CN219802294U

CN219802294U - Filter circuit and filter

Info

Publication number: CN219802294U
Application number: CN202321174568.6U
Authority: CN
Inventors: 俞雯超; 田敏
Original assignee: Suzhou HYC Technology Co Ltd
Current assignee: Suzhou HYC Technology Co Ltd
Priority date: 2023-05-16
Filing date: 2023-05-16
Publication date: 2023-10-03
Anticipated expiration: 2033-05-16

Abstract

The utility model relates to a filter circuit and a filter, the filter circuit includes: an input interface; the first filtering modules comprise filtering input ends, filtering output ends, first filtering units and second filtering units, the plurality of first filtering modules are arranged in a cascading mode, the filtering input ends of the first filtering modules of the first stage are connected with the input interface, the filtering output ends of the first filtering modules of the previous stage are connected with the filtering input ends of the first filtering modules of the next stage, in the same first filtering module, the input ends of the first filtering units are connected with the filtering input ends, the output ends of the second filtering units are connected with the filtering output ends, and the second filtering units are used for separating and filtering signals filtered by the first filtering units and outputting the separated and filtered signals by the filtering output ends; and the output interface is connected with the filtering output end of the final stage of the first filtering module.

Description

Filter circuit and filter

Technical Field

The present utility model relates to the field of filter circuits, and in particular, to a filter circuit and a filter.

Background

Before testing the audio signal, the unwanted signals need to be filtered out, leaving the target signal. Existing filter devices often include a bulky isolation housing. In the audio chip output test, a high-precision filter device is difficult to be embedded into an audio chip output test system under the condition of space limitation.

Disclosure of Invention

Based on this, it is necessary to provide a filter circuit and a filter which are small in size and high in accuracy. Wherein the filter circuit includes:

an input interface;

the first filtering modules comprise filtering input ends, filtering output ends, first filtering units and second filtering units, the plurality of first filtering modules are arranged in a cascading mode, the filtering input ends of the first filtering modules of the first stage are connected with the input interface, the filtering output ends of the first filtering modules of the previous stage are connected with the filtering input ends of the first filtering modules of the next stage, in the same first filtering module, the input ends of the first filtering units are connected with the filtering input ends, the output ends of the second filtering units are connected with the filtering output ends, and the second filtering units are used for separating and filtering signals filtered by the first filtering units and outputting the separated and filtered signals by the filtering output ends;

and the output interface is connected with the filtering output end of the final stage of the first filtering module.

In one embodiment, in the same first filtering module, the first filtering unit includes a first capacitor, one end of the first capacitor is connected to the filtering input end, the other end of the first capacitor is grounded, and the input end of the second filtering unit is connected to the input end of the first filtering unit.

In one embodiment, the second filtering unit includes a first filtering branch and a second filtering branch that are disposed in parallel, and the first filtering branch and the second filtering branch are respectively used for filtering signals in different wavebands.

In one embodiment, the first filter leg comprises a first resistor and the second filter leg comprises an inductor.

In one embodiment, the filter circuit further comprises:

and the input end of the second filtering module is connected with the output end of the final stage first filtering module, and the output end of the second filtering module is connected with the output interface.

In one embodiment, the second filter module includes a second capacitor and a second resistor, one end of the second capacitor is connected to the output end of the final stage first filter module, the other end of the second capacitor is grounded, and two ends of the second resistor are respectively connected to the output end of the final stage first filter module and the output interface.

In one embodiment, the filter circuit includes:

the input end of the voltage adjusting unit is connected with the input interface, and the output end of the voltage adjusting unit is connected with the filtering input end of the first filtering module of the first stage.

In one embodiment, the voltage adjustment unit includes: the first resistor unit and the second resistor unit are arranged in parallel, the first resistor unit comprises a third resistor, the second resistor unit comprises a fourth resistor, a fifth resistor and a variable resistor, and the fourth resistor is connected in parallel with the fifth resistor and then connected in series with the variable resistor.

In one embodiment, the filtering circuit includes a plurality of input interfaces and a plurality of output interfaces, and the plurality of first filtering modules are disposed between each of the input interfaces and the output interfaces.

Based on same conception, provide a wave filter, including balancing weight, box and circuit board, balancing weight and circuit board all set up in the box, the integrated foretell filter circuit of circuit board, the box includes: a first opening exposing the input interface and a second opening exposing the output interface.

According to the filter circuit and the filter, the audio signals input by the input interface are filtered for multiple times by the first filter unit and the second filter unit through the first filter modules which are arranged in a cascading mode, and finally signals of a target wave band are reserved. The filter circuit and the filter are small in size, and the accuracy of the filtered signals is high.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present utility model, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of an audio test system according to an embodiment;

FIG. 2 is a schematic diagram of a filter according to an embodiment;

FIG. 3 is a schematic diagram of a first filtering module according to an embodiment;

FIG. 4 is a schematic diagram of a voltage adjusting unit according to an embodiment;

FIG. 5 is a schematic diagram of a case according to an embodiment;

FIG. 6 is a schematic diagram of a circuit board according to an embodiment;

fig. 7 is a schematic diagram of a case and a counterweight according to an embodiment.

Reference numerals illustrate:

a filter circuit-10; an input interface-11; a first filtering module-12; a filter input-121; -a filtering output 122; a first filtering unit-123; a second filtering unit-124; a first filtering branch-1241; a second filtering branch-1242; an output interface-13; a second filtering module-14; a voltage adjustment unit-15; a voltage adjustment unit input terminal 15a; the output end-15 b of the voltage adjusting unit; a first resistance unit-151; a second resistance unit 152; chip to be tested-20; test meter-30; a circuit board-100; balancing weight 200; a box body-300; a first aperture 301; a second opening 302.

Detailed Description

In order that the utility model may be readily understood, a more complete description of the utility model will be rendered by reference to the appended drawings. Embodiments of the utility model are illustrated in the accompanying drawings. This utility model may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, 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 utility model belongs. The terminology used herein in the description of the utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model.

It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element.

It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them. It is understood that "plurality" means two or more.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, the term "and/or" as used in this specification includes any and all combinations of the associated listed items.

In one embodiment, referring to fig. 1, an audio test system for an audio class chip is provided. The audio test system includes a test meter 30 and a filter. The filter is connected between the audio chip 20 and the test meter 30, and is used for filtering out part of the audio signals sent by the audio chip 20 and reserving the audio signals of the target wave band. As an example, the audio test system is provided with a class D power amplifier. Class D power amplifiers are a type of modulated audio signal amplifier. When the audio signal and the triangular wave high-frequency carrier wave are compared through the comparator, pulse width modulation waves (Pulse width modulation wave, PWM) with different duty ratios can be obtained, and then the PWM signal is input to the loudspeaker through the field effect tube pair tube and the filter. The PWM obtained after modulation contains an audio component, and at this time, the high-frequency carrier wave needs to be filtered by a low-pass filter to be restored to an original signal.

Referring to fig. 2, the filter at least includes a weight 200, a case 300, and a plurality of circuit boards 100, and each circuit board 100 may integrate the filter circuit 10. The filter circuit 10 is provided with various electronic components, and can filter out part of the audio signals and retain the audio signals of the target wave band. As an example, the high frequency signal band may be eliminated, while the low frequency signal band is preserved. In this case, the filter is a low-pass filter.

In one embodiment, referring to fig. 1, the filtering circuit 10 includes an input interface 11, a plurality of first filtering modules 12 arranged in cascade, and an output interface 13.

The input interface 11 may be connected to the audio-type chip 20 to be tested, and a signal of the chip 20 to be tested flows in through the input interface 11.

The first filtering module 12 includes a filtering input 121, a filtering output 122, a first filtering unit 123, and a second filtering unit 124.

The filter input 121 is connected to the input interface 11. An output of the second filtering unit 124 is connected to the filtering output 122. The signals filtered by the first filter unit 123 and the second filter unit 124 enter the output interface 13 from the filter output 122.

The first filtering unit 123 is used for filtering out high frequency signals. The second filtering unit 124 is configured to perform separation filtering on the signal filtered by the first filtering unit 123, and output the separated and filtered signal from the filtering output terminal 122. As an example, the second filtering unit 124 may separate the signal into a high frequency signal and a low frequency signal, and the second filtering unit 124 may consume the high frequency signal band again.

In the same first filter module 12, the input end of the second filter unit 124 is connected to the input end of the first filter unit 123. It is understood that the input of the first filtering unit 123 and the input of the second filtering unit 124 may both be connected to the filtering input 121.

The plurality of first filter modules 12 may be arranged in cascade. At this time, the filter input end 121 of the first stage first filter module 12 is connected to the input interface 11, and the filter output end 122 of the previous stage first filter module 12 is connected to the filter input end 121 of the next stage first filter module 12. It can be appreciated that after the plurality of first filtering modules 12 are cascaded, the audio signal can be filtered multiple times, so as to achieve the purpose of high-precision signal filtering. As an example, the filter circuit 10 may comprise two first filter modules 12 arranged in cascade.

The output interface 13 is connected to the filter output 122 of the final first filter module 12. The output interface 13 may be connected to the test meter 30, and the resulting target signal is transferred to the test meter 30, so that the test meter 30 tests the target signal.

Referring to fig. 5 to 7, the filter circuit 10 may be integrated onto a circuit board 100 of the filter. The housing 300 of the filter comprises a first aperture 301 and a second aperture 302. The first opening 301 exposes the input interface 11 and the second opening 302 exposes the output interface 13. The first opening 301 may be connected to the audio-type chip 20 to be tested, and the second opening 302 may be connected to the test meter 30.

In the above embodiment, after the input interface 11 of the filter circuit 10 receives the signal input by the connection of the audio chip to be tested 20, the first filter module 12 can filter out the high frequency band and reserve the low frequency band. The first filtering unit 123 in the first filtering module 12 may consume a high frequency band, and the second filtering unit 124 may separate the signal filtered by the first filtering unit 123. Meanwhile, the second filtering unit 124 may consume the high frequency band again, so as to achieve the purpose of consuming the high frequency band multiple times.

In addition, the filter circuit 10 in the above embodiment is of a passive design, and the filter circuit 10 is directly connected between the audio chip 20 to be tested and the test meter 30. Thus, the filtering purpose is achieved while the volume is reduced.

In one embodiment, the first filtering unit 123 includes a first capacitor. The first capacitor includes one end and another end. One end of the first capacitor is connected with the input end of the first filter module 12, and the other end of the first capacitor is grounded. For example, referring to fig. 3, the first capacitor may be C1.

It will be appreciated that the high frequency signal may pass through and be dissipated by the first capacitor, thereby filtering the high frequency signal. Meanwhile, it is difficult for the low frequency signal to pass through the first capacitor so that the low frequency signal may flow to the second filtering unit 124 without passing through the first filtering unit 123.

In one embodiment, the second filtering unit 124 includes a first filtering branch 1241 and a second filtering branch 1242 arranged in parallel.

The first filtering branch 1241 and the second filtering branch 1242 are respectively used for filtering signals with different wave bands. Specifically, the first filtering branch 1241 may pass through the high frequency signal, and the first filtering branch 1241 may remove the high frequency signal. The second filtering branch 1242 may pass the low frequency signal and pass the low frequency signal to the filtering output 122. Specifically, the first filtering branch includes a first resistor, and the second filtering branch includes an inductance coil. For example, referring to fig. 3, the first resistor of the first filtering branch 1241 may be the resistor R1, and may also include the capacitor C2, and the second filtering branch 1242 may include the inductor L1.

Of course, the plurality of cascaded first filtering modules 12 may include different combinations of second filtering units 124. As an example, referring to fig. 3, the first filtering branch 1241 in the first stage first filtering module 12 may include a resistor R1 and a capacitor C2 arranged in series, while the second filtering branch 1242 in the first stage first filtering module 12 may include an inductor L1. Similarly, the first filtering module 12 (not shown) may also include a resistor R2 and a capacitor C2 at the second stage, and the first filtering branch 1241 may include a resistor R3, and the second filtering branch 1242 may include an inductor L2. The relevant performance parameters of the elements in each stage of the first filter module 12 may be similar.

In one embodiment, the filtering circuit 10 further includes a second filtering module 14.

An input end of the second filter module 14 is connected with an output end of the final stage first filter module 12, and an output end of the second filter module 14 is connected with the output interface 13. It will be appreciated that the second filtering module 14 may eventually filter out the high frequency signal again.

Specifically, the second filtering module 14 includes a second capacitor and a second resistor. One end of the second capacitor is connected with the output end of the final stage first filter module 12, and the other end of the second capacitor is grounded. The two ends of the second resistor are respectively connected with the output end of the final stage first filter module 12 and the output interface 13. It will be appreciated that the high frequency signal may pass through and be dissipated by the second capacitor, thereby filtering the high frequency signal. Meanwhile, it is difficult for the low frequency signal to pass through the second capacitor so that the low frequency signal can enter the output interface 13.

In one embodiment, the filter circuit 10 includes a voltage adjustment unit 15. The voltage adjustment unit 15 includes a voltage adjustment unit input 15a and a voltage adjustment unit output 15b.

The input end 15a of the voltage adjusting unit is connected with the input interface 11, and the output end 15b of the voltage adjusting unit is connected with the filtering input end 121 of the first stage first filtering module 12. The voltage adjusting unit 15 is used for adjusting the gain of the entire filter circuit 10.

Specifically, the voltage adjusting unit 15 includes a first resistor unit 151 and a second resistor unit 152 disposed in parallel. The first resistor unit 151 includes a third resistor, and the second resistor unit 152 includes a fourth resistor, a fifth resistor, and a variable resistor, and the fourth resistor is connected in parallel with the fifth resistor and then connected in series with the variable resistor.

As an example, referring to fig. 4, the third resistor may include a resistor R5, the fourth resistor may include a resistor R6, the fifth resistor may include a resistor R7, and the variable resistor may include a resistor VR1. At this time, the resistor R6 and the resistor R7 are connected in parallel and then connected in series with the variable resistor VR1.

In the above-described embodiment, the resistance of the voltage adjusting unit 15 is controlled by changing the resistance value of the variable resistor, thereby adjusting the gain of the entire filter circuit 10.

Typically class D filters have a passband of 20-20kHz. The voltage adjustment unit 15 keeps the gain as flat as possible within the passband frequency. By setting the rated values of the respective electronic components of the filter circuit 10, the loss of the filter circuit 10 can be made to reach the target loss.

The filter circuit 10 may be configured as a multi-order filter circuit. For example, the filter circuit 10 may include two first filter modules 12 and one second filter module 14 that are disposed in cascade, and together form a fifth-order filter circuit.

The five-order filter circuit can better filter out high-frequency signals and keep low-frequency signals. Moreover, the volume of the fifth-order filter circuit is smaller, so that the volume of the filter is smaller, and the filter can be easily embedded into the audio test system.

In the conventional technology, the low-order filter still has certain defects. For example, a steep attenuation curve is difficult to achieve with a low order filter. Although the low-order filter can be modified to a certain extent, the low-order filter can be used for measuring the output frequency response of the power amplifier. For example, the performance of the low order filter may meet the 1kHz commonly used for power amplifier testing. But the low order filter will produce some error for the output noise and distortion measurements associated with the power amplifier across the output frequency band (20 Hz-20 kHz).

Therefore, in the above embodiment, by combining the multi-order passive filters, relatively high performance is achieved, so that the output signal of the class D power amplifier can realize roll-off at a frequency higher than 20kHz, while maintaining the passband gain of 0-20kHz in an ideal state. Through the calculation of the transfer function, the multi-order filter model can be obtained by means of the filter design and the simulation tool, and finally the analysis of the audio signals output by the class D power amplifier is realized.

As an example, the frequency response of the conventional filter circuit 10 needs to be less than 0.1dB, the noise to be filtered is high frequency noise, the high frequency cut-off ratio thereof needs to be greater than 50dB, the insertion loss is less than-0.1 dB, and the inter-channel crosstalk is greater than 90dB. In the filter circuit 10 in the above embodiment, the rated values of the resistors, the capacitors and the inductors are set so that the cut-off frequency of the filter circuit 10 can be 42kHz, the frequency response in the passband frequency is 0.05dB, the high-frequency cut-off ratio is about 60dB, the insertion loss is 0.025dB, and the inter-channel crosstalk is greater than 120dB.

In addition, conventional RC filters (e.g., RC filters) typically suffer from relatively large losses, but the passband and the filtered curve are relatively smooth. While LC filters (e.g., LC filters) or LC-rc filters (e.g., RLC filters) generally have smaller losses, they have larger inductance volumes and have higher requirements for the performance of the inductor and the parallel resonance parameters of the overall circuit structure. In the above embodiment, the filter formed by combining the inductance, the resistance and the capacitance can properly reduce the loss of the whole filter circuit 10, so that the overall loss of the whole filter structure meets the expectations.

In one embodiment, the filter circuit 10 includes a plurality of input interfaces 11 and a plurality of output interfaces 13, and a plurality of first filter modules 12 and second filter modules 14 are disposed between each of the input interfaces 11 and the output interfaces 13. Specifically, the adjacent first capacitors may share the ground. At this time, the plurality of first filter modules 12 and second filter modules 14 between each of the input interface 11 and the output interface 13 may be symmetrically disposed.

The filter circuit 10 may be provided with a plurality of channels. As an example, one filter circuit 10 may include two channels. When the filter includes four circuit boards 100, the filter may include eight channels. At the same time, each channel is provided with a second filtering module 14.

In the conventional art, the filter generally includes only two or four channels. When the filter comprises eight channels, the filtering efficiency of the filter can be improved, and the testing efficiency of the audio chip to be tested is further improved. Of course, referring to fig. 6, the circuit board 100 may also be stacked, so that the filter may also include sixteen channels.

In the description of the present specification, reference to the term "some embodiments," "other embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the utility model. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present utility model, which are described in more detail and are not to be construed as limiting the scope of the present utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of the utility model should be assessed as that of the appended claims.

Claims

1. A filter circuit, comprising:

an input interface;

2. The filter circuit according to claim 1, wherein in the same first filter module, the first filter unit includes a first capacitor, one end of the first capacitor is connected to the filter input end, the other end of the first capacitor is grounded, and the input end of the second filter unit is connected to the input end of the first filter unit.

3. The filter circuit of claim 1, wherein the second filter unit includes a first filter branch and a second filter branch disposed in parallel, the first filter branch and the second filter branch being respectively used for filtering signals of different wavebands.

4. A filter circuit according to claim 3, wherein the first filter leg comprises a first resistor and the second filter leg comprises an inductor.

5. The filter circuit of claim 1, wherein the filter circuit further comprises:

6. The filter circuit of claim 5, wherein the second filter module comprises a second capacitor and a second resistor, one end of the second capacitor is connected to the output end of the final stage first filter module, the other end of the second capacitor is grounded, and two ends of the second resistor are respectively connected to the output end of the final stage first filter module and the output interface.

7. The filter circuit of claim 1, wherein the filter circuit comprises:

8. The filter circuit according to claim 7, wherein the voltage adjustment unit includes: the first resistor unit and the second resistor unit are arranged in parallel, the first resistor unit comprises a third resistor, the second resistor unit comprises a fourth resistor, a fifth resistor and a variable resistor, and the fourth resistor is connected in parallel with the fifth resistor and then connected in series with the variable resistor.

9. The filter circuit of claim 1, wherein the filter circuit comprises a plurality of the input interfaces and a plurality of the output interfaces, the plurality of first filter modules being disposed between each of the input interfaces and the output interfaces.

10. A filter, characterized by comprising a balancing weight, a box body and a circuit board, wherein the balancing weight and the circuit board are both arranged in the box body, the circuit board integrates the filter circuit according to any one of claims 1-9, and the box body comprises: a first opening exposing the input interface and a second opening exposing the output interface.