CN112671353A - Low-distortion D-type power amplifier applied to high-power range - Google Patents
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Abstract
The invention belongs to the technical field of audio power amplifiers, and discloses a low-distortion D-type power amplifier applied to a high-power range, which comprises the following components: a voltage control module, a current self-excited inner ring oscillation circuit, an MOS switch circuit, an output LC filter circuit, a nonlinear compensation module and a self-excited oscillation frequency adjusting module, the current self-excited inner ring oscillation circuit consists of a comparator and an output LC capacitance current sampling feedback circuit with current feedback connected with the comparator, the voltage control module is provided with a high-frequency phase control circuit for adjusting the switching frequency phase delay of the circuit and eliminating nonlinearity caused by high-frequency fluctuation, the self-oscillation frequency adjusting module adjusts the oscillation frequency according to the amplitude of an input signal, the change range of the switching frequency is narrowed, the adaptability of a voltage loop is increased and the nonlinearity distortion is reduced, the output LC capacitance current sampling feedback circuit adopts a mode that an output capacitor is connected with a current mirror with a small capacitor in parallel, the nonlinear compensation module carries out nonlinear compensation on the circuit, and further eliminates the amplitude distortion of the full signal of the circuit.
Description
Technical Field
The invention belongs to the technical field of audio power amplifiers, and discloses a low-distortion D-type power amplifier applied to a high-power range.
Background
The class D power amplifier simply means an amplification mode in which the power amplification element is in a switch operation state. The principle is realized by comparing an audio signal with a high-frequency fixed frequency signal to obtain a modulation signal of the audio signal on a carrier wave with fixed frequency, namely converting the modulation signal into a PWM signal, amplifying the PWM signal into a high-voltage and high-current high-power PWM signal through a switching amplifier, and finally restoring the high-power audio signal through a low-pass filter.
The distortion of the digital D-type power amplifier has a unique source relative to the analog power amplifier, a good digital power amplifier circuit can be designed to meet high dynamic performance, but the fluctuation of the switching frequency is inevitably introduced into a control loop, and the fluctuation is sampled and reflected to output by a switching comparator to cause larger distortion of the digital power amplifier. The control loop adjusts not only the dynamic control characteristic but also the phase delay characteristic of the switching frequency. Theoretically, perfect phase delay characteristics are designed, the positive and negative trip point voltage fluctuation of the comparator can be added to be 0, and the fluctuation does not affect the output although existing, namely the nonlinearity of the high-frequency fluctuation can be eliminated. The power amplifier distortion can realize the level of less than 0.0002% in the full audio frequency range after the point is achieved.
The existing digital power amplifier has high performance and is in a self-oscillation working mode, and the problem that the oscillation frequency becomes low as the signal amplitude becomes large is solved while the high performance is obtained, and the frequency becomes lower by 50% or more than that of a small signal when a large signal is generated, so that the control loop has to reduce the speed to move to the working state of the large signal amplitude. At the same time, the frequency is greatly changed, so that the high-frequency phase control is difficult, and therefore, the distortion is increased sharply when the high-signal amplitude work is carried out. And, when the amplitude of the large signal is large, the output voltage OUT is close to the power supply VCC, the output inductive current is not triangular wave any more, but has a point circular arc deformation, the frequency becomes more serious after the frequency becomes lower, the average value of the current peak-to-peak value no longer represents the average value of the current, and the complex nonlinear characteristic is generated at the moment.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention discloses a low-distortion D-type power amplifier applied to a high-power range, which has the following specific technical scheme:
a low distortion class D power amplifier for use in a high power range, comprising: the circuit comprises a voltage control module, a current self-excited inner ring oscillation circuit, an MOS (metal oxide semiconductor) switching circuit, an output LC (inductance capacitance) filter circuit, a nonlinear compensation module and a self-excited oscillation frequency adjusting module, wherein the current self-excited inner ring oscillation circuit consists of a comparator and an output LC capacitance current sampling feedback circuit connected with the comparator in a feedback mode; the input end of the nonlinear compensation module is connected with an input voltage VIN, and the output end of the nonlinear compensation module outputs a nonlinear compensation function signal to the output end of the voltage control module; the input end of the self-oscillation frequency adjusting module is connected with an input voltage VIN, and the output end of the self-oscillation frequency adjusting module is connected with a comparator.
Furthermore, the voltage control module is provided with a high-frequency phase control circuit, and the high-frequency phase control circuit is provided with a plurality of high-frequency zero poles for accurately adjusting the phase of the switching frequency point.
Further, the output LC capacitive current sampling feedback circuit performs sampling feedback on the capacitive current of the output LC filter circuit, and adopts one of the following modes:
a: the output capacitor of the output LC filter circuit is connected with a small capacitor in parallel, the current of the small capacitor is a mirror image of the output capacitor reduced in proportion, a virtual ground is formed at the lower end of the small capacitor by using a virtual ground generation and current detection module to absorb the current of the small capacitor, and the virtual ground generation and current detection module outputs a current signal of the output capacitor;
b: the output capacitor of the output LC filter circuit is connected with a small capacitor in parallel, the current of the small capacitor is a mirror image of the output capacitor reduced in proportion, a virtual ground is formed at the lower end of the capacitor by using a virtual ground generation and current detection module to absorb the current of the capacitor, a resistor is connected in series at the control output end of a front-stage circuit to offset the low-frequency part of the mirror image current, and the virtual ground generation and current detection module outputs the high-frequency part of an output capacitor current signal;
c: an output capacitor of the output LC filter circuit is connected with a current detection sensor, and a sampling current is obtained through detection of the current detection sensor, wherein the current detection sensor comprises a current transformer or a resistor;
d: an output capacitor of the output LC filter circuit is connected with a small capacitor in parallel, the small capacitor is connected with a resistor in series and then grounded, and sampling is amplified by a resistor voltage amplifier for multiple times to obtain an approximate output capacitor current signal;
e: the output capacitor of the output LC filter circuit is connected with a small capacitor in parallel, the small capacitor is connected with a resistor in series and then connected with a preceding stage circuit to control output, and the high-frequency part of the current signal of the approximate output capacitor is obtained by sampling and amplifying the signal by a resistor voltage amplifier by multiple times.
Furthermore, the input end of the virtual ground generation and current detection module is externally represented as low resistance to absorb external injection current, and the output end of the virtual ground generation and current detection module outputs a detection value of the external injection current from the input end to obtain an output voltage signal V = K × I, wherein K is a constant and I is the external injection current.
Further, the virtual ground generation and current detection module sinks current using an OPA860 chip or a transconductance amplifier to form a virtual ground and convert the current to a voltage.
Further, the self-excited oscillation frequency adjusting module obtains and adjusts a hysteresis value by adopting an analog circuit or through MCU calculation, the analog circuit comprises an RC filter circuit, the RC filter circuit is connected to an input voltage VIN, an output voltage signal VIN2 is used for replacing an output voltage OUT signal, the absolute value of the voltage signal VIN2 and a power supply voltage VCC to a function f2(abs (VIN2), VCC) operation circuit are output, a hysteresis value required when the frequency is stable is obtained, and the frequency is stabilized by a hysteresis amplitude control circuit according to the hysteresis value, wherein the f2(abs (VIN2), VCC) analog circuit realizes fitting by using a linear function or a broken line method.
Further, the nonlinear compensation module eliminates the full-signal amplitude distortion of the circuit by using an analog circuit or by MCU calculation, the analog circuit is provided with an RC filter circuit, the input end of the RC filter circuit is connected with the input voltage VIN and the output voltage VIN2, and meanwhile, the power voltage VCC is input to a nonlinear compensation function f1(VIN2, VCC) circuit to obtain the compensation value of the circuit.
Further, the nonlinear compensation function f1(VIN2, VCC) analog circuit implementation uses a broken line fitting.
The sampling of the output capacitance current adopts a mirror image mode, small capacitors are connected in parallel, the current needing to be sampled can be reduced by many times, and then the mirror image capacitance current is collected, so that the mirror image capacitance current collection mode has the advantages of extremely low distortion rate and low cost; the voltage loop is added with well-designed high-frequency phase control, so that the influence of high-frequency ripples in the loop can be greatly eliminated; two benefits may be achieved by adjusting the oscillation frequency by the free-running oscillation frequency adjustment module based on the input signal amplitude. 1: the minimum operating frequency increase may result in faster control loop speeds, 2: after the frequency change becomes smaller, the design of the control loop switch frequency phase delay becomes simpler; after the frequency adjusting circuit is added, the distortion of the signal with the small amplitude becomes very small, but nonlinear distortion of other factors can be generated under the condition of very large signal amplitude, and the nonlinear compensation circuit can eliminate the remaining distortion, so that the distortion of the circuit in a very large amplitude range is extremely low.
Drawings
FIG. 1 is a schematic circuit diagram of the present invention;
FIG. 2 is a schematic diagram of a conventional basic voltage control module using a circuit;
fig. 3, 4, 5 and 6 are schematic circuit diagrams of the voltage control module according to the embodiment of the invention;
FIGS. 7 and 8 are waveform diagrams of high frequency ripple and sampling point of the conventional basic voltage control module for small and large signals, respectively;
fig. 9 and 10 are waveform diagrams of high-frequency ripples and sampling points of the voltage control module provided with the high-frequency phase control circuit according to the present invention when a small signal and a large signal are respectively detected;
FIG. 11 is a BODE diagram of the voltage control module and the basic voltage control module with the high frequency phase control circuit according to the present invention;
FIG. 12 is a circuit BODE diagram of a voltage control module with a high frequency phase control circuit according to the present invention;
fig. 13, 14, 15, 16, 17 and 18 are schematic circuit diagrams for sampling and feeding back the capacitance current of the output LC filter circuit according to the present invention;
FIG. 19a is a schematic circuit diagram of a virtual ground generation and current detection module of the present invention;
FIG. 19b is a schematic circuit diagram of the virtual ground generation and current detection module of the present invention using an OPA860 chip;
FIG. 19c is a schematic circuit diagram of the virtual ground generation and current detection module of the present invention using a transconductance amplifier;
FIG. 20 is a schematic view of a broken line fitting of the nonlinear compensation function of the present invention;
in the figure, 1-a voltage control module, 2-a comparator, 3-a MOS switch circuit, 4-an output LC filter circuit, 5-a nonlinear compensation module, 6-an output LC capacitance current sampling feedback circuit and 7-a self-oscillation frequency adjusting module.
Detailed Description
In order to make the objects, technical solutions and technical effects of the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and examples.
As shown in fig. 1, a low distortion class D power amplifier applied to a high power range includes: the circuit comprises a voltage control module 1, a current self-excited inner ring oscillation circuit, an MOS (metal oxide semiconductor) switch circuit 3, an output LC (inductance capacitance) filter circuit 4, a nonlinear compensation module 5 and a self-excited oscillation frequency adjusting module 7, wherein the current self-excited inner ring oscillation circuit consists of a comparator 2 and a capacitance current sampling feedback circuit 6 of which the current feedback is connected with the output LC of the comparator 2, the input end of the voltage control module 1 is connected with an input voltage VIN, the output end of the voltage control module outputs a control voltage VM to the input end of the comparator 2, the output end of the comparator 2 is connected with the input end of the MOS switch circuit 3, the output end of the MOS switch circuit 3 is connected with the input end of the output LC filter circuit 4, the output end of the output LC filter circuit 4 is connected with the voltage control module 1, and the capacitance current of the output LC filter circuit 4; (ii) a The nonlinear compensation module 5 has a first input end connected to the input voltage VIN, a second input end connected to the power supply voltage VCC, and an output end outputting a nonlinear compensation function signal to the input end of the comparator 2; the first input end of the self-oscillation frequency adjusting module 7 is connected with an input voltage VIN, the second input end is connected with a ground power voltage VCC, and the output end is connected with the comparator 2.
Fig. 2 shows a circuit of a conventional basic voltage control module, which includes an operational amplifier U1, a resistor R1, a resistor R2, a capacitor C1, and a capacitor C2, wherein after being connected in parallel, one end of the capacitor C1 and the resistor R2 is connected to an output terminal of the LC filter circuit 4, the other end of the capacitor C2 is connected to one end of a resistor R1, the other end of the capacitor C2 is connected to an output terminal of the operational amplifier U1, an inverting input terminal of the operational amplifier U1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to an input voltage VIN, and an output of the circuit is VM 1; the circuit can meet the dynamic characteristic of the whole circuit, because the rear-stage current inner loop is equivalent to the first-order characteristic of a current source driving capacitor parallel resistance load, the voltage outer loop is actually very stable, and after the feedback capacitor differential characteristic is added, the characteristics of quick response and no overshoot can be achieved, but the basic circuit does not process high-frequency ripples which are the main source of nonlinear distortion of the circuit.
The voltage control module 1 of the present invention is provided with a high frequency phase control circuit for processing high frequency ripples, and the high frequency phase control circuit comprises the following circuit structure:
as shown in fig. 3, a resistor R3 is added to the basic voltage control module circuit, and the resistor R3 and the capacitor C1 are connected in series, and then the resistor end is connected to the output end of the LC filter circuit 4; the output of this circuit is VM 2;
as shown in fig. 4, a resistor R3, a resistor R4 and a capacitor C3 are added to a basic voltage control module circuit, a resistor end of the resistor R4 and a capacitor C3 are connected in series and then connected to an output end of the LC filter circuit 4, and a resistor R3 and a capacitor C1 are connected in series and then connected to an output end of the LC filter circuit 4; the output of this circuit is VM 3;
as shown in fig. 5, a resistor R3 and a resistor R5 are added to a basic voltage control module circuit, the resistor R3 and a capacitor C1 are connected in series, and then the resistor end is connected to the output end of the LC filter circuit 4, and the resistor R5 is arranged between the capacitor C2 and the output end of the operational amplifier U1; the output of this circuit is VM 4;
as shown in fig. 6, a primary circuit is added to a basic voltage control module circuit, the added circuit includes an operational amplifier U2, a resistor R3, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R10, a capacitor C4 and a capacitor C5, the resistor R3 and the capacitor C1 are connected in series, and then the resistor R5 is disposed between the capacitor C2 and the output terminal of the operational amplifier U1, one end of the capacitor C4 is connected to one end of the resistor R7, the other end of the resistor R7 is connected to one end of the resistor R6 and then connected to the inverting input terminal of the operational amplifier U2, and the other end of the capacitor C4 is connected to the other end of the resistor R6 and then connected to the output terminal of the operational amplifier U1; the output of this circuit is VM 6;
the dynamic characteristics of the circuits can be kept in audio frequency, but a plurality of high-frequency poles-zero can be arranged according to the actual circuit requirements to accurately adjust the phase of a switching frequency point, wherein a resistor R3 can lead the high-frequency phase, a resistor R5 can lead the phase, and the complicated phase control aims at: in the switching frequency range, a suitable phase slope is set. Fig. 6 shows that some circuit structures need to add a stage circuit on the original basis, and a certain phase control can also be added to the stage circuit. After the high-frequency ripple phase is accurately adjusted, the distortion rate can be reduced by two orders of magnitude, and the full audio frequency range reaches below 0.0002%.
Fig. 7 and 8 are waveform diagrams of high-frequency ripple and sampling point of the fundamental voltage control module, where VM1 is the output of the fundamental voltage control module, sample is the comparator flip point, fig. 7 shows that when the signal input level is 0, the duty ratio of the high-frequency switch is 50%, and fig. 8 shows that when a large signal is input, the duty ratio deviates from 50%. It can be seen that the sampling point of VM1 when the switch is turned over does not reflect the average voltage of VM1, and actually has a great nonlinearity, which is the main nonlinear distortion of the circuit.
Fig. 9 and 10 show waveforms of high-frequency ripples and sampling points of a voltage control module provided with a high-frequency phase control circuit according to the present invention, in which the phases of the switching frequency points are shifted backward by approximately 90 degrees. So that the average value of the voltage of the positive and negative switch switching sampling points of the VM2 is just the average value of the VM2 when the input signal amplitude is different, and the influence of the switching frequency ripple is eliminated. More complex phase control can be controlled more accurately, and after the nonlinear distortion is eliminated, the circuit distortion can reach an extremely low level.
As shown in fig. 11 and 12, VM1 is a basic circuit that satisfies the dynamics of the voltage outer loop, and the dynamics of the latter circuits are similar, but the phase is adjusted around the switching frequency point of 500 KHZ. VM2 is the simplest circuit which approximately meets the requirement, the amplitude of the switching frequency point is greatly attenuated by comparing with VM1, namely the reduction of the control voltage ripple is beneficial to reducing nonlinearity, and meanwhile, the phase of the switching frequency point is greatly adjusted, so that the voltage fluctuation of VM2 at the positive and negative jump time points of the comparator is added and added to be 0, and the high-frequency ripple factor is counteracted. Both VM3 and VM4 can make corrections including phase slope based on VM2, resulting in more accurate phase control.
The sampling feedback of the capacitance current of the output LC filter circuit 4 adopts one of the following modes:
as shown in fig. 13, the output capacitor of the output LC filter circuit 4 is connected in series with the current transformer, and because the output capacitor is only ac, the current transformer can stably operate, but the magnetic element may have a certain nonlinearity, and is not suitable when an extremely low distortion degree is required;
as shown in fig. 14, the output capacitor of the output LC filter circuit 4 is connected in series with a resistor, and the voltage of the resistor is amplified to obtain the current of the capacitor, which has the disadvantages that the resistor has a certain power loss and generates heat, and has a little influence on the output voltage;
as shown in fig. 15, the output capacitor of the output LC filter circuit 4 is connected in parallel with a small capacitor, the small capacitor is connected in series with a resistor and then grounded, and the voltage of the resistor is amplified by a resistor voltage amplifier by several times to be used as an approximate output capacitor current signal. The small capacitor is connected in series with the resistor, and a low-pass filtered signal of the output capacitor current is obtained, and the smaller the resistor is, the smaller the attenuation of high frequency is, so that the small resistor voltage is preferably used for amplification. The practical use of a larger resistor without amplification can also work, and only the attenuation of the high-frequency part of current sampling is more, so that the output impedance parameter is deteriorated.
As shown in fig. 16, the output capacitor of the output LC filter circuit 4 is connected in parallel with a small capacitor, the small capacitor is connected in series with a resistor and then connected to the control output of the preceding stage circuit, the high frequency part of the current signal of the approximate output capacitor is obtained by sampling the signal amplified by the resistor voltage amplifier by several times, and the preceding stage feedback circuit maintains the virtual ground at the lower end of the small capacitor, but the preceding stage circuit only controls the audio part and the high frequency part is also the filter characteristic.
As shown in fig. 17, the output capacitor of the output LC filter circuit 4 is connected in parallel with a small capacitor, the small capacitor current is a mirror image of the output capacitor with a reduced proportion, a virtual ground is formed at the lower end of the small capacitor by using the virtual ground generating and current detecting module to absorb its current, the virtual ground generating and current detecting module outputs an output capacitor current signal, and simultaneously the detection of the current on the small capacitor can be realized.
As shown in fig. 18, in the practical application circuit, in order to operate the current self-excited comparator at about 0 point, the front stage circuit is used to control the output vm (n) series resistor to cancel the low frequency part of the image current, and the remaining high frequency part is absorbed and converted into a high frequency voltage signal by the virtual ground generation and current detection module, and this signal is compared with the hysteresis voltage above and below 0 level to generate a PWM wave.
Specifically, as shown in fig. 19a, the input end of the virtual ground generation and current detection module is externally connected with a low resistance to absorb the external injection current, and the output end outputs the detection value of the external injection current from the input end to obtain an output voltage signal V = K × I, where K is a constant and I is the external injection current.
As shown in fig. 19b and 19c, the virtual ground generation and current detection block may use similar OPA860 chips or transconductance amplifiers to sink current to form a virtual ground and convert the current to a voltage.
The feedback of the capacitance current of the output LC filter circuit 4 includes an output inductive current and a load current, the inductive current feedback provides the dynamic characteristic and stability of the circuit, and the load current feedback makes the output impedance reach an extremely low level.
Since the self-excited oscillation changes the duty ratio along with the increase of the amplitude of the output voltage, and the switching frequency also becomes low greatly, the switching frequency is a function of the output voltage, the output inductance, the power supply voltage and the hysteresis value of the comparator, and the hysteresis value required when the frequency is stable is calculated through the function, the loop of the voltage control module 1 must adapt to the low switching frequency due to the low switching frequency, and the high-frequency phase control becomes complex, the self-excited oscillation frequency adjusting module 7 is adopted in the invention for dynamically adjusting the stability of the switching frequency and greatly improving the circuit performance.
The self-oscillation frequency adjusting module 7 obtains and adjusts a hysteresis value by adopting an analog circuit or through calculation of an MCU, so as to stabilize the frequency, the analog circuit includes an RC filter circuit, the RC filter circuit is connected to an input voltage VIN for replacing an output voltage, and outputs a voltage signal VIN2, the output voltage signal VIN2 can simulate a phase lag of an output voltage OUT with respect to the input voltage VIN, so that the output voltage signal VIN2 can replace the output voltage OUT for calculation, and outputs an absolute value of the voltage signal VIN2 and a power voltage VCC to a function f2(abs (VIN2, VCC), so as to obtain the hysteresis value required when the frequency is stable, and according to the hysteresis value, the frequency is stabilized by a hysteresis amplitude control circuit, wherein the f2(abs (VIN2), VCC) analog circuit can realize that a linear function or a broken line fitting can be used in a simplified manner. The MCU computation implementation may derive an arbitrary f2() function.
The nonlinear distortion of the circuit comes from another aspect in addition to the influence of the high frequency ripple on the control circuit. When the amplitude of the large signal is large, the output voltage OUT is close to the power supply voltage VCC, the output inductive current is not triangular wave any more, but has point circular arc deformation, and the average value of the current peak value no longer represents the average value of the current, so that the complex nonlinear characteristic is generated. The nonlinear compensation module 5 of the invention eliminates the amplitude distortion of the circuit full signal by using an analog circuit or MCU calculation, the analog circuit realizes that VCC can be defaulted to be constant and the fold line method is used for fitting, and the MCU calculation implementation mode can obtain any f1() function.
The analog circuit is provided with an RC filter circuit, the input end of the RC filter circuit is connected with an input voltage VIN, the output end of the RC filter circuit outputs a signal to the nonlinear compensation function circuit, and meanwhile, a power supply voltage VCC is input to the nonlinear compensation function f1(VIN2, VCC) circuit to obtain a compensation value of the circuit, so that the nonlinear distortion of the circuit is eliminated. As shown in fig. 20, in order to simplify the actual circuit, the power supply voltage VCC can be ignored because it is relatively stable, the nonlinear compensation function analog circuit implementation can default that VCC is constant and use a broken line method for fitting, and the circuit implementation is relatively simple.
Claims (8)
1. A low distortion class D power amplifier for use in a high power range, comprising: the circuit is characterized by further comprising a nonlinear compensation module (5) and a self-excited oscillation frequency adjusting module (7), wherein the current self-excited inner ring oscillation circuit consists of a comparator (2) and an output LC capacitance current sampling feedback circuit (6) connected with the comparator (2) in a current feedback mode, the input end of the voltage control module (1) is connected with an input voltage VIN, the output end of the voltage control module outputs a control voltage VM to the input end of the comparator (2), the output end of the comparator (2) is connected with the input end of the MOS switch circuit (3), the output end of the MOS switch circuit (3) is connected with the input end of the output LC filter circuit (4), the output end of the output LC filter circuit (4) is connected with the voltage control module (1), and the capacitance current of the output LC filter circuit (4) is fed back to the output LC capacitance current sampling feedback circuit (6) through the output LC capacitance current sampling feedback circuit (6) A comparator (2); the first input end of the nonlinear compensation module (5) is connected with an input voltage VIN, the second input end of the nonlinear compensation module is connected with a power voltage VCC, and the output end of the nonlinear compensation module outputs a nonlinear compensation function signal to the input end of the comparator (2); and a first input end of the self-oscillation frequency adjusting module (7) is connected with an input voltage VIN, a second input end is connected with a ground power voltage VCC, and an output end is connected with the comparator (2).
2. A low distortion class D power amplifier applied in high power range according to claim 1, characterized in that the voltage control module (1) is provided with a high frequency phase control circuit, said high frequency phase control circuit is provided with a plurality of high frequency zero poles to precisely adjust the phase of the switching frequency point.
3. The low distortion class-D power amplifier applied to high power range according to claim 1, wherein the output LC capacitive current sampling feedback circuit (6) samples and feeds back the capacitive current of the output LC filter circuit (4) by one of the following methods:
a: an output capacitor of the output LC filter circuit (4) is connected with a small capacitor in parallel, the current of the small capacitor is a mirror image of the output capacitor reduced in proportion, a virtual ground is formed at the lower end of the capacitor by using a virtual ground generation and current detection module to absorb the current of the capacitor, and the virtual ground generation and current detection module outputs a current signal of the output capacitor;
b: the output capacitor of the output LC filter circuit (4) is connected with a small capacitor in parallel, the current of the small capacitor is a mirror image of the output capacitor reduced in proportion, a virtual ground is formed at the lower end of the small capacitor by using a virtual ground generation and current detection module to absorb the current of the small capacitor, a resistor is connected in series at the control output end of a front-stage circuit to offset the low-frequency part of the mirror image current, and the virtual ground generation and current detection module outputs a high-frequency part of an output capacitor current signal;
c: an output capacitor of the output LC filter circuit (4) is connected with a current detection sensor, and a sampling current is obtained through detection of the current detection sensor, wherein the current detection sensor comprises a current transformer or a resistor;
d: an output capacitor of the output LC filter circuit (4) is connected with a small capacitor in parallel, the small capacitor is connected with a resistor in series and then grounded, and sampling is amplified by a resistor voltage amplifier for multiple times to obtain an approximate output capacitor current signal;
e: the output capacitor of the output LC filter circuit (4) is connected with a small capacitor in parallel, the small capacitor is connected with a resistor in series and then connected with a preceding stage circuit to control output, and the high-frequency part of the current signal of the approximate output capacitor is obtained by sampling and amplifying the signal by a resistor voltage amplifier by multiple times.
4. The low-distortion class-D power amplifier applied to a high power range according to claim 3, wherein the input end of the virtual ground generation and current detection module is low-resistance to the outside to absorb external injection current, and the output end of the virtual ground generation and current detection module outputs a detection value of the injection current from the input end to obtain an output voltage signal V = K I, wherein K is a constant and I is the external injection current.
5. The low distortion class D power amplifier for high power range as claimed in claim 4 wherein said virtual ground generation and current detection module uses OPA860 chip or transconductance amplifier to sink current to form virtual ground and convert current to voltage.
6. The low-distortion class-D power amplifier applied to a high-power range according to claim 1, wherein the self-oscillation frequency adjusting module (7) obtains and adjusts a hysteresis value by using an analog circuit or by calculation of an MCU, the analog circuit includes an RC filter circuit, the RC filter circuit is connected to an input voltage VIN, an output voltage VIN2 is used for replacing an output voltage OUT signal, an absolute value of the voltage VIN2 and a power voltage VCC to function f2(abs (VIN2), VCC) operation circuit are output, a hysteresis value required when the frequency is stable is obtained, and the frequency is stabilized by a hysteresis amplitude control circuit according to the hysteresis value, wherein the f2(abs (VIN2), VCC) analog circuit realizes fitting by using a linear function or a broken line method.
7. The low-distortion class-D power amplifier applied to the high-power range as claimed in claim 1, wherein the nonlinear compensation module (5) eliminates the full-signal amplitude distortion of the circuit by using an analog circuit or by MCU calculation, the analog circuit is provided with an RC filter circuit, the input end of the RC filter circuit is connected with the input voltage VIN and the output voltage VIN2, and the power voltage VCC is simultaneously input to the nonlinear compensation function f1(VIN2, VCC) circuit to obtain the compensation value of the circuit.
8. The low distortion class-D power amplifier applied to high power range of claim 7, wherein the non-linear compensation function f1(VIN2, VCC) analog circuit implementation uses a zigzag fitting.
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| CN202110175480.5A CN112671353B (en) | 2021-02-09 | 2021-02-09 | Low-distortion class-D power amplifier applied to high-power range |
| PCT/CN2021/078065 WO2022170645A1 (en) | 2021-02-09 | 2021-02-26 | Low-distortion class d power amplifier applied to high-power range |
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| CN202110175480.5A CN112671353B (en) | 2021-02-09 | 2021-02-09 | Low-distortion class-D power amplifier applied to high-power range |
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| CN117134715B (en) * | 2023-10-26 | 2024-01-26 | 苏州仁正智探科技有限公司 | Induction type oil liquid abrasive dust micro-signal two-stage amplification processing system and method |
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| CN112671353B (en) | 2024-02-13 |
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