A Class D Audio Power Amplifier and a Signal Compression Method

Abstract

The present invention is applicable to the technical field of audio power amplifiers, and provides a class D audio power amplifier and a signal compression method. The class D audio power amplifier includes: a controllable limiter, a class D amplifier, a first filter, a second filter, and a logic control module. In the present application, when an abnormal signal appears in the filtered signal, the logic control module compresses the filtered signal to reduce the amplitude of the abnormal signal in the filtered signal, that is, the compression processing of the abnormal signal effectively reduces the compression and distortion phenomenon of the class D audio power amplifier when processing low-frequency signals, improves the sound quality performance of the audio amplifier, and the audio power amplifier device is smaller in size and lighter in weight, which is easy to carry and install. In addition, the circuit structure of the present application has high energy conversion efficiency, which can effectively reduce the energy consumption of the power amplifier device and reduce the waste of electric energy, while reducing heat generation, reducing heat dissipation requirements, and improving the stability and life of the equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of audio power amplifiers, and in particular relates to a class D audio power amplifier and a signal compression method. Background Art

[0002] Class D audio amplifier refers to an audio amplifier device that uses Class D amplification technology. Traditional Class AB amplifiers consume power continuously when amplifying signals, resulting in relatively low efficiency and generating more heat. Class D amplifiers use PWM (pulse width modulation) technology to achieve high-efficiency power amplification by converting audio signals into pulse sequences and then controlling them with switching tubes at the output. This technology makes Class D amplifiers more energy-efficient and lighter than traditional Class AB amplifiers at the same power output, while reducing heat dissipation requirements, making the equipment more compact and reliable.

[0003] Class D audio amplifiers are widely used in audio systems, car audio, home theaters, and other fields. Its main advantages include high efficiency, low power consumption, and small size. The main structure of this amplifier includes input filter, power amplifier, and output filter. Its working principle is to amplify the input audio signal through the amplifier and then output it to drive the speaker to produce sound. Two important parameters of audio signals are the distribution of signal level over time and frequency, which is at a low level most of the time and the peak of the dynamic range is relatively small.

[0004] Although Class D audio amplifiers have the advantages of high efficiency and low power consumption, they will experience distortion and overload when processing high-amplitude sinusoidal signals. For example, due to the limited switching speed of the switch tube, it cannot fully follow the changes in the low-frequency signal, resulting in compression and distortion of the output signal. When processing low frequencies, more high-order harmonics will be generated, further increasing the distortion of the output signal, resulting in reduced sound quality and power loss. Although existing signal processing technology can alleviate this problem to a certain extent, it still has disadvantages such as poor effect and high complexity. Therefore, it needs to be improved. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a Class D audio amplifier, aiming to solve the problem that the existing Class D audio amplifier will experience distortion and overload when processing high-amplitude sinusoidal signals, resulting in reduced sound quality and power loss. Although the existing signal processing technology can alleviate this phenomenon to a certain extent, it still has disadvantages such as poor effect and high complexity.

[0006] The embodiment of the present application is implemented by providing a class D audio power amplifier, the class D audio power amplifier comprising:

[0007] A controllable limiter, a class D amplifier, a first filter, a second filter and a logic control module;

[0008] The controllable limiter is provided with an audio signal input terminal for receiving an audio signal input; the signal output terminal of the controllable limiter is connected to the class D amplifier;

[0009] The output end of the class D amplifier is connected to the first filter, and the class D amplifier is used to amplify the audio signal input from the controllable limiter to generate a PWM pulse signal;

[0010] The first filter is used to filter the PWM pulse signal output by the class D amplifier, convert it into an analog quantity, obtain a filtered signal, and input the filtered signal to the load end;

[0011] The input end of the logic control module is used to receive the filter signal. When an abnormal signal appears in the filter signal, the filter signal is compressed to reduce the amplitude of the abnormal signal in the filter signal to generate a control signal.

[0012] The second filter is connected to the logic control module and the controllable limiter, and is used for converting the control signal into a quantization / error signal input of the controllable limiter to adjust the signal output of the controllable limiter.

[0013] Preferably, the class D amplifier comprises a class D modulation stage and a class D terminal amplifier stage, the class D modulation stage is used to convert the electrical signal input by the controllable limiter into a pulse signal, and the class D terminal amplifier stage is used to amplify the voltage and / or current of the pulse signal;

[0014] The logic control module is also used to connect to the class D modulation stage and to enable and control the class D modulation stage.

[0015] Preferably, the class D audio power amplifier further includes a power module;

[0016] The power supply module is a high-frequency AC power supply, which is used for voltage transformation and outputting AC voltage to each module in the Class D audio power amplifier for power supply.

[0017] Preferably, the class D audio power amplifier further includes a preamplifier module;

[0018] The pre-amplification module is arranged between the controllable limiter and the audio signal input terminal, and is used for preprocessing the audio signal input to the controllable limiter and changing the gain of the signal.

[0019] Preferably, the class D audio power amplifier further comprises a load connected to the first filter, and the load is a speaker;

[0020] The logic control module is used to perform temperature detection on the load, and is also used to perform voltage sampling, current sampling and short circuit detection on the filtered signal input to the load.

[0021] Another object of the embodiment of the present application is to provide a signal compression method, wherein the signal processing method is implemented based on the logic control module in the class D audio power amplifier as described above, and is used to perform signal processing on the filtered signal;

[0022] The method comprises the following steps:

[0023] S10: continuously sampling the filtered signal output by the first filter to obtain a sampled signal;

[0024] S20: When an abnormal signal is detected in the sampled signal, timing the duration of the abnormal signal;

[0025] S30: When the duration of the abnormal signal exceeds the first threshold, or when an abnormal low-frequency DC signal is detected after sampling the signal, the Class D audio power amplifier is controlled to compress its output power to a first limit level;

[0026] S40: After the output power of the class D audio power amplifier is compressed to the first limit level, the voltage value of the sampled signal is determined:

[0027] If the sampled signal obtained by sampling returns to normal, the output power compression of the Class D audio power amplifier is stopped;

[0028] If the sampled signal still has an abnormal signal output, and the output duration of the abnormal signal exceeds the second threshold, the output power of the Class D audio amplifier is compressed to the second limit level and maintained at the second limit level until the sampled signal returns to normal.

[0029] Preferably, the abnormal signal is one or more of the following signal characteristics:

[0030] Maximum level output signals, abnormal DC signals, and abnormal very low frequency signals.

[0031] Preferably, the first threshold is 10 seconds, and the second threshold is 15 seconds;

[0032] The first limit level is 1 / 2, and the second limit level is 1 / 4.

[0033] Preferably, the signal compression method further comprises:

[0034] If the number of times that the class D audio power amplifier is compressed to the first limit level exceeds the warning number within a preset time period, the class D audio power amplifier is controlled to stop working.

[0035] Preferably, the signal compression method further comprises:

[0036] When the stop time of the class D audio power amplifier being stopped due to the number of times exceeding the first limit level being higher than the warning number reaches the stop time threshold, the class D audio power amplifier is controlled to restart.

[0037] The Class D audio amplifier provided in the embodiment of the present application has the following outstanding advantages: the circuit structure of the present application has high energy conversion efficiency, can effectively reduce the energy consumption of the amplifier device, reduce the waste of electric energy, and at the same time reduce the heat generation, reduce the heat dissipation requirements, and improve the stability and life of the equipment. After an abnormal signal appears in the filter signal part of the logic circuit in the present application, the logic control module will compress the filter signal to reduce the amplitude of the abnormal signal in the filter signal, that is, the compression processing of the abnormal signal effectively reduces the compression and distortion of the Class D audio amplifier when processing low-frequency signals, and improves the sound quality performance of the audio amplifier. The audio amplifier device is smaller in overall size, lighter in weight, simple in structure, and easy to carry and install. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A connection diagram of a Class D audio amplifier module provided in an embodiment of the present application;

[0039] Figure 2 A circuit diagram of a second filter provided in an embodiment of the present application;

[0040] Figure 3 A working principle diagram of a first filter provided in an embodiment of the present application;

[0041] Figure 4 A flowchart of a signal compression method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, a first script may be referred to as a second script, and similarly, a second script may be referred to as a first script without departing from the scope of this application.

[0044] like Figure 1 As shown, in one embodiment, a class D audio power amplifier comprises:

[0045] A controllable limiter, a class D amplifier, a first filter, a second filter and a logic control module;

[0046] The controllable limiter is provided with an audio signal input terminal for receiving an audio signal input; the signal output terminal of the controllable limiter is connected to the class D amplifier;

[0047] The output end of the class D amplifier is connected to the first filter, and the class D amplifier is used to amplify the audio signal input from the controllable limiter to generate a PWM pulse signal;

[0048] The first filter is used to filter the PWM pulse signal output by the class D amplifier, convert it into an analog quantity, obtain a filtered signal, and input the filtered signal to the load end;

[0049] The input end of the logic control module is used to receive the filter signal. When an abnormal signal appears in the filter signal, the filter signal is compressed to reduce the amplitude of the abnormal signal in the filter signal to generate a control signal.

[0050] The second filter is connected to the logic control module and the controllable limiter, and is used for converting the control signal into a quantization / error signal input of the controllable limiter to adjust the signal output of the controllable limiter.

[0051] In one embodiment of the present application, a high-power high-frequency switching power supply can be used as an energy source, and the direct current is converted into high-frequency alternating current through the working principle of the high-frequency switching power supply, and after filtering and adjustment, it is input to the class D output stage. The class D output stage adopts a high-efficiency amplifier design, which can amplify the input audio signal and output it to a speaker or other output device under the drive of the high-frequency switching power supply. Such a design enables the present invention to achieve the advantages of small size, light weight, low heat generation and wide dynamic range while maintaining high efficiency.

[0052] In the embodiment of the present application, the second filter may be a quantization / error filter, which can convert the PID (proportional integral differential) adjustment output of the first filter and the logic control module into a quantization / error signal input of the controllable limiter, thereby adjusting the output of the limiter. The circuit diagram structure is as follows Figure 2 shown.

[0053] In the embodiment of the present application, the first filter can be a high-voltage and high-current PWM filter, which can convert PWM pulses into audio signals. The principle can be as follows Figure 3 As shown in the figure, the digital signal is converted into an analog signal and the audio is output. For example, a sine wave is input to the speaker load.

[0054] In this embodiment, the abnormal signal can be a variety of abnormal audio signals, for example, a level signal with a continuous output voltage value of the maximum amplitude, or an audio signal with a DC level, or an extremely low AC frequency (for example, 20HZ), or a DC low-frequency signal appearing at the first filter after being amplified by this system, or 50Hz / 60Hz AC power supply noise caused by a suspended ground wire, etc.

[0055] In one embodiment of the present application, the audio power amplifier device can be mainly composed of the following components: High-frequency switching power supply: Provides an energy source for power output, adopts high-frequency switching power supply technology, realizes the switching and regulation of the power supply through the power control module, and outputs stable high-frequency alternating current. Power filter: Filters the current output by the high-frequency switching power supply to remove stray frequencies and ensure the stability and purity of the power output. Class D output stage: Responsible for amplifying and processing the input audio signal, adopts a high-efficiency Class D amplifier design, and amplifies the input signal and outputs it to a speaker or other output device. Logic control module: Controls the working state of the entire audio power amplifier device, including the switching and regulation of the high-frequency switching power supply, the control and protection of the Class D output stage, and other functions. These components are connected together through circuit boards and connecting wires to form the structure of the entire audio power amplifier device. Its working principle is that the high-frequency switching power supply provides stable energy, the filter performs filtering processing on it, the Class D output stage amplifies the input audio signal, and finally outputs the processed signal to the speaker or other output device, thereby realizing the amplification and playback of the audio signal.

[0056] The present application effectively reduces the compression and distortion of the Class D audio amplifier when processing low-frequency signals through compression processing for abnormal signals, thereby improving the sound quality performance of the audio amplifier. The compression method adopted in the present application can maintain the dynamic range of the audio signal, reduce the degree of compression of the signal, and make the audio output richer and more dynamic. The Class D output stage design has a strong overload capacity, can stably output high-power signals, and adapt to various complex audio scenes. Compared with mainstream products in the traditional market, the audio power amplifier device of the present application is smaller in size and lighter in weight, easy to carry and install, and suitable for the needs of various occasions. In addition, the present application has a high energy conversion efficiency, can effectively reduce the energy consumption of the power amplifier device, reduce the waste of electric energy, and at the same time reduce the heat generation, reduce the heat dissipation requirements, and improve the stability and life of the equipment. The audio power amplifier device can reduce energy consumption, reduce the waste of electric energy, achieve the purpose of energy saving and environmental protection, and at the same time reduce pollution to the environment.

[0057] In a preferred embodiment, the Class D amplifier includes a Class D modulation stage and a Class D terminal amplifier stage, the Class D modulation stage is used to convert the electrical signal input by the controllable limiter into a pulse signal, and the Class D terminal amplifier stage is used to amplify the voltage and / or current of the pulse signal; the logic control module is also used to connect to the Class D modulation stage for enabling control of the Class D modulation stage.

[0058] In a preferred embodiment, the class D audio power amplifier further includes a power module; the power module is a high-frequency AC power supply, which is used for voltage transformation and outputting AC voltage to each module in the class D audio power amplifier for power supply.

[0059] In a preferred embodiment, the class D audio amplifier also includes a pre-amplifier module; the pre-amplifier module is arranged between the controllable limiter and the audio signal input terminal, and is used to pre-process the audio signal input to the controllable limiter and change the gain of the signal.

[0060] In a preferred embodiment, the Class D audio amplifier also includes a load connected to the first filter, and the load is a speaker; the logic control module is used to perform temperature detection on the load, and is also used to perform voltage sampling, current sampling and short circuit detection on the filtered signal input to the load.

[0061] In the embodiment of the present application, the logic control module can also perform temperature detection. When the temperature is abnormal, the control amplifier is turned off; when the temperature is normal, the control amplifier is restarted.

[0062] In a preferred embodiment, the load is a speaker, and may also be an audio output port for connecting other audio circuits.

[0063] In an embodiment of the present application, a signal compression method is provided. The signal processing method is implemented based on the logic control module in the class D audio amplifier as described above, and is used to compress the filtered signal.

[0064] The method comprises the following steps:

[0065] S10: continuously sampling the filtered signal output by the first filter to obtain a sampled signal;

[0066] S20: When an abnormal signal is detected in the sampled signal, timing the duration of the abnormal signal;

[0067] S30: When the duration of the abnormal signal exceeds the first threshold, or when an abnormal low-frequency DC signal is detected after sampling the signal, the Class D audio power amplifier is controlled to compress its output power to a first limit level;

[0068] S40: After the output power of the class D audio power amplifier is compressed to the first limit level, the voltage value of the sampled signal is determined:

[0069] If the sampled signal obtained by sampling returns to normal, the output power compression of the class D audio power amplifier is stopped.

[0070] If the sampled signal still has an abnormal signal output, and the output duration of the abnormal signal exceeds the second threshold, the output power of the Class D audio amplifier is compressed to the second limit level and maintained at the second limit level until the sampled signal returns to normal.

[0071] In the embodiment of the present application, a special compression module is designed in the audio power amplifier controller to process the high-amplitude sinusoidal signal output by the class D power amplifier module. The compression module can be implemented using digital signal processing (DSP) technology.

[0072] In one embodiment, Figure 4 As shown, the steps for signal compression are:

[0073] 1. Signal sampling: First, the signal output by the Class D power amplifier module is continuously sampled to obtain high-frequency signal data.

[0074] 2. Application of compression algorithm: This design continuously samples the maximum output signal of the final stage. Once the maximum output is detected, the counting starts. If the maximum output signal decreases or disappears during this period, the counter is reset. If the maximum output signal is continuously detected within 10 seconds of counting, it is considered an abnormal event. Either the tested sine wave signal or the abnormal low-frequency DC signal can be considered an abnormal signal. At this time, the output power is compressed by half, the output voltage is reduced by 1.414 times, and the sound pressure level SPL is about -3dB, which can be distinguished. After the output signal is compressed by 3dB, the output continues to be at the maximum level of the compressed signal. If this signal also lasts for 15 seconds, the input signal is compressed by 1 / 2, that is, the maximum output power is reduced by another 3dB, that is, 6dB is compressed on the initial maximum output signal. This design continuously samples the maximum output signal of the final stage. If the maximum burst output lasts for about 10 seconds, the compressor starts to compress the output to half the power (the output voltage is reduced to 0.707 times the initial value), and the sound pressure level SPL is about -3dB, which can be discerned. This power lasts for about 10 seconds. If the input decreases at this time, the compressor returns to normal. If the input remains unchanged at this time, the power is compressed by half again, and the output voltage is reduced by 0.707 times, and the sound pressure level SPL is reduced by -3dB. This output power is maintained until the input signal decreases, and the compressor recovers in reverse stages.

[0075] In a preferred embodiment, the first threshold is 10 seconds, and the second threshold is 15 seconds; the first limit level is 1 / 2, and the second limit level is 1 / 4.

[0076] The abnormal signal is one or more of the following signal characteristics: a maximum level output signal, an abnormal direct current signal, and an abnormal extremely low frequency signal.

[0077] In the embodiment of the present application, since the output duration of a normal low-frequency audio signal (such as a percussion instrument, etc.) will not exceed 10 seconds, only the tested sine wave or abnormal input signal will last for more than 10 seconds with the same amplitude. Therefore, the preferred solution is 10 seconds.

[0078] In a preferred embodiment, the signal compression method further comprises:

[0079] If the number of times that the class D audio power amplifier is compressed to the first limit level exceeds the warning number within a preset time period, the class D audio power amplifier is controlled to stop working.

[0080] In one embodiment, the signal compression method further includes:

[0081] When the stop time of the class D audio power amplifier being stopped due to the number of times exceeding the first limit level being higher than the warning number reaches the stop time threshold, the class D audio power amplifier is controlled to restart.

[0082] In the embodiment of the present application, fault protection and automatic restart functions are provided. For example, if protection is triggered 5 times in a row within 1 minute, the current channel is closed and the fault light flashes. After the channel is closed for about 5 minutes, try to open it. If the fault is eliminated, it can work normally. Otherwise, the above state is repeated.

[0083] Those skilled in the art will understand that Figure 1 to Figure 4 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0084] It should be understood that, although each step in the flow chart of each embodiment of the present application is shown in sequence according to the indication of the arrow, these steps are not necessarily performed in sequence according to the order indicated by the arrow. Unless there is clear explanation in this article, the execution of these steps does not have strict order restriction, and these steps can be performed in other orders. Moreover, at least a portion of the steps in each embodiment may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily performed at the same time, but can be performed at different times, and the execution order of these sub-steps or stages is not necessarily performed in sequence, but can be performed in turn or alternately with at least a portion of other steps or sub-steps or stages of other steps.

[0085] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a software program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0086] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A signal compression method, characterized in that: The signal compression method is implemented based on a logic control module in a Class D audio power amplifier and is used to perform signal processing on the filtered signal; The class D audio power amplifier comprises: A controllable limiter, a class D amplifier, a first filter, a second filter and a logic control module; The controllable limiter is provided with an audio signal input terminal for receiving an audio signal input; the signal output terminal of the controllable limiter is connected to the class D amplifier; The output end of the class D amplifier is connected to the first filter, and the class D amplifier is used to amplify the audio signal input from the controllable limiter to generate a PWM pulse signal; The first filter is used to filter the PWM pulse signal output by the class D amplifier, convert it into an analog quantity, obtain a filtered signal, and input the filtered signal to the load end; The input end of the logic control module is used to receive the filter signal. When an abnormal signal appears in the filter signal, the filter signal is compressed to reduce the amplitude of the abnormal signal in the filter signal to generate a control signal. The second filter is connected to the logic control module and the controllable limiter, and is used to convert the control signal into a quantization / error signal input of the controllable limiter to adjust the signal output of the controllable limiter; The method comprises the following steps: S10: continuously sampling the filtered signal output by the first filter to obtain a sampled signal; S20: When an abnormal signal is detected in the sampled signal, timing the duration of the abnormal signal; S30: When the duration of the abnormal signal exceeds the first threshold, or when an abnormal low-frequency DC signal is detected after sampling the signal, the Class D audio power amplifier is controlled to compress its output power to a first limit level; S40: After the output power of the class D audio power amplifier is compressed to the first limit level, the voltage value of the sampled signal is determined: If the sampled signal obtained by sampling returns to normal, the output power compression of the Class D audio power amplifier is stopped; If the sampled signal still has an abnormal signal output, and the output duration of the abnormal signal exceeds the second threshold, the output power of the Class D audio amplifier is compressed to the second limit level and maintained at the second limit level until the sampled signal returns to normal.

2. A signal compression method according to claim 1, characterized in that: The abnormal signal is one or more of the following signal characteristics: Maximum level output signals, abnormal DC signals, and abnormal very low frequency signals.

3. A signal compression method according to claim 1, characterized in that: The first threshold is 10 seconds, and the second threshold is 15 seconds; The first limit level is 1 / 2, and the second limit level is 1 / 4.

4. A signal compression method according to claim 1, characterized in that: The signal compression method further comprises: If the number of times that the class D audio power amplifier is compressed to the first limit level exceeds the warning number within a preset time period, the class D audio power amplifier is controlled to stop working.

5. A signal compression method according to claim 4, characterized in that: The signal compression method further comprises: When the stop time of the class D audio power amplifier being stopped due to the number of times exceeding the first limit level being higher than the warning number reaches the stop time threshold, the class D audio power amplifier is controlled to restart.

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