Interference suppression circuit and audio receiving processor

Abstract

The utility model discloses an interference suppression circuit and an audio receiving processor, the circuit comprises an audio socket, a capacitor filter circuit, a magnetic bead, a pseudo-differential circuit, an n-shaped filter circuit, a blocking circuit, an operational amplifier circuit, a DSP and a switching circuit which are connected in sequence, and the switching circuit comprises a switch, a first resistor and a second resistor. One end of the switch is connected with an AGND signal output by the audio circuit, the other end of the switch is connected with the first pin or the second pin in a switching mode, the first pin is grounded after being connected with the first resistor, the second pin is grounded after being connected with the second resistor, the first resistor is larger than the second resistor, and when ground loop interference noise exists, the first pin of the switch is controlled to be switched on, and the second pin of the switch is controlled to be switched off. At the moment, the switching circuit realizes single-point connection through the first resistor, and the pseudo-differential circuit is accessed after the first resistor is introduced, so that an audio analog signal can flow back to an input source through the ground on a signal line, and the problem of loop-to-ground current noise caused by a ground loop is effectively solved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to an interference suppression circuit and an audio receiving processor. Background Art

[0002] As an integrator of audio and video technology, sound quality has always been an important evaluation point for recording and broadcasting. Since the recording and broadcasting host is located at the center of the interconnection of various devices, it has external devices such as all-in-one machine, microphone, audio processor, speaker, etc., and the recording and broadcasting host will be connected to many external devices through HDMI (High Definition Multimedia Interface) interface cables, USB cables, audio cables, network cables and other signal cables. Some of these external devices are powered by adapters, while others are powered by AC.

[0003] For devices powered by AC alternating current, the noise and harmonic energy it contains runs through the audio frequency range, including high-frequency energy, such as harsh buzzing sounds, which will produce AC-DC common-mode or differential-mode conducted interference; electromagnetic induction interference generated by alternating current such as transformers. Moreover, in the overall deployment environment, if the analog audio line is not properly isolated from the AC power line, electromagnetic interference such as space and stray electromagnetic waves will be coupled to the audio signal line through the analog audio line, and there will be a large background noise problem when the recording and broadcasting host collects the audio. Figure 1 FIG. 1 is a schematic diagram showing an analog audio signal affected by strong electrical interference.

[0004] In addition, in the interconnected system, there will be a ground loop problem between the audio device and the recording and broadcasting host large-screen all-in-one machine, speakers and other devices. For example, the recording and broadcasting host is located in the center, the audio source device outputs analog audio, and the audio receiving processor in the recording and broadcasting host collects the transmitted analog signal and then transmits this signal to the speaker. Among them, the audio source device and the audio receiving processor are two different devices. The inconsistent impedance of the two devices to the ground leads to a potential difference between the two devices, which in turn causes the audio receiving processor to introduce noise interference when collecting non-audio signals. Utility Model Content

[0005] In view of this, the utility model provides an interference suppression circuit and an audio receiving processor to solve the interference caused by the spatial electromagnetic radiation between the sound source device and the audio receiving processor coupled into the audio line, and the current noise interference problem caused by the potential difference between devices due to the ring ground when multiple devices are interconnected.

[0006] In a first aspect, the utility model provides an interference suppression circuit, the circuit comprising: an audio circuit, a magnetic bead, a pseudo differential circuit, a Π-type filter circuit, a DC isolation circuit, an operational amplifier circuit and a digital signal processor DSP connected in sequence, wherein the circuit further comprises a switch circuit;

[0007] Wherein, the audio circuit comprises a ground terminal and an audio signal output terminal, the ground terminal is used to output an analog ground AGND signal, and the audio signal output terminal is used to output an analog audio signal to the magnetic bead;

[0008] The switch circuit comprises a switch, a first resistor and a second resistor, wherein one end of the switch is connected to the analog ground AGND signal output by the audio circuit, and the other end of the switch is switchably connected to the first pin or the second pin, the first pin is connected to the first resistor and then to the ground, the second pin is connected to the second resistor and then to the ground, and the first resistor is greater than the second resistor;

[0009] The magnetic bead is connected to the audio signal output end, and is used to receive an analog audio signal, suppress electromagnetic interference on the analog audio signal, and transmit the suppressed analog audio signal to the pseudo differential circuit;

[0010] The pseudo differential circuit is connected to the magnetic bead and the audio signal output end, and is used to convert the suppressed analog audio signal from one analog audio signal to a pseudo differential signal with two outputs, and transmit the pseudo differential signal with two outputs to the Π-type filter circuit and the DC isolation circuit;

[0011] The Π-type filter circuit and the DC isolation circuit are used to filter and isolate the pseudo differential signals outputted from the dual-path of the pseudo differential circuit in sequence, and output the dual-path AC signals after the DC isolation to the operational amplifier circuit;

[0012] The operational amplifier circuit includes an operational amplifier, two input terminals of the operational amplifier are used to receive the two AC signals after the DC isolation process, and an output terminal is used to output the amplified signal to the DSP.

[0013] In an optional implementation, the circuit further includes a capacitor filter circuit, which is connected between a ground terminal and an audio signal output terminal of the audio circuit and is used to receive and filter the analog audio signal.

[0014] In another optional implementation, the number of the ground terminal and the audio signal output terminal of the audio circuit is two; the number of the magnetic beads, the pseudo-differential circuit, the Π-type filter circuit, the DC isolation circuit, and the operational amplifier circuit are all two;

[0015] The ground terminal of the audio circuit includes a first ground terminal and a second ground terminal; and is used to output two analog ground AGND signals to the switch circuit;

[0016] The audio signal output end includes a first audio signal output end and a second audio signal output end, which are used to output two analog audio signals of a left channel and a right channel to two magnetic beads; and the two analog audio signals are processed by two magnetic beads, two pseudo-differential circuits, two Π-type filter circuits, two DC isolation circuits and two operational amplifier circuits in sequence, and then the two operational amplifier circuits output two amplified signals to the DSP.

[0017] In another optional implementation, the number of the capacitor filter circuits is two, each capacitor filter circuit includes three capacitors, and the connection relationship of the three capacitors is: the first capacitor and the second capacitor are connected in parallel and then connected in series with the third capacitor.

[0018] In yet another optional implementation, the circuit further includes an electrostatic impedance device, which is connected to the audio signal output terminal and is used to release electrostatic current and protect the circuit from high voltage breakdown.

[0019] In yet another optional implementation, the resistance value of the first resistor is 5.1Ω, and the resistance value of the second resistor is 0.

[0020] In another optional embodiment, the DC isolation circuit includes two capacitors and two resistors, one end of each capacitor is connected to a resistor, the other end of each capacitor is connected to an output end of the Π-type filter circuit, and the other end of each resistor is connected to the input end of the operational amplifier circuit.

[0021] In another optional implementation, the operational amplifier circuit further includes a first RC filter circuit and a second RC filter circuit; the first RC filter circuit is connected to the negative feedback circuit of the operational amplifier; and the second RC filter circuit is connected to the non-inverting input terminal of the operational amplifier.

[0022] In yet another optional implementation, the DSP includes an analog-to-digital converter ADC.

[0023] In a second aspect, the utility model further provides an audio receiving processor, comprising the interference suppression circuit as described in the first aspect or any implementation of the first aspect.

[0024] The interference suppression circuit provided by the utility model is provided with a switch circuit, and the switch switches the circuit through the first pin and the second pin. When there is ground loop interference noise between two interconnected devices, the first pin of the switch is controlled to be connected, and at this time, a single-point connection is realized between the analog ground and the digital ground through the first resistor, and the first resistor is a noise suppression resistor. When there is current sound noise interference caused by the ring ground, the dip switch is turned to the first pin, and a single-point connection is made with the device ground through the first resistor. The first resistor is equivalent to adding an impedance between the shielding layers of the audio transmission cable, which will reduce the noise potential difference between the audio cable grounds. After the suppression impedance is introduced, the pseudo-differential circuit is connected to eliminate the potential difference of the ground, and the first resistor also plays a shunt role for the dry noise current signal, thereby effectively solving the audio current public frequency interference problem caused by the ground loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of an analog audio signal affected by strong electrical interference provided by the utility model;

[0027] Figure 2 This is a scene schematic diagram of an interconnected system provided by the utility model;

[0028] Figure 3 It is a circuit diagram of an interference suppression circuit provided by an embodiment of the utility model;

[0029] Figure 4 It is a circuit diagram of another interference suppression circuit provided by an embodiment of the utility model;

[0030] Figure 5 It is a circuit diagram of another interference suppression circuit provided by an embodiment of the utility model;

[0031] Figure 6 It is a schematic diagram of an audio device provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0033] Among them, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.

[0034] See also Figure 2 As shown, the application scenario of the utility model can be applied, and the application scenario can be an interconnected system including multiple devices. In an interconnected system, it specifically includes: a recording and broadcasting host 1, a large-screen all-in-one machine 2, a socket 3, a router 4, other audio processors 5 and a speaker 6, etc. Figure 2 In the figure, the recording and broadcasting host 1 includes an audio receiving processor, and signal connections are made between various devices, such as solid lines representing earth connection and dotted lines representing signal line ground connection. Some of these peripherals are powered by adapters, and some are powered by AC. For AC powered devices, the noise and harmonic energy they contain may run through the frequency range of the audio.

[0035] Refer to the above Figure 1 , the recording and broadcasting host 1 is used as an audio receiving processor, and the large-screen all-in-one machine 2 is used as an analog audio source device. The audio receiving processor is used to collect analog signals through the transmission line, and then transmit the signal to the speaker 6 through the router 4. Since the recording and broadcasting host 1 and the large-screen all-in-one machine 2 have different impedances to the ground, there is a potential difference between the two devices. When the audio receiving processor collects non-audio signals, electromagnetic interference will be introduced.

[0036] In addition, if the analog audio cable and the AC power line are not isolated in the whole machine deployment environment, electromagnetic interference such as space and stray electromagnetic waves will be coupled to the audio signal line through the analog audio cable, and there will be a large background noise when the recording and broadcasting host collects the audio.

[0037] In order to solve the above problems, this embodiment provides an interference suppression circuit and an audio device. The interference suppression circuit and the audio device provided by the utility model are introduced in detail below.

[0038] See also Figure 3 , an interference suppression circuit is provided for this embodiment, the circuit includes: an audio circuit, a magnetic bead LM, a pseudo-differential circuit, a Π-type filter circuit, a DC isolation circuit, an operational amplifier circuit and a DSP (Digital Signal Processor) connected in sequence, and the circuit also includes a switching circuit.

[0039] Among them, the audio circuit includes a ground terminal and an audio signal output terminal, the ground terminal is used to output an analog ground AGND signal, and the switch circuit is connected to the analog ground AGND signal; the audio signal output terminal is connected to the magnetic bead LM, and is used to output an analog audio signal to the magnetic bead LM.

[0040] The magnetic bead LM is used to suppress electromagnetic interference on the analog audio signal output from the audio circuit, and transmit the suppressed analog audio signal to the pseudo differential circuit;

[0041] The pseudo differential circuit is connected to the magnetic bead LM and the analog ground AGND signal output by the audio circuit, and is used to convert the suppressed analog audio signal from one analog audio signal to a pseudo differential signal with two outputs, and transmit the pseudo differential signal with two outputs to the Π-type filter circuit and the DC isolation circuit.

[0042] The Π-type filter circuit and the DC isolation circuit are used to filter and isolate the pseudo differential signals from the dual outputs of the pseudo differential circuit in turn, and output the two AC signals after the DC isolation to the operational amplifier circuit.

[0043] The operational amplifier circuit includes an operational amplifier, which includes a non-inverting input terminal, an inverting input terminal and an output terminal, wherein the non-inverting input terminal and the inverting input terminal are used to receive two AC signals output after the DC isolation circuit is isolated, and the output terminal of the operational amplifier is used to output the amplified signal to the DSP.

[0044] The switch circuit includes a switch, a first resistor and a second resistor, wherein one end of the switch is connected to the analog ground AGND signal, and the other end of the switch is switched to connect to the first pin or the second pin, the first pin is connected to the first resistor and then to the ground, the third pin is connected to the second resistor and then to the ground, and the first resistor is greater than the second resistor. Figure 3 As shown, the first pin 1 is connected to the first resistor, the third pin 3 is connected to the second resistor, and both the first resistor and the second resistor are grounded.

[0045] When the second pin 2 of the switch is connected to the first pin 1, the first pin 1 is connected to the ground at a single point through the first resistor; when the second pin 2 is connected to the third pin 3, the second pin 2 is connected to the ground at a single point through the second resistor.

[0046] When there is no electromagnetic interference caused by a ground loop between two interconnected devices, the second pin 2 and the third pin 3 of the switch are connected; when there is ground loop noise caused by a common ground between the two interconnected devices, the third pin 3 of the switch is switched to the first pin 1, so that the second pin 2 is connected to the first pin 1. At this time, the analog ground AGND and the digital ground GND are connected at a single point through a first resistor (for example, the first resistor is 5.1 ohms). The 5.1 ohm first resistor is a noise suppression resistor. When there is current sound noise interference caused by a ground loop, the dip switch is turned to the first pin, the 5.1 ohm first resistor is connected, and a single point connection is made with the device ground through 5.1 ohms. The first resistor is equivalent to adding an impedance between the shielding layers of the audio transmission cable, which will reduce the noise potential difference between the audio cable grounds. After the 5.1 ohm impedance is introduced, the pseudo-differential circuit is connected to eliminate the ground potential difference. In addition, the 5.1 ohm first resistor also plays a shunt role for the dry noise current signal, thereby effectively solving the audio current common frequency interference problem caused by the ground loop.

[0047] Optionally, the audio circuit is a 3.5mm stereo audio socket.

[0048] Optionally, the resistance value of the first resistor is 5.1Ω, and the resistance value of the second resistor is 0.

[0049] In addition, optionally, the above-mentioned DSP may be an analog-to-digital converter ADC, or a DSP including an ADC.

[0050] In some embodiments, the above circuit further includes a capacitor filter circuit, which is connected between the ground terminal and the audio signal output terminal of the audio circuit and is used to receive and filter the analog audio signal.

[0051] In other embodiments, the number of the ground terminal and the audio signal output terminal of the audio circuit is two; and the number of the magnetic beads, the pseudo-differential circuit, the Π-type filter circuit, the DC isolation circuit, and the operational amplifier are all two, such as Figure 4 shown.

[0052] Wherein, the ground terminal of the audio circuit includes a first ground terminal and a second ground terminal, which are used to output two analog ground AGND signals to the switch circuit;

[0053] The audio signal output end includes a first audio signal output end and a second audio signal output end, which are used to output two analog audio signals of a left channel and a right channel to two magnetic beads; and the two analog audio signals are processed by two magnetic beads, two pseudo-differential circuits, two Π-type filter circuits, two DC isolation circuits and two operational amplifier circuits in sequence, and then processed by two operational amplifiers to output two amplified signals to the DSP.

[0054] Furthermore, there are two capacitor filter circuits, each of which includes three capacitors. The connection relationship between the three capacitors is as follows: the first capacitor and the second capacitor are connected in parallel and then connected in series with the third capacitor.

[0055] This embodiment provides an interference suppression circuit according to the above Figure 3 The structure shown also provides a complete interference suppression circuit, such as Figure 4 and Figure 5 As shown. Figure 4 For the complete circuit structure, Figure 5 For Figure 4 The circuit is divided into circuit modules based on the circuit.

[0056] like Figure 5 As shown, the audio circuit CN1 outputs two analog audio signals and two analog ground AGND signals. The audio circuit CN1 includes 1 to 6 pins, wherein pin 1 and pin 2 are ground pins, pin 3 and pin 4 input right channel EP_R and left channel analog audio signals EP_R respectively, and pin 5 and pin 6 are input sources DET 6 (LINE DET).

[0057] In addition, the interference suppression circuit also includes: a switch circuit, a capacitor filter circuit, a magnetic bead LM, a pseudo differential circuit, a Π-type filter circuit, a DC isolation circuit, an operational amplifier circuit and a DSP. Since the audio circuit outputs two analog audio signals of the left channel and the right channel, the number of magnetic beads LM, pseudo differential circuit, Π-type filter circuit, DC isolation circuit and operational amplifier circuit required by the back-end circuit is two.

[0058] like Figures 4 to 5 As shown, the right channel analog audio signal EP_R output by the audio circuit passes through the magnetic bead LM1, the first pseudo-differential circuit (including resistor RA3), the first Π-type filter circuit (including resistor RA6 and capacitor CA5), and the first DC isolation circuit (including capacitor CA2 and resistor RA4) in sequence, and is input to the reverse input terminal RINN of the first operational amplifier of the operational amplifier circuit.

[0059] The analog ground AGND signal 1 output by the audio circuit passes through the first pseudo-differential circuit (including resistor RA8), the first Π-type filter circuit (including resistor RA6 and capacitor CA5), and the first DC isolation circuit (including capacitor CA4 and resistor RA5) in sequence, and is input to the non-inverting input terminal RINP of the first operational amplifier.

[0060] The first operational amplifier amplifies the two input signals and outputs the amplified signals to the DSP through the output terminal ROUT.

[0061] The first capacitor filter circuit includes capacitors CA16, CA17 and CA19, wherein capacitors CA16 and CA17 are connected in parallel and then in series with capacitor CA19. In addition, capacitor CA16 is also connected to the right channel analog audio signal EP_R, and capacitor CA17 is also connected to the ground pin 1 of the audio circuit.

[0062] Similarly, the left channel analog audio signal EP_L output by the audio circuit passes through the magnetic bead LM2, the second pseudo-differential circuit (including resistor RA16), the second Π-type filter circuit (including resistor RA14 and capacitor CA9), and the second DC isolation circuit (including capacitor CA8 and resistor RA13) in sequence, and is input to the reverse input terminal LINN of the second operational amplifier.

[0063] The analog ground AGND signal 2 output by the audio circuit passes through the second pseudo-differential circuit (including resistor RA10), the second Π-type filter circuit (including resistor RA14 and capacitor CA9), and the second DC isolation circuit (including capacitor CA7 and resistor RA11) in sequence, and is input to the non-inverting input terminal LINP of the second operational amplifier.

[0064] The second operational amplifier amplifies the two input signals and outputs them to the DSP through the output terminal LOUT.

[0065] The second capacitor filter circuit includes capacitors CA14, CA15 and CA20, wherein capacitors CA14 and CA15 are connected in parallel and then connected in series with capacitor CA20. In addition, capacitor CA15 is also connected to the left channel analog audio signal EP_L, and capacitor CA14 is also connected to the ground pin 2 of the audio circuit.

[0066] In addition, the circuit provided in this embodiment also includes an electrostatic impedance device, which is connected to the audio signal output terminal and is used to protect sensitive circuits from electrostatic discharge (ESD). Specifically, the electrostatic impedance device is used to release electrostatic current and protect subsequent circuits.

[0067] Optionally, the electrostatic impedance device is an ESD device. Generally, ESD devices mainly include diodes, resistors, P / NMOS tubes, BJTs, SCRs, etc., because they have characteristics such as avalanche breakdown, avalanche and injection, and can instantly enter a low-resistance state, they have good current discharge capabilities and can be used as ESD devices.

[0068] Optionally, the audio circuit is a 3.5mm stereo audio socket CN1. Specifically, the audio socket CN1 represents a connection port on the circuit board, which is used to connect other audio devices or components. In this embodiment, it can be used to connect analog audio source devices, such as the large-screen all-in-one machine 2.

[0069] like Figures 4 to 5 As shown, when the analog audio signal is input through the 3.5mm stereo audio jack, the left and right channel analog audio signals near the jack are connected to the electrostatic impedance device, and the other end of the electrostatic impedance device is grounded. In this embodiment, two electrostatic impedance devices are set, namely DA1 and DA2. Among them, DA1 is connected to the left channel analog audio signal EP_L to release the electrostatic current on the left channel analog audio signal EP_L, and DA2 is connected to the electrostatic current on the right channel analog audio signal EP_R.

[0070] The magnetic beads LM1 and LM2 are used to suppress electromagnetic interference on the right channel and the left channel analog audio signals respectively, and transmit the suppressed right channel and the left channel analog audio signals to the first pseudo differential circuit and the second pseudo differential circuit.

[0071] The first pseudo differential circuit is used to convert the suppressed right channel analog audio signal EP_R from a one-way analog audio signal to a dual-way output analog audio signal, and output the dual-way to the first Π-type filter circuit and the first DC isolation circuit.

[0072] The second pseudo differential circuit is used to convert the suppressed left channel analog audio signal EP_L from a one-way analog audio signal to a dual-way output analog audio signal, and output the dual-way to the second Π-type filter circuit and the second DC isolation circuit.

[0073] The first Π-type filter circuit and the first DC isolation circuit are used to filter and isolate the pseudo differential signals from the dual-channel output of the pseudo differential circuit in turn, and output the dual-channel AC signals after the DC isolation processing to the first operational amplifier.

[0074] The in-phase input terminal RINP of the first amplifier receives an AC audio signal outputted from RA5 of the first DC blocking circuit; the inverting input terminal RINN of the first amplifier receives another AC audio signal outputted from RA4 of the first DC blocking circuit.

[0075] In addition, the operational amplifier circuit also includes a first RC filter circuit and a second RC filter circuit. The first RC filter circuit is connected to the negative feedback circuit of the first operational amplifier; the second RC filter circuit is connected to the non-inverting input terminal of the first operational amplifier. Figure 4 and Figure 5 As shown, the first RC filter circuit is composed of a capacitor CA1 and a resistor RA1 connected in parallel, connected between the output terminal ROUT and the non-inverting input terminal RINP of the first operational amplifier, and is used to filter the signal on the negative feedback circuit. The second RC filter circuit is composed of a capacitor CA6 and a resistor RA7 connected in parallel, connected to the non-inverting input terminal RINP of the first operational amplifier, and is used to filter the non-inverting input analog signal.

[0076] In addition, the operational amplifier circuit further includes resistors RA9 and RA12, wherein the resistor RA9 is connected in series between the first operational amplifier output terminal ROUT and DSP.

[0077] Similarly, the second Π-type filter circuit and the second DC isolation circuit are used to filter and isolate the pseudo differential signals from the dual outputs of the pseudo differential circuit in turn, and output the dual AC signals after DC isolation to the second operational amplifier.

[0078] The in-phase input terminal LINP of the second amplifier receives an AC audio signal output from RA11 of the second DC blocking circuit; the inverting input terminal LINN of the first amplifier receives another AC audio signal output from RA13 of the second DC blocking circuit.

[0079] In addition, the operational amplifier circuit also includes a first RC filter circuit and a second RC filter circuit. The first RC filter circuit is connected to the negative feedback circuit of the second operational amplifier; the second RC filter circuit is connected to the non-inverting input terminal of the second operational amplifier. Figure 4 and Figure 5 As shown, the first RC filter circuit is composed of a capacitor CA3 and a resistor RA2 connected in parallel, connected between the output terminal LOUT and the non-inverting input terminal LINP of the second operational amplifier, and is used to filter the signal on the negative feedback circuit. The second RC filter circuit is composed of a capacitor CA10 and a resistor RA15 connected in parallel, connected to the non-inverting input terminal LINP of the second operational amplifier, and is used to filter the non-inverting input analog signal.

[0080] In addition, the resistor RA12 in the operational amplifier circuit is connected in series between the second operational amplifier output terminal LOUT and DSP.

[0081] Optionally, the model of the operational amplifier circuit is AD22653B. The operational amplifier circuit of this model also includes an SDN terminal, which is connected to an AU_3V voltage through a resistor RA17. The operational amplifier circuit also includes a ground terminal (such as GND and PGND) and a power supply terminal VSS.

[0082] In addition, the above circuit also includes a switch circuit, which includes a switch S1, wherein the switch S1 includes a first pin 1, a second pin 2, and a third pin 3. In this embodiment, the first pin 1 is connected to the first resistor RA19, the third pin 3 is connected to the second resistor RA18, and the second pin 2 is connected to the analog ground AGND signal output by the output end of the audio circuit. And the resistance of the first resistor RA19 is greater than that of the second resistor RA18.

[0083] Optionally, the resistance of RA19 is 5.1 ohms and the resistance of RA18 is 0 ohms.

[0084] When there is no signal interference caused by a ground loop between two interconnected devices, the second pin 2 and the third pin 3 of the switch S1 are connected. At this time, the analog ground and the digital ground in the pseudo-differential circuit are connected at a single point through a resistor; when there is a common ground between the two interconnected devices and ground loop interference noise is generated, the second pin 2 of the switch S1 is controlled to be connected to the first pin 1. At this time, the analog ground and the digital ground are connected at a single point through a 5.1 ohm RA19 resistor. Due to the introduction of the 5.1 ohm resistor impedance and the pseudo-differential circuit, the analog signal input to 3.5 mm can flow back to the input source through the ground on the signal line, thereby effectively solving the analog signal interference caused by the ground loop.

[0085] In addition, this circuit also realizes the conversion of analog audio input signals into pseudo differential signals after input, ensuring that the signals received by the receiving end are not subject to electromagnetic interference, and effectively solving the problem of audio signal distortion caused by the frequency response generated by the potential difference in the ring ground.

[0086] In addition, the circuit provided in this embodiment can ensure that the audio frequency response signal meets the frequency response range of 20 Hz to 20 KHz.

[0087] The interference suppression circuit provided by this embodiment has the following beneficial effects:

[0088] First, the magnetic beads in this circuit can effectively filter out the electromagnetic interference in the audio signal.

[0089] Second, this circuit converts a single-ended input audio signal into a dual-channel pseudo-differential signal by setting a pseudo-differential circuit, and then transmits the dual-channel pseudo-differential signal to a Π-type filter circuit, a DC isolation circuit, and an operational amplifier circuit for processing, and finally outputs it to a back-end DSP chip. Since the Π-type filter circuit, the DC isolation circuit, and the operational amplifier circuit have the functions of reducing noise and amplifying signals for the input pseudo-differential signal (the source comes from the analog audio signal), the analog audio signal output by the Π-type filter circuit, the DC isolation circuit, and the operational amplifier circuit improves the signal-to-noise ratio of the analog audio signal compared to the analog audio signal at the source, where the signal-to-noise ratio SNR (Signal-to-noise Ratio) is the ratio of the signal to the noise.

[0090] Third, this circuit connects a switch circuit to the analog ground AGND signal output by the audio circuit. The switch circuit contains two resistors that are grounded at a single point, and one resistor is larger than the other resistor. The switch circuit has a simple structure and can solve the problem of ring ground noise interference without other circuit elements, and the cost is low.

[0091] In addition, an audio receiving processor such as Figure 6 As shown, including the above Figures 3 to 5 The interference suppression circuit shown. Optionally, the interference suppression circuit can be arranged in the audio receiving processor.

[0092] Furthermore, the audio receiving processor may be integrated in Figure 2 As shown in the recording and broadcasting host 1.

[0093] Of course, the interference suppression circuit of the present invention can also be applied to other audio devices, and can also improve the noise interference suppression effect of the audio devices.

[0094] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An interference suppression circuit, characterized in that: The circuit comprises: an audio circuit, a magnetic bead, a pseudo differential circuit, a Π-type filter circuit, a DC isolation circuit, an operational amplifier circuit and a digital signal processor DSP connected in sequence, wherein the circuit also comprises a switch circuit; Wherein, the audio circuit comprises a ground terminal and an audio signal output terminal, the ground terminal is used to output an analog ground AGND signal, and the audio signal output terminal is used to output an analog audio signal to the magnetic bead; The switch circuit comprises a switch, a first resistor and a second resistor, wherein one end of the switch is connected to the analog ground AGND signal output by the audio circuit, and the other end of the switch is switchably connected to the first pin or the second pin, the first pin is connected to the first resistor and then to the ground, the second pin is connected to the second resistor and then to the ground, and the first resistor is greater than the second resistor; The magnetic bead is connected to the audio signal output end, and is used to receive an analog audio signal, suppress electromagnetic interference on the analog audio signal, and transmit the suppressed analog audio signal to the pseudo differential circuit; The pseudo differential circuit is connected to the magnetic bead and the audio signal output end, and is used to convert the suppressed analog audio signal from one analog audio signal to a pseudo differential signal with two outputs, and transmit the pseudo differential signal with two outputs to the Π-type filter circuit and the DC isolation circuit; The Π-type filter circuit and the DC isolation circuit are used to filter and isolate the pseudo differential signals outputted from the dual-path of the pseudo differential circuit in sequence, and output the dual-path AC signals after the DC isolation to the operational amplifier circuit; The operational amplifier circuit includes an operational amplifier, two input terminals of the operational amplifier are used to receive the two AC signals after the DC isolation process, and an output terminal is used to output the amplified signal to the DSP.

2. The interference suppression circuit according to claim 1, characterized in that: The circuit also includes a capacitor filter circuit, The capacitor filter circuit is connected between the ground terminal and the audio signal output terminal of the audio circuit, and is used for receiving and filtering the analog audio signal.

3. The interference suppression circuit according to claim 2, characterized in that: The number of the ground terminal and the audio signal output terminal of the audio circuit is two; the number of the magnetic beads, the pseudo-differential circuit, the Π-type filter circuit, the DC isolation circuit, and the operational amplifier circuit are all two; The ground terminal of the audio circuit includes a first ground terminal and a second ground terminal; and is used to output two analog ground AGND signals to the switch circuit; The audio signal output end includes a first audio signal output end and a second audio signal output end, which are used to output two analog audio signals of a left channel and a right channel to two magnetic beads; and the two analog audio signals are processed by two magnetic beads, two pseudo-differential circuits, two Π-type filter circuits, two DC isolation circuits and two operational amplifier circuits in sequence, and then the two operational amplifier circuits output two amplified signals to the DSP.

4. The interference suppression circuit according to claim 3, characterized in that: There are two capacitor filter circuits, each of which includes three capacitors. The connection relationship of the three capacitors is as follows: the first capacitor and the second capacitor are connected in parallel and then connected in series with the third capacitor.

5. The interference suppression circuit according to claim 1, characterized in that: The circuit further comprises an electrostatic impedance device, and the electrostatic impedance device is connected to the audio signal output terminal.

6. The interference suppression circuit according to claim 1, characterized in that: The resistance value of the first resistor is 5.1Ω, and the resistance value of the second resistor is 0.

7. The interference suppression circuit according to any one of claims 1 to 6, characterized in that: The DC isolation circuit includes two capacitors and two resistors, one end of each capacitor is connected to a resistor, the other end of each capacitor is connected to an output end of the Π-type filter circuit, and the other end of each resistor is connected to the input end of the operational amplifier circuit.

8. The interference suppression circuit according to any one of claims 1 to 6, characterized in that: The operational amplifier circuit also includes a first RC filter circuit and a second RC filter circuit; The first RC filter circuit is connected to the negative feedback circuit of the operational amplifier; The second RC filter circuit is connected to the non-inverting input terminal of the operational amplifier.

9. The interference suppression circuit according to any one of claims 1 to 6, characterized in that: The DSP includes an analog-to-digital converter ADC.

10. An audio receiving processor, characterized in that: The invention comprises the interference suppression circuit as claimed in any one of claims 1 to 9.

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