CN115567007B - Power amplifier direct current operating point tracking circuit - Google Patents
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- H—ELECTRICITY
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- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
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- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/181—Low-frequency amplifiers, e.g. audio preamplifiers
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- H—ELECTRICITY
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- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
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Abstract
The invention discloses a power amplifier direct-current working point tracking circuit, wherein an error amplification module is used for overlapping an audio signal, a power level pulse signal and a first reference voltage signal, performing difference operation with a second reference voltage signal, amplifying the difference signal and inputting the amplified difference signal to a pulse modulation module; the pulse modulation module is used for modulating the amplified difference signal into a power level pulse signal and outputting the power level pulse signal outwards; the feedback module is used for feeding the power level pulse signal back to the error amplification module; the invention has the advantages that the audio power amplifier can still realize maximum range output under the condition of large voltage fluctuation range when the single power supply supplies power, and the power amplifier output direct current working point is ensured to track half of the power amplifier power supply voltage all the time.
Description
Technical Field
The invention relates to the technical field of audio power amplifier electronics, in particular to a power amplifier direct-current working point tracking circuit.
Background
In order to reduce the complexity and cost of a power supply, a digital audio power amplifier often needs to be powered by a single power supply, and particularly in products such as battery powered equipment, active sound boxes and vehicle-mounted high-power amplifiers, a direct-current working point needs to be set for the output of the power amplifier in order to obtain the bidirectional dynamic range of an audio signal. The current common schemes include: if the power supply voltage is 48V, the fixed direct current working point of the digital power amplifier output is 24V, the scheme is characterized by simplicity and convenience, and obvious defects are that: when the power supply voltage of the power amplifier changes in a large range during working, for example, the typical voltage range of a 48V lithium battery is 32v to 55v, a fixed direct current working point of 24V is set, when the power supply voltage is only 32V, only 32-24=8v is maximally output at the positive half cycle of an audio signal under an ideal condition, the maximum peak value of undistorted output is only 2x8=16v, and the power supply voltage utilization rate of 32v is only 50%.
In view of this, the present application is specifically made.
Disclosure of Invention
The invention aims to solve the technical problem that in the prior art, a fixed direct-current working point is set to obtain a bidirectional dynamic range of an audio signal, the audio signal tracking circuit is only suitable for an application scene with stable and unchangeable power supply voltage, when voltage fluctuation is too large, power amplifier output cannot completely utilize the power supply range of the power amplifier, maximum dynamic output is realized, and the utilization rate of the power supply voltage is reduced.
The invention is realized by the following technical scheme:
a power amplifier direct current working point tracking circuit comprises an error amplification module, a feedback module and a pulse modulation module;
the error amplification module is used for superposing the audio signal, the power level pulse signal and the first reference voltage signal, performing difference operation on the superposed audio signal, the power level pulse signal and the first reference voltage signal and a second reference voltage signal, amplifying the difference signal and inputting the amplified difference signal to the pulse modulation module;
the pulse modulation module is used for modulating the amplified difference signal into a power level pulse signal and outputting the power level pulse signal outwards;
the feedback module is used for feeding the power level pulse signal back to the error amplification module.
In a traditional digital audio power amplifier, in order to obtain an audio bidirectional dynamic range, a fixed direct current working point is usually set, and the range change of a power supply voltage of a power amplifier during the working period is realized by setting the fixed direct current working point, but when the audio bidirectional dynamic range is obtained by adopting a traditional method, the audio bidirectional dynamic range is usually only suitable for an application scene with stable and unchangeable power supply voltage, when the voltage fluctuation is overlarge, the power amplifier output cannot completely utilize the power supply range of the power amplifier to realize the maximum dynamic output, so that the utilization rate of the power supply voltage is reduced.
Preferably, the pulse modulation module includes a modulator, a driving module and a power output stage circuit, the positive electrode of the modulator is connected to the output end of the error amplification module, the negative electrode of the modulator is connected to the pulse signal, the output end of the modulator is connected to the input end of the driving module, and the output end of the driving module is connected to the input end of the power output stage circuit.
Preferably, the power output stage circuit includes a MOS transistor Q1 and a MOS transistor Q2, a gate of the MOS transistor Q1 and a gate of the MOS transistor Q2 are both connected to the output terminal of the driving module, a drain of the MOS transistor Q1 is connected to the power supply voltage, a source of the MOS transistor Q1 and a drain of the MOS transistor Q2 are connected and then output to the outside, and a source of the MOS transistor Q2 is connected to the ground.
Preferably, the first reference voltage signal is connected to the input terminal of the error amplification module through a resistor Rdcin and a compensation network, and the audio signal is connected to the input terminal of the error amplification module through a capacitor Cin and a resistor Rin in sequence.
Preferably, the circuit further comprises a second filter circuit, an input end of the second filter circuit is connected with an output end of the pulse modulation module, and an output end of the second filter circuit is connected with the loudspeaker through a coupling capacitor Cout.
Preferably, the first reference voltage signal is obtained through a dc reference voltage circuit, the dc reference voltage circuit includes a voltage dividing module, an RC filter, a dc offset module and an operational amplifier, an input end of the voltage dividing module is connected to a power amplifier supply voltage VP, an output end of the voltage dividing module is connected to an input end of the RC filter, and an output end of the RC filter is connected to an inverting input end of the operational amplifier through a resistor R4; the output end of the direct current bias module is connected with the non-inverting input end of the operational amplifier, and the output end of the operational amplifier outputs a first reference voltage signal.
Preferably, the voltage divider module includes resistance R1, resistance R2 and electric capacity C2, and power amplifier supply voltage VP passes through resistance R1 with the RC filter input is connected, resistance R2 one end and electric capacity C2's one end equally divide respectively with resistance R1 and the RC filter input is connected, the resistance R2 other end and electric capacity C2's the other end is connected to the ground.
Preferably, the dc bias module includes a resistor R6, a resistor R7, a resistor R8, a capacitor C5, and a capacitor C6, the power supply voltage is sequentially connected to the non-inverting input terminal of the operational amplifier through the resistor R6 and the resistor R7, one end of the capacitor C5 is connected to the resistor R6 and the resistor R7, and the other end of the capacitor C5 is connected to ground; one end of the capacitor C6 is connected with the resistor R7 and the inverting input end of the operational amplifier respectively, the other end of the capacitor C6 is connected with the ground, and the inverting input end of the operational amplifier is also connected with the ground through a resistor R8.
Preferably, the inverting input terminal of the operational amplifier is connected in parallel with the output terminal of the operational amplifier through a resistor R5 and a capacitor C4.
Preferably, when the circuit is in operation, the specific expression of the voltage DC _ PA at the DC operating point at the output end of the error amplifying module is:
vref is the second reference voltage signal and the second reference voltage signal,
the reference voltage is a first reference voltage signal, rfb is a feedback resistor in the feedback module, rdcin is a resistance value of a resistor between the first reference voltage signal and the error amplification module, VA is a power supply voltage, VP is a power amplifier power supply voltage, R1, R2, R4, R5, R6, R7 and R8 are specific resistance values of corresponding resistors, and R3 is a resistance value corresponding to a resistor R3 in the RC filter.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the direct-current working point tracking circuit of the power amplifier, provided by the embodiment of the invention, the first reference voltage signal and the audio signal are superposed at the input end of the error amplification module and have errors with the second reference voltage signal, and the error signal processing method is adopted, so that the maximum range output of the audio power amplifier can be still realized under the condition that the voltage fluctuation range is large when the single power supply supplies power, and the power amplifier output direct-current working point is ensured to track half of the power supply voltage of the power amplifier all the time.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic diagram of a circuit module;
FIG. 2 is a detailed schematic diagram of a digital audio power amplifier;
FIG. 3 is a circuit diagram of reference voltage calculation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail so as not to obscure the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrases "one embodiment," "an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "upper", "lower", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be construed as limiting the scope of the present invention.
In a digital audio power amplifier, in order to obtain an audio bidirectional dynamic range, a fixed direct-current operating point is usually set, and the range change of power supply voltage of a power amplifier during the operation is realized by setting the fixed direct-current operating point.
The invention provides a power amplifier direct current working point tracking circuit, which is characterized in that a first reference voltage signal and an audio signal are superposed at the input end of an error amplification module and have errors with a second reference voltage signal, and an error signal processing method is adopted to ensure that the audio power amplifier can still realize maximum range output under the condition of large voltage fluctuation range when a single power supply supplies power, and ensure that a power amplifier output direct current working point always tracks half of the power amplifier power supply voltage VP.
The specific circuit structure of the invention is shown in fig. 1, and comprises an error amplification module, a feedback module and a pulse modulation module; the error amplification module is used for superposing the audio signal, the power level pulse signal and the first reference voltage signal, performing difference operation on the superposed audio signal, the power level pulse signal and the first reference voltage signal and a second reference voltage signal, amplifying the difference signal and inputting the amplified difference signal to the pulse modulation module; in this embodiment, the error amplifying module is an error amplifier, and can perform a difference operation on two signals input by the input terminal.
The first reference voltage signal is connected with the input end of the error amplification module through a resistor Rdcin and a compensation network, and the audio signal is connected with the input end of the error amplification module through a capacitor Cin and a resistor Rin in sequence.
The pulse modulation module is used for modulating the amplified difference signal into a power level pulse signal and outputting the power level pulse signal outwards;
the pulse modulation module comprises a modulator, a driving module and a power output stage circuit, wherein the positive electrode of the modulator is connected with the output end of the error amplification module, the negative electrode of the modulator is connected with a pulse signal, the output end of the modulator is connected with the input end of the driving module, and the output end of the driving module is connected with the input end of the power output stage circuit.
The power output stage circuit comprises an MOS tube Q1 and an MOS tube Q2, the grid electrode of the MOS tube Q1 and the grid electrode of the MOS tube Q2 are connected with the output end of the driving module, the drain electrode of the MOS tube Q1 is connected with a power supply voltage, the source electrode of the MOS tube Q1 is connected with the drain electrode of the MOS tube Q2 and then outputs outwards, and the source electrode of the MOS tube Q2 is connected with the ground.
The feedback module is configured to feed back the power stage pulse signal to the error amplification module, in this embodiment, the feedback module is a resistor Rfb, and the feedback module is specifically configured to feed back a power stage output signal to an error amplifier of the input stage, obtain an error signal by overlapping the error signal with an input signal, and correct an input error and an output error by performing PWM modulation on the error signal, so that the output tracks input changes.
The circuit further comprises a second filter circuit, wherein the input end of the second filter circuit is connected with the output end of the pulse modulation module, and the output end of the second filter circuit is connected with the loudspeaker through a coupling capacitor Cout.
In this embodiment, as shown in fig. 2, the following specific settings are set:
the audio Input signal Input is connected to the inverting Input end of an error amplifier formed by the U1 through a resistor Rin, the non-inverting Input end of the error amplifier is connected with a second reference voltage Vref, and the non-inverting Input end of the error amplifier and the second reference voltage Vref of the integrated digital power amplifier chip are integrated in the chip and cannot be adjusted externally. A first reference voltage DC _ REF output by the direct current reference voltage calculation circuit is connected to the inverting input end of an error amplifier U1 of the digital audio power amplifier through a resistor Rdcin, a PWM signal output by the power output stage is connected to the inverting input end of the error amplifier U1 through a feedback resistor Rfb, the output of the error amplifier is used for obtaining the PWM signal through a modulator, the PWM signal output by the modulator is used for obtaining a finally amplified audio signal through a driving module, a power output stage circuit and a second filter circuit, the audio signal is connected with a loudspeaker through a coupling capacitor Cout, and the second filter circuit is an LC filter.
In this embodiment, the first reference voltage signal may be obtained through computer setting, or obtained through circuit matching, and the obtaining manner is not further limited, and in this embodiment, the obtaining specifically is: the first reference voltage circuit comprises a voltage division module, an RC filter, a direct current bias module and an operational amplifier, wherein the input end of the voltage division module is connected with a power amplifier power supply voltage VP, the output end of the voltage division module is connected with the input end of the RC filter, and the output end of the RC filter is connected with the inverting input end of the operational amplifier through a resistor R4; the output end of the direct current bias module is connected with the non-inverting input end of the operational amplifier, and the output end of the operational amplifier outputs a first reference voltage signal.
The voltage division module includes resistance R1, resistance R2 and electric capacity C2, and power amplifier supply voltage VP passes through resistance R1 with the RC wave filter input is connected, resistance R2 one end and electric capacity C2's one end equally divide do not with resistance R1 with the RC wave filter input is connected, the resistance R2 other end and electric capacity C2's the equal ground connection of the other end.
The direct current bias module comprises a resistor R6, a resistor R7, a resistor R8, a capacitor C5 and a capacitor C6, power supply voltage is connected with the non-inverting input end of the operational amplifier sequentially through the resistor R6 and the resistor R7, one end of the capacitor C5 is connected with the resistor R6 and the resistor R7 respectively, and the other end of the capacitor C5 is connected with the ground; one end of the capacitor C6 is connected with the resistor R7 and the inverting input end of the operational amplifier respectively, the other end of the capacitor C6 is connected with the ground, and the inverting input end of the operational amplifier is also connected with the ground through a resistor R8. And the inverting input end of the operational amplifier and the output end of the operational amplifier are connected with a resistor R5 and a capacitor C4 in parallel.
The direct current reference voltage calculation circuit is used for calculating a direct current reference voltage DC _ REF according to the power amplifier power supply voltage VP, a voltage division module is formed by resistors R1, R2 and C2 and used for filtering high-frequency noise, the input of the voltage division module is connected with the power amplifier power supply VP and used for detecting the power supply voltage and realizing the tracking of the power supply voltage by the power amplifier output direct current voltage, and the output of the voltage division module is connected to the inverting input end of the operational amplifier U3 through a resistor R4 after passing through an RC filter formed by a resistor R3 and a capacitor C3; the resistors R6, R7 and R8 and the capacitors C5 and C6 form a direct current bias module for generating a direct current bias for the direct current reference voltage calculation circuit, the capacitors C5 and C6 are used for filtering high-frequency noise, the resistor R5 and the capacitor C4 are a feedback network of the operational amplifier U3 and used for setting the direct current gain of the operational amplifier and attenuating high-frequency interference, and the detailed circuit is shown in the attached figure 3.
When the circuit operates, a specific expression of the voltage DC _ PA at the DC operating point at the output end of the error amplification module is as follows:
vref is the second reference voltage signal and the second reference voltage signal,
the reference voltage is a first reference voltage signal, rfb is a feedback resistor in the feedback module, rdcin is a resistance value of a resistor between the first reference voltage signal and the error amplification module, VA is a power supply voltage, VP is a power amplifier power supply voltage, and R1, R2, R3, R4, R5, R6, R7 and R8 are specific resistance values of corresponding resistors.
The form can be obtained by combining the above two equations
Where a and b are determined by the respective resistance parameters and VA, vref in the drawing, it is only necessary to select the device parameters such that a = is obtained0,b =0.5, namely, can obtain
Namely, the voltage of the output direct-current working point of the digital audio power amplifier strictly tracks half of the power supply voltage, and the maximum dynamic range of the output of the amplifier is ensured.
If the voltage VA is 12v, vref is 5v, and rfb is 47k Ω, then Rdcin =10k Ω, R1=47k Ω, R2=10k Ω, R3=47 Ω, R4=8.2k Ω, R5=10k Ω, R6=13k Ω, R7=510 Ω, and R8=6.2k Ω may be selected, and the calculation method may be used to obtain the voltage VA, vref, and rfb
That is, the output dc operating point voltage of the digital audio power amplifier can be made to strictly track half of the power supply voltage, and only 1.7mV error is generated, which is negligible for the audio power amplifier.
According to the power amplifier direct-current working point tracking circuit disclosed by the embodiment, the first reference voltage signal and the audio signal are superposed at the input end of the error amplification module and have an error with the second reference voltage signal, and the error signal processing method is used for ensuring that the audio power amplifier can still realize maximum range output under the condition of a large voltage fluctuation range when the single power supply supplies power, and ensuring that the power amplifier output direct-current working point always tracks half of the power amplifier power supply voltage VP.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A power amplifier direct current working point tracking circuit is characterized by comprising an error amplification module, a feedback module and a pulse modulation module;
the error amplification module is used for superposing the audio signal, the power level pulse signal and the first reference voltage signal, performing difference operation on the superposed audio signal, the power level pulse signal and the first reference voltage signal and a second reference voltage signal, amplifying the difference signal and inputting the amplified difference signal to the pulse modulation module;
the pulse modulation module is used for modulating the amplified difference signal into a power level pulse signal and outputting the power level pulse signal outwards;
the feedback module is used for feeding the power level pulse signal back to the error amplification module;
the first reference voltage signal is obtained through a direct current reference voltage circuit, the direct current reference voltage circuit comprises a voltage division module, an RC filter, a direct current bias module and an operational amplifier, the input end of the voltage division module is connected with a power amplifier power supply voltage VP, the output end of the voltage division module is connected with the input end of the RC filter, and the output end of the RC filter is connected with the inverting input end of the operational amplifier through a resistor R4; the output end of the direct current bias module is connected with the non-inverting input end of the operational amplifier, and the output end of the operational amplifier outputs a first reference voltage signal;
the voltage division module comprises a resistor R1, a resistor R2 and a capacitor C2, a power amplifier power supply voltage VP is connected with the input end of the RC filter through the resistor R1, one end of the resistor R2 and one end of the capacitor C2 are respectively connected with the resistor R1 and the input end of the RC filter, and the other end of the resistor R2 and the other end of the capacitor C2 are respectively connected with the ground;
the direct current bias module comprises a resistor R6, a resistor R7, a resistor R8, a capacitor C5 and a capacitor C6, a power supply voltage VA is connected with the non-inverting input end of the operational amplifier sequentially through the resistor R6 and the resistor R7, one end of the capacitor C5 is connected with the resistor R6 and the resistor R7 respectively, and the other end of the capacitor C5 is connected with the ground; one end of the capacitor C6 is connected with the resistor R7 and the inverting input end of the operational amplifier respectively, the other end of the capacitor C6 is connected with the ground, and the inverting input end of the operational amplifier is also connected with the ground through a resistor R8.
2. The power amplifier dc operating point tracking circuit according to claim 1, wherein the pulse modulation module comprises a modulator, a driving module, and a power output stage circuit, a positive pole of the modulator is connected to the output terminal of the error amplification module, a negative pole of the modulator is connected to a pulse signal, an output terminal of the modulator is connected to the input terminal of the driving module, and an output terminal of the driving module is connected to the input terminal of the power output stage circuit.
3. The power amplifier dc operating point tracking circuit according to claim 2, wherein the power output stage circuit includes a MOS transistor Q1 and a MOS transistor Q2, a gate of the MOS transistor Q1 and a gate of the MOS transistor Q2 are both connected to the output terminal of the driving module, a drain of the MOS transistor Q1 is connected to a power supply voltage, a source of the MOS transistor Q1 is connected to a drain of the MOS transistor Q2 and then outputs the output voltage, and a source of the MOS transistor Q2 is connected to ground.
4. The power amplifier dc operating point tracking circuit according to claim 1, wherein the first reference voltage signal is connected to the input terminal of the error amplifying module through a resistor Rdcin, and the audio signal is connected to the input terminal of the error amplifying module through a capacitor Cin and a resistor Rin in sequence.
5. The power amplifier dc operating point tracking circuit according to claim 1, further comprising a second filter circuit, wherein an input terminal of the second filter circuit is connected to the output terminal of the pulse modulation module, and an output terminal of the second filter circuit is connected to the speaker through a coupling capacitor Cout.
6. The power amplifier dc operating point tracking circuit of claim 1, wherein the inverting input of the operational amplifier is connected in parallel with the output of the operational amplifier via a resistor R5 and a capacitor C4.
7. The power amplifier DC operating point tracking circuit of claim 6, wherein when the circuit is operating, the DC operating point voltage DC _ PA at the output of the error amplifying module is expressed by the following specific expression:
vref is a second reference voltage signal, DC _ REF is a first reference voltage signal, rfb is a feedback resistor in the feedback module, rdcin is a resistance value of the resistor between the first reference voltage signal and the error amplification module, VA is a power supply voltage, VP is a power amplifier power supply voltage, R1, R2, R4, R5, R6, R7 and R8 are specific resistance values of corresponding resistors, and R3 is a resistance value corresponding to a resistor R3 in the RC filter.
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| CN112671226B (en) * | 2021-03-22 | 2021-06-29 | 宜宾听点科技有限公司 | Power amplifier power supply voltage control method and system |
| CN216794946U (en) * | 2021-12-20 | 2022-06-21 | 惠州市雅迪威电子有限公司 | Power amplifier circuit, playing device and audio system |
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| WO2007029737A1 (en) * | 2005-09-09 | 2007-03-15 | Pioneer Corporation | Balanced amplifier, and electronic circuit |
| JP2016039451A (en) * | 2014-08-06 | 2016-03-22 | ローム株式会社 | Power supply circuit for audio amplifier, electronic apparatus, supply method of power supply voltage to audio amplifier |
| CN113890492A (en) * | 2021-10-09 | 2022-01-04 | 深圳市创成微电子有限公司 | Power supply voltage control method and controller of audio power amplifier and audio equipment |
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