A Class D amplifier audio output detection method, device and medium

Abstract

The present invention provides a method, device, and medium for detecting audio output of a Class D amplifier in the field of Class D amplifier technology. The method includes: step S10, inputting a sine wave signal of a preset frequency into the Class D amplifier; step S20, connecting a filter circuit to the load end of the Class D amplifier and setting the cutoff frequency of the filter circuit; step S30, the Class D amplifier superimposes the sine wave signal on a carrier signal and outputs the signal through the filter circuit; step S40, sampling the output signal of the filter circuit through an ADC and performing a fast Fourier transform to obtain a complex sequence corresponding to the sampling points, thereby calculating the effective value of the input signal; step S50, multiplying the sine wave signal by the amplification factor of the Class D amplifier, comparing the value obtained with the corresponding effective value, and analyzing the complex sequence to determine whether the output of the Class D amplifier is normal. The advantage of the present invention is that it greatly improves the accuracy of audio output detection of the Class D amplifier.

Description

Technical Field

[0001] The present invention relates to the technical field of class D power amplifiers, and in particular to a method, device and medium for detecting audio output of a class D power amplifier. Background Art

[0002] Due to its high efficiency, the audio output circuit of a Class D amplifier is particularly suitable for portable and high-power audio output devices. The output waveform of a Class D amplifier is a series of PWM waveforms with varying duty cycles, which are obtained by comparing the input audio signal with a triangular high-frequency carrier wave through a comparator. It is difficult to determine whether a Class D amplifier is operating properly by directly measuring the output waveform at the output.

[0003] Traditionally, testing the audio output of a Class D amplifier involves manually determining whether the audio signal output by the speaker is normal, thereby confirming whether the Class D amplifier's audio output is normal. However, this method is highly subjective, and when multiple Class D amplifiers are tested simultaneously, their audio outputs are prone to mutual interference and confusion, making judgment difficult.

[0004] Therefore, how to provide a method, device and medium for detecting the audio output of a Class D power amplifier to improve the accuracy of audio output detection of the Class D power amplifier has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method, device and medium for detecting audio output of a Class D power amplifier, so as to improve the accuracy of audio output detection of the Class D power amplifier.

[0006] In a first aspect, the present invention provides a method for detecting audio output of a Class D amplifier, comprising the following steps:

[0007] Step S10: inputting a sine wave signal of a preset frequency into a Class D amplifier;

[0008] Step S20: Connect a filter circuit to the load end of the Class D power amplifier and set the cutoff frequency of the filter circuit;

[0009] Step S30: The class D power amplifier adds the carrier signal to the sine wave signal and outputs the signal through a filter circuit;

[0010] Step S40: The MCU samples the output signal of the filter circuit through the ADC and performs a fast Fourier transform to obtain a complex sequence corresponding to the sampling points, and calculates the effective value of the input signal based on the complex sequence;

[0011] Step S50: Multiply the sine wave signal by the amplification factor of the Class D power amplifier to obtain a value, compare it with the effective value of the corresponding sampling point, and analyze the complex sequence of the sampling point. When the effective value is judged to be normal and the distribution of the complex sequence satisfies the set complex sequence distribution relationship of the sine wave signal, it is considered that the output of the Class D power amplifier is normal; otherwise, it is considered that the output of the Class D power amplifier is abnormal.

[0012] Furthermore, in step S10, the preset frequency has a value range of 20 Hz to 20 kHz.

[0013] Furthermore, the step S20 is specifically as follows:

[0014] Determine the type of Class D amplifier. If it is a full-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive and negative poles of the load end respectively; if it is a half-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive pole of the load end;

[0015] The cutoff frequency of the second-order passive low-pass RC filter circuit is set to 20 kHz.

[0016] Furthermore, in step S40, sampling the output signal is specifically performed as follows:

[0017] The ADC samples the output signal of the filter circuit according to the preset resolution and sampling frequency to obtain a series of sampling points, and calculates the amplitude of each sampling point;

[0018] The amplitude formula of the nth sampling point is expressed as y=A*sin(2π*n / N+φ)+h;

[0019] Among them, N represents the number of sampling points, N = fs / f; f represents the resolution; fs represents the sampling frequency, which is 44 kHz - 60 kHz; y represents the sampling point amplitude; h represents the DC component of the input signal; φ represents the initial phase of the sine wave signal; A represents the amplitude of the sine wave signal.

[0020] Furthermore, in step S40, the effective value calculation process is specifically as follows:

[0021] A series of sampling points are fast Fourier transformed to obtain a corresponding complex number series, where the complex number of the k-th sampling point in the complex number series is expressed as:

[0022]

[0023] Where N represents the number of sampling points; x[n] represents the amplitude of the nth sampling point; j represents the imaginary unit in the complex number; k represents the kth sampling point; n is an integer in the range of 0 to N;

[0024] Then, the amplitude value of each sampling point in the frequency range of [0 to fs / 2] is calculated based on the complex number series to obtain an amplitude value sequence, and the amplitude value of the sampling point at the preset frequency is set as the effective value, wherein the amplitude value is calculated as follows:

[0025] F[k]=M[k]*2 / N; where F[k] represents the amplitude value corresponding to the k-th sampling point; M[k] represents the modulus value of the complex number corresponding to the k-th sampling point, specifically the square of the absolute value of the complex number corresponding to the sampling point.

[0026] Furthermore, in step S50, the process of determining whether the output of the Class D power amplifier is normal is specifically as follows:

[0027] When the distribution of the complex sequence satisfies the complex sequence distribution relationship of the set sinusoidal wave signal, and the value Z obtained by multiplying the sinusoidal wave signal by the amplification factor of the Class D power amplifier and the effective value F satisfy the following conditions: (ZF) / Z≤±10%; and at the same time, the effective value F is greater than any other amplitude value, then the Class D power amplifier output is considered normal.

[0028] In a second aspect, the present invention provides a Class D amplifier audio output detection device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method described in the first aspect when executing the program.

[0029] In a third aspect, the present invention provides a Class D amplifier audio output detection medium having a computer program stored thereon, which implements the method described in the first aspect when executed by a processor.

[0030] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0031] The output of the Class D amplifier is filtered through a filtering circuit, that is, the carrier signal of the Class D amplifier is filtered out. The output signal of the filtering circuit is then sampled by an ADC and fast Fourier transform is performed to obtain a complex sequence corresponding to the sampled signal. The effective value of the input signal is calculated through the complex sequence. Finally, by comparing the sine wave signal and the effective value (one of the amplitude values) of the sampled signal, it can be determined whether the audio output of the Class D amplifier is normal. Compared with manual judgment, this is more objective and avoids mutual interference when testing the audio output of multiple Class D amplifiers at the same time, ultimately greatly improving the accuracy of Class D amplifier audio output detection.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Figure 1 The present invention is a flow chart of a method for detecting audio output of a Class D power amplifier.

[0035] Figure 2 It is a structural schematic diagram of a Class D power amplifier audio output detection device of the present invention.

[0036] Figure 3 It is a structural schematic diagram of a Class D power amplifier audio output detection medium of the present invention. DETAILED DESCRIPTION

[0037] The embodiments of the present application provide a method, device, and medium for detecting audio output of a Class D power amplifier, thereby improving the accuracy of audio output detection of a Class D power amplifier.

[0038] The technical solution in the embodiments of the present application has the following overall idea: the output of the Class D power amplifier is filtered through a filtering circuit, the output signal of the filtering circuit is sampled by an ADC and a fast Fourier transform is performed to obtain a complex sequence corresponding to each sampled signal, the effective value of the input signal is calculated through the complex sequence, and the audio output of the Class D power amplifier is detected by comparing the effective value (one of the amplitude values) of the sine wave signal and the sampling signal to improve the accuracy of the audio output detection of the Class D power amplifier.

[0039] Example 1

[0040] This embodiment provides a method for detecting audio output of a Class D amplifier. Figure 1 As shown, the following steps are included:

[0041] Step S10: inputting a sine wave signal of a preset frequency into a Class D amplifier;

[0042] Step S20: Connect a filter circuit to the load end of the Class D power amplifier and set the cutoff frequency of the filter circuit;

[0043] Step S30: The class D power amplifier adds the carrier signal to the sine wave signal and outputs the signal through a filter circuit;

[0044] Step S40: The MCU samples the output signal of the filter circuit through the ADC and performs a fast Fourier transform to obtain a complex sequence corresponding to the sampling points, and calculates the effective value of the input signal based on the complex sequence;

[0045] According to the Nyquist theorem, in order to prevent spectrum aliasing, the sampling frequency of the ADC should be at least twice the cutoff frequency of the filter circuit. For example, when the cutoff frequency is 20 kHz, the sampling frequency can be 44 kHz.

[0046] Step S50: Multiply the sine wave signal by the amplification factor of the Class D power amplifier to obtain a value, compare it with the effective value of the corresponding sampling point, and analyze the complex sequence of the sampling point. When the effective value is judged to be normal and the distribution of the complex sequence satisfies the set complex sequence distribution relationship of the sine wave signal, it is considered that the output of the Class D power amplifier is normal; otherwise, it is considered that the output of the Class D power amplifier is abnormal.

[0047] This embodiment samples the above-mentioned scheme, filters the output of the Class D power amplifier through a filtering circuit, then uses an ADC to sample the output signal of the filtering circuit and performs a fast Fourier transform on all sampling points to obtain a complex sequence of sampling points, and then calculates the effective value of the sampling signal through the complex sequence. Finally, the audio output of the Class D power amplifier is detected by comparing the sine wave signal and the effective value (one of the amplitude values) of the sampling signal to improve the accuracy of the audio output detection of the Class D power amplifier.

[0048] In step S10, the preset frequency range is 20 Hz to 20 kHz. Because audio signals in the frequency range of 20 Hz to 20 kHz are within the sound signal range that can be distinguished by the human ear, the present invention preferably sets the preset frequency range to 20 Hz to 20 kHz.

[0049] The step S20 is specifically as follows:

[0050] Determine the type of Class D amplifier. If it is a full-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive and negative poles of the load end respectively; if it is a half-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive pole of the load end;

[0051] The cutoff frequency of the second-order passive low-pass RC filter circuit is set to 20 kHz.

[0052] Since full-bridge Class D amplifiers have differential outputs, both polarities of the differential signal are connected to a second-order passive low-pass RC filter circuit for testing. Half-bridge Class D amplifiers, on the other hand, have single-ended outputs, so only the single-ended output signal is tested, requiring only the positive electrode of the load to be connected to a second-order passive low-pass RC filter circuit.

[0053] In step S40, sampling the output signal is specifically performed as follows:

[0054] The ADC samples the output signal of the filter circuit according to the preset resolution and sampling frequency to obtain a series of sampling points, and calculates the amplitude of each sampling point;

[0055] The amplitude formula of the nth sampling point is expressed as y=A*sin(2π*n / N+φ)+h;

[0056] Among them, N represents the number of sampling points, N = fs / f; f represents the resolution; fs represents the sampling frequency, which is 44 kHz - 60 kHz; y represents the sampling point amplitude; h represents the DC component of the input signal; φ represents the initial phase of the sine wave signal; A represents the amplitude of the sine wave signal.

[0057] In step S40, the effective value calculation process is specifically as follows:

[0058] A series of sampling points are fast Fourier transformed to obtain a corresponding complex number series, where the complex number of the k-th sampling point in the complex number series is expressed as:

[0059]

[0060] Where N represents the number of sampling points; x[n] represents the amplitude of the nth sampling point; j represents the imaginary unit in the complex number; k represents the kth sampling point; n is an integer in the range of 0 to N;

[0061] When the Class D amplifier output is normal, the complex sequence calculated above conforms to the complex sequence distribution relationship of the set sine wave signal. Therefore, the calculation of the complex sequence can be used as one of the conditions for determining whether the Class D amplifier output is normal.

[0062] Then, the amplitude value of each sampling point in the frequency range of [0 to fs / 2] is calculated based on the complex number series to obtain an amplitude value sequence, and the amplitude value of the sampling point at the preset frequency is set as the effective value, wherein the amplitude value is calculated as follows:

[0063] F[k]=M[k]*2 / N; where F[k] represents the amplitude value corresponding to the k-th sampling point; M[k] represents the modulus value of the complex number corresponding to the k-th sampling point, specifically the square of the absolute value of the complex number corresponding to the sampling point.

[0064] The above method calculates the amplitude value of the sampling point at the preset frequency, i.e., the effective value. When the Class D amplifier output is normal, the effective value should be the maximum of all amplitude values. The effective value should theoretically be equal to the value obtained by multiplying the sine wave signal by the Class D amplifier's amplification factor. Therefore, the effective value can be used as one of the criteria for determining whether the Class D amplifier output is normal.

[0065] By combining the complex sequence and the effective value, it can be determined whether the output of the Class D power amplifier is normal.

[0066] In step S50, the process of determining whether the output of the Class D power amplifier is normal is as follows:

[0067] The Class D amplifier output is considered normal when the distribution of the complex sequence satisfies the complex sequence distribution relationship of the set sinusoidal signal, and the value Z obtained by multiplying the sinusoidal signal by the amplification factor of the Class D amplifier satisfies the following relationship: (ZF) / Z ≤ ±10%; and the effective value F is greater than any other amplitude value. Due to the influence of electronic component precision and measurement errors, there is often a certain deviation between the calculated effective value and the value Z obtained by multiplying the sinusoidal signal by the amplification factor of the Class D amplifier. Therefore, the present invention sets this deviation to within 10%, and the effective value F is greater than any other amplitude value to be considered as meeting the requirements.

[0068] The step S50 is described with an example:

[0069] The sampling frequency is 60kHz, and the number of sampling points is 1000, so the resolution (frequency accuracy) is 60Hz. Each sampling point is fast Fourier transformed to obtain a complex sequence corresponding to the 1000 sampling points. Then, the formula F[k] = M[k] * 2 / N is applied to calculate the amplitude value corresponding to the k-th sampling point. The amplitude value of the sampling point at the preset frequency is set as the effective value;

[0070] By performing complex calculations on each point of the fast Fourier transform results, we can know the amplitude value of each frequency of the sampling signal, and find the effective value of the preset frequency of the sampling point from the amplitude value sequence. By comparing the effective value with the value of the corresponding amplification multiple of the input sinusoidal wave signal, we can determine whether the Class D amplifier is normal.

[0071] For example, when inputting a 1kHz signal, the maximum amplitude value, that is, the effective value, should be obtained at the 16th or 17th point, and the effective value should be equal to the amplification factor of the Class D amplifier multiplied by the signal amplitude of the sine wave signal. The corresponding amplitude values ​​of the remaining 1 to 500 points should be significantly smaller than the effective value.

[0072] Based on the same inventive concept, this application provides an electronic device embodiment corresponding to the first embodiment, see the second embodiment for details.

[0073] Example 2

[0074] This embodiment provides a Class D amplifier audio output detection device, such as Figure 2 As shown, it includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, any implementation method in the first embodiment can be implemented.

[0075] Since the electronic device described in this embodiment is the device used to implement the method in Example 1 of this application, based on the method described in Example 1 of this application, those skilled in the art will be able to understand the specific implementation of the electronic device of this embodiment and its various variations. Therefore, how the electronic device implements the method in the embodiment of this application will not be described in detail here. As long as the device used by those skilled in the art to implement the method in the embodiment of this application falls within the scope of protection to be provided by this application.

[0076] Based on the same inventive concept, this application provides a storage medium corresponding to Example 1, see Example 3 for details.

[0077] Example 3

[0078] This embodiment provides a class D amplifier audio output detection medium, such as Figure 3 As shown, a computer program is stored thereon, and when the computer program is executed by a processor, any implementation method in Example 1 can be implemented.

[0079] The technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0080] The output of the Class D amplifier is filtered through a filtering circuit, that is, the carrier signal of the Class D amplifier is filtered out. The output signal of the filtering circuit is then sampled by an ADC and fast Fourier transform is performed to obtain a complex sequence corresponding to the sampled signal. The effective value of the input signal is calculated through the complex sequence. Finally, by comparing the sine wave signal and the effective value (one of the amplitude values) of the sampled signal, it can be determined whether the audio output of the Class D amplifier is normal. Compared with manual judgment, this is more objective and avoids mutual interference when testing the audio output of multiple Class D amplifiers at the same time, ultimately greatly improving the accuracy of Class D amplifier audio output detection.

[0081] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0082] The present invention is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products of the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0083] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0085] Although the specific embodiments of the present invention are described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting audio output of a Class D power amplifier, characterized by: The steps include: Step S10: inputting a sine wave signal of a preset frequency into a Class D amplifier; Step S20: Connect a filter circuit to the load end of the Class D power amplifier and set the cutoff frequency of the filter circuit; Step S30: The class D power amplifier adds the carrier signal to the sine wave signal and outputs the signal through a filter circuit; Step S40: The MCU samples the output signal of the filter circuit through the ADC and performs a fast Fourier transform to obtain a complex sequence corresponding to the sampling points, and calculates the effective value of the input signal based on the complex sequence; Step S50: Multiply the sine wave signal by the amplification factor of the Class D power amplifier to obtain a value, compare it with the effective value of the corresponding sampling point, and analyze the complex sequence of the sampling point. When the effective value is judged to be normal and the distribution of the complex sequence satisfies the set complex sequence distribution relationship of the sine wave signal, it is considered that the output of the Class D power amplifier is normal; otherwise, it is considered that the output of the Class D power amplifier is abnormal.

2. The method for detecting audio output of a Class D power amplifier according to claim 1, wherein: In step S10, the preset frequency ranges from 20 Hz to 20 kHz.

3. The method for detecting audio output of a Class D power amplifier according to claim 1, wherein: The step S20 is specifically as follows: Determine the type of Class D amplifier. If it is a full-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive and negative poles of the load end respectively; if it is a half-bridge Class D amplifier, connect a second-order passive low-pass RC filter circuit to the positive pole of the load end; The cutoff frequency of the second-order passive low-pass RC filter circuit is set to 20 kHz.

4. The method for detecting audio output of a Class D power amplifier according to claim 1, wherein: In step S40, sampling the output signal is specifically performed as follows: The ADC samples the output signal of the filter circuit according to the preset resolution and sampling frequency to obtain a series of sampling points, and calculates the amplitude of each sampling point; The amplitude formula of the nth sampling point is expressed as y=A*sin(2π*n / N+φ)+h; Where N is the number of sampling points, N = fs / f; f is the resolution; fs is the sampling frequency, which ranges from 44kHz to 60kHz; y is the sampling point amplitude; h is the DC component of the input signal; φ is the initial phase of the sinusoidal signal; and A is the amplitude of the sinusoidal signal.

5. The method for detecting audio output of a Class D power amplifier according to claim 1, wherein: In step S40, the effective value calculation process is specifically as follows: A series of sampling points are fast Fourier transformed to obtain a corresponding complex number sequence, where the complex number of the k-th sampling point in the complex number sequence is expressed as: Where N represents the number of sampling points; x[n] represents the amplitude of the nth sampling point; j represents the imaginary unit in the complex number; k represents the kth sampling point; n is an integer in the range of 0 to N; Then, the amplitude value of each sampling point in the frequency range of [0 to fs / 2] is calculated according to the complex sequence to obtain an amplitude value sequence, and the amplitude value of the sampling point at the preset frequency is set as the effective value, wherein the amplitude value is calculated as follows: F[k]=M[k]*2 / N; where F[k] represents the amplitude value corresponding to the k-th sampling point; M[k] represents the modulus value of the complex number corresponding to the k-th sampling point, specifically the square of the absolute value of the complex number corresponding to the sampling point.

6. The method for detecting audio output of a Class D power amplifier according to claim 5, wherein: In step S50, the process of determining whether the output of the Class D power amplifier is normal is as follows: When the distribution of the complex sequence satisfies the complex sequence distribution relationship of the set sinusoidal wave signal, and the value Z obtained by multiplying the sinusoidal wave signal by the amplification factor of the Class D power amplifier and the effective value F satisfy the following conditions: (ZF) / Z≤±10%; and at the same time, the effective value F is greater than any other amplitude value, then the Class D power amplifier output is considered normal.

7. A Class D amplifier audio output detection device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 6 is implemented.

8. A Class D amplifier audio output detection medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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