Circuit for testing audio performance of audio equipment and audio performance testing system

Abstract

The utility model relates to the technical field of audio performance index detection and test, in particular to a circuit for testing audio performance of audio equipment and an audio performance test system. A circuit for testing audio performance of audio equipment comprises an impedance simulation circuit which comprises at least two groups of jumpers and is used for simulating impedance characteristics of audio output equipment under different audio frequencies; the jumper cap is connected with any group of jumper wires and is used for adjusting the impedance value of the impedance analog circuit by being connected with different jumper wires; and the low-pass filter circuit is connected between the audio input end and the analog impedance circuit and is used for filtering high-frequency noise in the audio signal. According to the scheme, a complete process from audio signal input, filtering and loudspeaker simulation to earphone simulation is realized. The risk of directly using a real loudspeaker is avoided, and the test accuracy is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of audio performance index detection and testing, in particular to a circuit for testing the audio performance of audio equipment and an audio performance testing system. Background Art

[0002] Currently, audio performance testing of the power amplifier output stages of audio devices like tablet motherboards, TV motherboards, and conference machine motherboards mostly uses real speakers or linear loads with the same resistance as the speakers. This directly yields test results under normal speaker conditions. However, using real speakers for maximum load testing, aging testing, and commissioning tests can easily damage the speakers or reduce their lifespan due to excessive amplifier output power. Furthermore, when the same motherboard is shipped to different customers with speakers of varying specifications, frequent speaker replacement and plugging and unplugging during testing is unavoidable. While using a linear load with the same resistance as the speaker for testing avoids speaker burnout, the signal applied to the load after the pre-lowpass filter is still contaminated with multiple harmonics close to the fundamental component, and the linear load cannot simulate the same load model as the speaker at different audio frequencies.

[0003] In summary, existing audio performance testing methods have two main problems:

[0004] 1. When using real audio output devices, such as speakers or headphones for testing, the speakers may be damaged due to excessive power, resulting in economic losses.

[0005] 2. Use a simple electronic load to simulate the speaker, but this simulation is not accurate enough to reflect the actual performance of the speaker at different audio frequencies.

[0006] Therefore, there is an urgent need to design an audio performance detection system that can solve one or more of the above problems. Utility Model Content

[0007] The purpose of the utility model is to provide a circuit for testing the audio performance of audio equipment and an audio performance testing system to address the deficiencies of the prior art.

[0008] The utility model achieves the above-mentioned purpose through the following technical solutions: A circuit for testing the audio performance of an audio device, comprising:

[0009] An impedance simulation circuit, comprising at least two sets of jumpers, for simulating impedance characteristics of an audio output device at different audio frequencies;

[0010] a jumper cap connected to any group of the jumpers, and used to adjust the impedance value of the impedance simulation circuit by connecting to different jumpers;

[0011] The low-pass filter circuit is connected between the audio input terminal and the analog impedance circuit and is used to filter out high-frequency noise in the audio signal.

[0012] As a further solution of the present invention: the impedance simulation circuit is a speaker load simulation circuit and / or an earphone load simulation circuit.

[0013] As a further solution of the present invention: the speaker load simulation circuit is used to simulate the impedance characteristics of the speaker at different audio frequencies;

[0014] The speaker load simulation circuit includes inductors SL3, SL4, SL5, and SL6, resistors AR3, AR4, AR5, AR6, AR19, AR20, AR21, and AR22, and jumpers JP11, JP12, JP15, and JP16;

[0015] One end of the inductor SL3 is connected to the output terminal R+ of the low-pass filter circuit, and the other end is connected to the first pin of the jumper JP12. Resistors AR3 and AR4 are connected in parallel, and the two ends of the parallel resistor formed by the parallel connection are respectively connected to the other end of the inductor SL3 and the first pin of the jumper JP11. Resistors AR5 and AR6 are connected in parallel, and the parallel resistor formed by the parallel connection has one end connected to the second pin of the jumper JP11 and the second pin of the jumper JP12, respectively, and the other end is connected to one end of the inductor SL4. The other end of the inductor SL4 is connected to the output terminal R- of the low-pass filter circuit.

[0016] One end of the inductor SL5 is connected to the output terminal L+ of the low-pass filter circuit, and the other end is connected to the first pin of the jumper JP16. Resistors AR19 and AR20 are connected in parallel, and the two ends of the parallel resistor formed by the parallel connection are respectively connected to one end of the inductor SL5 and the first pin of the jumper JP15. Resistors AR21 and AR22 are connected in parallel, and one end of the parallel resistor formed by the parallel connection is respectively connected to the second pin of the jumper JP12 and the second pin of the jumper JP16, and the other end is connected to one end of the inductor SL6. The other end of the inductor SL6 is connected to the output terminal L- of the low-pass filter circuit.

[0017] As a further solution of the present invention: the headphone load simulation circuit is used to simulate the impedance characteristics of the headphone at different audio frequencies;

[0018] The headphone load simulation circuit includes resistors AR11, AR12, AR13, AR14, AR15, AR16, AR17, AR18, jumpers JP7, JP8, and connector ACN3;

[0019] Connect pins 1 and 2 or pins 2 and 3 of jumper JP7 through a jumper cap; connect pins 1 and 2 or pins 2 and 3 of jumper JP8 through a jumper cap;

[0020] Resistors AR11 and AR12 are connected in series, with the ends of the series circuit connected to pin 1 of jumper JP8 and pin 3 of the connector, respectively. Resistors AR13 and AR14 are connected in series, with the ends of the series circuit connected to pin 1 and pin 3 of jumper JP8, respectively. Resistors AR15 and AR16 are connected in series, with the ends of the series circuit connected to pin 1 of jumper JP7 and pin 2 of the connector, respectively. Resistors AR17 and AR18 are connected in series, with the ends of the series circuit connected to pin 1 and pin 3 of jumper JP7, respectively. Pin 2 of jumper JP8 and pin 2 of JP7 are connected and grounded. Pin 1 of the connector is grounded.

[0021] As a further solution of the present invention: the low-pass filter circuit includes inductors AL1, AL2, AL3, AL4, capacitors AC1, AC2, AC3, AC4, AC5, AC6, resistors AR1, AR2, and jumpers JP1, JP2, JP3, JP4, JP5, JP6, JP13, JP14;

[0022] Connect pin 1 of jumper JP13 to pin 1 of jumper JP1. Connect pin 3 of jumper JP13 to one end of inductor AL1. Connect the other end of inductor AL1 to pin 2 of capacitor AC1, pin 2 of capacitor AC3, and pin 3 of jumper JP1, respectively. Connect pin 1 of capacitor AC1 to one end of resistor AR1. Connect pin 1 of capacitor AC3 to ground.

[0023] Connect pin 1 of jumper JP14 to one end of inductor AL2. Connect the other end of inductor AL2 to the other end of resistor AR1, pin 1 of capacitor AC5, and pin 1 of jumper JP2. Connect pin 2 of capacitor AC5 to ground. Connect pin 3 of jumper JP14 to pin 3 of jumper JP2.

[0024] Connect pin 1 of jumper JP6 to pin 1 of jumper JP3. Connect pin 3 of jumper JP6 to one end of inductor AL3. Connect the other end of inductor AL3 to pin 2 of capacitor AC2, pin 1 of capacitor AC4, and pin 3 of jumper JP3 respectively. Connect pin 1 of capacitor AC2 to one end of resistor AR2. Connect pin 2 of capacitor AC4 to ground.

[0025] Connect pin 1 of jumper JP5 to one end of inductor AL4. Connect the other end of inductor AL4 to the other end of resistor AR2, pin 1 of capacitor AC6, and pin 1 of jumper JP4. Connect pin 2 of capacitor AC6 to ground. Connect pin 3 of jumper JP5 to pin 3 of jumper JP4.

[0026] The output end R+ of jumper JP1 is connected to one end of inductor SL3, the output end R- of jumper JP2 is connected to the other end of inductor SL4, the output end L- of jumper JP3 is connected to the other end of inductor SL6, and the output end L+ of jumper JP4 is connected to one end of inductor SL5.

[0027] As a further solution of the present invention: the impedance simulation circuit also includes at least one inductor and at least one resistor.

[0028] The present invention also provides another technical solution: an audio performance testing system, comprising:

[0029] an audio generating circuit, configured to generate an audio signal, and having an audio input terminal; and

[0030] A detection circuit is connected to the audio input terminal;

[0031] Wherein, the detection circuit is any one of the aforementioned circuits for testing the audio performance of an audio device.

[0032] As a further solution of the present invention: it also includes an audio analyzer connected to the detection circuit.

[0033] Beneficial effects of the utility model:

[0034] In this solution, the low-pass filter circuit is responsible for performing preliminary low-pass filtering on the audio signal input from the audio input terminal, and then passes the signal to the impedance simulation circuit;

[0035] The impedance simulation circuit includes a speaker load simulation circuit and a headphone load simulation circuit. The speaker load simulation circuit simulates the load circuit of a speaker. A filtered audio signal is loaded across the simulated speaker load to simulate the load conditions of a real speaker. The headphone load simulation circuit simulates the load circuit of a headphone. An audio signal is input through the ACN3 connector (3.5mm headphone jack) and loaded across the simulated headphone load to simulate the load characteristics of the headphone under different conditions.

[0036] By using jumpers to select different pins connected to different jumpers in the impedance simulation circuit, the impedance characteristics of the circuit can be changed, thereby simulating the performance of speakers or headphones at different frequencies. This method is very flexible because the impedance can be adjusted by conveniently moving jumpers without re-soldering or modifying the circuit. It completes the entire process from audio signal input, filtering, speaker simulation, to headphone simulation. This avoids the risks of directly using real speakers and improves test accuracy. It can be summarized as follows:

[0037] Safer: No need to use real speakers or headphones, avoiding the risk of overload and damage to the equipment.

[0038] More accurate: By simulating real load impedance characteristics, audio performance test results are closer to the performance of the device in actual use.

[0039] More flexible: The impedance value can be adjusted to adapt to speakers and headphones of different specifications, making this test system have a wider range of applications.

[0040] Simply put, the core of this solution is to simulate the load characteristics of real speakers and headphones and combine them with filtering technology to design a safe and accurate audio performance test circuit and test system. This not only solves the problems of existing technologies but also greatly improves test accuracy and equipment applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the audio performance test system of the present invention simulating a loudspeaker to perform audio performance testing.

[0042] Figure 2 This is a schematic diagram of the audio performance test system of the present invention simulating headphones to perform audio performance testing.

[0043] Figure 3 This is a schematic diagram of the circuit principle of the low-pass filter circuit of the utility model.

[0044] Figure 4 The figure is a schematic diagram of the circuit principle of the loudspeaker load simulation circuit in the impedance simulation circuit of the present invention.

[0045] Figure 5 The figure is a schematic diagram of the circuit principle of the headphone load simulation circuit in the impedance simulation circuit of the present invention.

[0046] Figure 6 This is a schematic diagram of the present invention when testing the performance of a loudspeaker or simulating its performance at different frequencies.

[0047] Figure 7 This is a schematic diagram of a pulse width signal of an amplified audio signal in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It is understood that the drawings are only provided for reference and illustration purposes and are not intended to limit the present invention. The connection relationship shown in the drawings is only for the convenience of clear description and does not limit the connection method.

[0049] like Figures 1 to 7 As shown, in an embodiment of the present invention, a circuit for testing the audio performance of an audio device is provided, comprising: an impedance simulation circuit, a jumper cap, and a low-pass filter circuit.

[0050] An impedance simulation circuit, comprising at least two sets of jumpers, for simulating impedance characteristics of an audio output device at different audio frequencies;

[0051] a jumper cap connected to any group of the jumpers, and used to adjust the impedance value of the impedance simulation circuit by connecting to different jumpers;

[0052] A low-pass filter circuit is connected between the audio input and the analog impedance circuit to filter out high-frequency noise from the audio signal. Specifically, the jumper is a jumper terminal, and different jumper terminals are selected via jumper caps to adjust the impedance. The impedance characteristic of a speaker measures the resistance it presents to current flow. This resistance is not a fixed value but fluctuates with the frequency of the sound being played.

[0053] In this solution, the low-pass filter circuit is responsible for performing preliminary low-pass filtering on the audio signal input from the audio input terminal, and then passes the signal to the impedance simulation circuit;

[0054] The impedance simulation circuit includes a speaker load simulation circuit and a headphone load simulation circuit. The speaker load simulation circuit simulates the load circuit of a speaker. A filtered audio signal is loaded across the simulated speaker load to simulate the load conditions of a real speaker. The headphone load simulation circuit simulates the load circuit of a headphone. An audio signal is input through the ACN3 connector (3.5mm headphone jack) and loaded across the simulated headphone load. The audio signal is processed to simulate the load characteristics of the headphone under different conditions.

[0055] By using jumpers to select different pins connected to different jumpers in the impedance simulation circuit, the impedance characteristics of the circuit can be changed, thereby simulating the performance of speakers or headphones at different frequencies. This method is very flexible because the impedance can be adjusted by conveniently moving jumpers without re-soldering or modifying the circuit. It completes the entire process from audio signal input, filtering, speaker simulation, to headphone simulation. This avoids the risks of directly using real speakers and improves test accuracy. It can be summarized as follows:

[0056] Safer: No need to use real speakers or headphones, avoiding the risk of overload and damage to the equipment.

[0057] More accurate: By simulating real load impedance characteristics, audio performance test results are closer to the performance of the device in actual use.

[0058] More flexible: The impedance value can be adjusted to adapt to speakers and headphones of different specifications, making this test system have a wider range of applications.

[0059] Simply put, the core of this solution is to simulate the load characteristics of real speakers and headphones and combine them with filtering technology to design a safe and accurate audio performance test circuit and test system. This not only solves the problems of existing technologies but also greatly improves test accuracy and equipment applicability.

[0060] In one embodiment, Figure 4 and Figure 5 As shown, the impedance simulation circuit is a speaker load simulation circuit and / or an earphone load simulation circuit.

[0061] In another embodiment, Figure 4 As shown, the speaker load simulation circuit is used to simulate the impedance characteristics of the speaker at different audio frequencies;

[0062] The speaker load simulation circuit includes inductors SL3, SL4, SL5, and SL6, resistors AR3, AR4, AR5, AR6, AR19, AR20, AR21, and AR22, and jumpers JP11, JP12, JP15, and JP16;

[0063] One end of the inductor SL3 is connected to the output terminal R+ of the low-pass filter circuit, and the other end is connected to the first pin of the jumper JP12. Resistors AR3 and AR4 are connected in parallel, and the two ends of the parallel resistor formed by the parallel connection are respectively connected to the other end of the inductor SL3 and the first pin of the jumper JP11. Resistors AR5 and AR6 are connected in parallel, and the parallel resistor formed by the parallel connection has one end connected to the second pin of the jumper JP11 and the second pin of the jumper JP12, respectively, and the other end is connected to one end of the inductor SL4. The other end of the inductor SL4 is connected to the output terminal R- of the low-pass filter circuit.

[0064] One end of inductor SL5 is connected to the output terminal L+ of the low-pass filter circuit, and the other end is connected to pin 1 of jumper JP16. Resistors AR19 and AR20 are connected in parallel, and the ends of the parallel resistor formed by the parallel connection are connected to one end of inductor SL5 and pin 1 of jumper JP15 respectively. Resistors AR21 and AR22 are connected in parallel, and the parallel resistor formed by the parallel connection has one end connected to pin 2 of jumper JP12 and pin 2 of jumper JP16 respectively, and the other end is connected to one end of inductor SL6. The other end of inductor SL6 is connected to the output terminal L- of the low-pass filter circuit. Specifically, the input signal passes through different impedance paths, and by selecting the appropriate jumper cap, the circuit can be adjusted to a specific impedance combination. This adjustable impedance allows the circuit to accurately simulate the impedance characteristics of the speaker at different frequencies, thereby simulating the actual performance of the speaker at high and mid-frequency levels.

[0065] In yet another embodiment, Figure 5 As shown, the headphone load simulation circuit is used to simulate the impedance characteristics of the headphone at different audio frequencies;

[0066] The headphone load simulation circuit includes resistors AR11, AR12, AR13, AR14, AR15, AR16, AR17, and AR18, jumpers JP7 and JP8, and connector ACN3; wherein connector ACN3 is a 3.5mm headphone jack, specifically, the headphone jack CKX-3.5-25 / black;

[0067] Connect pins 1 and 2 or pins 2 and 3 of jumper JP7 through a jumper cap; connect pins 1 and 2 or pins 2 and 3 of jumper JP8 through a jumper cap;

[0068] When the jumper cap connects the 1st and 2nd pins of jumper JP7 and the 1st and 2nd pins of jumper JP8, the load of the left and right channels of the simulated headphone is 16Ω.

[0069] When the jumper cap connects the 2nd and 3rd pins of jumper JP7, and the 2nd and 3rd pins of jumper JP8, the left and right channels are 32Ω;

[0070] Resistors AR11 and AR12 are connected in series, with the ends of the circuit connected to pin 1 of jumper JP8 and pin 3 of the connector, respectively. Resistors AR13 and AR14 are connected in series, with the ends of the circuit connected to pin 1 and pin 3 of jumper JP8, respectively. Resistors AR15 and AR16 are connected in series, with the ends of the circuit connected to pin 1 of jumper JP7 and pin 2 of the connector, respectively. Resistors AR17 and AR18 are connected in series, with the ends of the circuit connected to pin 1 and pin 3 of jumper JP7, respectively. Pin 2 of jumper JP8 and pin 2 of JP7 are connected and grounded, and pin 1 of the connector is grounded. Specifically, by connecting a parallel resistor network, the complex impedance curve of a speaker at different frequencies can be simulated. These resistor combinations allow the circuit to accurately exhibit impedance characteristics similar to those of an actual speaker within a specific frequency range, thereby simulating the speaker's true performance at different frequencies.

[0071] In yet another embodiment, Figure 3 As shown, the low-pass filter circuit includes inductors AL1, AL2, AL3, and AL4, capacitors AC1, AC2, AC3, AC4, AC5, and AC6, resistors AR1 and AR2, and jumpers JP1, JP2, JP3, JP4, JP5, JP6, JP13, and JP14;

[0072] Connect pin 1 of jumper JP13 to pin 1 of jumper JP1. Connect pin 3 of jumper JP13 to one end of inductor AL1. Connect the other end of inductor AL1 to pin 2 of capacitor AC1, pin 2 of capacitor AC3, and pin 3 of jumper JP1, respectively. Connect pin 1 of capacitor AC1 to one end of resistor AR1. Connect pin 1 of capacitor AC3 to ground.

[0073] Connect pin 1 of jumper JP14 to one end of inductor AL2. Connect the other end of inductor AL2 to the other end of resistor AR1, pin 1 of capacitor AC5, and pin 1 of jumper JP2. Connect pin 2 of capacitor AC5 to ground. Connect pin 3 of jumper JP14 to pin 3 of jumper JP2.

[0074] Connect pin 1 of jumper JP6 to pin 1 of jumper JP3. Connect pin 3 of jumper JP6 to one end of inductor AL3. Connect the other end of inductor AL3 to pin 2 of capacitor AC2, pin 1 of capacitor AC4, and pin 3 of jumper JP3 respectively. Connect pin 1 of capacitor AC2 to one end of resistor AR2. Connect pin 2 of capacitor AC4 to ground.

[0075] Connect pin 1 of jumper JP5 to one end of inductor AL4. Connect the other end of inductor AL4 to the other end of resistor AR2, pin 1 of capacitor AC6, and pin 1 of jumper JP4. Connect pin 2 of capacitor AC6 to ground. Connect pin 3 of jumper JP5 to pin 3 of jumper JP4.

[0076] The output terminal R+ of jumper JP1 is connected to one end of inductor SL3, the output terminal R- of jumper JP2 is connected to the other end of inductor SL4, the output terminal L- of jumper JP3 is connected to the other end of inductor SL6, and the output terminal L+ of jumper JP4 is connected to one end of inductor SL5. Specifically, when the audio signal passes through the power amplifier circuit, some unwanted high-frequency noise may be generated. If this noise is not removed, it will interfere with our test. To this end, this solution designs a low-pass filter, which will filter out this high-frequency noise and ensure that the audio signal entering the analog circuit is clean and free of interference. See Figure 3The right-channel audio signal is introduced into the circuit through the SPK_RP and SPK_RN connectors, where it passes through a low-pass filter composed of an inductor and capacitor. The left-channel audio signal is similarly introduced through the SPK_LP and SPK_LN connectors and undergoes the same filtering process. After these audio signals are input, they are processed by their respective filter circuits. The low-pass filter circuit processes signals of different frequencies to simulate the frequency response characteristics of a speaker. When an audio signal is input, it first passes through the low-pass filter circuit, also known as the low-pass filter. The combination of inductors and capacitors determines the characteristics of the low-pass filter, allowing the circuit to exhibit different impedance characteristics at different frequencies, effectively simulating the low-frequency response of a speaker.

[0077] pass Figures 3 to 5 By combining different circuits in this test circuit, the present invention comprehensively simulates the impedance characteristics of speakers and / or headphones at different audio frequencies through a low-pass filter circuit, a speaker load simulation circuit, and a headphone load simulation circuit. These circuits can flexibly adjust the impedance, allowing the test circuit to accurately simulate the performance of audio output devices under actual operating conditions. This is crucial for testing speaker audio performance indicators and ensuring the speaker's true performance at different audio frequencies.

[0078] In another embodiment, Figure 4 As shown, the impedance simulation circuit also includes at least one inductor and at least one resistor. Specifically, inductors and resistors are used to combine into an impedance simulation circuit, which can simulate the impedance changes of audio output devices such as speakers at different frequencies. The role of the inductor is to simulate the performance of the speaker at high frequencies, while the resistor simulates the performance at low frequencies. Through this combination, the impedance simulation circuit can exhibit an impedance similar to that of a real speaker when facing audio signals of different frequencies. Users are allowed to select different impedance values ​​(for example, 4Ω or 8Ω) as needed. Different speakers have different impedance values, and these impedance values ​​will also vary at different frequencies. By selecting the appropriate impedance value, we can more accurately simulate the behavior of different types of speakers at different frequencies.

[0079] In another embodiment, Figures 1 to 6 As shown, an audio performance test system includes: an audio generation circuit and a detection circuit.

[0080] An audio generating circuit, for generating an audio signal, having an audio input terminal;

[0081] A detection circuit is connected to the audio input terminal;

[0082] Wherein, the detection circuit is any one of the aforementioned circuits for testing the audio performance of an audio device.

[0083] The audio performance testing process of this solution can be summarized into the following steps:

[0084] S1. Signal Input and Preliminary Processing: The audio signal from the audio generation circuit (i.e., the mainboard) first passes through a Class D power amplifier, then through a low-pass filter circuit (i.e., an LC low-pass filter) to remove high-frequency components before being input into the simulated load system.

[0085] S2. Impedance matching and signal application: Select the appropriate impedance value based on the test requirements and apply the filtered audio signal to the simulated speaker or headphone load.

[0086] S3. Parameter Measurement and Analysis: Use test equipment such as an audio analyzer to measure the signals at both ends of the load. Tests include harmonic distortion, signal-to-noise ratio, and gain. By adjusting the input signal sensitivity and observing performance under different load conditions, various indicators of the power amplifier chip or audio system are evaluated.

[0087] S4. Optimization and Verification: Make adjustments based on test results, such as setting input sensitivity based on load size during software debugging, to ensure the stability and reliability of the audio system in real-world usage scenarios.

[0088] In another embodiment, an audio analyzer connected to the detection circuit is further included.

[0089] The two types of tablet motherboard audio test devices currently available on the market still have the following defects:

[0090] 1) Real speakers are very likely to burn out under maximum load, causing unnecessary losses;

[0091] 2) Use a linear load with the same resistance as the speaker for direct testing. Since the pre-stage low-pass filter uses a ferrite bead instead of an inductor, although the high-frequency portion of the signal is filtered out, the resulting signal is still contaminated with multiple harmonics in the mid- and low-frequency bands. The test results obtained by applying an impure signal to both ends of the load will have a certain error, and the sound quality played by the speaker will also be deviated;

[0092] 3) The linear load cannot simulate the real speaker impedance model at different frequencies, and the accuracy of testing and debugging audio performance indicators is insufficient.

[0093] The audio performance testing system of the present invention simulates the hardware load system of the back end of the audio power amplifier and the headphone output end to realize the performance index detection of the system audio, media audio and headphone audio of the tablet-like motherboard. From the hardware performance detection, fault detection, problem point location and problem point debugging of the tablet-like motherboard audio and headphone audio in the product development stage, to the defective product screening and stability testing in the mass production and testing stage of the tablet-like motherboard, this device plays a vital role.

[0094] Audio performance test system, including:

[0095] The low-pass filter circuit is used to implement low-pass filtering on the audio signal output by the power amplifier, filtering out high-frequency harmonic components and restoring the pure audio signal;

[0096] A speaker load simulation circuit is used to simulate an impedance model identical to that of the speaker and select and match the impedance model as needed according to different application scenarios to achieve audio performance indicator testing. The speaker load simulation circuit includes a speaker simulation load selection switching module, specifically jumpers JP11, JP12, JP15, and JP16. By selecting different jumper pin connections through jumper caps, different speaker impedance models can be switched.

[0097] The headphone load simulation circuit simulates the same impedance model as the headphones and selects and matches the impedance model as needed for different applications to detect headphone output audio performance indicators. The headphone load simulation circuit includes a headphone simulation load selection switching module, specifically jumpers JP7 and JP8. Using jumpers, different jumper pin connections are selected to switch between different headphone impedance models. The jumper can be used to select whether to connect pins 1 and 2 or pins 2 and 3 of jumper JP7; the jumper can be used to select whether to connect pins 1 and 2 or pins 2 and 3 of jumper JP8. When the jumper connects pins 1 and 2 of jumpers JP7 and JP8, the simulated headphone left and right channel load is 16Ω. When the jumper connects pins 2 and 3 of jumpers JP7 and JP8, the simulated headphone left and right channel load is 32Ω.

[0098] This solution solves the problem of inaccurate linear load test data during audio testing. At the same time, the presence of the low-pass filter ensures that the pure audio signal reaches the load end, achieving accurate detection and judgment of hardware performance. At the same time, the device realizes matching testing of different loads through the selection of multiple impedance values. Specifically:

[0099] 1. Secondary filtering: such as Figure 6As shown in the figure, the audio signal of the motherboard first passes through the Class D power amplifier and then through the low-pass filter before being added to both ends of the speaker. Since the signal obtained by the Class D power amplifier is an amplified pulse width signal, the pulse width signal carries the relevant information of the original audio signal. Assuming that the amplified pulse width signal is as follows Figure 7 The Fourier series expansion of the pulse width signal is as follows:

[0100]

[0101] The high-frequency components of the signal are filtered out after passing through the low-pass filter. Since the low-pass filter composed of magnetic beads and capacitors has an excellent filtering effect on high-frequency components at the megahertz level, there are still multiple harmonic components in the mid- and low-frequency bands mixed in the separated audio signal, such as Figure 3 As shown in the figure, LC low-pass filter circuits are added before the two load models to effectively filter out multiple harmonics in the low and mid-frequency bands to obtain relatively pure low-frequency audio signals. At the same time, at JP1-JP6, JP13, and JP14, jumpers can be used to select whether to apply the audio signal to both ends of the speaker or to both ends of the simulated load with a low-pass filter to complete the corresponding test work.

[0102] 2. Impedance adjustable: as shown in the attached Figure 4 The figure shows a circuit for simulating a speaker load system. Jumpers at JP11, JP12, JP15, and JP16 can be used to select the load impedance. For example, by selecting jumpers at JP11 and JP15, two 8Ω speakers can be simulated, thus completing the corresponding test. This circuit connects a low-DCR inductor in series across the linear load to simulate an impedance model identical to that of a real speaker. The impedance characteristics exhibited by this circuit under audio signals of different frequencies are identical to those of a real speaker.

[0103] 3. Multiple parameter index tests:

[0104] 1) For software debugging. On a tablet motherboard or TV motherboard, the main chip will directly transmit the processed audio signal to the amplifier chip. This audio signal is called the input sensitivity of the amplifier. During software debugging, the input sensitivity will be set according to the load size and the load standard rated power. Figure 4 As shown, when debugging the software, the audio analyzer can be connected to R+ and R-, and L+ and L- respectively. If the load is an 8Ω / 8W speaker, jumpers can be used to select JP11 and JP15. The input sensitivity can be adjusted through software settings. The change in the power applied to the simulated load can be observed at the audio analyzer end. When the power applied to the simulated load is 8W, the input sensitivity at this time is the input sensitivity that the software should set.

[0105] 2) Used to test various parameters of the power amplifier chip. In the process of testing the power amplifier chip, many parameters need to be tested, such as harmonic distortion test, balance test of the power amplifier chip, signal-to-noise ratio test, gain test of the power amplifier chip, etc. After confirming that the various indicators of the power amplifier chip are consistent with the description in the specification, it can be applied to the design. Figure 4 As shown, when testing the balance of an amplifier chip, connect an audio analyzer to the R+ and R- terminals, and the L+ and L- terminals, respectively. Adjust the input sensitivity so that the load operates at the standard rated power. The audio analyzer can then be used to observe the root mean square voltages (VL) and VR across the left and right channel loads. VL / VR represents the balance ratio of the amplifier chip. This solution simulates a speaker to perform the corresponding tests for each of the aforementioned amplifier chip parameters, so we will not elaborate on each one here.

[0106] 4. Headphone load impedance model: as shown in the attached Figure 2 This solution achieves coverage of conventional audio terminals by adding a headphone load impedance model. This load model also has the characteristic of adjustable impedance. Figure 5 As shown in the figure, by selecting the 1-2 contact or the 2-3 contact of the jumper JP8, the 16Ω or 32Ω headphone simulation can be realized, so as to perform targeted measurements of different indicators under different loads.

[0107] Because this solution incorporates low-pass filtering circuits and impedance simulation circuits, it achieves accurate testing of the audio performance indicators of speakers and headphones of different specifications, and realizes the technical effect of hardware performance testing of the audio circuits of commercial display motherboards with sound systems, such as tablet motherboards, TV motherboards, and advertising machine motherboards.

[0108] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A circuit for testing the audio performance of an audio device, characterized in that: include: An impedance simulation circuit, comprising at least two sets of jumpers, for simulating impedance characteristics of an audio output device at different audio frequencies; a jumper cap connected to any group of the jumpers, and used to adjust the impedance value of the impedance simulation circuit by connecting to different jumpers; The low-pass filter circuit is connected between the audio input terminal and the analog impedance circuit and is used to filter out high-frequency noise in the audio signal.

2. The circuit for testing the audio performance of an audio device according to claim 1, wherein: The impedance simulation circuit is a speaker load simulation circuit and / or an earphone load simulation circuit.

3. The circuit for testing the audio performance of an audio device according to claim 2, wherein: The speaker load simulation circuit is used to simulate the impedance characteristics of the speaker at different audio frequencies; The speaker load simulation circuit includes inductors SL3, SL4, SL5, and SL6, resistors AR3, AR4, AR5, AR6, AR19, AR20, AR21, and AR22, and jumpers JP11, JP12, JP15, and JP16; One end of the inductor SL3 is connected to the output terminal R+ of the low-pass filter circuit, and the other end is connected to the first pin of the jumper JP12. Resistors AR3 and AR4 are connected in parallel, and the two ends of the parallel resistor formed by the parallel connection are respectively connected to the other end of the inductor SL3 and the first pin of the jumper JP11. Resistors AR5 and AR6 are connected in parallel, and the parallel resistor formed by the parallel connection has one end connected to the second pin of the jumper JP11 and the second pin of the jumper JP12, respectively, and the other end is connected to one end of the inductor SL4. The other end of the inductor SL4 is connected to the output terminal R- of the low-pass filter circuit. One end of the inductor SL5 is connected to the output terminal L+ of the low-pass filter circuit, and the other end is connected to the first pin of the jumper JP16. Resistors AR19 and AR20 are connected in parallel, and the two ends of the parallel resistor formed by the parallel connection are respectively connected to one end of the inductor SL5 and the first pin of the jumper JP15. Resistors AR21 and AR22 are connected in parallel, and one end of the parallel resistor formed by the parallel connection is respectively connected to the second pin of the jumper JP12 and the second pin of the jumper JP16, and the other end is connected to one end of the inductor SL6. The other end of the inductor SL6 is connected to the output terminal L- of the low-pass filter circuit.

4. The circuit for testing the audio performance of an audio device according to claim 2, wherein: The headphone load simulation circuit is used to simulate the impedance characteristics of the headphone at different audio frequencies; The headphone load simulation circuit includes resistors AR11, AR12, AR13, AR14, AR15, AR16, AR17, AR18, jumpers JP7, JP8, and connector ACN3; Connect pins 1 and 2 or pins 2 and 3 of jumper JP7 through a jumper cap; Connect pins 1 and 2 or 2 and 3 of jumper JP8 through a jumper cap; Resistors AR11 and AR12 are connected in series, with the ends of the series circuit connected to pin 1 of jumper JP8 and pin 3 of the connector, respectively. Resistors AR13 and AR14 are connected in series, with the ends of the series circuit connected to pin 1 and pin 3 of jumper JP8, respectively. Resistors AR15 and AR16 are connected in series, with the ends of the series circuit connected to pin 1 of jumper JP7 and pin 2 of the connector, respectively. Resistors AR17 and AR18 are connected in series, with the ends of the series circuit connected to pin 1 and pin 3 of jumper JP7, respectively. Pin 2 of jumper JP8 and pin 2 of JP7 are connected and grounded. Pin 1 of the connector is grounded.

5. The circuit for testing the audio performance of an audio device according to claim 3, wherein: The low-pass filter circuit includes inductors AL1, AL2, AL3, and AL4, capacitors AC1, AC2, AC3, AC4, AC5, and AC6, resistors AR1 and AR2, and jumpers JP1, JP2, JP3, JP4, JP5, JP6, JP13, and JP14; Connect pin 1 of jumper JP13 to pin 1 of jumper JP1. Connect pin 3 of jumper JP13 to one end of inductor AL1. Connect the other end of inductor AL1 to pin 2 of capacitor AC1, pin 2 of capacitor AC3, and pin 3 of jumper JP1, respectively. Connect pin 1 of capacitor AC1 to one end of resistor AR1. Connect pin 1 of capacitor AC3 to ground. Connect pin 1 of jumper JP14 to one end of inductor AL2. Connect the other end of inductor AL2 to the other end of resistor AR1, pin 1 of capacitor AC5, and pin 1 of jumper JP2. Connect pin 2 of capacitor AC5 to ground. Connect pin 3 of jumper JP14 to pin 3 of jumper JP2. Connect pin 1 of jumper JP6 to pin 1 of jumper JP3. Connect pin 3 of jumper JP6 to one end of inductor AL3. Connect the other end of inductor AL3 to pin 2 of capacitor AC2, pin 1 of capacitor AC4, and pin 3 of jumper JP3 respectively. Connect pin 1 of capacitor AC2 to one end of resistor AR2. Connect pin 2 of capacitor AC4 to ground. Connect pin 1 of jumper JP5 to one end of inductor AL4. Connect the other end of inductor AL4 to the other end of resistor AR2, pin 1 of capacitor AC6, and pin 1 of jumper JP4. Connect pin 2 of capacitor AC6 to ground. Connect pin 3 of jumper JP5 to pin 3 of jumper JP4. The output end R+ of jumper JP1 is connected to one end of inductor SL3, the output end R- of jumper JP2 is connected to the other end of inductor SL4, the output end L- of jumper JP3 is connected to the other end of inductor SL6, and the output end L+ of jumper JP4 is connected to one end of inductor SL5.

6. The circuit for testing the audio performance of an audio device according to claim 1, wherein: The impedance simulation circuit further includes at least one inductor and at least one resistor.

7. An audio performance testing system, characterized in that: include: An audio generating circuit, for generating an audio signal, having an audio input terminal; as well as A detection circuit is connected to the audio input terminal; Wherein, the detection circuit is the circuit for testing the audio performance of an audio device as described in any one of claims 1 to 6.

8. The audio performance testing system according to claim 7, characterized in that: Also included is an audio analyzer connected to the detection circuit.

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