CN113179089A

CN113179089A - Audio power amplifier circuit, power limiting method thereof and electronic equipment

Info

Publication number: CN113179089A
Application number: CN202110420516.1A
Authority: CN
Inventors: 王伟
Original assignee: Shanghai Awinic Technology Co Ltd
Current assignee: Shanghai Awinic Technology Co Ltd
Priority date: 2021-04-19
Filing date: 2021-04-19
Publication date: 2021-07-27
Anticipated expiration: 2041-04-19
Also published as: CN113179089B

Abstract

The application discloses audio power amplifier circuit and power limiting method, an electronic equipment thereof, audio power amplifier circuit includes: the audio amplification module comprises an integral amplification unit, a signal modulation unit and a half-wave modulation mode detection unit; the half-wave modulation mode detection unit is used for enabling the audio amplification module to work in a half-wave modulation mode; the signal modulation unit is used for outputting a pulse width modulation signal; the power limiting module is used for comparing the output voltage of the output end of the integral amplifying unit with a threshold voltage and adjusting the input current of the input end of the integral amplifying unit according to a comparison result so as to limit the output voltage of the integral amplifying unit within a preset amplitude range; and the threshold voltage adjusting module is connected with the power limiting module and used for outputting the threshold voltage which is changed along with the control signal to the power limiting module. The audio power amplifier circuit can realize flexible and dynamic power limitation in a half-wave modulation mode.

Description

Audio power amplifier circuit, power limiting method thereof and electronic equipment

Technical Field

The application relates to the technical field of audio power amplification, in particular to an audio power amplification circuit, a power limiting method thereof and electronic equipment.

Background

The high-power audio power amplifier has the characteristic of high output power and is widely applied to medium and high power sound equipment products. Because the output power is larger, higher requirements are required for the loudspeaker, and the loudspeaker can be damaged if the output power is not limited. For medium and small power sound products in the market, a high-power audio power amplifier chip is often used inside the sound products, a typical high-power audio power amplifier chip is a 30W/8 omega audio power amplifier chip outputting 1% THD (harmonic distortion rate), and when the high-power audio power amplifier chip is applied to a 15W or 10W sound product, the output power of the audio power amplifier chip needs to be limited.

In order to prevent the loudspeaker from being burnt out, the high-power audio power amplifier chip on the market at present adopts a mode of directly limiting output power, however, the generally limited power is relatively fixed and cannot be adjusted, so that the application of the audio power amplifier chip is limited, and more product applications cannot be met.

Meanwhile, a full-wave modulation mode and a half-wave modulation mode often exist in the audio power amplifier, the full-wave modulation mode is that the output duty ratio is 50% in a static state, and the half-wave modulation mode can reduce the power consumption of the power amplifier by changing the duty ratio of the output waveform.

In the prior art, under a half-wave modulation mode, the output power cannot be accurately adjusted.

Disclosure of Invention

In view of this, the present application provides an audio power amplifier circuit, a power limiting method thereof, and an electronic device, so as to solve the problem that the limited power of the existing audio power amplifier chip cannot be flexibly adjusted.

The application provides an audio power amplifier circuit includes: the audio amplification module comprises an integral amplification unit, a signal modulation unit and a half-wave modulation mode detection unit; the half-wave modulation mode detection unit is connected between the output end of the integral amplification unit and the signal modulation unit, and is used for providing a half-wave modulation common-mode voltage VCM2 for the integral amplification unit according to the output signal of the integral amplification unit and inputting the output signal of the integral amplification unit to the signal modulation unit, so that the audio amplification module works in a half-wave modulation mode; the signal modulation unit is used for modulating the output signal of the integral amplification unit through a modulation wave and outputting a pulse width modulation signal; the power limiting module is connected between the output end and the input end of the integral amplifying unit of the audio amplifying module and used for comparing the output voltage of the output end of the integral amplifying unit with a threshold voltage and adjusting the input current of the input end of the integral amplifying unit according to a comparison result so as to limit the output voltage of the integral amplifying unit within a preset amplitude range; the input end of the threshold voltage adjusting module is used for inputting a control signal, and the output end of the threshold voltage adjusting module is connected to the power limiting module and used for outputting the threshold voltage which is changed along with the control signal to the power limiting module.

Optionally, the half-wave modulation mode detecting unit is configured to compare the output signal of the integrating and amplifying unit with a first threshold VCM2_ L and a second threshold VCM2_ H, and adjust the half-wave modulation common-mode voltage VCM2 according to the comparison result, and includes: when the amplitude of the output signal is within VCM2_ L-VCM 2_ H, the half-wave modulation common-mode voltage VCM2 is a fixed value; when the amplitude of the output signal is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value and gradually decreases the half-wave modulated common mode voltage VCM2 as the lowest amplitude of the output signal decreases; wherein VCM2_ L < VCM2_ H.

Optionally, the fixed value is a common-mode reference voltage VCM, where VCM ═ VCM2_ L + VCM2_ H)/2; the modulation signal is a triangular wave, the amplitude is PWM _ L-PWM _ H, VCM > (PWM _ L + PWM _ H)/2, and VCM2_ H is not less than PWM _ H.

Optionally, the threshold voltage adjusting module includes: and the first input end of the inverting amplifying unit is used for inputting the control signal, the second input end of the inverting amplifying unit is used for inputting a reference voltage, the output end of the inverting amplifying unit is used as a threshold voltage output end, a threshold voltage is output to the power limiting module, and the threshold voltage is changed along with the control signal.

Optionally, the threshold voltage adjusting module further includes: and the reference unit is used for outputting corresponding reference voltage to the inverting amplification unit according to the magnitude of the output signal of the integral amplification unit of the audio power amplifier circuit.

Optionally, the reference unit is configured to generate at least two sub-reference voltages respectively corresponding to different amplitude ranges of the output signal, and select one of the sub-reference voltages as a reference voltage to be output to the inverting amplification unit according to a magnitude of a current output signal.

Optionally, the reference unit includes a reference voltage generating circuit, and the reference voltage generating circuit includes a constant current unit, a mirror image unit, and an output unit; the constant current unit is used for generating a constant current, the mirror image unit is used for outputting the constant current mirror image to the output unit, and the output unit is used for converting the constant current into at least one sub-reference voltage and outputting the sub-reference voltage.

Optionally, the threshold voltage adjustment module further includes a reference voltage selection unit, where the reference voltage selection unit is connected to the reference voltage generation circuit, and is configured to select a corresponding sub-reference voltage according to a dynamic detection control signal corresponding to the magnitude of the output signal of the integral amplification unit, and output the sub-reference voltage to the inverting amplification unit.

Optionally, the sub-reference voltage output terminals of the reference voltage generating circuit are respectively connected to the reference voltage output terminal through a switch; the reference voltage selection unit comprises a first AND gate, a second AND gate, a first inverter and a control end, and the control end is used for inputting the dynamic detection control signal; one input end of the first AND gate is used for inputting a mode control signal, and the other input end of the first AND gate is connected to the control end; one input end of the second AND gate is used for inputting a mode control signal, the other input end of the second AND gate is connected to the output end of the first phase inverter, and the input end of the first phase inverter is connected to the control end.

Optionally, the threshold voltage adjusting module further includes: and the dynamic detection unit is used for detecting the amplitude range of the output signal of the integral amplification unit and outputting a dynamic detection control signal corresponding to the amplitude range of the output signal.

Optionally, the dynamic detection unit includes: the dynamic detection circuit comprises a comparator and a latch circuit, wherein two positive input ends of the comparator are respectively used for inputting two output signals of the integral amplification unit, a negative input end of the comparator is used for inputting a first threshold value, an output end of the comparator is connected to the latch circuit, the dynamic detection control signal is output by the circuit, the latch circuit outputs a dynamic detection control signal which is opposite to the output signal of the comparator, and the dynamic detection control signal is latched in a high-level output state when the dynamic detection control signal is at a high level.

Optionally, the latch circuit includes: a flip-flop, a transistor MP1, a transistor MP2, a transistor MP3, a transistor MN1, a transistor MN2, and a second inverter; one input end of the trigger is connected to the output end of the comparator, and the non-inverting output end of the trigger is connected to the grid of the transistor MP 1; the source electrode of the transistor MP1, the source electrode of the transistor MP2 and the source electrode of the transistor MP3 are all connected to a power supply voltage; the drain of the transistor MP1, the drain of the transistor MP2, the drain of the transistor MN1, the gate of the transistor MP3, and the gate of the transistor MN2 are electrically connected to each other; the gate of the transistor MP2, the drain of the transistor MP3, the drain of the transistor MN2, the gate of the transistor MN1, and the input terminal of the second inverter are electrically connected to each other, and the dynamic state detection control signal is output from the second inverter.

Optionally, the power limiting module is configured to adjust the input current when one of the two output voltages of the integrating and amplifying unit is lower than the threshold voltage.

The present application further provides a power limiting method for an audio power amplifier circuit, where the audio power amplifier circuit includes an integral amplifying unit, including: providing a half-wave modulation common-mode voltage VCM2 to the integral amplification unit according to the output signal of the integral amplification unit, so that the audio power amplifier circuit works in a half-wave modulation mode; comparing the output voltage of the output end of the integral amplification unit with a threshold voltage, wherein the threshold voltage is changed along with a control signal; according to the comparison result, the input current of the input end of the integral amplification unit is adjusted so as to limit the output voltage of the integral amplification unit within a preset amplitude range; and modulating the output signal by a modulation signal to output a half-wave modulated pulse width modulation signal.

Optionally, the method for providing the half-wave modulated common-mode voltage VCM2 to the integrating and amplifying unit according to the output signal of the integrating and amplifying unit includes: comparing the output signal of the integrating amplifying unit with a first threshold VCM2_ L and a second threshold VCM2_ H; when the amplitude of the output signal is within VCM2_ L-VCM 2_ H, the half-wave modulation common-mode voltage VCM2 is a fixed value; when the output signal amplitude is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value and gradually decreases the half-wave modulated common mode voltage VCM2 as the signal amplitude decreases.

Optionally, the fixed value is a common-mode reference voltage VCM, where VCM ═ VCM2_ L + VCM2_ H)/2; the modulation signal is a triangular wave, the amplitude is PWM _ L-PWM _ H, and VCM > (PWM _ L + PWM _ H)/2; VCM2_ H is greater than or equal to PWM _ H.

Optionally, when one of the pair of differential signals output by the integrating and amplifying unit is lower than the threshold voltage, the input current of the integrating and amplifying unit is adjusted to adjust the amplitude of the output voltage.

Optionally, the threshold voltage is also in a linear relationship with the reference voltage, and the output signals with different amplitude ranges correspond to different reference voltages.

Optionally, the method includes: adjusting the threshold voltage by adjusting at least one of the control signal, a correlation coefficient between the threshold voltage and the control signal, and a correlation coefficient between the threshold voltage and the reference voltage.

Optionally, the method for adjusting the input current of the input end of the integrating and amplifying unit includes: and converting the difference value of the output voltage of the output end of the integral amplification unit and the threshold voltage into output current, and outputting the output current to the input end of the integral amplification unit so as to realize the adjustment of the input current.

The application also provides an electronic device comprising the audio power amplifier circuit.

The audio amplifying circuit can output the threshold voltage which changes along with the input control signal through the threshold voltage adjusting module in the half-wave modulation mode, so that the value of the threshold voltage can be adjusted as required, and the output power of the audio amplifying circuit in the half-wave modulation mode is dynamically limited.

Furthermore, the threshold voltage adjusting module further comprises a reference unit for outputting a reference voltage, and the threshold voltage further corresponds to the magnitude of the input signal, so that the output power can be correspondingly limited for the input signals in different ranges, and the adaptability and flexibility of the circuit working state are higher.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an audio power amplifier circuit according to an embodiment of the present application;

fig. 2 is a schematic diagram illustrating a duty ratio principle of a half-wave modulation mode of an audio power amplifier circuit according to an embodiment of the present application;

FIG. 3a is a schematic waveform diagram of an audio driving signal output by the audio power amplifier circuit in a full-wave modulation mode of the audio power amplifier circuit;

FIG. 3b is a schematic waveform diagram of the audio driving signal outputted by the audio power amplifying circuit in the half-wave modulation mode of the audio power amplifying circuit;

FIG. 4 is a schematic diagram of power limiting of an audio power amplifier circuit according to an embodiment of the present application;

fig. 5 is a schematic structural diagram of a threshold voltage adjustment module of an audio power amplifier circuit according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of a dynamic detection unit of a threshold voltage adjustment module of an audio power amplifier circuit according to an embodiment of the present application;

fig. 7 is a schematic diagram illustrating a dynamic detection principle of a dynamic detection unit of an audio power amplifier circuit according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of a reference voltage generating circuit of an audio power amplifier circuit according to an embodiment of the present application;

fig. 9 is a schematic flowchart of an audio power amplifier output power limiting method according to an embodiment of the present application.

Detailed Description

As described in the background art, the power limit of the audio power amplifier resistor in the prior art is usually a fixed value, and cannot be adjusted according to different application scenarios. Even if some audio power amplifier chips capable of adjusting and limiting the output power exist, an accurate reference voltage is often required to be provided externally, so that the accurate adjustment of the output power is generally difficult to realize.

Especially in a half-wave modulation mode, the THD is often sacrificed to reduce the power consumption, and at present, in the half-wave modulation mode, it is difficult to accurately limit the output power to be arbitrarily adjustable, especially in a wide power supply range, the output power range is large, and it is difficult to effectively control the output power to be arbitrarily adjustable.

The inventor provides a novel audio power amplifier circuit and a power limiting method thereof, which can meet the requirement of a half-wave modulation mode, adjust the output power of the audio power amplifier circuit within a larger voltage power supply range to meet the requirement of half-wave modulation within a wide power supply voltage range, and have higher flexibility.

The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The following embodiments and their technical features may be combined with each other without conflict.

Fig. 1 is a schematic structural diagram of an audio power amplifier circuit according to an embodiment of the present invention.

In this embodiment, the audio power amplifier circuit includes: the audio power amplifier comprises an audio power amplifier module 110, a power limiting module 120 and a threshold voltage adjusting module 130.

The audio power amplifier module 110 includes an integral amplifying unit 111, a signal modulating unit 112, a driving output unit 113, and a half-wave modulation mode detecting unit 114.

The integrating and amplifying unit 111 includes a two-stage integrating amplifier AMP2 for integrating and amplifying the input signal to output signals A2VON and A2 VOP. In this embodiment, the integrating and amplifying unit 111 further includes a first-stage integrating amplifier AMP 1. The pair of differential signals INP and INN are respectively coupled to the first-stage integrating amplifier AMP1 through a capacitor Cin and a resistor Rin, and output signals A2VON and A2VOP after being subjected to full differential amplification sequentially by the first-stage integrating amplifier AMP1 and the second-stage integrating amplifier AMP2, the differential signals INP and INN are converted into current signals A1VIP and A1VIN through the capacitor Cin and the resistor Rin and input to the AMP1, voltage signals A1VON and A1VOP are output through AMP1 integral amplification operation, the A1VON and A1VOP are converted into current signals input to the AMP2 through resistors, the signals A2VON and A2VOP are output after being subjected to integral amplification by the AMP2, and the A2VON and A2VOP are voltage signals.

The half-wave modulation mode detection unit 114 is connected between the output end of the integrating amplification unit 11 and the signal modulation unit, and is configured to input the output signals A2VON and A2VOP of the integrating amplification unit to the signal modulation unit 112, and provide a half-wave modulation common-mode voltage VCM2 to the integrating amplification unit 111 according to the output signal of the integrating amplification unit 111, so that the audio amplification module 110 operates in a half-wave modulation mode. In this embodiment, the half-wave modulated common mode voltage VCM2 is provided to the second integrating amplifier AMP2 such that the output signals A2VON and A2VOP are symmetric about the half-wave modulated common mode voltage VCM 2.

After the output signals A2VON and A2VOP pass through the half-wave modulation pattern detection unit 114, they pass through the comparators CMP1 and CMP2 in the signal modulation unit 112 and a modulation signal S, respectively_RAMPModulating to generate pulse width modulation signal, and outputting driving signals VOP and VON via the driving output unit 113, wherein the modulation signal S_RAMPTypically a waveform having periodic rising and falling edges, such as a triangular wave or a sawtooth wave. The half-wave modulation common mode voltage VCM2 of the output signals A2VON and A2VOP causes the signal modulation unit 112 to half-wave modulate the output signals A2VON and A2VOP of the second-stage integrating amplifier AMP 2.

With said modulated signal S_RAMPFor triangular wave example, the signal amplitude is PWM _ VL &PWM _ VH, VCM2 > (PWM _ VL + PWM _ VH)/2, in which case, the signal modulation unit 112 performs half-wave modulation, specifically including: in a static working state (namely when no input signal exists), the driving signals VOP and VON are both square wave signals with the duty ratio of less than 50%; when the input signal is large, the VOP or VON has no signal, and only a single-side signal is output.

The common-mode voltage of the first-stage integrating amplifier AMP1 is VCM1, VCM1 is less than VCM2,

in this embodiment, the signal modulation unit 112 is mainly caused to perform half-wave modulation on the output signal of the integrating and amplifying unit 111 by the size of the half-wave modulation common-mode signal VCM2, and controls the duty ratio of the half-wave modulation.

Further, the half-wave modulation common-mode voltage VCM2 may be a fixed value, or may be a dynamic value that varies with the magnitude of the output signal of the integrating and amplifying unit 111. The half-wave modulation mode detection unit 114 performs feedback adjustment on the half-wave modulation common-mode voltage VCM2 according to the amplitude ranges of the output signals A2VON and A2VOP, and specifically, the half-wave modulation mode detection unit 114 is configured to compare the output signal of the integrating and amplifying unit 111 with a first threshold VCM2_ L and a second threshold VCM2_ H, and adjust the output half-wave modulation common-mode voltage VCM2 according to the comparison result, and includes: when the amplitude of the input signal is within VCM2_ L-VCM 2_ H, the half-wave modulation common-mode voltage VCM2 is a fixed value; when the amplitude of the output signal is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value, and gradually decreases the half-wave modulated common mode voltage VCM2 as the amplitude of the signal decreases. By lowering the half-wave modulation common mode voltage VCM2 when the signal is large, the lowest amplitude of the signals of the output voltages A2VON and A2VOP is shifted down, so that the truncation distortion can be reduced. The fixed value may be a common-mode reference voltage VCM on the basis of which the VCM2 is adjusted.

Fig. 2 is a schematic diagram of duty ratio in half-wave modulation mode.

Taking the static operating state as an example, when the AMP2 outputs signals A2VON and A2VOP both greater than VCM2_ L, VCM2 is fixed at VCM. For the static working condition, the duty ratio of the power amplifier output OUTP and OUTN is less than 50%, and the THD and power consumption influence is comprehensively considered, and the duty ratio is generally set to be about 10% to 30%. The difference between VCM2_ H and the maximum value PWM _ VH of the triangular wave is delta V', VCM2_ H is slightly larger than PWM _ VH, and VCM2_ H can be adjusted according to the requirement of THD. In some cases, Δ V' may be as low as 0.

It should be noted that the circuit modules other than the driving output unit 113, such as the integrating and amplifying unit 111 and the signal modulating unit 112, are usually operated in the VDD domain, that is, the low-voltage domain power supply VDD generated by a low dropout regulator (LDO) (not shown) inside the chip is used for supplying power, and VDD is usually about 4V to 6V. The driving output unit 113 mainly works in a PVDD domain, that is, a power supply usually adopts a high-voltage domain power supply PVDD input from the outside of a chip, and the minimum voltage can be 4V, the maximum voltage can be 30V, and usually about 20V-30V; in some cases, some devices or circuits (e.g., circuit units connected to VDD domain) in the driving output unit 113 also operate on VDD power, and can be connected to circuits operating on PVDD through a level shifter.

In this embodiment, PWM _ VH is 0.5VDD +0.056PVDD, and PWM _ L is 0.5VDD-0.056 PVDD.

Referring to fig. 3a and 3b, schematic diagrams of output duty ratios of a full-wave modulation mode and a half-wave modulation mode according to an embodiment of the invention are shown.

Fig. 3a shows a full-wave modulation mode, in a static operating state, an input signal is 0, no output signal is present, and OUTP and OUTN are square wave signals with a duty ratio of 50%; and under the state of having input signals, the two output ends both have signal outputs.

Fig. 3b shows that in the half-wave modulation mode, in the static operating state, the input signal is 0, and OUTP and OUTN are square wave signals with a duty ratio lower than 50%; when a signal is input and the amplitude of the signal is large, the situation that one end of the signal has a square wave and the other end of the signal has no square wave can occur. Because the audio power amplifier circuit is applied usually, the LC filter is added at both ends of the output end. Compared with the full-wave modulation mode, the duty ratios of signals on two sides of the output end are the same and are less than 50% in the static working state of the half-wave modulation mode, the whole charging time is shortened, the average current is small, and the power consumption is reduced; when a signal is input, if one side of the output end has no signal and the other side of the output end is a square wave with a narrow pulse width, only the LC filter at one end is charged, so that the overall average current is small, and the power consumption is reduced.

With continued reference to fig. 1, the integrating and amplifying unit 111 includes a primary integrating amplifier AMP1 and a secondary integrating amplifier AMP2 for converting and outputting a current signal into a voltage signal. The magnitudes of the output signals A2VON and A2VOP of the integrating and amplifying unit 111 determine the output power of the audio power amplifier module, and the magnitudes of the voltages of the output signals A2VON and A2VOP are determined by the input current at the input terminal of the first-stage integrating amplifier AMP1 of the integrating and amplifying unit 111, i.e., by the input current at the input terminal of the first-stage integrating amplifier AMP 1.

In this embodiment, a power limiting module 120 is connected between the output end and the input end of the integrating and amplifying unit 111, the power limiting module 120 is configured to adjust the amplitude of the input current at the input end of the integrating and amplifying unit 111 according to the output end signal of the integrating and amplifying unit 111, the integrating and amplifying unit 111 converts the input current into the output voltage through a first-stage integrating amplifier AMP1 and a second-stage amplifier AMP2, and the amplitude adjustment of the output voltage can be achieved by controlling the input current.

In this embodiment, the power limiting module 120 is configured to compare the output signals A2VON and A2VOP at the output end of the integrating and amplifying unit 111 with a threshold voltage VLIMIT, perform current amplitude adjustment on the input currents AIVIP and A1VIN at the input end of the integrating and amplifying unit 111 according to the comparison result, and limit the voltage magnitudes of the output signals A2VOP and A2VON of the AMP2 within a preset amplitude range after passing through the two-stage integrator, so as to adjust the output power. The amplitude range may be preset according to the limit requirement for output power.

Since the output signals A2VON and A2VOP at the output end of the integrating and amplifying unit 111 are a pair of differential signals symmetrical about the half-wave modulation common-mode voltage VCM2, and the VCM2 is adjusted with reference to the common-mode reference voltage VCM, the threshold voltage VLIMT can be set smaller than VCM, and the output signals A2VON and A2VOP are respectively compared with the threshold voltage VLIMIT.

Fig. 4 is a schematic diagram illustrating a power limitation according to an embodiment of the invention.

The signal 1 is an original signal, the signal 2 is a signal subjected to power limitation, the lowest amplitude of the signal is limited above VLIMIT, and the value of VLIMIT can be adjusted by adjusting the control signal PLIMIT, so that the signal amplitude range of the signal 2 subjected to power limitation is adjusted, and the output power is adjusted.

When one of the voltages of A2VON and A2VOP is lower than VLIMIT, the power limiting module 120 starts to operate, draw a current to the input terminal of the first-stage integrating amplifier AMP1, and reduce the magnitude of the current input to the input terminal of the first-stage integrating amplifier AMP1, so as to limit the signal magnitudes of the output signals A2VON and A2VOP at the output terminal of the second-stage integrating amplifier AMP2, and the voltage ranges of the output signals A2VON and A2VOP can be limited within a range from VLIMIT to (2 × VCM-VLIMIT), so as to limit the output power; when both of the output signals A2VON and A2VOP at the output of the second-stage integrating amplifier AMP2 are greater than the threshold voltage VLIMIT, the power limiting module 120 is disabled and does not draw current at the input of the first-stage integrating amplifier AMP 1.

Specifically, the power limiting module 120 includes a transconductance amplifying unit, configured to convert a difference between an output voltage at an output end of the integrating and amplifying unit 111 and the threshold voltage VLIMIT into an output current, and output the output current to an input end of the integrating and amplifying unit 111, so as to adjust an input current at the input end of the integrating and amplifying unit 111. For example, when the output signal A2VON is smaller than the threshold voltage VLIMIT, the voltage difference between A2VON and VLIMIT is converted into an output current, and the output current is output to the two input terminals of the integrating and amplifying unit 111. According to the current direction of the output current, the extraction or the supplement of the input current at the input end of the integral amplification unit 111 is realized. The transconductance amplifying unit comprises a transconductance amplifier and a matched related circuit structure, and the transconductance amplifier can convert input differential voltage into output current.

The threshold voltage adjusting module 130 is connected to the power limiting module 120, and configured to output the threshold voltage VLIMIT, which varies with the control signal PLIMIT, to the power limiting module 120.

Under the condition that the threshold voltage VLIMIT is different, the amplitude ranges of the output signals A2VON and A2VOP are changed, so that under different conditions, the limit degree of the output power can be adjusted by adjusting the output threshold voltage VLIMIT.

In this embodiment, the threshold voltage adjusting module 130 is configured to output the threshold voltage VLIMIT in negative correlation with the control signal PLIMIT, that is, the larger the control signal PLIMIT is, the smaller the output threshold voltage VLIMIT is under other conditions. In other embodiments, the threshold voltage VLIMIT and the control signal PLIMIT may also be in a positive correlation. The threshold voltage VLIMIT can be adjusted without changing the control signal PLIMIT by adjusting a correlation coefficient between the control signal PLIMIT and the threshold voltage VLIMIT.

The audio amplification circuit can output the threshold voltage VLIMIT which is adjustable along with the control signal PLIMIT through the threshold voltage adjusting module, so that the value of the threshold voltage VLIMT can be adjusted under different conditions, and the output power of the audio amplification circuit is dynamically limited.

Fig. 5 is a schematic structural diagram of the threshold voltage adjustment module 130 according to an embodiment of the invention.

In this embodiment, the threshold voltage adjusting module 130 includes an inverting amplifying unit 131 and a reference unit 132.

The reference unit 132 is configured to output a corresponding reference voltage VCOM according to a magnitude of an output signal of the integrating and amplifying unit 111; the inverting amplifying unit 131 has a first input terminal for inputting the control signal PLIMIT, a second input terminal for inputting the reference voltage VCOM, and an output terminal of the inverting amplifying unit 131 serving as an output terminal of the threshold voltage VLIMIT.

In this embodiment, the inverting amplifying unit 131 includes an amplifier AMP12, the control signal PLIMIT is coupled to the negative input terminal of the amplifier AMP12 through a resistor RS1, the positive input terminal of the amplifier AMP12 is used for inputting the divided signal of the reference voltage VCOM, and a resistor RF1 is connected between the output terminal and the negative input terminal of the inverting amplifier AMP 12. In this embodiment, a buffer AMP11 is further connected between the control signal PLIMIT and the resistor RS1, and is used for stabilizing the control signal PLIMIT and increasing the driving force of the control signal PLIMIT. The buffer AMP11 includes an amplifier having an output terminal short-circuited to a negative input terminal, and a positive input terminal of the buffer AMP11 receives the control signal PLIMIT. In other embodiments, the buffer AMP11 may be omitted, or other types of devices may be employed for the buffer AMP 11.

An output terminal of the reference unit 132 is connected to a second input terminal of the inverting amplifying unit 131, and is used for inputting a reference voltage VCOM to the inverting amplifying unit 131. Specifically, the inverting amplifying unit 131 includes an amplifier AMP12, and an output terminal of the amplifier AMP12 is an output terminal of the inverting amplifying unit 131. A voltage dividing circuit is connected between the output terminal of the reference unit 132 and the positive input terminal of the amplifier AMP12, the voltage dividing circuit includes resistors R0, RF2 and RS2 connected in series between the output terminal of the amplifier AMP12 and the ground, one end of the resistor R0 is connected to the output terminal of the amplifier AMP12, the other end of the resistor R0 is connected to one end of the resistor RF2, the other end of the resistor RF2 is connected to the resistor RS2, and the other end of the resistor RS2 is grounded. The output terminal of the reference unit 132 is connected to the connection terminal of the resistors R0 and RF2, and the connection terminal of the resistors RF2 and RS2 is connected to the positive input terminal of the amplifier AMP 12.

The two input terminals of the inverting amplifier AMP12 have a virtual short characteristic and are equal in voltage. It can be calculated that:

obtaining:

the threshold voltage VLIMIT is inversely proportional to the control signal PLIMIT, and the correlation coefficient is

The threshold voltage VLIMIT is also related to the reference voltage VCOM with a correlation coefficient therebetween

The adjustment of the threshold voltage VLIMIT may be achieved by adjusting any one or several of the control signal PLIMIT, the correlation coefficient between the threshold voltage VLIMIT and the control signal PLIMIT, and the correlation coefficient between the threshold voltage VLIMIT and the reference voltage VCOM.

In this embodiment, RS 1-RS 2-RS and RF 1-RF 2-RF.

Thus VLIMIT is:

in this case, if PLIMIT is large, VLIMIT is too small, and the voltage fluctuation width Δ VS of the output signals A2VON and A2VOP becomes large at 2 × (VCM — VLIMIT), which may cause output power not to be sufficiently limited, and may still damage the horn. Therefore, the value of PLIMIT needs to be set properly.

In this embodiment, the reference unit 132 is configured to generate two sub-reference voltages VREFA and VREFB corresponding to different amplitude ranges of A2VON and A2VOP, VREFA > VREFB, and select one of the sub-reference voltages as the reference voltage VCOM to be output to the inverting amplifying unit 131 according to the current signal magnitude.

In the case where the amplitude range of the input signal is small, i.e., the amplitude ranges of A2VON and A2VOP are small, the corresponding reference voltage VCOM is equal to VREFB,

in case two, when the amplitude range of the input signal is large, i.e., the amplitude ranges of A2VON and A2VOP are large, the corresponding reference voltage VCOM is equal to VREFA,

VLIMIT2 > VLIMIT1, so in case two, the degree of power limitation is greater.

Specifically, the reference cell 132 includes a reference voltage generating circuit 1321, two output terminals of the reference voltage generating circuit 1321 are respectively used for outputting the sub-reference voltage VREFA and the sub-reference voltage VREFB, and the two output terminals are respectively connected to a buffer AMP13 through switches, and the stable reference voltage VCOM is output through the buffer AMP 13.

The threshold voltage adjusting module 130 further includes a reference voltage selecting unit 133, where the reference voltage selecting unit 133 is connected to the reference voltage generating circuit 1321, and is configured to select a corresponding sub-reference voltage to output to the inverting amplifying unit 131 according to a dynamic detection control signal corresponding to the magnitudes of the output signals A2VON and A2VOP of the integrating amplifying unit. The dynamic detection control signal comprises a first control signal CLK1 and a second control signal CLK2, and controls the on-off state of the switch through the level of CLK1 and the level of CLK2, so that a proper reference voltage is output. In one embodiment, when CKL1 is high and CLK2 is low, VCOM is VREFA; when CKL2 is high and CLK1 is low, VCOM is VREFB.

In this embodiment, the reference voltage selection unit 133 includes a first AND gate AND1, a second AND gate AND2, a first inverter INV1, AND a control terminal for inputting the dynamic detection control signal LLM _ SEL; one input end of the first AND gate AND1 is used for inputting a mode control signal CLK _ LLM, AND the other input end is connected to the control end; one input end of the second AND gate AND2 is used for inputting a mode control signal CLK _ LLM, the other input end is connected to the output end of the first inverter INV1, AND the input end of the first inverter INV1 is connected to the control end; the first AND gate AND1 outputs a first control signal CLK1, AND the second AND gate AND2 outputs a second control signal CLK 2. When the dynamic detection control signal LLM _ SEL is low, the first control signal CLK1 is low, the second control signal CLK2 is high, and VCOM is VREFB; when the dynamic detection control signal LLM _ SEL is high, the first control signal CLK1 is high, the second control signal CLK2 is low, and VCOM is VREFA.

Referring to fig. 6, the threshold voltage adjusting module 130 further includes a dynamic detection unit 134 for detecting an amplitude range of the output signal of the integrating and amplifying unit 111 and outputting a dynamic detection control signal LLM _ SEL corresponding to the amplitude range of the output signal.

The dynamic detection unit 134 includes: a comparator CMP3 having two positive input terminals for inputting the two output signals A2VOP and A2VON of the integrating and amplifying unit 111, respectively, a negative input terminal for inputting the first threshold VCM2_ L, the comparator CMP3 having an output terminal connected to the latch circuit, the dynamic detection control signal LLM _ SEL being output by the latch circuit, the latch circuit outputting the dynamic detection control signal LLM _ SEL in phase opposition to the output signal of the comparator CMP3, and latching in a high level output state when the dynamic detection control signal LLM _ SEL is at a high level.

The latch circuit includes: a flip-flop 1341, a transistor MP1, a transistor MP2, a transistor MP3, a transistor MN1, a transistor MN2, and a second inverter INV 2; an input end of the flip-flop 1341 is connected to the output end of the comparator CMP3, and a non-inverting output end of the flip-flop 1341 is connected to the gate of the transistor MP 1; the source of the transistor MP1 is connected to the source of the transistor MP2, the drain of the transistor MP1 is connected to the drain of the transistor MP2, the drain of the transistor MP2 is connected with the drain of the transistor MN1, and the drain of the transistor MP3 is connected with the drain of the transistor MN 2; the gate of the transistor MP2 is connected to the drain of the transistor MP3, the gate of the transistor MP3 is connected to the drain of the transistor MP2, the gate of the transistor MN1 is connected to the drain of the transistor MN2, and the gate of the transistor MN2 is connected to the drain of the transistor MN 1; drains of the transistor MP3 and the transistor MN2 are connected to an input terminal of the second inverter INV2, and the dynamic detection control signal is output from the second inverter INV 2. The transistors MP 1-MP 3 are PMOS transistors, the sources are connected to a low-voltage domain power supply VDD, the transistors MN1 and MN2 are NMOS transistors, and the sources are grounded.

In this embodiment, the dynamic detection unit 134 may further include a filter module, for example, in fig. 5, a filter circuit formed by a resistor R and a capacitor C is disposed at the positive input end of the comparator CMP3, the A2VOP and the A2VON are filtered and then compared with the first threshold VCM2_ L by the comparator CMP3, and the anti-spike pulser 1342 is further disposed between the output end of the comparator CMP3 and the latch circuit, so as to prevent the level of the output signal of the comparator CMP3 from being turned over due to signal disturbance.

In an embodiment of the present invention, the modulation signal S of the signal modulation unit 112 of the audio power amplifier module 110_RAMPHas signal amplitude of PWM _ VL-PWM _ VH, wherein PWM _ VL is a modulation signal S_RAMPPWM _ VH is the modulation signal S_RAMPThe highest value of the voltage. In the half-wave modulation mode, the phase of the signal is changed,

please refer to fig. 7, which is a schematic diagram of waveforms of signals under different conditions.

In this embodiment, the operating signal is divided into two cases: case one and case two.

In the case of small signal input, the minimum amplitudes of A2VOP and A2VON are both higher than VCM2_ L, the signal amplitudes are VCM2_ L to VCM2_ L, the output of comparator CMP3 is high, the gate voltage of MP1 is high, after passing through the respective transistors and second inverter INV2, the output LLM _ SEL is low, VCOM is VREFB is VCM, and VCM2 is VCM.

In case of large signal input, the maximum amplitudes of A2VON and A2VOP are clamped to VCM2_ H, and at this time, the half-wave modulation common-mode voltage VCM2 of AMP2 drops and VCM2 drops, the lowest amplitude of the signal is released downwards, and the waveform extends downwards; when the lowest amplitude is detected to be lower than VCM2_ L, the comparator CMP3 output is low, at which time the gate voltage of MP1 is low, the output LLM _ SEL is high, and latching is performed. VCOM — VREFA — PWM — VH.

In one embodiment, the signal S is modulated_RAMThe amplitude of the triangular wave is (0.5VDD-0.0556PVDD) - (0.5VDD +0.0556PVDD), namely PWM _ VL is 0.5VDD-0.0556PVDD, PWM _ VH is 0.5VDD +0.0556PVDD, 0.5VDD is less than VCM and less than 0.5VDD +0.0556 PVDD; in case one, the reference voltage VCOM is VREFB VCM; in case two, the reference voltage VCOM is VREFA — PWM _ VH is 0.5VDD +0.0556 PVDD.

In other embodiments, signal S is modulated with_RAMThe common mode reference voltage VCM and the reference voltage VCOM at different signal amplitudes are changed accordingly.

Fig. 2 is a schematic diagram illustrating a power limitation principle according to an embodiment of the invention.

Taking the power limit under harmonic distortion condition of 1% THD as an example, modulate signal S_RAMPThe amplitude range of the signal of (a) is Δ V, and the amplitude range of the output signals A2VON and A2VOP of the two-stage integrating amplifier AMP2 varies by Δ VS.

From the output end signals A2VON and A2VOP of the two-stage integral amplifier AMP2 to the audio drive signal OUTP/OUTN at the output end of the whole audio power amplifier circuit

Thus, when the differential driving signals OUTP and OUTN are output, the peak voltage VP of the signal OUTP-OUTN after being converted into a single-ended output is:

the peak voltage VP determines the maximum output power of the audio power amplifier circuit at 1% THD.

In the small signal state, VCM2 is VCM, and VCOM is VREFB is VCM.

The triangular wave has a signal range VV-PWM _ VL-2 × 0.0556 × PVDD. The amplification from the output of the two-stage integrating amplifier AMP2 to the output of the output stage is

Therefore, the temperature of the molten metal is controlled,

according to the above-mentioned formula,

suppose that

Fixed, then the single-ended peak value VP of the output signal can be adjusted by adjusting the value of PLIMIT, thereby achieving accurate control of the output power.

In other embodiments, VREFB may be set to different voltage values in case of one, so as to limit different power levels, so as to adjust the output power accurately when the output signal of AMP2 is small, i.e. the input signal of the audio amplification module is small.

In case two, the lowest amplitude of the output signals A2VON and A2VOP of the integrating and amplifying unit is smaller than VCM2_ L, VCOM is VREFA is PWM _ VH, and the amplitude Δ V of the output signal is limited to be smaller than VCM2_ L

Single end peak value

Also, suppose

Fixed, then the value of PLIMIT may be adjusted,and adjusting the single-ended peak value VP of the output signal, thereby realizing accurate control of the output power.

In other embodiments, the output power in the two modes can be consistent by adjusting the RF/RS value and the PLIMIT value under different conditions, so as to meet the user's requirement for fixed output power.

Fig. 8 is a schematic circuit diagram of a reference voltage generating circuit 1321 according to an embodiment of the invention.

The reference voltage generation circuit 1321 includes a constant current unit 701, a mirror unit 702, and an output unit 703. The constant current unit 701 is configured to generate a constant current IB, the mirror image unit 702 is configured to mirror and output the constant current IB to the output unit 703, and the output unit 703 uses the common-mode voltage VCM1 as a clamping voltage to convert the constant current IB into a plurality of voltage signals related to the clamping voltage and output the voltage signals. VCM1 in this example is 0.5 VDD.

In this embodiment, the reference voltage generation circuit 1321 is not only used for generating the sub-reference voltages VREFA and VREFB, but also used for generating the modulation signal S_RAMPPWM _ VH and PWM _ VL, the first threshold VCM2_ L, the second threshold VCM2_ H, and the common mode reference voltage VCM input to the half-wave modulation mode detection unit 114.

The constant current unit 701 includes a resistor R11 and a resistor R12 connected in series between the high voltage domain power source PVDD and ground, an amplifier AMP21, a transistor MP0, and a resistor R13.

The resistor R11 has one end connected to the high-voltage domain power supply PVDD and the other end connected to the resistor R12, the other end of the resistor R12 is grounded, a connection end of the resistor R12 and the resistor R11 is connected to one input end of the amplifier AMP21, an output end of the amplifier AMP12 is connected to a gate of the transistor MP0, and a drain of the transistor MP0 is grounded via the resistor R13 and is also connected to the other input end of the amplifier AMP 12. The transistor MP0 is a PMOS transistor.

The high voltage domain power PVDD provides a first input voltage VIN to the negative input terminal of the amplifier AMP21 after being divided by R11 and R12,

due to the imaginary short effect between the two input terminals of the amplifier AMP21, the second input voltage VIP ═ VIN at the positive input terminal of AMP21 is caused. One end of the resistor R13 is fixed to VIP voltage, so constant current flows

The mirror unit 702 comprises transistors MP11 and MP12 in mirror connection, wherein MP11 and MP12 are both PMOS transistors, MP11 has a source connected to the low voltage domain power VDD, and a drain connected to the source of MP 0. In this embodiment, MP11 and MP12 are the same size, and therefore, the same current IB flows in MP12 as in MP 11. The drain of MP12 is connected to an output unit for providing a constant current IB to the output unit 703.

The output unit 703 comprises a transistor MN0, resistors R16 and R17 which are sequentially connected in series between the drain of the transistor MP2 and the drain of the transistor MN0, an amplifier AMP22, a resistor R14 and a resistor R15. The transistor MN0 is an NMOS transistor.

The resistor R14 and the resistor R15 are connected in series between the low-voltage domain power supply VDD and the ground, a connection end between the resistor R14 and the resistor R15 is connected to a negative input end of the amplifier AMP22, a positive input end of the amplifier AMP22 is connected to a connection end of the resistor R16 and the resistor R17, and an output end of the amplifier AMP22 is connected to a gate of the transistor MN0 to control the switching state of the transistor MN 0.

The low-voltage domain power supply VDD divides the common-mode voltage VCM1 of the AMP1 through R14 and R15, and inputs the voltage VCM1 to the negative input terminal of the amplifier AMP22,

in one embodiment, R14 is set to R15 with the same resistance and VCM1 is set to 0.5 VDD.

Voltages are output from ends of the resistors R164, R163, R162, R161, and R17 connected in series as VCM2_ H, PWM _ VH, VCM, and VCM2_ L, PWM _ VL, respectively; where VREFB is VCM, PWM _ VH also serves as the reference voltage VREFA.

Wherein the content of the first and second substances,

PWM_VH＝VCM1+IB*(R161+R162+R163)；

PWM_VL＝VCM1-IB*R17；

VCM2_L＝VCM1+IB*R161；

VCM2_H＝VCM1+IB*(R161+R162+R163+R164)；

VCM＝VCM1+IB*(R161+R162)；

in the embodiment of the present invention, the value of each output signal can be adjusted by adjusting the resistance value of each resistor in the output unit 703.

In the above embodiment, the audio amplifier circuit can output the threshold voltage VLIMIT adjustable along with the control signal PLIMIT through the threshold voltage adjusting module, so that the value of the threshold voltage VLIMIT can be adjusted as needed, and the output power of the audio amplifier circuit is dynamically limited.

Furthermore, the threshold voltage adjusting module further comprises a reference unit for outputting a reference voltage, and the threshold voltage is also related to the reference voltages corresponding to the magnitudes of the output signals of different integrating and amplifying units, so that the output power can be correspondingly limited according to different signal magnitudes, and the adaptability and flexibility of the circuit working state are higher.

The technical scheme of the invention also provides electronic equipment which comprises the audio power amplifier circuit in the embodiment. The electronic equipment can randomly adjust the output power of the audio power amplifier for input signals in a large range in a wide power supply voltage range in a low-power-consumption half-wave modulation mode, has high flexibility, can effectively protect a loudspeaker, and meets the requirements of the wide power supply voltage range and the large input signal range.

The embodiment of the invention also provides an output power limiting method of the audio power amplifier circuit.

Fig. 9 is a flowchart illustrating an output power limiting method according to an embodiment of the invention.

The method comprises the following steps:

step S801, providing a half-wave modulation common-mode voltage VCM2 to the integral amplification unit according to the output signal of the integral amplification unit, so that the audio power amplifier circuit works in a half-wave modulation mode.

In one embodiment, the method of providing a half-wave modulated common mode voltage VCM2 to the integrating amplification unit according to the output signal of the integrating amplification unit comprises: comparing the output signal of the integrating amplifying unit with a first threshold VCM2_ L and a second threshold VCM2_ H; when the amplitude of the input signal is within the range of VCM 2-L-VCM 2-H, controlling the half-wave modulation common-mode voltage VCM2 to be a fixed value; when the output signal amplitude is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value and gradually decreases the half-wave modulated common mode voltage VCM2 as the signal amplitude decreases.

Step S802, comparing the output signal of the output end of the integral amplifying unit with a threshold voltage, wherein the threshold voltage is changed along with the control signal.

In one embodiment, the threshold voltage is inversely related to the control signal, and the larger the control signal, the smaller the threshold voltage.

And step S803, according to the comparison result, adjusting the input current of the input end of the integral amplification unit, so as to limit the output voltage of the integral amplification unit within a preset amplitude range.

Specifically, when one of a pair of differential signals output by the integrating and amplifying unit is lower than the threshold voltage, the amplitude of the input current of the integrating and amplifying unit is adjusted; when the output signals are all larger than the threshold voltage, the input current is not adjusted, the output voltage is not limited, and therefore the amplitude of the output voltage is kept unchanged.

The method for adjusting the amplitude of the input current of the integral amplification unit comprises the following steps: and converting the difference value between the output voltage of the output end of the integral amplification unit and the threshold voltage into output current, outputting the output current to the input end of the integral amplification unit, and adjusting the input current of the integral amplification unit.

In some embodiments, the threshold voltage may be further related to, e.g., linearly related to, a reference voltage. The audio power amplifier circuit can work in a half-wave modulation mode, and different reference voltages are correspondingly generated under different output signal amplitude conditions. The threshold voltage is related to the reference voltage, so that the power limitation requirements under different working modes can be more flexibly adapted. The amplitude range of the output voltage may be preset as a limitation requirement on the output power range.

Since the threshold voltage limits the signal amplitude of the output voltage, the threshold voltage can be adjusted according to different conditions by adjusting the control signal, the correlation coefficient between the threshold voltage and the control signal, and any one or more of the correlation coefficients between the threshold voltage and the reference voltage, so that the adjustment of the output voltage amplitude of the integral amplification unit is realized, and further more flexible and accurate power limitation is realized.

And step S804, modulating the output signal by a modulating wave and outputting a half-wave modulated pulse width modulation signal.

In one embodiment, the modulation signal is a triangular wave with amplitude of PWM _ L-PWM _ H; VCM (VCM2_ L + VCM2_ H)/2, VCM2_ H is equal to PWM _ H, VCM2 > (PWM _ L + PWM _ H)/2.

The above-mentioned embodiments are only examples of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by the contents of the specification and the drawings, such as the combination of technical features between the embodiments and the direct or indirect application to other related technical fields, are also included in the scope of the present application.

Claims

1. An audio power amplifier circuit, comprising:

the audio amplification module comprises an integral amplification unit, a signal modulation unit and a half-wave modulation mode detection unit; the half-wave modulation mode detection unit is connected between the output end of the integral amplification unit and the signal modulation unit, and is used for providing a half-wave modulation common-mode voltage VCM2 for the integral amplification unit according to the output signal of the integral amplification unit and inputting the output signal of the integral amplification unit to the signal modulation unit, so that the audio amplification module works in a half-wave modulation mode; the signal modulation unit is used for modulating the output signal of the integral amplification unit through a modulation wave and outputting a pulse width modulation signal;

the power limiting module is connected between the output end and the input end of the integral amplifying unit of the audio amplifying module and used for comparing the output voltage of the output end of the integral amplifying unit with a threshold voltage and adjusting the input current of the input end of the integral amplifying unit according to a comparison result so as to limit the output voltage of the integral amplifying unit within a preset amplitude range;

the input end of the threshold voltage adjusting module is used for inputting a control signal, and the output end of the threshold voltage adjusting module is connected to the power limiting module and used for outputting the threshold voltage which is changed along with the control signal to the power limiting module.

2. The audio power amplifier circuit of claim 1, wherein the half-wave modulation mode detection unit is configured to compare the output signal of the integrating amplification unit with a first threshold VCM2_ L and a second threshold VCM2_ H, and adjust the half-wave modulation common-mode voltage VCM2 according to the comparison result, and comprises: when the amplitude of the output signal is within VCM2_ L-VCM 2_ H, the half-wave modulation common-mode voltage VCM2 is a fixed value; when the amplitude of the output signal is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value and gradually decreases the half-wave modulated common mode voltage VCM2 as the lowest amplitude of the output signal decreases; wherein VCM2_ L < VCM2_ H.

3. The audio power amplifier circuit of claim 2, wherein the fixed value is a common-mode reference voltage VCM, (VCM2_ L + VCM2_ H)/2; the modulation signal is a triangular wave, the amplitude is PWM _ L-PWM _ H, VCM > (PWM _ L + PWM _ H)/2, and VCM2_ H is not less than PWM _ H.

4. The audio power amplifier circuit of claim 1, wherein the threshold voltage adjusting module comprises: and the first input end of the inverting amplifying unit is used for inputting the control signal, the second input end of the inverting amplifying unit is used for inputting a reference voltage, the output end of the inverting amplifying unit is used as a threshold voltage output end, a threshold voltage is output to the power limiting module, and the threshold voltage is changed along with the control signal.

5. The audio power amplifier circuit of claim 4, wherein the threshold voltage adjustment module further comprises: and the reference unit is used for outputting corresponding reference voltage to the inverting amplification unit according to the magnitude of the output signal of the integral amplification unit of the audio power amplifier circuit.

6. The audio power amplifier circuit of claim 5, wherein the reference unit is configured to generate at least two sub-reference voltages respectively corresponding to different amplitude ranges of the output signal, and select one of the sub-reference voltages as the reference voltage to be output to the inverting amplification unit according to a magnitude of a current output signal.

7. The audio power amplifier circuit according to claim 6, wherein the reference unit comprises a reference voltage generating circuit, and the reference voltage generating circuit comprises a constant current unit, a mirror image unit and an output unit; the constant current unit is used for generating a constant current, the mirror image unit is used for outputting the constant current mirror image to the output unit, and the output unit is used for converting the constant current into at least one sub-reference voltage and outputting the sub-reference voltage.

8. The audio power amplifier circuit according to claim 7, wherein the threshold voltage adjustment module further comprises a reference voltage selection unit, and the reference voltage selection unit is connected to the reference voltage generation circuit and configured to select a corresponding sub-reference voltage to output to the inverting amplification unit according to a dynamic detection control signal corresponding to the magnitude of the output signal of the integrating amplification unit.

9. The audio power amplifier circuit according to claim 8, wherein the sub-reference voltage output terminals of the reference voltage generating circuit are respectively connected to the reference voltage output terminal through a switch; the reference voltage selection unit comprises a first AND gate, a second AND gate, a first inverter and a control end, and the control end is used for inputting the dynamic detection control signal; one input end of the first AND gate is used for inputting a mode control signal, and the other input end of the first AND gate is connected to the control end; one input end of the second AND gate is used for inputting a mode control signal, the other input end of the second AND gate is connected to the output end of the first phase inverter, and the input end of the first phase inverter is connected to the control end.

10. The audio power amplifier circuit of claim 8, wherein the threshold voltage adjustment module further comprises: and the dynamic detection unit is used for detecting the amplitude range of the output signal of the integral amplification unit and outputting a dynamic detection control signal corresponding to the amplitude range of the output signal.

11. The audio power amplifier circuit of claim 10, wherein the dynamic detection unit comprises: the dynamic detection circuit comprises a comparator and a latch circuit, wherein two positive input ends of the comparator are respectively used for inputting two output signals of the integral amplification unit, a negative input end of the comparator is used for inputting a first threshold value, an output end of the comparator is connected to the latch circuit, the dynamic detection control signal is output by the circuit, the latch circuit outputs a dynamic detection control signal which is opposite to the output signal of the comparator, and the dynamic detection control signal is latched in a high-level output state when the dynamic detection control signal is at a high level.

12. The audio power amplifier circuit of claim 11, wherein the latch circuit comprises: a flip-flop, a transistor MP1, a transistor MP2, a transistor MP3, a transistor MN1, a transistor MN2, and a second inverter; one input end of the trigger is connected to the output end of the comparator, and the non-inverting output end of the trigger is connected to the grid of the transistor MP 1; the source electrode of the transistor MP1, the source electrode of the transistor MP2 and the source electrode of the transistor MP3 are all connected to a power supply voltage; the drain of the transistor MP1, the drain of the transistor MP2, the drain of the transistor MN1, the gate of the transistor MP3, and the gate of the transistor MN2 are electrically connected to each other; the gate of the transistor MP2, the drain of the transistor MP3, the drain of the transistor MN2, the gate of the transistor MN1, and the input terminal of the second inverter are electrically connected to each other, and the dynamic state detection control signal is output from the second inverter.

13. The audio power amplifier circuit of claim 1, wherein the power limiting module is configured to adjust the input current when one of the two output voltages of the integrating and amplifying unit is lower than the threshold voltage.

14. A power limiting method of an audio power amplifier circuit, wherein the audio power amplifier circuit comprises an integral amplifying unit, is characterized by comprising the following steps:

providing a half-wave modulation common-mode voltage VCM2 to the integral amplification unit according to the output signal of the integral amplification unit, so that the audio power amplifier circuit works in a half-wave modulation mode;

comparing the output voltage of the integral amplification unit with a threshold voltage, wherein the threshold voltage is changed along with a control signal;

according to the comparison result, the input current of the input end of the integral amplification unit is adjusted so as to limit the output voltage of the integral amplification unit within a preset amplitude range;

and modulating the output signal by a modulation signal to output a half-wave modulated pulse width modulation signal.

15. The method of claim 14, wherein the step of providing a half-wave modulated common-mode voltage VCM2 to the integrating amplification unit based on the output signal of the integrating amplification unit comprises: comparing the output signal of the integrating amplifying unit with a first threshold VCM2_ L and a second threshold VCM2_ H; when the amplitude of the output signal is within VCM2_ L-VCM 2_ H, the half-wave modulation common-mode voltage VCM2 is a fixed value; when the output signal amplitude is less than the first threshold VCM2_ L, the half-wave modulated common mode voltage VCM2 is less than the fixed value and gradually decreases the half-wave modulated common mode voltage VCM2 as the signal amplitude decreases.

16. The power limiting method of claim 15 wherein the fixed value is a common-mode reference voltage VCM, VCM ═ 2 (VCM2_ L + VCM2_ H)/VCM; the modulation signal is a triangular wave, the amplitude is PWM _ L-PWM _ H, and VCM > (PWM _ L + PWM _ H)/2; VCM2_ H is greater than or equal to PWM _ H.

17. The power limiting method of claim 14 wherein the input current of the integrating and amplifying unit is adjusted to adjust the output voltage amplitude when one of the pair of differential signals at the output of the integrating and amplifying unit is below the threshold voltage.

18. The method of claim 14, wherein the threshold voltage is further linear with respect to a reference voltage, and wherein output signals of different magnitude ranges correspond to different reference voltages.

19. The power limiting method of claim 14, comprising: adjusting the threshold voltage by adjusting at least one of the control signal, a correlation coefficient between the threshold voltage and the control signal, and a correlation coefficient between the threshold voltage and the reference voltage.

20. The method of claim 14, wherein the step of adjusting the input current to the input of the integrator-amplifier unit comprises: and converting the difference value of the output voltage of the output end of the integral amplification unit and the threshold voltage into output current, and outputting the output current to the input end of the integral amplification unit so as to realize the adjustment of the input current.

21. An electronic device comprising an audio power amplifier circuit according to claims 1 to 13.