CN106992756A - Class D Power Amplifiers and Audio Equipment - Google Patents

Abstract

The present invention discloses a class D power amplifier. The class D power amplifier includes a waveform generator, a comparator, a power amplifier circuit and a low-pass filter. The in-phase input end of the comparator is connected to the output end of the waveform generator. The inverting input end of the comparator is connected to the input signal. The output end of the comparator is connected to the input end of the power amplifier circuit. The output end of the power amplifier circuit is connected to the input end of the low-pass filter. The low-pass filter is a low-pass filter with an adjustable cut-off frequency. The class D power amplifier of the embodiment of the present invention adopts a low-pass filter with an adjustable cut-off frequency to demodulate the modulated signal, and the cut-off frequency of the low-pass filter can be adjusted according to the demand for mid-high frequencies to change the amplitude-frequency characteristics, thereby changing the sound effect. In addition, the present invention also discloses an audio device.

Description

Class D Power Amplifiers and Audio Equipment

technical field

The invention relates to the field of audio technology, in particular to a class D power amplifier and audio equipment.

Background technique

In related technologies, class D power amplifiers are widely used in communication, audio and other fields due to their advantages of simple structure and high efficiency. In terms of audio, many people have different pursuits for the ratio of mid-to-treble, that is, different pursuits for sound effects. For example, some people want more treble, while others have less. In order to meet this demand, the common method is to adjust the frequency response by adding DSP and software. However, the disadvantage of this method is that it increases the cost and also reduces the audio performance.

Contents of the invention

Embodiments of the present invention provide a class D power amplifier and audio equipment.

The class D power amplifier of the embodiment of the present invention comprises a waveform generator, a comparator, a power amplifier circuit and a low-pass filter; the non-inverting input terminal of the comparator is connected to the output terminal of the waveform generator, and the inverting The phase input terminal is connected to the input signal, and the output terminal of the comparator is connected to the input terminal of the power amplifier circuit; the output terminal of the power amplifier circuit is connected to the input terminal of the low-pass filter, and the low-pass filter is a cut-off frequency Adjustable low pass filter.

An audio device according to an embodiment of the present invention includes a class D power amplifier according to an embodiment of the present invention.

The class D power amplifier and audio equipment in the embodiment of the present invention use a low-pass filter with an adjustable cut-off frequency to demodulate the modulated signal, and the cut-off frequency of the low-pass filter can be adjusted according to the demand for mid-high tones to change the amplitude-frequency characteristics, thereby changing the sound effect.

Additional aspects and advantages of embodiments of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and understandable from the description of the embodiments in conjunction with the following drawings, wherein:

FIG. 1 is a schematic diagram of functional modules of a class D power amplifier according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a first-order low-pass filter according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a second-order low-pass filter according to an embodiment of the present invention.

FIG. 4 is a circuit diagram of a third-order low-pass filter according to an embodiment of the present invention.

Description of main components and symbols:

Class D power amplifier 10, waveform generator 11, comparator 12, power amplifier circuit 13, low-pass filter 14, first-order low-pass filter 142, second-order low-pass filter 144, third-order low-pass filter 146;

The first resistor R1, the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the first inductor L1, the second inductor L2, the first switch SW1, The second switch SW2 and the third switch SW3.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, are only for explaining the embodiments of the present invention, and should not be construed as limiting the embodiments of the present invention.

Referring to FIG. 1 , a class D power amplifier 10 according to an embodiment of the present invention includes a waveform generator 11 , a comparator 12 , a power amplifier circuit 13 and a low-pass filter 14 . The non-inverting input terminal of the comparator 12 is connected to the output terminal of the waveform generator 11 . The inverting input terminal of the comparator 12 is connected to the input signal. The output terminal of the comparator 12 is connected to the input terminal of the power amplifier circuit 13 . The output terminal of the power amplifier circuit 13 is connected to the input terminal of the low-pass filter 14 . The low-pass filter 14 is a low-pass filter 14 with an adjustable cut-off frequency.

The class D power amplifier 10 of the embodiment of the present invention adopts the low-pass filter 14 with adjustable cut-off frequency to demodulate the modulated signal, and the cut-off frequency of the low-pass filter 14 can be adjusted to change the amplitude-frequency characteristics, thereby changing the sound effect.

In some embodiments, the waveform generator 11 is a sawtooth generator.

Specifically, the sawtooth generator can periodically generate a sawtooth signal. The input signal is compared with the sawtooth signal generated by the sawtooth wave generator through the comparator 12, and then PWM modulated to output a pulse width modulated signal. The power amplifier circuit 13 amplifies the modulated signal, and the low pass filter 14 will be modulated. The signal is demodulated. Therefore, the amplitude-frequency characteristic of the low-pass filter 14 affects the sound effect of the class-D power amplifier 10 . In some embodiments, the low-pass filter 14 includes a switch that can be turned on and off to adjust the cutoff frequency.

In some embodiments, the low pass filter 14 includes an LC filter circuit and a switch. The switch is connected to the LC filter circuit. The closing and opening of the switch is used to change the capacitance value of the LC filter circuit to adjust the cut-off frequency.

For example, the closing of the switch can increase the capacitance value in the LC filter circuit, so that the cut-off frequency of the low-pass filter 14 decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa.

In some embodiments, the low pass filter 14 includes an LC filter circuit and a switch. The switch is connected to the LC filter circuit. The closing and opening of the switch is used to change the inductance value of the LC filter circuit to adjust the cut-off frequency.

For example, the closing of the switch can increase the inductance value in the LC filter circuit, so that the cut-off frequency of the low-pass filter 14 decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa.

In some embodiments, the low pass filter 14 includes an RC filter circuit and a switch. The switch is connected to the RC filter circuit. The closing and opening of the switch is used to change the capacitance value of the RC filter circuit to adjust the cut-off frequency.

For example, closing the switch can increase the capacitor value in the RC filter circuit, so that the cutoff frequency of the low-pass filter 14 decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa.

Referring to FIG. 2 , in some embodiments, the low-pass filter 14 includes a first-order low-pass filter 142 .

Specifically, the first-order low-pass filter 142 may be a circuit composed of RC elements and switches. In this way, the circuit structure is simple.

In some implementations, the first-order low-pass filter 142 includes a first resistor R1 , a first capacitor C1 , a second capacitor C2 and a first switch SW1 . One end of the first resistor R1 is connected to the output end of the power amplifier circuit 13 . The other end of the first resistor R1 is connected to one end of the first capacitor C1 and one end of the first switch SW1. The other end of the first capacitor C1 is grounded. One end of the second capacitor C2 is connected to the other end of the first switch SW1. The other end of the second capacitor C2 is grounded. The closing and opening of the first switch SW1 is used to adjust the cut-off frequency.

Specifically, in the embodiment of the present invention, one end of the first resistor R1 is used as the input end of the first-order low-pass filter 142 , and the other end of the first resistor R1 is used as the output end of the first-order low-pass filter 142 .

The formula for calculating the cutoff frequency is It can be seen that when the resistance R=1Ω and the capacitance C=159μH, the cutoff frequency f=1KHZ; when the resistance R=0.1Ω and the capacitance C=1590μH, the cutoff frequency f=1KHZ.

Therefore, the values of the first resistor R1 and the first capacitor should be determined according to the cutoff frequency. It can be understood that the first resistor R1 should have a smaller resistance value, and the first capacitor C1 or the second capacitor C2 should have a larger capacitance value, so as to avoid voltage loss on the first resistor R1.

When the first switch SW1 is closed, the first capacitor C1 and the second capacitor C2 are connected in parallel, the capacitance value of the first-order low-pass filter 142 becomes larger, the cut-off frequency decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa Of course.

In this way, the cut-off frequency of the low-pass filter 14 can be adjusted to change the amplitude-frequency characteristics according to the demand for middle and high tones, thereby changing the sound effect.

Certainly, in other implementation manners, the first-order low-pass filter 142 may also be composed of other elements or circuits.

Referring to FIG. 3 , in some embodiments, the low-pass filter 14 includes a second-order low-pass filter 144 .

Specifically, the second-order low-pass filter 144 may be a circuit composed of LC elements and switches. In this way, the filtering effect is better and the cost is lower.

In some implementations, the second-order low-pass filter 144 includes a first inductor L1, a third capacitor C3, a fourth capacitor C4, and a second switch SW2. One end of the first inductor L1 is connected to the output end of the power amplifier circuit 13 . The other end of the first inductor L1 is connected to one end of the third capacitor C3 and one end of the second switch SW2. The other end of the third capacitor C3 is grounded. One end of the fourth capacitor C4 is connected to the other end of the second switch SW2. The other end of the fourth capacitor C4 is grounded. The closing and opening of the second switch SW2 is used to adjust the cut-off frequency.

Specifically, in the embodiment of the present invention, one end of the first inductor L1 is used as the input end of the second-order low-pass filter 144 , and the other end of the first inductor L1 is used as the output end of the second-order low-pass filter 144 .

When the second switch SW2 is closed, the third capacitor C3 and the fourth capacitor C4 are connected in parallel, the capacitance value of the second-order low-pass filter 144 becomes larger, the cut-off frequency decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa Of course.

In this way, the cut-off frequency of the low-pass filter 14 can be adjusted to change the amplitude-frequency characteristics according to the demand for middle and high tones, thereby changing the sound effect.

Certainly, in other implementation manners, the second-order low-pass filter 144 may also be composed of other elements or circuits.

Referring to FIG. 4 , in some embodiments, the low-pass filter 14 includes a third-order low-pass filter 146 .

Specifically, the third-order low-pass filter 146 may be a circuit composed of LC elements and switches. In this way, the filtering effect is better, and the part of the signal higher than the cutoff frequency attenuates rapidly.

In some implementations, the third-order low-pass filter 146 includes a second inductor L2, a fifth capacitor C5, a sixth capacitor C6, and a third switch SW3. One end of the second inductor L2 is connected to the output end of the power amplifier circuit 13 and one end of the third switch SW3. The other end of the second inductor L2 is connected to one end of the sixth capacitor C6. One end of the fifth capacitor C5 is connected to the other end of the third switch SW3. The other end of the fifth capacitor C5 is grounded. The other end of the sixth capacitor C6 is grounded. The closing and opening of the third switch SW3 is used to adjust the cut-off frequency.

Specifically, in the embodiment of the present invention, one end of the second inductor L2 is used as the input end of the third-order low-pass filter 146 , and the other end of the second inductor L2 is used as the output end of the third-order low-pass filter 146 .

When the third switch SW3 is closed, the capacitance value of the third-order low-pass filter 146 increases, the cut-off frequency decreases, and the high-frequency part that can pass through the circuit decreases, and vice versa.

In this way, the cut-off frequency of the low-pass filter 14 can be adjusted to change the amplitude-frequency characteristics according to the demand for middle and high tones, thereby changing the sound effect.

Certainly, in other implementation manners, the third-order low-pass filter 146 may also be composed of other elements or circuits.

The audio equipment in the embodiment of the present invention includes the class D power amplifier 10 in any of the above embodiments.

The audio equipment of the embodiment of the present invention adopts the low-pass filter 14 with adjustable cut-off frequency to demodulate the modulated signal, and can adjust the cut-off frequency of the low-pass filter 14 to change the amplitude-frequency characteristic according to the demand for middle and high tones, thereby Change sound effects.

Specifically, audio equipment can be, but not limited to, audio equipment such as power amplifiers, speakers, multimedia consoles, digital mixers, audio sampling cards, synthesizers, mid-high frequency speakers, microphones, sound cards in PCs, earphones, and DVD playback equipment. .

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the description of the embodiments of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a It is a detachable connection, or an integral connection; it can be mechanically connected, it can be electrically connected, or it can communicate with each other; it can be directly connected or indirectly connected through an intermediary, and it can be internal communication between two components or two components interaction relationship. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present invention according to specific situations.

The above disclosure provides many different embodiments or examples for implementing different structures of embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, the components and arrangements of specific examples are described above. Of course, they are only examples and are not intended to limit the invention. Furthermore, embodiments of the present invention may repeat reference numerals and/or reference letters in different instances, such repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. . In addition, embodiments of the present invention provide examples of various specific processes and materials, but one of ordinary skill in the art may recognize the use of other processes and/or the use of other materials.

In the description of this specification, reference to the terms "one embodiment", "certain embodiments", "exemplary embodiments", "examples", "specific examples" or "some examples" etc. A specific feature, structure, material, or characteristic described in an embodiment or an example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

Any process or method descriptions in flowcharts or otherwise described herein may be understood to represent modules, segments or portions of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and the scope of preferred embodiments of the invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including substantially concurrently or in reverse order depending on the functions involved, which shall It is understood by those skilled in the art to which the embodiments of the present invention pertain.

The logic and/or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium, For use with instruction execution systems, devices, or devices (such as computer-based systems, systems including processing modules, or other systems that can fetch instructions from instruction execution systems, devices, or devices and execute instructions), or in conjunction with these instruction execution systems, devices or equipment used. For the purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use in or in conjunction with an instruction execution system, device or device. More specific examples (non-exhaustive list) of computer-readable media include the following: electrical connection with one or more wires (electronic device), portable computer disk case (magnetic device), random access memory (RAM), Read Only Memory (ROM), Erasable and Editable Read Only Memory (EPROM or Flash Memory), Fiber Optic Devices, and Portable Compact Disc Read Only Memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program can be printed, since the program can be read, for example, by optically scanning the paper or other medium, followed by editing, interpretation or other suitable processing if necessary. The program is processed electronically and stored in computer memory.

It should be understood that each part of the embodiments of the present invention may be implemented by hardware, software, firmware or a combination thereof. In the embodiments described above, various steps or methods may be implemented by software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques known in the art: Discrete logic circuits, ASICs with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

Those of ordinary skill in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. During execution, one or a combination of the steps of the method embodiments is included.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing module, each unit may exist separately physically, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software function modules. If the integrated modules are realized in the form of software function modules and sold or used as independent products, they can also be stored in a computer-readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, and the like.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (12)

1. a kind of D-type power amplifier, it is characterised in that including waveform generator, comparator, power amplifier and LPF Device；The in-phase input end of the comparator connects the output end of the waveform generator, and the inverting input of the comparator connects Input signal is connect, the output end of the comparator connects the input of the power amplifier；The output end of the power amplifier connects The input of the low pass filter is connect, the low pass filter is the adjustable low pass filter of cut-off frequency.

2. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter includes LC filter circuits And switch, the switch connection LC filter circuits, the closure of the switch is with disconnecting for changing the LC filter circuits Capacitance to adjust the cut-off frequency.

3. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter includes LC filter circuits And switch, the switch connection LC filter circuits, the closure of the switch is with disconnecting for changing the LC filter circuits Inductance value to adjust the cut-off frequency.

4. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter includes RC filter circuits And switch, the switch connection RC filter circuits, the closure of the switch is with disconnecting for changing the RC filter circuits Capacitance to adjust the cut-off frequency.

5. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter includes first-order low-pass Ripple device.

6. D-type power amplifier as claimed in claim 5, it is characterised in that the low-pass first order filter includes the first electricity Resistance, the first electric capacity, the second electric capacity and first switch；One end of the first resistor connects the output end of the power amplifier, institute The other end for stating first resistor connects one end of first electric capacity and one end of the first switch；First electric capacity it is another One end is grounded；One end of second electric capacity connects the other end of the first switch, and the other end of second electric capacity is grounded, The closure of the first switch is with disconnecting for adjusting the cut-off frequency.

7. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter is filtered including step low-pass Ripple device.

8. D-type power amplifier as claimed in claim 7, it is characterised in that the second-order low-pass filter includes the first electricity Sense, the 3rd electric capacity, the 4th electric capacity and second switch；One end of first inductance connects the output end of the power amplifier, institute The other end for stating the first inductance connects one end of the 3rd electric capacity and one end of the second switch；3rd electric capacity it is another One end is grounded；One end of 4th electric capacity connects the other end of the second switch, and the other end of the 4th electric capacity is grounded, The closure of the second switch is with disconnecting for adjusting the cut-off frequency.

9. D-type power amplifier as claimed in claim 1, it is characterised in that the low pass filter is filtered including third-order low-pass Ripple device.

10. D-type power amplifier as claimed in claim 9, it is characterised in that the third-order low-pass filter includes the second electricity Sense, the 5th electric capacity, the 6th electric capacity and the 3rd switch；One end of second inductance connects output end and the institute of the power amplifier One end of the 3rd switch is stated, the other end of second inductance connects one end of the 6th electric capacity；The one of 5th electric capacity The other end of end connection the 3rd switch, the other end ground connection of the 5th electric capacity；The other end ground connection of 6th electric capacity, The closure of 3rd switch is with disconnecting for adjusting the cut-off frequency.

11. D-type power amplifier as claimed in claim 1, it is characterised in that the waveform generator is sawtooth waveforms Device.

12. a kind of audio frequency apparatus, it is characterised in that including the D-type power amplifier as described in claim 1-11 any one.