WO2020063594A1 - 音频播放电路和终端 - Google Patents

音频播放电路和终端 Download PDF

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Publication number
WO2020063594A1
WO2020063594A1 PCT/CN2019/107555 CN2019107555W WO2020063594A1 WO 2020063594 A1 WO2020063594 A1 WO 2020063594A1 CN 2019107555 W CN2019107555 W CN 2019107555W WO 2020063594 A1 WO2020063594 A1 WO 2020063594A1
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WIPO (PCT)
Prior art keywords
circuit
channel
earphone
left channel
right channel
Prior art date
Application number
PCT/CN2019/107555
Other languages
English (en)
French (fr)
Inventor
黄停
邱钰鹏
冯英群
Original Assignee
华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to US17/281,175 priority Critical patent/US11337003B2/en
Publication of WO2020063594A1 publication Critical patent/WO2020063594A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/007—Protection circuits for transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/04—Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/033—Headphones for stereophonic communication

Definitions

  • the present application relates to the technical field of terminals, and in particular, to an audio playback circuit and a terminal.
  • the left and right channels play independently.
  • the left and right channels can be played at different times or at the same time.
  • the issue of isolation needs to be considered, that is, the two channel playback circuits must be isolated to avoid mutual influence of the sounds played by the left and right channels.
  • Two headphones in two channels are usually connected to a common ground point.
  • the common ground point needs to be connected to the sound source ground on the motherboard, and there is a wiring impedance, a bead impedance, and the like between the common ground point and the sound source ground on the motherboard. Therefore, when the absolute value of the voltage of the signal received by the processor from a channel is greater than the signal from the motherboard's sound source, the common ground point and the motherboard's sound source will exist due to the aforementioned wiring impedance and magnetic bead impedance. Voltage difference. This voltage difference causes a current to flow through the headphones of the other channel, thereby generating sound playback on the other channel, resulting in poor isolation between the left and right channels.
  • the present application discloses an audio playback circuit and a terminal, which can improve the isolation between left and right channels.
  • an embodiment of the present application 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, wherein an output terminal of the left channel circuit is used for coupling Connected to the first end of the left channel earphone, the input end of the first feedback circuit is used to couple the second end of the left channel earphone, the output end of the first feedback circuit and the left channel circuit.
  • the input end of the right channel circuit is used to couple the first end of the right channel earphone, and the input end of the second feedback circuit is used to couple the second end of the right channel earphone.
  • the output terminal of the second feedback circuit is coupled to the input terminal of the right channel circuit; the second terminal of the left channel earphone is coupled to the second terminal of the right channel earphone;
  • the first end of the first current path is respectively coupled to the output end of the left channel circuit and the first end of the left channel earphone, and the second end of the first current path is respectively connected to the second feedback
  • the input end of the circuit is coupled to the second end of the left channel earphone;
  • the first of the second current path Respectively coupled to the output end of the right channel circuit and the first end of the right channel headset, and the second end of the second current path is respectively connected to the input end of the first feedback circuit and the right
  • the second end of the channel headset is coupled;
  • the left channel circuit is configured to output a left channel audio signal to the first end of the left channel headset; and the right channel circuit is configured to output a right channel An audio signal to a first end of the right channel earphone;
  • the first feedback circuit is configured to, when the right channel circuit output
  • the first current path is used to adjust the voltage fed back to the signal input terminal of the right channel earphone, which can make the voltage of the two ends of the right channel earphone equal when the right channel playback circuit is not playing. The effect of the current generated by the channel headphones.
  • the second current path is used to change the voltage fed back to the signal input terminal of the left channel headphones, so that the voltage across the left channel headphones is equal, reducing the current impact on the left channel headphones when the right channel is played back. It can be seen that through this current path, crosstalk between the left and right channels can be reduced, and the isolation between the left and right channels can be improved.
  • the coupling represents the energy transfer from one circuit part to another circuit part.
  • the coupling may be connected through a trace, or via an electronic component or a circuit.
  • the output of the channel audio signal by the channel circuit may mean that the absolute value of the voltage received by the channel circuit from the processor signal is greater than the motherboard sound source ground.
  • the channel circuit does not output the channel audio signal may also mean that the voltage received by the channel circuit from the processor signal is equal to the voltage of the motherboard sound source ground.
  • both the first feedback circuit and the second feedback circuit may be voltage feedback circuits.
  • the first current path includes a first impedance, and a first end of the first impedance is respectively an output end of the left channel circuit and a first end of the left channel earphone. Coupled, the second end of the first impedance is respectively coupled to the input end of the second feedback circuit and the second end of the left-channel earphone; the second current path includes a second impedance, and the The first end of the second impedance is coupled to the output end of the right channel circuit and the first end of the right channel headset, respectively, and the second end of the second impedance is respectively connected to the first end of the first feedback circuit. An input end is coupled to a second end of the right-channel earphone.
  • the left channel circuit, the right channel circuit, the first feedback circuit, and the second feedback circuit are integrated in an audio chip; the first current path passes through the The chip interface of the audio chip is respectively coupled to the output terminal of the left channel circuit and the input terminal of the second feedback circuit, and the output terminal of the left channel circuit is connected to the left through the chip interface of the audio chip.
  • a first end of the channel earphone is coupled, and an input end of the first feedback circuit is coupled to a second end of the left channel earphone through a chip interface of the audio chip; the second current path passes through the The chip interface of the audio chip is respectively coupled to the output terminal of the right channel circuit and the input terminal of the first feedback circuit, and the output terminal of the right channel circuit is connected to the right channel through the chip interface of the audio chip.
  • a first end of the channel earphone is coupled, and an input end of the second feedback circuit is coupled to a second end of the right channel earphone through a chip interface of the audio chip.
  • the chip interface of the audio chip can be used to reduce the crosstalk between the right channel playback circuit and the left channel playback circuit, and improve the right channel.
  • the isolation between the channel playback circuit and the left channel playback circuit is not required to change the internal structure of the audio chip.
  • 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
  • an output terminal of the left channel circuit is coupled to a first terminal of the left channel headset through a chip interface of the audio chip, and an input terminal of the first feedback circuit passes through the audio chip.
  • a chip interface is coupled to the second end of the left-channel headset; an output end of the right-channel circuit is coupled to a first end of the right-channel headset through a chip interface of the audio chip;
  • An input terminal of the second feedback circuit is coupled to a second terminal of the right channel earphone through a chip interface of the audio chip.
  • an output end of the left channel circuit is coupled to a first end of the left channel headset through a headphone interface, and an output end of the right channel circuit is coupled through the headphone interface.
  • the equivalent impedance generated between the headset interface and the stereo headset is a first equivalent impedance Rx, and the stereo headset includes the left-channel headset and the Right channel earphone;
  • the input end of the first feedback circuit is coupled to the second end of the left channel earphone through the earphone interface, and the input end of the second feedback circuit is coupled to the earphone interface
  • the sound source ground is coupled to the second end of the left channel earphone and the second end of the right channel earphone through the headphone interface;
  • the headphone interface is coupled to the Effective impedance
  • the sound source is the motherboard sound source.
  • the sound source ground of the motherboard refers to the reference voltage of the sound signal, which can come from the processor on the motherboard.
  • Chips and devices can be set on the motherboard.
  • the chip may include, for example, an audio chip, and the device may include, for example, a device constituting a current path.
  • the resistance value of the first impedance is:
  • Rrfb is the resistance value of the first impedance
  • Rr is the equivalent impedance of the right-channel earphone
  • 1 / x1 is the amplification factor of the left channel circuit and the amplification factor of the first feedback circuit. product
  • the resistance value of the second impedance is:
  • Rlfb is the resistance value of the second impedance
  • R1 is the equivalent impedance of the left channel earphone
  • 1 / x2 is the amplification factor of the right channel circuit and the amplification factor of the second feedback circuit. product.
  • the left channel circuit when the left channel circuit receives the signal from the processor as the signal from the motherboard sound source, the voltage across the left channel headphones is equal. 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 of the motherboard sound source, the left channel circuit further reduces the voltage of the left channel headphones when the signal from the processor is the signal of the motherboard sound source. Difference to reduce crosstalk between the right channel playback circuit and the left channel playback circuit.
  • the absolute value of the voltage of the signal received from the processor in the left channel circuit is greater than the signal of the motherboard sound source.
  • the signal of the right channel receives the signal from the processor is the signal of the motherboard sound source
  • the right channel The voltage across the headphones is equal. Therefore, when the absolute value of the voltage of the signal from the processor received by the left channel is greater than the signal of the motherboard's sound source, and when the signal of the right channel receives the signal from the processor is the signal of the motherboard's sound source, the Voltage difference to reduce crosstalk between the left channel playback circuit and the right channel playback circuit. This improves the isolation between the right channel playback circuit and the left channel playback circuit.
  • an embodiment of the present application provides an audio playback circuit.
  • the audio playback circuit includes a left channel circuit, a right channel circuit, and a third current path.
  • An output terminal of the left channel circuit is used for coupling.
  • the output end of the right channel circuit is used to couple the first end of the right channel headset, the second end of the left channel headset and the right channel headset The second end is coupled;
  • the left channel circuit is configured to output a left channel audio signal to the first end of the left channel headset;
  • the right channel circuit is configured to output a right channel audio signal to all The first end of the right-channel earphone;
  • the first end of the third current path is respectively coupled to the output of the left-channel circuit and the first end of the left-channel earphone, and the third current
  • the second end of the path is respectively coupled to the output end of the right channel circuit and the first end of the right channel headset;
  • the third current path is used to output the left channel in the left channel circuit.
  • the current output from the left channel circuit is shunted to adjust the input to the right channel headphones
  • the third voltage at the first end when the left channel circuit outputs a left channel audio signal and the right channel circuit does not output a right channel audio signal, the third voltage The voltages at the second ends are equal; the third current path is further configured to shunt the current output by the right channel circuit when the right channel circuit outputs a right channel audio signal to adjust the input to the left channel
  • a fourth voltage at the first end of the earphone when the right channel circuit outputs a right channel audio signal and the left channel circuit does not output a left channel audio signal, the fourth voltage and the left channel The voltage on the second end of the headset is equal.
  • the left channel circuit changes the voltage of the input terminal of the left channel earphone when the signal from the processor is the signal of the motherboard audio source, so that the voltage value of the input terminal of the left channel earphone It is equal to the voltage of the common ground point. Therefore, the voltage difference between the two ends of the left channel earphone is reduced, and the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.
  • the third current path is used to make the left channel The voltage across the headphones is equal. At this time, the voltage difference between the left channel headphones can be reduced, and the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.
  • the current path 3 is a third current path.
  • the equivalent impedance Rx is the first equivalent impedance
  • the equivalent impedance Ry is the second equivalent impedance
  • the equivalent impedance Re is the third equivalent impedance.
  • the equivalent ground impedance may also include a detection impedance for detecting whether the earphone is inserted into the earphone interface, and the equivalent ground impedance may further include other ground impedances connected to the current path 3.
  • the equivalent impedance Rb R11 + R13.
  • the third current path includes a third impedance, and a first end of the third impedance is respectively an output end of the left channel circuit and a first end of the left channel earphone.
  • the second terminal of the third impedance is coupled to the output terminal of the right channel circuit and the first terminal of the right channel earphone respectively.
  • an output end of the left channel circuit is coupled to a first end of the left channel headset through a headphone interface, and an output end of the right channel circuit is coupled through the headphone interface.
  • the equivalent impedance generated between the headset interface and the stereo headset is a first equivalent impedance Rx, and the stereo headset includes the left-channel headset and the The right channel earphone;
  • the sound source ground is coupled to the second end of the left channel earphone and the second end of the right channel earphone through the headphone interface;
  • the headphone interface is coupled to the sound source ground to generate
  • the equivalent impedance of is the third equivalent impedance Re;
  • the voltage of the sound source ground is the voltage of the first end of the left channel earphone when the left channel circuit is not outputting the left channel audio signal.
  • the resistance value of the third impedance is:
  • Rfb is the resistance value of the third impedance
  • Rr is the equivalent impedance of the right channel earphone
  • R1 is the equivalent impedance of the left channel earphone
  • Rb is the equivalent ground impedance
  • the third A current path is coupled to the sound source ground through the equivalent ground impedance.
  • the feedback impedance Rfb may also be the equivalent impedance Rl of the left-channel headphones and the equivalent impedance of the right-channel headphones
  • Rr is determined at the same time.
  • Rc can be based on the equivalent impedance Rl of the left channel headphones and the right channel
  • the equivalent impedance Rr of the earphone is determined.
  • Rc may be the average of the equivalent impedance Rl of the left-channel earphone and the equivalent impedance Rr of the right-channel earphone.
  • the left channel circuit and the right channel circuit are integrated in an audio chip; the first end of the third current path is connected to the output of the left channel circuit through a chip interface of the audio chip. And the output end of the left channel circuit is coupled to the first end of the left channel earphone through a chip interface of the audio chip; the second end of the third current path passes the audio chip
  • the chip interface is coupled to the output terminal of the right channel circuit, and the output terminal of the right channel circuit is coupled to the first terminal of the right channel headset through the chip interface of the audio chip.
  • the chip interface of the audio chip can be used to reduce the crosstalk between the right channel playback circuit and the left channel playback circuit, and improve the right channel playback circuit and Isolation between the playback channels of the left channel.
  • the left channel circuit, the right channel circuit, and the third current path are integrated in an audio chip; an output terminal of the left channel circuit and a first end of the third current path
  • the chip interface of the audio chip is coupled to the input terminal of the left-channel earphone.
  • An output terminal of the right channel circuit and a second terminal of the third current path are coupled to an input terminal of the right channel earphone through a chip interface of the audio chip.
  • an embodiment of the present application provides a terminal.
  • the terminal includes a processor, an audio playback circuit, and a headphone interface.
  • the processor is coupled 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 coupled to the headphone interface; the headphone interface is used to connect an external stereo headset, and the stereo headset includes a left-channel headset and a right-sounder Audio headphone; the audio playback circuit is the audio playback circuit described in the first aspect or any possible implementation manner of the first aspect.
  • an embodiment of the present application provides a terminal, where the terminal includes a processor, an audio playback circuit, and a headphone interface, where the processor is coupled to an input end of the audio playback circuit, and the processor, It is used to input audio signals to the audio playback circuit; the output end of the audio playback circuit is coupled to the headphone interface; the headphone interface is used to connect external stereo headphones, and the stereo headphones include left-channel headphones and Right channel headphones; the audio playback circuit is the audio playback circuit described in the second aspect or any possible implementation manner of the second aspect.
  • FIG. 1 is a schematic structural diagram of a sound playback system according to an embodiment of the present application.
  • FIG. 2 is an equivalent circuit structural diagram of a stereo headset provided by an embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of another sound playback system according to an embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a sound playback system according to an embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of another sound playback system according to an embodiment of the present application.
  • FIG. 6 is an equivalent circuit structure diagram of a loop 1 and a loop 2 provided by an embodiment of the present application;
  • FIG. 7 is a schematic structural diagram of another sound playback system according to an embodiment of the present application.
  • FIG. 8 is an equivalent circuit structure diagram of the loop 3 and the loop 4 provided in the embodiment of the present application.
  • FIG. 9 is a schematic structural diagram of a terminal according to an embodiment of the present application.
  • the audio chip can be integrated inside the terminal, or it can be an independent chip.
  • the audio chip may be, for example, an encoder-decoder (CODEC) chip, and may be a high-fidelity (HiFi) chip.
  • the audio chip can support audio compression (decoder) and decompression (decoder).
  • the audio chip can use hardware to complete audio compression and decompression, which can save CPU resources and improve the operating efficiency of the terminal.
  • the audio chip involved in the embodiment of the present application may be a CODEC chip, a HiFi chip, or other chips used for audio codec, or a chip newly used in the future for audio codec. No restrictions.
  • the terminal may include a mobile phone, a tablet computer, a desktop computer, a mobile station, a mobile unit, a wireless unit, a remote unit, a user agent, a mobile client, an in-vehicle device, and the like with an audio playback function.
  • the stereo headset can be plugged into the headset interface of the terminal through the stereo headset plug to achieve connection with the audio chip in the terminal.
  • the stereo headphone plug is a plug located on the earphone and can be various types of plugs. For example, it can be a 3.5mm plug and a typeC plug.
  • the headphone jack is located on the terminal and is used for an external headphone plug.
  • the 3.5mm plug can be matched with a 3.5mm headphone jack to connect into a closed sound playback loop.
  • the typeC plug can match the typeC headphone jack to connect into a closed sound playback loop.
  • the headphone adapter cable when the headphone jack and the headphone plug are not the same type, you can use the headphone adapter cable to switch. For example, when the headphone jack is a typeC headphone jack and the headphone plug is a 3.5mm plug, you can use a headphone adapter cable to connect the 3.5mm plug to the typeC plug, and then connect the typeC plug on the headphone adapter cable to the typeC headphone jack to form a sound Playback loop.
  • the headphone jack is a 3.5mm headphone jack and the headphone plug is a typeC plug
  • headphone jacks and headphone plugs are not limited to 3.5mm and typeC types, but can also be extended to other headphone jacks and headphone plugs.
  • the headphone jacks and headphone plugs are not the same type, they can be connected through the headphone. Transfer to form a sound playback loop.
  • the equivalent impedance between the common ground point of the two headphones and the motherboard's sound source ground will increase due to the contact impedance and wiring impedance of the adapter cable during the transfer, as shown in Figure 3.
  • the resistance of Rx will increase significantly due to the headphone adapter.
  • the motherboard sound source ground refers to the reference voltage of the sound signal, and the reference voltage can come from the processor on the motherboard.
  • Chips and devices can be set on the motherboard.
  • the chip may include, for example, an audio chip, and the device may include, for example, a device constituting a current path.
  • Coupling reflects the connection relationship between electronic components and electronic components, between electronic components and circuits, and between circuits.
  • the electronic component may include, for example, a resistor, a capacitor, an inductor, and an amplifier.
  • the circuit may be a plurality of electronic components connected by wires.
  • the coupling represents the energy transfer from one circuit part to another circuit part.
  • a and B coupling may indicate that A and B are connected through a trace, and also that A and B are connected via an electronic component or via a circuit. Both A and B can be devices or circuits.
  • a left channel sound signal may be input to a left channel earphone through a left channel circuit
  • a right channel sound signal may be input to a right channel earphone through a right channel circuit.
  • the left channel circuit and the right channel circuit may be included in an audio chip, and are used to receive a digital state sound signal from a processor, and perform digital-to-analog conversion, amplification, and transmission to the left channel earphone and the right channel earphone.
  • the unplayed state of the channel playback circuit means that the signal received by the channel playback circuit from the processor is the motherboard sound source.
  • the playback status of the channel playback circuit means that the absolute value of the voltage received by the channel playback circuit from the processor is greater than the motherboard audio source ground.
  • the output of the channel audio signal by the channel circuit may also mean that the absolute value of the voltage received by the channel circuit from the processor signal is greater than the motherboard audio source ground.
  • the channel circuit does not output the channel audio signal may also mean that the voltage received by the channel circuit from the processor signal is equal to the voltage of the motherboard sound source ground.
  • the ground voltage of the motherboard sound source is a reference voltage, that is, the voltage of the audio signal output by the processor when the left channel circuit or the right channel circuit is not outputting audio signals.
  • the channel circuit may include a left channel circuit and a right channel circuit. For a detailed description of the left channel circuit and the right channel circuit, reference may be made to the specific description in the embodiment described in FIG. 4 below, which is not repeated here. .
  • the left channel circuit outputs a left channel audio signal it means that the voltage received by the left channel circuit from the processor is equal to the motherboard sound source ground.
  • the sound source ground of the motherboard is the sound source ground.
  • FIG. 1 is a schematic structural diagram of a sound playback system provided by an embodiment of the present application.
  • the sound playback system includes a terminal 10 and a stereo headset 20.
  • the terminal 10 may include an audio chip 101, and the terminal 10 provides an external earphone interface 102 for connecting to the stereo earphone 20 to form a sound playback loop.
  • the stereo headphone 20 includes a headphone plug 201.
  • the headphone plug 201 may be coupled to the left-channel headphones and the right-channel headphones, respectively, and connected to the headphone interface 102, thereby forming a sound playback loop.
  • a digital-to-analog converter 1 of the audio chip 101, an operational amplifier 1, impedances R1, R2, R3, a left-channel earphone, and a main board sound source constitute a left-channel playback loop through a wire.
  • the digital-to-analog converter 1 is configured to convert the left-channel audio data of the received digital signal state into an analog signal, and the left-channel audio data of the digital signal state may come from a processor.
  • the operational amplifier 1 is used for output amplification of an analog signal output from the digital-to-analog converter 1.
  • the impedances R1 and R2 are used for current limiting, and the impedance R3 is used to form a negative feedback loop of the operational amplifier 1, so that the closed-loop gain of the operational amplifier 1 tends to be stable, and the influence of the open-loop gain of the operational amplifier 1 is eliminated.
  • the digital-to-analog converter 2 in the sound playback system, the digital-to-analog converter 2, the operational amplifier 2, the impedance R4, R5, and R6 of the audio chip 101 and the right-channel headphones and the motherboard sound source constitute the right channel through a wire Playback loop.
  • the digital-to-analog converter 2 is used to convert the received right-channel audio data of the digital signal state into an analog signal, and the operational amplifier 2 is used to output-amplify the analog signal output by the digital-to-analog converter 2.
  • the impedances R4 and R5 are used for current limiting, and the impedance R6 is used to form a negative feedback loop of the operational amplifier 2, so that the closed-loop gain of the operational amplifier 2 tends to be stable, and the influence of the open-loop gain of the operational amplifier 2 is eliminated.
  • the left-channel earphone and the right-channel earphone are connected to the motherboard audio source ground on the motherboard inside the terminal 10 through a common ground point A on the earphone plug 201 to be grounded.
  • the audio chip includes a left channel circuit and a right channel circuit.
  • the left channel circuit contains digital-to-analog converters 1, operational amplifiers 1, impedances R1, R2, and R3 connected through traces
  • the right channel circuit contains digital-to-analog converters 2, operational amplifiers 2, impedance R4, connected through traces, R5 and R6.
  • the output end of the left channel circuit in the audio chip may be provided through the chip interface 1 of the audio chip, and the output end of the right channel circuit may be provided through the chip interface 2 of the audio chip.
  • An interface for accessing the audio chip to the stereo headset 20 may be provided through the headset interface 102 on the terminal.
  • the stereo headset 20 is connected to the headset interface 102 on the terminal through a headset plug 201.
  • the voltage across the right channel headphones is V0 and V1, respectively, and there is a voltage difference between the two ends of the right channel headphones, so that current flows through the right channel headphones. That is, the sound playback of the left channel headphones will have an impact on the right channel headphones. Similarly, the playback status of the right channel headphones also affects the left channel headphones, so the isolation between the left and right channels is low.
  • Isolation can reflect the degree of crosstalk between the left and right channels.
  • the absolute value of the voltage of the signal received from the processor on one channel is greater than the motherboard's sound source ground, and the voltage of the signal received from the processor on the other channel is the motherboard sound source ground, you can use the voltage ratio on the two-channel headphones As isolation.
  • FIG. 2 is an equivalent circuit structure diagram of the stereo headset provided in the embodiment of the present application, that is, an equivalent circuit structure diagram of the stereo headset shown in FIG. 1. As shown in Figure 2, according to Ohm's law, we get:
  • Rl is the equivalent impedance of the left-channel headphones
  • Rr is the equivalent impedance of the right-channel headphones
  • Re is the wiring existing between the headphone interface and the motherboard sound source ground
  • Rx contains One or more of the following: the contact impedance generated between the headphone plug and the headphone interface, the trace between the headphone to the headphone plug, the equivalent impedance generated by the magnetic beads, and the equivalent impedance generated by the headphone adapter.
  • the magnitude of crosstalk is related to the equivalent impedances of the left and right channel headphones Rl and Rr and Re + Rx, and has nothing to do with the amplitude of the signal input to the audio chip.
  • the isolation can be characterized by the absolute value of crosstalk.
  • FIG. 3 is a schematic structural diagram of another sound playback system provided by an embodiment of the present application.
  • the sound playback system is obtained by adding a feedback circuit to the sound playback system shown in FIG. 1.
  • a feedback circuit 1 is added, and for the right channel, a feedback circuit 2 is added.
  • the left channel playback circuit receives an absolute value of the signal from the processor that is greater than the signal from the motherboard audio source, the voltage V2 at the Rx end is fed back to the input of the right channel headphones through the feedback circuit 2 so that the right channel Reduce the voltage difference between the right channel headphones when the channel is not playing.
  • the voltage V2 at the Rx end is fed back to the input of the left channel headphones through the feedback circuit 1, so that the left channel When the channel is not playing, reduce the voltage difference between the two ends of the left channel headphones.
  • 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, and impedances R7 and R8.
  • the impedance R8 is used for current limiting, and R7 and R8 can be used to determine the amplification factor of the amplifier 3.
  • the feedback circuit 2 may include an operational amplifier 4 and impedances R9 and R10.
  • the impedance R10 is used for current limiting, and R9 and R10 can be used to determine the amplification factor of the amplifier 4.
  • Ry includes one or more of the following: the equivalent impedance generated by the feedback trace and the equivalent impedance generated by the magnetic beads.
  • the feedback trace may include a trace from the headphone interface to the input of the feedback circuit 1 (or the feedback circuit 2).
  • Rx includes one or more of the following: the contact impedance generated between the headphone plug and the headphone interface, the equivalent impedance generated by the traces and ferrite beads between the headphone and the headphone plug, and the equivalent impedance generated by the headphone adapter cable.
  • the feedback circuit 2 feedbacks the voltage V2 at one end of Rx to the right channel through the voltage feedback, that is, via the operational amplifier 2 And the operational amplifier 4 transmits V2 to the right channel headphones. If the product of the amplification factors of operational amplifier 2 and operational amplifier 4 is 1 / x2, when the absolute value of the voltage of the signal received from the processor on the right channel playback circuit is equal to the voltage value of the signal of the ground source of the motherboard, The voltages at both ends are V2 / x2 and V1.
  • V2 / x2 and V1 are almost equal. This is because the voltage division is positively related to the impedance. The voltage value of the signal from the processor almost falls on R1, and the voltage division on Rx can be ignored, that is, V1 is almost equal to V2.
  • the magnification 1 / x2 is set to 1, V2 / x2 and V1 are almost equal. That is, when the absolute value of the voltage of the signal received from the processor on the right channel playback circuit is equal to the voltage value of the signal from the motherboard sound source, the current on the right channel headphones is approximately zero.
  • the audio chip includes a left channel circuit and a right channel circuit.
  • the left channel circuit contains digital-to-analog converters 1, operational amplifiers 1, impedances R1, R2, and R3 connected through traces
  • the right channel circuit contains digital-to-analog converters 2, operational amplifiers 2, impedance R4, connected through traces, R5 and R6.
  • the audio chip also includes a feedback circuit 1 and a feedback circuit 2.
  • the output terminal of the left channel circuit in the audio chip can be provided through the chip interface 3 of the audio chip, and the feedback input terminal of the feedback circuit 1 can be provided through the chip interface 4 of the audio chip.
  • the output end of the right channel circuit can be provided through the chip interface 6 of the audio chip, and the feedback input end of the feedback circuit 2 can be provided through the chip interface 5 of the audio chip.
  • An audio chip interface can be provided for a stereo headset through a headphone interface on the terminal.
  • the audio chip access interface includes a chip interface 3, a chip interface 4, a chip interface 5, and a chip interface 6. Stereo headphones are connected to the headphone jack on the terminal through the headphone plug.
  • an embodiment of the present application provides an audio playback circuit.
  • the audio playback circuit may include a current path, and the current path may include a first current path and a second current path.
  • One end of the first current path may be coupled to the output end of the left channel circuit, and the other end of the first current path may be coupled to the input end of the feedback path 2.
  • One end of the second current path may be coupled to the output end of the right channel circuit, and the other end of the second current path may be coupled to the input end of the feedback path 1.
  • the first current path is used to adjust the feedback.
  • the voltage at the signal input of the right channel headphones can make the voltage across the right channel headphones equal when the right channel playback circuit is not playing, reducing the current impact on the right channel headphones when the left channel playback circuit is playing. .
  • the second current path is used to change the voltage fed back to the signal input terminal of the left channel headphones, so that the voltage across the left channel headphones is equal, reducing the current impact on the left channel headphones when the right channel is played back. It can be seen that through this current path, crosstalk between the left and right channels can be reduced, and the isolation between the left and right channels can be improved.
  • FIG. 4 is a schematic structural diagram of a sound playback system provided by an embodiment of the present application.
  • the left channel circuit in the audio chip, the left channel headphones, and the motherboard sound source ground constitute a left channel playback loop through a wire.
  • the voltage V3 at one end of the impedance Ry is fed back to the input terminal of the left channel through the voltage feedback circuit 1.
  • the voltage feedback circuit 1 is used to adjust the voltage of the left channel headphones.
  • the left channel circuit receives a signal from the processor. When the signal is the ground signal of the motherboard, the voltage difference between the two ends of the left channel earphone is reduced to reduce the crosstalk between the right channel playback circuit and the left channel playback circuit.
  • the right channel circuit in the audio chip, the right channel headphones, and the audio source ground of the motherboard form a right channel playback loop through a wire.
  • the voltage V3 at one end of the impedance Ry is fed back to the input of the right channel circuit through the voltage feedback circuit 2.
  • the voltage feedback circuit 2 is used to adjust the voltage of the right channel headphones, and the signal from the processor is received in the right channel circuit. It is to reduce the voltage difference between the right channel headphones when the signal from the motherboard sound source is used to reduce the crosstalk between the left channel playback circuit and the right channel playback circuit. It can be seen that the isolation between the left and right channels can be improved by using the voltage feedback circuit 1 and the voltage feedback circuit 2 described above.
  • the current path 1 in the previous and subsequent texts is the first current path
  • the current path 2 is the second current path.
  • the voltage feedback circuit 1 and the feedback circuit 1 are the first feedback circuit
  • the voltage feedback circuit 2 and the feedback circuit 2 are the second feedback circuit.
  • the equivalent impedance Rx is the first equivalent impedance
  • the equivalent impedance Ry is the second equivalent impedance
  • the equivalent impedance Re is the third equivalent impedance.
  • the output terminal of the left channel circuit is coupled to the first terminal of the left channel headset
  • the input terminal of the first feedback circuit is coupled to the second terminal of the left channel headset
  • the output of the first feedback circuit Is coupled to the input of the left channel circuit.
  • the output end of the right channel circuit is coupled to the first end of the right channel headset
  • the input end of the second feedback circuit is used to couple the second end of the right channel headset
  • the output end of the second feedback circuit is connected to the right channel.
  • the input of the circuit is coupled.
  • the second end of the left channel earphone is coupled to the second end of the right channel earphone.
  • the first end of the first current path is respectively coupled to the output end of the left channel circuit and the first end of the left channel earphone, and the second end of the first current path is respectively connected to the The input end is coupled to the second end of the left-channel earphone.
  • the first end of the second current path is respectively coupled to the output end of the right channel circuit and the first end of the right channel earphone, and the second end of the second current path is respectively connected to the input end of the first feedback circuit and the right channel.
  • the second end of the earphone is coupled.
  • the left channel circuit is used to output the left channel audio signal to the first end of the left channel headset.
  • the right channel circuit is used to output the right channel audio signal to the first end of the right channel headphones.
  • the first feedback circuit is configured to feed back the first voltage to the first end of the left-channel earphone through the left-channel circuit when the right-channel circuit is outputting 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 earphone through the right-channel circuit when the left-channel circuit is outputting the left-channel audio signal.
  • the first current path is used for shunting the current output by the left channel circuit when the left channel circuit outputs the left channel audio signal to adjust the second voltage fed back to the first end of the right channel earphone.
  • the second voltage is equal to the voltage of the second terminal of the right channel earphone.
  • the second current path is used to divide the current output by the right channel circuit when the right channel circuit outputs the right channel audio signal, so as to adjust the first voltage fed back to the first end of the left channel earphone.
  • the first voltage is equal to the voltage of the second terminal of the left channel earphone.
  • the right channel circuit For current path 2, when the absolute value of the voltage received by the right channel circuit from the processor is greater than the signal from the motherboard's audio source, and the left channel circuit receives the signal from the processor as the signal from the motherboard's audio source, due to the routing Impedance, magnetic bead impedance, or equivalent impedance of the earphone adapter cable, the voltage at the common ground point A of the right-channel earphone and the left-channel earphone is V1, which is greater than the main-board sound source ground voltage V0.
  • the right channel circuit forms a current loop through the current path 2, the motherboard sound source ground, and the wiring between the two, that is, loop 1 in Figure 4, to change the voltage V3 that is fed back to the left channel playback path.
  • Loop 1 can change the voltage V3 fed back to the left channel playback path by shunting the current on the right channel circuit.
  • the impedance value on the current path 2 can determine the voltage V3 that is fed back to the left channel playback path. Therefore, by setting the impedance value on the current path 2, the voltage fed back to the first end of the left-channel earphone is V1. Therefore, when the absolute value of the voltage of the signal received from the processor by the right channel circuit is greater than the signal of the motherboard sound source, and when the signal of the left channel circuit receives the signal of the motherboard sound source, the first end and The voltage at both terminals is equal to V1.
  • loop 2 is a right-channel playback loop formed when the absolute value of the voltage of the signal received by the right-channel circuit from the processor is greater than the signal of the motherboard sound source.
  • the circuit formed by the circuit path 1, the impedances Ry, Rx, and the motherboard sound source ground connection can change the voltage V3 fed back to the right channel playback path by shunting the current on the left channel circuit.
  • the impedance value on the current path 1 can determine the voltage V3 that is fed back to the left channel playback path. Therefore, by setting the impedance value on the current path 1, the voltage fed back to the first end of the right-channel earphone 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 of the motherboard sound source, and when the right channel circuit receives the signal from the processor as the signal of the motherboard sound source, the first end and the first end of the right channel headphones The voltage at both terminals is equal to V1.
  • the voltage difference between the two ends of the right channel earphone is further reduced to reduce the crosstalk between the left channel playback circuit and the right channel playback circuit.
  • 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 terminal of the left channel circuit in the audio chip may be provided through the chip interface 7 of the audio chip, and the feedback input terminal of the voltage feedback circuit 1 may be provided through the chip interface 8 of the audio chip.
  • the output terminal of the right channel circuit may be provided through the chip interface 10 of the audio chip, and the feedback input terminal of the feedback circuit 2 may be provided through the chip interface 9 of the audio chip.
  • the current path 1 and the current path 2 may both be disposed on a motherboard of the terminal. Chips and devices can be set on this motherboard.
  • the chip may include, for example, an audio chip, and the device may include, for example, a device constituting a current path.
  • the current path 1 is connected to the left channel circuit through the chip interface 7 of the audio chip, and is connected to the voltage feedback circuit 1 through the chip interface 8 of the audio chip.
  • the current path 2 is connected to the right channel circuit through the chip interface 10 of the audio chip, and is connected to the voltage feedback circuit 2 through the chip interface 9 of the audio chip.
  • the stereo headphone can be provided with an interface for accessing the audio chip, current path, and audio source ground of the motherboard through the earphone interface on the terminal.
  • the interface for accessing the audio chip includes chip interface 7, chip interface 8, chip interface 9, and chip interface 10.
  • Stereo headphones are connected to the headphone jack on the terminal through the headphone plug.
  • the headphone plug of the stereo headset can be connected to the headphone jack on the terminal, so that the left channel is connected to the input of the left channel headset, and the common ground point A is connected to the motherboard sound source ground through wiring, magnetic beads, etc.
  • the right channel is connected to the input of the right channel headphones, and the common ground point A is connected to the voltage feedback circuit 1 and the voltage feedback circuit 2 through a trace, a magnetic bead, and a feedback trace.
  • a specific implementation example of the left channel circuit, the right channel circuit, the voltage feedback circuit 1, the voltage feedback circuit 2, the current path 1, and the current path 2 in the sound playback system shown in FIG. 4 is listed below.
  • the left channel circuit in the audio chip may be implemented by an operational amplifier and an impedance
  • the right channel circuit may be implemented by an operational amplifier and an impedance
  • the voltage feedback circuit 1 and the voltage feedback circuit 2 may also be implemented by an operational amplifier and an impedance
  • the current path 1 and the current path 2 may be implemented by impedance.
  • FIG. 5 is a schematic structural diagram of another sound playback system provided by an embodiment of the present application. It can be understood that the specific structures of the left channel circuit, the right channel circuit, the voltage feedback circuit 1, the voltage feedback circuit 2 and the current path shown in FIG. 5 are only used to explain the embodiments of the present application, and other structures or Variations are not limited in the embodiments of the present application.
  • the first current path includes a first impedance.
  • the first end of the first impedance is coupled to the output end of the left channel circuit and the first end of the left channel earphone, respectively, and the second end of the first impedance is connected to the input end of the second feedback circuit and the left channel earphone respectively.
  • the second terminal is coupled.
  • the second current path includes a second impedance.
  • the first end of the second impedance is coupled to the output end of the right channel circuit and the first end of the right channel earphone, respectively, and the second end of the second impedance is connected to the input end of the first feedback circuit and the right channel earphone respectively.
  • the second terminal is coupled.
  • the current path 2 can be realized by using the impedance Rrfb.
  • the absolute value of the voltage received by the signal from the processor in the right channel circuit is greater than the signal of the motherboard sound source.
  • the signal received by the left channel circuit from the processor is When the signal is grounded on the motherboard, the voltage at the common ground point of the right-channel earphone and the left-channel earphone is V1 due to the trace impedance, the bead impedance, or the equivalent impedance of the earphone adapter cable. As shown in FIG.
  • Loop 1 is a current circuit formed by connecting the right channel circuit, the current path 2 and the sound source of the motherboard.
  • Loop 2 is a current loop formed by connecting the right channel circuit, the right channel headphones, and the motherboard's sound source. Loop 1 can change the voltage V3 fed back to the left channel playback path by shunting the current on the right channel circuit.
  • the magnitude of the impedance Rrfb on the current path 2 can 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 impedance Rrfb. Furthermore, by setting the impedance Rrfb, the voltage of the first terminal supplied to the left channel earphone and the second terminal of the left channel earphone after the feedback circuit 1 and the left channel circuit are equal to each other, both being V1.
  • FIG. 6 is an equivalent circuit structure diagram of the loop 1 and the loop 2 provided in the embodiment of the present application. The following describes how to determine the value of the impedance Rrfb to achieve: when the right channel playback loop is playing and the left channel is not playing, the voltage value of the first end of the left channel headset is V1.
  • the voltage V3 between the impedances Rrfb and Ry in the current path 2 is the voltage value that is fed back to the left channel playback path.
  • the voltage value is equal to the voltage value at the common ground point and is V1. If the amplification product of operational amplifier 3 and operational amplifier 1 is 1 / x1, then V3 is increased, that is:
  • V3 x1 * V1 (3)
  • the left channel circuit further reduces the voltage of the left channel headphones when the signal from the processor is the signal of the motherboard sound source. Difference to reduce crosstalk between the right channel playback circuit and the left channel playback circuit.
  • the current on the left channel can be shunted by the current path 1 to change the voltage V3 fed back to the right channel playback path.
  • the magnitude of the impedance Rlfb on the current path 1 can 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 impedance Rlfb. Furthermore, by setting the impedance Rlfb, the voltage supplied to the first terminal of the right channel earphone and the voltage of the second terminal of the right channel earphone after the feedback circuit 2 and the right channel circuit are equal to each other, which are both V1.
  • the method of determining the value of the impedance Rlfb can be analogized to the method of determining the impedance Rrfb.
  • the value of the obtained impedance Rlfb can be realized: when the left channel playback loop is playing and the right channel is not playing, the voltage value of the first end of the feedback to the right channel headphones is equal to V1, which is equal to the right channel headphones The voltage of the second terminal.
  • the current path 1 and the current path 2 shown in FIG. 5 may also be integrated in the audio chip.
  • the left channel circuit is connected to the input terminal of the left channel headset through the chip interface of the audio chip.
  • the right channel circuit is connected to the input terminal of the right channel headset through the chip interface of the audio chip.
  • Current path 1 and current path 2 are connected to the other end of Rx through the chip interface of the audio chip.
  • the headphone interface on the terminal can be used to provide an interface for the stereo headphones to access the audio chip, current path, and audio source ground of the motherboard.
  • Stereo headphones are connected to the headphone jack on the terminal through the headphone plug.
  • Rlfb in the current path 1 is the first impedance
  • Rrfb in the current path 2 is the second impedance.
  • the first terminal of the first impedance is coupled to the output terminal of the left channel circuit
  • the second terminal of the first impedance is coupled to the input terminal of the second feedback circuit.
  • the first terminal of the second impedance is coupled to the output terminal of the right channel circuit
  • the second terminal of the second impedance is coupled to the input terminal of the first feedback circuit.
  • the voltage fed back by the first feedback circuit to the first end of the left channel earphone is the first voltage.
  • the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the signal of the motherboard sound source, and when the signal of the left channel circuit receives the signal of the motherboard sound source, the first voltage V3 / x1 and the left The voltage at the second end of the earphone is equal.
  • the voltage fed back by the second feedback circuit to the first end of the right channel earphone is the second voltage.
  • the current path may be directly bridged from the output terminal of the left channel circuit to the output terminal of the right channel circuit.
  • FIG. 7 is a schematic structural diagram of another sound playback system according to an embodiment of the present application.
  • the left channel circuit in the audio chip, the left channel headphones, and the main board sound source constitute a left channel playback loop through a wire.
  • the absolute value of the voltage of the signal received by the right channel circuit from the processor is greater than the ground signal of the motherboard, and when the signal of the left channel circuit receives the signal of the motherboard sound source, the right channel circuit generates a current through the current path 3.
  • the loop that is, loop 3 in FIG. 7, changes the voltage fed back to the left channel playback path.
  • the current path 3 may be implemented using a feedback impedance Rfb.
  • the current path 3 is the third current path, and the feedback impedance Rfb is the third impedance.
  • the third current path includes a third impedance, and the first end of the third impedance is coupled to the output end of the left channel circuit and the first end of the left channel earphone, respectively, and the second end of the third impedance is Respectively coupled to the output end of the right channel circuit and the first end of the right channel earphone.
  • the left channel circuit may include a digital-to-analog converter 3, an operational amplifier 5, impedances R11, R12, and R13 connected through a trace
  • the right channel circuit may include a The digital-to-analog converter 4, the operational amplifier 6, and the impedances R14, R15, and R16 are connected by wires.
  • the embodiment of the present application is described by taking the following situation as an example: the current path 3 is implemented by using the feedback impedance Rfb, and the left channel circuit includes a digital-to-analog converter 3, an operational amplifier 5, impedances R11, R12, and R13, the right channel circuit includes a digital-to-analog converter 4, an operational amplifier 6, and impedances R14, R15, and R16 connected through a trace.
  • the current path 3, the left channel circuit, and the right channel circuit shown in FIG. 7 are only used to explain the embodiments of the present application.
  • the current path 3, the left channel circuit, and the right channel circuit may have other structures or variations. The embodiments of the present application are not limited.
  • the current path 3 is a third current path.
  • the equivalent impedance Rx is the first equivalent impedance
  • the equivalent impedance Ry is the second equivalent impedance
  • the equivalent impedance Re is the third equivalent impedance.
  • the output of the left channel circuit is used to couple the first end of the left channel headphones
  • the output of the right channel circuit is used to couple the first end of the right channel headphones
  • the left channel headphones The second end of is coupled to the second end of the right-channel earphone.
  • the left channel circuit is used to output the left channel audio signal to the first end of the left channel headset.
  • the right channel circuit is used to output the right channel audio signal to the first end of the right channel headphones.
  • the first end of the third current path is coupled to the output end of the left channel circuit and the first end of the left channel earphone, respectively, and the second end of the third current path is connected to the output end of the right channel circuit and the right channel respectively.
  • the first end of the earphone is coupled.
  • the third current path is used to shunt the current output by the left channel circuit when the left channel circuit outputs the left channel audio signal to adjust the third voltage input to the first end of the right channel earphone.
  • the third voltage is equal to the voltage of the second terminal of the right channel earphone.
  • the third current path is also used to shunt the current output by the right channel circuit when the right channel circuit outputs the right channel audio signal to adjust the fourth voltage input to the first end of the left channel earphone.
  • the fourth voltage is equal to the voltage of the second terminal of the left channel earphone.
  • the loop 3 is a current loop formed by the right channel circuit, the current path 3, and the equivalent ground impedance through the wiring.
  • the equivalent ground impedance may include the feedback impedances R11 and R13 in the left channel circuit.
  • the equivalent ground impedance may also include a detection impedance for detecting whether the earphone is inserted into the earphone interface, and the equivalent ground impedance may also include other ground impedances connected to the current path 3.
  • Loop 4 is a current loop formed by the right channel circuit, the right channel headphones, and the motherboard sound source ground.
  • Loop 3 can change the absolute value of the signal of the left channel earphone when the right channel circuit receives the absolute value of the signal from the processor, and the left channel circuit receives the signal from the processor.
  • the voltage makes the voltage value of the input terminal of the left-channel earphone equal to the voltage of the common ground point, and both are V1. Therefore, the voltage difference between the two ends of the left channel earphone is reduced, and the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.
  • the following describes how to determine the value of the impedance Rfb to achieve: when the right channel playback loop is playing and the left channel is not playing, the voltage value of the first end of the feedback to the left channel headphones is equal to V1. When the left channel playback loop is playing and the right channel is not playing, the voltage value of the first end of the right channel earphone is V1.
  • FIG. 8 is an equivalent circuit structure diagram of the circuits 3 and 4 provided in the embodiment of the present application. Using Ohm's law for Figure 8 gives:
  • Rb is the equivalent ground impedance.
  • the left channel circuit When the absolute value of the voltage received by the right channel circuit from the processor is greater than the signal from the motherboard's sound source, and the left channel circuit receives the signal from the processor as the signal from the motherboard's sound source, it can be obtained by formula (9).
  • the voltage across the two headphones is V1. At this time, the voltage difference between the left channel headphones can be reduced, and the crosstalk between the right channel playback circuit and the left channel playback circuit is reduced.
  • the feedback impedance Rfb can also be expressed as:
  • the absolute value of the voltage of the signal received by the left channel circuit from the processor is greater than the signal of the motherboard sound source, and the signal of the right channel received by the processor is the signal of the motherboard sound source, it can be obtained by formula (11).
  • the voltage at both ends of the channel headphones is V1. At this time, the voltage difference between the two ends of the right channel headphones can be reduced, and the crosstalk between the left channel playback circuit and the right channel playback circuit can be reduced.
  • the feedback impedance Rfb may also be determined by the equivalent impedance Rl of the left-channel headset and the equivalent impedance Rr of the right-channel headset simultaneously.
  • the equivalent impedance Rl of the left-channel earphone and the equivalent impedance Rr of the right-channel earphone may be equal, and then formula (10) and formula (11) are the same.
  • the equivalent impedance Rl of the left-channel earphone and the equivalent impedance Rr of the right-channel earphone may also be different.
  • the feedback impedance Rfb can also be expressed as:
  • Rc can be determined according to the equivalent impedance Rl of the left-channel headphones and the equivalent impedance Rr of the right-channel headphones.
  • Rc can be the equivalent impedance Rl of the left-channel headphones and the equivalent of the right-channel headphones The average value of the impedance Rr.
  • Rfb in the current path 3 is the third impedance.
  • the first terminal of the third impedance is coupled to the output terminal of the left channel circuit, and the second terminal of the third impedance is coupled to the output terminal of the right channel circuit.
  • the fourth voltage V4 is equal to the voltage V1 at the second end of the left-channel earphone.
  • the third voltage is equal to the voltage V1 of the second terminal of the right-channel earphone.
  • 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 chip interface 11 of the audio chip.
  • the right channel circuit The output end can be provided through the chip interface 12 of the audio chip, and the current path 3 is connected to the main board of the terminal through the chip interface 11 and the chip interface 12.
  • the sound playback system does not need to change the internal structure of the audio chip.
  • the chip interface of the audio chip can be used to reduce crosstalk between the left and right channel playback circuits and improve the isolation between the left and right channel playback circuits.
  • FIG. 9 is a schematic structural diagram of a terminal provided by an embodiment of the present application.
  • the terminal may be the terminal 10 described in FIG. 1.
  • the terminal includes a processor 901, an audio playback circuit 902, and a headphone interface 903, where:
  • the processor 901 may be one or more central processing units (CPUs).
  • CPUs central processing units
  • the processor 901 is a CPU
  • the CPU may be a single-core CPU or a multi-core CPU.
  • the processor 901 is coupled to an input terminal of the audio playback circuit 902, and the processor 901 is configured to input an audio signal to the audio playback circuit 902.
  • An output terminal of the audio playback circuit 902 is coupled to the headphone interface 903;
  • the headphone interface 903 is used to connect external stereo headphones.
  • the stereo headphones include left-channel headphones and right-channel headphones.
  • the earphone interface 903 may be the earphone interface 102 in FIG. 1, and the earphone interface may be a typeC earphone interface or a 3.5mm earphone interface.
  • the stereo headset may be the stereo headset 20 described in FIG. 1.
  • the stereo headphones may also be the stereo headphones described in any one of FIGS. 3-7.
  • the audio playback circuit 902 may be the audio playback circuit described in the foregoing embodiment, such as FIG. 4 or FIG. 5.
  • the first current path is used to adjust the feedback.
  • the voltage at the signal input of the right channel headphones can make the voltage across the right channel headphones equal when the right channel playback circuit is not playing, reducing the current impact on the right channel headphones when the left channel playback circuit is playing. .
  • the second current path is used to change the voltage fed back to the signal input terminal of the left channel headphones, so that the voltage across the left channel headphones is equal, reducing the current impact on the left channel headphones when the right channel is played back. It can be seen that through this current path, crosstalk between the left and right channels can be reduced, and the isolation between the left and right channels can be improved.
  • the audio playback circuit 902 may also be an audio playback circuit as described in the embodiment of FIG. 7.
  • the voltage at the first end of the left channel earphone It is equal to the voltage of the second terminal of the left channel earphone.
  • the voltage at the first end of the right channel earphone It is equal to the voltage of the second terminal of the right channel earphone.
  • the terminal shown in FIG. 9 is only an implementation manner of the embodiment of the present application. In practical applications, the terminal shown in FIG. 9 may further include more or fewer components, which is not limited herein.

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Abstract

本申请实施例提供一种音频播放电路和终端。该音频播放电路包含：第一电流通路，用于在左声道电路输出左声道音频信号时，分流左声道电路输出的电流，以调整向右声道耳机的第一端反馈的第二电压；在左声道电路输出左声道音频信号且右声道电路未输出右声道音频信号时，第二电压与右声道耳机的第二端的电压相等；第二电流通路，用于在右声道电路输出右声道音频信号时，分流右声道电路输出的电流，以调整向左声道耳机的第一端反馈的第一电压；在右声道电路输出右声道音频信号且左声道电路未输出左声道音频信号时，第一电压与左声道耳机的第二端的电压相等。本申请实施例的音频播放电路可以提高左右声道之间的隔离度。

Description

音频播放电路和终端 技术领域
本申请涉及终端技术领域，尤其涉及一种音频播放电路和终端。
背景技术
在终端播放立体声音频时，左右声道播放回路独立的进行播放。左右声道可以不同时播放，也可以同时播放。为了保证左右两个声道各自独立播放互不影响，需要考虑隔离度问题，即两个声道播放回路之间要隔离，以避免左右声道播放声音相互影响。
两个声道中的两个耳机通常会连接到共同接地点上。该共同接地点需要连接到主板上的音源地，而该共同接地点到主板上的音源地之间存在走线阻抗、磁珠阻抗等。由此，当某一声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，由于前述的走线阻抗、磁珠阻抗等会导致该共同接地点与主板音源地存在电压差。该电压差使得另一声道的耳机上有电流流过，从而在另一声道上产生声音播放，造成左右声道的隔离度差。
发明内容
本申请公开了一种音频播放电路和终端，可以提高左右声道之间的隔离度。
第一方面，本申请实施例提供一种音频播放电路。所述音频播放电路包含左声道电路、右声道电路、第一反馈电路、第二反馈电路、第一电流通路和第二电流通路，其中：所述左声道电路的输出端用于耦接左声道耳机的第一端，所述第一反馈电路的输入端用于耦接所述左声道耳机的第二端，所述第一反馈电路的输出端与所述左声道电路的输入端耦接；所述右声道电路的输出端用于耦接右声道耳机的第一端，所述第二反馈电路的输入端用于耦接所述右声道耳机的第二端，所述第二反馈电路的输出端与所述右声道电路的输入端耦接；所述左声道耳机的第二端与所述右声道耳机的第二端耦接；所述第一电流通路的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第一电流通路的第二端分别与所述第二反馈电路的输入端和所述左声道耳机的第二端耦接；所述第二电流通路的第一端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接，所述第二电流通路的第二端分别与所述第一反馈电路的输入端和所述右声道耳机的第二端耦接；所述左声道电路，用于输出左声道音频信号给所述左声道耳机的第一端；所述右声道电路，用于输出右声道音频信号给所述右声道耳机的第一端；所述第一反馈电路，用于当所述右声道电路在输出右声道音频信号时，通过所述左声道电路向所述左声道耳机的第一端反馈第一电压；所述第二反馈电路，用于当所述左声道电路在输出左声道音频信号时，通过所述右声道电路向所述右声道耳机的第一端反馈第二电压；所述第一电流通路，用于在所述左声道电路输出左声道音频信号时，分流所述左声道电路输出的电流，以调整向所述右声道耳机的第一端反馈的所述第二电压；在所述左声道电路输出左声道音频信号且所述右声道电路未输出右声道音频信号时，所述第二 电压与所述右声道耳机的第二端的电压相等；所述第二电流通路，用于在所述右声道电路输出右声道音频信号时，分流所述右声道电路输出的电流，以调整向所述左声道耳机的第一端反馈的所述第一电压；在所述右声道电路输出右声道音频信号且所述左声道电路未输出左声道音频信号时，所述第一电压与所述左声道耳机的第二端的电压相等。
使用上述的音频播放电路，在左声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道播放回路接收到来自处理器的信号等于主板音源地时，利用该第一电流通路来调节反馈回右声道耳机的信号输入端的电压，可以使得在右声道播放回路未播放状态下右声道耳机两端的电压相等，减小左声道播放回路播放时对右声道耳机产生的电流影响。类似的，在右声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，利用该第二电流通路来改变反馈回左声道耳机的信号输入端的电压，可以使得在左声道播放回路未播放状态下左声道耳机两端的电压相等，减少右声道播放回播放时对左声道耳机产生的电流影响。可见，通过该电流通路，可以减小左右声道之间的串扰，提高左右声道之间的隔离度。
其中，耦接表示一个电路部分到另一个电路部分的能量传递。耦接可以是通过走线连接，也可以是经由电子元件或者经由电路连接。
其中，声道电路输出声道音频信号可以是指该声道电路接收到来自处理器的信号的电压绝对值大于主板音源地。声道电路未输出声道音频信号也可以是指该声道电路接收到来自处理器的信号的电压等于主板音源地的电压。
具体实现中，第一反馈电路和第二反馈电路均可以是电压反馈电路。
作为一种可能的实施方式，所述第一电流通路包含第一阻抗，所述第一阻抗的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第一阻抗的第二端分别与所述第二反馈电路的输入端和所述左声道耳机的第二端耦接；所述第二电流通路包含第二阻抗，所述第二阻抗的第一端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接，所述第二阻抗的第二端分别与所述第一反馈电路的输入端和所述右声道耳机的第二端耦接。
作为一种可能的实施方式，所述左声道电路、所述右声道电路、所述第一反馈电路和所述第二反馈电路集成在音频芯片中；所述第一电流通路通过所述音频芯片的芯片接口分别与所述左声道电路的输出端和所述第二反馈电路的输入端耦接，所述左声道电路的输出端通过所述音频芯片的芯片接口与所述左声道耳机的第一端耦接，所述第一反馈电路的输入端通过所述音频芯片的芯片接口与所述左声道耳机的第二端耦接；所述第二电流通路通过所述音频芯片的芯片接口分别与所述右声道电路的输出端和所述第一反馈电路的输入端耦接，所述右声道电路的输出端通过所述音频芯片的芯片接口与所述右声道耳机的第一端耦接，所述第二反馈电路的输入端通过所述音频芯片的芯片接口与所述右声道耳机的第二端耦接。
可见，通过第一电流通路和第二电流通路，无需改变音频芯片的内部结构，利用音频芯片的芯片接口即可实现减小右声道播放回路与左声道播放回路之间的串扰，提高右声道播放回路和左声道播放回路之间的隔离度。
作为一种可能的实施方式，所述左声道电路、所述右声道电路、所述第一反馈电路、所述第二反馈电路、所述第一电流通路和所述第二电流通路集成在音频芯片中；所述左 声道电路的输出端通过所述音频芯片的芯片接口与所述左声道耳机的第一端耦接，所述第一反馈电路的输入端通过所述音频芯片的芯片接口与所述左声道耳机的第二端耦接；所述右声道电路的输出端通过所述音频芯片的芯片接口与所述右声道耳机的第一端耦接，所述第二反馈电路的输入端通过所述音频芯片的芯片接口与所述右声道耳机的第二端耦接。
作为一种可能的实施方式，所述左声道电路的输出端通过耳机接口耦接到所述左声道耳机的第一端，所述右声道电路的输出端通过所述耳机接口耦接到所述右声道耳机的第一端；其中，所述耳机接口到立体声耳机之间产生的等效阻抗为第一等效阻抗Rx，所述立体声耳机包含所述左声道耳机和所述右声道耳机；所述第一反馈电路的输入端通过所述耳机接口耦接到所述左声道耳机的第二端，所述第二反馈电路的输入端通过所述耳机接口耦接到所述右声道耳机的第二端；其中，所述耳机接口到反馈电路之间产生的等效阻抗为第二等效阻抗Ry，所述反馈电路包含所述第一反馈电路和所述第二反馈电路；音源地通过所述耳机接口耦接到所述左声道耳机的第二端和所述右声道耳机的第二端；所述耳机接口耦接到所述音源地产生的等效阻抗为第三等效阻抗Re；所述音源地的电压为所述左声道电路或所述右声道电路在未输出音频信号状态下的参考电压。
其中，音源地即为主板音源地。主板音源地是指声音信号的参考电压，该参考电压可以来源于主板上的处理器。主板上可以设置芯片和器件。芯片例如可以包含音频芯片，器件例如可以包含组成电流通路的器件。
作为一种可能的实施方式，所述第一阻抗的阻值为：
Figure PCTCN2019107555-appb-000001
其中，Rrfb为所述第一阻抗的阻值，Rr为所述右声道耳机的等效阻抗，1/x1为所述左声道电路的放大倍数和所述第一反馈电路的放大倍数的乘积；
所述第二阻抗的阻值为：
Figure PCTCN2019107555-appb-000002
其中，Rlfb为所述第二阻抗的阻值，Rl为所述左声道耳机的等效阻抗，1/x2为所述右声道电路的放大倍数和所述第二反馈电路的放大倍数的乘积。
具体实现中，当x1＝1时，
Figure PCTCN2019107555-appb-000003
具体实现中，当x2＝1时，
Figure PCTCN2019107555-appb-000004
使用上述阻抗Rrfb，在左声道电路接收到来自处理器的信号为主板音源地信号时，左声道耳机的两端电压相等。从而在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时进一步减小左声道耳机两端的电压差值，来减小右声道播放回路对左声道播放回路的串扰。
使用上述阻抗Rrfb取值，在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，右声道耳机的两端电压相等。从而在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，且右声道电路接收到来自处理器的信号为主板音源地信号时进一步减小右声道耳机两端的电压差值，来减小左声道播放回路对右声道播放回路的串扰。从而提高右声道播放回路和左声道播放回路之间的隔离度。
第二方面，本申请实施例提供一种音频播放电路，所述音频播放电路包含左声道电路、右声道电路和第三电流通路，其中：所述左声道电路的输出端用于耦接左声道耳机的第一端，所述右声道电路的输出端用于耦接右声道耳机的第一端，所述左声道耳机的第二端与所述右声道耳机的第二端耦接；所述左声道电路，用于输出左声道音频信号给所述左声道耳机的第一端；所述右声道电路，用于输出右声道音频信号给所述右声道耳机的第一端；所述第三电流通路的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第三电流通路的第二端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接；所述第三电流通路，用于在所述左声道电路输出左声道音频信号时，分流所述左声道电路输出的电流，以调整输入所述右声道耳机的第一端的第三电压；在所述左声道电路输出左声道音频信号且所述右声道电路未输出右声道音频信号时，所述第三电压与所述右声道耳机的第二端的电压相等；所述第三电流通路，还用于在所述右声道电路输出右声道音频信号时，分流所述右声道电路输出的电流，以调整输入所述左声道耳机的第一端的第四电压；在所述右声道电路输出右声道音频信号且所述左声道电路未输出左声道音频信号时，所述第四电压与所述左声道耳机的第二端的电压相等。
使用上述的音频播放电路，利用第三电流通路，左声道电路接收到来自处理器的信号为主板音源地信号时改变左声道耳机的输入端的电压，使得左声道耳机的输入端的电压值和共同接地点的电压相等。从而减小左声道耳机两端的电压差值，减小右声道播放回路对左声道播放回路的串扰。当右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，利用第三电流通路，使得左声道耳机两端的电压相等，此时可以减小左声道耳机两端的电压差值，减小右声道播放回路对左声道播放回路的串扰。
本申请实施例中，电流通路3即为第三电流通路。等效阻抗Rx即为第一等效阻抗，等效阻抗Ry为第二等效阻抗，等效阻抗Re为第三等效阻抗。
具体实现中，等效接地阻抗还可以包含用于检测耳机是否插入耳机接口的检测阻抗，等效接地阻抗还可以包含与电流通路3连接的其他接地阻抗。
当等效接地阻抗仅包含左声道电路中的反馈阻抗时，等效阻抗Rb＝R11+R13。
在一种可能的实施方式中，所述第三电流通路包含第三阻抗，所述第三阻抗的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第三阻抗的第二端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接。
在一种可能的实施方式中，所述左声道电路的输出端通过耳机接口耦接到所述左声道耳机的第一端，所述右声道电路的输出端通过所述耳机接口耦接到所述右声道耳机的第一端；其中，所述耳机接口到立体声耳机之间产生的等效阻抗为第一等效阻抗Rx，所述立体声耳机包含所述左声道耳机和所述右声道耳机；音源地通过所述耳机接口耦接到所述左声道耳机的第二端、所述右声道耳机的第二端；所述耳机接口耦接到所述音源地产生的等效阻抗为第三等效阻抗Re；所述音源地的电压为所述左声道电路未输出左声道音频信号状态下所述左声道耳机的第一端的电压。
在一种可能的实施方式中，所述第三阻抗的阻值为：
Figure PCTCN2019107555-appb-000005
或，
Figure PCTCN2019107555-appb-000006
其中，Rfb为所述第三阻抗的阻值，Rr为所述右声道耳机的等效阻抗，Rl为所述左声道耳机的等效阻抗，Rb为等效接地阻抗，所述第三电流通路通过所述等效接地阻抗与所述音源地耦接。
可选的，反馈阻抗Rfb还可以是由左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗
Rr同时确定的。具体实现中，
Figure PCTCN2019107555-appb-000007
Rc可以根据左声道耳机的等效阻抗Rl和右声道
耳机的等效阻抗Rr确定，具体实现中，Rc可以是左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr的均值。
可选的，所述左声道电路和所述右声道电路集成在音频芯片中；所述第三电流通路的第一端通过所述音频芯片的芯片接口与所述左声道电路的输出端耦接，所述左声道电路的输出端通过所述音频芯片的芯片接口与所述左声道耳机的第一端耦接；所述第三电流通路的第二端通过所述音频芯片的芯片接口与所述右声道电路的输出端耦接，所述右声道电路的输出端通过所述音频芯片的芯片接口与所述右声道耳机的第一端耦接。
可见，通过第三电流通路，无需改变音频芯片的内部结构，利用音频芯片的芯片接口即可实现减小右声道播放回路与左声道播放回路之间的串扰，提高右声道播放回路和左声道播放回路之间的隔离度。
可选的，所述左声道电路、所述右声道电路和所述第三电流通路集成在音频芯片中；所述左声道电路的输出端和所述第三电流通路的第一端通过所述音频芯片的芯片接口与所述左声道耳机的输入端耦接。所述右声道电路的输出端和所述第三电流通路的第二端通过所述音频芯片的芯片接口与所述右声道耳机的输入端耦接。
第三方面，本申请实施例提供一种终端，所述终端包括处理器、音频播放电路和耳机接口，其中：所述处理器与所述音频播放电路的输入端耦接，所述处理器用于向所述音频播放电路输入音频信号；所述音频播放电路的输出端与所述耳机接口耦接；所述耳机接口用于连接外部的立体声耳机，所述立体声耳机包括左声道耳机和右声道耳机；所述音频播放电路是第一方面或第一方面任一种可能的实施方式所描述的音频播放电路。
第四方面，本申请实施例提供一种终端，所述终端包括处理器、音频播放电路和耳机接口，其中：所述处理器与所述音频播放电路的输入端耦接，所述处理器，用于向所述音频播放电路输入音频信号；所述音频播放电路的输出端与所述耳机接口耦接；所述耳机接口用于连接外部的立体声耳机，所述立体声耳机包括左声道耳机和右声道耳机；所述音频播放电路是第二方面或第二方面任一种可能的实施方式所描述的音频播放电路。
附图说明
图1是本申请实施例提供的一种声音播放系统的结构示意图；
图2是本申请实施例提供的立体声耳机的等效电路结构图；
图3是本申请实施例提供的另一种声音播放系统的结构示意图；
图4是本申请实施例提供的一种声音播放系统的结构示意图；
图5是本申请实施例提供的另一种声音播放系统的结构示意图；
图6是本申请实施例提供的回路1和回路2的等效电路结构图；
图7是本申请实施例提供的又一种声音播放系统的结构示意图；
图8是本申请实施例提供的回路3和回路4的等效电路结构图；
图9是本申请实施例提供的一种终端的结构示意图。
具体实施方式
下面介绍本申请实施例涉及的应用场景和概念。在立体声场景下，左右声道独立的进行播放。在终端播放立体声时，立体声耳机和音频芯片可以构成声音播放回路。其中，音频芯片可以集成在终端内部，也可以是独立的芯片。音频芯片例如可以是音频编译码(coder-decoder，CODEC)芯片，可以是高保真(high-fidelity，HiFi)芯片。音频芯片可以支持音频压缩(coder)与解压缩(decoder)。音频芯片可以使用硬件完成音频的压缩和解压缩，可以节省CPU的资源，提高终端的运行效率。本申请实施例涉及的音频芯片可以是CODEC芯片，也可以是HiFi芯片，还可以是其他用于音频编解码的芯片，或者未来新出现的用于音频编解码的芯片，本申请实施例对此不作限制。
其中，终端可以包括具有音频播放功能的手机、平板电脑、台式机、移动台(mobile station)、移动单元(mobile unit)、无线单元，远程单元、用户代理、移动客户端、车载设备等等。立体声耳机可以通过立体声耳机插头插接在终端的耳机接口上，实现和终端中的音频芯片连接。
为了便于理解本申请实施例，下面对本申请实施例涉及的一些概念或术语进行解释。
(1)耳机插头和耳机接口
立体声耳机插头是位于耳机上的插头，可以是各种类型的插头。例如可以为3.5mm插头和typeC插头。耳机接口位于终端上，用于外接耳机插头。3.5mm插头可以匹配3.5mm的耳机接口，来连接成闭合的声音播放回路。同样的，typeC插头可以匹配typeC的耳机接口，来连接成闭合的声音播放回路。
另外，在耳机接口和耳机插头不是同样的类型时，可以通过耳机转接线来进行转接。例如，在耳机接口为typeC耳机接口，耳机插头为3.5mm插头时，可以使用耳机转接线将3.5mm插头连接到typeC插头，再将耳机转接线上的typeC插头连通到typeC耳机接口，从而构成声音播放回路。又例如，在耳机接口为3.5mm耳机接口，耳机插头为插头typeC插头时，可以使用耳机转接线将typeC插头连接到3.5mm插头，再将耳机转接线上的3.5mm插头连通到3.5mm耳机接口，从而构成声音播放回路。
可以理解的，上述对耳机接口和耳机插头的类型举例不限于3.5mm和typeC类型，也可以扩展到其他耳机接口和耳机插头，当耳机接口和耳机插头不是同样的类型时均可以通过耳机转接线转接，来形成声音播放回路。
使用耳机转接线实现转接功能时，由于转接会产生接触阻抗、转接线的走线阻抗，两个耳机的共同接地点与主板音源地之间的等效阻抗会增大，即图3中Rx的阻值由于耳机转接线会显著增大。
其中，主板音源地是指声音信号的参考电压，该参考电压可以来源于主板上的处理器。主板上可以设置芯片和器件。芯片例如可以包含音频芯片，器件例如可以包含组成 电流通路的器件。
(2)电子元件、电路之间的耦接
耦接反映电子元件与电子元件之间、电子元件与电路之间、电路与电路之间的连接关系。其中，电子元件例如可以包含电阻、电容、电感和放大器。电路可以是多个电子元器件通过导线连接。
本申请实施例中，耦接表示一个电路部分到另一个电路部分的能量传递。例如，A和B耦接可以表示A和B通过走线连接，也可以表示A和B经由电子元件或者经由电路连接。其中的A、B均可以是器件或者电路。
(3)声道播放回路的播放状态和未播放状态
本申请实施例中，可以通过左声道电路将左声道的声音信号输入左声道耳机，通过右声道电路将右声道的声音信号输入右声道耳机。左声道电路和右声道电路可以包含在音频芯片中，用于接收来自处理器的数字状态的声音信号，并进行数模转换、放大后传输给左声道耳机和右声道耳机。
本申请实施例中，声道播放回路的未播放状态是指该声道播放回路接收到来自处理器的信号为主板音源地。声道播放回路播放状态是指该声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地。
在声道播放回路中，声道电路输出声道音频信号也可以是指该声道电路接收到来自处理器的信号的电压绝对值大于主板音源地。声道电路未输出声道音频信号也可以是指该声道电路接收到来自处理器的信号的电压等于主板音源地的电压。该主板音源地电压为参考电压，即左声道电路或右声道电路在未输出音频信号状态下处理器输出的音频信号的电压。其中，声道电路可以包含左声道电路和右声道电路，关于左声道电路和右声道电路的具体描述可以参考后文图4所描述的实施例中的具体描述，这里不再赘述。例如，左声道电路在输出左声道音频信号时，即是表明左声道电路接收到来自处理器的信号的电压等于主板音源地。本申请实施例中，主板音源地即为音源地。
请参阅图1，图1是本申请实施例提供的一种声音播放系统的结构示意图。如图1所示，声音播放系统包含终端10和立体声耳机20。终端10可以包含音频芯片101，且终端10对外提供耳机接口102，用于与立体声耳机20连接构成声音播放回路。立体声耳机20包括耳机插头201，耳机插头201可以分别与左声道耳机和右声道耳机耦接，并接入耳机接口102，从而构成声音播放回路。
如图1所示，该声音播放系统中，音频芯片101的数模转换器1、运算放大器1、阻抗R1、R2、R3、左声道耳机和主板音源地通过导线组成左声道播放回路。其中，数模转换器1用于将接收到的数字信号状态的左声道音频数据转换为模拟信号，该数字信号状态的左声道音频数据可以来自处理器。运算放大器1用于对数模转换器1输出的模拟信号进行输出放大。阻抗R1和R2用于限流，阻抗R3用于组成运算放大器1的负反馈回路，使得运算放大器1的闭环增益趋于稳定，消除运算放大器1的开环增益的影响。
类似的，如图1所示，该声音播放系统中，音频芯片101的数模转换器2、运算放大器2、阻抗R4、R5、R6以及右声道耳机和主板音源地通过导线组成右声道播放回路。其中，数模转换器2用于将接收到的数字信号状态的右声道音频数据转换为模拟信号， 运算放大器2用于对数模转换器2输出的模拟信号进行输出放大。阻抗R4和R5用于限流，阻抗R6用于组成运算放大器2的负反馈回路，使得运算放大器2的闭环增益趋于稳定，消除运算放大器2的开环增益的影响。
如图1所示，左声道耳机和右声道耳机通过耳机插头201上的共同接地点A连接到终端10内部的主板上的主板音源地来接地。耳机插口102与主板音源地之间存在的走线、磁珠产生的等效阻抗Re。
该声音播放系统中，如图1所示，音频芯片中包含左声道电路和右声道电路。左声道电路包含通过走线连接的数模转换器1、运算放大器1、阻抗R1、R2和R3，右声道电路包含通过走线连接的数模转换器2、运算放大器2、阻抗R4、R5和R6。音频芯片中左声道电路的输出端可以通过音频芯片的芯片接口1提供，右声道电路的输出端可以通过音频芯片的芯片接口2提供。可以通过终端上的耳机接口102为立体声耳机20提供接入音频芯片的接口。立体声耳机20通过耳机插头201接入终端上的耳机接口102。
如图1所示，当左声道播放回路上接收到来自处理器的信号的电压绝对值大于主板音源地信号时，由于耳机插口与主板音源地之间存在的走线、磁珠产生的等效阻抗Re，该共同接地点A的电压V1与主板音源地V0存在电压差。而当右声道播放回路接收到来自处理器的信号的电压绝对值等于主板音源地信号时，右声道耳机的信号输入端的电压值即为主板音源地V0。即右声道耳机两端的电压分别为V0和V1，右声道耳机的两端有电压差，从而有电流流过右声道耳机。即左声道耳机的声音播放会在右声道耳机产生影响。同样的，右声道耳机播放状态也会对左声道耳机产生影响，从而左右声道之间的隔离度较低。
下面介绍本申请实施例涉及的串扰和隔离度得概念。隔离度可以反映左、右两个声道之间的串扰(crosstalk)的程度。当其中一个声道从处理器接收到的信号的电压绝对值大于主板音源地，另一个声道从处理器接收到信号的电压为主板音源地时，可以用两声道的耳机上的电压比值作为隔离度。
当左声道耳机的输入端接收到经过模数转换、放大后的电压为V，右声道耳机的输入端接收到的电压为主板音源地V0，设右声道耳机两端的电压值Vr，左声道耳机两端的电压值Vl。在该情况下，请参阅图2，图2是本申请实施例提供的立体声耳机的等效电路结构图，即图1中所示的立体声耳机的等效电路结构图。如图2所示，依据欧姆定律可得：
Figure PCTCN2019107555-appb-000008
当Rl＝Rr时，根据公式(1)可得：
Figure PCTCN2019107555-appb-000009
其中，Rl为左声道耳机的等效阻抗，Rr为右声道耳机的等效阻抗，Re为耳机接口与主板音源地之间存在的走线、磁珠产生的等效阻抗等，Rx包含以下中的一种或多种：耳机插头与耳机接口之间产生的接触阻抗、耳机到耳机插头之间的走线、磁珠产生的等效阻抗和耳机转接线产生的等效阻抗。
可见，串扰的大小与左、右声道耳机等效阻抗Rl和Rr以及Re+Rx相关，与输入音频芯片的信号的幅值无关。Re+Rx越小，左右声道之间的串扰越小，左右声道之间的隔离度越好，通过两个耳机输出声音的立体感越强。
隔离度可以用串扰的绝对值来表征，串扰的绝对值越大，左右声道之间的隔离度越大，通过两个耳机输出声音的立体感越强。
请参阅图3，图3是本申请实施例提供的另一种声音播放系统的结构示意图。如图3所示，该声音播放系统是在图1所示出的声音播放系统的基础上增加反馈电路得到的。具体的，如图3所示，对于左声道回路，增加反馈电路1，对于右声道回路，增加反馈电路2。在左声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，通过反馈电路2来将Rx一端的电压V2反馈到右声道耳机的输入端，从而在右声道通路处于未播放状态时减小右声道耳机的两端电压差。在右声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，通过反馈电路1来将Rx一端的电压V2反馈到左声道耳机的输入端，从而在左声道通路处于未播放状态时减小左声道耳机的两端电压差。
具体的，反馈电路1和反馈电路2均可以是电压反馈电路。反馈电路1可以包括运算放大器3、阻抗R7和R8。其中阻抗R8用于限流，R7和R8可以用于确定放大器3的放大倍数。反馈电路2可以包括运算放大器4、阻抗R9和R10。其中阻抗R10用于限流，R9和R10可以用于确定放大器4的放大倍数。
其中，Ry包含以下中的一种或多种：反馈走线产生的等效阻抗和磁珠产生的等效阻抗。反馈走线可以包含耳机接口到反馈电路1(或者反馈电路2)的输入端之间的走线。Rx包含以下中的一种或多种：耳机插头与耳机接口之间产生的接触阻抗、耳机到耳机插头之间的走线和磁珠产生的等效阻抗、耳机转接线产生的等效阻抗。关于左声道播放回路、右声道播放回路的具体描述可以参考图1所描述实施例的具体介绍，这里不再赘述。
下面具体介绍利用反馈电路减小左右声道播放回路之间的串扰的原理。
当左声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，反馈电路2通过电压反馈将Rx一端的电压V2反馈到右声道播放回路上，即经由运算放大器2和运算放大器4将V2传输给右声道耳机。如果运算放大器2和运算放大器4的放大倍数的乘积为1/x2，则在右声道播放回路接收到来自处理器的信号的电压绝对值等于主板音源地信号的电压值时右声道耳机的两端电压分别为V2/x2和V1。当Rx远小于左右声道耳机的阻抗Rl、Rr时，V2/x2和V1几乎相等。这是由于分压与阻抗大小正相关，来自处理器的信号的电压值几乎均落在R1上，Rx上分压可以忽略，即V1几乎等于V2。当设置放大倍数1/x2为1时，V2/x2和V1几乎相等。即在右声道播放回路接收到来自处理器的信号的电压绝对值等于主板音源地信号的电压值时，右声道耳机上的电流近似为零。类似的，在右声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，左声道耳机两侧的电压也几乎相等，可以显著减小两个声道播放声音之间的影响，从而提高左右声道之间的隔离度。
该声音播放系统中，如图3所示，音频芯片中包含左声道电路和右声道电路。左声道电路包含通过走线连接的数模转换器1、运算放大器1、阻抗R1、R2和R3，右声道电路包含通过走线连接的数模转换器2、运算放大器2、阻抗R4、R5和R6。音频芯片中还包含反馈电路1和反馈电路2。音频芯片中左声道电路的输出端可以通过音频芯片 的芯片接口3提供，反馈电路1的反馈输入端可以通过音频芯片的芯片接口4提供。右声道电路的输出端可以通过音频芯片的芯片接口6提供，反馈电路2的反馈输入端可以通过音频芯片的芯片接口5提供。可以通过终端上的耳机接口为立体声耳机提供接入音频芯片的接口，该接入音频芯片的接口包含芯片接口3、芯片接口4、芯片接口5和芯片接口6。立体声耳机通过耳机插头接入终端上的耳机接口。
然而，图3所示出的声音播放系统中，如果Rx相对于左右声道耳机的阻抗Rl、Rr不可忽略，例如通过耳机转接线转接导致Rx增大，则在其中一个声道播放回路进行播放时，会在另一个声道的耳机上产生声音，从而降低了左右声道之间的隔离度。
为了提高左右声道之间的隔离度，本申请实施例提供一种音频播放电路。该音频播放电路可以包含电流通路，电流通路可以包含第一电流通路和第二电流通路。第一电流通路的一端可以与左声道电路的输出端耦接，第一电流通路的另一端可以与反馈通路2的输入端耦接。第二电流通路的一端可以与右声道电路的输出端耦接，第二电流通路的另一端可以与反馈通路1的输入端耦接。在左声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道播放回路接收到来自处理器的信号等于主板音源地时，利用该第一电流通路来调节反馈回右声道耳机的信号输入端的电压，可以使得在右声道播放回路未播放状态下右声道耳机两端的电压相等，减小左声道播放回路播放时对右声道耳机产生的电流影响。类似的，在右声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，利用该第二电流通路来改变反馈回左声道耳机的信号输入端的电压，可以使得在左声道播放回路未播放状态下左声道耳机两端的电压相等，减少右声道播放回播放时对左声道耳机产生的电流影响。可见，通过该电流通路，可以减小左右声道之间的串扰，提高左右声道之间的隔离度。
具体的，请参阅图4，图4是本申请实施例提供的一种声音播放系统的结构示意图。如图4所示，该声音播放系统中，对于左声道通路，音频芯片中的左声道电路、左声道耳机和主板音源地通过导线组成左声道播放回路。通过电压反馈电路1将阻抗Ry一端的电压V3反馈回左声道电路的输入端，该电压反馈电路1用于调整输入左声道耳机的电压，在左声道电路接收到来自处理器的信号为主板音源地信号时减小左声道耳机两端的电压差，来减小右声道播放回路对左声道播放回路的串扰。对于右声道通路，类似的，音频芯片中的右声道电路、右声道耳机和主板音源地通过导线组成右声道播放回路。通过电压反馈电路2将阻抗Ry一端的电压V3反馈回右声道电路的输入端，该电压反馈电路2用于调整输入右声道耳机的电压，在右声道电路接收到来自处理器的信号是主板音源地信号时减小右声道耳机两端的电压差，来减小左声道播放回路对右声道播放回路的串扰。可见，利用上述电压反馈电路1和电压反馈电路2可以提高左右声道之间的隔离度。
本申请实施例中，前后文中的电流通路1即为第一电流通路，电流通路2即为第二电流通路。前后文中的电压反馈电路1和反馈电路1即为第一反馈电路，电压反馈电路2和反馈电路2即为第二反馈电路。等效阻抗Rx即为第一等效阻抗，等效阻抗Ry为第二等效阻抗，等效阻抗Re为第三等效阻抗。
如图4所示，左声道电路的输出端耦接到左声道耳机的第一端，第一反馈电路的输 入端耦接到左声道耳机的第二端，第一反馈电路的输出端与左声道电路的输入端耦接。右声道电路的输出端耦接到右声道耳机的第一端，第二反馈电路的输入端用于耦接右声道耳机的第二端，第二反馈电路的输出端与右声道电路的输入端耦接。左声道耳机的第二端与右声道耳机的第二端耦接。
如图4所示，第一电流通路的第一端分别与左声道电路的输出端和左声道耳机的第一端耦接，第一电流通路的第二端分别与第二反馈电路的输入端和左声道耳机的第二端耦接。
第二电流通路的第一端分别与右声道电路的输出端和右声道耳机的第一端耦接，第二电流通路的第二端分别与第一反馈电路的输入端和右声道耳机的第二端耦接。
音频播放电路中各个模块的功能介绍如下：
左声道电路，用于输出左声道音频信号给左声道耳机的第一端。
右声道电路，用于输出右声道音频信号给右声道耳机的第一端。
第一反馈电路，用于当右声道电路在输出右声道音频信号时，通过左声道电路向左声道耳机的第一端反馈第一电压。
第二反馈电路，用于当左声道电路在输出左声道音频信号时，通过右声道电路向右声道耳机的第一端反馈第二电压。
第一电流通路，用于在左声道电路输出左声道音频信号时，分流左声道电路输出的电流，以调整向右声道耳机的第一端反馈的第二电压。在左声道电路输出左声道音频信号且右声道电路未输出右声道音频信号时，第二电压与右声道耳机的第二端的电压相等。
第二电流通路，用于在右声道电路输出右声道音频信号时，分流右声道电路输出的电流，以调整向左声道耳机的第一端反馈的第一电压。在右声道电路输出右声道音频信号且左声道电路未输出左声道音频信号时，第一电压与左声道耳机的第二端的电压相等。
下面结合图4具体介绍电流通路1和电流通路2的功能。
(1)在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号的场景下，电流通路2的功能
对于电流通路2来说，当右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，由于走线阻抗、磁珠阻抗或者耳机转接线的等效阻抗，右声道耳机和左声道耳机的共同接地点A的电压为V1，大于主板音源地电压V0。右声道电路通过电流通路2、主板音源地以及两者之间的走线形成电流回路，即图4中的回路1，来改变反馈回左声道播放通路的电压V3。回路1可以通过分流右声道电路上的电流来改变反馈回左声道播放通路的电压V3。电流通路2上的阻抗值可以确定反馈回左声道播放通路的电压V3。因此，可以通过设置电流通路2上的阻抗值来使反馈回左声道耳机的第一端的电压为V1。从而在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时左声道耳机的第一端和第二端电压均等于V1。进一步减小左声道耳机两端的电压差值，来减小右声道播放回路对左声道播放回路的串 扰。如图4所示，回路2是当右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，形成的右声道播放回路。
(2)在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号的场景下，电流通路1的功能
对于电流通路1来说，当左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，由于走线阻抗、磁珠阻抗或者耳机转接线的等效阻抗，左声道耳机和右声道耳机的共同接地点A的电压为V1，大于主板音源地电压V0。左声道电路通过电流通路1、主板音源地和两者之间的走线形成电流回路，来改变反馈回右声道播放通路的电压V3。电路通路1、阻抗Ry、Rx和主板音源地连接形成的回路可以通过分流左声道电路上的电流来改变反馈回右声道播放通路的电压V3。电流通路1上的阻抗值可以确定反馈回左声道播放通路的电压V3。因此，可以通过设置电流通路1上的阻抗值来使反馈回右声道耳机的第一端的电压为V1。从而在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时右声道耳机的第一端和第二端电压均等于V1。进一步减小右声道耳机两端的电压差值，来减小左声道播放回路对右声道播放回路的串扰。
该声音播放系统中，如图4所示，音频芯片中包含左声道电路、右声道电路电压反馈电路1和电压反馈电路2。音频芯片中左声道电路的输出端可以通过音频芯片的芯片接口7提供，电压反馈电路1的反馈输入端可以通过音频芯片的芯片接口8提供。右声道电路的输出端可以通过音频芯片的芯片接口10提供，反馈电路2的反馈输入端可以通过音频芯片的芯片接口9提供。
其中，电流通路1和电流通路2可以均设置在终端的主板上。该主板上可以设置芯片和器件。芯片例如可以包含音频芯片，器件例如可以包含组成电流通路的器件。如图4所示，电流通路1通过音频芯片的芯片接口7与左声道电路连接，并通过音频芯片的芯片接口8与电压反馈电路1连接。电流通路2通过音频芯片的芯片接口10与右声道电路连接，并通过音频芯片的芯片接口9与电压反馈电路2连接。可以通过终端上的耳机接口为立体声耳机提供接入音频芯片、电流通路和主板音源地的接口，该接入音频芯片的接口包含芯片接口7、芯片接口8、芯片接口9和芯片接口10。立体声耳机通过耳机插头接入终端上的耳机接口。立体声耳机的耳机插头上可以与终端上的耳机接口连接，从而将左声道通路与左声道耳机的输入端连接，将共同接地点A通过走线、磁珠等与主板音源地连接，将右声道通路与右声道耳机的输入端连接，并将共同接地点A通过走线、磁珠、反馈走线连接到电压反馈电路1和电压反馈电路2。
下面列出一种图4所示出的声音播放系统中左声道电路、右声道电路、电压反馈电路1、电压反馈电路2、电流通路1和电流通路2的具体实现示例。
本申请实施例中，音频芯片中左声道电路可以是运算放大器和阻抗实现，右声道电路可以是由运算放大器和阻抗实现。电压反馈电路1和电压反馈电路2也可以是由运算放大器和阻抗实现。电流通路1和电流通路2可以是由阻抗实现。具体的，请参阅图5，图5是本申请实施例提供的另一种声音播放系统的结构示意图。可以理解的，图5所示 出的左声道电路、右声道电路、电压反馈电路1、电压反馈电路2和电流通路的具体结构仅用于解释本申请实施例，还可以有其他结构或者变形，本申请实施例不作限定。
如图5所示，第一电流通路包含第一阻抗。第一阻抗的第一端分别与左声道电路的输出端和左声道耳机的第一端耦接，第一阻抗的第二端分别与第二反馈电路的输入端和左声道耳机的第二端耦接。第二电流通路包含第二阻抗。第二阻抗的第一端分别与右声道电路的输出端和右声道耳机的第一端耦接，第二阻抗的第二端分别与第一反馈电路的输入端和右声道耳机的第二端耦接。
如图5所示，关于左声道播放回路、右声道播放回路可以参考图1和图3中的左声道播放回路和右声道播放回路。关于电压反馈电路1和电压反馈电路2的具体描述可以参考图3中的反馈电路1和反馈电路2的具体描述，这里不再赘述。
下面分别结合具体场景介绍图5示例出的电流通路1和电流通路2的功能。
(a)电流通路2的功能
如图5所示，电流通路2可以利用阻抗Rrfb来实现，在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，由于走线阻抗、磁珠阻抗或者耳机转接线的等效阻抗，右声道耳机和左声道耳机的共同接地点的电压为V1。如图5所示，在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，在该声音播放系统中产生两个电流回路：回路1和回路2。其中，回路1是右声道电路、电流通路2和主板音源地连接形成的电流回路。回路2是右声道电路、右声道耳机和主板音源地连接形成的电流回路。回路1可以通过分流右声道电路上的电流来改变反馈回左声道播放通路的电压V3。电流通路2上的阻抗Rrfb的大小可以确定反馈回左声道播放通路的电压V3。因此，可以通过设置阻抗Rrfb来设置反馈回左声道电路的电压V3。进而通过设置阻抗Rrfb来使经过反馈电路1和左声道电路后该输送给左声道耳机的第一端电压和左声道耳机的第二端电压相等，均为V1。
具体的，图5所示的回路1和回路2的等效电路如图6所示。图6是本申请实施例提供的回路1和回路2的等效电路结构图。下面介绍怎样确定阻抗Rrfb的取值，来实现：当右声道播放回路播放状态，左声道通路未播放状态时，反馈回左声道耳机的第一端的电压值等于V1。
如图6所示，电流通路2中阻抗Rrfb和Ry之间的电压V3即为反馈回左声道播放通路的电压值，该电压经过运算放大器3和运算放大器1之后输入到左声道耳机的电压值等于共同接地点的电压值，为V1。如果运算放大器3和运算放大器1的放大倍数乘积为1/x1，则将V3调高，即：
V3＝x1*V1   (3)
设回路1流过的电流为I1，回路2流过的电流为I2，则对图6使用欧姆定律可得：
Figure PCTCN2019107555-appb-000010
根据公式(3)和公式(4)可得：
Figure PCTCN2019107555-appb-000011
当x1＝1时，根据公式(5)得到：
Figure PCTCN2019107555-appb-000012
根据公式(3)，在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，将电压V3＝x1*V1通过运算放大器3和运算放大器1反馈到左声道耳机的输入端。该电压V3经过运算放大器3和运算放大器1后，输入到左声道耳机的电压为V3/x1，即为V1。则左声道耳机的两端电压均为V1。从而在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时进一步减小左声道耳机两端的电压差值，来减小右声道播放回路对左声道播放回路的串扰。
(b)电流通路1的功能
与电流通路2类似，可以通过电流通路1分流左声道电路上的电流，来改变反馈回右声道播放通路的电压V3。电流通路1上的阻抗Rlfb的大小可以确定反馈回右声道播放通路的电压V3。因此，可以通过设置阻抗Rlfb来设置反馈回右声道电路的电压V3。进而通过设置阻抗Rlfb来使经过反馈电路2和右声道电路后输送给右声道耳机的第一端的电压和右声道耳机的第二端的电压相等，均为V1。
确定阻抗Rlfb的取值的方法可以类比确定阻抗Rrfb的方法。得到的阻抗Rlfb的取值可以实现：当左声道播放回路播放状态，右声道通路未播放状态时，反馈回右声道耳机的第一端的电压值等于V1，即等于右声道耳机的第二端的电压。
运算放大器4和运算放大器2的放大倍数乘积为1/x2，则可得：
Figure PCTCN2019107555-appb-000013
当x2＝1时，根据公式(7)得到：
Figure PCTCN2019107555-appb-000014
根据公式(8)，在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，将电压V3＝x2*V1通过运算放大器4和运算放大器2反馈到右声道耳机的输入端。该电压V3经过运算放大器4和运算放大器2后，输入到右声道耳机的电压为V3/x2，即为V1。则右声道耳机的两端电压均为V1。从而在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，且右声道电路接收到来自处理器的信号为主板音源地信号时进一步减小右声道耳机两端的电压差值，来减小左声道播放回路对右声道播放回路的串扰。
可见，通过Rrfb和Rlfb组成的电流通路，无需改变音频芯片的内部结构，利用音频芯片的芯片接口即可实现减小右声道播放回路与左声道播放回路之间的串扰，提高右声道播放回路和左声道播放回路之间的隔离度。
在另一种可能的实施例中，图5所示出的电流通路1和电流通路2也可以集成在音频芯片中。左声道电路通过音频芯片的芯片接口接入左声道耳机的输入端。右声道电路通过音频芯片的芯片接口接入右声道耳机的输入端。电流通路1和电流通路2通过音频芯片的芯片接口与Rx的另一端连接。
可以通过终端上的耳机接口为立体声耳机提供接入音频芯片、电流通路和主板音源地的接口。立体声耳机通过耳机插头接入终端上的耳机接口。
本申请实施例中，电流通路1中Rlfb即为第一阻抗，电流通路2中Rrfb即为第二 阻抗。如图5所示，第一阻抗的第一端与左声道电路的输出端耦接，第一阻抗的第二端与第二反馈电路的输入端耦接。第二阻抗的第一端与右声道电路的输出端耦接，第二阻抗的第二端与第一反馈电路的输入端耦接。
当右声道电路在输出右声道音频信号时，第一反馈电路向左声道耳机的第一端反馈的电压即为第一电压。在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，该第一电压V3/x1与左声道耳机的第二端的电压相等。当左声道电路在输出左声道音频信号时，第二反馈电路向右声道耳机的第一端反馈的电压即为第二电压。在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，该第二电压V3/x2与右声道耳机的第二端的电压相等。
在一种可能的实施方式中，电流通路可以直接从左声道电路的输出端跨接到右声道电路的输出端。请参阅图7，图7是本申请实施例提供的又一种声音播放系统的结构示意图。如图7所示，该声音播放系统中，对于左声道通路，音频芯片中的左声道电路、左声道耳机和主板音源地通过导线组成左声道播放回路。当右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，右声道电路通过电流通路3形成电流回路，即图7中的回路3，来改变反馈回左声道播放通路的电压。
在一种可能的实现方式中，如图7所示，电流通路3可以使用反馈阻抗Rfb实现。
电流通路3即第三电流通路，反馈阻抗Rfb即为第三阻抗。如图7所示，第三电流通路包含第三阻抗，第三阻抗的第一端分别与左声道电路的输出端和左声道耳机的第一端耦接，第三阻抗的第二端分别与右声道电路的输出端和右声道耳机的第一端耦接。
在一种可能的实施方式中，如图7所示，左声道电路可以包含通过走线连接的数模转换器3、运算放大器5、阻抗R11、R12和R13，右声道电路可以包含通过走线连接的数模转换器4、运算放大器6、阻抗R14、R15和R16。关于左声道电路和右声道电路的具体描述可以参考图1所描述的实施例中的相关描述，这里不再赘述。
可以理解的，本申请实施例以以下情况为例进行介绍：电流通路3利用反馈阻抗Rfb实现，左声道电路包含通过走线连接的数模转换器3、运算放大器5、阻抗R11、R12和R13，右声道电路包含通过走线连接的数模转换器4、运算放大器6、阻抗R14、R15和R16。但是上述图7所示出的电流通路3、左声道电路和右声道电路仅用于解释本申请实施例，电流通路3、左声道电路和右声道电路均可以有其他结构或者变形，本申请实施例不作限定。
本申请实施例中，电流通路3即为第三电流通路。等效阻抗Rx即为第一等效阻抗，等效阻抗Ry为第二等效阻抗，等效阻抗Re为第三等效阻抗。关于等效阻抗Rx、Ry和Re的描述可以参考图1和图3所描述实施例的具体介绍，这里不再赘述。
如图4所示，左声道电路的输出端用于耦接左声道耳机的第一端，右声道电路的输出端用于耦接右声道耳机的第一端，左声道耳机的第二端与右声道耳机的第二端耦接。音频播放电路中各个模块的功能介绍如下：
左声道电路，用于输出左声道音频信号给左声道耳机的第一端。
右声道电路，用于输出右声道音频信号给右声道耳机的第一端。
第三电流通路的第一端分别与左声道电路的输出端和左声道耳机的第一端耦接，第三电流通路的第二端分别与右声道电路的输出端和右声道耳机的第一端耦接。
第三电流通路，用于在左声道电路输出左声道音频信号时，分流左声道电路输出的电流，以调整输入右声道耳机的第一端的第三电压。在左声道电路在输出左声道音频信号且右声道电路在未输出右声道音频信号时，第三电压与右声道耳机的第二端的电压相等。
第三电流通路，还用于在右声道电路输出右声道音频信号时，分流右声道电路输出的电流，以调整输入左声道耳机的第一端的第四电压。在右声道电路输出右声道音频信号且左声道电路未输出左声道音频信号时，第四电压与左声道耳机的第二端的电压相等。
如图7所示，在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，在该声音播放系统中产生两个电流回路：回路3和回路4。
其中，回路3是右声道电路、电流通路3和等效接地阻抗通过走线形成的电流回路。如图7所示，等效接地阻抗可以包含左声道电路中的反馈阻抗R11和R13。另外，等效接地阻抗还可以包含用于检测耳机是否插入耳机接口的检测阻抗，等效接地阻抗还可以包含与电流通路3连接的其他接地阻抗。回路4是右声道电路、右声道耳机和主板音源地形成的电流回路。回路3可以在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时改变左声道耳机的输入端的电压，使得左声道耳机的输入端的电压值和共同接地点的电压相等，均为V1。从而减小左声道耳机两端的电压差值，减小右声道播放回路对左声道播放回路的串扰。
下面介绍怎样确定阻抗Rfb的取值，来实现：当右声道播放回路播放状态，左声道通路未播放状态时，反馈回左声道耳机的第一端的电压值等于V1。当左声道播放回路播放状态，右声道通路未播放状态时，反馈回右声道耳机的第一端的电压值等于V1。
具体的，图7所示的回路3和回路4的等效电路如图8所示。图8是本申请实施例提供的回路3和回路4的等效电路结构图。对图8使用欧姆定律可得：
Figure PCTCN2019107555-appb-000015
其中，Rb为等效接地阻抗，当等效接地阻抗仅包含左声道电路中的反馈阻抗时，如图7所示，Rb＝R11+R13。
根据公式(9)得：
Figure PCTCN2019107555-appb-000016
当右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，由公式(9)可得，左声道耳机两端的电压均为V1，此时可以减小左声道耳机两端的电压差值，减小右声道播放回路对左声道播放回路的串扰。
类似的，反馈阻抗Rfb还可以表示为：
Figure PCTCN2019107555-appb-000017
当左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，由公式(11)可得，右声道耳机两端的电压均为V1，此时可以减小右声道耳机两端的电压差值，减小左声道播放回路对右声道播放回路的串扰。
可选的，反馈阻抗Rfb还可以是由左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr同时确定的。左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr可以相等，则公式(10)和公式(11)相同。左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr也可以不同，则反馈阻抗Rfb还可以表示为：
Figure PCTCN2019107555-appb-000018
其中，Rc可以根据左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr确定，具体实现中，Rc可以是左声道耳机的等效阻抗Rl和右声道耳机的等效阻抗Rr的均值。
其中，电流通路3中Rfb即为第三阻抗。如图7所示，第三阻抗的第一端与左声道电路的输出端耦接，第三阻抗的第二端与右声道电路的输出端耦接。
在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，左声道耳机的第一端的电压即为第四电压V4。由欧姆定律可得，利用该第三电流通路，该第四电压V4与左声道耳机的第二端的电压V1相等。在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，右声道耳机的第一端的电压即为第三电压。由欧姆定律可得，该第三电压与右声道耳机的第二端的电压V1相等。
该声音播放系统中，如图7所示，音频芯片中包含左声道电路和右声道电路，音频芯片中左声道电路的输出端可以通过音频芯片的芯片接口11提供，右声道电路的输出端可以通过音频芯片的芯片接口12提供，在终端的主板上通过芯片接口11和芯片接口12来连接电流通路3。该声音播放系统无需改变音频芯片的内部结构，利用音频芯片的芯片接口即可实现减小左右声道播放回路之间的串扰，提高左右声道播放回路之间的隔离度。
请参阅图9，图9是本申请实施例提供的一种终端的结构示意图。该终端可以是图1所描述的终端10。如图9所示，该终端包含处理器901、音频播放电路902和耳机接口903，其中：
处理器901可以是一个或多个中央处理器(central processing unit，CPU)，在处理器901是一个CPU的情况下，该CPU可以是单核CPU，也可以是多核CPU。
处理器901与音频播放电路902的输入端耦接，处理器901用于向音频播放电路902输入音频信号。
音频播放电路902的输出端与所述耳机接口903耦接；
耳机接口903用于连接外部的立体声耳机，立体声耳机包括左声道耳机和右声道耳机。该耳机接口903可以是图1中的耳机接口102，该耳机接口可以是typeC耳机接口，也可以是3.5mm耳机接口。
其中，立体声耳机可以是图1中所描述的立体声耳机20。立体声耳机还可以是图3-图7中任一个所描述的立体声耳机。
音频播放电路902可以是前述实施例如图4或者图5所描述的音频播放电路。
在左声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道播放回路接收到来自处理器的信号等于主板音源地时，利用该第一电流通路来调节反馈回右声道耳机的信号输入端的电压，可以使得在右声道播放回路未播放状态下右声道耳机两端的电压相等，减小左声道播放回路播放时对右声道耳机产生的电流影响。类似的，在右声道播放回路接收到来自处理器的信号的电压绝对值大于主板音源地信号时，利用该第二电流通路来改变反馈回左声道耳机的信号输入端的电压，可以使得在左声道播放回路未播放状态下左声道耳机两端的电压相等，减少右声道播放回播放时对左声道耳机产生的电流影响。可见，通过该电流通路，可以减小左右声道之间的串扰，提高左右声道之间的隔离度。
音频播放电路902还可以是如图7实施例所描述的音频播放电路。
在右声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，左声道电路接收到来自处理器的信号为主板音源地信号时，左声道耳机的第一端的电压与左声道耳机的第二端的电压相等。在左声道电路接收到来自处理器的信号的电压绝对值大于主板音源地信号，右声道电路接收到来自处理器的信号为主板音源地信号时，右声道耳机的第一端的电压与右声道耳机的第二端的电压相等。
需要说明的，图9所示的终端仅仅是本申请实施例的一种实现方式，实际应用中，图9所示的终端还可以包括更多或更少的部件，这里不作限制。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何在本申请揭露的技术范围内的变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (12)

  1. 一种音频播放电路，其特征在于，所述音频播放电路包含左声道电路、右声道电路、第一反馈电路、第二反馈电路、第一电流通路和第二电流通路，其中：
    所述左声道电路的输出端用于耦接左声道耳机的第一端，所述第一反馈电路的输入端用于耦接所述左声道耳机的第二端，所述第一反馈电路的输出端与所述左声道电路的输入端耦接；
    所述右声道电路的输出端用于耦接右声道耳机的第一端，所述第二反馈电路的输入端用于耦接所述右声道耳机的第二端，所述第二反馈电路的输出端与所述右声道电路的输入端耦接；所述左声道耳机的第二端与所述右声道耳机的第二端耦接；
    所述第一电流通路的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第一电流通路的第二端分别与所述第二反馈电路的输入端和所述左声道耳机的第二端耦接；
    所述第二电流通路的第一端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接，所述第二电流通路的第二端分别与所述第一反馈电路的输入端和所述右声道耳机的第二端耦接；
    所述左声道电路，用于输出左声道音频信号给所述左声道耳机的第一端；
    所述右声道电路，用于输出右声道音频信号给所述右声道耳机的第一端；
    所述第一反馈电路，用于当所述右声道电路在输出右声道音频信号时，通过所述左声道电路向所述左声道耳机的第一端反馈第一电压；
    所述第二反馈电路，用于当所述左声道电路在输出左声道音频信号时，通过所述右声道电路向所述右声道耳机的第一端反馈第二电压；
    所述第一电流通路，用于在所述左声道电路输出左声道音频信号时，分流所述左声道电路输出的电流，以调整向所述右声道耳机的第一端反馈的所述第二电压；在所述左声道电路输出左声道音频信号且所述右声道电路未输出右声道音频信号时，所述第二电压与所述右声道耳机的第二端的电压相等；
    所述第二电流通路，用于在所述右声道电路输出右声道音频信号时，分流所述右声道电路输出的电流，以调整向所述左声道耳机的第一端反馈的所述第一电压；在所述右声道电路输出右声道音频信号且所述左声道电路未输出左声道音频信号时，所述第一电压与所述左声道耳机的第二端的电压相等。
  2. 根据权利要求1所述的电路，其特征在于，
    所述第一电流通路包含第一阻抗，所述第一阻抗的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第一阻抗的第二端分别与所述第二反馈电路的输入端和所述左声道耳机的第二端耦接；
    所述第二电流通路包含第二阻抗，所述第二阻抗的第一端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接，所述第二阻抗的第二端分别与所述第一反馈电路的输入端和所述右声道耳机的第二端耦接。
  3. 根据权利要求1或2所述的电路，其特征在于，
    所述左声道电路、所述右声道电路、所述第一反馈电路和所述第二反馈电路集成在音频芯片中；
    所述第一电流通路通过所述音频芯片的芯片接口分别与所述左声道电路的输出端和所述第二反馈电路的输入端耦接，所述左声道电路的输出端通过所述音频芯片的芯片接口与所述左声道耳机的第一端耦接，所述第一反馈电路的输入端通过所述音频芯片的芯片接口与所述左声道耳机的第二端耦接；
    所述第二电流通路通过所述音频芯片的芯片接口分别与所述右声道电路的输出端和所述第一反馈电路的输入端耦接，所述右声道电路的输出端通过所述音频芯片的芯片接口与所述右声道耳机的第一端耦接，所述第二反馈电路的输入端通过所述音频芯片的芯片接口与所述右声道耳机的第二端耦接。
  4. 根据权利要求1或2所述的电路，其特征在于，
    所述左声道电路、所述右声道电路、所述第一反馈电路、所述第二反馈电路、所述第一电流通路和所述第二电流通路集成在音频芯片中；
    所述左声道电路的输出端通过所述音频芯片的芯片接口与所述左声道耳机的第一端耦接，所述第一反馈电路的输入端通过所述音频芯片的芯片接口与所述左声道耳机的第二端耦接；
    所述右声道电路的输出端通过所述音频芯片的芯片接口与所述右声道耳机的第一端耦接，所述第二反馈电路的输入端通过所述音频芯片的芯片接口与所述右声道耳机的第二端耦接。
  5. 根据权利要求2至4任一项所述的电路，其特征在于，
    所述左声道电路的输出端通过耳机接口耦接到所述左声道耳机的第一端，所述右声道电路的输出端通过所述耳机接口耦接到所述右声道耳机的第一端；其中，所述耳机接口到立体声耳机之间产生的等效阻抗为第一等效阻抗Rx，所述立体声耳机包含所述左声道耳机和所述右声道耳机；
    所述第一反馈电路的输入端通过所述耳机接口耦接到所述左声道耳机的第二端，所述第二反馈电路的输入端通过所述耳机接口耦接到所述右声道耳机的第二端；其中，所述耳机接口到反馈电路之间产生的等效阻抗为第二等效阻抗Ry，所述反馈电路包含所述第一反馈电路和所述第二反馈电路；
    音源地通过所述耳机接口耦接到所述左声道耳机的第二端和所述右声道耳机的第二端；所述耳机接口耦接到所述音源地产生的等效阻抗为第三等效阻抗Re；所述音源地的电压为所述左声道电路或所述右声道电路在未输出音频信号状态下的参考电压。
  6. 根据权利要求5所述的电路，其特征在于，
    所述第一阻抗的阻值为：
    Figure PCTCN2019107555-appb-100001
    其中，Rrfb为所述第一阻抗的阻值，Rr为所述右声道耳机的等效阻抗，1/x1为所述左声道电路的放大倍数和所述第一反馈电路的放大倍数的乘积；
    所述第二阻抗的阻值为：
    Figure PCTCN2019107555-appb-100002
    其中，Rlfb为所述第二阻抗的阻值，Rl为所述左声道耳机的等效阻抗，1/x2为所述右声道电路的放大倍数和所述第二反馈电路的放大倍数的乘积。
  7. 一种音频播放电路，其特征在于，所述音频播放电路包含左声道电路、右声道电路和第三电流通路，其中：
    所述左声道电路的输出端用于耦接左声道耳机的第一端，所述右声道电路的输出端用于耦接右声道耳机的第一端，所述左声道耳机的第二端与所述右声道耳机的第二端耦接；
    所述左声道电路，用于输出左声道音频信号给所述左声道耳机的第一端；
    所述右声道电路，用于输出右声道音频信号给所述右声道耳机的第一端；
    所述第三电流通路的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第三电流通路的第二端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接；
    所述第三电流通路，用于在所述左声道电路输出左声道音频信号时，分流所述左声道电路输出的电流，以调整输入所述右声道耳机的第一端的第三电压；在所述左声道电路输出左声道音频信号且所述右声道电路未输出右声道音频信号时，所述第三电压与所述右声道耳机的第二端的电压相等；
    所述第三电流通路，还用于在所述右声道电路输出右声道音频信号时，分流所述右声道电路输出的电流，以调整输入所述左声道耳机的第一端的第四电压；在所述右声道电路输出右声道音频信号且所述左声道电路未输出左声道音频信号时，所述第四电压与所述左声道耳机的第二端的电压相等。
  8. 根据权利要求7所述的电路，其特征在于，
    所述第三电流通路包含第三阻抗，所述第三阻抗的第一端分别与所述左声道电路的输出端和所述左声道耳机的第一端耦接，所述第三阻抗的第二端分别与所述右声道电路的输出端和所述右声道耳机的第一端耦接。
  9. 根据权利要求8所述的电路，其特征在于，
    所述左声道电路的输出端通过耳机接口耦接到所述左声道耳机的第一端，所述右声道电路的输出端通过所述耳机接口耦接到所述右声道耳机的第一端；其中，所述耳机接口到立体声耳机之间产生的等效阻抗为第一等效阻抗Rx，所述立体声耳机包含所述左声道耳机和所述右声道耳机；
    音源地通过所述耳机接口耦接到所述左声道耳机的第二端、所述右声道耳机的第二端；所述耳机接口耦接到所述音源地产生的等效阻抗为第三等效阻抗Re；所述音源地的电压为所述左声道电路未输出左声道音频信号状态下所述左声道耳机的第一端的电压。
  10. 根据权利要求9所述的电路，其特征在于，所述第三阻抗的阻值为：
    Figure PCTCN2019107555-appb-100003
    或，
    Figure PCTCN2019107555-appb-100004
    其中，Rfb为所述第三阻抗的阻值，Rr为所述右声道耳机的等效阻抗，Rl为所述左声道耳机的等效阻抗，Rb为等效接地阻抗，所述第三电流通路通过所述等效接地阻抗与所述音源地耦接。
  11. 一种终端，其特征在于，所述终端包括处理器、音频播放电路和耳机接口，其中：
    所述处理器与所述音频播放电路的输入端耦接，所述音频播放电路的输出端与所述耳机接口耦接；
    所述处理器用于向所述音频播放电路输入音频信号；
    所述耳机接口用于连接外部的立体声耳机，所述立体声耳机包括左声道耳机和右声道耳机；
    所述音频播放电路是如权利要求1至6任一项所描述的音频播放电路。
  12. 一种终端，其特征在于，所述终端包括处理器、音频播放电路和耳机接口，其中：
    所述处理器与所述音频播放电路的输入端耦接，所述音频播放电路的输出端与所述耳机接口耦接；
    所述处理器，用于向所述音频播放电路输入音频信号；
    所述耳机接口用于连接外部的立体声耳机，所述立体声耳机包括左声道耳机和右声道耳机；
    所述音频播放电路是如权利要求7至10任一项所描述的音频播放电路。
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CN114143698B (zh) * 2021-10-29 2023-12-29 北京奇艺世纪科技有限公司 一种音频信号处理方法、装置及计算机可读存储介质

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