CN113162560B - High-power low-distortion class D power amplifier implementation method based on high-performance MCU - Google Patents
High-power low-distortion class D power amplifier implementation method based on high-performance MCU Download PDFInfo
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Abstract
A realization method of a high-power low-distortion class D power amplifier based on a high-performance MCU belongs to the field of audio power amplifiers. The steps are as follows: 1) The input signal mode is selected and displayed. 2) The input signal is preprocessed to obtain audio data. 3) The audio data is transmitted to the STM32F407 minimum system, and PWM is output to the half-bridge driving module. 4) Every two half-bridge driving modules drive a full-bridge power amplifying part to realize the power amplification of small signals. 5) The output of the full-bridge power amplifying section is filtered. 6) And (3) sampling the current of the output passing through the low-pass filter, and feeding back to a minimum system. 7) And setting a digital filter according to the output feedback signal, and filtering the audio data in the step 1). 8) Repeating 2) -7), and realizing negative feedback control of output. The invention solves the problem of instantaneous noise interference of the power-on of the class D power amplifier by using lower cost, and also solves the problem of high requirement on a filter when the switching frequency of the class D power amplifier is low by compensating high frequency through IIR.
Description
Technical Field
The invention belongs to the field of audio power amplification, relates to design and manufacture of a high-performance and convenient man-machine interaction type D audio power amplifier controlled by STM32F407, and particularly relates to a high-performance MCU-based high-power low-distortion type D power amplifier realization method.
Background
The class A and class B power amplifier directly carries out linear amplification on the audio by utilizing a linear amplification region of the power tube, and the voltage is applied to the power tube, so that the power consumption of the power tube is very high. The class D power amplifier is used for comparing an input signal with a triangular wave and then driving a half bridge, and obtaining power amplification after filtering and obtaining audio. The power tube works in a switching state, and compared with linear power amplifiers of class A, class A and class B, the power tube has high efficiency, low loss and small overall volume, and does not need a large-size radiator for heat dissipation. And as the manufacturing process of the field effect tube is mature, the high-performance field effect tube such as GaN, siC and the like is applied to high-power electric appliances, and the green and environment-friendly portable D-type power amplifier has more competitiveness.
Thd+n is an important indicator of the measurement of the audio power amplifier. Most of the integrated power amplifiers on the market at present have extremely small THD under the condition of low power, but the THD of the integrated power amplifier is exponentially increased under the condition of high power, namely the class-D power amplifier and the linear power amplifier. The class D power amplifier takes TDA8920 as an example, the maximum output power of a double channel is 200W, THD is only 0.2% under the power of 1W, and THD is 10% under the maximum power. Class A and class B power amplifier takes LM1875 as an example, the test frequency is 1Khz, the THD is only 0.015% under the condition of 20W power, and the THD exceeds 1% under the condition of 30W. And the class A and class B power amplifier has low efficiency, the maximum efficiency is only 78.5 percent, and extremely large radiating fins are needed during high-power operation. Therefore, the method is not suitable for high-power occasions whether the D-class set is successfully put or the A-class set is successfully put, has poor man-machine interaction performance, and cannot directly carry out digital processing on amplified audio.
The design directly carries out operation processing on the audio signal by utilizing the data processing capacity of the STM32F407 minimum system. And comparing the input audio signal with the triangular wave of the advanced timer, outputting PWM with complementary dead zone, and driving the field effect transistor. In order to make the power amplifier have higher performance under high power, a discrete field effect transistor is selected as a power tube, so that the power of the power tube is doubled compared with the traditional integrated D-type power amplifier, and meanwhile, the THD is smaller, and the audio amplification is more accurate.
For example, li Yangchun, etc. (CN 104270105A) is a digital power amplifier circuit, which processes signals by separating high and low tones to drive class AB and class D power amplifiers respectively, the amplitude-frequency flatness is not high, and the output signal is connected to an integrated class D power amplifier circuit, which is not suitable for high-power occasions, has low efficiency and single input mode, and is difficult to meet the requirement of multi-mode audio input. In view of the foregoing, there is a need for a class D power amplifier implementation method that supports multiple output modes by a high performance MCU, outputs PWM to directly drive a full-bridge circuit, and compensates for audio treble to make its amplitude-frequency characteristics flat.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a method for realizing a high-power low-distortion D-class power amplifier based on a high-performance MCU.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the implementation method is based on a system module, wherein the system module comprises an STM32F407 minimum system, an audio Bluetooth module, an SD card module, a U disk module, a half-bridge driving module, a MOSFET full-bridge power amplifying part, an LCD display module, an audio analog signal amplifying module, a word stock storage module, a voltage reduction auxiliary power supply system, a current sampling module, an IIR digital filter, a diaphragm loudspeaker and a plasma loudspeaker. The audio Bluetooth module is connected with the STM32F407 minimum system through an I2S communication protocol, the SD card module is connected with the STM32F407 minimum system through an SDIO, the U disk module is connected with the STM32F407 minimum system through a USB bus, and the audio analog signal amplification module is connected with the STM32F407 minimum system through an ADC. The half-bridge driving module is connected with the STM32F407 minimum system. The full-bridge power amplification part is input with a driving signal by the half-bridge driving module, is connected with the INA282 current sampling module after passing through the low-pass filter, is connected with the vibrating diaphragm loudspeaker, and is communicated with the STM32F407 minimum system through the IIR digital filter; the full-bridge power amplifying part is also connected with the plasma loudspeaker through a high-pass filter. The word stock storage module is connected with the STM32F407 minimum system through SPI. The step-down auxiliary power supply system comprises a 3.3V step-down auxiliary power supply system, a 5V step-down auxiliary power supply system and a 2V step-down auxiliary power supply system, wherein 3.3V output by the 3.3V step-down auxiliary power supply system is supplied by an STM32F407 minimum system, an SD card module, an LCD touch display module, a word stock storage module, an audio analog signal amplifying module and an INA282 current sampling module; the 5V step-down auxiliary power supply system outputs 5V to supply power to the step-down auxiliary power supply module, the U disk module, the audio Bluetooth module and the half-bridge driving module; the 12V step-down auxiliary power supply system outputs 12V to supply power for the step-down auxiliary power supply system and the half-bridge driving module. The implementation method specifically comprises the following steps:
first, selecting and displaying a playing mode.
Firstly, the LCD touch display module is used for selecting and displaying the input signal mode. The input signal mode comprises four modes of USB flash disk input, SD card input, analog audio signal input and audio Bluetooth input. The Chinese character display is that a word stock storage module is communicated with an STM32F407 minimum system to obtain a word stock, and the word stock is displayed on an LCD touch display module.
And secondly, preprocessing the input signal.
2.1 The USB flash disk module is communicated with an STM32F407 minimum system through a USB bus, four file formats of WAV, MP3, FLAC and APE are read by using a FATFS file management system, and audio data in a PCM format are obtained after the audio data are passed through corresponding digital decoders.
2.2 Inputting an SD card, communicating the SD card module with an STM32F407 minimum system through SDIO, reading four file formats of WAV, MP3, FLAC and APE by using a FATFS file management system, and obtaining the audio data in the PCM format after the audio data passes through a corresponding digital decoder.
2.3 Analog audio signal is input, and after the audio signal is amplified for the first time and biased by the audio analog signal amplifying module, the audio signal can be sampled by the singlechip ADC of the STM32F407 minimum system to the maximum extent, and the audio data in the PCM format is formed after multiplying the corresponding proportionality coefficient.
2.4 For audio Bluetooth input, the singlechip obtains input data of the audio Bluetooth module through IIS communication, and stores the data into a memory to obtain a PCM audio data format.
And thirdly, loading the PCM audio data obtained in the second step in a timer of an STM32F407 minimum system. Initializing a timer, and setting the frequency, channel, dead time and output polarity of the output PWM; and transmitting the audio data processed in the second step to a timer, and outputting PWM to a half-bridge driving module. And transmitting the PCM audio data to two channels of the timer, wherein the two channels respectively correspond to the audio frequencies of the left and right channels, and each timer channel outputs signals to two half-bridge driving modules.
And step four, driving a full-bridge power amplifying part by every two half-bridge driving modules. The full-bridge power amplification part comprises four half-bridges, each two half-bridges form a full-bridge, namely the full-bridge power amplification part comprises two full-bridges, and the output of the two full-bridges is the power amplification of left and right sound channels. Every two half-bridge driving modules drive one full bridge in the full-bridge power amplifying part through a grid driving resistor and a diode connected in parallel with the grid driving resistor, and finally, the power amplification of small signals is realized.
And fifthly, filtering the output of the full-bridge power amplification part.
The high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are respectively input into the diaphragm loudspeaker and the plasma loudspeaker:
when the high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are connected to the diaphragm loudspeaker, a low-pass filter is needed to be used for filtering the high-frequency carrier wave and the low-frequency modulation signal so as to enhance the efficiency, and finally, the audio playing is realized;
when the output high-frequency carrier wave and the low-frequency modulation signal of the full-bridge power amplification part are connected to the plasma loudspeaker, a high-pass filter is needed to filter the output high-frequency carrier wave and the low-frequency modulation signal, so that the low-frequency power consumption can be reduced, and the plasma is generated by breakdown air to realize the function of the plasma loudspeaker.
And sixthly, adopting an INA282 current sampling module to sample the current of the output which passes through the low-pass filter in the fifth step, and feeding back to the STM32F407 minimum system. Specific: and (3) carrying out current sampling on the output subjected to low-pass filtering by using an INA282 current sampling module, and feeding the output back to a singlechip ADC of an STM32F407 minimum system to finally obtain an output feedback signal.
And seventh, setting an IIR digital filter according to the output feedback signal of the sixth step, so as to filter the PCM audio data generated in the first step.
7.1 And (3) carrying out Fourier transform on the PCM audio data generated in the first step to finally obtain the amplitude-frequency characteristic of the input signal. The amplitude-frequency characteristic can display music frequency spectrum through the LCD touch display module.
7.2 And (3) carrying out Fourier transform on the output feedback signal in the sixth step to obtain the amplitude-frequency characteristic of the output signal.
7.3 Comparing the output feedback signal after Fourier transformation with the amplitude of the PCM audio data generated in the first step on each frequency to obtain the transfer function of the low-pass filter.
7.4 Determining parameters of the IIR digital filter from the transfer function of the low pass filter.
7.5 The audio data in the 16-bit PCM format obtained in the first step is processed by adopting an IIR digital filter, so that corrected audio data is obtained, the amplitude-frequency characteristic of the audio data after the audio data passes through a low-pass filter is flatter, and namely, a high-pitch part is enhanced.
And eighth step, repeating the third step to the seventh step to realize negative feedback control of output.
The beneficial effects of the invention are as follows:
(1) Frequency domain negative feedback is added, so that amplitude-frequency characteristics are flat, and the requirements on a filter are reduced.
(2) The discrete device is used, so that the power tube works independently, the efficiency is higher, and the power is greatly improved.
(3) The single chip microcomputer is adopted for direct control, no noise is generated at the moment of power-on, and the signal processing capability is stronger.
(4) The distortion is smaller in the high-power occasion, and the total harmonic distortion is within 1% under the power of 100W.
(5) The input modes are various, and the application occasions are wider.
(6) The man-machine interaction is strong, the touch screen is arranged, the Chinese character library is arranged, and the USB flash disk and the SD card can be read and written.
(7) The full-bridge topology is used, a single power supply is used for supplying power, and the power utilization rate is high.
Drawings
FIG. 1 is a schematic diagram of a system for implementing the method of the present invention.
Detailed Description
The invention is further illustrated below with reference to specific examples.
The implementation method is based on a system module, wherein the system module comprises an STM32F407 minimum system, a step-down auxiliary power supply, an audio Bluetooth module, an SD card module, a U disk module, a half-bridge driving module, a MOSFET full-bridge power amplifying part, an LCD display module, an audio analog signal amplifying module, a word stock storage module, a step-down auxiliary power supply system, a current sampling module, an IIR digital filter, a diaphragm loudspeaker and a plasma loudspeaker. The audio Bluetooth module is connected with the STM32F407 minimum system through an I2S communication protocol, the SD card module is connected with the STM32F407 minimum system through an SDIO, the U disk module is connected with the STM32F407 minimum system through a USB bus, and the audio analog signal amplification module is connected with the STM32F407 minimum system through an ADC. The half-bridge driving module is connected with the STM32F407 minimum system. The full-bridge power amplification part is input with a driving signal by the half-bridge driving module, is connected with the INA282 current sampling module after passing through the low-pass filter, is connected with the vibrating diaphragm loudspeaker, and is communicated with the STM32F407 minimum system through the IIR digital filter; the full-bridge power amplifying part is also connected with the plasma loudspeaker through a high-pass filter. The word stock storage module is connected with the STM32F407 minimum system through SPI. The step-down auxiliary power supply system comprises a 3.3V step-down auxiliary power supply system, a 5V step-down auxiliary power supply system and a 2V step-down auxiliary power supply system, wherein 3.3V output by the 3.3V step-down auxiliary power supply system is supplied by an STM32F407 minimum system, an SD card module, an LCD touch display module, a word stock storage module, an audio analog signal amplifying module and an INA282 current sampling module; the 5V step-down auxiliary power supply system outputs 5V to supply power to the step-down auxiliary power supply module, the U disk module, the audio Bluetooth module and the half-bridge driving module; the 12V step-down auxiliary power supply system outputs 12V to supply power for the step-down auxiliary power supply system and the half-bridge driving module. The implementation method specifically comprises the following steps:
first, selecting and displaying a playing mode.
Firstly, the LCD touch display module is used for selecting and displaying the input signal mode. The input signal mode comprises four modes of USB flash disk input, SD card input, analog audio signal input and audio Bluetooth input. The Chinese character display is that a word stock storage module is communicated with an STM32F407 minimum system to obtain a word stock, and the word stock is displayed on an LCD touch display module.
And secondly, preprocessing the input signal.
2.1 The USB flash disk module is communicated with an STM32F407 minimum system through a USB bus, four file formats of WAV, MP3, FLAC and APE are read by using a FATFS file management system, and audio data in a PCM format are obtained after the audio data are passed through corresponding digital decoders.
2.2 Inputting an SD card, communicating the SD card module with an STM32F407 minimum system through SDIO, reading four file formats of WAV, MP3, FLAC and APE by using a FATFS file management system, and obtaining the audio data in the PCM format after the audio data passes through a corresponding digital decoder.
2.3 The analog audio signal is input, and after the audio signal is amplified for the first time and biased by the audio analog signal amplifying module, the audio signal can be sampled by the singlechip ADC of the STM32F407 minimum system to the maximum extent, and the audio data in a 16-bit PCM format is formed after multiplying the audio signal by the corresponding proportionality coefficient.
2.4 For audio Bluetooth input, the singlechip obtains input data of the audio Bluetooth module through IIS communication, and stores the data into a memory to obtain a 16-bit PCM audio data format.
Third, 16-bit PCM audio data is loaded in the timer of the STM32F407 minimum system. Initializing a timer, and setting the frequency, channel, dead time and output polarity of the output PWM; and transmitting the audio data processed in the second step to a timer to output PWM to a half-bridge driving module. And the 16-bit PCM is sent to two channels of the timer, the two channels respectively correspond to the audio frequency of the left channel and the audio frequency of the right channel, and each timer channel outputs signals to two half-bridge driving modules.
And step four, driving a full-bridge power amplifying part by every two half-bridge driving modules. The full-bridge power amplification part comprises four half-bridges, each two half-bridges form a full-bridge, namely the full-bridge power amplification part comprises two full-bridges, and the output of the two full-bridges is the power amplification of left and right sound channels. Every two half-bridge driving modules drive one full bridge in the full-bridge power amplifying part through a grid driving resistor and a diode connected in parallel with the grid driving resistor, and finally, the power amplification of small signals is realized.
And fifthly, filtering the output of the full-bridge power amplification part.
The high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are respectively input into the diaphragm loudspeaker and the plasma loudspeaker:
when the high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are connected to the diaphragm loudspeaker, a low-pass filter is needed to be used for filtering the high-frequency carrier wave and the low-frequency modulation signal so as to enhance the efficiency, and finally, the audio playing is realized;
when the output high-frequency carrier wave and the low-frequency modulation signal of the full-bridge power amplification part are connected to the plasma loudspeaker, a high-pass filter is needed to filter the output high-frequency carrier wave and the low-frequency modulation signal, so that the low-frequency power consumption can be reduced, and the plasma is generated by breakdown air to realize the function of the plasma loudspeaker.
And sixthly, adopting an INA282 current sampling module to sample the current of the output after low-pass filtering of the low-pass filter, and feeding the output back to a singlechip ADC of an STM32F407 minimum system to finally obtain an output feedback signal.
And seventh, setting an IIR digital filter according to the output feedback signal of the sixth step, so as to filter the PCM audio data generated in the first step.
7.1 And (3) carrying out Fourier transform on the PCM audio data generated in the first step to finally obtain the amplitude-frequency characteristic of the input signal. The amplitude-frequency characteristic can display music frequency spectrum through the LCD touch display module.
7.2 And (3) carrying out Fourier transform on the output feedback signal in the sixth step to obtain the amplitude-frequency characteristic of the output signal.
7.3 Comparing the output feedback signal after Fourier transformation with the amplitude of the PCM audio data generated in the first step on each frequency to obtain the transfer function of the low-pass filter.
7.4 Determining parameters of the IIR digital filter from the transfer function of the low pass filter.
7.5 The audio data in the 16-bit PCM format obtained in the first step is processed by adopting an IIR digital filter, so that corrected audio data is obtained, the amplitude-frequency characteristic of the audio data after the audio data passes through a low-pass filter is flatter, and namely, a high-pitch part is enhanced.
And eighth step, repeating the third step to the seventh step to realize negative feedback control of output.
The examples described above represent only embodiments of the invention and are not to be understood as limiting the scope of the patent of the invention, it being pointed out that several variants and modifications may be made by those skilled in the art without departing from the concept of the invention, which fall within the scope of protection of the invention.
Claims (2)
1. The implementation method is characterized in that the implementation method is based on a system module, wherein the system module comprises an STM32F407 minimum system, a step-down auxiliary power supply system, an audio Bluetooth module, an SD card module, a U disk module, a half-bridge driving module, a MOSFET full-bridge power amplifying part, an LCD display module, an audio analog signal amplifying module, a word stock storage module, a current sampling module, an IIR digital filter, a diaphragm loudspeaker and a plasma loudspeaker; the audio Bluetooth module is connected with the STM32F407 minimum system through an I2S communication protocol, the SD card module is connected with the STM32F407 minimum system through an SDIO, the U disk module is connected with the STM32F407 minimum system through a USB bus, and the audio analog signal amplification module is connected with the STM32F407 minimum system through an ADC; the half-bridge driving module is connected with an STM32F407 minimum system; the full-bridge power amplification part is input with a driving signal by the half-bridge driving module, is connected with the INA282 current sampling module after passing through the low-pass filter, is connected with the vibrating diaphragm loudspeaker, and is communicated with the STM32F407 minimum system through the IIR digital filter; the full-bridge power amplifying part is also connected with a plasma loudspeaker through a high-pass filter; the word stock storage module is connected with the STM32F407 minimum system through the SPI; the step-down auxiliary power supply system supplies power for the whole system; the method comprises the following steps:
firstly, selecting and displaying a playing mode;
selecting and displaying an input signal mode through an LCD touch display module;
step two, preprocessing an input signal to obtain audio data;
thirdly, loading the PCM audio data obtained in the second step in a timer of an STM32F407 minimum system; initializing a timer, and setting the frequency, channel, dead time and output polarity of the output PWM; transmitting the audio data processed in the second step to a timer, and outputting PWM to a half-bridge driving module; the PCM audio data are transmitted to two channels of a timer, the two channels respectively correspond to the audio of the left channel and the right channel, and each timer channel outputs signals to two half-bridge driving modules;
step four, driving a full-bridge power amplifying part by every two half-bridge driving modules; the full-bridge power amplification part comprises two full bridges, and the output of the two full bridges is the power amplification of left and right sound channels; every two half-bridge driving module driving resistors and diodes connected in parallel drive one full bridge in the full-bridge power amplifying part, so that power amplification of small signals is realized;
fifthly, filtering the output of the full-bridge power amplifying part;
the high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are respectively input into the diaphragm loudspeaker and the plasma loudspeaker:
when the high-frequency carrier wave and the low-frequency modulation signal output by the full-bridge power amplification part are connected to the diaphragm loudspeaker, a low-pass filter is needed to be used for filtering the high-frequency carrier wave and the low-frequency modulation signal;
when the output high-frequency carrier wave and the low-frequency modulation signal of the full-bridge power amplification part are connected to the plasma loudspeaker, a high-pass filter is needed to filter the output high-frequency carrier wave and the low-frequency modulation signal;
sixthly, adopting an INA282 current sampling module to sample the current of the output of the low-pass filter in the fifth step, and feeding back to the STM32F407 minimum system;
a seventh step of setting an IIR digital filter according to the sixth step of outputting a feedback signal, and filtering PCM audio data generated in the first step;
7.1 Performing Fourier transform on the PCM audio data generated in the first step to obtain amplitude-frequency characteristics of the input signal; the amplitude-frequency characteristic can display music frequency spectrum through the LCD touch display module;
7.2 Performing Fourier transform on the output feedback signal of the sixth step to obtain amplitude-frequency characteristics of the output signal;
7.3 Comparing the output feedback signal after Fourier transformation with the amplitude of the PCM audio data generated in the first step on each frequency to obtain the transfer function of the low-pass filter;
7.4 Determining parameters of the IIR digital filter according to the transfer function of the low-pass filter;
7.5 Processing the 16-bit PCM format audio data obtained in the first step by adopting an IIR digital filter to obtain corrected audio data, so that the amplitude-frequency characteristic of the audio data after the audio data passes through a low-pass filter is flatter, namely, a high-pitch part is enhanced;
and eighth step, repeating the third step to the seventh step to realize negative feedback control of output.
2. The method for implementing the high-power low-distortion class D power amplifier based on the high-performance MCU of claim 1, wherein in the second step, the preprocessing of the input signal is specifically:
2.1 Input to the U disk): the U disk module is communicated with an STM32F407 minimum system, a FATFS file management system is used for reading four file formats of WAV, MP3, FLAC and APE, and audio data in a PCM format is obtained after the audio data passes through a digital decoder;
2.2 Input to SD card): the SD card module communicates with the STM32F407 minimum system through SDIO, reads four file formats of WAV, MP3, FLAC and APE by using a FATFS file management system, and obtains audio data in a PCM format after the audio data passes through a digital decoder;
2.3 Analog audio signal input: the audio analog signal amplifying module is used for performing primary amplification and biasing on the audio signal to form audio data in a PCM format;
2.4 For audio bluetooth input): the singlechip obtains input data of the audio Bluetooth module through IIS communication, stores the data into the memory, and obtains a PCM audio data format.
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