RU2771788C1 - Terminal device and audio playback circuit - Google Patents

Abstract

FIELD: acoustics.

SUBSTANCE: invention relates to acoustics, in particular, to headphones. The sound reproduction circuit contains two digital-to-analog converters, two stereo headset speakers, an interface and a headset plug, series-connected resistors are connected to the common point of the speakers, the output of the second of which is grounded. The circuit consists of the first and second current routes. The first route is made with the possibility of shunting the current output by the left channel circuit to adjust the voltage supplied to the first end of the right channel of the headset, the second voltage is equal to the voltage at the second end of the right channel of the headset. The second current flow route, made with the possibility of shunting the current output by the right channel circuit to adjust the first voltage supplied back to the first end of the left channel of the headset, when the right channel circuit outputs the audio signal of the right channel, where when the right channel circuit outputs the audio signal of the right channel and the left channel circuit does not output the audio signal of the left channel, the first voltage is equal to the voltage at the second end of the left channel of the headset.

EFFECT: improvement in the separation of signals between the left channel and the right channel.

12 cl, 10 dwg

Description

The technical field to which the invention belongs

The present disclosure relates to the field of communication technologies and, in particular, to a terminal device and an audio playback circuit.

State of the art

When the terminal device plays stereo sound, the left channel playback circuit and the right channel playback circuit play stereo sound independently. The left channel and right channel can play stereo sound at different times, or can play stereo sound at the same time. To ensure independent reproduction of stereo sound by the left channel and right channel, without affecting each other, it is necessary to solve the technical problem of separation; that is, the playback circuits of the two channels must be separated from each other to prevent the left and right channels from interfering with each other when playing the left and right channels.

Two headsets of two channels are usually connected to a common ground point. The common ground point must be connected to the ground of the audio source on the motherboard, but there is a wiring resistance, magnetic washer resistance, etc. between the common ground and the ground of the sound source on the motherboard. Therefore, when the channel playback circuit receives a signal from the processor whose absolute voltage is greater than that of the signal from the sound source ground on the motherboard, due to wiring resistance, magnetic disk resistance, and, for example, between the common ground point and the sound source ground on the motherboard fix the voltage difference. The voltage difference causes current to flow through the headset of the other channel, so that the sound is played on the other channel and the separation between the left and right channels is unsatisfactory.

Disclosure of the essence of the invention

The present disclosure for improving the separation between the left channel and the right channel proposes an audio playback circuit and a terminal device.

According to a first aspect, an embodiment of the present invention provides an audio playback circuit. The audio playback circuit includes a left channel circuit, a right channel circuit, a first feedback circuit, a second feedback circuit, a first current path, and a second current path, where: the output end of the left channel circuit is connected to the first end of the left channel of the headset, the input end of the first a feedback circuit is connected to a second end of the left channel of the headset, and an output end of the first feedback circuit is connected to an input end of the left channel circuit; the output end of the right channel circuit is connected to the first end of the right channel of the headset, the input end of the second feedback circuit is connected to the second end of the right channel of the headset, and the output end of the second feedback circuit is connected to the input end of the right channel circuit, where the second end of the left channel of the headset is connected to the second end of the right channel of the headset; the first end of the first current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first current path is connected to the input end of the second feedback circuit and the second end of the left channel of the headset; the first end of the second current path is connected to the output end of the right channel circuit and the first end of the right channel of the headset, and the second end of the second current path is connected to the input end of the first feedback circuit and the second end of the right channel of the headset; the left channel circuit is configured to output the left channel audio signal to a first end of the left channel of the headset; the right channel circuit is configured to output the right channel audio signal to a first end of the right channel of the headset; the first feedback circuit is configured to feed back the first voltage to the first end of the left channel of the headset through the left channel circuit when the right channel circuit outputs the right channel audio signal; the second feedback circuit is configured to feed back the second voltage to the first end of the right channel of the headset through the right channel circuit when the left channel circuit outputs the left channel audio signal; the first current path is configured to shunt the current output of the left channel circuit to adjust the second voltage supplied back to the first end of the right channel of the headset when the left channel circuit outputs the left channel audio signal, where when the left channel circuit outputs the left channel audio signal and the right channel circuit does not outputs the right channel audio signal, the second voltage is equal to the voltage at the second end of the right channel of the headset; and the second current path is configured to shunt the current output by the right channel circuit to adjust the first voltage fed back to the first end of the left channel of the headset when the right channel circuit outputs the right channel audio signal, where when the right channel circuit outputs the right channel audio signal and the left channel circuit does not output the left channel audio signal, the first voltage is equal to the voltage at the second end of the left channel of the headset.

According to the audio playback circuit, when the absolute value of the voltage of the signal received by the left channel playback circuit from the processor is greater than that of the signal received by the motherboard audio source ground, and when the voltage of the signal received by the right channel playback circuit from the processor is equal to the signal voltage from the audio source ground on the motherboard, the first path of the current fed back to the right channel signal input end of the headset is used to adjust the voltage, so that the voltages at both ends of the right channel of the headset are equal when the right channel playback circuit is in the non-playing state, thereby , reducing the effect of current on the right channel of the headset when the left channel playback circuit is playing audio. Similarly, when the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is greater than the signal from the audio source ground on the motherboard, the second current path is used to change the voltage fed back to the left channel signal input end of the headset, so that the voltages at both ends of the left channel of the headset are equal when the playback circuit of the left channel is in the non-playback state, thereby reducing the influence of the current on the left channel of the headset when the playback circuit of the right channel is playing. Obviously, it is possible to reduce crosstalk between the left channel and the right channel by using a current path, which will improve the separation between the left channel and the right channel.

Coupling refers to the transfer of power from one part of a circuit to another part of a circuit. The connection may be based on wiring, or may be based on an electronic component, or circuit connection.

The fact that the channel circuitry is outputting the channel's audio signal may mean that the absolute voltage value of the signal received by the channel circuitry from the processor is greater than the signal from the audio source ground on the motherboard. The fact that the channel circuit is not outputting the channel's audio signal may mean that the voltage of the signal received by the channel circuit from the processor is equal to the ground voltage of the audio source on the motherboard.

During a particular implementation, both the first feedback circuit and the second feedback circuit may be voltage feedback circuits.

In an exemplary implementation, the first current path includes a first resistance, where the first end of the first resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first resistance is connected to the input end of the second feedback circuit and the second end of the left channel of the headset ; and the second current path includes a second resistance, where the first end of the second resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset and the second end of the second resistance is connected to the input end of the first feedback circuit and the second end of the right channel of the headset.

In an exemplary implementation, the left channel circuit, the right channel circuit, the first feedback circuit, and the second feedback circuit are integrated into the audio chip; the first current path is connected to the output end of the left channel circuit and the input end of the second feedback circuit through the audio chip chip interface, the output end of the left channel circuit is connected to the first left channel end of the headset through the audio chip interface, and the input end of the first feedback circuit is connected to the second end of the left channel of the headset through the sound chip chip interface; and the second current path is connected to the output end of the right channel circuit and the input end of the first feedback circuit through the audio chip chip interface, the output end of the right channel circuit is connected to the first right channel end of the headset through the audio chip interface, and the input end of the second feedback circuit is connected with the second end of the right channel of the headset through the sound chip chip interface.

Obviously, crosstalk between the right channel playback circuit and the left channel playback circuit can be reduced by using the audio chip chip interface without changing the internal structure of the audio chip through the first current path and the second current path, so that the separation between the right channel playback circuit and the playback of the left channel.

In an exemplary implementation, the left channel circuit, the right channel circuit, the first feedback circuit, the second feedback circuit, the first current path, and the second current path are integrated into the audio chip; the output end of the left channel circuit is connected to the first left channel end of the headset via the audio chip chip interface, and the input end of the first feedback circuit is connected to the second left channel end of the headset via the audio chip chip interface; and the output end of the right channel circuit is connected to the first right channel end of the headset via the audio chip chip interface, and the input end of the second feedback circuit is connected to the second right channel end of the headset via the audio chip chip interface.

In an exemplary implementation, the output end of the left channel circuit is connected to the first left channel end of the headset via the headset interface, and the output end of the right channel circuit is connected to the first end of the right channel of the headset via the headset interface, where the equivalent resistance generated between the headset interface and the stereo headset is the first equivalent impedance Px and stereo headset includes the left channel of the headset and the right channel of the headset; the input end of the first feedback circuit is connected to the second end of the left channel of the headset via the headset interface, and the input end of the second feedback circuit is connected to the second end of the right channel of the headset via the headset interface, where the equivalent resistance generated between the headset interface and the feedback circuit is the second equivalent resistance Ry, and the feedback circuit includes a first feedback circuit and a second feedback circuit; and the sound source ground is connected to the second end of the left channel of the headset and the second end of the right channel of the headset through the headset interface, where the equivalent resistance generated by the headset interface connected to the sound source ground is the third equivalent resistance Re, and the sound source ground voltage is the reference voltage, when the left or right channel circuit is not outputting audio signal.

The sound source ground is the sound source ground on the motherboard. The audio source ground on the motherboard refers to the audio reference voltage, where the reference voltage can come from the processor on the motherboard. A chip and a device may be provided on the motherboard. The chip may include, for example, a sound chip; and the device may include, for example, a device forming a current path.

In a possible implementation, the value of the first resistance is as follows:

where Rrfb is the value of the first resistance; Rr is the equivalent right channel impedance of the headset; and 1/x1 is the product of the gain of the left channel circuit and the gain of the first feedback circuit; and

the value of the second resistance is as follows:

where Rlfb is the value of the second resistance; Rl is the equivalent left channel impedance of the headset; and 1/x2 is the product of the gain of the right channel circuit and the gain of the second feedback circuit.

During a particular implementation, when x1=1,

During a particular implementation, when x2=1,

With Rrfb resistance, when the signal received by the left channel circuitry from the processor is the signal from the audio source ground on the motherboard, the voltages at both ends of the left channel of the headset are equal. Therefore, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the motherboard sound source ground, and the signal received by the left channel circuit from the processor is the signal from the motherboard sound source ground, the voltage difference between the two ends of the left channel of the headset is further reduced, so that crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.

At the value of Rrfb, when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is the signal from the sound source ground on the motherboard , the voltages at both ends of the headset's right channel are equal. Therefore, when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the motherboard audio source ground, and the signal received by the right channel circuit from the processor is the signal from the motherboard audio source ground, the difference the voltage between the two ends of the right channel of the headset is further reduced so that crosstalk between the left channel playback circuit and the right channel playback circuit is reduced. Thus, the separation between the right channel reproduction circuit and the left channel reproduction circuit is improved.

According to a second aspect, an embodiment of the present invention provides an audio playback circuit, wherein the audio playback circuit includes a left channel circuit, a right channel circuit, and a third current path, where: an output end of the left channel circuit is configured to connect to a first left channel end of a headset, the output end of the right channel circuit is configured to be connected to the first end of the right channel of the headset, and the second end of the left channel of the headset is connected to the second end of the right channel of the headset; the left channel circuit is configured to output the left channel audio signal to the first end of the left channel of the headset;

the right channel circuit is configured to output the right channel audio signal to the first end of the right channel of the headset; the first end of the third current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the third current path is connected to the output end of the right channel and the first end of the right channel of the headset; the third current path is configured to shunt the current output by the left channel circuit to adjust the third voltage at the input of the first end of the headset right channel when the left channel circuit outputs the left channel audio signal, where when the left channel circuit outputs the left channel audio signal and the right channel circuit does not outputs the sound signal of the right channel, the third voltage is equal to the voltage at the second end of the right channel of the headset; and

the third current path is further configured to shunt the current output by the right channel circuit to adjust the fourth voltage at the input of the first end of the left channel of the headset when the right channel circuit outputs the right channel audio signal, where when the right channel circuit outputs the right channel audio signal and the left channel circuit does not outputs the audio signal of the left channel, the fourth voltage is equal to the voltage at the second end of the left channel of the headset.

In the audio playback circuit, when the signal received by the left channel circuit from the processor is the signal from the audio source ground on the motherboard, the voltage at the input end of the left channel of the headset is changed using the third current path, so that the value of the voltage at the input end of the left channel of the headset is common ground voltage. Therefore, the voltage difference between the two ends of the left channel of the headset is reduced, so that the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced. When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, the third current path is used to equalize the voltages at both ends of the left channel of the headset. In this case, the voltage difference between the two ends of the left channel of the headset can be reduced so that crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.

In this embodiment of the present invention, current path 3 is the third current path. The equivalent resistance Rx is the first equivalent resistance, the equivalent resistance Ry is the second equivalent resistance and the equivalent resistance Re is the third equivalent resistance.

During a specific implementation, the equivalent ground resistance may also include a detection resistance used to determine if a headset is inserted into the headset interface, and the equivalent ground impedance may also include another ground resistance connected to current path 3.

When the equivalent ground resistance includes only the feedback resistance in the left channel circuit, then the equivalent resistance is Rb=R11+R13.

In an exemplary implementation, the third current path includes a third resistance, where the first end of the third resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the third resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset.

In an exemplary implementation, the output end of the left channel circuit is connected to the first left channel end of the headset via the headset interface, and the output end of the right channel circuit is connected to the first end of the right channel of the headset via the headset interface, where the equivalent resistance generated between the headset interface and the stereo headset is the first equivalent resistance Rx, and the stereo headset includes the left channel of the headset and the right channel of the headset; and

the sound source ground is connected to the second end of the left channel of the headset and the second end of the right channel of the headset through the headset interface, where the equivalent resistance generated by the headset interface connected to the sound source ground is the third equivalent resistance Re, and the sound source ground voltage is the voltage at the first end left channel of the headset when the left channel of the headset is not outputting left channel audio.

In a possible implementation, the value of the third resistance would be:

where Rfb is the value of the third resistance; Rr is the equivalent right channel impedance of the headset; Rl is the equivalent left channel impedance of the headset; and Rb is the equivalent ground resistance, where the third current path is connected to the sound source ground through the equivalent ground resistance.

Possibly, the feedback resistance Rfb could alternatively be determined based on both the left headset channel equivalent resistance R1 and the headset right channel equivalent resistance Rr.

Rc может быть определено на основании эквивалентного сопротивления R1 левого канала гарнитуры и эквивалентного сопротивления Rr правого канала гарнитуры.During a particular implementation,

Rc can be determined based on the equivalent resistance R1 of the left channel of the headset and the equivalent resistance Rr of the right channel of the headset.

During a particular implementation, Rc may be the average equivalent resistance R1 of the left channel of the headset and the equivalent resistance Rr of the right channel of the headset.

Perhaps the left channel circuitry and the right channel circuitry are integrated into the audio chip; the first end of the third current path is connected to the output end of the left channel circuit through the audio chip chip interface, and the output end of the left channel circuit is connected to the first left channel end of the headset through the audio chip chip interface; and the second end of the third current path is connected to the output end of the right channel circuit via the audio chip chip interface, and the output end of the right channel circuit is connected to the first right channel end of the headset via the audio chip chip interface.

Obviously, the crosstalk between the right channel playback circuit and the left channel playback circuit can be reduced by using the audio chip interface through the third current path without changing the internal structure of the audio chip, so that the separation between the right channel playback circuit and the left channel playback circuit is improved.

Perhaps the left channel circuitry, the right channel circuitry, and the third current path are integrated into the audio chip; and the output end of the left channel circuit and the first end of the third current path are connected to the input end of the left channel of the headset via the audio chip chip interface. The output end of the right channel circuit and the second end of the third current path are connected to the input end of the right channel of the headset through the audio chip interface.

According to a third aspect, an embodiment of the present invention provides a terminal device, where the terminal device includes a processor, an audio playback circuit, and a headset interface, where: the processor is connected to an input end of the audio playback circuit, and the processor is configured to input an audio signal to the audio playback circuit; the output end of the audio playback circuit is connected to the headset interface; the headset interface is configured to connect to an external stereo headset, where the stereo headset includes a left headset channel and a right headset channel; and the audio playback scheme is the audio playback scheme according to the first aspect, or any possible implementation of the first aspect.

According to a fourth aspect, an embodiment of the present invention provides a terminal device, where the terminal device includes a processor, an audio playback circuit, and a headset interface, where: the processor is connected to an input end of the audio playback circuit, and the processor is configured to input an audio signal to the audio playback circuit; the output end of the audio playback circuit is connected to the headset interface; the headset interface is configured to connect an external stereo headset, in which the stereo headset includes a left headset channel and a right headset channel; and the audio playback scheme is an audio playback scheme according to the second aspect or any possible implementation of the second aspect.

Brief description of the drawings

Fig. 1A and FIG. 1B are diagrams of an audio playback system according to an embodiment of the present invention;

Fig. 2 is a block diagram of an equivalent circuit of a stereo headset according to an embodiment of the present invention;

Fig. 3 is a block diagram of another audio playback system according to an embodiment of the present invention;

Fig. 4 is a block diagram of an audio playback system according to an embodiment of the present invention;

Fig. 5 is a block diagram of another audio playback system according to an embodiment of the present invention;

Fig. 6 is a block diagram of the equivalent circuits of loop 1 and loop 2 according to an embodiment of the present invention;

Fig. 7 is a block diagram of another audio playback system according to an embodiment of the present invention;

Fig. 8 is a block diagram of the equivalent circuits of loop 3 and loop 4 according to an embodiment of the present invention; and

Fig. 9 is a block diagram of a terminal device according to an embodiment of the present invention.

Implementation of the invention

The following describes the application scenario and concepts used in the embodiments of the present invention. In a stereo scenario, the left and right channels are played independently. When stereo audio is played back by a terminal device, the stereo headset and sound chip can form an audio playback loop. The audio chip may be integrated into the terminal device or may be a separate chip. The audio chip may be, for example, a coder-decoder (CODEC) chip, and may be a high-fidelity (HiFi) chip. The sound chip can support audio compression (encoder) and decompression (decoder). The sound chip can compress and decompress the audio signal with hardware, thus saving CPU resources and improving the efficiency of the terminal device. The audio chip used in the embodiments of the present invention may be a CODEC chip, a HiFi chip, another chip used for audio encoding and decoding, or a future chip used for audio encoding and decoding, which is not limited to the embodiments of the present invention.

The terminal device may include a mobile phone, a tablet computer, a desktop computer, a mobile station, a mobile unit, a radio device, a remote device, a user agent, a mobile client, a vehicle-mounted device, and the like. ., which has an audio playback function. A stereo headset can be connected to the headset interface of the terminal device via a stereo headset plug to connect to the audio chip in the terminal device.

To facilitate understanding of the embodiments of the present invention, some of the concepts or terms used in the embodiments of the present invention are described below.

(1) Headset plug and headset interface.

The stereo headset plug is the plug on the headset and can be of various types. For example, a stereo headset plug can be a 3.5 mm plug or a Type C plug. The headset interface is located on the terminal device and is configured to connect to an external headset plug. The 3.5mm plug can match the 3.5mm headset interface, and they can be connected to form a closed loop audio playback. Likewise, the Type C plug may correspond to a Type C headset interface, and they may be connected to form an audio playback loop.

Further, when the headset interface and the headset plug are of different types, the headset adapter can be connected via the headset adapter cable. For example, if the headset interface is a type-C headset interface and the headset plug is a 3.5mm plug, the 3.5mm plug can be connected to the type-C plug using the headset cable adapter, and then the type-C plug on the headset adapter cable connected to a type C headset interface to form an audio playback loop. As another example, when the headset interface is a 3.5mm headset interface and the headset plug is a Type-C plug, the Type-C plug can be connected to a 3.5mm plug using a headset adapter cable, and then to a 3.5mm plug on the headset adapter cable connects to the 3.5mm headset interface to form an audio playback loop.

Obviously, the above examples of headset interface and headset plug types are not limited to 3.5mm and C type, but can be extended to other headset interfaces and headset plugs. If the headset interface and headset plug are different types, they can be connected with a headset adapter cable to form an audio playback loop.

When the headset adapter cable is used to implement the adaptation function, the equivalent resistance between the common ground point of the two headsets and the audio source ground on the motherboard increases due to the contact resistance generated by the adapter and the wiring resistance of the adapter cable, that is, the value of Px in FIG. 3 is greatly enhanced by the headset adapter cable.

The audio source ground on the motherboard refers to the audio reference voltage, where the reference voltage can come from the processor on the motherboard. A chip and a device may be provided on the motherboard. The chip may include, for example, a sound chip; and the device may include, for example, a device forming a current path.

(2) Connection between electronic components and connection between circuits.

A connection reflects the relationship between electronic components, the relationship between an electronic component and a circuit, or the relationship between circuits. An electronic component may be, for example, a resistor, a capacitor, an inductor, or an amplifier. A circuit may be a plurality of electronic components connected by wires.

In embodiments of the present invention, connection refers to the transfer of power from one part of a circuit to another part of a circuit. For example, a connection between A and B may indicate that A and B are connected by wiring, or may indicate that A and B are connected by an electronic component or circuit. Each of A and B can be a device or a circuit.

(3) Playback state and non-playback state of the channel playback loop.

In embodiments of the present invention, left channel audio may be input to the left channel of the headset via the left channel circuit, and right channel audio may be input to the right channel of the headset via the right channel circuit. The left channel circuit and the right channel circuit may be included in the audio chip and are used to receive a digital audio signal from the processor and perform digital-to-analog conversion and amplification, and then pass the received audio signal to the left channel of the headset and the right channel of the headset.

In embodiments of the present invention, the non-playback state of the channel playback loop means that the signal received by the channel playback loop from the processor is a signal from the audio source ground on the motherboard. The playback state of the channel's playback loop means that the absolute value of the voltage of the signal received by the channel's playback loop from the processor is greater than the signal from the audio source ground on the motherboard.

In a channel playback loop, that the channel circuitry outputs the channel's audio signal could alternatively mean that the absolute value of the voltage of the signal received by the channel circuitry from the processor is greater than the signal from the audio source ground on the motherboard. The fact that the channel circuit is not outputting the channel's audio signal may mean that the voltage of the signal received by the channel circuit from the processor is equal to the ground voltage of the audio source on the motherboard. The ground voltage of the audio source on the motherboard is the reference voltage, that is, the voltage of the audio signal output by the processor when the left or right channel circuit is not outputting audio. The channel scheme may include a left channel scheme and a right channel scheme. For a detailed description of the left channel circuit and the right channel circuit, reference may be made to detailed descriptions in the embodiment described below in FIG. 4, and details are not described here again. For example, when the left channel circuit outputs the left channel audio signal, this indicates that the voltage of the signal received by the left channel circuit from the processor is equal to the signal voltage from the audio source ground on the motherboard. In embodiments of the present invention, the audio source ground is the audio source ground on the motherboard.

Fig. 1A and FIG. 1B are diagrams of an audio playback system according to an embodiment of the present invention. As shown in FIG. 1A and FIG. 1B, an audio playback system includes a terminal device 10 and a stereo headset 20. Terminal device 10 may include an audio chip 101 and terminal device 10 provides an external headset interface 102 for connecting to stereo headset 20 to form an audio playback loop. The stereo headset 20 includes a headset plug 201, where the headset plug 201 can be connected to a headset left channel and a headset right channel and connected to a headset interface 102 to form an audio playback loop.

As shown in FIG. 1A and FIG. 1B, in the audio playback system: D/A converter 1, operational amplifier 1, resistance R1, resistance R2 and resistance R3, which belong to the sound chip 101, the left channel of the headset and the sound source ground on the motherboard form the left channel playback circuit through the wires . The digital-to-analog converter 1 is configured to convert the received left channel digital audio data into an analog signal, in which the left channel digital audio data can be received from the processor. The op-amp 1 is configured to output and amplify the analog signal output by the digital-to-analog converter 1. The resistors R1 and R2 are configured to limit the current and the resistance R3 is configured to form a negative feedback loop of the op-amp 1 so that the closed-loop gain of the op-amp amplifier 1 should be stable, thus eliminating the effect of the open-loop gain of op-amp 1.

Similarly, as shown in FIG. 1A and FIG. 1B, in the audio playback system: D/A converter 2, operational amplifier 2, resistance R4, resistance R5 and resistance R6, which belong to the sound chip 101, the right channel of the headset and the sound source ground on the motherboard form the right channel playback circuit through the wires . The digital-to-analog converter 2 is configured to convert the received digital audio data of the right channel into an analog signal, and the operational amplifier 2 is used to output and amplify the analog signal at the output of the digital-to-analog converter 2. The resistors R4 and R5 are configured to limit the current, and the resistance R6 is configured to the ability to form a negative feedback loop of the op-amp 2, so that the closed-loop gain of the op-amp 2 must be stable, thereby eliminating the influence of the open-loop gain of the op-amp 2.

As shown in FIG. 1A and FIG. 1B, the left channel of the headset and the right channel of the headset are grounded through a common ground point A, which is located on the headset plug 201 and which is connected to the ground of the audio source on the motherboard inside the terminal device 10. Between the headset jack 102 and the ground of the audio source on the motherboard there is an equivalent resistance Re generated by wiring or magnetic washers.

In an audio playback system as shown in FIG. 1A and FIG. 1B, the audio chip includes a left channel circuit and a right channel circuit. The left channel circuit includes a D/A converter 1, an operational amplifier 1, a resistor R1, a resistor R2, and a resistor R3, which are connected through wiring, and the right channel circuit includes a D/A converter. 2, operational amplifier 2, resistance R4, resistance R5 and resistance R6, which are connected by wiring. The output end of the left channel circuit in the audio chip may be the interface 1 of the audio chip, and the output end of the right channel circuit may be the interface 2 of the audio chip. The stereo headset 20 may be interfaced to an audio chip through the headset interface 102 on the terminal device. The stereo headset 20 is connected to the headset interface 102 on the terminal device via the headset plug 201 .

As shown in FIG. 1A and FIG. 1V, when the absolute value of the voltage of the signal received by the left channel playback circuit from the processor is greater than that of the signal from the motherboard sound source ground, the voltage V1 of the common ground point A differs from the sound source ground voltage V0 of the motherboard due to equivalent resistance. Re, created by wiring or magnetic washers and existing between the headset jack and the ground of the sound source on the motherboard. When the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is equal to the voltage value of the signal from the audio source ground on the motherboard, the voltage value of the input end of the right channel signal of the headset is the voltage V0 of the audio source ground on the motherboard. That is, the voltages at both ends of the right channel of the headset are V0 and V1, and there is a voltage difference between the two ends of the right channel of the headset, so that current flows through the right channel of the headset. That is, the sound reproduction of the left channel of the headset affects the right channel of the headset. Similarly, the playback status of the right channel of the headset affects the left channel of the headset, so the separation between the left channel and the right channel is not good.

The following is a description of the concepts of crosstalk and separation used in embodiments of the present invention. The separation may reflect the degree of crosstalk between the left channel and the right channel. When the absolute value of the voltage of the signal received by one of the channels from the processor is greater than the ground voltage of the sound source on the motherboard, and the voltage of the signal received by another channel from the processor is the ground voltage of the sound source on the motherboard, the voltage difference can be used as a separation two channels of headsets.

When the voltage of the signal received by the left channel input end of the headset and which undergoes A/D conversion and amplification is V, and the voltage of the signal received by the headset right channel input end is the audio source ground voltage V0 on the motherboard, it is assumed that the voltage values both ends of the right channel of the headset are Vr, and the voltage values at both ends of the left channel of the headset are V1. In this case, refer to FIG. 2. FIG. 2 is an equivalent circuit diagram of a stereo headset according to an embodiment of the present invention, that is, an equivalent circuit diagram of the stereo headset shown in FIG. 1A and FIG. 1B. As shown in FIG. 2, according to Ohm's law, you can get:

When R1=Rr, according to formula (1), the following can be obtained:

where Rl is the equivalent resistance of the left channel of the headset; Rr is the equivalent right channel impedance of the headset; Re is the equivalent resistance that is generated by wiring or magnetic washers and that occurs between the headset interface and the sound source ground on the motherboard or the like; equivalent resistance generated by magnetic washers; and Rx includes one or more of the following: a contact resistance generated between the headset plug and the headset interface, an equivalent resistance that is generated by wiring or magnetic washers between the headset and the headset plug, or an equivalent resistance generated by the headset adapter cable.

It is obvious that crosstalk refers to the equivalent resistance R1 of the left channel of the headset, the equivalent resistance of Rr of the right channel of the headset and Re + Rx, and is not related to the amplitude of the input signal of the audio chip. The smaller the Re+Rx sum, the less crosstalk between the left and right channels, the better the separation between the left and right channels, and the stronger the stereoscopic feeling of the sound output from the two headsets.

The separation can be represented by the absolute value of the crosstalk. The larger the absolute value of crosstalk, the greater the separation between the left and right channels, and the stronger the stereoscopic feeling of the sound output from the two headsets.

Fig. 3 is a diagram of another audio playback system according to an embodiment of the present invention. As shown in FIG. 3, the structure of the audio playback system is formed by adding a feedback circuit to the audio playback system shown in FIG. 1A and FIG. 1B. In particular, as shown in FIG. 3, a feedback circuit 1 is added to the left channel circuit, and a feedback circuit 2 is added to the right channel circuit. When the absolute value of the voltage of the signal received by the playback circuit of the left channel from the processor is greater than that of the signal from the ground of the sound source on the motherboard, the voltage V2 at the end of Px is fed back to the input end of the right channel of the headset through the feedback circuit 2, thereby reducing voltage difference between the two ends of the right channel of the headset when the right channel path is in the non-playback state. When the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, the voltage V2 at the Rx end is fed back to the input end of the left channel of the headset through the feedback circuit 1, thereby reducing voltage difference between the two ends of the left channel of the headset when the left channel path is in the non-playing state.

In particular, both the feedback circuit 1 and the feedback circuit 2 may be voltage feedback circuits. The feedback circuit 1 may include an operational amplifier 3, a resistor R7 and a resistor R8. The resistor R8 is configured to limit the current, R7 and R8 may be configured to determine the gain of the amplifier 3. The feedback circuit 2 may include an operational amplifier 4, a resistor R9 and a resistor R10. The resistance R10 is for current limiting, R9 and R10 can be configured to determine the gain of the op-amp 4.

Ry includes one or more of the following: equivalent resistance generated by feedback wiring, or equivalent resistance generated by magnetic discs. The feedback wiring may include wiring between the headset interface and the input end of the feedback circuit 1 (or feedback circuit 2). Rx includes one or more of the following: the contact resistance generated between the headset plug and the headset interface, the equivalent resistance that is generated by wiring or magnetic washers that exists between the headset and the headset plug, or the equivalent resistance that is generated by the headset adapter cable. For a detailed description of the left channel playback circuit and the right channel playback circuit, reference may be made to the detailed descriptions in the embodiment described in FIG. 1A and FIG. 1B, and the details are again not described here.

Next, a detailed description will be given on the principle of reducing crosstalk between the left channel reproduction circuit and the right channel reproduction circuit using the feedback circuit.

When the absolute value of the voltage of the signal received by the left channel playback circuit from the processor is greater than the signal from the sound source ground on the motherboard, the feedback circuit 2 feeds back the voltage V2 at Rx to the right channel playback circuit through voltage feedback, i.e. , transmits V2 to the right channel of the headset through op-amp 2 and op-amp 4. If the product of the gain of op-amp 2 and the gain of op-amp 4 is 1/x2, the voltages at both ends of the right channel of the headset are N21x1 and V1 when the absolute value the voltage of the signal received by the right channel playback circuit from the processor is equal to the voltage value of the signal from the sound source ground on the motherboard. When Rx is much smaller than the headset left channel impedance R1 and headset right channel impedance Rr, V2/x2 and V1 are nearly equal. This is because the partial voltage is positively related to the resistance, and almost all the voltage values of the signals from the processor fall on R1, and the partial voltage on Rx is negligible, that is, V1 is almost equal to V2. When the magnification factor 1/x2 is set to 1, V2/x2 and V1 are nearly equal. That is, when the absolute value of the signal voltage received by the right channel playback circuit from the processor is equal to the voltage value of the signal from the sound source ground on the motherboard, the current on the right channel of the headset is approximately zero. Similarly, when the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, the voltages at both ends of the left channel of the headset are almost equal, so that the impact of two-channel playback sounds can be significant. reduced, thereby improving the separation between the left and right channels.

In an audio playback system as shown in FIG. 3, the audio chip includes a left channel circuit and a right channel circuit. The left channel circuit includes a D/A converter 1, an op amp 1, a resistor R1, a resistor R2, and a resistor R3, which are connected through wiring, and a right channel circuit includes a D/A converter 2, an op amp 2, a resistor R4, resistance R5 and resistance R6, which are connected by wiring. The audio chip further includes a feedback circuit 1 and a feedback circuit 2. The output end of the left channel circuit in the audio chip can be provided through the interface 3 of the audio chip, and the feedback input end of the feedback circuit 1 can be provided through the interface 4 of the audio chip. The output end of the right channel circuit can be provided through the audio chip chip interface 6, and the feedback input end of the feedback circuit 2 can be provided through the audio chip chip interface 5. The stereo headset may be provided with an interface to the audio chip via the headset interface on the terminal device, where the interface to the audio chip includes interface 3, interface 4, interface 5, and interface 6. The stereo headset is connected to the headset interface on the terminal device via a headset plug.

However, in the audio playback system shown in FIG. 3, if Rx is not negligible with respect to the headset left channel impedance Rl and headset right channel impedance Rr, for example, Rx is increased due to the headset adapter cable, the sound is generated on the headset of the other channel when one of the playback channels is played, so that the separation between left and right channels.

In order to improve separation between a left channel and a right channel, an embodiment of the present invention provides an audio playback circuit. The audio playback circuitry may include a current path, where the current path may include a first current path and a second current path. One end of the first current path may be connected to the output end of the left channel circuit and the other end of the first current path may be connected to the input end of the feedback path 2. One end of the second current path may be connected to the output end of the right channel circuit, and the other end of the second current path may be connected to the input end of feedback path 1. When the absolute value of the voltage of the signal received by the left channel playback circuit from the processor is greater than the signal received by the sound source ground on the motherboard, and when the voltage of the signal received by the right channel playback circuit from the processor is equal to the signal voltage from the sound source ground on the motherboard, the first current path is used to adjust the voltage fed back to the input end of the right channel of the headset so that the voltages at both ends of the right channel of the headset are equal when the right channel playback circuit is in the non-playing state, thereby reducing the effect of current on the right channel of the headset when playing back the playback loop of the left channel. Similarly, when the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is greater than the signal from the audio source ground on the motherboard, the second current path is used to change the feed back voltage at the left channel signal input end of the headset, so that the voltages at both ends of the left channel of the headset are equal when the left channel playback circuit is in the non-playback state, thereby reducing the influence of the current on the left channel of the headset when playing the right channel playback circuit. Obviously, the crosstalk between the left channel and the right channel can be reduced by using the current path, so that the separation between the left channel and the right channel is improved.

In particular, reference may be made to FIG. 4. FIG. 4 is a diagram of an audio playback system according to an embodiment of the present invention. As shown in FIG. 4, in the audio playback system for the left channel path, the left channel circuit in the sound chip, the left channel of the headset and the audio source ground on the motherboard form the left channel playback circuit through wiring. The voltage V3 at the end of the resistance Ry is fed back to the input end of the left channel circuit through the voltage feedback circuit 1, where the voltage feedback circuit 1 is configured to adjust the input voltage of the left channel of the headset and reduce the voltage difference between the two ends of the left channel of the headset when the signal received by the left channel circuit from the processor is a signal from the sound source ground on the motherboard, so that the crosstalk of the right channel playback circuit to the left channel playback circuit is reduced. For the right channel, similarly, the right channel circuit in the sound chip, the right channel of the headset and the sound source ground on the motherboard form the right channel playback circuit through wiring. The voltage V3 at the end of the resistance Ry is fed back to the input end of the right channel circuit through the voltage feedback circuit 2, where the voltage feedback circuit 2 is configured to apply voltage to the right channel of the headset, and reduce the voltage difference between the two ends of the right channel of the headset, when the signal received by the right channel circuit from the processor is the signal from the sound source ground on the motherboard, so that the crosstalk of the left channel playback circuit to the right channel playback circuit is reduced. Obviously, by using the voltage feedback circuit 1 and the voltage feedback circuit 2, the separation between the left channel and the right channel can be improved.

In this embodiment of the present invention, current path 1 in the context is the first current path and current path 2 is the second current path. The voltage feedback circuit 1 and the feedback circuit 1 in this context are the first feedback circuits, and the voltage feedback circuit 2 and the feedback circuit 2 are the second feedback circuits. The equivalent resistance Rx is the first equivalent resistance, the equivalent resistance Ry is the second equivalent resistance and the equivalent resistance Re is the third equivalent resistance.

As shown in FIG. 4, the output end of the left channel circuit is connected to the first end of the left channel of the headset, the input end of the first feedback circuit is connected to the second end of the left channel of the headset, and the output end of the first feedback circuit is connected to the input end of the left channel circuit. The output end of the right channel circuit is connected to the first end of the right channel of the headset, the input end of the second feedback circuit is connected to the second end of the right channel of the headset, and the output end of the second feedback circuit is connected to the input end of the right channel circuit. The second end of the left channel of the headset is connected to the second end of the right channel of the headset.

As shown in FIG. 4, the first end of the first current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first current path is connected to the input end of the second feedback circuit and the second end of the left channel of the headset.

The first end of the second current path is connected to the output end of the right channel circuit and the first end of the right channel of the headset, and the second end of the second current path is connected to the input end of the first feedback circuit and the second end of the right channel of the headset.

Next, the functions of the modules in the audio playback circuit will be described.

The left channel circuit is configured to output the left channel audio signal to the first end of the left channel of the headset.

The right channel circuit is configured to output the right channel audio signal to the first end of the right channel of the headset.

The first feedback circuit is configured to feed back the first voltage to the first end of the left channel of the headset through the left channel circuit when the right channel circuit outputs the right channel audio signal.

The second feedback circuit is configured to feed back the second voltage through the right channel circuit to the first end of the right channel of the headset when the left channel circuit outputs the left channel audio signal.

The first current path is configured to shunt the current output of the left channel circuitry to adjust the second voltage fed back to the first end of the right channel of the headset when the left channel circuitry outputs the left channel audio signal. When the left channel circuit outputs the left channel audio signal and the right channel circuit does not output the right channel audio signal, the second voltage is equal to the voltage at the other end of the right channel of the headset.

The second current path is configured to shunt the current output of the right channel circuitry to adjust the first voltage fed back to the first end of the left channel of the headset when the right channel circuitry outputs the right channel audio signal. When the right channel circuit outputs the right channel audio signal and the left channel circuit does not output the left channel audio signal, the first voltage is equal to the voltage at the second end of the left channel of the headset.

Next, with reference to FIG. 4 is a detailed description of the function of current path 1 and current path 2.

(1) Current path 2 functions when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground on the motherboard.

For current path 2, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground on the motherboard Due to the resistance of the wiring, the resistance of the magnetic bead, or the equivalent resistance of the headset adapter cable, the voltage at the common ground point A for the right channel of the headset and the left channel of the headset is V1, which is greater than the ground voltage V0 of the audio source ground on the motherboard. The right channel circuit forms a current loop through current path 2, motherboard audio source ground, and wires between current path 2 and motherboard audio source ground, that is, loop 1 in FIG. 4 to change the voltage V3 fed back to the left channel playback circuit. Loop 1 can change the voltage V3 fed back to the left channel playback circuit by shunting the current in the right channel circuit. The resistance value on current path 2 can be used to determine the voltage V3 fed back into the left channel playback circuit. Therefore, the value of the resistance on the current path 2 can be set so that the voltage fed back to the first end of the left channel of the headset is equal to V1. Therefore, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the motherboard audio source ground, and the signal received by the left channel circuit from the processor is the signal from the motherboard audio source ground, the voltages across the first and second ends of the left channel of the headset are equal to V1. The difference between the voltages at both ends of the left channel of the headset is further reduced, so that crosstalk between the right channel playback circuit and the left channel playback circuit is reduced. As shown in FIG. 4, circuit 2 is a right channel playback circuit formed when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard.

(2) Current path 1 functions when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is the signal from the sound source ground on the motherboard.

For current path 1, when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is the signal from the sound source ground on the motherboard Due to the resistance of the wiring, the resistance of the magnetic bead, or the equivalent resistance of the headset adapter cable, the voltages at the common ground point A for the left channel of the headset and the right channel of the headset are V1, which is greater than the voltage V0 of the audio source ground on the motherboard. The left channel circuitry forms a current loop through current path 1, motherboard audio source ground, and wires between current path 1 and motherboard audio source ground to change the V3 voltage fed back into the right channel playback circuit. The loop formed by connecting path 1, resistance Ry and Rx, and motherboard sound source ground to each other can change the voltage V3 fed back to the right channel playback path by the current shunt path in the left channel circuitry. The resistance value on current path 1 can be used to determine the voltage V3 fed back into the left channel playback circuit. Therefore, the resistance value of current path 1 can be set such that the voltage fed back to the first end of the right channel of the headset is V1. Therefore, when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the motherboard audio source ground, and the signal received by the right channel circuit from the processor is the signal from the motherboard audio source ground, the voltages across the first and second ends of the headset's right channel are equal to V1. The difference between the voltages at both ends of the right channel of the headset is further reduced, so that crosstalk between the left channel playback circuit and the right channel playback circuit is reduced.

In an audio playback system as shown in FIG. 4, the audio chip includes a left channel circuit, a right channel circuit, a voltage feedback circuit 1, and a voltage feedback circuit 2. The output end of the left channel circuit in the audio chip can be provided through the interface 7 of the audio chip, and the feedback input end of the voltage feedback circuit 1 can be provided through the interface 8 of the audio chip. The output end of the right channel circuit can be provided through the audio chip chip interface 10, and the feedback input end of the feedback circuit 2 can be provided through the audio chip chip interface 9.

Both current path 1 and current path 2 can be provided on the mother board of the terminal device. A chip and a device may be provided on the motherboard. The chip may include, for example, a sound chip; and the device may include, for example, a device forming a current path. As shown in FIG. 4, the current path 1 is connected to the left channel circuit through the audio chip chip interface 7, and connected to the voltage feedback circuit 1 through the audio chip chip interface 8. The current path 2 is connected to the right channel circuit through the interface 10 of the audio chip, and is connected to the voltage feedback circuit 2 through the interface 9 of the audio chip. The stereo headset can be provided with interfaces to the sound chip, current path and sound source ground on the motherboard through the headset interface on the terminal device, as well as an interface to the sound chip, including chip interface 7, chip interface 8, chip interface 9 and chip interface 10 • The stereo headset is connected to the headset interface on the target device via the headset plug.

The stereo headset headset plug can be connected to the headset interface of the terminal device, so that the left channel route is connected to the left channel input end of the headset, the common ground point A is connected to the motherboard audio source ground through wiring, magnetic washers, etc., the right channel route channel is connected to the input end of the right channel of the headset, and common ground point A is connected to the voltage feedback circuit 1 and the voltage feedback circuit 2 by means of wiring, magnetic washers or feedback wiring.

The following is a specific example of implementing a left channel circuit, a right channel circuit, a voltage feedback circuit 1, a voltage feedback circuit 2, a current path 1, and a current path 2 in the audio playback system shown in FIG. 4.

In this embodiment of the present invention, a left channel circuit in an audio chip can be implemented using an op amp and a resistor, and a right channel circuit can be implemented using an op amp and a resistor. The voltage feedback circuit 1 and the voltage feedback circuit 2 can also be implemented using an operational amplifier and a resistance. Current path 1 and current path 2 can be implemented using resistance. In particular, reference may be made to FIG. 5. FIG. 5 is a diagram of another audio playback system according to an embodiment of the present invention. It can be understood that the specific structures that are the left channel circuit, the right channel circuit, the voltage feedback circuit 1, the voltage feedback circuit 2, and the current path which are shown in FIG. 5 are used simply to describe this embodiment of the present invention, and may have other structures or variations. In this embodiment of the present invention, no restrictions are imposed.

As shown in FIG. 5, the first current path includes a first resistance. The first end of the first resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first resistance is connected to the input end of the second feedback circuit and the second end of the left channel of the headset. The second current path includes a second resistance. The first end of the second resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset, and the second end of the second resistance is connected to the input end of the first feedback circuit and the second end of the right channel of the headset.

As shown in FIG. 5, reference can be made to the left channel playback loop and the right channel playback loop in FIG. 1A and FIG. 1B and FIG. 3 with reference to the playback path of the left channel. For a detailed description of the voltage feedback circuit 1 and the voltage feedback circuit 2, reference may be made to the detailed descriptions of the feedback circuit 1 and the feedback circuit 2 in FIG. 3, and details are not described here again.

Next, with reference to specific scenarios, the functions of the current path 1 and the current path 2 illustrated in FIG. 5.

(a) Route 2 current functions

As shown in FIG. 5, the current path 2 can be implemented using the resistance Rrfb. When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is equal to the signal from the sound source ground on the motherboard due to wiring resistance , washer resistance, or equivalent resistance of the headset adapter cable, the voltage of the common ground point of the right channel of the headset and the left channel of the headset is V1. As shown in FIG. 5, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground on the motherboard, in the system audio playback, two current loops are generated: Loop 1 and Loop 2. Loop 1 is a current circuit formed by connecting the right channel circuit, current path 2, and motherboard audio source ground to each other. Loop 2 is a current loop formed by connecting the right channel circuit, the right channel of the headset, and the sound source ground on the motherboard to each other. Loop 1 can change the voltage V3 fed back to the left channel playback path by shunting the current in the right channel circuitry. The resistance Rrfb on current path 2 can be used to determine the voltage V3 fed back to the left channel playback path. Therefore, the voltage V3 fed back to the left channel circuit can be set by setting the resistance Rrfb. In addition, the resistance Rrfb is set so that the voltage at the first end of the feedback circuit 1 and the voltage at the second end of the left channel of the headset are equal to the voltage at the second end of the left channel of the headset, that is, V1.

In particular, in FIG. 6 illustrates the equivalent circuits of loop 1 and loop 2 shown in FIG. 5. FIG. 6 is an equivalent circuit diagram of loop 1 and loop 2 according to an embodiment of the present invention. The following describes how to determine the resistance value Rrfb for the following implementation: when the playback circuit of the right channel is in the playback state, the left channel path is in the non-playback state, the value of the voltage fed back to the first end of the left channel of the headset is V1.

As shown in FIG. 6, the voltage V3 between the resistances Rrfb and Ry in current path 2 is the voltage value returned to the playback path of the left channel, and the voltage value that is input to the left channel of the headset after passing through the op-amp 3 and op-amp 1 is equal to the voltage value in common ground point, that is, V1. If the product of the gain of op-amp 3 and the gain of op-amp 1 is 1/x1, V3 is increased, i.e.:

Assuming that the current flowing through loop 1 is I1 and the current flowing through loop 2 is I2, with reference to FIG. 6, the following expression can be obtained using Ohm's law:

The following can be obtained according to formula (3) and formula (4):

When x1=1, formula (5) gives the following:

According to formula (3), when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground on the motherboard, voltage V3=x1*V1 is fed back to the input end of the left channel of the headset through the op-amp 3 and op-amp 1. After the voltage V3 is on the op-amp 3 and op-amp 1, the input voltage in the left channel of the headset is V3/x1, then yes, V1. The voltage at both ends of the left channel of the headset is V1. Therefore, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the motherboard audio source ground, and the signal received by the left channel circuit from the processor is the signal from the motherboard audio source ground, the voltage difference between the two ends of the left channel of the headset is further reduced, so that crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.

(b) Current route 1 functions

Like current path 2, the voltage V3 fed back to the right channel reproduction circuit can be changed by shunting the current in the left channel circuit through current path 1. The resistance Rlfb on current path 1 can be used to determine the voltage V3 fed back to the right channel playback path. Therefore, the voltage V3 fed back to the right channel circuit can be set by setting the resistance Rlfb. In addition, the resistance Rlfb is set so that the output voltage at the first end of the right channel of the headset, after passing through the feedback circuit 2 and the right channel circuit, is equal to the output voltage at the second end of the right channel of the headset, that is, V1.

The method for determining the resistance Rrfb is similar to the method for determining the value of the resistance Rlfb. The value of the received resistance Rlfb can be used to realize the following: when the playback circuit of the left channel is in the playback state, and the right channel path is in the non-playback state, the voltage value fed back to the first end of the right channel of the headset is equal to V1, that is, equal to the voltage at the other end of the right channel of the headset.

If the product of the gain of op-amp 4 and the gain of op-amp 2 is 1/x2, the following can be obtained:

When x2=1, formula (7) yields the following:

According to formula (8), when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is the signal from the sound source ground on the motherboard board, V3=x2*V1 is fed back to the right channel input end of the headset through op amp 4 and op amp 2. After V3 is applied to op amp 4 and op amp 2, the input voltage on the right channel of the headset is V3/ x2, that is, V1. The voltage at both ends of the right channel of the headset is V1. Therefore, when the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than the signal from the motherboard audio source ground, and the signal received by the right channel circuit from the processor is the signal from the motherboard audio source ground, the voltage difference between the two ends of the right channel of the headset is further reduced so that crosstalk between the left channel playback circuit and the right channel playback circuit is reduced.

Obviously, the crosstalk between the right channel playback circuit and the left channel playback circuit can be reduced by using the audio chip chip interface through the current path formed by Rrfb and Rlfb without changing the internal structure of the audio chip, so that separation between the right channel playback circuit and the playback circuit the left channel improves.

In another possible embodiment, current path 1 and current path 2 shown in FIG. 5 may alternatively be integrated into the audio chip. The left channel circuit is connected to the left channel input end of the headset through the audio chip chip interface. The right channel circuit is connected to the right channel input end of the headset through the audio chip chip interface. Current path 1 and current path 2 are connected to the other end of Rx via the audio chip chip interface.

A stereo headset can be provided with audio chip interfaces, a current path, and an audio source ground on the motherboard via a headset interface on the terminal device. The stereo headset is connected to the headset interface on the target device via the headset plug.

In this embodiment of the present invention, Rlfb in current path 1 is the first resistance and Rrfb in current path 2 is the second resistance. As shown in FIG. 5, the first end of the first resistance is connected to the output end of the left channel circuit, and the second end of the first resistance is connected to the input end of the second feedback circuit. The first end of the second resistance is connected to the output end of the right channel circuit and the second end of the second resistance is connected to the input end of the first feedback circuit.

When the right channel circuit outputs the right channel audio signal, the voltage fed back by the first feedback circuit to the first end of the left channel of the headset is the first voltage. When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is equal to the signal from the sound source ground of the motherboard, the first voltage V3/ x1 is equal to the voltage at the second end of the left channel of the headset. When the left channel circuit outputs the left channel audio signal, the voltage fed back by the second feedback circuit to the first end of the right channel of the headset is the second voltage. When the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, the second voltage V3/ x2 is equal to the voltage at the second end of the right channel of the headset.

In an exemplary implementation, the current path may be directly connected from the output end of the left channel circuit to the output end of the right channel circuit. Fig. 7 is a diagram of another audio playback system according to an embodiment of the present invention. As shown in FIG. 7, in the audio playback system for the left channel path, the left channel circuits in the audio chip, the left channel of the headset, and the audio source ground on the motherboard form the left channel playback circuit through wiring. When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, the right channel circuit generates current loop through current path 3, that is, loop 3 in FIG. 7 to change the voltage fed back to the left channel playback path.

In a possible implementation, as shown in FIG. 7, the current path 3 can be implemented using the feedback resistance Rfb.

The current path 3 is the third current path and the feedback resistance Rfb is the third resistance. As shown in FIG. 7, the third current path includes a third resistance, where the first end of the third resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the third resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset.

In a possible implementation, as shown in FIG. 7, the left channel circuit may include a D/A converter 3, an op amp 5, a resistor R11, a resistor R12, and a resistor R13, which are connected through wiring, and a right channel circuit may include a D/A converter 4, an op amp 6 and resistance R14, resistance R15 and resistance R16, which are connected by wiring. For a detailed description of the left channel circuit and the right channel circuit, reference may be made to the respective descriptions in the embodiment described in FIG. 1A and FIG. 1B, and the details are again not described here.

Obviously, the embodiment of the present invention is described based on the following case: the current path 3 is implemented using the feedback resistance Rfb, the left channel circuit includes a digital-to-analog converter 3, an operational amplifier 5, and a resistance R11, a resistance R12, and a resistance R13, which are connected by wiring, and the right channel circuit includes a digital-to-analog converter 4, an operational amplifier 6, a resistance R14, a resistance R15 and a resistance R16. which are connected by wire. However, the current path 3, the left channel circuit and the right channel circuit shown in FIG. 7 are merely used to describe this embodiment of the present invention, and the current path 3, the left channel circuit, and the right channel circuit may have other structures or variations. In this embodiment of the present invention, no limitation is imposed.

In this embodiment of the present invention, current path 3 is the third current path. The equivalent resistance Rx is the first equivalent resistance, the equivalent resistance Ry is the first equivalent resistance, and the equivalent resistance Re is the first equivalent resistance. For descriptions of the equivalent resistances Rx, Ry, and Re, reference may be made to the detailed descriptions of the embodiments described in FIG. 1 and FIG. 3 and details are not described here again.

As shown in FIG. 4, the output end of the left channel circuit is configured to connect to the first end of the left channel of the headset, the output end of the right channel circuit is configured to connect to the first end of the right channel of the headset, and the second end of the left channel of the headset is connected to the second end of the right channel of the headset. The following describes the functions of the modules in the audio playback circuits.

The left channel circuit is configured to output the left channel audio signal to the first end of the left channel of the headset.

The right channel circuit is configured to output the right channel audio signal to the first end of the right channel of the headset.

The first end of the third current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the third current path is connected to the output end of the right channel circuit and the first end of the right channel of the headset.

The third current path is configured to shunt the current output of the left channel circuit to adjust the third input voltage at the first end of the right channel of the headset when the left channel circuit outputs the left channel audio signal. When the left channel circuit outputs the left channel audio signal and the right channel circuit does not output the right channel audio signal, the third voltage is equal to the voltage at the second end of the right channel of the headset.

The third current path is further configured to shunt the current output by the right channel circuit to adjust the fourth input voltage at the first end of the left channel of the headset when the right channel circuit outputs the right channel audio signal. When the right channel circuit outputs the right channel audio signal and the left channel circuit does not output the left channel audio signal, the fourth voltage is equal to the voltage at the second end of the left channel of the headset.

As shown in FIG. 7, when the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the ground of the sound source on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground of the motherboard, in the system audio playback, two current loops are formed: loop 3 and loop 4.

Loop 3 is a current loop that is formed by the right channel circuitry, current path 3, and equivalent ground resistance through the wiring. As shown in FIG. 7, the equivalent ground resistance may include the feedback resistance R11 and R13 in the left channel circuits. Additionally, the equivalent ground resistance may also include a detection resistance to determine if a headset is inserted into the headset interface, and the equivalent ground resistance may also include another ground resistance connected to current path 3. Loop 4 is a current loop formed by the right channel circuitry, the headset right channel, and the audio source ground on the motherboard. When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, loop 3 can change voltage at the input end of the left channel of the headset, so that the voltage at the input end of the left channel of the headset will be equal to the voltage at the common ground point, that is, V1. Therefore, the voltage difference between the two ends of the left channel of the headset is reduced, so that the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.

The following describes how to determine the resistance value Rfb to realize the following: when the playback circuit of the right channel is in the playback state and the left channel path is in the non-playback state, the voltage value fed back to the first end of the left channel of the headset is V1; and when the left channel playback circuit is in the playback state and the right channel path is in the non-playback state, the voltage value fed back to the first end of the right channel of the headset is V1.

In particular, in FIG. 8 illustrates the equivalent circuits of loop 3 and loop 4 shown in FIG. 7. FIG. 8 is an equivalent circuit diagram of loop 3 and loop 4 according to an embodiment of the present invention. With reference to FIG. 8 can be obtained using Ohm's law, the following:

where Rb is the equivalent ground resistance and when the equivalent ground resistance includes only the feedback resistance in the left channel circuit as shown in FIG. 7, Rb=R11+R13.

The following can be obtained according to formula (9):

When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the left channel circuit from the processor is the signal from the sound source ground on the motherboard, according to the formula (9 ) you can find out that the voltages at both ends of the left channel of the headset are V1. In this case, the voltage difference between the two ends of the left channel of the headset can be reduced, so that crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.

Similarly, the feedback resistance Rfb can also be expressed as:

When the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal received by the motherboard audio source ground, and the signal received by the right channel circuit from the processor is the signal from the motherboard audio source ground, the voltages at both ends of the right channel of the headset obtained by formula (11) are equal to VLB. In this case, the voltage difference between the two ends of the right channel of the headset can be reduced so that the crosstalk between the left channel playback circuit and the right channel playback circuit is reduced.

Possibly, the feedback resistance Rfb could alternatively be determined based on both the left headset channel equivalent resistance R1 and the headset right channel equivalent resistance Rr. The equivalent resistance Rl of the left channel of the headset and the equivalent resistance Rr of the right channel of the headset can be equal. In this case, formula (10) coincides with formula (11). The left headset channel equivalent resistance R1 and the headset right channel equivalent resistance Rr may alternatively be different. In this case, the feedback resistance Rfb can alternatively be expressed as:

where Rc may be determined based on the left headset channel equivalent resistance Rl and the headset right channel equivalent resistance Rr, and during a particular implementation, Rc may be the average left headset channel equivalent resistance Rl and the headset right channel equivalent resistance Rr.

Rfb in route 3 current is the third resistance. As shown in FIG. 7, the first end of the third resistance is connected to the output end of the left channel circuit, and the second end of the third resistance is connected to the output end of the right channel circuit.

When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the motherboard audio source ground, and the signal received by the left channel circuit from the processor is the signal from the motherboard audio source ground, the voltage at the first end the left channel of the headset is the fourth voltage V4. According to Ohm's law, in the third current path, the fourth voltage V4 is equal to the voltage V1 at the second end of the left channel of the headset. When the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, the voltage at the first end the right channel of the headset is equal to the third voltage. According to Ohm's law, the third voltage is equal to the voltage V1 at the second end of the right channel of the headset.

In an audio playback system as shown in FIG. 7, the audio chip includes a left channel circuit and a right channel circuit, the output end of the left channel circuit in the audio chip can be provided through the interface 11 of the audio chip, the output end of the right channel circuit can be provided through the interface 12 of the audio chip, and the path 3 current is connected to the motherboard of the terminal device through the interface 11 of the chip and the interface 12 of the chip. The audio playback system can reduce crosstalk between the left channel playback circuit and the right channel playback circuit using the audio chip interface without changing the internal structure of the audio chip, so that the separation between the left channel playback circuit and the right channel playback circuit is improved.

Fig. 9 is a diagram of a terminal device according to an embodiment of the present invention. The terminal device may be the terminal device 10 described in FIG. 1A and FIG. 1B. As shown in FIG. 9, the terminal includes a processor 901, an audio playback circuit 902, and a headset interface 903.

Processor 901 may be one or more central processing units (central processing unit, CPU). When the processor 901 is a single CPU, the CPU may be a single-core or multi-core CPU.

The processor 901 is connected to the input end of the audio playback circuit 902, and the processor 901 is configured to supply an audio signal to the audio playback circuit 902.

The output end of the audio playback circuit 902 is connected to the headset interface 903 .

The headset interface 903 is configured to connect to an external stereo headset, where the stereo headset includes a left channel headset and a right channel headset. The headset interface 903 may be the headset interface 102 shown in FIG. 1A and FIG. 1B, or the headset interface may be a C-type headset interface or a 3.5mm headset interface.

The stereo headset may be the stereo headset 20 described in FIG. 1A and FIG. 1B. The stereo headset may alternatively be the stereo headset described with reference to FIG. 3 - fig. 7.

The audio playback circuit 902 may be the audio playback circuit described with reference to the previous embodiment of FIG. 4 or FIG. 5.

When the absolute value of the voltage of the signal received by the left channel playback circuit from the processor is greater than that of the signal received by the sound source ground on the motherboard, and when the voltage of the signal received by the right channel playback circuit from the processor is equal to that of the signal from the sound source ground on the motherboard, the first current path is used to adjust the voltage fed back to the right channel input end of the headset, so that the voltages at both ends of the right channel of the headset are equal when the right channel playback circuit is in the non-play state, thereby reducing the impact of the current to the right channel of the headset when playing the playback loop of the left channel. Similarly, when the absolute value of the voltage of the signal received by the right channel playback circuit from the processor is greater than the signal from the audio source ground on the motherboard, the second current path is used to change the voltage fed back to the left channel signal input end of the headset, so that the voltages at both ends of the left channel of the headset are equal when the left channel playback circuit is in the non-playback state, thereby reducing the effect of current on the left channel of the headset when playing the right channel playback circuit. Obviously, the crosstalk between the left and right channels can be reduced by using the current path, so that the separation between the left and right channels is improved.

The audio playback circuit 902 may alternatively be the audio playback circuit described in the embodiment of FIG. 7.

When the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal from the motherboard audio source ground, and the signal received by the left channel circuit from the processor is the signal from the motherboard audio source ground, the voltage at the first end left channel of the headset is equal to the voltage at the second end of the left channel of the headset. When the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than that of the signal from the sound source ground on the motherboard, and the signal received by the right channel circuit from the processor is equal to the signal from the sound source ground on the motherboard, the voltage at the first end right channel of the headset is equal to the voltage at the second end of the right channel of the headset.

It should be noted that the terminal shown in FIG. 9 is only one implementation of this embodiment of the present invention. In an actual application, the terminal shown in FIG. 9 may further include more or fewer components, this aspect is not limited.

The above descriptions are merely specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. Any changes or substitutions within the technical scope disclosed in the present invention should be within the protection scope of the present invention. Therefore, the scope of protection of the present invention should be consistent with the scope of protection of the claims.

Claims (58)

1. An audio playback circuit, comprising a left channel circuit, a right channel circuit, a first feedback circuit, a second feedback circuit, a first current path, and a second current path, wherein: the output end of the left channel circuit is connected to the first end of the left channel of the headset, the input end of the first feedback circuit is connected to the second end of the left channel of the headset, and the output end of the first feedback circuit is connected to the input end of the left channel circuit; the output end of the right channel circuit is connected to the first end of the right channel of the headset, the input end of the second feedback circuit is connected to the second end of the right channel of the headset, and the output end of the second feedback circuit is connected to the input end of the right channel circuit, the second end of the left channel of the headset is connected to the second the end of the right channel of the headset; the first end of the first current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first current path is connected to the input end of the second feedback circuit and the second end of the left channel of the headset; the first end of the second current path is connected to the output end of the right channel circuit and the first end of the right channel of the headset, and the second end of the second current path is connected to the input end of the first feedback circuit and the second end of the right channel of the headset; the left channel circuit is configured to output the left channel audio signal to the first end of the left channel of the headset; the right channel circuit is configured to output the right channel audio signal to a first end of the right channel of the headset; the first feedback circuit is configured to feed back the first voltage to the first end of the left channel of the headset through the left channel circuit when the right channel circuit outputs the right channel audio signal; the second feedback circuit is configured to feed back the second voltage to the first end of the right channel of the headset through the right channel circuit when the left channel circuit outputs the left channel audio signal; wherein the first current path is configured to shunt the current output of the left channel circuit to adjust the second voltage supplied back to the first end of the right channel of the headset when the left channel circuit outputs the left channel audio signal, wherein when the left channel circuit outputs the left channel audio signal and the right channel circuit channel does not output the right channel audio signal, the second voltage is equal to the voltage at the second end of the right channel of the headset; and the second current path is configured to shunt the current output of the right channel circuit to adjust the first voltage fed back to the first end of the left channel of the headset when the right channel circuit outputs the right channel audio signal, wherein when the right channel circuit outputs the right channel audio signal and the left channel circuit outputs channel does not output the audio signal of the left channel, the first voltage is equal to the voltage at the second end of the left channel of the headset. 2. The scheme according to claim 1, in which: the first current path includes a first resistance, the first end of the first resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the first resistance is connected to the input end of the second feedback circuit and the second end of the left channel of the headset; and the second current path includes a second resistance, the first end of the second resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset, and the second end of the second resistance is connected to the input end of the first feedback circuit and the second end of the right channel of the headset. 3. The scheme according to claim 1, in which: the left channel circuit, the right channel circuit, the first feedback circuit and the second feedback circuit are integrated into the audio chip; the first current path is connected to the output end of the left channel circuit and the input end of the second feedback circuit through the audio chip chip interface, the output end of the left channel circuit is connected to the first left channel end of the headset through the audio chip interface, and the input end of the first feedback circuit is connected to the second end of the left channel of the headset through the sound chip chip interface; wherein the second current path is connected to the output end of the right channel circuit and the input end of the first feedback circuit through the audio chip chip interface, the output end of the right channel circuit is connected to the first end of the right channel of the headset through the audio chip interface, and the input end of the second feedback circuit is connected to the other end of the right channel of the headset through the sound chip chip interface. 4. The scheme according to claim 1, in which: the left channel circuit, the right channel circuit, the first feedback circuit, the second feedback circuit, the first current path and the second current path are integrated into the audio chip; the output end of the left channel circuit is connected to the first left channel end of the headset through the audio chip chip interface, and the input end of the first feedback circuit is connected to the second left channel end of the headset through the audio chip chip interface; and the output end of the right channel circuit is connected to the first right channel end of the headset via the audio chip chip interface, and the input end of the second feedback circuit is connected to the second right channel end of the headset via the audio chip chip interface. 5. The scheme according to claim 2, in which: the output end of the left channel circuit is connected to the first end of the left channel of the headset through the headset interface, and the output end of the right channel circuit is connected to the first end of the right channel of the headset through the headset interface, while the equivalent resistance generated between the headset interface and the stereo headset is the first equivalent resistance Rx, wherein the stereo headset contains a left headset channel and a right headset channel; the input end of the first feedback circuit is connected to the second end of the left channel of the headset via the headset interface, and the input end of the second feedback circuit is connected to the second end of the right channel of the headset via the headset interface, wherein the equivalent resistance generated between the headset interface and the feedback circuit is a second equivalent resistance Ry, and the feedback circuit includes a first feedback circuit and a second feedback circuit; and the sound source ground is connected to the second end of the left channel of the headset and the second end of the right channel of the headset through the headset interface, the equivalent resistance generated by the headset interface connected to the sound source ground is the third equivalent resistance Re, and the sound source ground voltage is the reference voltage when the left or right channel circuit does not output audio. 6. Scheme according to claim 5, in which: the value of the first resistance is as follows:

where Rrfb is the value of the first resistance; Rr is the equivalent right channel impedance of the headset; and 1/x1 is the product of the gain of the left channel circuit and the gain of the first feedback circuit; a the value of the second resistance is as follows:

where Rlfb is the value of the second resistance; Rl is the equivalent left channel impedance of the headset; and 1/x2 is the product of the gain of the right channel circuit and the gain of the second feedback circuit. 7. An audio playback circuit, comprising a left channel circuit, a right channel circuit, and a current path, wherein: the output end of the left channel circuit is configured to connect to the first end of the left channel of the headset, the output end of the right channel circuit is configured to connect to the first end of the right channel of the headset, and the second end of the left channel of the headset is connected to the second end of the right channel of the headset; the left channel circuit is configured to output the left channel audio signal to the first end of the left channel of the headset; the right channel circuit is configured to output the right channel audio signal to the first end of the right channel of the headset; the first end of the current path is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the current path is connected to the output end of the right channel circuit and the first end of the right channel of the headset; the current path is configured to shunt the current output of the left channel circuit to adjust the third input voltage at the first end of the right channel of the headset when the left channel circuit outputs the left channel audio signal, wherein when the left channel circuit outputs the left channel audio signal and the right channel circuit does not output the audio signal right channel, the third voltage is equal to the voltage at the second end of the right channel of the headset; and the current path is further configured to shunt the current output of the right channel circuit to adjust the fourth input voltage at the first end of the left channel of the headset when the right channel circuit outputs the right channel audio signal, wherein when the right channel circuit outputs the right channel audio signal and the left channel circuit does not output left channel audio signal, the fourth voltage is equal to the voltage at the second end of the left channel of the headset. 8. Scheme according to claim 7, in which: the current flow path comprises a path resistance, the first end of the path resistance is connected to the output end of the left channel circuit and the first end of the left channel of the headset, and the second end of the path resistance is connected to the output end of the right channel circuit and the first end of the right channel of the headset. 9. Scheme according to claim 8, in which: the output end of the left channel circuit is connected to the first end of the left channel of the headset through the headset interface, and the output end of the right channel circuit is connected to the first end of the right channel of the headset through the headset interface, and the equivalent resistance generated between the headset interface and the stereo headset is the first equivalent resistance Rx, and a stereo headset contains a left headset channel and a right headset channel; and the sound source ground is connected to the second end of the left channel of the headset and the second end of the right channel of the headset through the headset interface, and the equivalent resistance generated by the headset interface connected to the sound source ground is the third equivalent resistance Re, and the sound source ground voltage is the voltage at the first end of the left headset channel when the left channel of the headset is not outputting left channel audio. 10. The scheme of claim 9, wherein the path resistance value is:

where Rfb is the path resistance value; Rr is the equivalent right channel impedance of the headset; Rl is the equivalent left channel impedance of the headset; and Rb is the equivalent ground resistance, with the current path connected to the sound source ground through the equivalent ground resistance. 11. An audio playback terminal device, comprising a processor, an audio playback circuit, and a headset interface, wherein: the processor is connected to an input end of the audio playback circuit, and an output end of the audio playback circuit is connected to a headset interface; the processor is configured to input an audio signal to an audio playback circuit; the headset interface is configured to connect to an external stereo headset, wherein the stereo headset includes a left headset channel and a right headset channel; a the audio playback circuit is an audio playback circuit according to any one of claims. 1-6. 12. An audio playback terminal device, comprising a processor, an audio playback circuit and a headset interface, wherein: the processor is connected to an input end of the audio playback circuit, and an output end of the audio playback circuit is connected to a headset interface; the processor is configured to input an audio signal to an audio playback circuit; the headset interface is configured to connect to an external stereo headset, the stereo headset comprising a left headset channel and a right headset channel; and the audio playback circuit is an audio playback circuit according to any one of claims. 7-10.

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