second common-mode inductor; the second common-mode inductor includes a fourth coil and a fifth coil wound on a second magnetic core, and the second end of the first coil is connected to the first end of the first capacitor and the first end of the second coil through the fourth coil and the fifth coil.

[0013] In the embodiment of the present application, the first common mode inductor and the second common mode inductor are equivalent to being connected in series, and filtering is achieved by the first common mode inductor and the second common mode inductor, which is equivalent to two-stage filtering, thereby improving the filtering effect. With two common mode inductors, the DC cancellation effect is better.

[0014] Optionally, the filtering circuit also includes a third capacitor, the second end of the first coil is connected to the first end of the fourth coil, the second end of the fourth coil is connected to the first end of the fifth coil and the first end of the third capacitor, the second end of the fifth coil is connected to the first end of the first capacitor and the first end of the second coil, and the second end of the third capacitor is connected to the second end of the first capacitor.

[0015] In the embodiment of the present application, the filtering circuit also includes a third capacitor, which causes a deviation between the current flowing through the fourth coil and the current flowing through the fifth coil, thereby allowing the second common-mode inductor to produce a filtering effect and realize a filtering function.

[0016] Optionally, the filtering circuit further includes a fourth capacitor, a first end of the fourth capacitor is connected to the first end of the fourth coil, and a second end of the fourth capacitor is connected to the second end of the first capacitor.

[0017] In the embodiment of the present application, the filtering circuit also includes a fourth capacitor, which causes a deviation between the current flowing through the first coil and the current flowing through the fourth coil, so that the first common-mode inductor and the second common-mode inductor jointly produce a filtering effect to achieve a filtering function.

[0018] Optionally, the number of turns of the fourth coil is equal to the number of turns of the fifth coil.

[0019] In the embodiment of the present application, the first common-mode inductor and the second common-mode inductor are used to replace the differential-mode inductor. When the current flows through the second common-mode inductor, the fourth coil and the fifth coil have the same number of turns, and the DC component in the current generates opposite magnetic fields in the fourth coil and the fifth coil and completely cancels each other out. There is no need to worry about DC flux saturation in the second common-mode inductor. Compared with the differential-mode inductor, the second magnetic core can be designed to be smaller, thereby reducing the volume and weight of the second common-mode inductor and reducing the cost of the filter circuit.

[0020] A second aspect of the embodiments of the present application provides a filter, comprising the filter circuit described in any one of the first aspect of the embodiments of the present application.

[0021] Optionally, the filter also includes a fifth capacitor and a sixth capacitor, the first end of the fifth capacitor is connected to the first input port, and the second end of the fifth capacitor is connected to the second input port; the first end of the sixth capacitor is connected to the first output port, and the second end of the sixth capacitor is connected to the second output port.

[0022] The fifth capacitor is a filter capacitor arranged at the first input port and the second input port, and the sixth capacitor is a filter capacitor arranged at the first output port and the second output port. Filter capacitors are arranged at the input port and the output port of the filter respectively, so as to improve the filtering effect of the input signal and the output signal.

[0023] The filter circuit of the embodiment of the present application includes a first common-mode inductor and a first capacitor; the first common-mode inductor includes a first coil and a second coil wound on a first magnetic core, the first end of the first coil is connected to the first input port, the second end of the first coil is connected to the first end of the first capacitor and the first end of the second coil, the second end of the second coil is connected to the first output port, and the second end of the first capacitor is connected to the second input port and the second output port. In the embodiment of the present application, the first common-mode inductor is used to replace the differential-mode inductor. When the current flows through the first common-mode inductor, the DC component in the current generates opposite magnetic fields in the first coil and the second coil to offset the first part. The first common-mode inductor is not prone to DC flux saturation. Compared with the differential-mode inductor, the first magnetic core can be designed to be smaller, thereby reducing the volume and weight of the first common-mode inductor and reducing the cost of the filter circuit. In addition, the first capacitor causes the current flowing through the first coil and the current of the second coil to deviate, so that the first common-mode inductor produces a filtering effect to achieve a filtering function. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 is a structural schematic diagram of a filter circuit provided in an embodiment of the present application;

[0026] Figure 2 is a structural schematic diagram of another filter circuit provided in an embodiment of the present application;

[0027] Figure 3 is a structural schematic diagram of another filter circuit provided in an embodiment of the present application;

[0028] Figure 4 It is a schematic diagram of the structure of another filter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0030] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, products or devices.

[0031] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0032] See also Figure 1 , Figure 1 1 is a schematic diagram of the structure of a filter circuit 100 provided in an embodiment of the present application. Figure 1 As shown, the filter circuit 100 includes a first common-mode inductor 10 and a first capacitor C1; the first common-mode inductor 10 includes a first coil L1 and a second coil L2 wound on a first magnetic core T1, and a first end of the first coil L1 is connected to a first input port (such as Figure 1 The second end of the first coil L1 is connected to the first end of the first capacitor C1 and the first end of the second coil L2, and the second end of the second coil L2 is connected to the first output port (as shown in FIG. Figure 1 The output port 1 shown in FIG. 1 ), the second end of the first capacitor C1 is connected to the second input port (as shown in FIG. 1 ). Figure 1 The input port 2 shown) and the second output port (as shown Figure 1 Output port 2 shown).

[0033] In an embodiment of the present application, the first coil L1 and the second coil L2 of the first common-mode inductor 10 are wound on the same magnetic core, and the coil diameter and number of turns of the first coil L1 and the second coil L2 are the same, but the winding directions are opposite. Since a coil has two pins, the first common-mode inductor 10 will have 4 pins. In an embodiment of the present application, the two pins of the first common-mode inductor 10 are connected together and connected to the first capacitor C1. The first capacitor C1 is connected to the connection between the first coil L1 and the second coil L2. The first capacitor C1 causes the current flowing through the first coil L1 and the current of the second coil L2 to deviate, thereby allowing the first common-mode inductor 10 to produce a filtering effect and realize the filtering function.

[0034] The first input port and the second input port can input signals output by other devices (e.g., switching power supplies), and the first output port and the second output port can output signals filtered by the filter circuit 100. The signal can be a current signal or a voltage signal. The signals output by the first output port and the second output port can be given to electrical devices such as loads.

[0035] For example, for a differential mode inductor, if the current is 120A, the differential mode inductor needs to be designed not to saturate at 120A, so the differential mode inductor needs a larger magnetic core. For a common mode inductor, if the DC component in the current is 120A and the AC component is 20A, since the common mode inductor cancels out the DC component, it only needs to be designed not to saturate at 20A, so the common mode inductor only needs a smaller magnetic core, thereby reducing the volume and weight of the common mode inductor and reducing the cost of the filter circuit 100.

[0036] In the embodiment of the present application, the function of the differential mode inductor is realized by the first common mode inductor 10 and the first capacitor C1. The first common mode inductor 10 is used to replace the differential mode inductor. When the current flows through the first common mode inductor 10, the DC component in the current generates opposite magnetic fields in the first coil L1 and the second coil L2 to offset the first part. The first common mode inductor 10 is not prone to DC magnetic flux saturation. Compared with the differential mode inductor, the first magnetic core T1 can be designed to be smaller, thereby reducing the volume and weight of the first common mode inductor 10 and reducing the cost of the filter circuit 100. In addition, the first capacitor C1 causes the current flowing through the first coil L1 and the current flowing through the second coil L2 to deviate, so that the first common mode inductor 10 produces a filtering effect and realizes the filtering function.

[0037] Optionally, the first coil L1 and the second coil L2 have the same number of turns.

[0038] In the embodiment of the present application, the first common-mode inductor 10 is used to replace the differential-mode inductor. When current flows through the first common-mode inductor 10, the number of turns of the first coil L1 and the second coil L2 is the same, and the DC component in the current generates opposite magnetic fields in the first coil L1 and the second coil L2 and completely cancels each other out. There is no need to worry about DC magnetic flux saturation in the first common-mode inductor 10. Compared with the differential-mode inductor, the first magnetic core T1 can be designed to be smaller, thereby reducing the volume and weight of the first common-mode inductor 10 and reducing the cost of the filter circuit 100.

[0039] See also Figure 2 , Figure 2 It is a structural schematic diagram of another filtering circuit provided in an embodiment of the present application. Figure 2 is Figure 1 Based on Figure 2As shown, the filter circuit 100 further includes a third coil L3 wound on the first magnetic core T1 , and the second end of the second coil L2 is connected to the first output port through the third coil L3 .

[0040] The winding directions of the third coil L3 and the second coil L2 are the same.

[0041] In the embodiment of the present application, a third coil L3 is added, and the DC component in the current will not be completely offset in the first coil L1, the second coil L2 and the third coil L3. The DC component will not be completely offset, and the number of turns of the third coil L3 can be designed according to the output requirements of the output port.

[0042] Optional, such as Figure 2 As shown, the filtering circuit 100 also includes a second capacitor C2, the second end of the second coil L2 is connected to the first end of the second capacitor C2 and the first end of the third coil L3, the second end of the third coil L3 is connected to the first output port, and the second end of the second capacitor C2 is connected to the second end of the first capacitor C1.

[0043] In the embodiment of the present application, two capacitors may be connected to the first common-mode inductor 10 , so that the filter circuit 100 can filter out ripples of different frequencies and amplitudes.

[0044] Optional, such as Figure 2 As shown, the sum of the number of turns of the second coil L2 and the number of turns of the third coil L3 is equal to the number of turns of the first coil L1.

[0045] In the embodiment of the present application, the first common-mode inductor 10 is used to replace the differential-mode inductor. When current flows through the first common-mode inductor 10, the sum of the number of turns of the second coil L2 and the number of turns of the third coil L3 is equal to the number of turns of the first coil L1. Since the winding direction of the third coil L3 and the second coil L2 is the same, which is opposite to the winding direction of the first coil L1, the magnetic field generated by the DC component in the current in the first coil L1 and the opposite magnetic fields generated in the second coil L2 and the third coil L3 completely cancel each other out. There is no need to worry about DC flux saturation in the first common-mode inductor 10. Compared with the differential-mode inductor, the first magnetic core T1 can be designed to be smaller, thereby reducing the volume and weight of the first common-mode inductor 10 and reducing the cost of the filter circuit 100.

[0046] See also Figure 3 , Figure 3 It is a structural schematic diagram of another filtering circuit provided in an embodiment of the present application. Figure 3 is Figure 1 Based on Figure 3As shown, the filter circuit 100 also includes a second common-mode inductor; the second common-mode inductor includes a fourth coil L4 and a fifth coil L5 wound on the second magnetic core T2, and the second end of the first coil L1 is connected to the first end of the first capacitor C1 and the first end of the second coil L2 through the fourth coil L4 and the fifth coil L5.

[0047] In the embodiment of the present application, the first common mode inductor 10 and the second common mode inductor are equivalent to being connected in series, and filtering is achieved by the first common mode inductor 10 and the second common mode inductor, which is equivalent to two-stage filtering, thereby improving the filtering effect. With two common mode inductors, the DC cancellation effect is better.

[0048] Optional, such as Figure 3 As shown, the filtering circuit 100 also includes a third capacitor C3, the second end of the first coil L1 is connected to the first end of the fourth coil L4, the second end of the fourth coil L4 is connected to the first end of the fifth coil L5 and the first end of the third capacitor C3, the second end of the fifth coil L5 is connected to the first end of the first capacitor C1 and the first end of the second coil L2, and the second end of the third capacitor C3 is connected to the second end of the first capacitor C1.

[0049] In the embodiment of the present application, the filter circuit 100 further includes a third capacitor C3. The third capacitor C3 causes a deviation between the current flowing through the fourth coil L4 and the current flowing through the fifth coil L5, thereby allowing the second common mode inductor to produce a filtering effect, thereby achieving a filtering function.

[0050] Optional, such as Figure 3 As shown, the filter circuit 100 further includes a fourth capacitor C4, a first end of the fourth capacitor C4 is connected to the first end of the fourth coil L4, and a second end of the fourth capacitor C4 is connected to the second end of the first capacitor C1.

[0051] In the embodiment of the present application, the filtering circuit 100 also includes a fourth capacitor C4. The fourth capacitor C4 causes a deviation between the current flowing through the first coil L1 and the current flowing through the fourth coil L4, so that the first common-mode inductor 10 and the second common-mode inductor 20 can jointly produce a filtering effect to achieve a filtering function.

[0052] Optional, such as Figure 3 As shown, the number of turns of the fourth coil L4 is equal to the number of turns of the fifth coil L5.

[0053] In the embodiment of the present application, the first common-mode inductor 10 and the second common-mode inductor 20 are used to replace the differential-mode inductor. When the current flows through the second common-mode inductor, the fourth coil L4 and the fifth coil L5 have the same number of turns, and the DC component in the current generates opposite magnetic fields in the fourth coil L4 and the fifth coil L5 and completely cancels each other out. There is no need to worry about DC magnetic flux saturation in the second common-mode inductor. Compared with the differential-mode inductor, the second magnetic core T2 can be designed to be smaller, thereby reducing the volume and weight of the second common-mode inductor and reducing the cost of the filter circuit 100.

[0054] See also Figure 4 , Figure 4 Schematic diagram of a filter structure provided by an embodiment of the present application. Figure 4 As shown, the filter 1000 may include Figure 1 The filter circuit shown.

[0055] In the embodiment of the present application, the filter 1000 may include three ports: a first input port, a second input port, and a first output port (wherein the second input port and the second output port are connected, equivalent to one port), and the filter 1000 may be a three-port filter 1000.

[0056] Optional, such as Figure 4 As shown, the filter 1000 also includes a fifth capacitor C5 and a sixth capacitor C6, wherein the first end of the fifth capacitor C5 is connected to the first input port, and the second end of the fifth capacitor C5 is connected to the second input port; the first end of the sixth capacitor C6 is connected to the first output port, and the second end of the sixth capacitor C6 is connected to the second output port.

[0057] In the embodiment of the present application, the fifth capacitor C5 is a filter capacitor arranged at the first input port and the second input port, and the sixth capacitor C6 is a filter capacitor arranged at the first output port and the second output port. Filter capacitors are arranged at the input port and the output port of the filter 1000, respectively, so as to improve the filtering effect of the input signal and the output signal.

[0058] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0059] In the several embodiments provided in the present application, it should be understood that the disclosed filter circuit can be implemented in other ways. For example, the filter circuit embodiments described above are only schematic, and the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

Claims

1. A filter circuit, characterized in that: It includes a first common-mode inductor and a first capacitor; the first common-mode inductor includes a first coil and a second coil wound on a first magnetic core, the first end of the first coil is connected to a first input port, the second end of the first coil is connected to a first end of the first capacitor and a first end of the second coil, the second end of the second coil is connected to a first output port, and the second end of the first capacitor is connected to a second input port and a second output port.

2. The filter circuit according to claim 1, characterized in that: The first common-mode inductor further includes a third coil wound on the first magnetic core, and the second end of the second coil is connected to the first output port through the third coil.

3. The filter circuit according to claim 2, characterized in that: The filtering circuit also includes a second capacitor, a second end of the second coil is connected to the first end of the second capacitor and the first end of the third coil, a second end of the third coil is connected to the first output port, and a second end of the second capacitor is connected to the second end of the first capacitor.

4. The filter circuit according to claim 3, characterized in that: The sum of the number of turns of the second coil and the number of turns of the third coil is equal to the number of turns of the first coil.

5. The filter circuit according to claim 1, characterized in that: The filtering circuit also includes a second common-mode inductor; the second common-mode inductor includes a fourth coil and a fifth coil wound on a second magnetic core, and the second end of the first coil is connected to the first end of the first capacitor and the first end of the second coil through the fourth coil and the fifth coil.

6. The filter circuit according to claim 5, characterized in that: The filtering circuit also includes a third capacitor, the second end of the first coil is connected to the first end of the fourth coil, the second end of the fourth coil is connected to the first end of the fifth coil and the first end of the third capacitor, the second end of the fifth coil is connected to the first end of the first capacitor and the first end of the second coil, and the second end of the third capacitor is connected to the second end of the first capacitor.

7. The filter circuit according to claim 6, characterized in that: The filter circuit further includes a fourth capacitor, a first end of the fourth capacitor is connected to the first end of the fourth coil, and a second end of the fourth capacitor is connected to the second end of the first capacitor.

8. The filter circuit according to claim 5, characterized in that: The number of turns of the fourth coil is equal to the number of turns of the fifth coil.

9. A filter, characterized in that: The invention comprises the filter circuit as claimed in any one of claims 1 to 8.

10. The filter according to claim 9, characterized in that The filter also includes a fifth capacitor and a sixth capacitor, wherein the first end of the fifth capacitor is connected to the first input port, and the second end of the fifth capacitor is connected to the second input port; the first end of the sixth capacitor is connected to the first output port, and the second end of the sixth capacitor is connected to the second output port.

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