Audio amplifier circuit and audio playback equipment

Abstract

The present application discloses an audio amplifier circuit and an audio playback device. The audio amplifier circuit includes two audio processing circuits and a power amplifier. The first audio processing circuit is capable of filtering differential audio signals, the second audio processing circuit is capable of limiting and filtering single-ended audio signals, and the power amplifier is capable of amplifying the audio signals output by the two audio processing circuits. Based on the processing operations of the two audio processing circuits, it is possible to ensure that the differential audio signal and the single-ended audio signal transmitted to the power amplifier have good signal quality and are relatively close in amplitude. Thus, a single power amplifier can reliably amplify two different types of audio signals, effectively simplifying the structure of the audio amplifier circuit.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to an audio amplifier circuit and an audio playback device. Background Art

[0002] An audio playback device (eg, a speaker) can generally establish a communication connection with a terminal (eg, a mobile phone or a computer) via Bluetooth (BT) or a universal serial bus (USB), and play audio signals transmitted by the terminal.

[0003] Audio playback devices in related technologies typically include a Bluetooth module, a USB port, a speaker, and two power amplifiers (PAs). One PA is connected to the Bluetooth module and the speaker, respectively, to amplify the differential audio signal received by the Bluetooth module and transmit it to the speaker. The other PA is connected to the USB port and the speaker, respectively, to amplify the single-ended audio signal received by the USB port and transmit it to the speaker.

[0004] However, since two PAs need to be configured in the audio playback device to respectively amplify the power of the differential audio signal and the single-ended audio signal, the structure of the audio playback device is relatively complicated. Summary of the Invention

[0005] This application provides an audio amplifier circuit and an audio playback device, which can solve the technical problem of the relatively complex structure of audio playback devices in related technologies. The technical solution is as follows:

[0006] In one aspect, an audio amplification circuit is provided, the audio amplification circuit comprising: a first audio processing circuit, a second audio processing circuit, and a power amplifier;

[0007] The first audio processing circuit has a differential input terminal and a differential output terminal, the differential output terminal is connected to the input terminal of the power amplifier, and the first audio processing circuit is used to filter the differential audio signal received through the differential input terminal and transmit the filtered differential audio signal to the power amplifier;

[0008] The second audio processing circuit has a single-ended input and a single-ended output, the single-ended output being connected to the input of the power amplifier, and the second audio processing circuit being configured to limit and filter a single-ended audio signal received through the single-ended input, and transmit the limited and filtered single-ended audio signal to the power amplifier;

[0009] The power amplifier is used to amplify the power of the received audio signal.

[0010] Optionally, the first audio processing circuit includes: a first filtering circuit and a second filtering circuit;

[0011] The first filter circuit is connected to the differential input terminal and the second filter circuit respectively, and the first filter circuit is used to perform a first-stage filtering on the differential audio signal;

[0012] The second filtering circuit is also connected to the differential output terminal, and is used to perform second-stage filtering on the differential audio signal after the first-stage filtering.

[0013] Optionally, the differential input terminal includes a first input terminal and a second input terminal; the first filtering circuit includes: a first capacitor, a first resistor, a second capacitor and a second resistor;

[0014] Wherein, the first capacitor and the first resistor are connected in series between the first input terminal and the first input end of the second filter circuit;

[0015] The second capacitor and the second resistor are connected in series between the second input terminal and the second input end of the second filter circuit.

[0016] Optionally, the differential output end includes a first output terminal and a second output terminal; the second filtering circuit includes: a third capacitor, a third resistor, a fourth capacitor and a fourth resistor;

[0017] Wherein, the third capacitor and the third resistor are connected in series between the first output end and the first output terminal of the first filter circuit;

[0018] The fourth capacitor and the fourth resistor are connected in series between the second output end and the second output terminal of the first filter circuit.

[0019] Optionally, the first audio processing circuit further includes a third filtering circuit, the third filtering circuit including: at least one of a fifth capacitor, a sixth capacitor, a fifth resistor, a sixth resistor, and a seventh resistor;

[0020] Wherein, one end of the fifth capacitor is connected to the first output end of the first filter circuit, and the other end of the fifth capacitor is connected to the second output end of the first filter circuit;

[0021] The sixth capacitor and the fifth resistor are connected in series between the first output terminal and the second output terminal of the first filter circuit;

[0022] One end of the sixth resistor is connected to the second output end of the first filter circuit, and the other end of the sixth resistor is connected to a target node, which is a connection node between the fourth capacitor and the fourth resistor;

[0023] One end of the seventh resistor is connected to the first output end of the first filter circuit, and the other end of the seventh resistor is connected to the ground end.

[0024] Optionally, the first audio processing circuit further includes: a common mode inductor;

[0025] The common-mode inductor is connected in series between the first filter circuit and the second filter circuit.

[0026] Optionally, the second audio circuit includes: a fourth filter circuit and a limiting filter circuit;

[0027] The fourth filtering circuit is connected to the single-ended input terminal and the amplitude limiting filtering circuit respectively, and the fourth filtering circuit is used to perform low-pass filtering on the single-ended audio signal;

[0028] The amplitude limiting filter circuit is also connected to the single-ended output end, and is used to limit the single-ended audio signal after low-pass filtering, and perform high-pass filtering on the single-ended audio signal after limiting.

[0029] Optionally, the fourth filtering circuit includes: a filtering inductor and a seventh capacitor;

[0030] One end of the filter inductor is connected to the single-ended input end, and the other end of the filter inductor is connected to the limiting filter circuit;

[0031] One end of the seventh capacitor is connected to the amplitude limiting filter circuit, and the other end of the seventh capacitor is connected to the ground.

[0032] Optionally, the fourth filtering circuit further includes: an eighth capacitor;

[0033] The eighth capacitor and the filter inductor are connected in series between the single-ended input terminal and the amplitude limiting filter circuit.

[0034] Optionally, the amplitude limiting filter circuit includes: an eighth resistor, a ninth resistor and a ninth capacitor;

[0035] Wherein, one end of the eighth resistor is connected to the fourth filter circuit, and the other end of the eighth resistor is connected to the ground end;

[0036] The ninth resistor and the ninth capacitor are connected in series between the fourth filter circuit and the single-ended output terminal.

[0037] On the other hand, an audio playback device is provided, comprising: the audio amplification circuit provided in the above aspect, a first signal transmission circuit, a second signal transmission circuit, and a speaker;

[0038] The differential input terminal of the audio amplifier circuit is connected to the first signal transmission circuit, the single-ended input terminal of the audio amplifier circuit is connected to the second signal transmission circuit, and the output terminal of the audio amplifier circuit is connected to the speaker;

[0039] The first signal transmission circuit is used to transmit a differential audio signal to the audio amplification circuit, the second signal transmission circuit is used to transmit a single-ended audio signal to the audio amplification circuit, and the speaker is used to play the audio signal output by the audio amplification circuit.

[0040] Optionally, the audio playback device further includes: a main control chip and at least one microphone interface circuit;

[0041] The main control chip is respectively connected to the at least one microphone interface circuit, the first signal transmission circuit and the second signal transmission circuit, and the main control chip is used to transmit the audio signal collected by the at least one microphone interface circuit to the first signal transmission circuit and / or the second signal transmission circuit.

[0042] Optionally, the audio playback device further includes: an audio retrieving circuit;

[0043] The audio sampling circuit is connected to the output end of the audio amplifier circuit, and is used to sample the audio signal output by the audio amplifier circuit to obtain a sampled signal;

[0044] The main control chip is also connected to the audio echo circuit, and the main control chip is further used to perform echo cancellation processing on the audio signal collected by the at least one microphone interface circuit based on the sampling signal.

[0045] The beneficial effects of the technical solution provided by this application include at least:

[0046] The present application provides an audio amplifier circuit and an audio playback device. The audio amplifier circuit includes two audio processing circuits and a power amplifier. The first audio processing circuit is capable of filtering differential audio signals, the second audio processing circuit is capable of limiting and filtering single-ended audio signals, and the power amplifier is capable of amplifying the audio signals output by the two audio processing circuits. Based on the processing operations of the two audio processing circuits, it can be ensured that the signal quality of the differential audio signal and the single-ended audio signal transmitted to the power amplifier is good and the amplitude is relatively close. As a result, two different types of audio signals can be reliably amplified using one power amplifier, which effectively simplifies the structure of the audio amplifier circuit and reduces the cost of the audio amplifier circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 This is a structural diagram of an audio playback device provided in an embodiment of the present application;

[0049] Figure 2 This is a structural diagram of an audio amplifier circuit provided in an embodiment of the present application;

[0050] Figure 3 is a structural diagram of a first audio processing circuit provided in an embodiment of the present application;

[0051] Figure 4 is a structural diagram of another first audio processing circuit provided in an embodiment of the present application;

[0052] Figure 5 is a structural diagram of a second audio processing circuit provided in an embodiment of the present application;

[0053] Figure 6 This is a structural diagram of another audio playback device provided in an embodiment of the present application;

[0054] Figure 7 This is a structural diagram of another audio playback device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0056] Figure 1 This is a structural diagram of an audio playback device provided in an embodiment of the present application. Figure 1 As shown, the audio playback device may include: an audio amplifying circuit 10 , a first signal transmission circuit 20 , a second signal transmission circuit 30 and a speaker 40 .

[0057] See also Figure 1 The differential input terminal IN1 of the audio amplifier circuit 10 is connected to the first signal transmission circuit 20, the single-ended input terminal IN2 of the audio amplifier circuit 10 is connected to the second signal transmission circuit 30, and the output terminal OUT of the audio amplifier circuit 10 is connected to the speaker 40.

[0058] The first signal transmission circuit 20 can establish a communication connection with a first terminal and is used to transmit a differential audio signal from the first terminal to the audio amplification circuit 10. The second signal transmission circuit 30 can establish a communication connection with a second terminal and is used to transmit a single-ended audio signal from the second terminal to the audio amplification circuit 10. The speaker 40 is used to play the audio signal output by the audio amplification circuit 10.

[0059] The first terminal and the second terminal may be electronic devices such as mobile phones or computers. The audio playback device may be an electronic device that can be used for sound amplification, such as a speaker or a conference phone.

[0060] The audio playback device provided in the embodiment of the present application can receive differential audio signals and single-ended audio signals respectively through different signal transmission circuits, and can amplify different types of audio signals through audio amplification circuits, and has high flexibility in use.

[0061] Figure 2 This is a structural diagram of an audio amplifier circuit provided by an embodiment of the present application. The audio amplifier circuit can be applied to Figure 1 The audio playback device shown. Figure 2 The audio amplifying circuit 10 includes: a first audio processing circuit 110 , a second audio processing circuit 120 and a power amplifier 130 .

[0062] The first audio processing circuit 110 has a differential input terminal and a differential output terminal. The differential input terminal includes a first input terminal I11 and a second input terminal I12, and the differential output terminal includes a first output terminal O11 and a second output terminal O12. The differential output terminal of the first audio processing circuit 110 is connected to the input terminal of the power amplifier 130. Figure 2 As shown, the power amplifier 130 includes two input terminals I31 and I32, a first output terminal O11 connected to the input terminal I31, and a second output terminal O12 connected to the input terminal I32. The first audio processing circuit 110 is configured to filter the differential audio signal received via the differential input terminal and transmit the filtered differential audio signal to the power amplifier 130.

[0063] The second audio processing circuit 120 has a single-ended input terminal I21 and a single-ended output terminal O21. The single-ended output terminal O21 is connected to the input terminal I32 of the power amplifier 130. The second audio processing circuit 120 is configured to limit and filter the single-ended audio signal received through the single-ended input terminal I21, and transmit the limited and filtered single-ended audio signal to the power amplifier 130.

[0064] The power amplifier 130 is configured to amplify the power of the received audio signal. The audio signal received by the power amplifier 130 may include at least one of a filtered differential audio signal and a filtered single-ended audio signal.

[0065] In the embodiment of the present application, the first audio processing circuit 110 filters the received differential audio signal to remove noise from the differential audio signal, thereby improving the signal quality of the differential audio signal transmitted to the power amplifier 130. The second audio processing circuit 120 limits and filters the received single-ended audio signal to reduce the amplitude of the single-ended audio signal and reduce noise from the single-ended audio signal. By filtering the single-ended audio signal, the signal quality of the single-ended audio signal transmitted to the power amplifier 130 can be improved.

[0066] Furthermore, since the amplitude of a single-ended audio signal is typically greater than that of a differential audio signal, the amplitude of the single-ended audio signal can be reduced so that the amplitude of the differential audio signal transmitted to the power amplifier 130 is closer to that of the single-ended audio signal. This ensures that the amplitudes of both the differential audio signal and the single-ended audio signal transmitted to the power amplifier 130 are within the rated input voltage range of the power amplifier 130. This allows, on the one hand, a single power amplifier 130 to effectively amplify two different types of audio signals; on the other hand, it ensures that the power amplifier 130 provides consistent amplification for the two different types of audio signals, thus preventing significant volume differences when the speakers play different types of audio signals.

[0067] For example, the second audio processing circuit 120 may limit the received single-ended audio signal so that the voltages applied to the input terminal I32 of the power amplifier 130 by the second audio processing circuit 120 and the first audio processing circuit 110 are equal or approximately equal.

[0068] It is understandable that in a scenario where the power amplifier 130 simultaneously receives a differential audio signal and a single-ended audio signal, if there is a significant amount of noise in the differential audio signal and / or the single-ended audio signal, the differential audio signal and the single-ended audio signal may interfere with each other, resulting in poor signal quality of the audio signal output by the power amplifier 130. Furthermore, if the amplitude of the differential audio signal transmitted to the power amplifier 130 differs significantly from that of the single-ended audio signal, the single-ended audio signal may interfere with the differential audio signal.

[0069] In the embodiment of the present application, since the differential audio signal and the single-ended audio signal can be filtered separately by two audio processing circuits, interference between the differential audio signal and the single-ended audio signal can be effectively reduced. Furthermore, since the single-ended audio signal can be limited by the second audio processing circuit 120, interference with the differential audio signal can be effectively reduced, ensuring high signal quality for both the differential audio signal and the single-ended audio signal output by the power amplifier 130.

[0070] In summary, an embodiment of the present application provides an audio amplifier circuit, which includes two audio processing circuits and a power amplifier. The first audio processing circuit is capable of filtering differential audio signals, the second audio processing circuit is capable of limiting and filtering single-ended audio signals, and the power amplifier is capable of amplifying the audio signals output by the two audio processing circuits. Based on the processing operations of the two audio processing circuits, it is possible to ensure that the differential audio signal and the single-ended audio signal transmitted to the power amplifier have good signal quality and are relatively close in amplitude. Thus, a single power amplifier can be used to reliably amplify two different types of audio signals, effectively simplifying the structure of the audio amplifier circuit and reducing the cost of the audio amplifier circuit.

[0071] Furthermore, when the power amplifier simultaneously amplifies two different types of audio signals, the interference between the two different types of audio signals is low, thereby ensuring that the audio signal output by the power amplifier has high signal quality.

[0072] Figure 3 is a structural diagram of a first audio processing circuit provided by an embodiment of the present application. Figure 3 The first audio processing circuit 110 may include a first filter circuit 1101 and a second filter circuit 1102. The first filter circuit 1101 is connected to the differential input terminal and the second filter circuit 1102, respectively. The first filter circuit 1101 is configured to perform a first-stage filtering on the differential audio signal. The second filter circuit 1102 is connected to the differential output terminal and is configured to perform a second-stage filtering on the differential audio signal after the first-stage filtering.

[0073] The first filter circuit 1101 performs a first-stage filtering on the differential audio signal to remove noise from the differential audio signal. The second filter circuit 1102 performs a second-stage filtering on the differential audio signal after the first-stage filtering to remove noise generated during transmission of the differential audio signal by the audio amplifier circuit 10. This improves the signal quality of the differential audio signal output by the first audio processing circuit 110. The first-stage filtering may be high-pass filtering or low-pass filtering, and the second-stage filtering may be high-pass filtering or low-pass filtering.

[0074] Continue to refer Figure 3 The first filter circuit 1101 may include: a first capacitor C1, a first resistor R1, a second capacitor C2, and a second resistor R2. The first capacitor C1 and the first resistor R1 are connected in series between a first input terminal I11 and a first input end of the second filter circuit 1102. The second capacitor R2 and the second resistor R2 are connected in series between a second input terminal I12 and a second input end of the second filter circuit 1102.

[0075] It is understandable that the first capacitor C1 and the first resistor R1 in the first filter circuit 1101 can form an RC filter circuit, and the second capacitor C2 and the second resistor R2 can also form an RC filter circuit. For example, both of the two RC filter circuits can be RC high-pass filter circuits. The two RC high-pass filter circuits can perform high-pass filtering on the differential audio signal inputted at the differential input end, that is, the two RC high-pass filter circuits can filter out low-frequency noise signals whose signal frequency is lower than the cutoff frequency f1. The calculation formula for the cutoff frequency f1 of the two RC high-pass filter circuits can be expressed as:

[0076]

[0077] For the RC high-pass filter circuit composed of the first capacitor C1 and the first resistor R1, R = r1 and C = c1 in the above formula. For the RC high-pass filter circuit composed of the second capacitor C2 and the second resistor R2, R = r2 and C = c2 in the above formula. Here, r1 is the resistance value of the first resistor R1, r2 is the resistance value of the second resistor R2, c1 is the capacitance value of the first capacitor C1, and c2 is the capacitance value of the second capacitor C2.

[0078] For example, in the embodiment of the present application, the capacitance value c1 of the first capacitor C1 can be 47×10 3 The resistance value r1 of the first resistor R1 can be 33 kilo-ohms (kΩ), and the capacitance value c2 of the second capacitor C2 can be 47×10 3 pF, the resistance value r2 of the second resistor R2 can be 33 kΩ.

[0079] In the embodiment of the present application, the first capacitor C1 and the first resistor R1, as well as the second capacitor C2 and the second resistor R2 in the first filter circuit 1101, can also function as impedance matching. By properly setting the resistance values of the first resistor R1 and the second resistor R2, as well as the capacitance values of the first capacitor C1 and the second capacitor C2, an impedance matching effect can be achieved, thereby effectively suppressing reflections of the differential audio signal. This ensures that the signal quality of the differential audio signal transmitted to the power amplifier 130 is high.

[0080] Continue to refer Figure 3 The second filter circuit 1102 may include: a third capacitor C3, a third resistor R3, a fourth capacitor C4, and a fourth resistor R4. The third capacitor C3 and the third resistor R3 are connected in series between the first output end of the first filter circuit 1101 and the first output terminal O11. The fourth capacitor C4 and the fourth resistor R4 are connected in series between the second output end of the first filter circuit 1101 and the second output terminal O12.

[0081] It is understood that the third capacitor C3 and the third resistor R3 of the second filter circuit 1102 can form an RC filter circuit, and the fourth capacitor C4 and the fourth resistor R4 can also form an RC filter circuit. For example, both of the two RC filter circuits can be RC high-pass filter circuits. The two RC high-pass filter circuits can filter out low-frequency signals whose signal frequencies are lower than the cutoff frequency f2. The calculation formula for the cutoff frequency f2 of the two RC high-pass filter circuits can be expressed as:

[0082]

[0083] Among them, R am is the input resistor integrated inside the power amplifier 130. For the RC high-pass filter circuit composed of the third capacitor C3 and the third resistor R3, R in the above formula in =r3,C in = c3. For the RC high-pass filter circuit composed of the fourth capacitor C4 and the fourth resistor R4, R in =r4,C in =c4. Wherein, r3 is the resistance value of the third resistor R3, r4 is the resistance value of the fourth resistor R4, c3 is the capacitance value of the third capacitor C3, and c4 is the capacitance value of the fourth capacitor C4.

[0084] For example, in the embodiment of the present application, the capacitance value c3 of the third capacitor C3 can be 10×10 4 pF, the resistance value of the third resistor R3 can be 68 ohms (Ω), and the capacitance value c4 of the fourth capacitor C4 can be 10×10 4 pF, the resistance value r4 of the fourth resistor R4 can be 68Ω.

[0085] It is understood that the two signal lines transmitting the differential audio signals in the first audio processing circuit 110 are relatively long and close together. During transmission, the differential audio signals are prone to generating additional noise signals, resulting in poor quality of the audio signals output by the audio amplifier circuit 110. The two RC filter circuits in the second filter circuit 1102 can perform a second stage of filtering on the differential audio signals after the first stage of filtering, thereby effectively filtering out the additional noise signals generated during the transmission of the differential audio signals.

[0086] Alternatively, as Figure 3 As shown, the first audio processing circuit 110 may further include a third filtering circuit 1103. The third filtering circuit 1103 may include: at least one of a fifth capacitor C5, a sixth capacitor C6, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7. For example, Figure 3 The third filtering circuit 1103 shown includes a fifth capacitor C5, a sixth capacitor C6, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7.

[0087] One end of the fifth capacitor C5 is connected to the first output terminal of the first filter circuit 1101, and the other end of the fifth capacitor is connected to the second output terminal of the first filter circuit 1101. A sixth capacitor C6 and a fifth resistor R5 are connected in series between the first output terminal and the second output terminal of the first filter circuit 1101. One end of the sixth resistor R6 is connected to the second output terminal of the first filter circuit 1101, and the other end of the sixth resistor R6 is connected to the target node, which is the connection node between the fourth capacitor C4 and the fourth resistor R4. One end of the seventh resistor R7 is connected to the first output terminal of the first filter circuit 1101, and the other end of the seventh resistor R7 is connected to the ground terminal.

[0088] It is understandable that by adopting different combinations of resistors and capacitors to form the third filter circuit 1103, the third filter circuit 1103 can realize the functions of high-pass filtering, low-pass filtering or band-pass filtering. In addition, by adjusting the resistance value of the resistor and / or the capacitance value of the capacitor in the third filter circuit 1103, the amplitude and phase of the differential audio signal can be adjusted, thereby achieving high-frequency boost or high-frequency attenuation of the differential audio signal, or, achieving low-frequency boost or low-frequency attenuation. That is, by adjusting the resistance value of the resistor and / or the capacitance value of the capacitor in the third filter circuit 1103, different equalizer (EQ) curves can be adjusted to meet the different sound requirements of different users. Accordingly, the third filter circuit 1103 can also be called a tuning circuit.

[0089] It can also be understood that the sixth resistor R6 in the third filter circuit 1103 and the fourth capacitor C4 in the second filter circuit 1102 can form an RC parallel resonant frequency selection circuit, and the sixth capacitor R6 and the fifth resistor R5 in the third filter circuit 1103 can form an RC series resonant frequency selection circuit.

[0090] The RC parallel resonant frequency selection circuit can transmit, to the second output terminal O12, the differential audio signal within the first frequency range outputted from the second output terminal of the first filter circuit 1101. In other words, the RC parallel resonant frequency selection circuit can attenuate, or filter out, audio signals outside the first frequency range.

[0091] The RC series resonant frequency selection circuit can transmit the differential audio signal within the second frequency range, output from the second output terminal of the first filter circuit 1101, to the connection node between the first resistor R1 and the third capacitor C3. The differential audio signal within the second frequency range can then be directed to the ground terminal via the seventh resistor R7. In other words, the RC parallel resonant frequency selection circuit can attenuate, or filter out, audio signals outside the second frequency range.

[0092] In the embodiment of the present application, when designing the RC parallel resonant frequency selection circuit and the RC series resonant frequency selection circuit, the first frequency range and the second frequency range can be determined based on the performance requirements of the audio playback device. Furthermore, the resistance value of the sixth resistor R6 and the capacitance value of the fourth capacitor C4 in the RC parallel resonant frequency selection circuit can be determined based on the first frequency range, and the resistance value of the fifth resistor R5 and the capacitance value of the sixth capacitor C6 in the RC series resonant frequency selection circuit can be determined based on the second frequency range.

[0093] Assuming that the first frequency range is one of the low frequency range and the high frequency range, and the second frequency range is the other of the low frequency range and the high frequency range, the high frequency range can be represented as a range with a center frequency of the first frequency selection point f3, the low frequency range can be represented as a range with a center frequency of the second frequency selection point f4, and f3>f4. Alternatively, the high frequency range can be represented as a range with a center frequency of the second frequency selection point f4, the low frequency range can be represented as a range with a center frequency of the first frequency selection point f3, and f3>f4. <f4。

[0094] For the first frequency selection point f3, its calculation formula can be expressed as:

[0095]

[0096] In the above formula, r6 is the resistance value of the sixth resistor R6, and c4 is the capacitance value of the fourth capacitor C4.

[0097] For the second frequency selection point f4, its calculation formula can be expressed as:

[0098]

[0099] Wherein, r5 in the above formula is the resistance value of the fifth resistor R5, and c6 is the capacitance value of the sixth capacitor C6.

[0100] It is understood that the first frequency selection point f3 can be referred to as the resonance point of the RC parallel resonant frequency selection circuit, and the second frequency selection point f4 can be referred to as the resonance point of the RC series resonant frequency selection circuit. In the audio signal output from the second output terminal of the first filter circuit 1101, the farther the signal frequency is from the frequency selection point, the greater the attenuation of the audio signal by the resonant frequency selection circuit.

[0101] As previously mentioned, the RC parallel resonant frequency selection circuit can attenuate audio signals outside a first frequency range, while the RC series resonant frequency selection circuit can attenuate audio signals outside a second frequency range. The degree of audio signal attenuation achieved by the resonant frequency selection circuit is positively correlated with the circuit impedance of the resonant frequency selection circuit. That is, the greater the circuit impedance of the resonant frequency selection circuit, the greater the degree of audio signal attenuation achieved by the resonant frequency selection circuit.

[0102] For the RC parallel resonant frequency selection circuit, the calculation formula of the circuit impedance value Z1 can be expressed as:

[0103] Z1=r6-jX c4 ,in,

[0104] In the above formula, X c4 is the capacitive reactance of the fourth capacitor C4 (i.e., the resistance of the fourth capacitor C4 to the AC signal). f0 is the frequency of the differential audio signal, and j is an imaginary unit. It can be understood that when f0 = f4, Z1 = r4, and the circuit impedance of the RC parallel resonant frequency selection circuit is minimum.

[0105] For the RC series resonant frequency selection circuit, the calculation formula of the circuit impedance value Z2 can be expressed as:

[0106] in,

[0107] In the above formula, X c6 is the capacitive reactance of the sixth capacitor C6 (ie, the blocking effect of the sixth capacitor C6 on the AC signal). When f0=f4, Z2=r6, and the circuit impedance value of the RC series resonant frequency selection circuit is minimum.

[0108] In the embodiment of the present application, the circuit impedance value Z1 of the RC parallel resonant frequency selection circuit and the circuit impedance value Z2 of the RC series resonant frequency selection circuit can be adjusted by adjusting the capacitance value of each capacitor and the resistance value of each resistor in the resonant circuit. Furthermore, the gain of the audio signal outputted by the second output terminal O12 of the first audio processing circuit 110 can be flexibly adjusted.

[0109] Continue to refer Figure 4The fifth capacitor C5 in the third filter circuit 1103 can function as a high-frequency bypass. Specifically, the fifth capacitor C5 can pass high-frequency harmonics (i.e., noise signals) in the audio signal, allowing these high-frequency harmonics to be transmitted through the seventh resistor R7 and drained to the ground terminal. Consequently, the audio signal transmitted from the first audio processing circuit 110 to the input terminal I32 of the power amplifier 130 contains less noise. Based on the above analysis, it can be seen that the fifth capacitor C5 can improve the signal-to-noise ratio (SNR) of the audio signal received by the input terminal I32 of the power amplifier 130.

[0110] Alternatively, as Figure 4 As shown, the first audio processing circuit 110 may further include a common-mode inductor L0 connected in series between the first filter circuit 1101 and the second filter circuit 1102 .

[0111] The common-mode inductor L0 can suppress common-mode interference in the differential audio signal. It is understood that the differential audio signal output by the first filter circuit 1101 may generate common-mode interference during transmission, i.e., a changing high-frequency interference signal, which can affect the signal quality of the differential audio signal. When the common-mode interference current, i.e., the common-mode current, passes through the common-mode inductor L0, the inductance of the common-mode inductor L0 increases, and the common-mode current is suppressed and attenuated, thereby suppressing the common-mode interference in the differential audio signal and improving the signal quality of the differential audio signal.

[0112] For example, in the embodiment of the present application, the impedance value of the common mode inductor L0 is 35Ω when the signal frequency is 100 megahertz (MHz).

[0113] Figure 5 This is a schematic diagram of the structure of a second audio processing circuit provided in an embodiment of the present application, see Figure 5 The second audio circuit 120 may include a fourth filter circuit 1201 and a limiting filter circuit 1202. The fourth filter circuit 1201 is connected to the single-ended input terminal I21 and the limiting filter circuit 1202, respectively. The fourth filter circuit 1201 is configured to perform low-pass filtering on the single-ended audio signal. The limiting filter circuit 1202 is also connected to the single-ended output terminal O21. The limiting filter circuit 1202 is configured to limit the low-pass filtered single-ended audio signal and to perform high-pass filtering on the limited single-ended audio signal.

[0114] It can be understood that the fourth filter circuit 1201 and the limiting filter circuit 1202 can form a bandpass filter circuit, which can filter out noise signals with frequencies outside the cutoff frequency, that is, high-frequency noise and low-frequency noise signals, thereby improving the signal quality of the single-ended audio signal transmitted to the power amplifier 130.

[0115] By adjusting the amplitude of the single-ended audio signal, the limiting filter circuit 1202 can prevent significant fluctuations in the amplitude difference of the audio signals received by the two input terminals I31 and I32 of the power amplifier 130. This not only enables the power amplifier 130 to effectively amplify both differential and single-ended audio signals, but also ensures that the power amplifier 130 provides consistent amplification for the two different types of audio signals, thus preventing significant volume differences when the speakers play different types of audio signals.

[0116] Optionally, refer to Figure 5 The fourth filter circuit 1201 may include a filter inductor L1 and a seventh capacitor C7. One end of the filter inductor L1 is connected to the single-ended input terminal I21, and the other end of the filter inductor L1 is connected to the limiting filter circuit 1202. One end of the seventh capacitor C7 is connected to the limiting filter circuit 1202, and the other end of the seventh capacitor C7 is connected to the ground terminal.

[0117] It is understood that the filter inductor L1 and the seventh capacitor C7 in the fourth filter circuit 1201 can form an LC low-pass filter circuit, which can filter out audio signals with a signal frequency higher than the cutoff frequency f5, that is, high-frequency noise signals. The calculation formula for the cutoff frequency f5 of the LC low-pass filter circuit can be expressed as:

[0118]

[0119] Wherein, l1 in the above formula is the inductance value of the filter inductor L1, and c7 is the capacitance value of the seventh capacitor C7. For example, in the embodiment of the present application, the inductance value l1 of the filter inductor L1 can be 68 microhenries (μH), and the capacitance value c7 of the seventh capacitor C7 can be 82×10 3 pF. The calculation formula of the quality factor Q of the LC low-pass filter circuit can be expressed as:

[0120]

[0121] Among them, R L The input resistor is integrated into the input terminal I32 of the power amplifier 130 .

[0122] Optionally, refer to Figure 5 The fourth filter circuit 1201 further includes: an eighth capacitor C8. The eighth capacitor C8 and the filter inductor L1 are connected in series between the single-ended input terminal I21 and the limiting filter circuit 1202. For example, referring to Figure 5One end of the eighth capacitor C8 is connected to the single-ended input terminal I21, and the other end is connected to one end of the filter inductor L1. The other end of the filter inductor L1 is connected to one end of the seventh capacitor C1. The capacitance value of the eighth capacitor C8 can be 33×10 3 pF.

[0123] In the embodiment of the present application, the eighth capacitor C8 can isolate the low-frequency signal in the single-ended audio signal, that is, the low-frequency noise signal, thereby effectively filtering out the low-frequency noise signal in the single-ended audio signal. It is understandable that the LC low-pass filter circuit in the fourth filter circuit 1201 can only filter out high-frequency noise signals whose signal frequency is higher than the cut-off frequency f5, and cannot effectively filter out the low-frequency noise signal in the single-ended audio signal. After configuring the eighth capacitor C8 before the LC low-pass filter circuit, it can be ensured that the fourth filter circuit 1201 can effectively filter out the high-frequency noise signal and the low-frequency noise signal in the single-ended audio signal, thereby ensuring that the signal quality of the single-ended audio signal output by the fourth filter circuit 1201 is good.

[0124] Optionally, refer to Figure 5 The limiting filter circuit 1202 may include an eighth resistor R8, a ninth resistor R9, and a ninth capacitor C9. One end of the eighth resistor R8 is connected to the fourth filter circuit 1201, and the other end of the eighth resistor R8 is connected to ground. The ninth resistor R9 and the ninth capacitor C9 are connected in series between the fourth filter circuit 1201 and the single-ended output terminal O21.

[0125] It is understood that the eighth resistor R8 and the ninth capacitor C9 in the limiting filter circuit 1202 can form an RC high-pass filter circuit. The RC filter circuit can further filter out low-frequency noise signals in the single-ended audio signal output by the fourth filter circuit 1201. That is, the RC high-pass filter circuit can filter out noise signals with a signal frequency lower than the cutoff frequency f6. The calculation formula of the cutoff frequency f6 of the RC high-pass filter circuit can be expressed as:

[0126]

[0127] Wherein, r8 is the resistance value of the eighth resistor R8, and c9 is the capacitance value of the ninth capacitor C9. For example, in the embodiment of the present application, the resistance value r8 of the eighth resistor R8 can be 180 kΩ, and the capacitance value c9 of the ninth capacitor C9 can be 10×10 4 pF.

[0128] In the embodiment of the present application, the eighth resistor R8 and the ninth resistor R9 in the limiting filter circuit 1202 can form a voltage-divider current-limiting circuit. By setting the resistance values of the eighth resistor R8 and the ninth resistor R9, the voltage of the single-ended audio signal output by the limiting filter circuit 1202 can be adjusted, that is, the amplitude of the single-ended audio signal transmitted to the power amplifier 130 can be adjusted. For example, when the resistance value r8 of the eighth resistor R8 is 180 kΩ, the resistance value r9 of the ninth resistor R9 can be 33 kΩ.

[0129] Figure 6 This is a schematic diagram of the structure of another audio amplifier circuit provided by an embodiment of the present application. Figure 6 As shown, the first audio processing circuit 110 and the second audio processing circuit 120 in the audio amplifier circuit can be integrated into an audio filter chip. The power amplifier 130 can be a power amplifier chip. Figure 6 The audio filter circuit has a differential input, a single-ended input I21, and a differential output. The differential input includes a first input terminal I11 and a second input terminal I12. The differential input includes a first output terminal O11 and a second output terminal O12. It is understood that the second output terminal O12 can be connected to the single-ended output O21 of the second audio processing circuit 120. The power amplifier 130 has two inputs I31 and I32, which are respectively connected to the two output terminals O11 and O12 of the audio filter circuit. The power amplifier 130 has two outputs O31 and O32, which serve as the output terminal OUT of the audio amplifier circuit 10 and are connected to the speaker 40.

[0130] Optionally, the first input terminal I11 may be a negative input terminal, and the second input terminal I12 may be a positive input terminal. The first output terminal O11 may be a negative output terminal, and the second output terminal O12 may be a positive output terminal. Accordingly, the input terminal I31 of the power amplifier 130 is a negative input terminal, and the input terminal I32 is a positive input terminal. The output terminal O31 of the power amplifier 130 is a negative output terminal, and the output terminal O32 is a positive output terminal.

[0131] In summary, an embodiment of the present application provides an audio amplifier circuit, which includes two audio processing circuits and a power amplifier. The first audio processing circuit is capable of filtering differential audio signals, the second audio processing circuit is capable of limiting and filtering single-ended audio signals, and the power amplifier is capable of amplifying the audio signals output by the two audio processing circuits. Based on the processing operations of the two audio processing circuits, it is possible to ensure that the differential audio signal and the single-ended audio signal transmitted to the power amplifier have good signal quality and are relatively close in amplitude. Thus, a single power amplifier can be used to reliably amplify two different types of audio signals, effectively simplifying the structure of the audio amplifier circuit and reducing the cost of the audio amplifier circuit.

[0132] Furthermore, when the power amplifier simultaneously amplifies two different types of audio signals, the interference between the two different types of audio signals is low, thereby ensuring that the audio signal output by the power amplifier has high signal quality.

[0133] The present application also provides an audio playback device. Figure 1 The audio playback device includes: an audio amplifier circuit 10 as provided in the above embodiment, a first signal transmission circuit 20, a second signal transmission circuit 30, and a speaker 40. The differential input terminal IN1 of the audio amplifier circuit 10 is connected to the first signal transmission circuit 20, the single-ended input terminal IN2 of the audio amplifier circuit is connected to the second signal transmission circuit 30, and the output terminal OUT of the audio amplifier circuit 10 is connected to the speaker 40.

[0134] The first signal transmission circuit 20 is used to transmit differential audio signals to the audio amplifier circuit 10, and the second signal transmission circuit 30 is used to transmit single-ended audio signals to the audio amplifier circuit 10. The audio amplifier circuit 10 can filter and amplify the received differential audio signals, and can filter, limit, and amplify the received single-ended audio signals. The audio amplifier circuit 10 can also transmit the processed audio signals to the speaker 40 for playback.

[0135] In the embodiment of the present application, the first signal transmission circuit 20 can be a Bluetooth module, or can be called a Bluetooth chip. Accordingly, the first signal transmission circuit 20 can establish a Bluetooth connection with a first terminal (such as a mobile phone or a computer) and can receive the differential audio signal transmitted by the first terminal.

[0136] The second signal transmission circuit 30 may be a universal serial bus (USB) interface. Accordingly, the second signal transmission circuit 30 may establish a USB connection with a second terminal (such as a mobile phone or a computer) and receive a single-ended audio signal sent by the second terminal.

[0137] It is understood that the audio signal received by the audio amplifier circuit 10 may include at least one of a differential audio signal and a single-ended audio signal. That is, the audio amplifier circuit 10 may only receive one type of audio signal transmitted by one signal transmission circuit at a time. Alternatively, the audio amplifier circuit 10 may simultaneously receive a differential audio signal transmitted by the first signal transmission circuit 20 and a single-ended audio signal transmitted by the second signal transmission circuit 30. In scenarios where both differential and single-ended audio signals are received simultaneously, the audio amplifier circuit 10 may process both types of audio signals simultaneously. Accordingly, the speaker 40 may simultaneously play both types of processed audio signals.

[0138] Figure 7 This is a structural diagram of another audio playback device provided in an embodiment of the present application. Figure 7 As shown, the audio playback device may further include: a main control chip 50 and at least one microphone interface circuit 60. The microphone interface circuit 60 is used to connect to a microphone to collect audio signals. The main control chip 50 is respectively connected to the at least one microphone interface circuit 60, the first signal transmission circuit 20, and the second signal transmission circuit 30. The main control chip 50 is used to transmit the audio signal collected by the at least one microphone interface circuit 60 to the first signal transmission circuit 20 and / or the second signal transmission circuit 30. That is, the main control chip 50 can transmit the audio signal collected by the at least one microphone interface circuit 60 to the terminal through the first signal transmission circuit 20 and / or the second signal transmission circuit 30 for the terminal to play.

[0139] In an embodiment of the present application, the main control chip 50 can be an embedded system-on-chip (SoC). The audio playback device may further include: a pseudo-differential circuit, a DC elimination circuit, and an analog-to-digital converter (ADC) connected to each microphone interface circuit 60. The pseudo-differential circuit is used to filter the audio signal collected by the microphone interface circuit 60, thereby filtering out noise signals in the audio signal. The DC elimination circuit is used to filter out the DC component in the audio signal output by the pseudo-differential circuit. The ADC is used to convert the audio signal output by the DC elimination circuit into a digital signal and transmit the digital signal to the main control chip 50.

[0140] In the embodiments of this application, Figure 7As shown, the audio playback device may include multiple microphone interface circuits 60 , for example, may include three microphone interface circuits 60 .

[0141] Optionally, continue to refer to Figure 7 The audio playback device may further include an audio recollection circuit 70. The audio recollection circuit 70 is connected to the output terminal OUT of the audio amplifier circuit 10 and the main control chip 50, respectively. The audio recollection circuit 70 is used to sample the audio signal output by the audio amplifier circuit 10 to obtain a sampled signal. The main control chip 50 is also used to perform echo cancellation processing on the audio signal collected by the at least one microphone interface circuit 60 based on the sampled signal. Afterwards, the main control chip 50 can transmit the audio signal after the echo cancellation processing to the terminal through the first signal transmission circuit 20 and / or the second signal transmission circuit 30.

[0142] Since the main control chip 50 can perform echo cancellation processing on the audio signal collected by the at least one microphone interface circuit 60, it can ensure that the echo when the terminal plays the audio signal is small and the playing effect of the audio signal is better.

[0143] Optionally, continue to refer to Figure 7 The audio playback device may further include at least one button 21 connected to the first signal transmission circuit 20, at least one indicator light 22, an antenna 23, and a debugging circuit 24. The at least one button 21 may be connected to the first signal transmission circuit 20 via a general-purpose input / output (GPIO) interface. The indicator light 22 may be connected to the first signal transmission circuit 20 via an inter-integrated circuit (I2C) bus, and the indicator light 22 may indicate the working status of the first signal transmission circuit 20. The antenna 23 may be used to receive audio signals sent by a terminal, for example, the antenna 23 may be a Bluetooth antenna. The debugging circuit 24 may be connected to the first signal transmission circuit 20 via a universal asynchronous receiver / transmitter (UART) bus. The first signal transmission circuit 20 may also be connected to the main control chip 50 via the UART bus, and the first signal transmission circuit 20 may transmit the working status information of the first signal transmission circuit 20 to the main control chip 50 via the UART bus.

[0144] It is understandable that the at least one button 21 and the at least one indicator light 22 may also be directly connected to the main control chip 50 .

[0145] Optionally, continue to refer to Figure 7The audio playback device may further include a flash memory 80 and a debug circuit 90 connected to the main control chip 50. The flash memory 80 may be connected to the main control chip 50 via a serial peripheral interface (SPI). The debug circuit 90 may be connected to the main control chip 50 via a UART bus.

[0146] In summary, an embodiment of the present application provides an audio playback device, wherein the audio amplification circuit in the audio playback device includes two audio processing circuits and a power amplifier. The first audio processing circuit is capable of filtering differential audio signals, the second audio processing circuit is capable of limiting and filtering single-ended audio signals, and the power amplifier is capable of amplifying the audio signals output by the two audio processing circuits. Based on the processing operations of the two audio processing circuits, it can be ensured that the signal quality of the differential audio signal and the single-ended audio signal transmitted to the power amplifier is good and the amplitudes are relatively close. Thus, a single power amplifier can be used to reliably amplify the power of two different types of audio signals, effectively simplifying the structure of the audio playback device and reducing the cost of the audio playback device.

[0147] Furthermore, when the power amplifier simultaneously amplifies two different types of audio signals, the interference between the two different types of audio signals is low, thereby ensuring that the signal quality of the audio signal output by the power amplifier is high, and further ensuring that the audio signal played by the speaker has a better effect.

[0148] It should be understood that the term "and / or" mentioned herein indicates that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the term "at least one" in this application means one or more, and the term "plurality" in this application means two or more.

[0149] In this application, the terms "first", "second", etc. are used to distinguish identical or similar items with substantially the same effects and functions. It should be understood that there is no logical or temporal dependency between "first", "second", and "nth", nor is there any limitation on the quantity and execution order.

[0150] The above description is merely an exemplary embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An audio amplifier circuit (10), characterized in that: The audio amplification circuit (10) comprises: a first audio processing circuit (110), a second audio processing circuit (120) and a power amplifier (130); The first audio processing circuit (110) has a differential input terminal and a differential output terminal, the differential output terminal is directly connected to the positive input terminal and the negative input terminal of the power amplifier (130), and the first audio processing circuit (110) is used to filter the differential audio signal received through the differential input terminal and transmit the filtered differential audio signal to the power amplifier (130); The second audio processing circuit (120) has a single-ended input terminal (I21) and a single-ended output terminal (O21), the single-ended output terminal (O21) being directly connected to the positive input terminal of the power amplifier (130), and the second audio processing circuit (120) is used to limit and filter the single-ended audio signal received through the single-ended input terminal (I21), and transmit the limited and filtered single-ended audio signal to the power amplifier (130), wherein limiting refers to reducing the amplitude of the single-ended audio signal; The power amplifier (130) is used to perform power amplification on the received audio signal, and the power amplifier (130) has the same amplification effect on different types of received audio signals.

2. The audio amplifier circuit (10) according to claim 1, characterized in that The first audio processing circuit (110) comprises: a first filtering circuit (1101) and a second filtering circuit (1102); The first filter circuit (1101) is connected to the differential input terminal and the second filter circuit (1102) respectively, and the first filter circuit (1101) is used to perform a first-stage filtering on the differential audio signal; The second filtering circuit (1102) is also connected to the differential output terminal, and the second filtering circuit (1102) is used to perform a second-stage filtering on the differential audio signal after the first-stage filtering.

3. The audio amplifier circuit (10) according to claim 2, characterized in that: The differential input terminal includes a first input terminal (I11) and a second input terminal (I12); The first filter circuit (1101) comprises: a first capacitor (C1), a first resistor (R1), a second capacitor (C2) and a second resistor (R2); wherein the first capacitor (C1) and the first resistor (R1) are connected in series between the first input terminal (I11) and the first input end of the second filter circuit (1102); The second capacitor (C2) and the second resistor (R2) are connected in series between the second input terminal (I12) and the second input end of the second filter circuit (1102).

4. The audio amplifier circuit (10) according to claim 2, characterized in that The differential output end includes a first output terminal (O11) and a second output terminal (O12); the second filter circuit (1102) includes: a third capacitor (C3), a third resistor (R3), a fourth capacitor (C4) and a fourth resistor (R4); wherein the third capacitor (C3) and the third resistor (R3) are connected in series between the first output end of the first filter circuit (1101) and the first output terminal (O11); The fourth capacitor (C4) and the fourth resistor (R4) are connected in series between the second output end of the first filter circuit (1101) and the second output terminal (O12).

5. The audio amplifier circuit (10) according to claim 4, characterized in that: The first audio processing circuit (110) further includes a third filtering circuit (1103), the third filtering circuit (1103) including: at least one of a fifth capacitor (C5), a sixth capacitor (C6), a fifth resistor (R5), a sixth resistor (R6), and a seventh resistor (R7); wherein one end of the fifth capacitor (C5) is connected to the first output end of the first filter circuit (1101), and the other end of the fifth capacitor (C5) is connected to the second output end of the first filter circuit (1101); The sixth capacitor (C6) and the fifth resistor (R5) are connected in series between the first output terminal and the second output terminal of the first filter circuit (1101); One end of the sixth resistor (R6) is connected to the second output end of the first filter circuit (1101), and the other end of the sixth resistor (R6) is connected to a target node, which is a connection node between the fourth capacitor (C4) and the fourth resistor (R4); One end of the seventh resistor (R7) is connected to the first output end of the first filter circuit (1101), and the other end of the seventh resistor (R7) is connected to the ground end.

6. The audio amplifier circuit (10) according to claim 2, characterized in that: The first audio processing circuit (110) further includes: a common mode inductor (L0); The common-mode inductor (L0) is connected in series between the first filter circuit (1101) and the second filter circuit (1102).

7. The audio amplifier circuit (10) according to any one of claims 1 to 6, characterized in that: The second audio circuit (120) comprises: a fourth filter circuit (1201) and a limiting filter circuit (1202); The fourth filter circuit (1201) is connected to the single-ended input terminal (I21) and the amplitude limiting filter circuit (1202) respectively, and the fourth filter circuit (1201) is used to perform low-pass filtering on the single-ended audio signal; The limiting filter circuit (1202) is also connected to the single-ended output terminal (O21), and the limiting filter circuit (1202) is used to limit the single-ended audio signal after low-pass filtering, and to perform high-pass filtering on the single-ended audio signal after limiting.

8. The audio amplifier circuit (10) according to claim 7, characterized in that: The fourth filter circuit (1201) comprises: a filter inductor (L1) and a seventh capacitor (C7); One end of the filter inductor (L1) is connected to the single-ended input end (I21), and the other end of the filter inductor (L1) is connected to the amplitude limiting filter circuit (1202); One end of the seventh capacitor (C7) is connected to the amplitude limiting filter circuit (1202), and the other end of the seventh capacitor (C7) is connected to the ground.

9. The audio amplifier circuit (10) according to claim 8, characterized in that: The fourth filtering circuit (1201) further includes: an eighth capacitor (C8); The eighth capacitor (C8) and the filter inductor (L1) are connected in series between the single-ended input terminal (I21) and the amplitude limiting filter circuit (1202).

10. The audio amplifier circuit (10) according to claim 7, characterized in that: The amplitude limiting filter circuit (1202) comprises: an eighth resistor (R8), a ninth resistor (R9) and a ninth capacitor (C9); wherein one end of the eighth resistor (R8) is connected to the fourth filter circuit (1201), and the other end of the eighth resistor (R8) is connected to the ground; The ninth resistor (R9) and the ninth capacitor (C9) are connected in series between the fourth filter circuit (1201) and the single-ended output terminal (O21).

11. An audio playback device, characterized in that: The audio playback device comprises: an audio amplifier circuit (10) according to any one of claims 1 to 10, a first signal transmission circuit (20), a second signal transmission circuit (30) and a speaker (40); The differential input terminal (IN1) of the audio amplifier circuit (10) is connected to the first signal transmission circuit (20), the single-ended input terminal (IN2) of the audio amplifier circuit (10) is connected to the second signal transmission circuit (30), and the output terminal (OUT) of the audio amplifier circuit (10) is connected to the speaker (40); The first signal transmission circuit (20) is used to transmit a differential audio signal to the audio amplifier circuit (10), the second signal transmission circuit (30) is used to transmit a single-ended audio signal to the audio amplifier circuit (10), and the speaker (40) is used to play the audio signal output by the audio amplifier circuit (10).

12. The audio playback device according to claim 11, characterized in that The audio playback device further comprises: a main control chip (50) and at least one microphone interface circuit (60); The main control chip (50) is respectively connected to the at least one microphone interface circuit (60), the first signal transmission circuit (20), and the second signal transmission circuit (30); the main control chip (50) is used to transmit the audio signal collected by the at least one microphone interface circuit (60) to the first signal transmission circuit (20) and / or the second signal transmission circuit (30).

13. The audio playback device according to claim 12, characterized in that: The audio playback device further includes: an audio retrieving circuit (70); The audio sampling circuit (70) is connected to the output end (OUT) of the audio amplifier circuit (10), and the audio sampling circuit (70) is used to sample the audio signal output by the audio amplifier circuit (10) to obtain a sampled signal; The main control chip (50) is also connected to the audio echo circuit (70), and the main control chip (50) is also used to perform echo cancellation processing on the audio signal collected by the at least one microphone interface circuit (60) based on the sampling signal.

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