KR101887322B1 - Audio processing circuit for eliminating plug-in and plug-out noise of earphone, and line control earphone - Google Patents

Audio processing circuit for eliminating plug-in and plug-out noise of earphone, and line control earphone Download PDF

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Publication number
KR101887322B1
KR101887322B1 KR1020177014750A KR20177014750A KR101887322B1 KR 101887322 B1 KR101887322 B1 KR 101887322B1 KR 1020177014750 A KR1020177014750 A KR 1020177014750A KR 20177014750 A KR20177014750 A KR 20177014750A KR 101887322 B1 KR101887322 B1 KR 101887322B1
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South Korea
Prior art keywords
earphone
audio
switch element
plug
circuit
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KR1020177014750A
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Korean (ko)
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KR20170080638A (en
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웨이궈 리
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칭다오 고어텍 테크놀로지 컴파니 리미티드
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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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • H04R1/1041—Mechanical or electronic switches, or control elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
    • 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
    • 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
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Headphones And Earphones (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Noise Elimination (AREA)

Abstract

According to the present invention, there is provided an audio processing circuit and a line control earphone for eliminating earphone plug in / out noise, wherein each of the audio transmission lines for transmitting the left channel audio signal and the right channel audio signal in the earphone has one noise suppression circuit And the noise suppressing circuit is provided with a isolating capacitor and a switch element; One end of the isolation capacitor is connected to the audio transmission circuit and the other end is connected to the switch element; Before and after the earphone plug-in / out, the switch element is turned off. In the earphone plug-in / out process, an applied direct current voltage is transmitted to the switch element through the isolation capacitor, the switch element is turned on, Is grounded through the switch path of the switch element and further cuts off the noise output. The circuit design structure of the present invention is simple and low in cost, can thoroughly eliminate the earphone plug-in / out noise, and can be applied to the circuit design of all current four-line line control earphones.

Description

AUDIO PROCESSING CIRCUIT FOR ELIMINATING PLUG-IN AND PLUG-OUT NOISE OF EARPHONE, AND LINE CONTROL EARPHONE FOR AUDIO PROCESSING CIRCUIT AND LINE CONTROL EARPHONE FOR EARPHONE PLUG IN /

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earphone circuit technology, and more particularly, to an audio processing circuit for eliminating noise generated in an earphone plug-in / out process and a line control earphone using the audio processing circuit design.

Conventional line control earphones are generally classified into three-piece earphones and four-piece earphones. Earphone plugs of line control earphones with a microphone (for example, line control earphones incorporated in mobile phones) And is defined as a left channel terminal L, a right channel terminal R, a microphone terminal MIC, and a ground terminal GND sequentially from the outside to the inside of the earphone plug, as shown in FIG. When the four-line line control earphone is inserted into the host, for example, when the plug is plugged into the earphone insertion hole of the mobile phone, since the level up circuit is provided in the circuit connecting the mobile phone side and the microphone terminal MIC of the earphone plug, When plugging in / out the earphone plug into the audio socket of the mobile phone, since the microphone terminal MIC of the earphone plug is connected to the DC power supply through the up resistor or directly connected to the DC power supply to provide the DC bias voltage for the microphone signal, Since the left channel terminal L and the right channel terminal R of the earphone plug sequentially pass and touch the level ascending circuit in the plug-in / out process, a direct current voltage is suddenly applied on the left and right channels of the earphone, , Which allows the user to "squeak" when plugging in / A cause to hear the sound.

In order to solve the problem of generating noise when plugging in / out a line control earphone of the prior art into a host audio socket, the present invention provides an audio processing circuit for eliminating earphone plug in / out noise, So that the overall sound quality of the earphone can be improved.

The technical solution of the present invention for achieving the above object is as follows.

An audio processing circuit for eliminating an earphone plug in / out noise, wherein one noise suppressing circuit is connected to the audio transmission line for transmitting the left channel audio signal and the right channel audio signal from the earphone, A capacitor and a switch element are provided; One end of the isolation capacitor is connected to the audio transmission circuit and the other end is connected to the switch element; Before and after the earphone plug-in / out, the switch element is turned off. In the earphone plug-in / out process, an applied direct current voltage is transmitted to the switch element through the isolation capacitor, the switch element is turned on, Is grounded through the switch path of the switch element.

Furthermore, the isolation capacitor is connected to the control electrode of the switch element through one series-connected current limiting resistor, and the control electrode of the switch element is grounded through one discharge resistor; The resistance value of the current limiting resistor and the discharging resistance satisfies that a voltage drop formed at both ends of the discharging resistor after the swinging DC voltage passes through the isolation capacitor and the current limiting resistor turns on the switching element.

Preferably, the resistance value of the current limiting resistor is 1 K? Or less; The resistance value of the discharge resistor is 10K? Or more.

Preferably, the switch element is an NPN triode, the base of the triode is connected to the current limiting resistor, the collector is connected to the audio transmission line, and the emitter is grounded.

In order to effectively remove the plug-in / out noise and ensure that the left and right channel audio signals are normally transmitted, the following parameter value selection principle must be followed when selecting the isolated capacitor:

When the audio signal in the normal frequency range is transmitted through the isolation capacitor to the control electrode of the switch element, the current applied to the control electrode is made to be smaller than the minimum ON-state voltage of the switch element, , So that it can not be turned on when the right channel audio signal is normally transmitted.

Furthermore, it is preferable that the isolation capacitor use a pico-class-class capacitor, a ceramic capacitor of several tens pico-paras is most preferable; The normal frequency range of the audio signal is typically between 20 Hz and 20 KHz, and the capacitor value of the isolating capacitor can be determined comprehensively by the frequency range, the ON voltage and the current of the switching device.

In order to improve the interference resistance capability of the earphone and ensure the quality of the audio signal, one resistance-capacitance filtering circuit is also connected to each of the audio transmission lines transmitting the left channel audio signal and the right channel audio signal; The microphone transmission line to which the microphone terminal of the earphone is connected is connected to a pi -type filtering circuit composed of a capacitor and an inductor.

Preferably, the audio processing circuit is installed in a line controller of an earphone, the line controller is provided with a plurality of function buttons, the different function buttons are connected in series with voltage dividing resistors having different resistance values, And is connected between the microphone terminal and the ground, and the function button is a mechanical button having no self-locking function.

Further, the earphone can be designed as a dual-plug line control earphone, wherein one audio socket can be added to the line controller, and the audio socket has a left channel pin, a right channel pin, A pin is provided; The left channel pin is connected to the left channel audio output of the line controller and the left channel audio output is connected to the left channel speaker through a cable; The right channel pin is connected to the right channel audio output of the line controller and the right channel audio output is connected to the right channel speaker via a cable; The microphone pin is connected to a microphone laid on a line controller or to a microphone signal input terminal of a line controller, and the microphone signal input is connected to a microphone through a cable; The ground pin is grounded through a single button having a self-locking function, and when the button is pressed, audio signals can be played through two earphones.

The present invention also provides a line control earphone using the above-mentioned audio processing circuit design based on the structure design of the audio processing circuit for eliminating the earphone plug in / out noise. In the earphone, the left channel audio signal and the right channel audio Wherein one noise suppressing circuit is connected to each of the audio transmission lines for transmitting signals, and the noise suppressing circuit is provided with a isolating capacitor and a switch element; One end of the isolation capacitor is connected to the audio transmission circuit and the other end is connected to the switch element; Wherein the audio transmission line is supplied with a DC voltage that is turned on during an earphone plug in / out process, the swirling DC voltage is transmitted to the switch device through the isolation capacitor, and the operation of the switch device is controlled, The output of the noise is cut off by making the potential close to zero, that is, the level of 0.

The advantages and advantageous effects of the present invention over the prior art are that the noise suppression circuit is added to the left and right channel audio transmission lines of the earphone to reduce the potential of the left and right channel audio transmission lines during the earphone plug- To prevent the earphone speaker from being output through the earphone speaker by blocking the DC voltage applied to the audio transmission line during the earphone plug-in / out process and further to effectively remove the plug-in / out noise generated due to the output of the DC voltage Improve use experience of earphone user. In addition, by designing the isolating capacitor in the noise suppressing circuit, on the basis of effectively suppressing the plug-in / out noise, excessive electricity consumption on the host side connected to the earphone is prevented from being consumed to ensure normal use of the host. The circuit design structure of the present invention is simple and low in cost, and can be widely used in the circuit design of all four-level line control earphones now, and the earphone plug-in / out noise is thoroughly removed and the overall cost of the earphone is remarkably improved Do not.

Other features and advantages of the present invention will become more apparent from the detailed description of the embodiments of the present invention with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention, It is not. In the figure,
1 is a general structural view of one embodiment of a four-piece line control earphone.
2 is a circuit principle diagram of one embodiment of an audio processing circuit for eliminating earphone plug in / out noise provided by the present invention;
Fig. 3 is a circuit principle diagram of one embodiment in which the audio processing circuit shown in Fig. 2 is applied to a dual plug line control earphone; Fig.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the objects, techniques and advantages of the present invention, reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

In the current line control earphone, especially the 4-line line control earphone, during the plug-in / out process of the earphone, the left and right channel terminals of the earphone are connected to the earphone plug of the host's earphone socket. Thus, the DC voltage is suddenly applied to the left and right channel audio transmission lines of the earphone, and noise is generated and outputted through the speaker of the earphone, thereby affecting the user's use experience. In order to eliminate the noise generated during the plug-in / out process of the earphone, in this embodiment, a noise suppression circuit is designed and connected to an audio transmission line for transmitting the left channel audio signal and the right channel audio signal from the earphone, respectively, The DC voltage applied to the audio transmission line is removed, and noise is further removed.

The noise suppression circuit of the present embodiment is provided with a isolating capacitor and a switch element. In the earphone plug-in / out process, the DC voltage applied to the left and right channel audio transmission lines suddenly is transmitted to the subsequent switch element through the isolation capacitor, The switching element is operated so that the switching element can operate correctly when a direct current voltage is suddenly applied to the audio loss lines of the left and right channels and further the direct current voltage is transmitted to the ground, Channel speaker and the right channel speaker, so that the user can not hear the noise.

A specific circuit structure of the noise suppression circuit of this embodiment will be described in detail with the following four-line line control earphone as an example.

1, the four-stage line control earphone of this embodiment mainly includes an earphone plug 1, a line controller 2, a left channel speaker 3 and a right channel speaker 4. Here, the earphone plug 1 is for insertion and connection into an audio socket of a host (for example, a mobile phone or the like). The earphone plug 1 receives left and right channel audio signals output from the host and transmits them to the line controller 2 via a cable And transmits them to the left channel speaker 3 and the right channel speaker 4 through the line controller 2, respectively, and further realizes the play output of the left and right channel audio signals.

In the present embodiment, the earphone plug 1 is divided into four stages, and is defined as a left channel terminal L, a right channel terminal R, a microphone terminal MIC, and a ground terminal GND sequentially from the outside to the inside. A group of the noise suppression circuit is added to the audio transmission line connected to the left channel terminal L to remove the DC voltage applied to the left channel audio transmission line in the earphone plug-in / out process. In addition, a group of the noise suppression circuit is added to the audio transmission line connected to the right channel terminal R to remove the DC voltage applied to the right channel audio transmission line in the earphone plug-in / out process. Thereby, when the user plugs in the earphone or plugs out of the earphone socket on the host, no further "squeaky" noise is heard.

More specifically, one end of the isolation capacitor is connected to the audio transmission line of the left channel or the right channel, and the other end is connected to the control electrode of the switch element. A switch path of the switch element is connected between the audio transmission line and the ground, and when the switch element is turned on, the potential of the audio transmission line is lowered, that is, close to 0 V, .

In order to improve the reliability of the operation of the noise suppression circuit, in the present embodiment, the noise suppression circuit is also provided with a current limiting resistor and a discharging resistor, which can be connected between the isolation capacitor and the control electrode of the switching element , The discharge resistance can be connected between the control electrode of the switch element and the ground, thereby realizing safe on / off control for the switch element.

2, in this embodiment, the noise suppressing circuit of the first group is constituted by using the isolation capacitor C1, the current limiting resistor R10, the discharging resistor R3, and the switching element Q1 to generate the audio for the left channel audio signal transmission Connect to the transmission line. The noise suppressing circuit of the second group is constituted by using the isolation capacitor C3, the current limiting resistor R11, the discharging resistor R5 and the switching element Q2, and is connected to the audio transmission line for transmission of the right channel audio signal. Hereinafter, the first group noise suppression circuit will be described as an example. In the present embodiment, the switching element Q1 may be an electronic device such as a triode, a MOS tube, or a silicon controlled rectifier. In this embodiment, an NPN triode is described as an example. As shown in Fig. 2, the base of the NPN triode Q1 is connected to the divider node of the voltage divider circuit, the emitter is grounded, and the collector is connected to the audio transmission line.

The resistance values of the current limiting resistor R10 and the discharging resistor R3 are configured by the magnitude of the DC voltage applied to the audio transmission line during the plug-in / out process of the earphone, and the DC voltage is applied to the isolation capacitor C1 and the current limiting resistor R10 The voltage drop across both ends of the discharging resistor R3 after passing is set to be larger than the ON voltage of the NPN triode T1. For example, it is preferable to set the voltage drop to be greater than 0.7V, preferably to the collector voltage of the triode T1 And the saturation-ON of the NPN-type triode tube Q1 is controlled so that the DC voltage is grounded to prevent the noise from being output through the left channel speaker 3.

In the present embodiment, it is preferable that the triode electrodes Q1 and Q2 are triode electrodes whose on impedance is relatively low.

In this embodiment, when designing the noise suppression circuit, in selecting the parameter values of the isolation capacitors C1 and C3, the magnitude of the DC voltage applied to the left and right channel audio transmission lines during the earphone plug-in / The frequency of the left and right channel audio signals should be considered. In order to allow normal left and right channel audio signals to be outputted normally through the earphone speakers 3 and 4, a parameter value selection principle to be followed when selecting the isolating capacitors C1 and C3 in this embodiment is that audio in a normal range When the signal is transmitted to the control electrode of the switching elements Q1 and Q2 through the isolation capacitors C1 and C3, the current magnitude applied to the control electrode is smaller than the minimum ON current of the switching elements Q1 and Q2, , And Q2 are erroneously turned on to block the normally transmitted left and right channel audio signals.

The selection of the parameter values of the isolation capacitors C1 and C3 will be described below by way of example, assuming that the normal frequency range of the audio signal is between 20Hz and 20KHz (determined by the hearing range of the human ear).

The capacitance reactance formula of the capacitor XC = 1 / (2? FC) = 1 / (2 * 3.1415 * f * C)

When the capacitance C = 100 pF of the isolated capacitor and the frequency f = 20 KHz of the audio signal,

XC = 1 / (2 * 3.1415 * 20 * 103 * 1 * 10 - 10) = 79580?

It is possible to ensure that the switch elements Q1 and Q2 are not turned on by satisfying f = 20Khz, that is, the switch elements Q1 and Q2 can be assured only when the frequency is 20 KHz, Q2 is not turned on within the full audio range (20 Hz to 20 KHz), ensuring that Q2 does not affect the output of the normal audio signal.

The resistance values of the current limiting resistors R10 / R11 and the discharging resistors R3 / R5 are configured by combining the minimum ON currents of the switching elements Q1 and Q2. An audio signal having a frequency of 20 KHz is isolated from the isolation capacitor C1 / R11 and the discharging resistor R3 / R5, the current does not turn on the switch elements Q1 and Q2, so that the normal output of the audio signal when the earphone is normally operated is not affected.

If the above requirement is satisfied on the frequency point of 20 KHz, an audio signal of 20 KHz or less can satisfy the above requirement.

In the present embodiment, it is preferable that the isolation capacitor C1 / C3 use a capacitor of a picoparadle class, for example, a design capacitor of several tens picofarads can satisfy a design requirement. The resistance value of the current limiting resistor R10 / R11 is preferably 1 K? Or less, and the resistance value of the discharge resistor R3 / R5 is preferably 10 K? Or more.

Through the design of the circuit, when the earphone plug 1 of the line control earphone is plugged in / out from the audio socket of the host, if the DC voltage on the host side is connected to the left channel terminal L and / When the voltage is applied to the audio transmission line connected to the left and right channel terminals L and R in contact with the terminal R, the turning DC voltage is transmitted to the current limiting resistors R10 and R11 through the isolation capacitors C1 and C3, Q1, and Q2. After the triode pipes Q1 and Q2 are turned on, the audio transmission line is connected to the system ground, and the DC voltage in the audio transmission line is discharged to the ground to prevent noise from being generated through the earphone speakers 3 and 4 do.

After the earphone plug 1 is completely plugged into the audio socket of the host, a normal audio signal output through the host is transmitted to the earphone speakers 3 and 4 through the audio transmission line in the earphone, and the isolation capacitors C1 and C3 It is possible to prevent the switch elements Q1 and Q2 from malfunctioning.

Then, by designing the isolating capacitors C1, C3 in the noise suppression circuit, if the plug-in / out is not complete, for example, when the earphone plug 1 is plugged into the host's audio socket If the left channel terminal L of the earphone does not move after being contacted to the microphone terminal of the audio socket of the host, if there is no isolation capacitor C1, C3, the DC voltage of the microphone terminal connected to the host side is turned on, Q2. ≪ / RTI > After adding the isolation capacitors C1 and C3, since the voltage across the capacitor can not be changed at the moment of contact, the triode T1 / Q2 momentarily turns on and the DC voltage is discharged through the triode T1 / Q2; If it is in contact all the time, the base voltage of the triode Q1 / Q2 drops as the isolation capacitor C1 / C3 discharges through the resistors R10, R3 or R11 and R5, and when the base voltage is 0.7 V or less, Q2 are turned off, and the DC voltage on the host side is not continuously discharged through the triode tube Q1 / Q2, so that excessive consumption of the battery electric quantity on the host side can be prevented.

In addition, the noise suppression circuit of the present embodiment can remove the peak interference signal that is generated suddenly in the process of playing the audio signal. Specifically, the noise suppression circuit of the present embodiment can include a capacitor C1 / C3 having a suitable capacitance value range, It is possible to realize suppression of the peak interference signal within a certain range by selecting the resistance R10 / R3 / R11 / R5.

Therefore, in order to further improve the quality of the audio signal output through the earphone, the left channel audio transmission line and the right channel audio transmission line are also provided with resistance-capacitance filtering circuits respectively, As shown. Here, the resistor R1 and the capacitor C2 connect the first group resistance-capacitance filtering circuit and are connected to the left channel audio transmission line to perform filtering on the left channel audio signal; The resistor R6 and the capacitor C4 connect the second group resistance-capacitance filtering circuit and are connected to the right channel audio transmission line to perform filtering on the right channel audio signal. Specifically, resistor R1 / R6 may be coupled to the audio transmission line and capacitor C2 / C4 may be coupled between the audio transmission line and ground. By adding the resistance-capacitance filtering circuit to the left and right channel audio transmission lines, the interference resistance ability of the line control earphone can be improved and the quality of the audio signal can be ensured. The parameter values of the resistors R1 / R6 and C2 / C4 can be selected specifically according to some objective standards.

In order to improve the quality of the audio signal collected through the microphone of the earphone, in the present embodiment, a pi-type filtering circuit is also designed in the microphone transmission line connected to the microphone terminal MIC of the earphone plug 1, As shown in Fig. 5A, the capacitors C5 / C6 and the inductor L1 constitute a connection. Here, the inductor L1 is connected in series to the microphone transmission line, the capacitors C5 and C6 are correspondingly connected to both ends of the inductor L1, and the other end is grounded.

In the present embodiment, the noise suppressing circuit and the filtering circuit are provided in the line controller 2 of the line control earphone, as shown in Figs. 1 and 2. Connects the left channel audio output terminal L_OUT on the line controller 2 through the cable to the left channel speaker 3 and outputs the left channel audio signal; Connects the right channel audio output R_OUT on the line controller 2 through the cable to the left channel speaker 4 and outputs the right channel audio signal; The microphone signal input terminal MIC_IN on the line controller 2 is connected to a microphone separate from the line controller 2 via a cable or directly connected to a microphone provided in the line controller 2 to receive an audio signal collected via a microphone And transmits it to the host side. Here, the left channel speaker 3 and the right channel speaker 4 are connected to the line controller 2 in a detachable manner, that is, the left and right channel speakers 3 and 4 are combined with an earphone speaker equipped with a plug. E. G., Two ear canal earphones can be plugged in / out from the audio socket of the line controller 2 so that the line controller 2 can receive various earphone speakers; Since the noise suppressing circuit of this embodiment is provided on the line controller 2 and there is no need for a circuit inside the earphone speaker, there is no earphone speaker or no circuit without any noise suppressing circuit When the line controller 2 is plugged in / out to the sound output facility through the earphone plug 1 after the earphone speaker is plugged into the corresponding line controller 2, the earphone speaker likewise plugs in / out noise And a good sound quality effect can be obtained.

The line controller 2 may further include function buttons SW1, SW2, and SW3, for example, buttons for volume size adjustment, function buttons for receiving / disconnecting, and the like. For example, the function button SW1 and the voltage-dividing resistor R7 are connected in series to each other, and the functional button SW1 and the voltage-dividing resistor R7 are connected in series. In order to accurately identify the operation state of the different function buttons, SW2 and the voltage-dividing resistor R8 are connected in series, and the function button SW3 and the voltage-dividing resistor R9 are connected in series; Then, each serial connection branch circuit is connected between the microphone terminal MIC of the earphone plug 1 and the ground. When the earphone plug 1 is plugged into the audio socket of the host, the DC voltage of the DC bias provided by the host side for the microphone signal is interconnected to the voltage dividing resistors R7 to R9 via the rising resistor and the microphone terminal MIC, respectively . When one of the function buttons SW1 / SW2 / SW3 is depressed, a voltage dividing circuit formed by a rising resistor and one of the voltage dividing resistors R7 / R8 / R9 of the rising resistor is connected to divide the voltage with respect to the DC voltage, It is possible to determine which function button SW1 / SW2 / SW3 has been depressed only by detecting the partial pressure value of the function button, and further, the host can be controlled to perform the corresponding operation and respond to the user's operation.

In the present embodiment, it is preferable that the function buttons SW1, SW2, and SW3 are selected by using a mechanical button having no self-locking function. The voltage-dividing resistors R7, R8, and R9 generally select a resistance value within 1000 ohms, and more specifically, by a voltage setting value that can be identified when each button of the plugged-in host is pressed.

The earphone circuit as shown in Figure 2 only supports a line control earphone of one plug and one audio socket on the basis of the circuit shown in Figure 2 for a line control earphone with two plugs , The audio socket Unite-2 as shown in Fig. 3 can be specifically placed on the line controller 2 of the earphone. The audio socket Unite-2 may be a four-stage audio socket, and the audio socket Unite-2 is provided with a left channel pin HL, a right channel pin HR, a microphone pin mic and a ground pin G. Connects the left channel pin HL of the audio socket Unite-2 to the left channel audio output L_OUT of the line controller 2, connects the right channel pin HR to the right channel audio output R_OUT of the line controller 2, To the microphone signal input terminal MIC_IN of the line controller 2, and the ground pin G is grounded through a button SW4 having a self-locking function.

When the earphone plug of the other four-speed line control earphone is plugged into the audio socket Unite-2 and the button SW4 is not pressed, since the earphone pin G is an open circuit, the plugged earphone is not grounded, No signal is output, thereby preventing plug-in / out noise from occurring when plugging another earphone into the audio socket Unite-2. Only after the button SW4 is pressed and the ground pin G is well grounded, the plug-in line control earphone can be normally used, and the left and right channel audio signals can be output and the microphone signal can be received. If the earphone plugged into the audio socket Unite-2 does not want to hear the conversation when the phone rings, turn off the button SW4 and press the SW4 button again after the call ends to connect another earphone. have.

The earphone circuit provided in the present embodiment does not need to supply electric power by using a separate power source and it is only required that the host side to which the plug is plugged is provided with the DC bias voltage for the microphone terminal MIC so as to perform the corresponding driving , The circuit design is simple, the cost is low, the noise generated during the earphone plug-in / out process can be thoroughly suppressed, and the satisfaction of the earphone user can be improved.

While the present invention has been particularly shown and described with reference to the particular embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (10)

An audio processing circuit for removing an earphone plug in / out noise,
One noise suppression circuit is connected to the audio transmission line for transmitting the left channel audio signal and the right channel audio signal in the earphone, and the noise suppression circuit is provided with the isolation capacitor and the switch element;
One end of the isolation capacitor is connected to the audio transmission line and the other end is connected to a control electrode of the switch element;
The parameter value selection principle of the isolation capacitor is such that when an audio signal in a normal frequency range is transmitted to the control electrode of the switch element through the isolation capacitor, the current applied to the control electrode is smaller than the minimum ON current of the switch element However,
Before and after the earphone plug-in / out, the switch element is turned off. In the earphone plug-in / out process, an applied direct current voltage is transmitted to the switch element through the isolation capacitor, the switch element is turned on, Is an earphone plug grounded via a switch path of the switch element. The method according to claim 1,
The isolation capacitor is connected to the control electrode of the switch element through one series-connected current limiting resistor, and the control electrode of the switch element is grounded through one discharge resistor;
Wherein the resistance value of the current limiting resistor and the discharging resistance satisfies that the voltage drop formed at both ends of the discharging resistor after the turning DC voltage passes through the isolation capacitor and the current limiting resistor turns on the switching element. Audio processing circuit for in / out noise rejection. The method of claim 2,
The resistance value of the current limiting resistor is 1K or less;
Wherein the resistance value of the discharge resistor is 10K? Or more. The method of claim 2,
Wherein the switch element is an NPN triode, the base of the triode tube is connected to the current limiting resistor, the collector is connected to the audio transmission line, and the emitter is an earphone plug in / . The method according to claim 1,
The normal frequency range of the audio signal is 20 Hz to 20 KHz;
Wherein the isolation capacitor is a pico-class-class capacitor, the audio processing circuit for removing an earphone plug in / out noise. The method according to claim 1,
Each of the audio transmission lines transmitting the left channel audio signal and the right channel audio signal is also each connected to one resistance-capacitance filtering circuit; An audio processing circuit for eliminating in / out noise of an earphone plug in which a π-type filtering circuit composed of a capacitor and an inductor is connected to a microphone transmission line to which a microphone terminal of the earphone is connected. The method of claim 6,
The audio processing circuit is installed in a line controller of the earphone. The line controller is provided with a plurality of function buttons. The different function buttons are connected in series with the voltage dividing resistors having different resistance values. And the function button is a mechanical button having no self-locking function. The audio processing circuit for removing an earphone plug in / out noise. The method of claim 7,
Further adding one audio socket to the line controller, wherein the audio socket is provided with a left channel pin, a right channel pin, a microphone pin and a ground pin;
The left channel pin is connected to the left channel audio output of the line controller and the left channel audio output is connected to the left channel speaker through a cable;
The right channel pin is connected to the right channel audio output of the line controller and the right channel audio output is connected to the right channel speaker via a cable;
The microphone pin is connected to a microphone laid on a line controller or to a microphone signal input terminal of a line controller, and the microphone signal input is connected to a microphone through a cable;
Wherein the earthing pin is grounded through a single button having a self-locking function. In a line control earphone,
Wherein the line control earphone is provided with an audio processing circuit for eliminating the earphone plug in / out noise according to any one of claims 1 to 8. delete
KR1020177014750A 2014-12-04 2015-11-27 Audio processing circuit for eliminating plug-in and plug-out noise of earphone, and line control earphone KR101887322B1 (en)

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