A method for suppressing startup pop noise of an audio power amplifier based on sound masking effect

Abstract

The application discloses a kind of audio power amplifier booting pop noise suppression methods based on sound masking effect, belong to power amplifier technical field, this method includes: step S1: preset voltage reference reference value for audio detection;Step S2: according to the comparison of input voltage value and voltage reference reference value, corresponding output suppression signal or working signal;Step S3: generate PWM signal, through and buffer connection to switch module;Step S4: when generating suppression signal, it is judged that audio input signal exists pop noise at this time, and power amplifier output end does not generate impact signal;When generating working signal, power amplifier output end generates impact signal containing suppression effect.The present application generates composite sound by input signal threshold detection, which is superimposed with preset switch music signal, has the advantages of solving the response lag bottleneck when D-class power amplifier pop noise suppression and promoting D-class power amplifier to miniaturization.

Description

Technical Field

[0001] This invention relates to the field of power amplifier technology, specifically to a method for suppressing popping noises when powering on an audio power amplifier based on the sound masking effect. Background Technology

[0002] In current audio power amplifiers (i.e., amplifiers), especially Class D amplifiers, the popping sound caused by the surge signal generated upon power-on is a common problem. Class D amplifiers operate based on high-frequency switching, typically using pulse-width modulation (PWM), controlling power transmission through rapid switching at the output stage. During power-on, the amplifier undergoes a transition from off to normal operation, inevitably generating a surge signal. This surge signal is emitted through the speakers, resulting in an unpleasant popping sound and negatively impacting the user experience. When the amplifier first starts up, the output signal fluctuates significantly, and the voltage is high. For professional Class D amplifiers, especially high-power versions, the operating voltage can reach several hundred volts, far exceeding the 5V operating voltage of ordinary chips. The amplifier output is connected to high-sensitivity, high-power speakers, typically with a sensitivity exceeding 100dB. Therefore, even small signal fluctuations can be amplified and produce an audible popping sound through the speakers. In existing methods for suppressing popping noises during the power-on of Class D amplifiers, a common approach is to install a relay at the amplifier output to disconnect the amplifier from the speaker upon power-on, and then reconnect it once the amplifier has stabilized. Because relays need to handle high currents, they are bulky and expensive, especially in high-power Class D amplifiers where the current handling capacity of the relays is crucial, further increasing the complexity and cost of the entire system. Summary of the Invention

[0003] This invention provides a method for suppressing pop noise during the startup of an audio power amplifier based on the sound masking effect, which solves the problems of poor pop noise suppression effect and lack of control over size and cost in existing technologies for suppressing pop noise during the startup of Class D audio power amplifiers.

[0004] This invention is achieved through the following technical solution:

[0005] A method for suppressing popping noises during the power-on of an audio power amplifier based on the sound masking effect, the method comprising:

[0006] Step S1: Measure the audio input signal for audio power amplification of the target power amplifier device, preset the voltage reference value for audio detection, set the audio detection circuit and PWM modulator, and input the audio input signal into the audio detection circuit;

[0007] Step S2: whenWhen the input voltage of the audio input signal is lower than the voltage reference value, the audio detection circuit generates a low-level suppression signal; when the input voltage is higher than the voltage reference value, the audio detection circuit generates a high-level working signal.

[0008] Step S3: Input the audio input signal into the PWM modulator to generate a PWM signal containing the modulated music signal. Connect both the PWM signal and the suppression signal to the input of the AND gate. Connect the output of the AND gate to the switching module through a buffer.

[0009] Step S4: When the audio detection circuit generates a suppression signal, the switching module is turned off, and no impulse signal is generated at the power amplifier output. When the audio detection circuit generates a working signal, the switching module is turned on and transmits the PWM signal to the power amplifier output. The power amplifier output generates an amplified music signal and a power-on impulse signal.

[0010] The connection between the power amplifier and the speaker is disconnected upon power-on and reconnected only after the amplifier has stabilized. Because relays need to handle high current, they are bulky and expensive, especially in high-power Class D amplifiers where the current handling capacity of the relays is crucial, increasing the complexity and cost of the entire system. Furthermore, while using a relay to disconnect the output, it doesn't eliminate internal noise sources. When the relay closes, residual voltage spikes or unstable biases may occur in the circuit, such as level jumps, irregular PWM waveforms, and high-frequency parasitic oscillations. These abnormal signals accumulate at the output, forming a wideband surge voltage. Once the relay closes, the speaker amplifies these signals, causing popping noises. Therefore, traditional delayed relay closure methods often fail to effectively avoid the popping noise problem during the power-on of Class D amplifiers. Based on this, this invention provides a method for suppressing popping noises during the power-on of audio amplifiers based on the sound masking effect, solving the problems of poor popping noise suppression and lack of control over size and cost in existing technologies for suppressing popping noises during the power-on of Class D audio amplifiers.

[0011] Furthermore, the audio detection circuit includes a T-type feedback network, an amplitude acquisition circuit, and a comparison output circuit connected in sequence, wherein the input terminal of the T-type feedback network is set as the input terminal of the audio detection circuit, and the output terminal of the comparison output circuit is set as the output terminal of the audio detection circuit.

[0012] The T-type feedback network performs high-frequency noise cancellation and impedance matching on the audio input signal, and increases the signal amplitude to a processable range; the amplitude acquisition circuit flips the negative half-cycle signal to positive polarity to convert the bidirectional parameter value of the audio input signal into a unipolar parameter amplitude; the comparison output circuit compares the amplitude signal with a preset threshold and generates a corresponding level control signal to the AND gate input.

[0013] Furthermore, the structure of the T-type feedback network includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first amplifier U1; one end of the first resistor R1 is designated as the first input terminal P1, and the other end of the first resistor R1 is connected to the same point as the inverting input terminal of the first amplifier U1 and one end of the third resistor R3; one end of the second resistor R2 is connected to the non-inverting input terminal of the first amplifier U1, and the other end of the second resistor R2 is grounded; the other end of the third resistor R3 is connected to the same point as one end of the fifth resistor R5 and one end of the fourth resistor R4, and the other end of the fourth resistor R4 is grounded; the other end of the fifth resistor R5 is connected to the same point as the output terminal of the first amplifier U1 and designated as terminal E1; terminal E1 is designated as the output terminal of the T-type feedback network.

[0014] Further, the amplitude acquisition circuit includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second amplifier U2, a first diode D1, and a second diode D2. One end of the sixth resistor R6 and one end of the seventh resistor R7 are connected to the same point and designated as endpoint E2, which is the input terminal of the amplitude acquisition circuit. The other end of the sixth resistor R6 is connected to the cathode of the first diode D2, one end of the eighth resistor R8, and the inverting input terminal of the second amplifier U2 at the same point. The anode of the first diode D1 is connected to the output terminal of the second amplifier U2 and the cathode of the second diode D2 at the same point. The non-inverting input terminal of the second amplifier U2 is connected in series with the ninth resistor R9 and the ground terminal. The other end of the eighth resistor R8 is connected to the anode of the second diode D2 and one end of the tenth resistor R10 at the same point, and the other end of the tenth resistor R10 is connected to the other end of the seventh resistor R7 at the same point and designated as endpoint E3. The amplitude acquisition circuit is connected to the comparison output circuit through endpoint E3.

[0015] Further, the comparison output circuit includes a first comparator Y1, a first voltage source VCC1, a second voltage source VCC2, an eleventh resistor R11, a twelfth resistor R12, and a first capacitor C1; the non-inverting input terminal of the first comparator Y1 and one end of the eleventh resistor R11 are connected to terminal E3; the positive power supply terminal of the first comparator Y1 is connected to the same point as the first voltage source VCC1 and one end of the first capacitor C1, and the other end of the first capacitor C1 is grounded; the inverting input terminal of the first comparator Y1 is connected in series with the twelfth resistor R12 and the second voltage source VCC2; the other end of the eleventh resistor R11 is connected to the same point as the output terminal of the first comparator Y1 and is set as terminal E4, and terminal E4 is set as the first output terminal Q1 representing the output terminal of the audio detection circuit.

[0016] Furthermore, the PWM modulator includes an operational amplifier inverting adder circuit and a PWM modulation circuit, wherein the input terminal of the operational amplifier inverting adder circuit is set as the input terminal of the PWM modulator, and the output terminal of the PWM modulation circuit is set as the output terminal of the PWM modulator.

[0017] The operational amplifier inverting adder circuit mixes and modulates the audio input signal with the preset switch music signal to generate a baseband signal; the PWM modulation circuit converts the synthesized baseband signal into a PWM waveform, uses the phase amplitude characteristics of the preset switch music signal to suppress popping components, sets the modulated baseband signal as the output signal of the PWM modulator, and completes the output.

[0018] Furthermore, the operational amplifier inverting adder circuit includes a memory MEM, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a seventeenth resistor R17, and a third amplifier U3; one end of the thirteenth resistor R13 is set as the second input terminal P2; one end of the fourteenth resistor R14 is provided with a fourth voltage source VCC4, and the other end is connected to one end of the memory MEM; the other end of the thirteenth resistor R13, the other end of the memory MEM, one end of the fifteenth resistor R15, and the inverting input terminal of the third amplifier U3 are connected to the same point and set as terminal E5; the non-inverting output terminal of the third amplifier U3 is connected in series with the seventeenth resistor R17 and the ground terminal in sequence; terminal E5 is set as the output terminal of the operational amplifier inverting adder circuit.

[0019] Further, the PWM modulation circuit includes a sixteenth resistor R16, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a second capacitor C2, a third capacitor C3, and a fourth amplifier U4. One end of the sixteenth resistor R16 is set as the input terminal of the PWM modulation circuit, and the other end of the sixteenth resistor R16 is connected to the same point as one end of the second capacitor C2 and one end of the eighteenth resistor R18. The other end of the eighteenth resistor R18 is connected to the same point as the non-inverting input terminal of the fourth amplifier U4 and one end of the third capacitor C3, and the other end of the third capacitor C3 is connected to the same point as one end of the nineteenth resistor R19 and the ground terminal. The other end of the nineteenth resistor R19 is connected to the same point as the inverting input terminal of the fourth amplifier U4 and one end of the twentieth resistor R20. The other end of the twentieth resistor R20 is connected to the same point as the other end of the second capacitor C2 and the output terminal of the fourth amplifier U4 and is set as terminal E6. Terminal E4 is set as the second output terminal Q2, representing the output terminal of the PWM modulation circuit.

[0020] Furthermore, the PWM modulation circuit also includes a third voltage source VCC3, a fourth capacitor C4, and a fifth capacitor C5. One end of the fourth capacitor C4 is connected to one end of the fifth capacitor C5, the positive power supply terminal of the fourth amplifier U4, and the third voltage source VCC3 at the same point; the other end of the fourth capacitor C4 is connected to the other end of the fifth capacitor C5 and the ground terminal at the same point.

[0021] Furthermore, the output noise density of the third voltage source VCC3 is less than 10μV, and the output current is greater than or equal to 100mA.

[0022] Compared with existing technologies, this invention addresses the issue of transient impact signals during power-on by detecting a threshold of the input signal. It first blocks the internal transient energy output until the input signal exceeds the threshold, at which point the amplifier outputs a normal signal to the speaker. This allows the listener to hear a composite sound generated by the superposition of the pop and the music signal. Furthermore, the use of integrated circuits instead of relays significantly reduces the size of the amplifier. This invention has the advantage of solving the response lag bottleneck in suppressing pops in Class D amplifiers and promotes the miniaturization of Class D amplifiers. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0024] Figure 1 This is a flowchart of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the circuit structure of the audio detection circuit of the present invention;

[0027] Figure 4 This is a schematic diagram of the circuit structure of the PWM modulator of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0029] Example 1

[0030] like Figures 1-2 As shown, this embodiment is a method for suppressing popping noises during the power-on of an audio power amplifier based on the sound masking effect. The method includes:

[0031] Step S1: Measure the audio input signal for audio power amplification of the target power amplifier device, preset the voltage reference value for audio detection, set the audio detection circuit and PWM modulator, and input the audio input signal into the audio detection circuit;

[0032] Step S2: when When the input voltage of the audio input signal is lower than the voltage reference value, the audio detection circuit generates a low-level suppression signal; when the input voltage is higher than the voltage reference value, the audio detection circuit generates a high-level working signal.

[0033] Step S3: Input the audio input signal into the PWM modulator to generate a PWM signal containing the modulated music signal. Connect both the PWM signal and the suppression signal to the input of the AND gate. Connect the output of the AND gate to the switching module through a buffer.

[0034] Step S4: When the audio detection circuit generates a suppression signal, the switching module is turned off, and no impulse signal is generated at the power amplifier output. When the audio detection circuit generates a working signal, the switching module is turned on and transmits the PWM signal to the power amplifier output. The power amplifier output generates an amplified music signal and a power-on impulse signal.

[0035] The acquired input signal refers to the audio signal being acquired or being obtained from the input terminal of the target power amplifier device, i.e., the interface before the audio signal enters the power amplifier. This is usually an analog audio signal, serving as the amplification source for the power amplifier. The measurement process involves not only simple acquisition but also the measurement and analysis of parameters such as the voltage magnitude, waveform characteristics, and frequency components of the audio input signal to determine its validity and status. The audio input signal is the original signal upon which the power amplifier relies for normal operation and is the foundational data for subsequent detection, modulation, and pop suppression. The voltage reference value refers to a pre-set voltage value used as the standard for the audio detection circuit to judge the input signal. The audio detection circuit compares the voltage amplitude of the input audio signal with the preset reference voltage and outputs two different logic level signals to control the opening and closing of subsequent circuits. The music signal is a pre-placed preset switch music signal. Generating a PWM signal containing modulated music signals means that an analog audio signal is input to a PWM modulator. After pulse width modulation processing, the modulator outputs a PWM signal whose pulse width changes according to the intensity of the audio signal. Its pulse width or duty cycle changes with the voltage amplitude of the original music signal. This PWM signal can be used to drive the power amplifier output stage, thereby generating an audio PWM signal with a sonic boom suppression effect. The audio input signal is typically an analog signal whose voltage changes over time, representing the original sound waveform. The PWM modulator modulates the analog audio signal into a PWM signal: mapping a continuous analog voltage to a series of pulse waveforms with different duty cycles at a fixed frequency. When the audio detection circuit detects that the input audio signal voltage is lower than a preset reference value, it considers the signal to be likely invalid, an abnormal starting impulse signal, or a popping sound. The system control switch module is disconnected, cutting off the signal path, and the power amplifier will not output a PWM signal containing impulse components, thus preventing the speaker from emitting a popping sound. When the detection circuit detects that the input signal is normal, i.e., the input voltage value is higher than the voltage reference value, the switch module is turned on, allowing the PWM modulated signal to be transmitted to the power amplifier output. The impact signal indicates that the PWM signal after normal modulation may still contain some transient fluctuations, but since abnormal popping sounds have been suppressed, the output signal is mainly a normal music signal after modulation.

[0036] In this embodiment, a specific implementation process is defined as follows: The voltage reference value is set to -50dBV. When the power amplifier is powered on, if the detected audio input signal is below -50dBV, the detection circuit outputs a low-level signal, which is ANDed with the PWM signal output by the PWM modulator. This results in a low-level input signal for subsequent circuits, keeping the switching transistors of the switching module in the off state. No surge signal appears at the power amplifier output, thus preventing popping sounds at the speaker. When the input audio signal amplitude is above -50dBV, the detection circuit outputs a high-level signal, which is ANDed with the PWM signal output by the PWM modulator. This makes the input of subsequent circuits a PWM signal, causing the switching transistors of the switching module to enter the switching state. A surge signal appears at the power amplifier output, resulting in a popping sound at the speaker. At this time, since the PWM signal output by the PWM modulator is modulated by the music signal, the sound emitted by the speaker is a superposition of the music signal and the popping sound. Because the music signal is much stronger than the popping sound, the human ear only hears the music sound and not the popping sound. This achieves suppression of the power-on popping sound. As a feasible implementation, the transmission process where the output of the audio detection circuit and the output of the PWM modulator are both connected to the input of an AND gate, and the output of the AND gate is connected to the switching module via a buffer, is represented as an audio transmission line. The number of audio transmission lines between the audio input signal and the switching module is set to two. The switching module is defined as a half-bridge switching circuit, and an LC demodulator is added between the switching module and the speaker at the power amplifier output. The half-bridge switching circuit structure supports soft-start control, which can gradually increase the PWM duty cycle to achieve a gradual rise in the audio signal. Simultaneously, it can avoid the popping sound phenomenon when the audio carrier is suddenly switched on, and is more easily integrated with the spectrum of the music signal, achieving effective popping sound masking using the masking effect. The LC demodulator is used to recover the audio signal from the high-frequency PWM pulse signal through low-pass filtering.

[0037] Example 2

[0038] In this embodiment, as Figure 3 As shown, the audio detection circuit includes a T-type feedback network, an amplitude acquisition circuit, and a comparison output circuit connected in sequence. The input terminal of the T-type feedback network is set as the input terminal of the audio detection circuit, and the output terminal of the comparison output circuit is set as the output terminal of the audio detection circuit.

[0039] The T-type feedback network performs high-frequency noise cancellation and impedance matching on the audio input signal, and increases the signal amplitude to a processable range; the amplitude acquisition circuit flips the negative half-cycle signal to positive polarity to convert the bidirectional parameter value of the audio input signal into a unipolar parameter amplitude; the comparison output circuit compares the amplitude signal with a preset threshold and generates a corresponding level control signal to the AND gate input.

[0040] The T-type feedback network includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first amplifier U1. One end of the first resistor R1 is designated as the first input terminal P1, and the other end of the first resistor R1 is connected to the inverting input terminal of the first amplifier U1 and one end of the third resistor R3 at the same point. One end of the second resistor R2 is connected to the non-inverting input terminal of the first amplifier U1, and the other end of the second resistor R2 is grounded. The other end of the third resistor R3 is connected to one end of the fifth resistor R5 and one end of the fourth resistor R4 at the same point, and the other end of the fourth resistor R4 is grounded. The other end of the fifth resistor R5 is connected to the output terminal of the first amplifier U1 at the same point and designated as terminal E1. Terminal E1 is designated as the output terminal of the T-type feedback network.

[0041] The first input terminal P1 represents the input terminal for the audio input signal. The T-type feedback network transforms the op-amp output impedance into an equivalent impedance suitable for the input terminal, optimizing signal transmission and reducing reflections and parasitic oscillations. The first resistor R1 participates in forming the equivalent feedback impedance, used to determine the closed-loop gain of the first amplifier U1, which can precisely control the amplitude amplification of the input signal to avoid distortion or overload; it also acts as an input current limiter, protecting the op-amp input stage from damage when the input voltage is instantaneously high. The second resistor R2 is used to provide a stable reference voltage, usually a bias voltage, to ensure that the op-amp operates in the correct linear region. Adding the second resistor R2 to the non-inverting input terminal, making its impedance match that of the first resistor R1, can reduce the input offset voltage caused by bias current. The third resistor R3, the fourth resistor R4, and the fifth resistor R5 are connected in series in a voltage divider and current shunt branch, forming the upper part of the entire feedback path. Its limited resistance value has a buffering effect on transient voltage changes, reducing the direct impact on the input terminal. The fourth resistor R4 provides a discharge path to ground, avoiding output drift caused by accumulated DC bias. The fifth resistor R5 is used to determine the magnitude of the operational amplifier output feedback current entering the inverting input. The third resistor R3 provides the main feedback path, the fourth resistor R4 provides the discharge path, and the fifth resistor R5 is connected to the output terminal to establish closed-loop feedback. The first amplifier U1 amplifies the signal and outputs it, while simultaneously feeding back part of the output signal to the inverting input terminal through the T-shaped feedback network composed of the third resistor R3, the fourth resistor R4, and the fifth resistor R5. Utilizing the principle of negative feedback, the operational amplifier automatically adjusts its output, making the input difference close to 0, thereby stabilizing the output voltage. The first amplifier U1 implements an active filtering function, filtering out high-frequency glitches, PWM parasitic components, and other impact noise. Preferably, as a feasible implementation, based on the structure of the fourth resistor R4 and the fifth resistor R5 connected in parallel and then in series with the third resistor R3, the feedback impedance is expressed as Z, and the formula for calculating the feedback impedance Z is: Let the closed-loop gain of the first amplifier U1 be denoted as A, then the formula for calculating the closed-loop gain A is as follows: .

[0042] Further, the amplitude acquisition circuit includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second amplifier U2, a first diode D1, and a second diode D2. One end of the sixth resistor R6 and one end of the seventh resistor R7 are connected to the same point and designated as endpoint E2, which is the input terminal of the amplitude acquisition circuit. The other end of the sixth resistor R6 is connected to the cathode of the first diode D2, one end of the eighth resistor R8, and the inverting input terminal of the second amplifier U2 at the same point. The anode of the first diode D1 is connected to the output terminal of the second amplifier U2 and the cathode of the second diode D2 at the same point. The non-inverting input terminal of the second amplifier U2 is connected in series with the ninth resistor R9 and the ground terminal. The other end of the eighth resistor R8 is connected to the anode of the second diode D2 and one end of the tenth resistor R10 at the same point, and the other end of the tenth resistor R10 is connected to the other end of the seventh resistor R7 at the same point and designated as endpoint E3. The amplitude acquisition circuit is connected to the comparison output circuit through endpoint E3.

[0043] The amplitude acquisition circuit is used to perform absolute value processing on the input signal, eliminating the influence of parameters on the circuit flow direction. When the input signal is positive, the output voltage of the amplitude acquisition circuit follows the input voltage change; when the input signal is negative, the amplitude acquisition circuit converts the input voltage into a positive value for output. Due to the virtual short characteristic of the operational amplifier, the inverting input terminal of the second amplifier U2 is at zero potential. The sixth resistor R6 is used to limit the input current and protect the subsequent circuit components. The sixth resistor R6 and the eighth resistor R8 together form part of the signal path, ensuring that the signal can enter the amplification and rectification stage. As a feasible implementation, when the sixth resistor R6 and the eighth resistor R8 are equal, the output voltage calculation formula of the amplitude acquisition circuit is: V IN Indicates the input voltage value, V O This represents the output voltage. The seventh resistor R7 forms a signal shunt, allowing part of the input signal to flow directly to endpoint E3 through R7. The eighth resistor R8 provides appropriate input impedance to the non-inverting input of the second amplifier U2, limiting the input signal current and protecting the op-amp input. The ninth resistor R9 ensures the virtual short principle of the op-amp holds, keeping the inverting input close to 0V, ensuring the accuracy of precision amplification and rectification within the linear operating region. The tenth resistor R10, together with the seventh resistor R7, forms a voltage divider, used to proportionally scale the rectified voltage signal, and the divided output is sent to the comparator output circuit.

[0044] The first diode D1 and the second diode D2 act as switching devices to achieve half-wave rectification and inversion of the signal. The second amplifier U2, in conjunction with the diodes, converts the positive and negative half-cycles of the input signal into a fully positive voltage output. During the positive half-cycle input signal, the input signal is positive and enters the inverting input terminal of the second amplifier U2 through the sixth resistor R6. At this time, the op-amp output voltage is negative, driving the first diode D1 to conduct and the second diode D2 to cut off. Current flows through the first diode D1 and feeds back to the input terminal, creating negative feedback in the op-amp. The output voltage linearly follows the amplitude of the positive half-cycle of the input voltage, and terminal E3 receives a positive voltage proportional to the amplitude of the positive half-cycle. During the negative half-cycle input signal, the input signal is negative, and the current flows to the inverting terminal of U2, changing its polarity. At this time, the op-amp output voltage is positive, driving the second diode D2 to conduct and the first diode D1 to cut off. The negative half-cycle signal is inverted into a positive signal output through the second diode D2, and terminal E3 also outputs a corresponding positive voltage amplitude, ensuring that the negative half-cycle is also converted into a unipolar positive voltage. The second amplifier U2, in conjunction with the first diode D1 and the second diode D2, achieves full-wave rectification and linear amplification of the positive and negative half-cycles of the input AC signal, and outputs a DC voltage representing the amplitude of the input signal, which greatly improves the accuracy and stability of audio signal amplitude detection.

[0045] Further, the comparison output circuit includes a first comparator Y1, a first voltage source VCC1, a second voltage source VCC2, an eleventh resistor R11, a twelfth resistor R12, and a first capacitor C1; the non-inverting input terminal of the first comparator Y1 and one end of the eleventh resistor R11 are connected to terminal E3; the positive power supply terminal of the first comparator Y1 is connected to the same point as the first voltage source VCC1 and one end of the first capacitor C1, and the other end of the first capacitor C1 is grounded; the inverting input terminal of the first comparator Y1 is connected in series with the twelfth resistor R12 and the second voltage source VCC2; the other end of the eleventh resistor R11 is connected to the same point as the output terminal of the first comparator Y1 and is set as terminal E4, and terminal E4 is set as the first output terminal Q1 representing the output terminal of the audio detection circuit.

[0046] The first output terminal Q1 is the output terminal of the audio detection circuit. The first comparator Y1 is used to compare the amplitude signal representing the current audio input signal output by the amplitude acquisition circuit with a preset threshold voltage. The non-inverting input terminal is connected to the amplitude signal from terminal E3, i.e., the detected audio amplitude signal; the inverting input terminal is connected to the preset threshold voltage, which is provided by the second voltage source VCC2 through the current-limiting resistor R12. When the amplitude signal is greater than the preset threshold, the comparator outputs a high-level working signal, the voltage value of which is close to that of the first voltage source VCC1; when the amplitude signal is less than the preset threshold, the comparator outputs a low-level suppression signal, the voltage value of which is close to that of ground. The first voltage source VCC1 provides positive power to the comparator Y1, enabling it to work normally and output a level signal. The second voltage source VCC2 is used to provide a preset reference threshold voltage for comparison with the amplitude signal. The eleventh resistor R11 is connected between the non-inverting input terminal and the output terminal of the first comparator Y1, forming an input impedance together with the output terminal of the amplitude acquisition circuit to ensure the signal stability at the comparator input terminal. The twelfth resistor R12 and VCC2 together form a voltage divider circuit, outputting a stable reference voltage as the threshold of the first comparator Y1. By adjusting the value of the twelfth resistor R12, the sensitivity of the comparator in determining whether the audio signal exceeds the threshold can be flexibly adjusted. The first capacitor C1 is used to store the electrical energy of the first voltage source VCC and release charge, playing a stabilizing role in the voltage at the power supply terminal of the first comparator Y1, and avoiding abnormal jumps in the comparator output caused by fluctuations in the power supply voltage.

[0047] Example 3

[0048] like Figure 4 As shown, the PWM modulator includes an operational amplifier inverting adder circuit and a PWM modulation circuit, wherein the input terminal of the operational amplifier inverting adder circuit is set as the input terminal of the PWM modulator, and the output terminal of the PWM modulation circuit is set as the output terminal of the PWM modulator.

[0049] The operational amplifier inverting adder circuit mixes and modulates the audio input signal with the preset switch music signal to generate a baseband signal; the PWM modulation circuit converts the synthesized baseband signal into a PWM waveform, uses the phase amplitude characteristics of the preset switch music signal to suppress popping components, sets the modulated baseband signal as the output signal of the PWM modulator, and completes the output.

[0050] The operational amplifier inverting adder circuit includes a memory MEM, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a seventeenth resistor R17, and a third amplifier U3. One end of the thirteenth resistor R13 is designated as the second input terminal P2. One end of the fourteenth resistor R14 is connected to a fourth voltage source VCC4, and the other end is connected to one end of the memory MEM. The other end of the thirteenth resistor R13, the other end of the memory MEM, one end of the fifteenth resistor R15, and the inverting input terminal of the third amplifier U3 are connected to the same point and designated as terminal E5. The non-inverting output terminal of the third amplifier U3 is connected in series with the seventeenth resistor R17 and the ground terminal. Terminal E5 is designated as the output terminal of the operational amplifier inverting adder circuit.

[0051] The thirteenth resistor R13 and the fourteenth resistor R14 control the current magnitude of the input signal, and together with the feedback resistor R15, determine the amplification factor of the input channel. In this embodiment, the input signal of the second input terminal P2 is set as the audio input signal, and the storage signal of the memory MEM is set as the preset switch music signal. In specific implementation, there is no specific limitation on which terminal they are input to. The fifteenth resistor R15 is used to connect the output terminal and the inverting input terminal of the operational amplifier to form a negative feedback loop. The seventeenth resistor R17 is used to automatically adjust the output voltage inside the operational amplifier so that the potential of the inverting terminal is approximately equal to the potential of the non-inverting terminal, realizing the linear precision operation of the operational amplifier. The third amplifier U3 is an operational amplifier with a negative feedback configuration. Its inverting input terminal receives the weighted voltage from two signal sources: the audio input signal and the preset switch music signal. The operational amplifier adjusts its own output according to the virtual short principle so that the voltage of the inverting terminal is equal to that of the non-inverting terminal, thereby outputting a mixed signal that is an inversely weighted superposition of the two input signals. The preset switch music signal is mixed into this circuit to "mask" the popping sound signal. This utilizes the characteristics of human hearing to reduce the perception of popping sounds, and the output is a mixed baseband signal, which is easily encoded into a pulse width signal by the PWM modulation module, improving response speed and stability. As a feasible implementation, the output voltage value of the operational amplifier inverting adder circuit can be calculated as follows: Let the output voltage of the operational amplifier inverting adder circuit be expressed as... V p2 This is expressed as the voltage value at the second input terminal P2, where V p3 This is represented as the voltage value of the memory MEM.

[0052] Further, the PWM modulation circuit includes a sixteenth resistor R16, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a second capacitor C2, a third capacitor C3, and a fourth amplifier U4. One end of the sixteenth resistor R16 is set as the input terminal of the PWM modulation circuit, and the other end of the sixteenth resistor R16 is connected to the same point as one end of the second capacitor C2 and one end of the eighteenth resistor R18. The other end of the eighteenth resistor R18 is connected to the same point as the non-inverting input terminal of the fourth amplifier U4 and one end of the third capacitor C3, and the other end of the third capacitor C3 is connected to the same point as one end of the nineteenth resistor R19 and the ground terminal. The other end of the nineteenth resistor R19 is connected to the same point as the inverting input terminal of the fourth amplifier U4 and one end of the twentieth resistor R20. The other end of the twentieth resistor R20 is connected to the same point as the other end of the second capacitor C2 and the output terminal of the fourth amplifier U4 and is set as terminal E6. Terminal E4 is set as the second output terminal Q2, representing the output terminal of the PWM modulation circuit.

[0053] The sixteenth resistor R16 and the second capacitor C2 together form an input filter network to smooth the input signal and reduce high-frequency interference. The eighteenth resistor R18 is used as a voltage distribution and signal attenuation element, working with the third capacitor C3 to buffer and filter the input signal. The nineteenth resistor R19 and the feedback resistor twentieth resistor R20 together form a negative feedback loop to adjust the amplifier's gain and response speed, thereby precisely controlling the duty cycle response of the PWM waveform and dynamically adjusting the PWM pulse width according to the amplitude of the baseband signal. The twentieth resistor R20 constitutes part of the negative feedback path. By changing the feedback strength, the twentieth resistor R20 adjusts the slope of the PWM waveform's duty cycle curve, making the output pulse width follow the baseband signal more smoothly, rather than abruptly changing, thus suppressing popping noises caused by edge abrupt changes. The second capacitor C2 is used to sample and integrate the baseband signal in each PWM cycle, and in conjunction with the twentieth resistor R20, generates a ramp reference wave, making the waveform edges of the PWM signal smoother and reducing edge spikes. The third capacitor C3 is used to suppress transient fluctuations in the reference level, ensuring that the PWM comparator compares against a constant reference in each cycle, improving linearity and repeatability. The fourth amplifier U4 performs voltage comparison and feedback regulation. The non-inverting input of the fourth amplifier U4 receives the reference signal after filtering the baseband signal, while the inverting input receives a portion of the feedback signal. When the input baseband signal voltage is higher than the reference level, U4 outputs a high level; when it is lower than the reference level, it outputs a low level, thereby generating a variable-width PWM pulse signal. The duty cycle dynamically changes with the input amplitude, enabling dynamic judgment and control of audio popping characteristics in an analog manner. The output of the fourth amplifier U4, which is also the output of the PWM modulator, is represented by the second output terminal P2, outputting the comparison result as a PWM waveform in real time.

[0054] Furthermore, as a feasible implementation, the PWM modulation circuit further includes a third voltage source VCC3, a fourth capacitor C4, and a fifth capacitor C5. One end of the fourth capacitor C4 is connected to one end of the fifth capacitor C5, the positive power supply terminal of the fourth amplifier U4, and the third voltage source VCC3 at the same point. The other end of the fourth capacitor C4 is connected to the other end of the fifth capacitor C5 and the ground terminal at the same point. The output noise density of the third voltage source VCC3 is less than 10μV, and the output current is greater than or equal to 100mA.

[0055] The third voltage source VCC3 provides a stable DC power supply voltage to the fourth amplifier U4, which meets the power supply requirements for the normal linear operation of the operational amplifier U4. The fourth capacitor C4 and the fifth capacitor C5 are connected in parallel between the third voltage source VCC3 and the ground terminal, forming a bypass filter circuit. The fourth capacitor C4 is a large-capacity capacitor used to filter out low-frequency power supply ripple; the fifth capacitor C5 is a small-capacity capacitor used to filter out high-frequency spikes and transient interference. This bypass filter circuit ensures that the power supply quality to U4 at the moment of power-on determines the reliability of its decision to output a PWM wave, and also significantly reduces false triggering phenomena such as power amplifier popping caused by unstable power supply. The output noise density of the third voltage source VCC3 is less than 10μV, which can significantly reduce DC offset, level jitter, and high-frequency glitches introduced by power supply noise inside the operational amplifier; the output current is greater than or equal to 100mA, which can provide sufficient current for the fourth amplifier U4 to drive the energy transients during strong loads or high-frequency switching in subsequent stages.

[0056] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for suppressing popping noises upon power-on of an audio power amplifier based on the sound masking effect, characterized in that, The method includes: Step S1: Measure the audio input signal for audio power amplification of the target power amplifier device, preset the voltage reference value for audio detection, set the audio detection circuit and PWM modulator, and input the audio input signal into the audio detection circuit; Step S2: When the input voltage value of the audio input signal is lower than the voltage reference value, the audio detection circuit generates a low-level suppression signal; when the input voltage value is higher than the voltage reference value, the audio detection circuit generates a high-level working signal. Step S3: Input the audio input signal into the PWM modulator to generate a PWM signal containing the modulated music signal. Connect both the PWM signal and the suppression signal to the input of the AND gate. Connect the output of the AND gate to the switching module through a buffer. Step S4: When the audio detection circuit generates a suppression signal, the switching module is turned off, and no impulse signal is generated at the power amplifier output. When the audio detection circuit generates a working signal, the switching module is turned on and transmits the PWM signal to the power amplifier output. The power amplifier output generates an amplified music signal and a power-on impulse signal. The audio detection circuit includes a T-type feedback network, an amplitude acquisition circuit, and a comparison output circuit connected in sequence. The input terminal of the T-type feedback network is set as the input terminal of the audio detection circuit, and the output terminal of the comparison output circuit is set as the output terminal of the audio detection circuit. The T-type feedback network performs high-frequency noise cancellation and impedance matching on the audio input signal, and increases the signal amplitude to a processable range; the amplitude acquisition circuit flips the negative half-cycle signal to positive polarity to convert the bidirectional parameter value of the audio input signal into a unipolar parameter amplitude; the comparison output circuit compares the amplitude signal with a preset threshold and generates a corresponding level control signal to the AND gate input.

2. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 1, characterized in that, The structure of the T-type feedback network includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first amplifier U1. One end of the first resistor R1 is designated as the first input terminal P1, and the other end of the first resistor R1 is connected to the inverting input terminal of the first amplifier U1 and one end of the third resistor R3 at the same point. One end of the second resistor R2 is connected to the non-inverting input terminal of the first amplifier U1, and the other end of the second resistor R2 is grounded. The other end of the third resistor R3 is connected to one end of the fifth resistor R5 and one end of the fourth resistor R4 at the same point, and the other end of the fourth resistor R4 is grounded. The other end of the fifth resistor R5 is connected to the output terminal of the first amplifier U1 at the same point and designated as terminal E1. Terminal E1 is designated as the output terminal of the T-type feedback network.

3. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 1, characterized in that, The amplitude acquisition circuit includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second amplifier U2, a first diode D1, and a second diode D2. One end of the sixth resistor R6 and one end of the seventh resistor R7 are connected to the same point and designated as endpoint E2, which is the input terminal of the amplitude acquisition circuit. The other end of the sixth resistor R6 is connected to the cathode of the first diode D2, one end of the eighth resistor R8, and the inverting input terminal of the second amplifier U2 at the same point. The anode of the first diode D1, the output terminal of the second amplifier U2, and the cathode of the second diode D2 are connected to the same point. The non-inverting input terminal of the second amplifier U2 is connected in series with the ninth resistor R9 and the ground terminal. The other end of the eighth resistor R8, the anode of the second diode D2, and one end of the tenth resistor R10 are connected to the same point, and the other end of the tenth resistor R10 and the other end of the seventh resistor R7 are connected to the same point and designated as endpoint E3. The amplitude acquisition circuit is connected to the comparison output circuit through endpoint E3.

4. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 3, characterized in that, The comparison output circuit includes a first comparator Y1, a first voltage source VCC1, a second voltage source VCC2, an eleventh resistor R11, a twelfth resistor R12, and a first capacitor C1. The non-inverting input terminal of the first comparator Y1 and one end of the eleventh resistor R11 are connected to terminal E3. The positive power supply terminal of the first comparator Y1 is connected to the same point as the first voltage source VCC1 and one end of the first capacitor C1, and the other end of the first capacitor C1 is grounded. The inverting input terminal of the first comparator Y1 is connected in series with the twelfth resistor R12 and the second voltage source VCC2. The other end of the eleventh resistor R11 is connected to the same point as the output terminal of the first comparator Y1 and is set as terminal E4. Terminal E4 is set as the first output terminal Q1, representing the output terminal of the audio detection circuit.

5. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 1, characterized in that, The PWM modulator includes an operational amplifier inverting adder circuit and a PWM modulation circuit, wherein the input terminal of the operational amplifier inverting adder circuit is set as the input terminal of the PWM modulator, and the output terminal of the PWM modulation circuit is set as the output terminal of the PWM modulator. The operational amplifier inverting adder circuit mixes and modulates the audio input signal with the preset switch music signal to generate a baseband signal; the PWM modulation circuit converts the synthesized baseband signal into a PWM waveform, uses the phase amplitude characteristics of the preset switch music signal to suppress popping components, sets the modulated baseband signal as the output signal of the PWM modulator, and completes the output.

6. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 5, characterized in that, The operational amplifier inverting adder circuit includes a memory MEM, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a seventeenth resistor R17, and a third amplifier U3. One end of the thirteenth resistor R13 is designated as the second input terminal P2. One end of the fourteenth resistor R14 is connected to a fourth voltage source VCC4, and the other end is connected to one end of the memory MEM. The other end of the thirteenth resistor R13, the other end of the memory MEM, one end of the fifteenth resistor R15, and the inverting input terminal of the third amplifier U3 are connected to the same point and designated as terminal E5. The non-inverting output terminal of the third amplifier U3 is connected in series with the seventeenth resistor R17 and the ground terminal. Terminal E5 is designated as the output terminal of the operational amplifier inverting adder circuit.

7. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 5, characterized in that, The PWM modulation circuit includes a sixteenth resistor R16, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a second capacitor C2, a third capacitor C3, and a fourth amplifier U4. One end of the sixteenth resistor R16 is set as the input terminal of the PWM modulation circuit. The other end of the sixteenth resistor R16 is connected to one end of the second capacitor C2 and one end of the eighteenth resistor R18 at the same point. The other end of the eighteenth resistor R18 is connected to the non-inverting input terminal of the fourth amplifier U4 and one end of the third capacitor C3 at the same point. The other end of the third capacitor C3 is connected to one end of the nineteenth resistor R19 and the ground terminal at the same point. The other end of the nineteenth resistor R19 is connected to the inverting input terminal of the fourth amplifier U4 and one end of the twentieth resistor R20 at the same point. The other end of the twentieth resistor R20 is connected to the other end of the second capacitor C2 and the output terminal of the fourth amplifier U4 at the same point and set as terminal E6. Terminal E4 is set as the second output terminal Q2, which represents the output terminal of the PWM modulation circuit.

8. The method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect according to claim 7, characterized in that, The PWM modulation circuit also includes a third voltage source VCC3, a fourth capacitor C4, and a fifth capacitor C5. One end of the fourth capacitor C4 is connected to one end of the fifth capacitor C5, the positive power supply terminal of the fourth amplifier U4, and the third voltage source VCC3 at the same point. The other end of the fourth capacitor C4 is connected to the other end of the fifth capacitor C5 and the ground terminal at the same point.

9. A method for suppressing popping noise during power-on of an audio power amplifier based on the sound masking effect, as described in claim 8, is characterized in that... The output noise density of the third voltage source VCC3 is less than 10μV, and the output current is greater than or equal to 100mA.

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