CN207266266U - Analog differential circuit and audio frequency apparatus - Google Patents
Analog differential circuit and audio frequency apparatus Download PDFInfo
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- CN207266266U CN207266266U CN201721263155.XU CN201721263155U CN207266266U CN 207266266 U CN207266266 U CN 207266266U CN 201721263155 U CN201721263155 U CN 201721263155U CN 207266266 U CN207266266 U CN 207266266U
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Abstract
The utility model discloses a kind of analog differential circuit and audio frequency apparatus, which includes：The Butterworth filter circuit that the audio signal of access is converted into exporting after negative differential signal, its input terminal are used for incoming audio signal, its output terminal is connected with the first input end of differential signal output circuit and the input terminal of low-pass filter circuit respectively；After the negative differential signal that Butterworth filter circuit is exported carries out anti-phase and filtering process, obtain principal-employment sub-signal and the low-pass filter circuit exported, its output terminal are connected with the second input terminal of differential signal output circuit；The differential signal output circuit for negative differential signal and principal-employment sub-signal export after divider filter processing, its decoding circuit of the first output terminal and the second output terminal respectively with the audio frequency apparatus are connected.The utility model significantly reduces the requirement to amplifier common-mode rejection ratio, so as to fulfill the requirement of the audio performances such as signal-to-noise ratio, distortion is improved.
Description
Technical Field
The utility model relates to an electronic circuit technical field, in particular to analog differential circuit and audio equipment.
Background
In audio equipment such as a television and a stereo, a received analog signal is generally output to an audio system of the audio equipment. In order to solve the problem that analog signals are easily interfered and are not suitable for long-distance transmission, a differential circuit is usually adopted to convert the analog signals into differential transmission so as to improve the anti-interference capability.
At present, most of differential circuits are formed by using a same phase ratio circuit and an inverse phase ratio circuit. However, the in-phase proportional circuit in such a differential circuit has a high requirement for the operational amplifier common mode rejection ratio, and cannot meet the requirement for improving the audio performance such as the signal-to-noise ratio and the distortion.
SUMMERY OF THE UTILITY MODEL
The main objective of the present invention is to provide a method for effectively reducing the requirement of the operational amplifier common mode rejection ratio, thereby achieving the requirement of improving the audio performance such as the signal-to-noise ratio and the distortion.
In order to achieve the above object, the present invention provides an analog differential circuit applied to an audio device, wherein the analog differential circuit comprises a Butterworth filter circuit, a low-pass filter circuit and a differential signal output circuit, an input end of the Butterworth filter circuit is used for accessing an audio signal, and an output end of the Butterworth filter circuit is connected to a first input end of the differential signal output circuit and an input end of the low-pass filter circuit respectively; the output end of the low-pass filter circuit is connected with the second input end of the differential signal output circuit; the first output end and the second output end of the differential signal output circuit are respectively connected with a decoding circuit of the audio equipment; wherein,
the Butterworth filter circuit is used for converting the accessed audio signal into a negative differential signal and outputting the negative differential signal;
the low-pass filter circuit is used for carrying out phase inversion and filtering processing on the negative differential signal output by the Butterworth filter circuit to obtain a positive differential signal and outputting the positive differential signal;
and the differential signal output circuit is used for performing voltage division filtering processing on the negative differential signal and the positive differential signal and outputting the processed signals to a decoding circuit of the audio equipment.
Preferably, the butterworth filter circuit comprises:
the first Butterworth filtering unit is used for converting a left channel audio signal accessed into the audio signal into a left channel negative differential signal and outputting the left channel negative differential signal;
and the second Butterworth filtering unit is used for converting the right channel audio signal accessed into the audio signal into a right channel negative differential signal and outputting the right channel negative differential signal.
Preferably, the first butterworth filter unit comprises a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, a third resistor and a first operational amplifier, wherein a first end of the first capacitor is an input end of the first butterworth filter unit, a second end of the first capacitor is interconnected with a first end of the second resistor, a first end of the third resistor and a first end of the second capacitor through the first resistor, and a second end of the second resistor is interconnected with an inverting input end of the first operational amplifier and a first end of the third capacitor; an output terminal of the first operational amplifier is an output terminal of the first butterworth filter unit and is interconnected with a second terminal of the third resistor and a second terminal of the third capacitor; the positive phase input end of the first operational amplifier is connected with a first direct current power supply; and the second end of the second capacitor is grounded.
Preferably, the second butterworth filter unit comprises a fourth capacitor, a fifth capacitor, a sixth capacitor, a fourth resistor, a fifth resistor, a sixth resistor and a second operational amplifier, wherein a first end of the fourth capacitor is an input end of the second butterworth filter unit, a second end of the fourth capacitor is interconnected with a first end of the fifth resistor, a first end of the sixth resistor and a first end of the fifth capacitor through the fourth resistor, and a second end of the fifth resistor is interconnected with an inverting input end of the second operational amplifier and a first end of the sixth capacitor; an output terminal of the second operational amplifier is an output terminal of the second butterworth filtering unit and is interconnected with a second terminal of the sixth resistor and a second terminal of the sixth capacitor; the positive phase input end of the second operational amplifier is connected with a second direct current power supply; and the second end of the fifth capacitor is grounded.
Preferably, the low-pass filter circuit includes:
the first low-pass filtering unit is used for converting the left channel negative differential signal output by the first Butterworth filtering unit into a left channel positive differential signal and outputting the left channel positive differential signal;
and the second low-pass filtering unit is used for converting the right channel negative differential signal output by the second Butterworth filtering unit into a right channel positive differential signal and outputting the right channel positive differential signal.
Preferably, the first low-pass filtering unit includes a seventh capacitor, a seventh resistor, an eighth resistor, and a third operational amplifier, a first end of the seventh resistor is an input end of the first low-pass filtering unit, and a second end of the seventh resistor is interconnected with an inverting input end of the third operational amplifier, a first end of the eighth resistor, and a first end of the seventh capacitor; an output end of the third operational amplifier is an output end of the first low-pass filtering unit, and is interconnected with a second end of the eighth resistor and a second end of the seventh capacitor; and the positive phase input end of the third operational amplifier is connected with a first direct current power supply.
Preferably, the second low-pass filtering unit includes an eighth capacitor, a ninth resistor, a tenth resistor and a fourth operational amplifier, a first end of the ninth resistor is an input end of the second low-pass filtering unit, and a second end of the ninth resistor is interconnected with an inverting input end of the fourth operational amplifier, a first end of the tenth resistor and a first end of the eighth capacitor; an output end of the fourth operational amplifier is an output end of the first low-pass filtering unit, and is interconnected with a second end of the tenth resistor and a second end of the eighth capacitor; and the positive phase input end of the fourth operational amplifier is connected with a second direct current power supply.
Preferably, the differential signal output circuit includes a plurality of voltage dividing units and blocking capacitors corresponding to the voltage dividing units, the input ends of the voltage dividing units are connected to the output ends of the low-pass filter circuit in a one-to-one correspondence, the output ends of the voltage dividing units are connected to the first ends of the blocking capacitors in a one-to-one correspondence, and the second ends of the blocking capacitors are connected to the input ends of the decoding circuit in a one-to-one correspondence.
The utility model also provides an audio device, which comprises a decoding circuit and the analog differential circuit; the analog differential circuit comprises a Butterworth filter circuit, a low-pass filter circuit and a differential signal output circuit, wherein the input end of the Butterworth filter circuit is used for accessing an audio signal, and the output end of the Butterworth filter circuit is respectively connected with the first input end of the differential signal output circuit and the input end of the low-pass filter circuit; the output end of the low-pass filter circuit is connected with the second input end of the differential signal output circuit; the first output end and the second output end of the differential signal output circuit are respectively connected with a decoding circuit of the audio equipment; the Butterworth filter circuit is used for converting the accessed audio signal into a negative differential signal and outputting the negative differential signal; the low-pass filter circuit is used for carrying out phase inversion and filtering processing on the negative differential signal output by the Butterworth filter circuit to obtain a positive differential signal and outputting the positive differential signal; and the differential signal output circuit is used for performing voltage division filtering processing on the negative differential signal and the positive differential signal and outputting the processed signals to a decoding circuit of the audio equipment.
Preferably, the decoding circuit comprises a decoding integrated chip.
In this embodiment, when it is detected that an analog signal is input to the left channel audio input interface and/or the right channel audio input interface, the butterworth filter circuit inverts and amplifies the analog signal input at a single end, converts the analog signal into a differential signal, and filters a high-frequency signal in the differential signal to obtain a negative differential signal, and outputs the negative differential signal to the input ends of the differential signal output circuit and the low-pass filter circuit. The low-pass filter circuit 20 performs 1:1 inversion processing on the accessed negative differential signal to convert the negative differential signal into a positive differential signal, and performs filtering processing on a high-frequency signal in the positive differential signal to obtain a positive differential signal, and then outputs the positive differential signal to the differential signal output circuit. The differential output circuit carries out blocking filtering processing on a negative differential signal output by the Butterworth filter circuit and a positive differential signal output by the low-pass filter circuit, carries out voltage division processing and then outputs the processed signals to a decoding circuit of an audio system, and therefore the purposes of converting a single-ended signal into a differential signal and transmitting the signal efficiently and with high quality are achieved. The utility model discloses a butterworth filter circuit and order low pass filter circuit are reverse phase proportion circuit, also are negative feedback circuit simultaneously, can reduce effectively to the requirement of putting common mode rejection ratio to fortune to realize improving requirements of audio performance such as SNR, distortion. The utility model discloses the analog signal of single-ended input changes differential signal output still has been realized, and then has solved analog signal and has received the interference more easily, is not suitable for more remote transmission's problem.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic diagram of a functional module of an embodiment of the present invention in which an analog differential circuit is applied to an audio device;
FIG. 2 is a schematic diagram of a circuit configuration of one embodiment of a Butterworth filter circuit and a low-pass filter circuit of the analog differential circuit of FIG. 1;
fig. 3 is a schematic circuit diagram of an embodiment of a differential signal output circuit of the analog differential circuit in fig. 1.
The objects, features and advantages of the present invention will be further described with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
It should be noted that, if directional indications (such as upper, lower, left, right, front and rear … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description relating to "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions in the embodiments may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
The utility model provides an analog differential circuit is applied to among the audio equipment.
The audio equipment can be audio equipment with an audio system, such as an android television, a portable computer, a mobile phone, a mini sound box, a multi-channel sound box sound bar and the like.
In these audio devices, it is common to output the received analog signal onto the audio system of the audio device. In order to solve the problem that analog signals are easily interfered and are not suitable for long-distance transmission, a differential circuit is usually adopted to convert the analog signals into differential transmission so as to improve the anti-interference capability.
The differential circuit is often configured by using a common phase ratio circuit and an inverting phase ratio circuit. However, the in-phase proportional circuit in such a differential circuit has a high requirement for the operational amplifier common mode rejection ratio, and cannot meet the requirement for improving the audio performance such as the signal-to-noise ratio and the distortion.
Referring to fig. 1 and 3, in order to solve the above problem, in an embodiment of the present invention, the analog differential circuit includes a butterworth filter circuit 10, a low pass filter circuit 20 and a differential signal output circuit 30, an input end of the butterworth filter circuit 10 is used for accessing an audio signal, and an output end of the butterworth filter circuit 10 is connected to a first input end of the differential signal output circuit 30 and an input end of the low pass filter circuit 20, respectively; the output end of the low-pass filter circuit 20 is connected with the second input end of the differential signal output circuit 30; a first output end and a second output end of the differential signal output circuit 30 are respectively connected with a decoding circuit of the audio device; wherein,
the Butterworth filter circuit 10 is configured to convert the accessed audio signal into a negative differential signal and output the negative differential signal;
the low-pass filter circuit 20 is configured to perform phase inversion and filtering processing on the negative differential signal output by the butterworth filter circuit 10 to obtain a positive differential signal and output the positive differential signal;
the differential signal output circuit 30 is configured to perform voltage division filtering on the negative differential signal and the positive differential signal, and output the signals to a decoding circuit of the audio device.
It should be noted that, audio input interfaces J1 are provided in the audio devices for inputting analog audio signals, and the audio input interface J1 includes a left channel audio input interface AUX-L and a right channel audio input interface AUX-R. In this embodiment, two input terminals of the butterworth filter circuit 10 are respectively connected to the left channel audio input interface AUX-L and the right channel audio input interface AUX-R, so as to access the analog audio signal input by the single terminal, which is hereinafter referred to as an analog signal.
The butterworth filter circuit 10, i.e., the infinite gain multi-path feedback circuit, inverts and amplifies the analog signal input at a single end and converts the analog signal into a differential signal, and filters a high-frequency signal in the differential signal to obtain a negative differential signal.
The input end of the low-pass filter circuit 20 is connected to the output end of the butterworth filter circuit 10, so as to perform 1:1 phase inversion processing on the accessed negative differential signal to convert the negative differential signal into a positive differential signal, and perform filtering processing on a high-frequency signal in the positive differential signal to obtain a positive differential signal.
The input end of the differential signal output circuit 30 is connected to the output end of the butterworth filter circuit 10 and the output end of the low-pass filter circuit 20, so as to perform blocking filtering processing on the negative differential signal output by the butterworth filter circuit 10 and the positive differential signal output by the low-pass filter circuit 20, perform voltage division processing, and output the processed signals to a decoding circuit of an audio system, thereby realizing the conversion of the single-ended signal into the differential signal and the high-efficiency and high-quality transmission.
In this embodiment, when it is detected that analog signals are input to the left channel audio input interface J1 and/or the right channel audio input interface J1, the butterworth filter circuit 10 inverts and amplifies the analog signals input at a single end to convert the analog signals into differential signals, and filters high-frequency signals in the differential signals to obtain negative differential signals, and outputs the negative differential signals to the input terminals of the differential signal output circuit 30 and the low-pass filter circuit 20. The low-pass filter circuit 20 performs 1:1 inversion processing on the accessed negative differential signal to convert the negative differential signal into a positive differential signal, and performs filtering processing on a high-frequency signal in the positive differential signal to obtain a positive differential signal, and then outputs the positive differential signal to the differential signal output circuit 30. The differential output circuit performs blocking filtering processing on the negative differential signal output by the Butterworth filter circuit 10 and the positive differential signal output by the low-pass filter circuit 20, performs voltage division processing, and outputs the processed signals to a decoding circuit of an audio system, so that the single-ended signal is converted into the differential signal and high-efficiency and high-quality transmission is realized. The utility model discloses a Butterworth filter circuit 10 and order low pass filter circuit 20 are reverse phase proportion circuit, also are negative feedback circuit simultaneously, can reduce the requirement of putting common mode rejection ratio to fortune effectively to realize improving audio performance's such as SNR, distortion requirements. The utility model discloses the analog signal of single-ended input changes differential signal output still has been realized, and then has solved analog signal and has received the interference more easily, is not suitable for more remote transmission's problem.
Referring to fig. 1 and 3, in a preferred embodiment, the butterworth filter circuit 10 includes:
the first butterworth filtering unit 11 is configured to convert a left channel audio signal accessed into the audio signal into a left channel negative differential signal and output the left channel negative differential signal;
and the second Butterworth filtering unit 12 is used for converting the right channel audio signal accessed into the audio signal into a right channel negative differential signal and outputting the right channel negative differential signal.
In this embodiment, the input end of the first butterworth filtering unit 11 is connected to the left channel audio input interface AUX-L, so as to invert and amplify the accessed left channel analog audio signal and convert the inverted signal into a differential signal, and filter a high-frequency signal in the differential signal, so as to obtain a negative differential signal of the left channel. The input end of the second butterworth filtering unit 12 is connected to the right channel audio input interface AUX-R to invert and amplify the accessed right channel analog audio signal and convert the inverted signal into a differential signal, and filter out a high-frequency signal in the differential signal to obtain a negative differential signal of the right channel.
Referring to fig. 1 and fig. 3, in the above embodiment, the first butterworth filtering unit 11 includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a first resistor R1, a second resistor R2, a third resistor R3 and a first operational amplifier U1, a first end of the first capacitor C1 is an input end of the first butterworth filtering unit 11, a second end of the first capacitor C1 is interconnected with a first end of the second resistor R2, a first end of the third resistor R3 and a first end of the second capacitor C2 through the first resistor R1, and a second end of the second resistor R2 is interconnected with an inverting input end of the first operational amplifier U1 and a first end of the third capacitor C3; the output terminal of the first operational amplifier U1 is the output terminal of the first butterworth filter unit 11 and is interconnected with the second terminal of the third resistor R3 and the second terminal of the third capacitor C3; the non-inverting input end of the first operational amplifier U1 is connected with a first direct current power supply VCC 1; the second end of the second capacitor C2 is grounded.
In this embodiment, the first butterworth filtering unit 11 is a deep negative feedback to make the circuit operate stably. Wherein, the gain of the first Butterworth filter unit 11 can be adjusted according to the ratio of the resistance of the first resistor R1 and the third resistor R3. The first resistor R1 and the second capacitor C2 form an RC filter to filter noise in the analog signal, the second resistor R2 and the third capacitor C3 form an RC integrating circuit, and the RC filter and the RC integrating circuit both have low-pass characteristics. The cut-off frequency f0 of the first butterworth filter unit 11 is adjusted according to the parameters of the second resistor R2, the third resistor R3, the second capacitor C2 and the third capacitor C3, and can be specifically calculated according to the following formula:
wherein, the values of the parameters C2, C3, R2, and R3 are respectively the second capacitor C2, the third capacitor C3, the second resistor R2, and the third resistor R3, when there are interference noise signals (i.e. high-frequency noise) in the analog audio signal input by the audio input interface J1 due to various factors, and when the noise frequency is greater than the cutoff frequency f0, the noise can be filtered by the filter circuit formed by the second resistor R2, the third resistor R3, the second capacitor C2, and the third capacitor C3, and the cutoff frequency f0 is about 45KHZ in this embodiment. It can be understood that the first butterworth filtering unit 11 of the present embodiment is a second-order filter, which has better filtering effect and better cut-off frequency characteristic than the first-order filter.
Referring to fig. 1 and 3, in the above embodiment, the second butterworth filtering unit 12 includes a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a second operational amplifier U2, a first end of the fourth capacitor C4 is an input end of the first butterworth filtering unit 11, a second end of the fourth capacitor C4 is interconnected with a first end of the fifth resistor R5, a first end of the sixth resistor R6 and a first end of the fifth capacitor C5 through the fourth resistor R4, and a second end of the fifth resistor R5 is interconnected with an inverting input end of the second operational amplifier U2 and a first end of the sixth capacitor C6; the output terminal of the second operational amplifier U2 is the output terminal of the second butterworth filter unit 12 and is interconnected with the second terminal of the sixth resistor R6 and the second terminal of the sixth capacitor C6; the non-inverting input end of the second operational amplifier U2 is connected with a second direct current power supply VCC 2; the second terminal of the fifth capacitor C5 is grounded.
In this embodiment, the second butterworth filter unit 12 is a deep negative feedback to make the circuit operate stably. Wherein, the gain of the second Butterworth filter unit 12 can be adjusted according to the ratio of the resistance of the fourth resistor R4 and the resistance of the sixth resistor R6. The first resistor R1 and the second capacitor C2 form an RC filter to filter noise in the analog signal, the second resistor R2 and the third capacitor C3 form an RC integrating circuit, and the RC filter and the RC integrating circuit both have low-pass characteristics. The cut-off frequency f0 of the first butterworth filter unit 11 is adjusted according to the parameters of the second resistor R2, the third resistor R3, the second capacitor C2 and the third capacitor C3, and can be specifically calculated according to the following formula:
wherein, the values of the parameters C5, C6, R5, and R6 are respectively the fifth capacitor C5, the sixth capacitor C6, the fifth resistor R5, and the sixth resistor R6, when there are interference noise signals (i.e. high-frequency noise) in the analog audio signal input by the audio input interface J1 due to various factors, and when the noise frequency is greater than the cutoff frequency f0, the noise can be filtered by the filter circuit formed by the fifth resistor R5, the sixth resistor R6, the fifth capacitor C5, and the sixth capacitor C6, and the cutoff frequency f0 is about 45KHZ in this embodiment. It can be understood that the second butterworth filtering unit 12 of the present embodiment is a second-order filter, which has better filtering effect and better cut-off frequency characteristic than the first-order filter.
Referring to fig. 1 and 3, in a preferred embodiment, the low pass filter circuit 20 includes:
a first low-pass filtering unit 21, configured to convert the left channel negative differential signal output by the first butterworth filtering unit 11 into a left channel positive differential signal and output the left channel positive differential signal;
and a second low-pass filtering unit 22, configured to convert the right channel negative differential signal output by the second butterworth filtering unit 12 into a right channel positive differential signal and output the right channel positive differential signal.
In this embodiment, the first low-pass filtering unit 21 is connected to the output end of the first butterworth filtering unit 11, and performs 1:1 phase inversion on the negative differential signal of the left channel output by the first butterworth filtering unit 11, and obtains a positive differential signal of the left channel after filtering processing. The second low-pass filtering unit 22 is connected to the output end of the second butterworth filtering unit 12, and performs 1:1 phase inversion on the negative differential signal of the right channel output by the second butterworth filtering unit 12, and obtains a positive differential signal of the right channel after filtering processing.
Referring to fig. 1 and fig. 3, in the above embodiment, the first low-pass filtering unit 21 includes a seventh capacitor C7, a seventh resistor R7, an eighth resistor R8 and a third operational amplifier U3, a first end of the seventh resistor R7 is an input end of the first low-pass filtering unit 21, and a second end of the seventh resistor R7 is interconnected with an inverting input end of the third operational amplifier U3, a first end of the eighth resistor R8 and a first end of the seventh capacitor C7; an output terminal of the third operational amplifier U3 is an output terminal of the first low pass filtering unit 21 and is interconnected with a second terminal of the eighth resistor R8 and a second terminal of the seventh capacitor C7; the non-inverting input terminal of the third operational amplifier U3 is connected to a first dc power source VCC 1.
In this embodiment, the seventh resistor R7 and the eighth resistor R8 have the same resistance value, so as to implement 1:1 phase inversion of the negative differential signal of the left channel, and therefore, the negative differential signal does not need to be amplified or reduced, and only needs to be inverted. The seventh capacitor C7 is used to realize that the high frequency signal can be transmitted to the output terminal of the third operational amplifier U3 without being inverted, and the high frequency signal is added to the positive differential signal, and has the same phase and amplitude as the high frequency signal on the negative differential signal, so that the high frequency signal and the high frequency signal can be cancelled out, thereby improving the signal-to-noise ratio and the distortion of the differential.
Referring to fig. 1 and fig. 3, in the above embodiment, the second low-pass filtering unit 22 includes an eighth capacitor C8, a ninth resistor R9, a tenth resistor R10 and a fourth operational amplifier U4, a first end of the ninth resistor R9 is an input end of the second low-pass filtering unit 22, and a second end of the ninth resistor R9 is interconnected with an inverting input end of the fourth operational amplifier U4, a first end of the tenth resistor R10 and a first end of the eighth capacitor C8; an output terminal of the fourth operational amplifier U4 is an output terminal of the first low pass filtering unit 21, and is interconnected with a second terminal of the tenth resistor R10 and a second terminal of the eighth capacitor C8; the non-inverting input terminal of the fourth operational amplifier U4 is connected to a second dc power source VCC 2.
In this embodiment, the ninth resistor R9 and the tenth resistor R10 have the same resistance value to realize 1:1 phase inversion of the negative differential signal of the left channel, so that the negative differential signal does not need to be amplified or reduced, and only needs to be inverted. The eighth capacitor C8 is used to realize that the high frequency signal can be transmitted to the output terminal of the fourth operational amplifier U4 without being inverted, and the high frequency signal is added to the positive differential signal, and has the same phase and amplitude as the high frequency signal on the negative differential signal, so that the high frequency signal and the high frequency signal can be cancelled out, thereby improving the signal-to-noise ratio and the distortion of the differential.
Referring to fig. 1 and 3, it can be understood that, in the above embodiment, the first operational amplifier U1 and the third operational amplifier U3, and the second operational amplifier U2 and the fourth operational amplifier U4 are preferably implemented by using a dual-channel IC, and the dual-channel IC supplies power to the same power source. The whole circuit adopts four operational amplifiers, and all the operational amplifiers are connected in parallel and negatively fed back by voltage, so that the operational amplifier small signal works and is in a linear state. The utility model discloses make full use of inverting input and the lower characteristics of common mode rejection ratio requirement of homophase input satisfy higher SNR, distortion performance requirement.
A first power supply voltage division unit 41 is further disposed between the non-inverting input terminals of the first operational amplifier U1 and the third operational amplifier U3 and the first direct current power supply VCC1, the first power supply voltage division unit 41 includes an eleventh resistor R11, a twelfth resistor R12, a ninth capacitor C9 and a tenth capacitor C10, a first end of the eleventh resistor R11 is connected to the first direct current power supply VCC1, a second end of the eleventh resistor R11 is connected to first ends of the twelfth resistor R12, the ninth capacitor C9 and the tenth capacitor C10, and the non-inverting input terminals of the first operational amplifier U1 and the third operational amplifier U3 are interconnected; the second end of the eleventh resistor R11 and the second ends of the twelfth resistor R12, the ninth capacitor C9 and the tenth capacitor C10 are all grounded. The eleventh resistor R11 and the twelfth resistor R12 are connected in series to divide the power voltage of the first dc power source VCC1 into a divided voltage and output to the non-inverting input terminals of the first operational amplifier U1 and the third operational amplifier U3. The ninth capacitor C9 and the tenth capacitor C10 are used for filtering noise in the first dc power supply VCC 1. According to the voltage division principle, the larger the ratio of the eleventh resistor R11 to the twelfth resistor R12 is, the larger the voltage divided by the eleventh resistor R11 is. In this way, the reference voltages of the first operational amplifier U1 and the third operational amplifier U3 can be adjusted by adjusting the resistance of the eleventh resistor R11 and/or the twelfth resistor R12, so as to adjust the operation accuracy.
Similarly, a second power dividing unit 42 is further disposed between the non-inverting input terminals of the second operational amplifier U2 and the fourth operational amplifier and the second dc power VCC2, and the second power dividing unit 42 includes a thirteenth resistor R13, a fourteenth resistor R14, an eleventh capacitor C11, and a twelfth capacitor C12. The second power supply voltage dividing unit 42 has the same structure as the first power supply voltage dividing unit 41, so the working principle is the same and the technical effect is the same, and reference may be made to the first power supply voltage dividing unit 41 specifically, which is not described herein again.
Referring to fig. 1 and 3, in a preferred embodiment, the differential signal output circuit 30 includes a plurality of voltage dividing units and blocking capacitors (not shown) disposed corresponding to the voltage dividing units (not shown), wherein input ends of the voltage dividing units are respectively connected to output ends of the low pass filter circuit 20 in a one-to-one correspondence, output ends of the voltage dividing units are respectively connected to first ends of the blocking capacitors in a one-to-one correspondence, and second ends of the blocking capacitors are respectively connected to input ends of the decoding circuit in a one-to-one correspondence.
In this embodiment, a voltage dividing unit is respectively disposed at the output ends of the first butterworth filtering unit 11, the second butterworth filtering unit 12, the first low-pass filtering unit 21, and the second low-pass filtering unit 22, and is denoted as a first voltage dividing unit 31, a second voltage dividing unit 32, a third voltage dividing unit 33, and a fourth voltage dividing unit 34, wherein the first voltage dividing unit 31 includes voltage dividing resistors R31 and R32, the second voltage dividing unit 32 includes voltage dividing resistors R33 and R34, the third voltage dividing unit 33 includes voltage dividing resistors R35 and R36, and the fourth voltage dividing unit includes voltage dividing resistors R35 and R36. The first voltage division unit 31, the second voltage division unit 32, the third voltage division unit 33, and the fourth voltage division unit 34 are used for performing voltage division processing on the accessed differential signals. It is understood that the operational amplifier amplifies only the differential mode signal, and the common mode signal can be further suppressed by each voltage dividing unit. The voltage dividing resistance of each voltage dividing unit can be adjusted according to the requirements of the rear-end decoding circuit. Corresponding to each voltage dividing unit, a dc blocking capacitor is disposed in the present embodiment and is respectively denoted as a first dc blocking capacitor C31, a second dc blocking capacitor C32, a third dc blocking capacitor C33, and a fourth dc blocking capacitor C34. The first DC blocking capacitor C31, the second DC blocking capacitor C32, the third DC blocking capacitor C33 and the fourth DC blocking capacitor C34 respectively isolate the medium-direct-current signals of the input differential signals, and the appropriate differential signals are obtained and sent to the post-stage processing.
The utility model discloses still provide an audio equipment, audio equipment includes decoding circuit and as above analog differential circuit. The detailed structure of the analog differential circuit can refer to the above embodiments, and is not described herein again; it can be understood that, because the utility model discloses used above-mentioned analog differential circuit among the audio equipment, consequently, the utility model discloses audio equipment's embodiment includes all technical scheme of the whole embodiments of above-mentioned analog differential circuit, and the technical effect who reaches is also identical, no longer gives unnecessary details here.
The decoding circuit is preferably implemented by using a decoding integrated chip, and the decoding integrated chip is used for decoding, analyzing and processing the accessed differential signals.
The above only be the preferred embodiment of the utility model discloses a not consequently restriction the utility model discloses a patent range, all are in the utility model discloses a conceive, utilize the equivalent structure transform of what the content was done in the description and the attached drawing, or direct/indirect application all is included in other relevant technical field the utility model discloses a patent protection within range.
Claims (10)
1. An analog differential circuit is applied to audio equipment, and is characterized in that the analog differential circuit comprises a Butterworth filter circuit, a low-pass filter circuit and a differential signal output circuit, wherein the input end of the Butterworth filter circuit is used for accessing an audio signal, and the output end of the Butterworth filter circuit is respectively connected with the first input end of the differential signal output circuit and the input end of the low-pass filter circuit; the output end of the low-pass filter circuit is connected with the second input end of the differential signal output circuit; the first output end and the second output end of the differential signal output circuit are respectively connected with a decoding circuit of the audio equipment; wherein,
the Butterworth filter circuit is used for converting the accessed audio signal into a negative differential signal and outputting the negative differential signal;
the low-pass filter circuit is used for carrying out phase inversion and filtering processing on the negative differential signal output by the Butterworth filter circuit to obtain a positive differential signal and outputting the positive differential signal;
and the differential signal output circuit is used for performing voltage division filtering processing on the negative differential signal and the positive differential signal and outputting the processed signals to a decoding circuit of the audio equipment.
2. The analog differential circuit of claim 1, wherein the butterworth filter circuit comprises:
the first Butterworth filtering unit is used for converting a left channel audio signal accessed into the audio signal into a left channel negative differential signal and outputting the left channel negative differential signal;
and the second Butterworth filtering unit is used for converting the right channel audio signal accessed into the audio signal into a right channel negative differential signal and outputting the right channel negative differential signal.
3. The analog differential circuit according to claim 2, wherein the first butterworth filter cell includes a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, a third resistor, and a first operational amplifier, a first end of the first capacitor being an input terminal of the first butterworth filter cell, a second end of the first capacitor being interconnected with a first end of the second resistor, a first end of the third resistor, and a first end of the second capacitor via the first resistor, a second end of the second resistor being interconnected with an inverting input terminal of the first operational amplifier and a first end of the third capacitor; an output terminal of the first operational amplifier is an output terminal of the first butterworth filter unit and is interconnected with a second terminal of the third resistor and a second terminal of the third capacitor; the positive phase input end of the first operational amplifier is connected with a first direct current power supply; and the second end of the second capacitor is grounded.
4. The analog differential circuit according to claim 2, wherein the second butterworth filter unit includes a fourth capacitor, a fifth capacitor, a sixth capacitor, a fourth resistor, a fifth resistor, a sixth resistor, and a second operational amplifier, a first end of the fourth capacitor being an input terminal of the second butterworth filter unit, a second end of the fourth capacitor being interconnected with a first end of the fifth resistor, a first end of the sixth resistor, and a first end of the fifth capacitor via the fourth resistor, a second end of the fifth resistor being interconnected with an inverting input terminal of the second operational amplifier and a first end of the sixth capacitor; an output terminal of the second operational amplifier is an output terminal of the second butterworth filtering unit and is interconnected with a second terminal of the sixth resistor and a second terminal of the sixth capacitor; the positive phase input end of the second operational amplifier is connected with a second direct current power supply; and the second end of the fifth capacitor is grounded.
5. The analog differential circuit of claim 2, wherein the low pass filter circuit comprises:
the first low-pass filtering unit is used for converting the left channel negative differential signal output by the first Butterworth filtering unit into a left channel positive differential signal and outputting the left channel positive differential signal;
and the second low-pass filtering unit is used for converting the right channel negative differential signal output by the second Butterworth filtering unit into a right channel positive differential signal and outputting the right channel positive differential signal.
6. The analog differential circuit according to claim 5, wherein the first low-pass filtering unit includes a seventh capacitor, a seventh resistor, an eighth resistor, and a third operational amplifier, a first end of the seventh resistor is an input terminal of the first low-pass filtering unit, and a second end of the seventh resistor is interconnected with an inverting input terminal of the third operational amplifier, a first end of the eighth resistor, and a first end of the seventh capacitor; an output end of the third operational amplifier is an output end of the first low-pass filtering unit, and is interconnected with a second end of the eighth resistor and a second end of the seventh capacitor; and the positive phase input end of the third operational amplifier is connected with a first direct current power supply.
7. The analog differential circuit according to claim 5, wherein the second low-pass filtering unit includes an eighth capacitor, a ninth resistor, a tenth resistor, and a fourth operational amplifier, a first terminal of the ninth resistor being an input terminal of the second low-pass filtering unit, a second terminal of the ninth resistor being interconnected with an inverting input terminal of the fourth operational amplifier, a first terminal of the tenth resistor, and a first terminal of the eighth capacitor; an output end of the fourth operational amplifier is an output end of the second low-pass filtering unit, and is interconnected with a second end of the tenth resistor and a second end of the eighth capacitor; and the positive phase input end of the fourth operational amplifier is connected with a second direct current power supply.
8. The analog differential circuit according to any one of claims 1 to 7, wherein the differential signal output circuit includes a plurality of voltage dividing units and blocking capacitors disposed corresponding to the voltage dividing units, input terminals of the voltage dividing units are respectively connected to output terminals of the low-pass filter circuit in a one-to-one correspondence, output terminals of the voltage dividing units are respectively connected to first ends of the blocking capacitors in a one-to-one correspondence, and second ends of the blocking capacitors are respectively connected to input terminals of the decoding circuit in a one-to-one correspondence.
9. Audio device, characterized in that it comprises a decoding circuit and an analog difference circuit according to any one of claims 1 to 8.
10. The audio device of claim 9, wherein the decoding circuit comprises a decoding integrated chip.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721263155.XU CN207266266U (en) | 2017-09-27 | 2017-09-27 | Analog differential circuit and audio frequency apparatus |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201721263155.XU CN207266266U (en) | 2017-09-27 | 2017-09-27 | Analog differential circuit and audio frequency apparatus |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110225425A (en) * | 2019-07-09 | 2019-09-10 | 深圳市中科蓝讯科技有限公司 | A kind of microphone input circuit |
| CN111200775A (en) * | 2018-11-19 | 2020-05-26 | 广州汽车集团股份有限公司 | Audio interface circuit, circuit group, automobile and audio access method |
| CN114362757A (en) * | 2021-12-16 | 2022-04-15 | 深圳万正芯源有限公司 | DAC post-filtering system based on Butterworth filter |
-
2017
- 2017-09-27 CN CN201721263155.XU patent/CN207266266U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111200775A (en) * | 2018-11-19 | 2020-05-26 | 广州汽车集团股份有限公司 | Audio interface circuit, circuit group, automobile and audio access method |
| CN111200775B (en) * | 2018-11-19 | 2021-03-05 | 广州汽车集团股份有限公司 | Audio interface circuit, circuit group, automobile and audio access method |
| CN110225425A (en) * | 2019-07-09 | 2019-09-10 | 深圳市中科蓝讯科技有限公司 | A kind of microphone input circuit |
| CN114362757A (en) * | 2021-12-16 | 2022-04-15 | 深圳万正芯源有限公司 | DAC post-filtering system based on Butterworth filter |
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