CN109068241B - Digital audio power amplifier system - Google Patents
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- CN109068241B CN109068241B CN201810979080.8A CN201810979080A CN109068241B CN 109068241 B CN109068241 B CN 109068241B CN 201810979080 A CN201810979080 A CN 201810979080A CN 109068241 B CN109068241 B CN 109068241B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2430/00—Signal processing covered by H04R, not provided for in its groups
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Abstract
The invention discloses a digital audio power amplifier system, which reduces the influence of a first current source module on a power supply rejection ratio by improving the equivalent output impedance of the first current source module and a second current source module, improves the matching degree between divider resistors, further improves the power supply rejection ratio of the digital audio power amplifier system and eliminates noise on a loudspeaker.
Description
Technical Field
The invention relates to the technical field of semiconductor integrated circuits, in particular to a digital audio power amplifier system.
Background
The current class D audio power amplifier has wide application due to the efficiency exceeding 80%, and particularly, the high efficiency is important for mobile equipment, so that the working time can be prolonged, and the heating value of handheld equipment such as mobile phones can be reduced.
In application fields such as mobile phones, volume and tone quality can have important influence on user experience, and the current trend is that an audio power amplifier outputs higher power to obtain larger volume and better tone quality.
However, in order to output higher emission power, the current digital audio power amplifier system needs to draw a large amount of current from the power supply, and because the power supply has a certain internal resistance, a large range of fluctuation can continuously appear on the power supply, namely the power supply rejection ratio cannot be controlled, and larger noise can be heard on the loudspeaker.
Disclosure of Invention
In view of the above, the present invention provides a digital audio power amplifier system, which has the following technical scheme:
A digital audio power amplifier system comprising: a first current source module and a first power amplifier loop; the first current source module includes: the first field effect transistor, the second field effect transistor, the third field effect transistor, the fourth field effect transistor, the first switch, the second switch, the first operational amplifier and the second operational amplifier;
the source electrode of the first field effect tube is connected with a power supply voltage end, the drain electrode of the first field effect tube is respectively connected with the source electrode of the second field effect tube and the inverting input end of the first operational amplifier, and the grid electrode of the first field effect tube is connected with a first voltage signal input end;
The drain electrode of the second field effect transistor is connected with the input end of the first switch, and the grid electrode of the second field effect transistor is connected with the output end of the first operational amplifier;
the non-inverting input end of the first operational amplifier is connected with the second voltage signal input end;
the output end of the first switch is connected with the input end of the second switch, and the output end of the second switch is connected with the drain electrode of the third field effect transistor;
The source electrode of the third field effect transistor is respectively connected with the inverting input end of the second operational amplifier and the drain electrode of the fourth field effect transistor, and the grid electrode of the third field effect transistor is connected with the output end of the second operational amplifier;
the non-inverting input end of the second operational amplifier is connected with the third voltage signal input end;
The grid electrode of the fourth field effect transistor is connected with the fourth voltage signal input end, and the source electrode of the fourth field effect transistor is grounded;
the first current source module and the first power amplifier loop form a first subsystem, a control end of the first switch and a control end of the second switch are used as signal input ends of the first subsystem and used for receiving PWMP signals, connection nodes of the first switch and the second switch are connected with the first input end of the first power amplifier loop, and an output end of the first power amplifier loop is used as a signal output end of the first subsystem.
Preferably, the first field effect transistor and the second field effect transistor are P-type field effect transistors;
the third field effect transistor and the fourth field effect transistor are N-type field effect transistors.
Preferably, the digital audio power amplifier system further comprises: the second current source module and the second power amplifier loop;
The circuit structure of the second current source module is the same as that of the first current source module, and the circuit structure of the second power amplifier loop is the same as that of the first power amplifier loop;
The second current source module and the second power amplifier loop form a second subsystem, a signal input end of the second subsystem is used for receiving PWMN signals, and an output end of the second power amplifier loop is used as a signal output end of the second subsystem.
Preferably, the digital audio power amplifier system further comprises: a feedback module;
The first input end of the feedback module is connected with the first input end of the first power amplifier loop, and the first output end of the feedback module is connected with the output end of the first power amplifier loop;
the second input end of the feedback module is connected with the first input end of the second power amplifier loop, and the second output end of the feedback module is connected with the output end of the second power amplifier loop;
The control end of the feedback module is used for receiving a control signal, and the control signal is used for controlling the feedback module to be in different working states so as to adjust the resistance matching degree of the first subsystem and the second subsystem and further adjust the power supply rejection ratio of the digital audio power amplifier system;
The periods of the control signal, the PWMP signal, and the PWMN signal are the same.
Preferably, the feedback module includes: a first feedback resistor, a second feedback resistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch, and a tenth switch;
The input end of the third switch and the input end of the fourth switch are connected with the first input end of the first power amplifier loop;
the output end of the fifth switch and the output end of the sixth switch are connected with the output end of the first power amplifier loop;
the input end of the seventh switch and the input end of the eighth switch are connected with the first input end of the second power amplifier loop;
The output end of the ninth switch and the output end of the tenth switch are connected with the output end of the second power amplifier loop;
the output end of the third switch and the output end of the seventh switch are connected with the first end of the first feedback resistor, the second end of the first feedback resistor is connected with the first end of the first resistor, and the second end of the first resistor is respectively connected with the input end of the fifth switch and the input end of the ninth switch;
the first end of the second resistor is connected with the first end of the first resistor, and the second end of the second resistor is grounded;
the output end of the fourth switch and the output end of the eighth switch are connected with the first end of the second feedback resistor, the second end of the second feedback resistor is connected with the first end of the third resistor, and the second end of the third resistor is respectively connected with the input end of the sixth switch and the input end of the tenth switch;
the first end of the fourth resistor is connected with the first end of the third resistor, and the second end of the fourth resistor is grounded;
The control ends of the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are used for receiving the control signals, and the control signals are used for controlling the working states of the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch;
When the third switch, the fifth switch, the eighth switch and the tenth switch are in a conducting state, the other switches are in a closing state;
When the fourth switch, the sixth switch, the seventh switch and the ninth switch are in an on state, the rest switches are in an off state.
Preferably, the third switch, the fifth switch, the eighth switch and the tenth switch are P-type field effect transistors;
the fourth switch, the sixth switch, the seventh switch and the ninth switch are N-type field effect transistors.
Preferably, the third switch, the fifth switch, the eighth switch and the tenth switch are all N-type field effect transistors;
The fourth switch, the sixth switch, the seventh switch and the ninth switch are P-type field effect transistors.
Preferably, the digital audio power amplifier system further comprises: a common mode voltage generating module;
And the second input end of the first power amplifier loop and the second input end of the second power amplifier loop are connected with the output end of the common-mode voltage generating module.
Preferably, the common mode voltage generating module includes: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor and a capacitor;
the first end of the fifth resistor is connected with the voltage input end, the second end of the fifth resistor is connected with the first end of the sixth resistor, the second end of the sixth resistor is connected with the first end of the seventh resistor, and the second end of the seventh resistor is grounded;
The first end of the eighth resistor is connected with the first end of the seventh resistor, the second end of the eighth resistor is connected with the first end of the capacitor, and the second end of the capacitor is connected with the second end of the seventh resistor;
And a connecting node of the eighth resistor and the capacitor is used as an output end of the common-mode voltage generating module.
Preferably, the fifth resistor, the sixth resistor and the seventh resistor have the same resistance value.
Compared with the prior art, the invention has the following beneficial effects:
According to the digital audio power amplification system, the first current source module is arranged to comprise the first field effect transistor, the second field effect transistor, the third field effect transistor, the fourth field effect transistor, the first switch, the second switch, the first operational amplifier and the second operational amplifier and is connected according to a circuit structure, so that the equivalent output impedance of the first current source module is improved, and the influence of the first current source module on the power supply rejection ratio is reduced, so that noise on a loudspeaker is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a digital power amplifier system according to an embodiment of the present invention;
Fig. 2 is another schematic structural diagram of the digital power amplifier system according to the embodiment of the present invention;
Fig. 3 is a schematic diagram of a common-mode voltage generating module according to an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a digital power amplifier system according to an embodiment of the present invention, which is used for converting a PWM signal processed by a digital module into an analog signal, and includes a first subsystem;
as shown in fig. 1, the first subsystem includes: a first current source module 11 and a first power amplifier loop 12; the output end of the first current source module 11 is connected with the first input end of the first power amplifier loop 12, the input end of the first current source module 11 is used as the signal input end of the first subsystem and is used for receiving a PWMP signal, and the output end of the first power amplifier loop 12 is used as the output end VOUTP of the first subsystem;
as shown in fig. 1, the first current source module 11 includes: a first fet M1, a second fet M2, a third fet M3, a fourth fet M4, a first switch S1, a second switch S2, a first operational amplifier 111, and a second operational amplifier 112;
The source electrode of the first field effect transistor M1 is connected with the power supply voltage end VDD, the drain electrode is respectively connected with the source electrode of the second field effect transistor M2 and the inverting input end of the first operational amplifier 111, and the grid electrode is connected with the first voltage signal input end V BP;
The drain electrode of the second field effect transistor M2 is connected to the input end of the first switch S1, and the gate electrode is connected to the output end of the first operational amplifier 111;
the non-inverting input end of the first operational amplifier 111 is connected with the second voltage signal input end V BP1;
the output end of the first switch S1 is connected with the input end of the second switch S2, and the output end of the second switch S2 is connected with the drain electrode of the third field effect transistor M3;
The source electrode of the third field effect transistor M3 is respectively connected with the inverting input end of the second operational amplifier 112 and the drain electrode of the fourth field effect transistor M4, and the grid electrode is connected with the output end of the second operational amplifier 112;
The non-inverting input end of the second operational amplifier 112 is connected with the third voltage signal input end V BN1;
The grid electrode of the fourth field effect transistor M4 is connected with the fourth voltage signal input end V BN, and the source electrode is grounded;
That is, the first current source module 11 and the first power amplifier loop 12 form a first subsystem, the control end of the first switch S1 and the control end of the second switch S2 are used as the input end of the first current source module 11 and are also signal input ends of the first subsystem, and are used for receiving PWMP signals, the connection node of the first switch S1 and the second switch S2 is used as the output end of the first current source module 11, and is connected with the first input end of the first power amplifier loop 12, and the output end of the first power amplifier loop 12 is used as the signal output end VOUTP of the first subsystem.
According to the digital audio power amplification system, the first current source module 11 is arranged to comprise the first field effect transistor M1, the second field effect transistor M2, the third field effect transistor M3, the fourth field effect transistor M4, the first switch S1, the second switch S2, the first operational amplifier 111 and the second operational amplifier 112, and the first current source module 11 is connected according to a circuit structure, so that the equivalent output impedance of the first current source module 11 is improved, and the influence of the first current source module 11 on the power supply rejection ratio is reduced, so that noise on a loudspeaker is reduced.
Further, the first field effect transistor M1 and the second field effect transistor M2 are P-type field effect transistors, and the third field effect transistor M3 and the fourth field effect transistor M4 are N-type field effect transistors;
or, the first field effect transistor M1 and the second field effect transistor M2 are N-type field effect transistors, and the third field effect transistor M3 and the fourth field effect transistor M4 are P-type field effect transistors.
Further, the digital audio power amplifier system further includes: a second subsystem;
As shown in fig. 1, the second subsystem includes: a second current source module 13 and a second power amplifier loop 14; the circuit structure of the second current source module 13 is the same as that of the first current source module 11, and the circuit structure of the second power amplifier loop 14 is the same as that of the first power amplifier loop 12;
The output end of the second current source module 13 is connected with the first input end of the second power amplifier loop 14, the input end of the second current source module 13 is used as the signal input end of the second subsystem and is used for receiving the PWMN signal, and the output end of the second power amplifier loop 14 is used as the output end VOUTN of the second subsystem;
As shown in fig. 1, the second current source module 13 includes: a fifth field effect transistor M5, a sixth field effect transistor M6, a seventh field effect transistor M7, an eighth field effect transistor M8, a switch a, a switch B, a third operational amplifier 131, and a fourth operational amplifier 132;
The source electrode of the fifth field effect transistor M5 is connected to the power voltage terminal VDD, the drain electrode is connected to the source electrode of the sixth field effect transistor M6 and the inverting input terminal of the third operational amplifier 131, and the gate electrode is connected to the first voltage signal input terminal V BP;
The drain electrode of the sixth field effect transistor M6 is connected with the input end of the switch A, and the grid electrode is connected with the output end of the third operational amplifier 131;
The non-inverting input end of the third operational amplifier 131 is connected with the second voltage signal input end V BP1;
the output end of the switch A is connected with the input end of the switch B, and the output end of the switch B is connected with the drain electrode of the seventh field effect transistor M7;
The source electrode of the seventh field effect transistor M7 is connected to the inverting input end of the fourth operational amplifier 132 and the drain electrode of the eighth field effect transistor M8, and the gate electrode is connected to the output end of the fourth operational amplifier 132;
The non-inverting input end of the fourth operational amplifier 132 is connected with the third voltage signal input end V BN1;
The grid electrode of the eighth field effect transistor M8 is connected with the fourth voltage signal input end V BN, and the source electrode is grounded;
That is, the second current source module 13 and the second power amplifier loop 14 form a second subsystem, the control end of the switch a and the control end of the switch B are used as the input end of the second current source module 13 and are also signal input ends of the second subsystem, and are used for receiving PWMN signals, the connection node of the switch a and the switch B is used as the output end of the second current source module 13, and is connected with the first input end of the second power amplifier loop 14, and the output end of the second power amplifier loop 14 is used as the signal output end VOUTN of the second subsystem.
According to the digital audio power amplification system, the second current source module 13 is arranged to comprise the fifth field effect transistor M5, the sixth field effect transistor M6, the seventh field effect transistor M7, the eighth field effect transistor M8, the switch A, the switch B, the third operational amplifier 131 and the fourth operational amplifier 132, and is connected according to a circuit structure, so that the equivalent output impedance of the second current source module 13 is improved, and the influence of the second current source module 13 on the power supply rejection ratio is reduced, so that noise on a loudspeaker is reduced.
Further, the fifth field effect transistor M5 and the sixth field effect transistor M6 are P-type field effect transistors, and the seventh field effect transistor M7 and the eighth field effect transistor M8 are N-type field effect transistors;
Or, the fifth field effect transistor M5 and the sixth field effect transistor M6 are N-type field effect transistors, and the seventh field effect transistor M7 and the eighth field effect transistor M8 are P-type field effect transistors.
Further, as shown in fig. 1, the digital audio power amplifier system further includes: a feedback module 15;
a first input end of the feedback module 15 is connected with a first input end of the first power amplifier loop 12, and a first output end of the feedback module is connected with an output end of the first power amplifier loop 12;
a second input end of the feedback module 15 is connected with a first input end of the second power amplification loop 14, and a second output end of the feedback module is connected with an output end of the second power amplification loop 14;
the control end of the feedback module 15 is configured to receive a control signal, where the control signal is configured to control the feedback module 15 to be in different working states, so as to adjust a resistance matching degree of the first subsystem and the second subsystem, and further adjust a power supply rejection ratio of the digital audio power amplifier system;
The periods of the control signal, the PWMP signal, and the PWMN signal are the same.
Further, as shown in fig. 1, the digital audio power amplifier system further includes: a common mode voltage generation module 16;
a second input of the first power amplifier loop 12 and a second input of the second power amplifier loop 14 are both connected to an output of the common mode voltage generating module 16.
The common-mode voltage generating module 16 is configured to generate a common-mode voltage signal VREF for maintaining stability of output signals of the first current source module 11 and the second current source module 13.
Further, as shown in fig. 2, the first power amplifier loop 12 includes a fifth operational amplifier 21, a power amplifier loop driving module 23, a first capacitor C1, a field effect transistor P1 and a field effect transistor N1;
The inverting input end of the fifth operational amplifier 21 is connected with the output end of the first current source module 11, the non-inverting input end of the fifth operational amplifier 21 is connected with the output end of the common-mode voltage generating module 16, the output end of the fifth operational amplifier 21 is connected with the input end of the power amplifier loop driving module 23, the first output end of the power amplifier loop driving module 23 is connected with the gate of the field effect transistor P1, and the second output end of the power amplifier loop driving module 23 is connected with the gate of the field effect transistor N1.
The source electrode of the field effect tube P1 is connected with the voltage input end PVDD, the drain electrode of the field effect tube P1 is connected with the drain electrode of the field effect tube N1, the source electrode of the field effect tube N1 is grounded, and the connection node of the field effect tube P1 and the field effect tube N1 is used as the output end VOUTP of the first power amplifier loop 12.
The first capacitor C1 has a first end connected to the output terminal of the fifth operational amplifier 21, and a second end connected to the inverting input terminal of the fifth operational amplifier 21.
Further, as shown in fig. 2, the second power amplifier loop 14 includes a sixth operational amplifier 22, a power amplifier loop driving module 24, a second capacitor C2, a field effect transistor P2 and a field effect transistor N2;
The inverting input end of the sixth operational amplifier 22 is connected with the output end of the second current source module 13, the non-inverting input end of the sixth operational amplifier 22 is connected with the output end of the common-mode voltage generating module 16, the output end of the sixth operational amplifier 22 is connected with the input end of the power amplifier loop driving module 24, the first output end of the power amplifier loop driving module 24 is connected with the gate of the field effect transistor P2, and the second output end of the power amplifier loop driving module 24 is connected with the gate of the field effect transistor N2.
The source electrode of the field effect transistor P2 is connected with the voltage input end PVDD, the drain electrode of the field effect transistor P2 is connected with the drain electrode of the field effect transistor N2, the source electrode of the field effect transistor N2 is grounded, and the connection node of the field effect transistor P2 and the field effect transistor N2 is used as the output end VOUTN of the second power amplifier loop 14.
The first end of the second capacitor C2 is connected to the output end of the sixth operational amplifier 22, and the second end is connected to the inverting input end of the sixth operational amplifier 22.
Further, as shown in fig. 2, the feedback module 15 includes: the first feedback resistor RFB1, the second feedback resistor RFB2, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, and the tenth switch S10;
the input end of the third switch S3 and the input end of the fourth switch S4 are both connected with the first input end of the first power amplifier loop 12;
the output end of the fifth switch S5 and the output end of the sixth switch S6 are both connected with the output end of the first power amplifier loop 12;
the input end of the seventh switch S7 and the input end of the eighth switch S8 are both connected with the first input end of the second power amplifier loop 14;
the output end of the ninth switch S9 and the output end of the tenth switch S10 are both connected with the output end of the second power amplifier loop 14;
The output end of the third switch S3 and the output end of the seventh switch S7 are both connected with the first end of the first feedback resistor RFB1, the second end of the first feedback resistor RFB1 is connected with the first end of the first resistor R1, and the second end of the first resistor R1 is respectively connected with the input end of the fifth switch S5 and the input end of the ninth switch S9;
the first end of the second resistor R2 is connected with the first end of the first resistor R1, and the second end of the second resistor R2 is grounded;
The output end of the fourth switch S4 and the output end of the eighth switch S8 are both connected to the first end of the second feedback resistor RFB2, the second end of the second feedback resistor RFB2 is connected to the first end of the third resistor R3, and the second end of the third resistor R3 is connected to the input end of the sixth switch S6 and the input end of the tenth switch S10, respectively;
the first end of the fourth resistor R4 is connected with the first end of the third resistor R3, and the second end of the fourth resistor R4 is grounded;
the control terminals of the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9 and the tenth switch S10 are configured to receive the control signals, where the control signals are configured to control the operating states of the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9 and the tenth switch S10;
when the third switch S3, the fifth switch S5, the eighth switch S8 and the tenth switch S10 are in an on state, the remaining switches are in an off state;
When the fourth switch S4, the sixth switch S6, the seventh switch S7, and the ninth switch S9 are in the on state, the remaining switches are in the off state.
It should be noted that, by setting the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4, the digital audio power amplifier system generates a higher output voltage.
Optionally, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, and the tenth switch S10 are field effect transistors.
Optionally, the third switch S3, the fifth switch S5, the eighth switch S8, and the tenth switch S10 are P-type field effect transistors;
the fourth switch S4, the sixth switch S6, the seventh switch S7, and the ninth switch S9 are N-type field effect transistors.
Optionally, the third switch S3, the fifth switch S5, the eighth switch S8, and the tenth switch S10 are N-type field effect transistors;
The fourth switch S4, the sixth switch S6, the seventh switch S7, and the ninth switch S9 are P-type field effect transistors.
Further, as shown in fig. 3, the common-mode voltage generating module 16 includes: a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a capacitor C;
the first end of the fifth resistor R5 is connected with the voltage input end PVDD, the second end of the fifth resistor R5 is connected with the first end of the sixth resistor R6, the second end of the sixth resistor R6 is connected with the first end of the seventh resistor R7, and the second end of the seventh resistor R7 is grounded;
The first end of the eighth resistor R8 is connected with the first end of the seventh resistor R7, the second end of the eighth resistor R8 is connected with the first end of the capacitor C, and the second end of the capacitor C is connected with the second end of the seventh resistor R7;
the connection node of the eighth resistor R8 and the capacitor C serves as the output terminal VREF of the common-mode voltage generating module 16.
Wherein, the resistance values of the fifth resistor R5, the sixth resistor R6 and the seventh resistor R7 are the same.
The principles of the first current source module 11 and the second current source module 13 are first described in the above-mentioned digital audio power amplifier system according to the embodiment of the present invention.
Wherein the equivalent output impedance ro1p of the first fet M1, the second fet M2 and the first operational amplifier 111 is,
ro1p＝A×gm2×ro1×ro2
Where a is the dc gain of the first operational amplifier 111, g m2 is the transconductance of the second fet M2, ro 1 is the output impedance of the first fet M1, and ro 2 is the output impedance of the second fet M2.
The equivalent output impedances ro1n of the third fet M3, the fourth fet M4 and the second operational amplifier 112 are,
ro1n＝A×gm3×ro3×ro4
Where a is the dc gain of the second operational amplifier 112, g m3 is the transconductance of the third fet M3, ro 3 is the output impedance of the third fet M3, and ro 4 is the output impedance of the fourth fet M4.
The output impedance rop of the first current source module 11 is then,
rop＝ro1p//ro1n
The output impedance rop of the first current source module 11 is much larger than the first feedback resistor RFB1 or the second feedback resistor RFB2.
Similarly, the equivalent output impedances ro2p of the fifth fet M5, the sixth fet M6 and the third operational amplifier 131 are,
ro2p＝A×gm6×ro5×ro6
Where a is the dc gain of the third operational amplifier 131, g m6 is the transconductance of the sixth fet M6, ro 5 is the output impedance of the fifth fet M5, and ro 6 is the output impedance of the sixth fet M6.
The equivalent output impedances ro2n of the seventh fet M7, eighth fet M8 and fourth op amp 132 are,
ro2n＝A×gm7×ro7×ro8
Wherein a is the dc gain of the fourth operational amplifier 132, g m7 is the transconductance of the seventh fet M7, ro 7 is the output impedance of the seventh fet M7, and ro 8 is the output impedance of the eighth fet M8.
The output impedance ron of the second current source module 13 is then,
ron＝ro2p//ro2n
The output impedance ron of the second current source module 13 is much larger than the first feedback resistor RFB1 or the second feedback resistor RFB2.
Therefore, in the digital audio power amplifier system, the output impedance of the first current source module 11 and the second current source module 13 is increased, so that the influence of the first current source module 11 and the second current source module 13 on the power supply rejection ratio is reduced, and noise on the loudspeaker is reduced.
As shown in fig. 2, the first resistor R1 and the second resistor R2 form a voltage division, and the third resistor R3 and the fourth resistor R4 form a voltage division, and the r4=2xr3 is set, at this time, the highest voltage at the output ends of the first subsystem and the second subsystem is 2/3 times that of the voltage input end PVDD, the common-mode voltage signal VREF becomes 1/3 times that of the voltage input end PVDD, which means that when the voltage input end PVDD is 10V, the common-mode voltage signal VREF is 3.3V, and under the condition that the power voltages of the first current source module, the second current source module, the first power amplifier loop and the second power amplifier loop are equal to 5V, the circuit can still work normally, and the function of high-voltage output is further realized.
Based on the digital audio power amplification system provided in the foregoing, when the feedback module 15 is not provided with the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7 and the eighth switch S8, the feedback module 15 is divided into two parts, one part is formed by the first feedback resistor RFB1, the first resistor R1 and the second resistor R2, and is correspondingly connected with the first subsystem, and the other part is formed by the second feedback resistor RFB2, the third resistor R3 and the fourth resistor R4, and is correspondingly connected with the second subsystem.
As can be seen from the above description, the output impedance of the first current source module 11 is rop, and the output impedance of the second current source module 13 is ron.
The signal ripple Δvip at the output Vip of the first current source module 11 is,
Where ΔV OUTP is the output ripple of output V OUTP of the first subsystem.
Since the gain of the first power amplifier loop 12 is very large at the low frequency band, the gain from the input VREF of the fifth operational amplifier 21 to Vip is equal to 1, and thus,
Where Δpvdd is the voltage ripple at the voltage input.
The finishing is carried out so as to obtain the finished products,
In the same way, it is known that,
Where ΔV OUTN is the output ripple of output V OUTN of the second subsystem.
Because in the actual manufacturing process, the resistance values of the resistors can fluctuate to a certain extent, the voltage dividing ratio and the design value of the first resistor R 1, the second resistor R 2, the third resistor R 3 and the fourth voltage R 4 can deviate, and meanwhile, the resistance values of the first feedback resistor R FB1 and the second feedback resistor R FB2 are not completely equal.
It is assumed that the number of the sub-blocks,
Since the output impedance of the first current source module 11 is rop and the output impedance of the second current source module 13 is ron, which is much larger than the first feedback resistor R FB1 and the second feedback resistor R FB2, the difference between β1 and β2 has negligible effect on PSRR even if the resistances of the first feedback resistor R FB1 and the second feedback resistor R FB2 are not exactly equal.
It is again assumed that,
α1-α2＝Δα
It can then be concluded that the number of the cells,
ΔVOUT＝ΔVOUTP-ΔVOUTN
Wherein DeltaV OUT is the total output fluctuation of the digital audio power amplifier system.
That is to say,
Then, the power supply rejection ratio PSRR of the digital audio power amplifier system is,
From the above formula, the main factor affecting the power supply rejection ratio PSRR of the high-voltage digital audio power amplifier system is the matching degree of the first resistor R 1, the second resistor R 2, the third resistor R 3 and the fourth voltage R 4.
Therefore, in this embodiment, by setting the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, and the tenth switch S10, the feedback module 15 is used by switching between the PWMP signal period and the PWMN signal period, for example, when the control signal SWAP is at a high level, the third switch S3, the fifth switch S5, the eighth switch S8, and the tenth switch S10 are in an on state, and the remaining switches are in an off state, and the output terminal V OUTP of the first subsystem is configured to sink or sink a current to the output terminal Vip of the first current source module through the first feedback resistor R FB1, the first resistor R 1, and the second resistor R 2, and at this time, the output terminal V OUTN of the second subsystem is configured to sink a current to the output terminal Vip of the first current source module through the second feedback resistor R FB2, the third resistor R 3, and the fourth resistor R 4. When the SWAP signal is at low level, the fourth switch S4, the sixth switch S6, the seventh switch S7, and the ninth switch S9 are in on states, and the other switches are in off states, so that the output terminal V OUTP of the first subsystem injects or extracts current to the output terminal Vip of the first current source module through the second feedback resistor R FB2, the third resistor R 3, and the fourth resistor R 4, and at this time, the output terminal V OUTN of the second subsystem injects or extracts current to the output terminal Vin of the second current source module through the first feedback resistor R FB1, the first resistor R 1, and the second resistor R 2.
The PWMP signal period and the PWMN signal period are the same as the SWAP signal period.
Thus, it can be derived that,
At this time, the feedback ratio of the output end V OUTP of the first subsystem is the same as the feedback ratio of the output end V OUTN of the second subsystem, and the voltage dividing resistance mismatch factor Δα caused by the manufacturing process in the PSRR formula of the power supply rejection ratio can be perfectly eliminated, so as to further improve the power supply rejection ratio PSRR of the digital audio power amplifier system.
The above describes a digital audio power amplifier system provided by the present invention in detail, and specific examples are applied to illustrate the principles and embodiments of the present invention, and the above examples are only used to help understand the method and core ideas of the present invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include, or is intended to include, elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A digital audio power amplifier system, comprising: a first current source module and a first power amplifier loop; the first current source module includes: the first field effect transistor, the second field effect transistor, the third field effect transistor, the fourth field effect transistor, the first switch, the second switch, the first operational amplifier and the second operational amplifier;
the source electrode of the first field effect tube is connected with a power supply voltage end, the drain electrode of the first field effect tube is respectively connected with the source electrode of the second field effect tube and the inverting input end of the first operational amplifier, and the grid electrode of the first field effect tube is connected with a first voltage signal input end;
The drain electrode of the second field effect transistor is connected with the input end of the first switch, and the grid electrode of the second field effect transistor is connected with the output end of the first operational amplifier;
the non-inverting input end of the first operational amplifier is connected with the second voltage signal input end;
the output end of the first switch is connected with the input end of the second switch, and the output end of the second switch is connected with the drain electrode of the third field effect transistor;
The source electrode of the third field effect transistor is respectively connected with the inverting input end of the second operational amplifier and the drain electrode of the fourth field effect transistor, and the grid electrode of the third field effect transistor is connected with the output end of the second operational amplifier;
the non-inverting input end of the second operational amplifier is connected with the third voltage signal input end;
The grid electrode of the fourth field effect transistor is connected with the fourth voltage signal input end, and the source electrode of the fourth field effect transistor is grounded;
The first current source module and the first power amplifier loop form a first subsystem, the control end of the first switch and the control end of the second switch are used as signal input ends of the first subsystem and are used for receiving PWMP signals, the connection nodes of the first switch and the second switch are connected with the first input end of the first power amplifier loop, and the output end of the first power amplifier loop is used as a signal output end of the first subsystem;
the digital audio power amplifier system further comprises: the second current source module and the second power amplifier loop;
the second current source module and the second power amplifier loop form a second subsystem, the signal input end of the second subsystem is used for receiving PWMN signals, and the output end of the second power amplifier loop is used as the signal output end of the second subsystem;
The digital audio power amplifier system further comprises: a feedback module;
The first input end of the feedback module is connected with the first input end of the first power amplifier loop, and the first output end of the feedback module is connected with the output end of the first power amplifier loop;
the second input end of the feedback module is connected with the first input end of the second power amplifier loop, and the second output end of the feedback module is connected with the output end of the second power amplifier loop;
The control end of the feedback module is used for receiving a control signal, and the control signal is used for controlling the feedback module to be in different working states so as to adjust the resistance matching degree of the first subsystem and the second subsystem and further adjust the power supply rejection ratio of the digital audio power amplifier system;
The feedback module comprises: a first feedback resistor, a second feedback resistor, a first resistor, a second resistor, a third resistor, a fourth resistor, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a ninth switch, and a tenth switch;
The input end of the third switch and the input end of the fourth switch are connected with the first input end of the first power amplifier loop;
the output end of the fifth switch and the output end of the sixth switch are connected with the output end of the first power amplifier loop;
the input end of the seventh switch and the input end of the eighth switch are connected with the first input end of the second power amplifier loop;
The output end of the ninth switch and the output end of the tenth switch are connected with the output end of the second power amplifier loop;
the output end of the third switch and the output end of the seventh switch are connected with the first end of the first feedback resistor, the second end of the first feedback resistor is connected with the first end of the first resistor, and the second end of the first resistor is respectively connected with the input end of the fifth switch and the input end of the ninth switch;
the first end of the second resistor is connected with the first end of the first resistor, and the second end of the second resistor is grounded;
the output end of the fourth switch and the output end of the eighth switch are connected with the first end of the second feedback resistor, the second end of the second feedback resistor is connected with the first end of the third resistor, and the second end of the third resistor is respectively connected with the input end of the sixth switch and the input end of the tenth switch;
the first end of the fourth resistor is connected with the first end of the third resistor, and the second end of the fourth resistor is grounded;
The control ends of the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch are used for receiving the control signals, and the control signals are used for controlling the working states of the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch, the ninth switch and the tenth switch;
When the third switch, the fifth switch, the eighth switch and the tenth switch are in a conducting state, the other switches are in a closing state;
When the fourth switch, the sixth switch, the seventh switch and the ninth switch are in an on state, the rest switches are in an off state.
2. The digital audio power amplifier system of claim 1, wherein the first field effect transistor and the second field effect transistor are P-type field effect transistors;
the third field effect transistor and the fourth field effect transistor are N-type field effect transistors.
3. The digital audio power amplifier system of claim 1, wherein,
The circuit structure of the second current source module is the same as that of the first current source module, and the circuit structure of the second power amplifier loop is the same as that of the first power amplifier loop.
4. The digital audio power amplifier system of claim 1, wherein,
The periods of the control signal, the PWMP signal, and the PWMN signal are the same.
5. The digital audio power amplifier system according to claim 4, wherein the third switch, the fifth switch, the eighth switch and the tenth switch are P-type field effect transistors;
the fourth switch, the sixth switch, the seventh switch and the ninth switch are N-type field effect transistors.
6. The digital audio power amplifier system according to claim 5, wherein the third switch, the fifth switch, the eighth switch and the tenth switch are N-type field effect transistors;
The fourth switch, the sixth switch, the seventh switch and the ninth switch are P-type field effect transistors.
7. The digital audio power amplifier system of claim 3, further comprising: a common mode voltage generating module;
And the second input end of the first power amplifier loop and the second input end of the second power amplifier loop are connected with the output end of the common-mode voltage generating module.
8. The digital audio power amplifier system of claim 7, wherein the common mode voltage generation module comprises: a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor and a capacitor;
the first end of the fifth resistor is connected with the voltage input end, the second end of the fifth resistor is connected with the first end of the sixth resistor, the second end of the sixth resistor is connected with the first end of the seventh resistor, and the second end of the seventh resistor is grounded;
The first end of the eighth resistor is connected with the first end of the seventh resistor, the second end of the eighth resistor is connected with the first end of the capacitor, and the second end of the capacitor is connected with the second end of the seventh resistor;
And a connecting node of the eighth resistor and the capacitor is used as an output end of the common-mode voltage generating module.
9. The digital audio power amplifier system according to claim 8, wherein the fifth resistor, the sixth resistor, and the seventh resistor have the same resistance value.
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| CN109660917B (en) * | 2018-12-26 | 2023-09-15 | 上海艾为电子技术股份有限公司 | High-voltage digital audio power amplifier system |
| CN109546978B (en) * | 2019-01-15 | 2023-09-19 | 上海艾为电子技术股份有限公司 | Current detection circuit of loudspeaker |
| CN109672413A (en) * | 2019-01-31 | 2019-04-23 | 上海艾为电子技术股份有限公司 | Digital analog converter, digital power amplifier subsystem, digital power amplifier system |
| CN109842381A (en) * | 2019-01-31 | 2019-06-04 | 上海艾为电子技术股份有限公司 | Digital analog converter, digital power amplifier subsystem, digital power amplifier system |
| CN110149445B (en) * | 2019-06-06 | 2020-10-30 | 四川赛科安全技术有限公司 | Fire-fighting extension telephone voice return circuit and implementation method |
| CN110768635A (en) * | 2019-11-29 | 2020-02-07 | 上海艾为电子技术股份有限公司 | Audio power amplifier and electronic equipment |
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