CN114584879A - Single-ended and differential output audio driving circuit and related POP sound removing method - Google Patents

Abstract

In the audio drive circuit with single-ended output, a negative input end of a first operational amplifier is respectively connected with a first end of a fourth resistor and a first input terminal through a first resistor, a positive input end of the first operational amplifier is respectively connected with a second input terminal through a second resistor and a third resistor, and an output end of the first operational amplifier is connected with a first node; the first node is connected with the second end of the fourth resistor through the first switch and connected with the second node through the third switch respectively; the second node is connected with the second end of the fourth resistor through a second switch and is grounded through a fifth resistor; the third switch comprises N switch units connected in parallel; each switch unit comprises a switch and a resistor which are connected in series, and N is an integer greater than or equal to 2. The POP sound generated in power-on and power-off of the circuit can be solved, the POP sound caused by the disorder of the operational amplifier can be solved, and the user experience is improved.

Description

Single-ended and differential output audio driving circuit and related POP sound removing method

Technical Field

The application relates to the technical field of removal of POP sound, in particular to a single-ended and differential output audio drive circuit and a method for removing related POP sound.

Background

With the popularization of mobile portable devices, on-chip integrated high performance audio headphone amplifiers are becoming popular, and headphone drivers are becoming more and more normalized to 16 ohms or 32 ohms. To ensure good sound quality requirements, it is desirable that the headphone driver amplifier should be free of other noise, such as POP, while having very low noise and harmonic distortion.

The POP sound is a burst sound generated by transient impact caused by various operations at the moment of power-on and power-off of an audio device and after power-on is stable. The POP sound has two main sources, one is that in the process of establishing a negative feedback loop of the operational amplifier, because the output signal is unstable, the signal jumps suddenly to bring impact, and the impact can be clearly captured by human ears at 1mV, which causes great influence on the hearing; the other is that after the negative feedback loop of the operational amplifier is established, the operational amplifier generates an offset voltage which is conducted directly to the output in a jump form, resulting in the generation of a POP tone.

In the related art, the POP sound can be eliminated by adopting a larger blocking capacitor on the circuit structure, but the required blocking capacitor is mostly an off-chip capacitor, and the integration of the circuit is not facilitated. Moreover, the method can be used for solving the POP sound existing in the power-on and power-off of the circuit, but can not solve the POP sound caused by the offset voltage generated by the operational amplifier. In practical use, POP sound generated by offset voltage of 1mV can be perceived by people, the offset of the operational amplifier easily exceeds 1mV under the condition of no calibration, and even if the operational amplifier can be calibrated, area resources, power consumption and subsequent test resources of a chip are wasted, the operation is complex, and ideal effects are difficult to achieve.

Disclosure of Invention

In view of the above, the present application is directed to overcoming the deficiencies of the prior art and providing a single-ended and differential-output audio driving circuit and a method for removing POP noise.

In order to achieve the purpose, the following technical scheme is adopted in the application:

a first aspect of the present application provides a single-ended output audio driving circuit, including: the circuit comprises a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first switch, a second switch and a third switch; the negative input end of the first operational amplifier is connected with the first end of the fourth resistor and the first input terminal through the first resistor, the positive input end of the first operational amplifier is connected with the second input terminal through the second resistor and the third resistor, and the output end of the first operational amplifier is connected with the first node; the first node is connected with the second end of the fourth resistor through the first switch and connected with the second node through the third switch respectively; the second node is connected with the second end of the fourth resistor through the second switch and grounded through the fifth resistor;

the third switch comprises N switch units connected in parallel; each switch unit comprises a switch and a resistor which are connected in series, and N is an integer greater than or equal to 2.

Optionally, impedances of resistors in the first switch unit to the nth switch unit in the N switch units are sequentially decreased from high to low.

A second aspect of the present application provides a method for removing a single-ended output POP tone, which is applied to a single-ended output audio driver circuit according to the first aspect of the present application, and the method includes:

in the process of electrifying the single-ended output audio output circuit, closing the first switch and starting the first operational amplifier at a first moment, sequentially closing the switches of N switch units in the third switch until all the switches are switched on from a second moment according to a first preset time interval, closing the second switch at a third moment, and opening the first switch at a fourth moment; wherein the fourth time is later than the third time, the third time is later than the second time, and the second time is later than the first time;

in the power-down process of the single-ended output audio output circuit, the first switch is closed at the fifth moment, the second switch is opened at the sixth moment, the switches of N switch units in the third switch are sequentially opened from the seventh moment until all the switches are opened according to a second preset time interval, and the first switch is opened and the first operational amplifier is closed at the eighth moment; the eighth time is later than the seventh time, the seventh time is later than the sixth time, and the sixth time is later than the fifth time.

Optionally, when impedances of resistors in the first to nth switch units of the N switch units decrease from high to low in sequence, sequentially closing the switches of the N switch units in the third switch until all the switches are turned on includes: sequentially closing the switches from the first switch unit to the Nth switch unit in the third switch until all the switches are conducted;

the sequentially disconnecting the switches of the N switch units in the third switch until all the switches are disconnected includes: and sequentially closing the switches from the Nth switch unit to the first switch unit in the third switch until all the switches are disconnected.

A third aspect of the present application provides a differentially output audio driver circuit comprising: the circuit comprises a first operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch and a ninth switch; a negative input end of the second operational amplifier is connected to the first end of the ninth resistor, and is connected to the third input terminal through the sixth resistor, a positive input end of the second operational amplifier is connected to the fourth input terminal through the seventh resistor, and is connected to the first end of the eleventh resistor through the eighth resistor, a first output end of the second operational amplifier is connected to the third node, a second output end of the second operational amplifier is connected to the fourth node, and the fourth node is connected to the second end of the eleventh resistor through the seventh switch, and is connected to the fifth node through the ninth switch; the third node is connected with the second end of the ninth resistor through the fourth switch and connected with a sixth node through the sixth switch respectively; the sixth node is connected with the second end of the ninth resistor through the fifth switch and connected with the fifth node through the tenth resistor respectively; a first end of the eighth switch is connected with the fifth node, and a second end of the eighth switch is connected with a second end of the eleventh resistor;

the sixth switch includes M switching circuits connected in parallel; each switch circuit comprises a switch and a resistor which are connected in series, and M is an integer greater than or equal to 2;

the ninth switch comprises K switch modules connected in parallel; each switch module comprises a switch and a resistor which are connected in series, and K is an integer greater than or equal to 2.

Optionally, impedances of resistors in the first to mth switch circuits in the M switch circuits are sequentially decreased from high to low.

Optionally, impedances of resistors in the first to K-th switch modules in the K switch modules sequentially decrease from high to low.

A fourth aspect of the present application provides a method for removing a differentially output POP sound, applied to a differentially output audio driver circuit according to the third aspect of the present application, the method including:

in the process of powering on the audio output circuit with differential output, the fourth switch and the seventh switch are closed at a ninth moment, the second operational amplifier is started, from a tenth moment, the switches of M switch circuits in the sixth switch are sequentially closed until all the switches are turned on according to a third preset time interval, meanwhile, the switches of K switch modules in the ninth switch are sequentially closed until all the switches are turned on, the fifth switch and the eighth switch are closed at an eleventh moment, and the fourth switch and the seventh switch are opened at a twelfth moment; wherein the twelfth time is later than the eleventh time, the eleventh time is later than the tenth time, and the tenth time is later than the ninth time;

in the power-down process of the audio output circuit with differential output, the fourth switch and the seventh switch are closed at a thirteenth moment, the fifth switch and the eighth switch are opened at a fourteenth moment, the switches of the M switch circuits in the sixth switch are sequentially opened from the fifteenth moment to all the switches are opened according to a fourth preset time interval, meanwhile, the switches of the K switch modules in the ninth switch are sequentially opened until all the switches are opened, the fourth switch and the seventh switch are opened at a sixteenth moment, and the second operational amplifier is closed; the sixteenth time is later than the fifteenth time, the fifteenth time is later than the fourteenth time, and the fourteenth time is later than the thirteenth time.

Optionally, when impedances of resistors from a first switch circuit to an mth switch circuit in the M switch circuits are sequentially decreased from high to low, sequentially closing the switches of the M switch circuits in the sixth switch until all the switches are turned on includes: sequentially closing the switches from the first switch circuit to the Nth switch circuit in the sixth switch until all the switches are conducted;

the sequentially disconnecting the switches of the M switch circuits in the sixth switch until all the switches are disconnected includes: and sequentially closing the switches from the Mth switch circuit to the first switch circuit in the sixth switch until all the switches are switched off.

Optionally, when impedances of resistors in first to K-th switch modules in the K switch modules decrease from high to low in sequence, sequentially closing switches of K switch modules in the ninth switch until all switches are turned on includes: sequentially closing the switches from the first switch module to the Kth switch module in the ninth switch until all the switches are conducted;

the sequentially disconnecting the switches of the K switch modules in the ninth switch until all the switches are disconnected includes: and sequentially closing the switches from the Kth switch module to the first switch module in the ninth switch until all the switches are disconnected.

The technical scheme provided by the application can comprise the following beneficial effects:

in the scheme of the application, a first switch, a second switch and a third switch are added to an audio output signal path of an audio driving circuit, so that an instant pulse signal generated in the power-on or power-off process can be resisted; the influence of offset voltage generated by the operational amplifier on POP sound can be eliminated by adopting N switch units connected in parallel; the on-resistances of the first switch, the second switch and the third switch are adjusted and arranged in the feedback loop, the nonlinearity of the third switch can be attenuated through the feedback loop, and the linearity of the single-ended output audio drive circuit is improved. Therefore, the POP sound existing in power-on and power-off of the circuit can be solved, the POP sound brought by offset voltage generated by the operational amplifier can be solved, the operation is simple, resources are saved, and the user experience is improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a circuit schematic diagram of a single-ended output audio driver circuit according to an embodiment of the present application.

Fig. 2 is a circuit diagram of a third switch according to another embodiment of the present disclosure.

Fig. 3 is a circuit diagram of an audio driver circuit with differential output according to another embodiment of the present application.

Fig. 4 is a schematic circuit diagram of a sixth switch according to another embodiment of the present application.

Fig. 5 is a circuit diagram of a ninth switch according to another embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail below. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall fall within the protection scope of the present application.

Fig. 1 is a schematic circuit diagram of a single-ended output audio driver circuit according to an embodiment of the present application. An embodiment of the present application provides a single-ended output audio driver circuit, and as shown in the figure, the single-ended output audio driver circuit may specifically include: the circuit comprises a first operational amplifier A1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first switch S1, a second switch S2 and a third switch S3.

The negative input terminal 1 of the first operational amplifier A1 is connected to the first terminal of the fourth resistor R4, and passes through the first resistor R1 and the first input terminal V_P1The positive input end 2 is connected with a second input terminal V through a second resistor R2_n1Connected to ground via a third resistor R3, an output terminal 3 connected to a first node V_XConnecting; first node V_XConnected to the second terminal of the fourth resistor R4 through the first switch S1 and the second node V through the third switch S3_YConnecting; second node V_YThe first end of the fourth resistor R4 is connected to ground through the fifth resistor R5 via the second switch S2.

As shown in fig. 2, the third switch S3 may include N switching cells connected in parallel; each of the switching units may include a switch and a resistor connected in series, and N is an integer of 2 or more.

In practice, the more switching units in the third switch S3, i.e., the larger N, the finer the jump step size, and the better the POP sound effect is removed.

In the scheme of this embodiment, by adding the first switch S1, the second switch S2, and the third switch S3 to the audio output signal path of the audio driver circuit, the transient pulse signal generated during power-on or power-off can be resisted; the influence of offset voltage generated by the operational amplifier on POP sound can be eliminated by adopting N switch units connected in parallel; the on-resistances of the first switch S1, the second switch S2 and the third switch S3 are adjusted and arranged in a feedback loop, so that the nonlinearity of the third switch S3 can be attenuated through the feedback loop, and the linearity of the single-ended output audio drive circuit is improved. Therefore, the POP sound existing in power-on and power-off of the circuit can be solved, the POP sound brought by offset voltage generated by the operational amplifier can be solved, the operation is simple, resources are saved, and the user experience is improved.

In practical applications, the fifth resistor R5 may be an equivalent resistor of a load earphone at the negative input of the first operational amplifier a1At the end, there is an offset voltage of the first operational amplifier A1, the first node V_XIs the output node of the first operational amplifier A1, the second node V_YIs the voltage node of the fifth resistor R5, i.e. the second node V when the fifth resistor R5 is a load earphone_YThe voltage fluctuation can be conducted to human ears through the earphone, so that the removal of the POP sound is to eliminate the second node V in the power-on or power-off process_YResulting in a voltage that can be heard by the human ear.

In some embodiments, the impedances of the resistors in the first to nth switch units of the N switch units are sequentially decreased from high to low.

In specific implementation, the impedances of the resistors in the first to the nth switch units of the N switch units of the third switch S3 are from high to low, for example, N is 4, and the impedances of the first to the fourth switch units of the third switch S3 are respectively Z₁、Z₂、Z₃And Z₄Then Z is₁＞Z₂＞Z₃＞Z₄. In this way, when the third switch S3 is closed or turned on, the on-resistance of the third switch S3 may be gradually changed, so as to better eliminate the influence of the offset voltage of the first operational amplifier a1 on the POP sound.

Preferably, the impedances of the resistors in the first to nth switch units of the N switch units may be sequentially decreased in a gradient manner from high to low. For example, N is 4, and impedances of the first to fourth switching units in the third switch S3 are Z₁、Z₂、Z₃And Z₄When Z is₁＝2Z₂＝4Z₃＝8Z₄。

The embodiment of the application provides a method for removing a single-ended output POP sound, which is applied to the single-ended output audio driver circuit described in any of the above embodiments, and the method for removing a single-ended output POP sound may specifically include two methods, which are respectively applied to the power-on process and the power-off process of the single-ended output audio driver circuit.

In the power-on process of the single-ended output audio output circuit, the first switch S1 is closed and the first operational amplifier a1 is turned on at a first time, from a second time, the switches of the N switch units in the third switch S3 are sequentially closed until all the switches are turned on at a first preset time interval, the second switch S2 is closed at a third time, and the first switch S1 is opened at a fourth time; the fourth time is later than the third time, the third time is later than the second time, and the second time is later than the first time.

In practice, with no input signal, i.e. first input terminal V_P1And a second input terminal V_n1The first switch S1, the second switch S2, and the third switch S3 are all turned off, and the first operational amplifier a1 is turned off, which is the first initial state. In the process of powering on the audio output circuit with single-ended output, the first switch S1 is first closed and the first operational amplifier a1 is opened at a first time, so that the first operational amplifier a1 becomes a negative feedback operation mode (closed loop), and then the first operational amplifier a1 starts to power on, in which case, the first operational amplifier a1 can stabilize the output voltage at the output common mode voltage after a set-up time under the inhibition of the negative feedback loop. Since the third switch S3 is in the open state at this time, the first operational amplifier A1 is at the first node V during setup_XThe generated offset voltage is not transmitted to the second node V_Y. After the first operational amplifier A1 is established, the first node V_XThe voltage is the offset voltage of the first operational amplifier a1, and then the switches of the N switch units in the third switch S3 are sequentially closed at the second moment until all the switches are turned on, so as to gradually turn on the first node V from high impedance to low impedance_XThe offset voltage is slowly conducted to the second node V like a step_Y. After the conduction is completed, the second switch S2 is closed at the third time in preparation for the conduction of the outer loop feedback, and finally the first switch S1 is opened at the fourth time so that the feedback loop passes through the third switch S3, the nonlinearity of the third switch S3 is attenuated by the feedback loop, and the switch contributing to the nonlinearity of the feedback loop is only the second switch S2. To this end, the second node V_YNo large voltage signal is generated during the power-on process, then the second node V_YWhere the generated voltage passes through the loaded earphone and the personAnd ear, no POP sound is generated.

The impedances of the resistors in the first switch unit to the Nth switch unit in the N switch units can be sequentially decreased from high to low.

When the switches of the N switch units in the third switch S3 are sequentially closed until all the switches are turned on, the switches of the N switch units may be sequentially closed at a first preset time interval to ensure stable conduction of the voltage.

Specifically, the first preset time interval may be set according to actual requirements, and is not limited herein.

In the power-down process of the audio output circuit, the first switch S1 is closed at the fifth moment, the second switch S2 is opened at the sixth moment, from the seventh moment, the switches of the N switch units in the third switch S3 are sequentially opened until all the switches are opened according to a second preset time interval, and the first switch S1 is opened at the eighth moment and the first operational amplifier a1 is closed; the eighth time is later than the seventh time, the seventh time is later than the sixth time, and the sixth time is later than the fifth time.

In practice, with no input signal, i.e. first input terminal V_P1And a second input terminal V_n1Is zero, the first switch S1 is open, the second switch S2 and the third switch S3 are closed, and the first operational amplifier a1 is turned on as a second initial state. During the power-down process of the audio output circuit with single-ended output, the first switch S1 is firstly closed, and then the second switch S2 is opened, at this time, the feedback loop established by the first operational amplifier a1 is taken over by the first switch, that is, the outer loop feedback is changed into the inner loop feedback. Then the switches of the N switch units in the third switch S3 are turned off in sequence until all the switches are turned off, and the first node V is connected_XAnd a second node V_YGradually becoming isolated. Finally, the first switch S1 is opened and the first operational amplifier a1 is turned off.

The impedances of the resistors in the first switch unit to the Nth switch unit in the N switch units can be sequentially decreased from high to low.

When the switches of the N switch units in the third switch S3 are sequentially turned off until all the switches are turned off, the switches of the N switch units may be sequentially turned off at a second preset time interval to ensure stable isolation of the voltage.

Specifically, the second preset time interval may be set according to actual requirements, and is not limited herein.

In some embodiments, when the impedances of the resistors in the first to nth switch units of the N switch units decrease sequentially from high to low, the switches of the N switch units of the third switch S3 are sequentially closed until all are turned on, which may be sequentially closing the switches of the first to nth switch units of the third switch S3 until all are turned on. Similarly, the switches of the N switch units in the third switch S3 may be sequentially opened until all are opened, and the switches from the nth switch unit to the first switch unit in the third switch S3 may be sequentially closed until all are opened.

An embodiment of the present application provides an audio driving circuit with differential output, as shown in fig. 3, the audio driving circuit with differential output may specifically include: a second operational amplifier a2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, and a ninth switch S9; wherein, the negative input terminal 4 of the second operational amplifier A2 is connected with the first terminal of the ninth resistor R9, passes through the sixth resistor R6 and the third input terminal V_P2The positive input end 5 is connected with the fourth input terminal V through a seventh resistor R7_n2The first end of the eleventh resistor R11 is connected through an eighth resistor R8, the first output end 6 is connected with a third node V1, the second output end 7 is connected with a fourth node V2, the fourth node V2 is connected with the second end of the eleventh resistor R11 through a seventh switch S7 and the fifth node V3 through a ninth switch S9, and the fifth node V3 is connected with the first end of an eighth switch S8; the third node V1 is connected to the second end of the ninth resistor R9 through the fourth switch S4, and connected to the sixth node V4 through the sixth switch S6; the sixth node V4 is connected to the second end of the ninth resistor R9 through the fifth switch S5, and connected to the fifth node V3 through the tenth resistor R10; eighth switch S8 thAnd the second end is connected to the second end of the eleventh resistor R11.

As shown in fig. 4, the sixth switch S6 includes M switch circuits connected in parallel; each of the switch circuits includes a switch and a resistor connected in series, and M is an integer of 2 or more.

As shown in fig. 5, the ninth switch S9 includes K switch modules connected in parallel; each switch module comprises a switch and a resistor which are connected in series, and K is an integer greater than or equal to 2.

In the scheme of this embodiment, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, and a ninth switch S9 are added to an audio output signal path of the audio driver circuit, so that a transient pulse signal generated in a power-on or power-off process can be resisted; the M switch circuits connected in parallel and the K switch modules connected in parallel are respectively used as a sixth switch S6 and a ninth switch S9, so that the influence of offset voltage generated by the operational amplifier on POP sound can be eliminated; the on-resistance of each switch is adjusted and arranged in a feedback loop, the nonlinearity of the sixth switch S6 and the ninth switch S9 can be attenuated through the feedback loop, and the linearity of the audio driving circuit with differential output is improved. Therefore, the POP sound existing in power-on and power-off of the circuit can be solved, the POP sound brought by offset voltage generated by the operational amplifier can be solved, the operation is simple, resources are saved, and the user experience is improved.

In practical applications, the tenth resistor may be an equivalent resistor of a load earphone, at the negative input terminal of the second operational amplifier a2, there is an offset voltage of the second operational amplifier a2, the differential nodes V1-V2 are output nodes of the second operational amplifier a2, and the differential nodes V3-V4 are voltage nodes of the tenth resistor, that is, when the tenth resistor is the load earphone, the voltage fluctuation of the differential nodes V3-V4 will be conducted to human ears through the earphone, so removing the POP sound is to eliminate the voltage that can be heard by human ears and is generated by the differential nodes V3-V4 during power-up or power-down.

In some embodiments, the impedances of the resistors in the first to mth switch circuits in the M switch circuits may be sequentially decreased from high to low.

In specific implementation, the impedances of the resistors in the first to mth switch circuits of the M switch circuits of the sixth switch S6 may decrease from high to low, for example, M is 6, and the impedances of the first to sixth switch circuits S6 in the sixth switch S6 are Z₁、Z₂、Z₃、Z₄、Z₅And Z₆Then Z is₁＞Z₂＞Z₃＞Z₄＞Z₅＞Z₆. In this way, when the sixth switch S6 is closed or turned on, the on-resistance of the sixth switch S6 may be gradually changed, so as to better cancel the influence of the offset voltage of the first operational amplifier a1 on the POP sound.

Preferably, the impedances of the resistors in the first switch circuit to the Mth switch circuit in the M switch circuits can be gradually decreased from high to low. For example, M is 6, and the impedances of the first to sixth switch S6 circuits in the sixth switch S6 are Z₁、Z₂、Z₃、Z₄、Z₅And Z₆When Z is₁＝2Z₂＝4Z₃＝8Z₄＝16Z₅＝32Z₆。

In some embodiments, the impedances of the resistors in the first to kth switch modules of the K switch modules may be sequentially decreased from high to low.

In specific implementation, the impedances of the resistors in the first to the kth switch modules of the K switch modules of the ninth switch S9 may decrease sequentially from high to low, for example, K is 7, and the impedances of the first to the seventh switch modules of the ninth switch S9 are Z₁、Z₂、Z₃、Z₄、Z₅、Z₆And Z₇Then Z is₁＞Z₂＞Z₃＞Z₄＞Z₅＞Z₆＞Z₇. In this way, when the ninth switch S9 is closed or turned on, the on-resistance of the ninth switch S9 may be gradually changed, so as to better cancel the influence of the offset voltage of the first operational amplifier a1 on the POP sound.

Preferably, the first of the K switch modulesThe impedance of the resistors from one switch module to the Kth switch module can be gradually decreased from high to low in a gradient manner. For example, K is 7, and impedances of the first to seventh switch modules in the ninth switch S9 are Z₁、Z₂、Z₃、Z₄、Z₅、Z₆And Z₇When Z is₁＝2Z₂＝4Z₃＝8Z₄＝16Z₅＝32Z₆＝64Z₇。

An embodiment of the present application provides a method for removing a differentially output POP sound, which is applied to the differentially output audio driver circuit according to any of the embodiments above, and the method for removing the differentially output POP sound may specifically include:

in the process of powering on the audio output circuit, the fourth switch S4 and the seventh switch S7 are closed at the ninth time, the second operational amplifier a2 is turned on, from the tenth time, the switches of the M switch circuits in the sixth switch S6 are sequentially closed until all switches are turned on, meanwhile, the switches of the K switch modules in the ninth switch S9 are sequentially closed until all switches are turned on, the fifth switch S5 and the eighth switch S8 are closed at the eleventh time, and the fourth switch S4 and the seventh switch S7 are opened at the twelfth time; the twelfth time is later than the eleventh time, the eleventh time is later than the tenth time, and the tenth time is later than the ninth time.

In practice, with no input signal, i.e. third input terminal V_P2And a fourth input terminal V_n2The fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, and the ninth switch S9 are all turned off, and the second operational amplifier a2 is turned off, thereby setting the state to the third initial state. In the process of powering on the audio output circuit with differential output, the fourth switch S4 and the seventh switch S7 are firstly closed and the second operational amplifier a2 is opened at the ninth time, so that the second operational amplifier a2 becomes a negative feedback operation mode (closed loop), and then the second operational amplifier a2 starts to power on, in this case, the second operational amplifier a2 can stabilize the output voltage at the output common mode voltage under the inhibition of the negative feedback loop for a certain set-up time. Since the sixth switch S6 and the ninth switch S9 areAt this time, the second operational amplifier A2 is in an off state, so the offset voltage generated at V1-V2 during the setup process is not transmitted to the differential nodes V3-V4.

After the second operational amplifier a2 is built, the voltage at the differential node V1-V2 is the offset voltage of the second operational amplifier a2, at this time, from the tenth time, the switches of the M switch circuits in the sixth switch S6 are sequentially closed until all switches are turned on, and at the same time, the switches of the K switch modules in the ninth switch S9 are sequentially closed until all switches are turned on, so as to gradually turn on the high impedance to the low impedance, and the offset voltage value at the differential node V1-V2 is slowly conducted to the second differential node V3-V4 as a step. After the conduction is completed, the fifth switch S5 and the eighth switch S8 are closed at the eleventh time to prepare for the conduction of the outer loop feedback, and finally the fourth switch S4 and the seventh switch S7 are opened at the twelfth time to make the feedback loop pass through the sixth switch S6 and the ninth switch S9, and the nonlinearity of the sixth switch S6 and the ninth switch S9 is attenuated by the feedback loop, and at this time, the switches contributing to the nonlinearity of the feedback loop are only the fifth switch S5 and the eighth switch S8. So far, the differential nodes V1-V2 do not generate large voltage signals in the power-on process, and the voltage generated at the differential nodes V3-V4 passes through a load earphone and human ears, and no POP sound is generated.

The impedances of the resistors from the first switch circuit to the Mth switch circuit in the M switch circuits can be sequentially decreased from high to low.

When the switches of the M switch circuits in the sixth switch S6 are sequentially closed until all the switches are turned on, the switches of the M switch circuits may be sequentially closed according to a third preset time interval to ensure stable conduction of the voltage.

Similarly, the impedances of the resistors in the first to kth switch modules of the K switch modules may decrease sequentially from high to low.

And when the switches of the K switch modules in the ninth switch S9 are sequentially turned on until all the switches are turned on, the switches of the K switch modules may be sequentially turned on according to a third preset time interval to ensure stable conduction of the voltage.

The third preset time interval may be set according to actual requirements, and is not limited herein.

In the power-down process of the audio output circuit, the fourth switch S4 and the seventh switch S7 are closed at a thirteenth time, the fifth switch S5 and the eighth switch S8 are opened at a fourteenth time, from the fifteenth time, the switches of the M switch circuits in the sixth switch S6 are sequentially opened until all the switches are opened, meanwhile, the switches of the K switch modules in the ninth switch S9 are sequentially opened until all the switches are opened, and at a sixteenth time, the fourth switch S4 and the seventh switch S7 are opened, and the second operational amplifier a2 is closed; the sixteenth time is later than the fifteenth time, the fifteenth time is later than the fourteenth time, and the fourteenth time is later than the thirteenth time.

In practice, with no input signal, i.e. third input terminal V_P2And a fourth input terminal V_n2Is zero, the fourth switch S4 and the seventh switch S7 are open, the fifth switch S5, the sixth switch S6, the eighth switch S8, and the ninth switch S9 are closed, and the second operational amplifier a2 is opened as a fourth initial state. In the power-down process of the audio output circuit with differential output, the fourth switch S4 and the seventh switch S7 are firstly closed at the thirteenth time, and then the fifth switch S5 and the eighth switch S8 are opened at the fourteenth time, at this time, the feedback loop established by the second operational amplifier a2 is taken over by the fourth switch S4 and the seventh switch S7, that is, the outer loop feedback is changed into the inner loop feedback. From the fifteenth time, the switches of the M switch circuits in the sixth switch S6 are sequentially turned off until all are turned off, and the switches of the K switch modules in the ninth switch S9 are sequentially turned off until all are turned off, so as to gradually isolate the differential nodes V1-V2 and the differential nodes V3-V4. Finally, the fourth switch S4 and the seventh switch S7 are turned off and the second operational amplifier a2 is turned off at the sixteenth time.

The impedances of the resistors from the first switch circuit to the Mth switch circuit in the M switch circuits can be sequentially decreased from high to low.

When the switches of the M switch circuits in the sixth switch S6 are turned off in sequence until all the switches are turned off, the switches of the M switch circuits may be turned off in sequence at a fourth preset time interval to ensure stable voltage isolation.

Similarly, the impedances of the resistors in the first to kth switch modules of the K switch modules may decrease sequentially from high to low.

When the switches of the K switch modules in the ninth switch S9 are sequentially turned off until all the switches are turned off, the switches of the K switch modules may be sequentially turned off at a fourth preset time interval to ensure stable isolation of the voltage.

The fourth preset time interval may be set according to actual requirements, and is not limited herein.

In some embodiments, when the impedances of the resistors in the first to mth switch circuits of the M switch circuits decrease sequentially from high to low, the switches of the M switch circuits of the sixth switch S6 are sequentially closed until all are turned on, which may be that the switches of the first to nth switch circuits of the sixth switch S6 are sequentially closed until all are turned on. Similarly, the switches of the M switch circuits in the sixth switch S6 may be sequentially opened until all are opened, and the switches from the mth switch circuit to the first switch circuit in the sixth switch S6 may be sequentially closed until all are opened.

Correspondingly, when the impedances of the resistors in the first to K-th switch modules in the K switch modules decrease from high to low in sequence, the switches of the K switch modules in the ninth switch S9 are sequentially closed until all the switches are turned on, which may be that the switches of the first to K-th switch modules in the ninth switch S9 are sequentially closed until all the switches are turned on. The switches of the K switch modules in the ninth switch S9 may be sequentially opened until all switches are opened, or the switches from the K switch module to the first switch module in the ninth switch S9 may be sequentially closed until all switches are opened.

It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments.

It should be noted that, in the description of the present application, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Further, in the description of the present application, the meaning of "a plurality" means at least two unless otherwise specified.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and the scope of the preferred embodiments of the present application includes other implementations in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.

It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.

In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.

In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.

Claims (10)

1. A single-ended output audio driver circuit, comprising: the circuit comprises a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first switch, a second switch and a third switch; the negative input end of the first operational amplifier is connected with the first end of the fourth resistor and the first input terminal through the first resistor, the positive input end of the first operational amplifier is connected with the second input terminal through the second resistor and the third resistor, and the output end of the first operational amplifier is connected with the first node; the first node is connected with the second end of the fourth resistor through the first switch and connected with the second node through the third switch respectively; the second node is connected with the second end of the fourth resistor through the second switch and grounded through the fifth resistor;

the third switch comprises N switch units connected in parallel; each switch unit comprises a switch and a resistor which are connected in series, and N is an integer greater than or equal to 2.

2. The single-ended output audio driver circuit according to claim 1, wherein the impedances of the resistors in the first through nth switch units of the N switch units decrease sequentially from high to low.

3. A method for removing POP tone of single-ended output, applied to the audio driver circuit of single-ended output according to claim 1 or 2, the method comprising:

in the process of powering on the single-ended output audio output circuit, the first switch is closed and the first operational amplifier is started at a first moment, from a second moment, the switches of the N switch units in the third switch are sequentially closed until all the switches are turned on according to a first preset time interval, the second switch is closed at a third moment, and the first switch is opened at a fourth moment; wherein the fourth time is later than the third time, the third time is later than the second time, and the second time is later than the first time;

in the power-down process of the single-ended output audio output circuit, the first switch is closed at the fifth moment, the second switch is opened at the sixth moment, the switches of N switch units in the third switch are sequentially opened from the seventh moment until all the switches are opened according to a second preset time interval, and the first switch is opened and the first operational amplifier is closed at the eighth moment; the eighth time is later than the seventh time, the seventh time is later than the sixth time, and the sixth time is later than the fifth time.

4. The method for removing the single-ended output POP tone according to claim 3, wherein when the impedances of the resistors in the first to Nth switch units in the N switch units decrease from high to low in sequence, the sequentially closing the switches of the N switch units in the third switch until all the switches are turned on comprises: sequentially closing the switches from the first switch unit to the Nth switch unit in the third switch until all the switches are conducted;

the sequentially disconnecting the switches of the N switch units in the third switch until all the switches are disconnected includes: and sequentially closing the switches from the Nth switch unit to the first switch unit in the third switch until all the switches are disconnected.

5. A differentially output audio driver circuit, comprising: the circuit comprises a first operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch and a ninth switch; a negative input end of the second operational amplifier is connected to the first end of the ninth resistor, and is connected to the third input terminal through the sixth resistor, a positive input end of the second operational amplifier is connected to the fourth input terminal through the seventh resistor, and is connected to the first end of the eleventh resistor through the eighth resistor, a first output end of the second operational amplifier is connected to the third node, a second output end of the second operational amplifier is connected to the fourth node, and the fourth node is connected to the second end of the eleventh resistor through the seventh switch, and is connected to the fifth node through the ninth switch; the third node is connected with the second end of the ninth resistor through the fourth switch and connected with a sixth node through the sixth switch respectively; the sixth node is connected with the second end of the ninth resistor through the fifth switch and connected with the fifth node through the tenth resistor respectively; a first end of the eighth switch is connected with the fifth node, and a second end of the eighth switch is connected with a second end of the eleventh resistor;

the sixth switch includes M switching circuits connected in parallel; each switch circuit comprises a switch and a resistor which are connected in series, and M is an integer greater than or equal to 2;

the ninth switch comprises K switch modules connected in parallel; each switch module comprises a switch and a resistor which are connected in series, and K is an integer greater than or equal to 2.

6. The differential-output audio driver circuit according to claim 5, wherein the impedances of the resistors in the first to Mth of the M switch circuits are sequentially decreased from high to low.

7. The differential-output audio driving circuit according to claim 5, wherein the impedances of the resistors in the first to Kth of the K switch modules are sequentially decreased from high to low.

8. A method for removing POP sound of differential output, which is applied to the audio driving circuit of differential output according to any one of claims 5-7, and comprises the following steps:

in the process of powering on the audio output circuit with differential output, the fourth switch and the seventh switch are closed at a ninth moment, the second operational amplifier is started, from a tenth moment, the switches of M switch circuits in the sixth switch are sequentially closed until all the switches are turned on according to a third preset time interval, meanwhile, the switches of K switch modules in the ninth switch are sequentially closed until all the switches are turned on, the fifth switch and the eighth switch are closed at an eleventh moment, and the fourth switch and the seventh switch are opened at a twelfth moment; wherein the twelfth time is later than the eleventh time, the eleventh time is later than the tenth time, and the tenth time is later than the ninth time;

in the power-down process of the audio output circuit with differential output, the fourth switch and the seventh switch are closed at a thirteenth moment, the fifth switch and the eighth switch are opened at a fourteenth moment, the switches of the M switch circuits in the sixth switch are sequentially opened from the fifteenth moment to all the switches are opened according to a fourth preset time interval, meanwhile, the switches of the K switch modules in the ninth switch are sequentially opened until all the switches are opened, the fourth switch and the seventh switch are opened at a sixteenth moment, and the second operational amplifier is closed; the sixteenth time is later than the fifteenth time, the fifteenth time is later than the fourteenth time, and the fourteenth time is later than the thirteenth time.

9. The method for removing the differentially output POP sound according to claim 8, wherein the sequentially closing the switches of the M switch circuits of the sixth switch until all of the switches are turned on when the impedances of the resistors in the first to M switch circuits of the M switch circuits sequentially decrease from high to low includes: sequentially closing the switches from the first switch circuit to the Nth switch circuit in the sixth switch until all the switches are conducted;

the sequentially disconnecting the switches of the M switch circuits in the sixth switch until all the switches are disconnected includes: and sequentially closing the switches from the Mth switch circuit to the first switch circuit in the sixth switch until all the switches are switched off.

10. The method for removing the differentially output POP sound according to claim 8, wherein the sequentially closing the switches of the K switch modules in the ninth switch until all the switches are turned on when the impedances of the resistors in the first to K switch modules decrease sequentially from high to low comprises: sequentially closing the switches from the first switch module to the Kth switch module in the ninth switch until all the switches are conducted;

the sequentially disconnecting the switches of the K switch modules in the ninth switch until all the switches are disconnected includes: and sequentially closing the switches from the Kth switch module to the first switch module in the ninth switch until all the switches are disconnected.

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