WO2010025639A1

WO2010025639A1 - Power amplifier and signal processing method thereof

Info

Publication number: WO2010025639A1
Application number: PCT/CN2009/072792
Authority: WO
Inventors: 庞世甫; 刘永平; 谢旺生
Original assignee: 华为技术有限公司
Priority date: 2008-09-04
Filing date: 2009-07-16
Publication date: 2010-03-11
Also published as: CN101350601A

Abstract

A power amplifier and a signal processing method thereof are provided. The power amplifier includes a second-order filter circuit (10), a modulation circuit (20) and an output circuit (30), wherein the output end of the second-order filter circuit is connected with the input end of the modulation circuit, and the output end of the modulation circuit is connected with the input end of the output circuit, and the output end of the output circuit is respectively connected with the input end of each filter circuit stage in the second-order filter circuit. The method includes: the second-order filter circuit sends the signal to the modulation circuit, and the modulation circuit modulates the signal and sends it to the output circuit, and the output circuit outputs the modulation signal and feeds back the signal to the input end of each filter circuit stage in the second-order filter circuit.

Description

A power amplifier and a signal processing method thereof. The present application claims priority to Chinese Patent Application No. 200810146674.7, entitled "A Power Amplifier and Signal Processing Method" thereof, filed on September 4, 2008, the Chinese Patent Office. The entire contents of which are incorporated herein by reference. Technical field

The present invention relates to the field of communications technologies, and in particular, to a power amplifier and a signal processing method thereof. Background technique

With the increasing popularity of portable consumer electronics, the demand for battery operating time is also increasing. Class D amplifiers featuring high efficiency and low distortion are beginning to be widely used in these products. For low-power audio products, such as mobile phones, MP3, MP4, etc., the use of Class D amplifiers can extend the battery life; for high-power audio products, such as multimedia speakers, amplifiers, etc., the use of Class D amplifiers can save heat sinks and use small The specification of the transformer reduces the overall cost of the product while saving energy and environmental protection. Unlike traditional Class AB amplifiers, Class D amplifiers use voltage comparison, pulse width modulation, etc. to amplify the audio signal, so Class D amplifiers are also known as digital power amplifiers.

Modern Class D amplifiers use a variety of modulator topologies, while the most basic topology combines Pulse Width Modulation (PWM) and Triangular (or Sawtooth) oscillators. 1 is a simplified block diagram of a prior art PWM-based half-bridge Class D amplifier. It includes a pulse width modulator PMW, two output metal oxide semiconductor field effect transistors (hereinafter referred to as MOSFETs), and an external low pass filter for recovering the amplified audio signal ( 1^ and C _F ). Among them, p-channel and n-channel MOSFETs are used as current steering switches, and their output nodes are alternately connected to VDD and ground. Since the output transistor switches the output between VDD or ground, the class D amplifier The final output is a high frequency square wave. The switching frequency (/ _sw ) of most Class D amplifiers is typically between 250kHz and 1.5MHz. The audio input signal is pulse width modulated on the output square wave. The audio input signal is compared with a triangular wave (or sawtooth wave) generated by the internal oscillator to obtain a PWM signal. This type of modulation is often referred to as natural sampling, where a triangular wave oscillator acts as a sampling clock. The duty cycle of the square wave is proportional to the input signal level. When there is no input signal, the duty cycle of the output waveform is 50%.

In order to extract the amplified audio signal from the PWM waveform, the output of the amplifier needs to be connected to a low pass filter. The LC low-pass filter in Figure 1 acts as a passive integrator, and its output is equal to the average of the square wave. In addition, the low pass filter prevents high frequency switching energy from being dissipated on the resistive load.

In the process of implementing the present invention, the inventors have found that at least the following problems exist in the prior art: An external LC filter is required in the implementation of the power amplifier. This not only increases the total cost of the solution and board space, but also introduces additional distortion due to the nonlinearity of the filter components. Summary of the invention

Embodiments of the present invention provide a power amplifier and a signal processing method thereof for reducing the cost of a power amplifier and improving the performance of the power amplifier.

An embodiment of the present invention provides a power amplifier, including: a second-order filter circuit, a modulation circuit, and an output circuit, wherein an output end of the second-order filter circuit is connected to an input end of the modulation circuit, and is configured to send a signal to the a modulation circuit; an output end of the modulation circuit is connected to an input end of the output circuit, configured to modulate the signal and output to the output circuit; and an output end of the output circuit and the second order The input end of each of the filter circuits in the filter circuit is connected for outputting according to the modulated signal, and the output signals are respectively fed back to the input end of each of the second-order filter circuits.

Embodiments of the present invention also provide a signal processing method in a power amplifier, which is applied to a power amplifier including a second-order filter circuit, a modulation circuit, and an output circuit, and includes:

The second order filtering circuit sends a signal to the modulation circuit;

The modulation circuit modulates the signal and outputs the signal to the output circuit; The output circuit outputs according to the modulated signal, and feeds the output signal to the input end of each of the second-order filter circuits.

Embodiments of the present invention have the following advantages over the prior art:

By using the embodiment of the present invention, a double feedback second-order filter circuit is adopted, and the signal is denoised by a second-order filter circuit, and then the signal is modulated by the modulation circuit and output through the output circuit, and the double-feedback second-order filter circuit can be effectively utilized. Reducing harmonic distortion and noise generated by the modulation circuit and the output circuit, improving the performance of the power amplifier and reducing the cost of the power amplifier. DRAWINGS

1 is a simplified block diagram of a PWM-based half-bridge Class D amplifier in the prior art;

2 is a schematic diagram of a power amplifier provided in an embodiment of the present invention;

3 is a schematic diagram showing AC characteristics of a power amplifier in an embodiment of the present invention;

4 is a schematic diagram of a PWM modulation output of a power amplifier in an embodiment of the present invention; FIG. 5 is a schematic diagram of a circuit simulation result output VOUT of a power amplifier in an embodiment of the present invention;

6A and 6B are schematic diagrams showing an output DFT test result of a power amplifier in an embodiment of the present invention;

7 is a flow chart of a signal processing method in a power amplifier in an embodiment of the present invention. detailed description

An embodiment of the present invention provides a power amplifier, as shown in Fig. 2, which is a schematic diagram of a power amplifier provided in an embodiment of the present invention, which is composed of a second-order filter circuit 10, a modulation circuit 20, and an output circuit 30. The output end of the second-order filter circuit 10 is connected to the input end of the modulation circuit 20; the output end of the modulation circuit 20 is connected to the input end of the output circuit 30; the output end of the output circuit 30 and each of the second-order filter circuits 10 are respectively filtered. The input is connected. The power amplifier can be a class D power amplifier.

The second-order filter circuit 10 outputs a signal to the modulation circuit 20; the modulation circuit 20 is usually a PWM The modulation circuit generates an output signal by comparing the input signal with a triangular wave or a sawtooth wave (generated by RAMP), and the output signal can be a PWM signal. The PWM signal generated by the modulation circuit 20 is output to the drive stage of the output circuit 30, and the PWM signal is outputted by the output circuit 30. At the same time, the output signal of the output circuit 30 is fed back to the input end of each of the second-order filter circuits 10 to form a closed-loop system, so that the power amplifier has good robustness.

Further, the second-order filter circuit 10 is composed of a first integrator 11 and a second integrator 12, and the differential outputs of the first integrator 11 are respectively invertingly connected to the differential inputs of the second integrator 12. The output signals of the output circuit 30 are fed back to the input terminals of the first integrator 11 and the second integrator 12 in the second-order filter circuit 10, respectively. In addition, in order to ensure the stability of the power amplifier, the SR (Slew Rate) of each integrator in the second-order filter circuit 10 can be set to be smaller than the slope generated by the triangular wave or the sawtooth wave.

Since the driving stages of the modulation circuit 20 and the output circuit 30 are prone to harmonic distortion and noise, the noise of the portion can be noise-shaped by double feedback to the second-order filter circuit 10 to realize a high-performance circuit.

As shown in Fig. 2, the first integrator 11 and the second integrator 12 form a second-order low-pass filter, and the transfer function is:

Y(s) = ^ * ¹ - ₂ X(s) + s R££, _{£ s)} ' 1 + sR ₂ R ₃ / R ₄ + s ¹ R ₂ R ₃ C ₂ / K ' 1 + sR^ / R ₄ + s^^C^ IK ' where is the gain from the PWM modulator. When K = l, the above formula becomes:

Y{ s ) =— * -, ( 5 ) + ^{2 3 1} , ² E(s)

' R _x 1 + IR _A + s ² ^^^ ' 1 + sR^C ^ + s^^C^ ' By changing! The value of ^ can change the gain and transfer function of the power amplifier to achieve volume adjustment.

For the power amplifier shown in Figure 2 above, the behavioral level simulation is performed, with the condition that the input signal has V _m = 1.5V and f = 1kHz. The simulation results are shown in Figure 3, Figure 4 and Figure 5. 3 is a schematic diagram of an AC (Alternating Current) characteristic of a power amplifier in an embodiment of the present invention. As can be seen from FIG. 3, changing the resistance and capacitance in the power amplifier has little effect on the overall performance, indicating that the power amplifier is robust. 4 is a schematic diagram of PWM modulation output of a power amplifier in an embodiment of the present invention, FIG. It is a schematic diagram of the circuit simulation result output VOUT of the power amplifier in the embodiment of the present invention. 6A and FIG. 6B are schematic diagrams showing the output DFT test result of the power amplifier in the embodiment of the present invention, and the output DFT (Disortion-Free Technology) test result of the embodiment of the present invention is 120 dB, which indicates the present invention. The class D power amplifier disclosed in the embodiment has a simple structure and high performance.

Embodiments of the present invention also provide a signal processing method in a power amplifier, which is applied to a power amplifier including a second-order filter circuit, a modulation circuit, and an output circuit, as shown in FIG. 7, which is a power amplifier in an embodiment of the present invention. The flow chart of the signal processing method includes:

Step s701, the second-order filter circuit sends an output signal to the modulation circuit;

Step s702: The modulation circuit modulates the signal and outputs the signal to the output circuit. Step s703: The output circuit outputs according to the modulated signal, and feeds the output signal to each of the second-order filter circuits. The input of the filter circuit.

Wherein, the second-order filter circuit specifically includes a first integrator and a second integrator, wherein the differential outputs of the first integrator are respectively in anti-phase connected to the differential inputs of the second integrator;

The step of feeding back the power output of the output circuit to the input end of each stage of the second stage filter circuit comprises: feeding back the power output of the output circuit to the first integrator and the second integrator Input.

The modulation circuit is a pulse width modulation PWM modulation circuit, and the signal generated by the PWM modulation circuit is a PWM signal. The step of generating the PWM signal by the PWM modulation circuit includes: the PWM modulation circuit comparing an input signal of the second-order filter circuit with a triangular wave or a sawtooth wave signal to generate a PWM signal.

The conversion rate of each integrator in the second-order filter circuit is smaller than the slope generated by the triangular wave or the sawtooth wave.

Wherein, the power amplifier can be a class D power amplifier.

The embodiment of the invention adopts a double feedback second-order filter circuit, and the signal is denoised by a second-order filter circuit, and then the signal is modulated by the modulation circuit and output through the output circuit, and the double-feedback second-order filter circuit can be used to effectively reduce the modulation circuit. Harmonic distortion and noise generated by the output circuit, Improve the performance of the power amplifier and reduce the cost of the power amplifier. In addition, the output of the gate drive output stage circuit is restored from the square wave output by the inductance of the external speaker coil itself and the natural filtering effect of the speaker and the human ear, eliminating the output filter. The embodiment of the invention adopts the double feedback system and the second-order filter circuit to solve the problem that the harmonic distortion of the prior art is relatively large, the design of the latter stage comparator and the driving circuit is not high, the implementation is relatively easy, and the circuit structure is simple. The ability to achieve low distortion, low power consumption, small chip area and good stability, greatly improved performance, greatly reducing the cost of power amplifiers, thus providing a smaller, cheaper and more efficient solution.

The above disclosure is only a few specific embodiments of the present invention, but the present invention is not limited thereto, and any changes that can be considered by those skilled in the art should fall within the protection scope of the present invention.

Claims

Rights request

A power amplifier, comprising: a second-order filter circuit, a modulation circuit, and an output circuit, wherein an output end of the second-order filter circuit is connected to an input end of the modulation circuit, and is configured to send a signal to the a modulation circuit; an output end of the modulation circuit is connected to an input end of the output circuit, configured to modulate the signal and output to the output circuit; and an output end of the output circuit and the second order The input end of each of the filter circuits in the filter circuit is connected for outputting according to the modulated signal, and the output signals are respectively fed back to the input end of each of the second-order filter circuits.

2. The power amplifier according to claim 1, wherein the second-order filter circuit comprises: a first integrator and a second integrator, wherein differential outputs of the first integrator are respectively connected in antiphase to the a differential input of the second integrator, and an output of the output circuit is coupled to an input of the first integrator and an input of the second integrator, respectively.

The power amplifier according to claim 1 or 2, wherein the modulation circuit is a pulse width modulation PWM modulation circuit, and the signal generated by the PWM modulation circuit is a PWM signal.

4. The power amplifier according to claim 3, wherein the PWM modulation circuit compares an input signal of the second-order filter circuit with a triangular wave or a sawtooth wave signal to generate a PWM signal.

The power amplifier according to claim 4, wherein a conversion rate of each of the integrators in the second-order filter circuit is smaller than a slope generated by the triangular wave or sawtooth signal.

6. A signal processing method in a power amplifier, characterized in that it is applied to a power amplifier including a second-order filter circuit, a modulation circuit, and an output circuit, including:

The second order filtering circuit sends a signal to the modulation circuit;

The modulation circuit modulates the signal and outputs the signal to the output circuit;

The output circuit outputs according to the modulated signal, and feeds the output signal to the input end of each of the second-order filter circuits.

The method according to claim 6, wherein when the second-order filter circuit specifically includes a first integrator and a second integrator, the differential outputs of the first integrator are respectively connected in reverse phase to Differential input of the second integrator;

The step of respectively feeding the output signal to the input end of each of the second-order filter circuits is specifically: the output circuit respectively feeding the output signals to the first integrator and the second integrator Input.

The method according to claim 6 or 7, wherein the modulation circuit is a pulse width modulation PWM modulation circuit, and the signal generated by the PWM modulation circuit is a PWM signal.

The method of claim 8, wherein the step of generating the PWM signal by the PWM modulation circuit comprises:

The PWM modulation circuit compares an input signal of the second-order filter circuit with a triangular wave or a sawtooth wave signal to generate a PWM signal.

10. The method of claim 9, wherein a rate of conversion of each integrator in the second order filtering circuit is less than a slope produced by the triangular or sawtooth signal.