A filter circuit, a circuit board, and an earphone

Abstract

The application provides a filter circuit, a circuit board and an earphone. The circuit comprises a first processing circuit configured to perform high-frequency filtering on an input audio signal to be filtered and output a primary processed audio signal, and a second processing circuit comprising an AC / DC decomposition circuit and a first operational amplifier. The input end of the AC / DC decomposition circuit is connected to the output end of the first processing circuit. The first operational amplifier is input-connected to the AC output end and the DC output end of the AC / DC decomposition circuit respectively. The output end of the first operational amplifier is connected in parallel to the AC output end. The AC / DC decomposition circuit is configured to decompose the primary processed audio signal and output a target AC signal and a target DC signal. The first operational amplifier is configured to perform passband out-of-band gain adjustment on the target AC signal based on the target DC signal and output a target audio signal. The application can improve the low-pass filtering effect of the audio signal.

Description

Technical Field

[0001] This application relates to the field of headphone technology, and more particularly to a filter circuit, a circuit board, and a headphone. Background Technology

[0002] For headphones, in order to improve the sound quality of the audio being played, it is generally necessary to perform low-pass filtering on the audio signal being played. When the low-pass filter circuit responds slowly to the high-frequency components in the audio signal, it will affect the sound quality. Utility Model Content

[0003] The main objective of this application is to provide a filter circuit, circuit board, and earphone, which aims to improve the attenuation rate of the high-frequency component gain of the filter circuit, thereby enhancing the low-pass filtering effect of the audio signal.

[0004] To achieve the above objectives, a first aspect of this application provides a filter circuit, comprising:

[0005] The first processing circuit is used to perform high-frequency filtering on the input audio signal to be filtered and output the initially processed audio signal.

[0006] The second processing circuit includes an AC / DC decomposition circuit and a first operational amplifier. The input terminal of the AC / DC decomposition circuit is connected to the output terminal of the first processing circuit. The first operational amplifier is connected to both the AC output terminal and the DC output terminal of the AC / DC decomposition circuit. The output terminal of the first operational amplifier is connected in parallel with the AC output terminal. The AC / DC decomposition circuit is used to decompose and output a target AC signal and a target DC signal based on the initial processed audio signal. The first operational amplifier is used to perform out-of-band gain adjustment on the target AC signal based on the target DC signal and output the target audio signal.

[0007] In one embodiment, the first operational amplifier includes a first input terminal and a second input terminal;

[0008] The AC / DC decomposition circuit includes:

[0009] An AC decomposition circuit is connected to the output terminal and the first input terminal of the first processing circuit, and is also connected to the output terminal of the first operational amplifier. The AC decomposition circuit is used to decompose the initial processed audio signal and output the target AC signal.

[0010] A DC decomposition circuit is connected to the output terminal of the first processing circuit and the second input terminal. The DC decomposition circuit is used to decompose the initial processed audio signal and output the target DC signal.

[0011] In one embodiment, the DC decomposition circuit includes:

[0012] A DC decomposition resistor is connected between the output terminal of the first processing circuit and the second input terminal;

[0013] A DC filter capacitor is used to ground the second input terminal to filter the target DC signal.

[0014] In one embodiment, the second processing circuit further includes:

[0015] An output filtering circuit is connected to the output terminal of the first operational amplifier, and the output filtering circuit is used to perform high-frequency filtering on the target audio signal.

[0016] In one embodiment, there are multiple second processing circuits, which are connected in series.

[0017] In one embodiment, the first processing circuit includes:

[0018] A low-pass filter circuit is used to perform high-frequency filtering on the audio signal to be filtered.

[0019] Bias voltage input circuit, used to input bias voltage signal;

[0020] Capacitor feedback circuit;

[0021] The second operational amplifier includes a third input terminal and a fourth input terminal. The third input terminal is connected to the output terminal of the low-pass filter circuit, and the fourth input terminal is connected to the output terminal of the bias voltage input circuit. The output terminal of the second operational amplifier is connected in parallel with the output terminal of the low-pass filter circuit. The third input terminal is connected to the output terminal of the second operational amplifier through the capacitor feedback circuit. The second operational amplifier is used to amplify the filtered audio signal based on the bias voltage signal after high-frequency filtering, and output the initial processed audio signal.

[0022] In one embodiment, the first processing circuit further includes:

[0023] A passband adjustment circuit is connected to the output terminal of the low-pass filter circuit and the fourth input terminal. The passband adjustment circuit is used to adjust the passband width.

[0024] In one embodiment, the bias voltage input circuit includes:

[0025] A voltage divider circuit is used to divide the voltage signal to be divided and output the divided voltage signal.

[0026] The third operational amplifier includes a fifth input terminal and a sixth input terminal. The fifth input terminal is connected to the output terminal of the third operational amplifier, and the sixth input terminal is connected to the output terminal of the voltage divider circuit. The third operational amplifier is used to output the bias voltage signal based on the voltage divider signal.

[0027] To achieve the above objectives, a second aspect of this application provides a circuit board that includes the circuit described in the first aspect.

[0028] To achieve the above objectives, a third aspect of the present application provides an earphone, the earphone including the circuit board described in the second aspect above.

[0029] This application discloses a filtering circuit, a circuit board, and an earphone. The circuit includes a first processing circuit for performing high-frequency filtering on an input audio signal to be filtered and outputting a pre-processed audio signal. A second processing circuit includes an AC / DC decomposition circuit and a first operational amplifier. The input terminal of the AC / DC decomposition circuit is connected to the output terminal of the first processing circuit. The first operational amplifier is connected to both the AC and DC output terminals of the AC / DC decomposition circuit. The output terminal of the first operational amplifier is connected in parallel with the AC output terminal. The AC / DC decomposition circuit is used to decompose and output a target AC signal and a target DC signal based on the pre-processed audio signal. The first operational amplifier is used to perform out-of-band gain adjustment on the target AC signal based on the target DC signal and output the target audio signal. Because of the AC / DC decomposition circuit, the initial processed audio signal can be decomposed into a target AC signal and a target DC signal. In this way, the second processing circuit can adjust the out-of-band gain of the target AC signal based on the target DC signal through the first operational amplifier. In this process, the output terminal of the first operational amplifier is connected in parallel with the AC output terminal to form an adjustment feedback, which enables the out-of-band gain of the target AC signal to be adjusted quickly. This improves the attenuation rate of the high-frequency component gain, thereby enabling the filtering circuit to respond quickly to the high-frequency components in the audio signal to be filtered, which helps to improve the low-pass filtering effect of the audio signal. Attached Figure Description

[0030] Figure 1 This is a circuit structure diagram of a filter circuit provided in one embodiment of this application;

[0031] Figure 2 yes Figure 1 A circuit diagram of one embodiment of the second processing circuit in the circuit;

[0032] Figure 3 yes Figure 1 A circuit diagram of another embodiment of the second processing circuit in the circuit;

[0033] Figure 4 yes Figure 1 A circuit diagram of one embodiment of the first processing circuit in the process;

[0034] Figure 5 yes Figure 1 A circuit diagram of another embodiment of the first processing circuit in the circuit;

[0035] Figure 6 This is a circuit structure diagram of the bias voltage input circuit 120 provided in the embodiments of this application.

[0036] Figure label:

[0037] First processing circuit 100, low-pass filter circuit 110, bias voltage input circuit 120, voltage divider circuit 121, third operational amplifier 122, capacitor feedback circuit 130, second operational amplifier 140, passband adjustment circuit 150, second processing circuit 200, AC / DC decomposition circuit 210, AC decomposition circuit 211, DC decomposition circuit 212, DC decomposition resistor 2121, DC filter capacitor 2122, first operational amplifier 220, output filter circuit 230. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0041] For headphones, in order to improve the sound quality of the audio being played, it is generally necessary to perform low-pass filtering on the audio signal being played. When the low-pass filter circuit responds slowly to the high-frequency components in the audio signal, it will affect the sound quality.

[0042] To improve the attenuation rate of high-frequency components in the filtering circuit and enhance the low-pass filtering effect of the audio signal, this application provides a filtering circuit, a circuit board, and headphones. The circuit includes a first processing circuit for performing high-frequency filtering on the input audio signal to be filtered and outputting a pre-processed audio signal. The second processing circuit includes an AC / DC decomposition circuit and a first operational amplifier. The input terminal of the AC / DC decomposition circuit is connected to the output terminal of the first processing circuit. The first operational amplifier is connected to the AC output terminal and the DC output terminal of the AC / DC decomposition circuit respectively. The output terminal of the first operational amplifier is connected in parallel with the AC output terminal. The AC / DC decomposition circuit is used to decompose and output a target AC signal and a target DC signal based on the pre-processed audio signal. The first operational amplifier is used to adjust the out-of-band gain of the target AC signal based on the target DC signal and output the target audio signal. Because of the AC / DC decomposition circuit, the initial processed audio signal can be decomposed into a target AC signal and a target DC signal. In this way, the second processing circuit can adjust the out-of-band gain of the target AC signal based on the target DC signal through the first operational amplifier. In this process, the output terminal of the first operational amplifier is connected in parallel with the AC output terminal to form an adjustment feedback, which enables the out-of-band gain of the target AC signal to be adjusted quickly. This improves the attenuation rate of the high-frequency component gain, thereby enabling the filtering circuit to respond quickly to the high-frequency components in the audio signal to be filtered, which helps to improve the low-pass filtering effect of the audio signal.

[0043] See Figure 1 , Figure 1 A circuit diagram of a filtering circuit according to an embodiment of this application is shown. In this embodiment, the filtering circuit may include a first processing circuit 100 and a second processing circuit 200. The first processing circuit 100 can be used to perform high-frequency filtering on the input audio signal to be filtered and output a pre-processed audio signal. The second processing circuit 200 may include an AC / DC decomposition circuit 210 and a first operational amplifier 220. The input terminal of the AC / DC decomposition circuit 210 is connected to the output terminal of the first processing circuit 100. The first operational amplifier 220 is connected to the AC output terminal and the DC output terminal of the AC / DC decomposition circuit 210 respectively. The output terminal of the first operational amplifier 220 is connected in parallel with the AC output terminal. The AC / DC decomposition circuit 210 can be used to decompose and output a target AC signal and a target DC signal according to the pre-processed audio signal. The first operational amplifier 220 can be used to perform out-of-band gain adjustment on the target AC signal based on the target DC signal and output the target audio signal.

[0044] Specifically, for the filtering circuit, the audio signal to be filtered is input into the first processing circuit 100 from its input terminal. The first processing circuit 100 performs high-frequency filtering on the audio signal and outputs a pre-processed audio signal that has undergone low-pass filtering. Since the output of the first processing circuit 100 is short-connected to the AC / DC decomposition circuit 210, the pre-processed audio signal output by the first processing circuit 100 will be input into the AC / DC decomposition circuit 210. The AC / DC decomposition circuit 210 decomposes the pre-processed audio signal into AC and DC signals, obtaining a target AC signal and a target DC signal. The target AC signal is output from the AC output terminal of the AC / DC decomposition circuit 210 to the first operational amplifier 220, and the target DC signal is output from the DC output terminal of the AC / DC decomposition circuit 210 to the first operational amplifier 220. The target DC signal serves as the bias signal for the first operational amplifier 220, enabling the first operational amplifier 220 to amplify the target AC signal and output the target audio signal. During this process, since the output terminal of the first operational amplifier 220 is connected in parallel with the AC output terminal, a negative feedback path is formed in the second processing circuit 200. The negative feedback path can improve the closed-loop gain of the second processing circuit 200, thereby improving the attenuation of high-frequency gain and improving the selectivity of the bandwidth of the first processing circuit 100.

[0045] In one embodiment, the output terminal of the first operational amplifier 220 and the AC output terminal can be connected in parallel by a pure line, an RC series circuit, a pure resistor circuit, etc., and no specific limitation is made here.

[0046] In one embodiment, the first operational amplifier 220 may be a specific model such as SGM8429C or LT1210, but no specific limitation is made here.

[0047] In one embodiment, the first processing circuit 100 may be a low-pass filter circuit formed only by electronic components such as resistors, capacitors, and inductors, or it may be an operational amplifier and peripheral circuits with high-frequency filtering capabilities forming the first processing circuit 100, etc. The specific details are not limited here.

[0048] See Figure 2 In one embodiment, the first operational amplifier 220 may include a first input terminal and a second input terminal, and the AC / DC decomposition circuit 210 may include an AC decomposition circuit 211 and a DC decomposition circuit 212. The AC decomposition circuit 211 is connected to the output terminal and the first input terminal of the first processing circuit 100, and is also connected to the output terminal of the first operational amplifier 220. The AC decomposition circuit can be used to decompose the initially processed audio signal and output a target AC signal. The DC decomposition circuit 212 is connected to the output terminal and the second input terminal of the first processing circuit 100, and can be used to decompose the initially processed audio signal and output a target DC signal.

[0049] In one embodiment, the first input terminal can be either the non-inverting input terminal or the inverting input terminal of the first operational amplifier 220, and the second input terminal corresponding to the first input terminal can be either the inverting input terminal or the non-inverting input terminal of the first operational amplifier 220.

[0050] In one embodiment, the AC decomposition circuit 211 can be a capacitor circuit that blocks DC and passes AC, or a resistor circuit that is purely resistive, etc., and is not specifically limited here.

[0051] In one embodiment, the DC decomposition circuit 212 can be a purely resistive circuit, a bridge rectifier circuit, etc., and is not specifically limited here. It should be noted that the specific form of the AC decomposition circuit 211 must correspond to the specific form of the DC decomposition circuit 212. For example, when the AC decomposition circuit 211 is a capacitor circuit that blocks DC and passes AC, the DC decomposition circuit 212 can be a purely resistive circuit; when the AC decomposition circuit 211 is a purely resistive circuit, the DC decomposition circuit 212 can be a bridge rectifier circuit.

[0052] In one embodiment, the DC decomposition circuit 212 may include a DC decomposition resistor 2121 and a DC filter capacitor 2122. The DC decomposition resistor 2121 is connected to the output terminal and the second input terminal of the first processing circuit 100. The DC filter capacitor 2122 can be used to ground the second input terminal to filter the target DC signal. Specifically, the connection point between the DC filter capacitor 2122 and the second input terminal is grounded, thereby filtering out the ripple component in the target DC signal. This reduces the ripple component carried by the signal input to the first operational amplifier 220, improving the stability of the first operational amplifier 220 and making the out-of-band gain adjustment effect more stable.

[0053] See Figure 3 In one embodiment, the second processing circuit 200 may further include an output filter circuit 230, which is connected to the output terminal of the first operational amplifier 220. The output filter circuit 230 can be used to perform high-frequency filtering on the target audio signal. By setting the output filter circuit 230 at the output terminal of the first operational amplifier 220, high-frequency signals in the output target audio signal can be filtered out, thereby reducing the impact of high-frequency noise generated by the first operational amplifier 220 due to its device characteristics and improving the overall filtering effect of the filter circuit.

[0054] In one embodiment, the output filter circuit 230 can be a pure capacitor circuit, or a combination circuit of RC series / parallel circuits, etc., and is not specifically limited here.

[0055] In one embodiment, there are multiple second processing circuits 200, which are connected in series. When the multiple second processing circuits 200 are connected in series and connected to the output of the first operational amplifier 220, the output initial audio signal can undergo multiple out-of-band gain adjustments, thereby increasing the attenuation rate of the high-frequency gain and improving the filtering capability of the filter circuit for high-frequency signals.

[0056] See Figure 4 In one embodiment, the first processing circuit 100 may include a low-pass filter circuit 110, a bias voltage input circuit 120, a capacitor feedback circuit 130, and a second operational amplifier 140. The low-pass filter circuit 110 can be used to perform high-frequency filtering on the audio signal to be filtered. The bias voltage input circuit 120 is used to input a bias voltage signal. The second operational amplifier 140 may include a third input terminal and a fourth input terminal. The third input terminal is connected to the output terminal of the low-pass filter circuit 110, and the fourth input terminal is connected to the output terminal of the bias voltage input circuit 120. The output terminal of the second operational amplifier 140 is connected in parallel with the output terminal of the low-pass filter circuit 110. The third input terminal is connected to the output terminal of the second operational amplifier 140 through the capacitor feedback circuit 130. The second operational amplifier 140 can be used to amplify the high-frequency filtered audio signal based on the bias voltage signal and output a pre-processed audio signal.

[0057] Because of the low-pass filter circuit 110, when the audio signal to be filtered is input into the first processing circuit 100, the low-pass filter circuit 110 can perform low-pass filtering. The audio signal to be filtered with high-frequency components filtered out is amplified by the second operational amplifier 140 based on the bias voltage signal. Since the capacitor feedback circuit 130 is provided at the third input terminal, the high-frequency components can be filtered out again through negative feedback, so that the proportion of high-frequency components in the output initial processed audio signal can be reduced, thereby improving the low-pass filtering capability of the first processing circuit 100.

[0058] In one embodiment, the low-pass filter circuit 110 can be an RC series filter circuit, a filter circuit with multiple capacitors in series, etc., and is not specifically limited here.

[0059] In one embodiment, the bias voltage input circuit 120 can be connected to a pure wire path, a resistor path, or an external output bias voltage signal, or it can be a circuit that generates its own bias voltage signal (such as a combined circuit formed by a transformer and a bridge rectifier circuit), etc., and the specific details are not limited here.

[0060] In one embodiment, the third input terminal can be either the non-inverting input terminal or the inverting input terminal of the second operational amplifier 140, and the fourth input terminal corresponding to the third input terminal can be either the inverting input terminal or the non-inverting input terminal of the second operational amplifier 140.

[0061] In one embodiment, the capacitor feedback circuit 130 can be a pure capacitor circuit composed of one or more capacitors, or it can be a combined circuit composed of other components (such as capacitors, inductors, etc.), etc., and so on. No specific limitation is made here.

[0062] In one embodiment, the second operational amplifier 140 may be a specific model such as SGM8429C or LT1210, but no specific limitation is made here.

[0063] See Figure 5 In one embodiment, the first processing circuit 100 further includes a passband adjustment circuit 150, which is connected to the output terminal and the fourth input terminal of the low-pass filter circuit 110. The passband adjustment circuit 150 can be used to adjust the passband width. By setting the passband adjustment circuit 150 between the output terminal and the fourth input terminal of the low-pass filter circuit 110, the bandwidth can be limited, thereby improving the low-pass filtering capability of the first processing circuit 100.

[0064] In one embodiment, the passband adjustment circuit 150 can be a pure capacitor circuit formed by one or more capacitors, or it can be a combined circuit composed of other components (such as capacitors, inductors, etc.), etc., and so on. The specific design is not limited here. The capacitors in the passband adjustment circuit 150 can be capacitors with fixed capacitance values, or electronically adjustable capacitors, etc., and so on.

[0065] See Figure 6 In one embodiment, the bias voltage input circuit 120 may include a voltage divider circuit 121 and a third operational amplifier 122. The voltage divider circuit 121 can be used to divide the signal to be divided and output a divided voltage signal. The third operational amplifier 122 may include a fifth input terminal and a sixth input terminal. The fifth input terminal is connected to the output terminal of the third operational amplifier 122, and the sixth input terminal is connected to the output terminal of the voltage divider circuit 121. The third operational amplifier 122 can be used to output a bias voltage signal based on the divided voltage signal. Specifically, after the voltage divider circuit 121 divides the signal to be divided, since the fifth input terminal is connected to the output terminal of the third operational amplifier 122, the divided voltage signal can be amplified by the third operational amplifier 122 to output a bias voltage signal.

[0066] In one embodiment, the fifth input terminal can be either the non-inverting input terminal or the inverting input terminal of the third operational amplifier 122, and the sixth input terminal corresponding to the fifth input terminal can be either the inverting input terminal or the non-inverting input terminal of the third operational amplifier 122.

[0067] In one embodiment, the third operational amplifier 122 can be a specific model of operational amplifier such as SGM8429C, LT1210, or DIO32051A, and no specific limitation is made here.

[0068] In one embodiment, the voltage divider circuit 121 may consist of multiple resistors, and the third operational amplifier 122 may be connected to the junction point between two specific resistors to obtain a voltage-divided signal with a specific voltage value. Multiple grounding capacitors may be connected in parallel between the voltage path of the third operational amplifier 122 and the voltage divider circuit 121 to filter out ripple in the voltage-divided signal, making the voltage-divided signal input to the third operational amplifier 122 purer, thereby improving the reliability of the bias voltage input circuit 120.

[0069] A specific embodiment of this application is given below.

[0070] First processing circuit 100: Capacitor C41 and resistor R34 are connected in series to form a low-pass filter circuit 110. In the low-pass filter circuit 110, one end of capacitor C41 is used to input the audio signal to be filtered, and one end of resistor R34 is used to output the audio signal to be filtered after high-frequency filtering. One end of the output signal of resistor R34 is connected to the third input terminal (i.e., the inverting input terminal of U6-D) of the second operational amplifier 140 (i.e., U6-D in the figure) through resistor R35, and to the output terminal of the second operational amplifier 140 through resistor R42. Capacitor C42 is connected between the inverting input terminal and the output terminal of U6-D to form a capacitor feedback circuit 130. Capacitor C43 is connected between one end of the output signal of resistor R34 and the fourth input terminal (i.e., the non-inverting input terminal of U6-D) to form a bandwidth adjustment circuit 150.

[0071] Bias voltage input circuit 120: Resistors R16 and R55 are connected in series to form a voltage divider circuit 121. One end of resistor R16 is input to the voltage to be divided signal VBAT. The series connection of resistors R16 and R55 is electrically connected to the sixth input terminal (i.e., the positive input terminal of U12) of the third operational amplifier 122 (i.e., U12 in the figure). The fifth input terminal (i.e., the inverting input terminal of U12) of the third operational amplifier 122 is connected to the output terminal of U12. The output terminal of U12 is connected to the non-inverting input terminal of U6-D.

[0072] The second processing circuit 200 consists of: resistor R67 (also known as DC decomposition resistor 2121) coupled to the output terminal of U6-D via resistor R36 and connected to the second input terminal (also known as the positive input terminal of U6-A) of the first operational amplifier 220 (also known as U6-A in the figure); capacitor C67 (also known as DC filter capacitor 2122) grounding the positive input terminal of U6-A to form DC decomposition circuit 212; capacitor C66 coupled to the output terminal of U6-D via resistor R36 and connected to the first input terminal (also known as the inverting input terminal of U6-A) to form AC decomposition circuit 211; AC decomposition circuit 211 and DC decomposition circuit 212 are connected in parallel with resistor R36 to form AC / DC decomposition circuit 210; the output terminal and the inverting input terminal of U6-A are connected to form a feedback loop; resistor C44 forms output filter circuit 230 and is connected to the output terminal of U6-A.

[0073] The bias voltage input circuit 120 converts the voltage-divided signal VBAT into a bias voltage signal of 0.5VBAT (labeled as VBAT / 2 in the figure) and inputs it to the positive input terminal of U6-D. The audio signal to be filtered is input from the low-pass filter circuit 110 to the first processing circuit 100. The first processing circuit 100 performs low-pass filtering on the audio signal to be filtered and amplifies the signal based on the bias voltage signal of 0.5VBAT, outputting the initially processed audio signal to the AC / DC decomposition circuit 210. This allows the second processing circuit to attenuate and adjust the out-of-band gain of the initially processed audio signal and output the target audio signal.

[0074] In one aspect, this application also proposes a circuit board, which includes the circuits provided in any of the above embodiments. The specific implementation principle can be referred to the above embodiments, and will not be repeated here.

[0075] This application also proposes an earphone, which includes a circuit board as provided in the above embodiments. The specific implementation principle can be referred to the above embodiments, and will not be repeated here.

[0076] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of this application, and do not constitute a limitation on the technical solutions provided in this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided in this application are also applicable to similar technical problems.

[0077] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0078] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0079] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0080] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0081] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0082] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0083] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0084] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0085] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing programs, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0086] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A filter circuit, characterized in that, include: The first processing circuit is used to perform high-frequency filtering on the input audio signal to be filtered and output the initially processed audio signal. The second processing circuit includes an AC / DC decomposition circuit and a first operational amplifier. The input terminal of the AC / DC decomposition circuit is connected to the output terminal of the first processing circuit. The first operational amplifier is connected to both the AC output terminal and the DC output terminal of the AC / DC decomposition circuit. The output terminal of the first operational amplifier is connected in parallel with the AC output terminal. The AC / DC decomposition circuit is used to decompose and output a target AC signal and a target DC signal based on the initial processed audio signal. The first operational amplifier is used to perform out-of-band gain adjustment on the target AC signal based on the target DC signal and output the target audio signal.

2. The circuit according to claim 1, characterized in that, The first operational amplifier includes a first input terminal and a second input terminal; The AC / DC decomposition circuit includes: An AC decomposition circuit is connected to the output terminal and the first input terminal of the first processing circuit, and is also connected to the output terminal of the first operational amplifier. The AC decomposition circuit is used to decompose the initial processed audio signal and output the target AC signal. A DC decomposition circuit is connected to the output terminal of the first processing circuit and the second input terminal. The DC decomposition circuit is used to decompose the initial processed audio signal and output the target DC signal.

3. The circuit according to claim 2, characterized in that, The DC decomposition circuit includes: A DC decomposition resistor is connected between the output terminal of the first processing circuit and the second input terminal; A DC filter capacitor is used to ground the second input terminal to filter the target DC signal.

4. The circuit according to claim 1, characterized in that, The second processing circuit also includes: An output filtering circuit is connected to the output terminal of the first operational amplifier, and the output filtering circuit is used to perform high-frequency filtering on the target audio signal.

5. The circuit according to claim 1, characterized in that, There are multiple second processing circuits, which are connected in series.

6. The circuit according to claim 1, characterized in that, The first processing circuit includes: A low-pass filter circuit is used to perform high-frequency filtering on the audio signal to be filtered. Bias voltage input circuit, used to input bias voltage signal; Capacitor feedback circuit; The second operational amplifier includes a third input terminal and a fourth input terminal. The third input terminal is connected to the output terminal of the low-pass filter circuit, and the fourth input terminal is connected to the output terminal of the bias voltage input circuit. The output terminal of the second operational amplifier is connected in parallel with the output terminal of the low-pass filter circuit. The third input terminal is connected to the output terminal of the second operational amplifier through the capacitor feedback circuit. The second operational amplifier is used to amplify the filtered audio signal based on the bias voltage signal after high-frequency filtering, and output the initial processed audio signal.

7. The circuit according to claim 6, characterized in that, The first processing circuit further includes: A passband adjustment circuit is connected to the output terminal of the low-pass filter circuit and the fourth input terminal. The passband adjustment circuit is used to adjust the passband width.

8. The circuit according to claim 6, characterized in that, The bias voltage input circuit includes: A voltage divider circuit is used to divide the voltage signal to be divided and output the divided voltage signal. The third operational amplifier includes a fifth input terminal and a sixth input terminal. The fifth input terminal is connected to the output terminal of the third operational amplifier, and the sixth input terminal is connected to the output terminal of the voltage divider circuit. The third operational amplifier is used to output the bias voltage signal based on the voltage divider signal.

9. A circuit board, characterized in that, The circuit board includes the circuitry as described in any one of claims 1 to 8.

10. An earphone, characterized in that, Includes the circuit board as described in claim 9.

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