A full-loop self-oscillating class D power amplifier circuit

Abstract

The present invention provides a full-loop self-oscillating Class D power amplifier circuit, belonging to the field of active speaker circuits. The present invention comprises a mutually independent woofer amplifier circuit and a treble amplifier circuit, each of which is equipped with a signal modulation module, a trigger shaping module, a driver module, a switch amplifier module, and a low-pass filter. The output of the signal modulation module is connected to the input of the trigger shaping module, the output of the trigger shaping module is connected to the input of the driver module, the output of the driver module is connected to the input of the switch amplifier module, and the output of the switch amplifier module is connected to the input of the low-pass filter. The output of the low-pass filter is provided with a positive feedback pin and a negative feedback pin that also serves as an output pin. The positive feedback pin and the negative feedback pin are respectively connected to the input of the signal modulation module, forming a full-loop feedback circuit. The present invention significantly reduces distortion.

Description

Technical Field

[0001] The present invention relates to an active speaker circuit, in particular to a full-loop self-oscillating class D power amplifier circuit. Background Art

[0002] Simply put, a Class D amplifier operates in a switching mode, where the power amplifier components are in an amplification mode. The principle behind this approach is to compare an audio signal with a high-frequency fixed-frequency signal, generating a modulated signal on a fixed-frequency carrier. This signal is then converted into a PWM signal, which is then amplified by a switching amplifier into a high-voltage, high-current, high-power PWM signal. This high-power audio signal is then restored to its original state by passing it through a low-pass filter.

[0003] This approach allows the amplifier element (typically a transistor) to enter a saturated state from the start of operation. The transistor acts like a switched-on switch, directly connecting the power supply to the load. Ideal switching amplifier circuits exhibit zero voltage drop, consume no energy, and generate no heat, eliminating the need for bulky heat sinks. Actual Class D amplifier circuits also experience almost exclusively the transistor's saturation voltage drop, so actual losses are largely dependent on the transistor's characteristics and unrelated to the signal output amplitude. This makes it particularly well-suited for high-power audio, energy-efficient amplification, and most applications requiring limited space.

[0004] Comparable Class D amplifiers on the market typically utilize fully integrated driver chips, which have a relatively fixed drive structure, limited driving capabilities, and lack comprehensive and reliable protection circuits. Furthermore, due to the limited circuit architecture, they cannot utilize the large-loop negative feedback commonly used in Class A / B amplifiers, leaving little room for improvement in distortion, a key performance metric for Class D amplifiers. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present invention provides a full-loop self-oscillating Class D power amplifier circuit.

[0006] The present invention includes a mutually independent bass power amplifier circuit and a tweeter power amplifier circuit, which are respectively used to drive a tweeter and a woofer, wherein the bass power amplifier circuit and the tweeter power amplifier circuit are both provided with a signal modulation module, a trigger shaping module, a driving module, a switch amplification module and a low-pass filter, wherein the output end of the signal modulation module is connected to the input end of the trigger shaping module, the output end of the trigger shaping module is connected to the input end of the driving module, the output end of the driving module is connected to the input end of the switch amplification module, the output end of the switch amplification module is connected to the input end of the low-pass filter, and the output end of the low-pass filter is provided with a positive feedback pin and a negative feedback pin which also serves as an output pin, and the positive feedback pin and the negative feedback pin are respectively connected to the input end of the signal modulation module to form a full-loop feedback circuit.

[0007] The present invention is further improved in that the tweeter power amplifier circuit adopts a half-bridge output stage topology structure, and the bass power amplifier circuit adopts a full-bridge output stage topology structure.

[0008] The present invention is further improved, the driving module includes a positive phase driving unit and a negative phase driving unit, the switching amplifier module includes two switching amplifier units respectively connected to the output ends of the positive phase driving unit and the negative phase driving unit, and the output end of the switching amplifier unit is connected to the input end of the low-pass filter.

[0009] The present invention is further improved, and the low-pass filter of the bass amplifier circuit is a common-mode inductor low-pass filter, including a common-mode inductor L1, a first switching amplifying unit connected to the input pin 4 of the common-mode inductor L1, and a second switching amplifying unit connected to the input pin 1 of the common-mode inductor L1. The common-mode inductor low-pass filter also includes a grounding capacitor C7 and a grounding capacitor C22. The output pin 3 of the common-mode inductor L7 is connected to one end of the grounding capacitor C7 and outputs the bass audio OUTW+. The output pin 2 of the common-mode inductor L7 is connected to one end of the grounding capacitor C22 and outputs the bass audio OUTW-.

[0010] The low-pass filter of the tweeter amplifier circuit includes an inductor L2 and a capacitor C41, wherein the input end of the inductor L1 is connected to the output end of the switching amplifier module, the output end of the inductor L1 is connected to one end of the capacitor C41 and outputs the tweeter audio OUTT+, the other end of the capacitor C41 is grounded, the positive feedback pin FB1 is respectively connected to one end of the parallel capacitors C40 and C141 and one end of the parallel resistors R64 and R65, the other ends of the parallel capacitors C40 and C141 are connected to the output end of the inductor L1, and the other ends of the parallel resistors R64 and R65 are grounded.

[0011] The present invention is further improved in that a differential filter is further provided between the output end and the output pin of the common-mode inductor low-pass filter, and the differential filter includes resistors R73, R75 and a capacitor C18, wherein one end of the resistors R73 and R75 connected in parallel is connected to the output pin 3 of the common-mode inductor L7, and the other end is connected to one end of the capacitor C18, and the other end of the capacitor C18 is connected to the output pin 2 of the common-mode inductor L7. The first positive feedback pin is connected to one end of the capacitor C18 through the parallel capacitor C142 and the capacitor C12, and the second positive feedback pin is connected to the other end of the capacitor C18 through the parallel capacitor C143 and the capacitor C21.

[0012] The present invention is further improved, the signal modulation module of the bass power amplifier circuit includes a high-speed comparator IC5 and its peripheral resistor and capacitor components, wherein:

[0013] The inverting input terminal of the high-speed comparator IC5 is connected to one end of the resistor R8 and the capacitor C5 respectively. The other end of the capacitor C5 is connected to the first positive feedback pin FB1. The other end of the resistor R8 is connected to one end of the resistor R5 and the resistor R7 and the grounded capacitor C8 respectively. The other end of the resistor R5 is connected to the output pin OUTW+. The other end of the resistor R7 inputs the audio signal INW- through the capacitor C3.

[0014] The non-inverting input terminal of the high-speed comparator IC5 is connected to one end of the resistor R17 and the capacitor C16 respectively. The other end of the capacitor C16 is connected to the second positive feedback pin FB2. The other end of the resistor R17 is connected to the resistor R19, one end of the resistor R16 and the grounded capacitor C9 respectively. The other end of the resistor R19 is connected to the output pin OUTW-. The other end of the resistor R16 inputs the audio signal INW+ through the capacitor C13.

[0015] Pins 5 and 6 of the high-speed comparator IC5 are suspended, pins 1 and 4 are connected to a -15A power supply and grounded through a capacitor C19, and pin 8 is connected to a +15A power supply and grounded through a capacitor C4; pin 7 of the high-speed comparator IC5 is an output pin.

[0016] The signal modulation module of the tweeter power amplifier circuit includes a high-speed comparator IC11 and its peripheral resistor and capacitor components, wherein:

[0017] The inverting input terminal of the high-speed comparator IC11 is connected to one end of the resistor R63 and the capacitor C42 respectively. The other end of the capacitor C42 is connected to the positive feedback pin FB3. The other end of the resistor R63 is connected to the resistor R58, one end of the resistor R62 and the grounded capacitor C46 respectively. The other end of the resistor R58 is connected to the output pin OUTT+. The other end of the resistor R62 inputs the audio signal INT- through the capacitor C43.

[0018] The non-inverting input terminal of the high-speed comparator IC11 is connected to one end of the resistor R71 and the capacitor C54 respectively, the other end of the capacitor C54 is grounded, the other end of the resistor R71 is connected to one end of the resistor R70, the resistor R74 and the grounded capacitor C49 respectively, the other end of the resistor R74 is grounded, and the other end of the resistor R70 inputs the audio signal INT+ through the capacitor C50.

[0019] Pins 5 and 6 of the high-speed comparator IC11 are suspended, pins 1 and 4 are connected to the -15B power supply and grounded through capacitor C53, pin 8 is connected to the +15B power supply and grounded through capacitor C39; pin 7 of the high-speed comparator IC11 is an output pin.

[0020] The present invention is further improved. The trigger shaping module of the bass power amplifier circuit has the same structure as the trigger shaping module of the treble power amplifier circuit. The trigger shaping module of the bass power amplifier circuit includes a trigger IC4, a transistor Q3, diodes D11, D3, D4, D8, D9 and peripheral resistors and capacitors, wherein:

[0021] The base of transistor Q1 is connected to the -15A power supply, the emitter is connected to the output end of the signal modulation module, the collector is connected to the positive electrode of diode D11, the pin 1 of trigger IC4A is connected to the ground resistor R14 and the negative electrode of diode D11 respectively, the other end of resistor R14 and pin 2 of trigger IC4A are connected to the -30V power supply, the pin 5 of trigger IC4A is connected to the 5V power supply through resistor R3, the pin 6 is connected to one end of resistor R6, the negative electrode of diode D8 and pin 3 of trigger IC4B respectively, the trigger IC4 Pin 4 of B is respectively connected to one end of resistor R9 and the cathode of diode D9. The other ends of resistors R6 and R9 are respectively connected to different pins of the drive module. The anode of diode D8 is respectively connected to the anode of diode D4, the other end of resistor R6, and one end of capacitor C10. The anode of diode D9 is respectively connected to the anode of diode D3, the other end of resistor R9, and one end of capacitor C11. The cathodes of diodes D4 and D3 are connected to the mute pin. The other ends of capacitors C10 and C11 are connected to a -30V power supply.

[0022] The present invention is further improved, wherein the positive phase driving unit of the bass amplifier circuit includes a driver chip IC3, and the negative phase driving unit includes a driver chip IC6. Both the driver chip IC3 and the driver chip IC6 use the MP18021A chip, wherein the other end of the resistor R6 is respectively connected to the 6th pin IL pin of the driver chip IC3 and the 5th pin IH pin of the driver chip IC3, and the other end of the resistor R9 is respectively connected to the 5th pin IH pin of the driver chip IC3 and the 6th pin IL pin of the driver chip IC3.

[0023] The present invention is further improved, wherein the switching amplification unit includes two switching tubes, wherein the gate of the switching tube Q1 of the first switching amplification unit is connected to pin 2 of the driver chip IC3, the drain is connected to a 30V power supply and is grounded through a capacitor C1, and the source is respectively connected to the drain of the switching tube Q2 and the input end of the filter. The gate of the switching tube Q2 is respectively connected to the anode of the diode D10 and one end of the resistor R14, the cathode of the diode D10 and the other end of the resistor R15 are connected to pin 8 of the driver chip IC3, and the source of the switching tube Q2 is connected to a -30V power supply and is grounded through a capacitor C15.

[0024] The present invention is further improved. The low-pass filter of the tweeter amplifier circuit includes an inductor L2 and a capacitor C41, wherein the input end of the inductor L1 is connected to the output end of the switching amplifier module, the output end of the inductor L1 is connected to one end of the capacitor C41 and outputs the tweeter audio OUTT+, the other end of the capacitor C41 is grounded, and the positive feedback pin FB1 is respectively connected to one end of the parallel capacitors C40 and C141 and one end of the parallel resistors R64 and R65, the other end of the parallel capacitors C40 and C141 is connected to the output end of the inductor L1, and the other end of the parallel resistors R64 and R65 is grounded.

[0025] Compared with the existing technology, the beneficial effects of the present invention are: the balanced audio signal feed plus the full-loop self-oscillating Class D power amplifier circuit solution can easily introduce large-loop audio negative feedback. Compared with the conventional Class D power amplifier, it greatly reduces the distortion, provides high-quality music playback capabilities, and the sound is clearer and more transparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of the present invention;

[0027] Figure 2 This is a schematic diagram of the circuit of the present invention;

[0028] Figure 3 This is the schematic diagram of the bass amplifier circuit;

[0029] Figure 4 This is the schematic diagram of the tweeter amplifier circuit;

[0030] Figure 5 This is a schematic diagram of the power supply circuit of the present invention;

[0031] Figure 6 This is a circuit diagram of the peripheral speaker DSP board of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0033] like Figure 2 、 Figure 5-6 As shown, the input audio signal of the present invention is processed by the DSP board and output to the full-loop self-oscillating Class D power amplifier circuit of the present invention, and the power supply circuit provides power for the entire speaker circuit including the power amplifier circuit of this example. Since the focus of the present invention is improved on the power amplifier circuit, other modules are not described here.

[0034] like Figure 1As shown, this example includes a bass amplifier circuit and a tweeter amplifier circuit that are independent of each other, which are used to drive the tweeter and the woofer, respectively. The bass amplifier circuit and the tweeter amplifier circuit are both provided with a signal modulation module, a trigger shaping module, a driving module, a switch amplification module and a low-pass filter. The output end of the signal modulation module is connected to the input end of the trigger shaping module, the output end of the trigger shaping module is connected to the input end of the driving module, the output end of the driving module is connected to the input end of the switch amplification module, the output end of the switch amplification module is connected to the input end of the low-pass filter, and the output end of the low-pass filter is provided with a positive feedback pin and a negative feedback pin that also serves as an output pin. The positive feedback pin and the negative feedback pin are respectively connected to the input end of the signal modulation module to form a full-loop feedback circuit.

[0035] like Figure 3 and Figure 4 As shown, the two amplifier circuit channels in this example share similar principles, each module employing a separate, independent design. Different output stage topologies, half-bridge and full-bridge, are employed due to varying power requirements. This example first uses a tweeter amplifier circuit, which has a relatively simple and intuitive architecture, for technical analysis.

[0036] like Figure 4 As shown, this example uses the LM311 high-speed comparator to reinvent the circuit. By utilizing the inherent phase shift characteristics of the LC filter output by the Class D power amplifier circuit, the comparator's inverting input is introduced from the final output terminal OUTT+ to the LC filter's high-frequency phase flip. This transforms the entire large loop of the power amplifier circuit into a special phase-shift oscillator, creating a novel full-loop self-oscillating Class D amplifier circuit. Although the structure of this circuit is relatively simple, its conception and application are very ingenious. A detailed analysis is as follows:

[0037] The inductor L2 and capacitor C41 at the output end form an LC low-pass filter. The oscillation frequency of the entire power amplifier circuit is mainly determined by the values ​​of these two inductors and capacitors. The inductor L2 is 22uH and the capacitor C41 is 1uF. Calculation shows that the upper cutoff frequency of this low-pass filter is set to ≈33.9kHz. This LC low-pass filter will produce a phase lag offset close to 180° near 10 times the cutoff frequency point (that is, ≈340kHz). In addition, the phase lag caused by the conversion rate and bandwidth limitation of the IC11 high-speed comparator LM311, and the conduction delay caused by other trigger shaping modules, drive modules and switch amplifier modules in the entire loop will also bring phase lag. The phase superposition of these lags will result in a phase lag offset near 10 times the cutoff frequency point of the low-pass filter that is equal to or greater than 180°, which is a prerequisite for high-frequency self-oscillation of the entire circuit.

[0038] Among them, the two 464Ω resistors R64 and R65 and the two 10nF capacitors C40 and C141 form a high-precision RC high-pass filter with a lower cutoff frequency set to ≈34.3kHz. This filter removes audio frequencies below 20kHz from the overall operating frequency band of the LC low-pass filter output terminal OUTT+. Furthermore, the residual sine wave of the high-frequency signal of approximately 340kHz set as described above, after being filtered by the LC low-pass filter, is fed back to the inverting input terminal of the high-speed comparator IC11 via the positive feedback pin FB3 connected to capacitor C42. The presence of this capacitor introduces a slightly leading phase difference to the high-frequency feedback path (but has no significant effect on the entire loop, especially the phase lag caused by the LC filter to the flip frequency). This accelerates the shaping of the high-frequency signal and makes the modulation oscillation working state of the high-speed comparator IC11 more ideal.

[0039] The entire power amplifier loop has a predetermined 180° phase flip at the IC12 trigger shaping module. If, at a set higher frequency point, the conduction delays caused by the output LC low-pass filter and other circuits in the entire loop are superimposed, the sum of all phase shifts resulting in the phase lag is exactly equal to 180°, then for this frequency point, the output and input ends of the entire high-frequency conduction loop are in phase with each other, that is, in positive feedback mode. At this time, the high-frequency AC loop of the LM311 high-speed comparator circuit constitutes a phase-shifted oscillator to generate an oscillating square wave signal. This is the entire generation mechanism of the high-frequency self-oscillation of the entire power amplifier circuit.

[0040] The actual oscillation frequency drops from the originally preset 340kHz to around 230kHz. This is due to the insufficient conversion rate and bandwidth of the LM311 high-speed comparator IC11, as mentioned above. Furthermore, the trigger shaping module, driver module, and switch amplifier module in the loop increase the conduction delay, causing the phase lag of the entire loop to shift to 180° and reduce the self-oscillation frequency. As long as the component parameters and selection of the entire high-frequency conduction path are fixed, the actual self-oscillation frequency of the entire loop will be controllable and stable.

[0041] If there is no input signal, the non-inverting input of high-speed comparator IC11 is grounded, and the OUTT+ output is a standard square wave with a self-oscillating frequency of approximately 230kHz and a 50% duty cycle. The input of the LM311 high-speed comparator IC11 is a combination of the audio signal and the overall loop feedback signal. Changes in the audio signal alter the comparator's zero-crossing point, or the flipping threshold, and thus the duty cycle of the oscillating square wave, ensuring that the duty cycle fully follows the audio signal. The LM311 high-speed comparator IC11 outputs a PWM signal modulated by the audio signal.

[0042] The PWM signal output from pin 7 of high-speed comparator IC11 is converted by BC807 transistor Q14 to convert the current direction of the comparator's output. It then undergoes accelerated shaping and phase inversion by two SN74LVC2G04 high-speed Schmitt triggers, IC12, converting it into a symmetrical PWM drive signal with complementary high and low-side operation. This signal then passes through the high-speed, high-performance half-bridge driver MP18021A IC10, further driving two small AON6280 surface-mount field-effect transistors, Q9 and Q12, to operate in a near-ideal switching state, converting the positive and negative power supplies into high-voltage, high-current, high-speed, high-power PWM signals. After filtering through the output LC low-pass filter, the amplified audio is generated. Based on the supply voltage, the rated output power of this amplifier circuit in half-bridge operation can reach 50W / 8Ω.

[0043] In this example, the audio feedback loop undergoes a predetermined 180° phase flip at the IC12 trigger-shaping circuit. Within the audio frequency range, the conduction delays caused by the output LC low-pass filter and the other circuits in the loop are minimal, resulting in only a slight phase shift. Therefore, the entire loop output is in phase with the input, effectively operating in negative feedback mode. Due to the introduction of negative feedback within the large audio loop, output distortion can be reduced by one or even several orders of magnitude compared to conventional Class D amplifiers. This amplifier circuit provides high-quality music playback, resulting in clear, transparent, and highly accurate sound reproduction.

[0044] like Figure 3 As shown in the figure, the bass amplifier circuit adopts a full-bridge output stage topology due to its higher power demand. Therefore, an inverting drive circuit is added to drive the other two AON6280 small surface-mount field-effect transistors Q4 and Q7. Among them, the two drive circuits of the bass amplifier circuit have the same drive circuit structure as the tweeter amplifier circuit.

[0045] In this example, the output low-pass filter is changed from an LC low-pass filter to a common-mode inductor low-pass filter. The output LC low-pass filter and the high-frequency RC feedback path feeding back to the comparator input are added accordingly. At the same time, the component parameters are re-adapted to match the change in the output stage topology.

[0046] Similarly, in this example, the common-mode inductor L1 and capacitors C7 and C22 at the output end form an LC common-mode low-pass filter, and are connected to the capacitor C18 through two parallel 0.03Ω resistors R73 and R75 (load current sampling resistors with negligible effect on filter parameters) to form a differential filter. The oscillation frequency of the entire power amplifier circuit is mainly determined by the values ​​of these four inductors and capacitors. The inductor L2 has a value of 11uH, the capacitors C7 and C22 have a value of 0.47uF, and the capacitor C18 has a value of 1uF. The upper cutoff frequency of this low-pass filter is set to ≈35kHz, and it will also produce a phase lag offset close to 180° near 10 times the cutoff frequency point (that is, ≈350kHz); similarly, due to the superposition of conduction delays caused by other trigger shaping modules, two sets of drive units and two sets of switching amplifier units in the entire bass amplifier loop, the phase lag offset of the entire loop to the self-oscillation frequency of 180° flip is also reduced, and the actual self-oscillation frequency of the bass amplifier circuit is reduced from the original preset 350kHz to about 220kHz.

[0047] The differential output negative terminal OUTW- in this example also adds an audio negative feedback path, matching the change in the output stage topology while forming a complete balanced large-loop negative feedback. The more specific principle structure and calculation analysis of other circuit modules of the bass amplifier are exactly the same as those of the aforementioned half-bridge amplifier for the treble part, so they will not be repeated one by one.

[0048] As can be inferred from the power supply voltage, the subwoofer amplifier circuit in this example uses a full-bridge output mode, and its rated output power can reach 400W / 4Ω. The selection of such miniaturized components and the overall design of the amplifier assembly can stably operate normally in mass production at this relatively high output power level, indicating that the optimized design of this split-type full-loop self-oscillating Class D amplifier circuit is very successful and highly competitive.

[0049] In summary, the Class D amplifier circuit design of this active speaker is novel, simple, efficient, and compact. Its core lies in cleverly utilizing the inherent phase shift characteristics of the LC output low-pass filter in the Class D amplifier circuit to create a full-loop, self-oscillating Class D amplifier. The independent design of each unit circuit and the optimized driver-stage circuit performance achieve excellent drive performance, thereby reducing switching losses in the output power transistors. Furthermore, enhanced protection logic ensures more reliable circuit operation, fully utilizing component performance and allowing for a more compact overall component and amplifier circuit assembly. Furthermore, the balanced audio signal input coupled with the introduction of balanced, large-loop negative feedback significantly reduces distortion compared to conventional Class D amplifiers, providing high-quality music reproduction with clearer and more transparent sound.

[0050] The specific implementation manner described above is a preferred implementation manner of the present invention, and is not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific implementation manner. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A full-loop self-oscillating Class D power amplifier circuit, characterized in that: The invention comprises a woofer amplifier circuit and a treble amplifier circuit, each of which is independent of the other, and is used to drive a tweeter and a woofer, respectively. The treble amplifier circuit adopts a half-bridge output stage topology, and the woofer amplifier circuit adopts a full-bridge output stage topology. The woofer amplifier circuit and the treble amplifier circuit are both provided with a signal modulation module, a trigger shaping module, a driving module, a switch amplifier module and a low-pass filter. The driving module includes a positive-phase driving unit and a negative-phase driving unit. The switch amplifier module includes two switch amplifier units respectively connected to the output ends of the positive-phase driving unit and the negative-phase driving unit. The output end of the signal modulation module is connected to the input end of the trigger shaping module, the output end of the trigger shaping module is connected to the input end of the driving module, the output end of the driving module is connected to the input end of the switch amplifier module, and the output end of the switch amplifier unit is connected to the input end of the low-pass filter. The output end of the low-pass filter is provided with a positive feedback pin and a negative feedback pin which also serves as an output pin. The positive feedback pin and the negative feedback pin are respectively connected to the input end of the signal modulation module, forming a full-loop feedback circuit. The signal modulation module of the tweeter power amplifier circuit includes a high-speed comparator IC11 and its peripheral resistor and capacitor components, wherein the inverting input terminal of the high-speed comparator IC11 is respectively connected to the resistor R63 and one end of the capacitor C42, the other end of the capacitor C42 is connected to the positive feedback pin FB3, the other end of the resistor R63 is respectively connected to the resistor R58, one end of the resistor R62 and the grounding capacitor C46, ​​the other end of the resistor R58 is connected to the output pin OUTT+, and the other end of the resistor R62 inputs the audio signal INT- through the capacitor C43; the high The low-pass filter of the audio amplifier circuit includes an inductor L2 and a capacitor C41, wherein the input end of the inductor L2 is connected to the output end of the switching amplifier module, the output end of the inductor L2 is connected to one end of the capacitor C41 and outputs the treble audio OUTT+, the other end of the capacitor C41 is grounded, and the positive feedback pin FB1 is respectively connected to one end of the parallel capacitors C40 and C141 and one end of the parallel resistors R64 and R65, the other ends of the parallel capacitors C40 and C141 are connected to the output end of the inductor L2, and the other ends of the parallel resistors R64 and R65 are grounded.

2. The full-loop self-oscillating Class D power amplifier circuit according to claim 1, wherein: The low-pass filter of the bass amplifier circuit is a common-mode inductor low-pass filter, including a common-mode inductor L1, a first switching amplifying unit connected to input pin 4 of the common-mode inductor L1, and a second switching amplifying unit connected to input pin 1 of the common-mode inductor L1. The common-mode inductor low-pass filter also includes a grounding capacitor C7 and a grounding capacitor C22. The output pin 3 of the common-mode inductor L1 is connected to one end of the grounding capacitor C7 and outputs the bass audio OUTW+. The output pin 2 of the common-mode inductor L1 is connected to one end of the grounding capacitor C22 and outputs the bass audio OUTW-.

3. The full-loop self-oscillating Class D power amplifier circuit according to claim 2, wherein: A differential filter is also provided between the output end and the output pin of the common-mode inductor low-pass filter. The differential filter includes resistors R73, R75 and a capacitor C18, wherein one end of the resistors R73 and R75 connected in parallel is connected to the output pin 3 of the common-mode inductor L1, and the other end is connected to one end of the capacitor C18. The other end of the capacitor C18 is connected to the output pin 2 of the common-mode inductor L1. The first positive feedback pin is connected to one end of the capacitor C18 through the parallel capacitor C142 and the capacitor C12, and the second positive feedback pin is connected to the other end of the capacitor C18 through the parallel capacitor C143 and the capacitor C21.

4. The full-loop self-oscillating Class D power amplifier circuit according to claim 3, wherein: The signal modulation module of the bass power amplifier circuit also includes a high-speed comparator IC5 and its peripheral resistor and capacitor components, wherein: The inverting input terminal of the high-speed comparator IC5 is connected to one end of the resistor R8 and the capacitor C5 respectively. The other end of the capacitor C5 is connected to the first positive feedback pin FB1. The other end of the resistor R8 is connected to one end of the resistor R5 and the resistor R7 and the grounded capacitor C8 respectively. The other end of the resistor R5 is connected to the output pin OUTW+. The other end of the resistor R7 inputs the audio signal INW- through the capacitor C3. The non-inverting input terminal of the high-speed comparator IC5 is connected to one end of the resistor R17 and the capacitor C16 respectively. The other end of the capacitor C16 is connected to the second positive feedback pin FB2. The other end of the resistor R17 is connected to the resistor R19, one end of the resistor R16 and the grounded capacitor C9 respectively. The other end of the resistor R19 is connected to the output pin OUTW-. The other end of the resistor R16 inputs the audio signal INW+ through the capacitor C13. Pins 5 and 6 of the high-speed comparator IC5 are suspended, pins 1 and 4 are connected to a -15A power supply and grounded through a capacitor C19, and pin 8 is connected to a +15A power supply and grounded through a capacitor C4; pin 7 of the high-speed comparator IC5 is an output pin. The signal modulation module of the tweeter power amplifier circuit also includes peripheral resistor and capacitor components of the high-speed comparator IC11, wherein: The non-inverting input terminal of the high-speed comparator IC11 is connected to one end of the resistor R71 and the capacitor C54 respectively, the other end of the capacitor C54 is grounded, the other end of the resistor R71 is connected to one end of the resistor R70, the resistor R74 and the grounded capacitor C49 respectively, the other end of the resistor R74 is grounded, and the other end of the resistor R70 inputs the audio signal INT+ through the capacitor C50. Pins 5 and 6 of the high-speed comparator IC11 are suspended, pins 1 and 4 are connected to the -15B power supply and grounded through capacitor C53, pin 8 is connected to the +15B power supply and grounded through capacitor C39; pin 7 of the high-speed comparator IC11 is an output pin.

5. The full-loop self-oscillating Class D power amplifier circuit according to claim 2, wherein: The trigger shaping module of the bass power amplifier circuit has the same structure as the trigger shaping module of the treble power amplifier circuit. The trigger shaping module of the bass power amplifier circuit includes a trigger IC4, a transistor Q3, diodes D11, D3, D4, D8, D9 and peripheral resistors and capacitors, wherein: The base of transistor Q1 is connected to the -15A power supply, the emitter is connected to the output end of the signal modulation module, the collector is connected to the positive electrode of diode D11, the pin 1 of trigger IC4A is connected to the ground resistor R14 and the negative electrode of diode D11 respectively, the other end of resistor R14 and pin 2 of trigger IC4A are connected to the -30V power supply, the pin 5 of trigger IC4A is connected to the 5V power supply through resistor R3, the pin 6 is connected to one end of resistor R6, the negative electrode of diode D8 and pin 3 of trigger IC4B respectively, the trigger IC4 Pin 4 of B is respectively connected to one end of resistor R9 and the cathode of diode D9. The other ends of resistors R6 and R9 are respectively connected to different pins of the drive module. The anode of diode D8 is respectively connected to the anode of diode D4, the other end of resistor R6, and one end of capacitor C10. The anode of diode D9 is respectively connected to the anode of diode D3, the other end of resistor R9, and one end of capacitor C11. The cathodes of diodes D4 and D3 are connected to the mute pin. The other ends of capacitors C10 and C11 are connected to a -30V power supply.

6. The full-loop self-oscillating Class D power amplifier circuit according to claim 5, wherein: The positive phase driving unit of the bass amplifier circuit includes a driving chip IC3, and the negative phase driving unit includes a driving chip IC6. Both the driving chip IC3 and the driving chip IC6 use the MP18021A chip. The other end of the resistor R6 is respectively connected to the 6th pin IL pin of the driving chip IC3 and the 5th pin IH pin of the driving chip IC3. The other end of the resistor R9 is respectively connected to the 5th pin IH pin of the driving chip IC3 and the 6th pin IL pin of the driving chip IC3.

7. The full-loop self-oscillating Class D power amplifier circuit according to claim 6, wherein: The switching amplifier unit includes two switching tubes, wherein the gate of the switching tube Q1 of the first switching amplifier unit is connected to pin 2 of the driver chip IC3, the drain is connected to a 30V power supply and is grounded through a capacitor C1, and the source is respectively connected to the drain of the switching tube Q2 and the input end of the filter. The gate of the switching tube Q2 is respectively connected to the anode of the diode D10 and one end of the resistor R14, the cathode of the diode D10 and the other end of the resistor R15 are connected to pin 8 of the driver chip IC3, and the source of the switching tube Q2 is connected to a -30V power supply and is grounded through a capacitor C15.

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