Audio amplification circuit and control method thereof

Abstract

An audio amplification circuit includes a pulse width modulation circuit, an auxiliary loop circuit, and a main loop circuit. The auxiliary loop circuit corresponds to a first variable resistance value and a first variable current value. The main loop circuit is coupled between a second node, an output terminal, and a first node. The main loop circuit corresponds to a second variable resistance value and a second variable current value. When the auxiliary loop circuit enters a first control state, the second variable resistance value is decreased and the second variable current value is increased to cause the main loop circuit to enter a second control state. When the main loop circuit enters the second control state, the first variable resistance value is increased and the first variable current value is decreased to cause the auxiliary loop circuit to exit the first control state.

Description

Technical Field

[0001] This disclosure relates to an audio technology. In particular, it relates to an audio amplifier circuit and its control method for reducing pop noise. Background Technology

[0002] With the development of technology, many electronic devices can now play audio. However, in some related technologies, audio components (such as audio amplifier circuits) can generate popping noise during power-on, power-off, or various operational instants. This popping noise can cause an uncomfortable auditory experience for the user. Summary of the Invention

[0003] Some embodiments of this disclosure relate to an audio amplifier circuit. The audio amplifier circuit includes a pulse width modulation (PWM) circuit, an auxiliary circuit, and a main circuit. The PWM circuit is coupled between a first node and a second node. The auxiliary circuit is coupled between the second node and the first node. The auxiliary circuit corresponds to a first variable resistance value and a first variable current value. The main circuit is coupled between the second node, its output terminal, and the first node. The main circuit corresponds to a second variable resistance value and a second variable current value. When both the auxiliary circuit and the main circuit are active, after the auxiliary circuit enters a first control state, the second variable resistance value is decreased and the second variable current value is increased to cause the main circuit to enter a second control state. After the main circuit enters the second control state, the first variable resistance value is increased and the first variable current value is decreased to cause the auxiliary circuit to exit the first control state.

[0004] Some embodiments of this disclosure relate to a control method for an audio amplifier circuit. The audio amplifier circuit includes an auxiliary circuit and a main circuit. The auxiliary circuit corresponds to a first variable resistance value and a first variable current value. The main circuit corresponds to a second variable resistance value and a second variable current value. The control method includes the following operations: when both the auxiliary circuit and the main circuit are turned on, after the auxiliary circuit enters a first control state, the second variable resistance value is decreased and the second variable current value is increased to cause the main circuit to enter a second control state; and after the main circuit enters the second control state, the first variable resistance value is increased and the first variable current value is decreased to cause the auxiliary circuit to exit the first control state.

[0005] In summary, the audio amplification circuit and control method disclosed herein can effectively reduce popping noise to avoid causing uncomfortable auditory experience to the user. Attached Figure Description

[0006] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the accompanying drawings are described below:

[0007] Figure 1 This is a schematic diagram of an audio amplifier circuit, a digital-to-analog converter, and an audio player described in accordance with some embodiments of the present disclosure;

[0008] Figure 2A This is a schematic diagram of an auxiliary variable resistor depicted according to some embodiments of the present disclosure;

[0009] Figure 2B This is a schematic diagram of an auxiliary driver depicted according to some embodiments of the present disclosure;

[0010] Figure 2C This is a schematic diagram of a feedback variable resistor depicted according to some embodiments of the present disclosure;

[0011] Figure 2D This is a schematic diagram of a main drive depicted according to some embodiments of the present disclosure;

[0012] Figure 2E It is described in accordance with some embodiments of this disclosure. Figure 2D A detailed schematic diagram of the driving circuit in the diagram;

[0013] Figures 3A to 3C It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram of the operation of an audio amplifier circuit;

[0014] Figure 4 It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram showing the changes in the audio amplifier circuit;

[0015] Figure 5 It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram showing the changes in the audio amplifier circuit; and

[0016] Figure 6 This is a flowchart depicting a control method according to some embodiments of the present disclosure. Detailed Implementation

[0017] As used herein, the term "coupled" may also refer to "electrical coupling," and the term "connection" may also refer to "electrical connection." "Coupled" and "connection" may also refer to the cooperation or interaction of two or more components.

[0018] refer to Figure 1 . Figure 1 This is a schematic diagram of an audio amplifier circuit 100, a digital-to-analog converter DAC, and an audio player A, as depicted in accordance with some embodiments of this disclosure.

[0019] The audio amplifier circuit 100 may be a Class D audio amplifier. The audio amplifier circuit 100 may be coupled between the digital-to-analog converter (DAC) and the audio player A. Specifically, the audio amplifier circuit 100 may be coupled to the DAC at its input terminal IN to receive the analog audio source input signal VIN from the DAC. The audio amplifier circuit 100 may be coupled to the audio player A at its output terminal OUT to output the analog audio source output signal VOUT to the audio player A. The audio player A can then play the corresponding audio based on the analog audio source output signal VOUT. In some embodiments, the audio player A may be a speaker or other sound-emitting device.

[0020] by Figure 1 For example, the audio amplifier circuit 100 includes an input resistor RIN, a pulse width modulation circuit 110, an auxiliary loop circuit 120, and a main loop circuit 130. The input resistor RIN is coupled between the input terminal IN and node N1. The pulse width modulation circuit 110 is coupled between node N1 and node N2. The auxiliary loop circuit 120 is coupled between node N2 and node N1. The main loop circuit 130 is coupled between node N2, the output terminal OUT, and node N1.

[0021] by Figure 1 For example, the pulse width modulation circuit 110 includes a filter 111, a triangular wave generator 112, and a pulse width modulation generator (PWM generator) 113. The filter 111 is coupled to node N1. The filter 111 generates a filtered signal FS based on the input signal VIN. The triangular wave generator 112 generates a triangular wave signal RS. The pulse width modulation generator 113 receives the filtered signal FS and the triangular wave signal RS to generate a pulse width modulation signal PWM. For example, the pulse width modulation generator 113 compares the filtered signal FS with the triangular wave signal RS to generate the pulse width modulation signal PWM.

[0022] The auxiliary circuit 120 includes an auxiliary driver 121 and an auxiliary variable resistor RAUX. The auxiliary driver 121 is coupled to node N2 to receive a pulse width modulation (PWM) signal and outputs a drive signal DS according to the PWM signal. The auxiliary driver 121 can correspond to a variable current value. The auxiliary variable resistor RAUX is coupled between the auxiliary driver 121 and node N1. The auxiliary variable resistor RAUX can correspond to a variable resistance value.

[0023] The main circuit 130 includes a power driver 131 and a feedback variable resistor RFB. The power driver 131 is coupled between node N2 and the output terminal OUT. The power driver 131 generates an analog audio source output signal VOUT based on a pulse width modulation (PWM) signal. The power driver 131 can correspond to a variable current value. The feedback variable resistor RFB is coupled between the output terminal OUT and node N1. The feedback variable resistor RFB can correspond to a variable resistance value.

[0024] refer to Figure 2A . Figure 2A This is a schematic diagram of an auxiliary variable resistor RAUX1 depicted according to some embodiments of the present disclosure. In some embodiments, the auxiliary variable resistor RAUX1 can be used to implement... Figure 1 The auxiliary variable resistor RAUX in the system. Figure 2A For example, the auxiliary variable resistor RAUX1 includes a switch S11, multiple (e.g., two) resistors R1, and multiple (e.g., two) switches S1. The switches S11 are connected in series with the resistors R1, while each switch S1 is connected in parallel with its corresponding resistor R1. The variable resistance value of the auxiliary variable resistor RAUX1 can be changed by controlling these switches S1.

[0025] The number of resistors R1 and switches S1 described above is merely illustrative and is not intended to limit this disclosure. Various other applicable quantities are within the scope of this disclosure.

[0026] refer to Figure 2B . Figure 2B This is a schematic diagram of an auxiliary driver 121A depicted according to some embodiments of the present disclosure. In some embodiments, the auxiliary driver 121A can be used to implement... Figure 1 The auxiliary driver 121 in the middle. Figure 2B For example, the auxiliary driver 121A includes a front driver DR1, multiple (e.g., four) transistors M2, and multiple (e.g., four) switches S2. Each pair of transistors M2 can form a transistor string (P-type transistors are shown above, and N-type transistors below in the diagram). Two transistors M2 in each string are connected in series at node N11 (or N12) and in series between the supply voltage terminal VDD1 and the ground terminal GND1. That is, these transistor strings are connected in parallel. Each switch S2 is coupled between the front driver DR1 and the control terminal (e.g., the gate terminal) of the corresponding transistor M2. Nodes N11 and N12 are coupled to the output pin PAD1 of the auxiliary driver 121A. By controlling these switches S2, the variable current value of the auxiliary driver 121A can be changed.

[0027] The number of transistors M2 and switches S2 described above is merely illustrative and is not intended to limit this disclosure. Various other suitable quantities are within the scope of this disclosure.

[0028] refer to Figure 2C . Figure 2C This is a schematic diagram of a feedback variable resistor RFB1 depicted according to some embodiments of the present disclosure. In some embodiments, the feedback variable resistor RFB1 can be used to implement... Figure 1 The feedback variable resistor RFB in the middle. Figure 2C For example, the feedback variable resistor RFB1 includes a switch S33, multiple (e.g., 8) resistors R3, and multiple (e.g., 8) switches S3. Switches S33 are connected in series with these resistors R3. Each switch S3 is connected in parallel with its corresponding resistor R3. By controlling these switches S3, the variable resistance value of the feedback variable resistor RFB1 can be changed.

[0029] The quantities of resistor R3 and switch S3 described above are merely illustrative and are not intended to limit this disclosure. Various other applicable quantities are within the scope of this disclosure.

[0030] refer to Figure 2D . Figure 2D This is a schematic diagram of a main drive 131A depicted according to some embodiments of the present disclosure. In some embodiments, the main drive 131A can be used to implement Figure 1 The main drive 131 in the system. Figure 2D For example, the main driver 131A includes a front driver DR4 and multiple (e.g., four) driver circuits 1311-1314. The driver circuits 1311-1314 are coupled between the front driver DR4 and the output pin PAD4.

[0031] refer to Figure 2E . Figure 2E It is described in accordance with some embodiments of this disclosure. Figure 2D A schematic diagram of the drive circuit 1311 is shown. Other drive circuits 1312-1314 have similar circuit architectures. Figure 2E For example, the drive circuit 1311 includes multiple (e.g., four) transistors M4 and multiple (e.g., four) switches S4. Each pair of transistors M4 can form a transistor string (P-type transistors are shown above and N-type transistors below in the diagram). Two transistors M4 in each string are connected in series at node N41 (or N42) and in series between the supply voltage terminal VDD4 and the ground terminal GND4. That is, these transistor strings are connected in parallel. Each switch S4 is coupled between the front driver DR4 and the control terminal (e.g., the gate terminal) of the corresponding transistor M4. Nodes N41-N42 are coupled to the auxiliary driver 131A (e.g.,...). Figure 2D The output pin PAD4 (shown) can be used to control the variable current value of the main driver 131A.

[0032] The number of transistors M4 and switches S4 described above is merely illustrative and is not intended to limit this disclosure. Various other suitable quantities are within the scope of this disclosure.

[0033] In some embodiments, the switches S1-S4 can be turned on or off by one or more control circuits inside or outside the audio amplifier circuit 100.

[0034] refer to Figures 1 to 4 . Figures 3A to 3C It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram of the operation of the audio amplifier circuit 100. Figure 4 It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram showing the changes in the audio amplifier circuit 100.

[0035] In the first stage, such as Figure 3A As shown, the auxiliary circuit 120 is turned on to establish a bias voltage for the pulse width modulation circuit 110, while the main circuit 130 is turned off.

[0036] Figure 2A When switch S11 of the auxiliary variable resistor RAUX1 is turned on, one of the switches S1 of the auxiliary variable resistor RAUX1 can be turned off while the other switch S1 can be turned on, so that the variable resistance value of the auxiliary variable resistor RAUX1 is r (assuming the resistance value of a resistor R1 is r), such as... Figure 4 As shown. Additionally... Figure 2B In the auxiliary driver 121A, both switches S2 can be turned on to control two transistors M2 (the pair of transistors M2 on the left of the figure, one P-type transistor and one N-type transistor) to be turned on, and to control two other transistors M2 (the pair of transistors M2 on the right of the figure, one P-type transistor and one N-type transistor) to be turned off. In this case, the variable current value of the auxiliary driver 121A is i.

[0037] on the other hand, Figure 2C The switch S33 of the feedback variable resistor RFB1 is not conducting, and Figure 2D These switches (such as those in drive circuits 1311-1314 of the main driver 131A) Figure 2E All of the switches S4 shown can be turned off to shut down the main circuit 130. At this time, the transfer function T100 of the audio amplifier circuit 100 (including the contributions from the transfer function T120 of the auxiliary circuit 120 and the transfer function T130 of the main circuit 130) is T.

[0038] Next, we move on to the second stage, such as... Figure 3BAs shown, the auxiliary circuit 120 remains on, and the main circuit 130 is turned on. That is, both the auxiliary circuit 120 and the main circuit 130 are turned on.

[0039] by Figure 4 For example, Figure 2A The variable resistance value of the auxiliary variable resistor RAUX1 remains at r and Figure 2B The variable current value of the auxiliary driver 121A remains at i (first control state). On the other hand, Figure 2C In the feedback variable resistor RFB1, all switches S3 can be off and switch S33 can be on, making the variable resistance of the feedback variable resistor RFB1 8r (assuming the resistance of a resistor R3 is r). Additionally, Figure 2D The two switches S4 of the main driver 131A (e.g.: Figure 2E The pair of switches S4 on the left side of the circuit is turned on to control the corresponding transistor M4 to turn on (one pair of transistors M4 at a time, one P-type transistor and one N-type transistor), while other switches S4 (e.g., other switches S4 in drive circuit 1311 and these switches S4 in drive circuits 1312-1314) are not turned on to turn off other transistors M4. In this case, the variable current value of the main driver 131A is 0.125i. At this time, the transfer function T100 of the audio amplifier circuit 100 is 0.89T (i.e., 8Z(s) / (Z(s)+8Z(s))×T) (which can be regarded as a parallel relationship), where Z(s) is the impedance transfer function.

[0040] Next, control Figure 2C These switches S3 are used to adjust the variable resistance value of the feedback variable resistor RFB1 to 4r and control Figure 2D These switches (such as those in drive circuits 1311-1314 of the medium power driver 131A) Figure 2E These switches S4) are used to adjust the variable current value of the main driver 131A to 0.25i. At this time, the transfer function T100 of the audio amplifier circuit 100 becomes 0.8T (i.e., 4Z(s) / (Z(s)+4Z(s))×T).

[0041] Next, control Figure 2C These switches S3 are used to adjust the variable resistance value of the feedback variable resistor RFB1 to 2r and control Figure 2D These switches (such as those in drive circuits 1311-1314 of the medium power driver 131A) Figure 2E These switches S4) are used to adjust the variable current value of the main driver 131A to 0.5i. At this time, the transfer function T100 of the audio amplifier circuit 100 is 0.67T (i.e., 2Z(s) / (Z(s)+2Z(s))×T).

[0042] then, Figure 2C The variable resistance value of the feedback variable resistor RFB1 remains at 2r and Figure 2D The variable current value of the main driver 131A remains at 0.5i (entering the second control state). Meanwhile, the control... Figure 2A These switches S1 are used to adjust the variable resistance value of the auxiliary variable resistor RAUX1 to 2r and control Figure 2B These switches S2 are used to adjust the variable current value of the auxiliary driver 121A to 0.5i (disengaging from the first control state). At this time, the transfer function T100 of the audio amplifier circuit 100 is T (i.e., 2Z(s) / (Z(s)+Z(s))×T).

[0043] In summary, in the second stage, when the auxiliary circuit 120 enters the first control state (as described above) Figure 2A The variable resistance value of the auxiliary variable resistor RAUX1 is r and Figure 2B After the variable current value of the auxiliary driver 121A is i), the variable resistance value of the feedback variable resistor RFB1 is gradually decreased while the variable current value of the main driver 131A is gradually increased to make the main circuit circuit 130 enter the second control state. When the main circuit circuit 130 enters the second control state ( Figure 2C The variable resistance value of the feedback variable resistor RFB1 is 2r and Figure 2D After the variable current value of the main driver 131A is 0.5i, the variable resistance value of the auxiliary variable resistor RAUX1 is increased and the variable current value of the auxiliary driver 121A is decreased so that the auxiliary loop circuit 120 is removed from the first control state.

[0044] Next, we move on to the third stage, such as... Figure 3C As shown, the main circuit 130 remains on, while the auxiliary circuit 120 is turned off. For example, Figure 2A The switch S11 of the auxiliary variable resistor RAUX1 can be non-conducting and Figure 2B All switches S2 in the auxiliary driver 121A can be deactivated to shut down the auxiliary circuit 120. For example... Figure 4 As shown, at this time, the transfer function T100 of the audio amplifier circuit 100 is restored to T.

[0045] In some related technologies, during the turn-on process of an audio amplifier circuit, popping noises can be generated due to instantaneous and huge voltage changes, which can cause an uncomfortable auditory experience for the user.

[0046] Compared to the aforementioned related technologies, this disclosure first establishes a bias voltage for the pulse width modulation circuit 110 using the auxiliary circuit 120 in the first stage, then gradually turns on the main circuit 130 in the second stage with multiple switching steps, and finally turns off the auxiliary circuit 120 in the third stage. This effectively reduces popping noise, thus avoiding uncomfortable auditory experiences for the user. Furthermore, in some embodiments of this disclosure (e.g.: Figure 4 The change in transfer function T100 between two adjacent switching steps is less than 0.5T. Therefore, compared with many related technologies, this disclosure can effectively reduce pop noise.

[0047] Figure 5 It is described in accordance with some embodiments of this disclosure. Figure 1 A schematic diagram showing the changes in the audio amplifier circuit 100. Figure 5 The first and third phases are similar Figure 4 The first and third stages.

[0048] However, compared to Figure 4 The second phase, Figure 5 The second phase involves more switching steps. In other words, Figure 5 In the second stage, the change in the transfer function between two adjacent switching steps is less than Figure 4 The change in the transfer function between two adjacent switching steps in the second stage.

[0049] The following will combine Figures 1 to 2D right Figure 5 Please provide an explanation.

[0050] by Figure 5 In the second stage example, when the variable resistance value of the auxiliary variable resistor RAUX1 remains at r and the variable current value of the auxiliary driver 121A remains at i, the variable resistance value of the feedback variable resistor RFB1 can be adjusted to 8r and the variable current value of the main driver 131A can be adjusted to 0.125i. Then, the variable resistance value of the feedback variable resistor RFB1 can be further adjusted (reduced) to 4r and the variable current value of the main driver 131A can be further adjusted (increased) to 0.25i. Next, the variable resistance value of the feedback variable resistor RFB1 can continue to be adjusted (reduced) to 3r and the variable current value of the main driver 131A can continue to be adjusted (increased) to 0.33i.

[0051] Next, the variable resistance value of the feedback variable resistor RFB1 can be maintained at 3r and the variable current value of the main driver 131A can be maintained at 0.33i, while the variable resistance value of the auxiliary variable resistor RAUX1 can be adjusted (increased) to 1.5r and the variable current value of the auxiliary driver 121A can be adjusted (decreased) to 0.67i.

[0052] Next, the variable resistance value of the auxiliary variable resistor RAUX1 can be maintained at 1.5r and the variable current value of the auxiliary driver 121A can be maintained at 0.67i, while the variable resistance value of the feedback variable resistor RFB1 can be adjusted (reduced) to 2r and the variable current value of the main driver 131A can be adjusted (increased) to 0.5i.

[0053] Next, the variable resistance value of the feedback variable resistor RFB1 can be maintained at 2r and the variable current value of the main driver 131A can be maintained at 0.5i, while the variable resistance value of the auxiliary variable resistor RAUX1 can be adjusted (increased) to 2r and the variable current value of the auxiliary driver 121A can be adjusted (decreased) to 0.5i.

[0054] Next, the variable resistance value of the auxiliary variable resistor RAUX1 can be maintained at 2r and the variable current value of the auxiliary driver 121A can be maintained at 0.5i, while the variable resistance value of the feedback variable resistor RFB1 can be adjusted (reduced) to 1.5r and the variable current value of the main driver 131A can be adjusted (increased) to 0.67i.

[0055] Next, the variable resistance value of the feedback variable resistor RFB1 can be maintained at 1.5r and the variable current value of the main driver 131A can be maintained at 0.67i, while the variable resistance value of the auxiliary variable resistor RAUX1 can be adjusted (increased) to 3r and the variable current value of the auxiliary driver 121A can be adjusted (decreased) to 0.33i.

[0056] Next, the variable resistance value of the auxiliary variable resistor RAUX1 can be maintained at 3r and the variable current value of the auxiliary driver 121A can be maintained at 0.33i, while the variable resistance value of the feedback variable resistor RFB1 can be adjusted (reduced) to r and the variable current value of the main driver 131A can be adjusted (increased) to i.

[0057] Therefore, compared to Figure 4 , Figure 5 The transfer function changes less between two adjacent switching steps, which can more effectively reduce pop noise.

[0058] In some further embodiments, the second stage may include more subtle switching steps to minimize the change in the transfer function between two adjacent switching steps.

[0059] refer to Figure 6 . Figure 6 This is a flowchart illustrating a control method 600 according to some embodiments of the present disclosure. In some embodiments, the control method 600 may be applied to... Figure 1 The audio amplifier circuit 100 is used in the middle. Figure 6For example, control method 600 includes operation S610 and operation S620.

[0060] In operation S610, with both the auxiliary circuit 120 and the main circuit 130 activated, after the auxiliary circuit 120 enters the first control state, the variable resistance value of the feedback variable resistor RFB is decreased and the variable current value of the main driver 131 is increased to cause the main circuit 130 to enter the second control state. Figure 2C as well as Figure 2E For example, the variable resistance value of the feedback variable resistor RFB1 and the variable current value of the main driver 131A can be controlled by controlling switches S3 and S4 respectively.

[0061] In operation S620, after the main circuit 130 enters the second control state, the variable resistance value of the auxiliary variable resistor RAUX is increased and the variable current value of the auxiliary driver 121 is decreased to cause the auxiliary circuit 120 to exit the first control state. Figure 2A as well as Figure 2B For example, the variable resistance value of the auxiliary variable resistor RAUX1 and the variable current value of the auxiliary driver 121A can be controlled by controlling switches S1 and S2 respectively.

[0062] In summary, the audio amplification circuit and control method disclosed herein can effectively reduce popping noise to avoid causing uncomfortable auditory experience to the user.

[0063] Although this disclosure has been described above with reference to embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make various changes and improvements without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the appended claims.

[0064] Explanation of reference numerals in the attached figures:

[0065] 100: Audio amplifier circuit

[0066] 110: Pulse Width Modulation Circuit

[0067] 111: Filter

[0068] 112: Triangular Wave Generator

[0069] 113: Pulse Width Modulation Generator

[0070] 120: Auxiliary circuit

[0071] 121: Auxiliary driver

[0072] 130: Main circuit

[0073] 131, 131A: Power driver

[0074] 1311, 1312, 1313, 1314: Drive circuits

[0075] 600: Control Method

[0076] DAC: Digital-to-Analog Converter

[0077] A: Audio player

[0078] IN: Input terminal

[0079] OUT: Output terminal

[0080] VIN: Analog audio input signal

[0081] VOUT: Analog audio source output signal

[0082] RIN: Input resistance

[0083] N1: Node

[0084] N2: Node

[0085] DS: Drive signal

[0086] FS: Filtered signal

[0087] RS: Triangular wave signal

[0088] PWM: Pulse Width Modulation signal

[0089] RAUX, RAUX1: Auxiliary variable resistor

[0090] RFB, RFB1: Feedback variable resistors

[0091] R1, R3: Resistors

[0092] M2, M4: Transistors

[0093] S1, S2, S3, S4, S11, S33: Switches

[0094] DR1, DR4: Front drive

[0095] VDD1, VDD4: Voltage supply terminals

[0096] GND1, GND4: Ground

[0097] N11, N12, N41, N42: Nodes

[0098] PAD1, PAD4: Output pins

[0099] T100, T120, T130: Transfer functions

[0100] S610, S620: Operation

Claims

1. An audio amplifier circuit, comprising: A pulse width modulation circuit is coupled between the first node and the second node; An auxiliary circuit is coupled between the second node and the first node, wherein the auxiliary circuit corresponds to a first variable resistance value and a first variable current value; and A main circuit is coupled between the second node, the output terminal, and the first node, wherein the main circuit corresponds to a second variable resistance value and a second variable current value, and the main circuit includes a power driver coupled between the second node and the output terminal and a feedback variable resistor coupled between the output terminal and the first node. When both the auxiliary circuit and the main circuit are turned on, after the auxiliary circuit enters the first control state, the second variable resistance value is reduced and the second variable current value is increased to make the main circuit enter the second control state. After the main circuit enters the second control state, the first variable resistance value is increased and the first variable current value is reduced to make the auxiliary circuit leave the first control state.

2. The audio amplifier circuit as claimed in claim 1, wherein when the auxiliary circuit enters the first control state, the second variable resistance value is gradually decreased and the second variable current value is gradually increased.

3. The audio amplifier circuit as described in claim 1, further comprising: An input resistor is coupled between the input terminal and the first node. The input terminal is used to receive analog audio source input signals, and the output terminal is used to output analog audio source output signals to the audio player.

4. The audio amplification circuit of claim 3, wherein the pulse width modulation circuit comprises: A filter, coupled to the first node, is used to generate a filtered signal based on the input signal; A triangular wave generator is used to output a triangular wave signal. as well as A signal generator, used to receive the filtered signal and the triangular wave signal, and coupled to the second node, The signal generator is used to compare the filtered signal with the triangular wave signal to generate a pulse width modulation signal.

5. The audio amplifier circuit of claim 4, wherein the power driver is configured to generate the analog audio source output signal according to the pulse width modulation signal; and The power driver is used to control the second variable current value, and the feedback variable resistor is used to control the second variable resistance value.

6. The audio amplifier circuit of claim 5, wherein the feedback variable resistor comprises: First switch; Multiple resistors, wherein the multiple resistors are coupled in series with the first switch; as well as A plurality of second switches, wherein each of the plurality of second switches is coupled in parallel to a corresponding resistor among the plurality of resistors. The power driver includes a plurality of drive circuits, each of the plurality of drive circuits comprising: Multiple transistor strings, wherein each of the multiple transistor strings comprises multiple transistors and the multiple transistors are connected in series with each other, and the multiple transistor strings are coupled in parallel with each other; and A plurality of switches, wherein each of the plurality of switches is coupled to the control terminal of a corresponding transistor among the plurality of transistors.

7. The audio amplifier circuit of claim 4, wherein the auxiliary circuit comprises: An auxiliary driver, coupled to the second node; and An auxiliary variable resistor is coupled between the auxiliary driver and the first node. The auxiliary driver is used to control the first variable current value, and the auxiliary variable resistor is used to control the first variable resistance value.

8. The audio amplifier circuit of claim 7, wherein the auxiliary variable resistor comprises: First switch; Multiple resistors, wherein the multiple resistors are coupled in series with the first switch; as well as A plurality of second switches, wherein each of the plurality of second switches is coupled in parallel to a corresponding resistor among the plurality of resistors. The auxiliary driver includes: Multiple transistor strings, wherein each of the multiple transistor strings comprises multiple transistors and the multiple transistors are connected in series with each other, and the multiple transistor strings are coupled in parallel with each other; and A plurality of switches, wherein each of the plurality of switches is coupled to the control terminal of a corresponding transistor among the plurality of transistors.

9. The audio amplifier circuit of claim 1, wherein the auxiliary circuit is turned on and the main circuit is turned off before both the auxiliary circuit and the main circuit are turned on, and wherein the main circuit remains on and the auxiliary circuit eventually turns off after both the auxiliary circuit and the main circuit are turned on.

10. A control method for an audio amplifier circuit, wherein the audio amplifier circuit includes an auxiliary circuit and a main circuit, the auxiliary circuit corresponding to a first variable resistance value and a first variable current value, and the main circuit corresponding to a second variable resistance value and a second variable current value, wherein the control method includes: When both the auxiliary circuit and the main circuit are activated, after the auxiliary circuit enters the first control state, the second variable resistance value is decreased and the second variable current value is increased to cause the main circuit to enter the second control state; and When the main circuit enters the second control state, the first variable resistance value is increased and the first variable current value is decreased to make the auxiliary circuit leave the first control state.

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