CN203788450U - Current hum restraining circuit of mobile terminal and mobile terminal - Google Patents
Current hum restraining circuit of mobile terminal and mobile terminal Download PDFInfo
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- CN203788450U CN203788450U CN201420189837.0U CN201420189837U CN203788450U CN 203788450 U CN203788450 U CN 203788450U CN 201420189837 U CN201420189837 U CN 201420189837U CN 203788450 U CN203788450 U CN 203788450U
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Abstract
The utility model discloses a current hum restraining circuit of a mobile terminal and a mobile terminal. The circuit is used for effectively filtering current hums transmitted through a microphone audio channel. Through arranging a resonant circuit composed of magnetic beads and a filter capacitor in the audio channel connected with a microphone, the problem of transmitting current hums generated due to antenna radiation interference through the microphone audio channel is solved. Single-end audio signals outputted by the microphone is configured to be in a difference mode, a positive electrode and a negative electrode of a difference signal are pulled upwardly to the same bias power supply, conduction interference signals introduced through the bias power supply is loaded on the positive electrode and the negative electrode of the difference signal, common mode interference is formed, restraining characteristics of a differential amplifier on the common mode interference are used for realizing effectively filtering conduction interference, the problem of transmitting current hums generated due to conduction interference through the microphone audio channel is thus solved, and the call quality of the mobile terminal is obviously improved.
Description
Technical field
The utility model belongs to mobile communication terminal technical field, specifically, relates to a kind of for eliminating circuit structure design and the mobile terminal product of the current sound transmitting by microphone audio passage.
Background technology
Day by day universal along with mobile terminal, performance and the quality of user to mobile terminal product also had higher requirement.Be accompanied by the popular of ultrathin design; in mobile terminal, the number of plies of pcb board reduces to some extent; this causes some crucial holding wires to be difficult to be effectively protected and isolate; for existing some mobile terminal product; for example: GSM mobile handset, user, in the time utilizing mobile phone to converse, often can hear the current sound of " Zi Zi "; not only affect speech quality, also reduced the satisfaction that cellphone subscriber uses.
The inventor finds in the time implementing the utility model scheme, and the current sound occurring in mobile terminal calling process, is mainly derived from two parts: aerial radiation disturbs and conducted interference.For example, in GSM mobile handset: because GSM mobile handset is when by its inner external emitting radio frequency signal of radio-frequency power amplifier PA, when being operated under burst mode, the frequency of the envelope of the burst radiofrequency signal of sending by radio frequency PA is 217Hz, and the audio frequency range that people's ear can be heard is between 20Hz-20KHz, if therefore GSM mobile handset is processed bad in the time of design and PCB fabric swatch, with regard to being easy to, the radiation signal of above-mentioned 217Hz is incorporated in the voice-grade channel of interior of mobile phone, disturbs thereby produce aerial radiation.On the other hand, when GSM mobile handset is operated in burst mode lower time, said frequencies is that the radiation signal of 217Hz also can be radiated on the power supply of interior of mobile phone, if PCB fabric swatch and the wiring of mobile phone are not suitably processed, be easy to cause the bias supply that is connected with voice-grade channel to be subject to the impact of other power supply signals and be superimposed with the interference waveform of 217Hz, thereby producing conducted interference.In the time that the voice-grade channel of mobile terminal inside is subject to above-mentioned aerial radiation interference and conducted interference, will make user in the time playing phone, hear the current sound of " Zi Zi ".
Summary of the invention
The utility model is prone to the problem of current sound in communication process in order to solve some mobile terminal product, proposed a kind of current sound and suppressed circuit, for the current noise of microphone audio passage is effectively suppressed, to improve speech quality.
For solving the problems of the technologies described above, the utility model is achieved by the following technical solutions:
A kind of current sound of mobile terminal suppresses circuit, comprise microphone and differential amplifier, described microphone is exported single-ended audio signal, transfer to the positive polarity input terminal of differential amplifier via first magnetic bead of connecting and the first capacitance, the intermediate node of described the first magnetic bead and the first capacitance passes through the first filter capacitor ground connection, and connects bias supply by the first pull-up resistor; The negative polarity input terminal of described differential amplifier is connected described bias supply by the second capacitance of series connection with the second pull-up resistor.
Further, described the first magnetic bead and the first filter capacitor form resonant circuit, the resonance point frequency of described resonant circuit is consistent with the antenna carrier frequency of described mobile terminal, can make thus resonant circuit impedance minimum in the time of resonance, and then make the emittance of antenna to be discharged into ground by filter capacitor rapidly, in effectively eliminating aerial radiation interference, can also play good buffer action to FM FM signal, make mobile terminal can receive the more FM FM signal of multiband.
Further again, the antenna of described mobile terminal is GSM antenna, and the carrier frequency of described GSM antenna is 900MHz.
Preferably, the capacitance of described the first filter capacitor is 33pF, and the impedance under the frequency of 100MHz of described the first magnetic bead is 600 Ω.
In order further to eliminate the radiated interference of antenna space, the second magnetic bead one tunnel of preferably described bias supply being passed through to series connection is via the second filter capacitor ground connection, and another road connects respectively described the first pull-up resistor and the second pull-up resistor.
For the interference signal that prevents that ground bounce noise from bringing, preferably described the first filter capacitor and the second filter capacitor are connected to the main stratum of pcb board by being opened in via hole on pcb board.
Further, described microphone can be mounted in the main microphone on terminal body, also can be mounted in the ear microphone on earphone, in the time that described microphone is the main microphone being arranged on terminal body, described main microphone is by the described single-ended audio signal of its anodal output; The amplitude of described bias supply equals the required power supply amplitude of main microphone work; Described differential amplifier is the differential amplifier being integrated in the audio processing chip of mobile terminal inside.
In the time that described microphone is the ear microphone being arranged on earphone, in the time that earphone is inserted on the earphone socket of mobile terminal, described ear microphone is communicated with the microphone terminal in earphone socket, the single-ended audio signal that transmission is described; The amplitude of described bias supply equals the required power supply amplitude of ear microphone work; Described differential amplifier is the differential amplifier being integrated in the audio processing chip of mobile terminal inside.
Further, in described earphone socket, be provided with left and right sound channels audio frequency terminal, the left and right sound channels audio signal of exporting by audio processing chip transfers to the left and right sound channels audio frequency terminal of earphone socket separately by a voice-grade channel correspondence, in the voice-grade channel described in each, be in series with respectively an independently magnetic bead, voice-grade channel described in each passes through respectively independently filter capacitor ground connection, utilize described magnetic bead and filter capacitor effectively to isolate wireless FM FM signal, to improve the receiving ability of mobile terminal to FM FM signal.
Suppress circuit based on above-mentioned current sound, the utility model has also proposed a kind of mobile terminal that adopts described current sound to suppress circuit design, comprise microphone and differential amplifier, described microphone is exported single-ended audio signal, transfer to the positive polarity input terminal of differential amplifier via first magnetic bead of connecting and the first capacitance, the intermediate node of described the first magnetic bead and the first capacitance passes through the first filter capacitor ground connection, and connects bias supply by the first pull-up resistor; The negative polarity input terminal of described differential amplifier is connected described bias supply by the second capacitance of series connection with the second pull-up resistor, just can eliminate thus the current sound sending by microphone channel.
Compared with prior art, advantage of the present utility model with good effect is: the utility model, by the resonant circuit being made up of magnetic bead and filter capacitor is set in the voice-grade channel that is connected microphone, has solved the problem of passing through microphone audio passage transmission current sound producing because of aerial radiation interference thus, by adopting, the single-ended audio signal of microphone output is configured to difference form, and to the design of same bias supply will be moved on the both positive and negative polarity of differential signal, thereby the conducted interference of introducing by bias supply can be carried on the both positive and negative polarity of differential signal simultaneously, form common mode disturbances, and then utilize differential amplifier to amplify processing to described differential signal, can eliminate the characteristic of common mode disturbances by differential amplifier, just can realize the effective filtering to conducted interference, and then solve the microphone audio passage that passes through producing because of conducted interference and transmitted the problem of current sound.The current sound that the utility model is proposed suppresses circuit application in the mobile terminal products such as mobile phone, can avoid cellphone subscriber in communication process, to hear the current sound of " Zi Zi ", significantly promoting speech quality, when improving cellphone subscriber's user satisfaction, also contribute to promote the complete machine quality of mobile phone products.
Read by reference to the accompanying drawings after the detailed description of the utility model execution mode, other feature of the present utility model and advantage will become clearer.
Brief description of the drawings
Fig. 1 is the circuit theory diagrams of a kind of embodiment of earphone voice-grade channel in existing mobile phone circuit;
Fig. 2 is the circuit theory diagrams that current sound that the utility model is proposed suppresses a kind of embodiment of circuit application in earpiece audio passage;
Fig. 3 is the circuit theory diagrams of a kind of embodiment of main microphone audio passage in existing mobile phone circuit;
Fig. 4 is the circuit theory diagrams that current sound that the utility model is proposed suppresses a kind of embodiment of circuit application in main microphone audio passage.
Embodiment
Below in conjunction with accompanying drawing, embodiment of the present utility model is described in detail.
The present embodiment is taking GSM mobile handset as described mobile terminal as example, described current sound being suppressed to concrete assembling structure and the operation principle thereof of circuit at length sets forth, the application that should be noted that scheme of the present utility model is not only confined to GSM mobile handset, also can be for the mobile terminal such as panel computer, intelligent watch.
For GSM mobile handset, frequency range by handset antenna radiation is in the interference signal of 20-20KHz, once be incorporated in the voice-grade channel of mobile phone, just likely produce the current sound (below the current sound being produced by this situation being referred to as to GSM current sound) of " Zi Zi ".In the design of existing GSM mobile handset, may exist the voice-grade channel of GSM current sound to mainly contain: connect earpiece voice-grade channel, connect the voice-grade channel of mobile phone speaker and connect the voice-grade channel (described microphone comprise be laid in the main microphone in mobile phone body and be arranged on the ear microphone on earphone) etc. of microphone.Because the audio signal itself of receiver and loud speaker reception just requires difference form, and be the passive device that does not need power drives, therefore, be easier to process for the GSM current sound ratio of the voice-grade channel that is incorporated into receiver and loud speaker.And for the GSM current sound that is incorporated into microphone audio passage, because the audio signal of exporting by microphone is single-ended signal, therefore cannot disturb processing mode by the employing GSM current sound identical with receiver and loud speaker.
In view of above reason, the present embodiment, for the interference signal that is incorporated into microphone audio passage, has proposed a kind of current sound and has suppressed circuit, for eliminating the current sound sending by the microphone audio passage of mobile phone.
Because the source of GSM current sound in mobile phone mainly contains two parts: aerial radiation disturbs and conducted interference, therefore for the interference signal of these two kinds of routes of transmission, the present embodiment proposes two kinds of circuit design modes: a kind of is to set up the resonant circuit being formed by connecting by magnetic bead and filter capacitor in the voice-grade channel that connects microphone, utilize described resonant circuit that aerial radiation is discharged into ground to the energy in microphone audio passage, to realize effective filtering that aerial radiation is disturbed, eliminate and disturb the current sound producing because of aerial radiation in microphone audio passage, and meanwhile play the buffer action to FM FM signal, another kind is that the single-ended audio signal of exporting by microphone is configured to false differential signal pattern, and will on the both positive and negative polarity of described differential signal, move on the bias supply of same road, make to conduct to by bias supply positive and negative two inputs that conducted interference in microphone audio passage can be carried in differential signal simultaneously and extremely go up, to form common mode interference signal.Because differential amplifier has the characteristic of eliminating common mode disturbances, therefore can be by described differential signal transmission to differential amplifier, when utilizing differential amplifier to carry out differential amplification processing to the audio signal of microphone output, realize the effective filtering to conducted interference, to eliminate the current sound producing because of conducted interference in microphone audio passage.
Due in existing Cell Phone Design, mainly contain two for picking up the microphone of user speech: a main microphone being mounted in mobile phone body; Another is mounted in the ear microphone on earphone, therefore, for these two microphones, on the pcb board of interior of mobile phone, can lay respectively two microphone audio passages, carrys out the audio signal of autonomous microphone and ear microphone with correspondence transmission.In order to eliminate all sidedly the GSM current sound sending by microphone audio passage, the present embodiment difference design current sound in the voice-grade channel that connects main microphone and ear microphone suppresses circuit, and the aerial radiation that is incorporated into microphone audio passage to eliminate to greatest extent disturbs and conducted interference.
For connecting the voice-grade channel of main microphone and the voice-grade channel of frames connecting with headphone microphone, the current sound respectively the present embodiment being proposed suppresses the specific design mode of circuit and at length sets forth below.
Fig. 1 is in existing mobile phone circuit, for the audio transmission channel designed with the matching used earphone of mobile phone body, comprises microphone audio passage and left and right acoustic channels voice-grade channel.Wherein, the microphone terminal 6 on microphone audio passage frames connecting with headphone socket CN7001, for transmitting the user speech picking up by ear microphone.Because the audio signal of exporting by ear microphone is single-ended audio signal MIC+, and mobile phone sound intermediate frequency process chip need to receive the audio signal of difference form, therefore in the time of design microphone audio passage, the single-ended audio signal MIC+ of microphone output can be configured to a pair of false differential signal, to meet the reception requirement of audio processing chip.
In existing circuit design, the method that the single-ended audio signal MIC+ of ear microphone output is configured to differential signal is: the positive polarity input terminal MSM_MIC2P that the single-ended audio signal MIC+ of the positive pole output by ear microphone is transferred to the microphone interface of audio processing chip via the first capacitance C7007, and be connected to the bias supply HSED_BIAS1 of ear microphone by the first pull-up resistor R7005, the amplitude of described bias supply HSED_BIAS1 equals the amplitude of the required power supply of ear microphone work, utilize described bias supply HSED_BIAS1 is ear microphone power supply simultaneously, by the negative polarity input terminal MSM_MIC2N of the microphone interface of audio processing chip, by the second capacitance C7010 ground connection, the cabling of two paths is made difference cabling in the time that PCB designs, and is configured to thus a pair of false differential signal.Adopt sort circuit design, although can have inhibition to the interference signal that directly has influence on ear microphone voice-frequency channel, but, conduct the interference of coming for the bias supply HSED_BIAS1 by ear microphone and just can not play inhibitory action, and be also difficult to realize filtering up hill and dale for the radiated interference of GSM antenna generation, be therefore easy to produce GSM current sound in the communication process of mobile phone.
In order to solve the problem that sends current sound by the voice-grade channel of ear microphone, the present embodiment is from suppressing antenna radiated interference and conducted interference two aspects, and design current sound suppresses circuit respectively, shown in Figure 2.First, i.e. the first magnetic bead L7003 of a magnetic bead L7003(connects in the microphone terminal 6 of earphone socket CN7001 connects the voice-grade channel of positive polarity input terminal MSM_MIC2P of the microphone interface of audio processing chip), make the single-ended audio signal MIC+ exporting by the positive pole of ear microphone transfer to audio processing chip via the first magnetic bead L7003 and the first capacitance C7007 of series connection, specifically can transfer to the positive polarity input terminal MSM_MIC2P of the differential amplifier of audio processing chip inside, then the intermediate node of described the first magnetic bead L7003 and the first capacitance C7007 is passed through to the first filter capacitor C7012 ground connection, and be connected to the bias supply HSED_BIAS1 of ear microphone by the first pull-up resistor R7005.For the negative polarity input terminal MSM_MIC2N of differential amplifier, originally the earth terminal of the second capacitance C7010 of the described negative polarity input terminal MSM_MIC2N that connected can be disconnected, then be connected to described bias supply HSED_BIAS1 by pull-up resistor R7016, just the single-ended audio signal MIC+ of ear microphone output can be configured to a pair of differential signal thus, and then utilize differential amplifier to carry out after differential amplification processing microphone signal, other functional modules of recycling audio processing chip inside are carried out subsequent treatment.
The present embodiment, by set up the first magnetic bead L7003 and the first filter capacitor C7012 in the voice-grade channel of frames connecting with headphone microphone, can form resonant circuit thus.Regulate the parameter value of the first magnetic bead L7003 and the first filter capacitor C7012, to change the resonance point frequency of described resonant circuit.In the present embodiment, preferably the resonance point frequency configuration of described resonant circuit is become to consistent with the antenna carrier frequency of mobile phone, just can make thus described resonant circuit impedance minimum in the time of resonance.So, just can discharge over the ground by the first filter capacitor C7012 rapidly by the energy of aerial radiation, just reach thus and eliminated the purpose of design of disturbing the current sound producing because of aerial radiation.
For the GSM mobile handset of the present embodiment, described antenna is GSM antenna, because the carrier frequency of GSM antenna is 900MHz, therefore, the resonance point Frequency Design of described resonant circuit can be become to 900MHz, to improve the filtration result that aerial radiation is disturbed.
As a kind of preferred design of the present embodiment, the capacitance of described filter capacitor C7012 is preferably 33pF, and it is the magnetic bead element of 600 Ω that described magnetic bead L7003 preferably adopts impedance under 100MHz frequency.
The present embodiment is set up the resonant circuit being made up of the first magnetic bead L7003 and the first filter capacitor C7012 in the voice-grade channel of ear microphone, when the radiated interference of GSM antenna is carried out to effective filtering, can also play good buffer action to the required FM FM signal of radio function in mobile phone.
The impact that is easy to be subject to other power supply signals due to the bias supply HSED_BIAS1 of ear microphone in PCB fabric swatch and wiring is superimposed with the interference waveform of 217Hz, and this interference waveform is the root that a lot of GSM mobile handset send current sounds.In order to eliminate this conducted interference, the present embodiment is connected to same road bias supply HSED_BIAS1 by the first pull-up resistor R7005 and the second pull-up resistor R7016 respectively by the both positive and negative polarity differential signal line of microphone audio passage, so, for the differential amplifier of audio processing chip inside, the interference signal being added on bias supply HSED_BIAS1 is just being carried in differential amplifier simultaneously, the sub-MSM_MIC2P of negative input, on MSM_MIC2N, thereby formation common mode disturbances, then utilize differential amplifier can eliminate the characteristic of common mode interference signal, just can filter out neatly the GSM current sound producing because of conducted interference on microphone audio passage.Adopt sort circuit design, can for example, produce good inhibitory action to other common-mode noises in voice-frequency channel (making an uproar in the end) equally.
As a kind of preferred circuit design of the present embodiment, preferably adopt the resistance device of similar resistance for the first pull-up resistor R7005 and the second pull-up resistor R7016, same current potential will be moved to, on the voltage magnitude of bias supply HSED_BIAS1 on the DC offset voltage of both positive and negative polarity differential signal.In order further near aerial radiation bias supply HSED_BIAS1 to be disturbed and to carry out effective filtering, the second magnetic bead L7001 can also connect in described bias supply HSED_BIAS1 connects the circuit of the first pull-up resistor R7005 and the second pull-up resistor R7016, and by the second filter capacitor C7002 ground connection, shown in Figure 2.Utilize the resonant circuit of the second magnetic bead L7001 and the second filter capacitor C7002 formation, can further eliminate the radiated interference of antenna space, further to improve the inhibition of GSM current sound.
In addition, for the interference signal that prevents that ground bounce noise from bringing, the present embodiment preferably for example, is directly beaten via hole by the earth terminal that is connected to all capacitor elements (the second filter capacitor C7012 and the first filter capacitor C7002) that need ground connection on ear microphone voice-grade channel and is connected to the main stratum of pcb board, by adopting the mode of beating via hole on pcb board, by filter capacitor C7002, the earth terminal of C7012 is by the main stratum ground connection of pcb board, avoid the surface earthing of these capacitor elements at pcb board, can prevent thus the ground bounce noise producing around laying because of grounding wire impedance.
For the left channel audio signal PM_HPA_OUT_L and the right channel audio signal PM_HPA_OUT_R that process output by audio processing chip, can pass through separately independently filter capacitor C7020, C7019 ground connection of a road, and separately by the magnetic bead L7004 of a road series connection, the left and right sound channels audio frequency terminal 5,2 that L7005 correspondence is connected to earphone socket CN7001, shown in Figure 2.The resonant circuit that utilizes described magnetic bead L7004, L7005 and filter capacitor C7020, C7019 to form, in effectively suppressing the interference of GSM aerial radiation, can also play the effect of the wireless FM FM signal of isolation, and then make the cellphone subscriber can the more FM broadcasting of multiband of uppick.
In order to prevent when the grafting earphone, outside electrostatic interference is incorporated in the circuit of interior of mobile phone by earphone socket CN7001, pcb board to interior of mobile phone impacts damage, the present embodiment is preferably on microphone terminal 6 and a left side of frames connecting with headphone socket CN7001, right audio channel terminal 5, on 2 voice-frequency channel, design respectively anti-static circuit, for example be connected to the ESD antistatic diode D7008 on microphone audio path and be connected to a left side, piezo-resistance RV7004 on right audio channel path, RV7005, to realize static surge current releasing rapidly over the ground.
Fig. 3 is in existing mobile phone circuit, for the audio transmission channel that is laid in the main microphone B7001 design in mobile phone body.Described main microphone B7001 is by its positive pole+export single-ended audio signal MIC1+, negative pole-ground connection.The single-ended audio signal MIC1+ of main microphone B7001 output is transferred to the positive polarity input terminal MSM_MIC1P of the main microphone interface of audio processing chip by capacitance C7023, and be connected to the bias supply VMSM_MICBIAS of main microphone by pull-up resistor R7001.The amplitude of described bias supply VMSM_MICBIAS equals the amplitude of the required power supply of main microphone work, and utilize described bias supply VMSM_MICBIAS is main microphone power simultaneously.The negative polarity input terminal MSM_MIC1N of the main microphone interface of audio processing chip, by capacitance C7025 ground connection, is configured to a pair of false differential signal thus.
Same, adopt sort circuit design, although can have inhibition to the interference signal that directly has influence on main microphone audio path, but, conduct the interference of coming for the bias supply VMSM_MICBIAS by main microphone and just can not play inhibitory action, and be also difficult to realize filtering up hill and dale for the radiated interference of GSM antenna generation, be therefore easy to produce GSM current sound in the communication process of mobile phone.
In order to solve the problem that sends current sound by the voice-grade channel of main microphone, first the present embodiment sets up the resonant circuit being made up of magnetic bead L7013 and filter capacitor C7028 in main microphone B7001 transmits the path of single-ended audio signal MIC1+, utilize resonant circuit effectively to suppress the radiated interference of antenna, and play the effect of isolation FM FM signal simultaneously.Secondly, to be configured to a pair of false differential signal by the single-ended audio signal MIC1+ of main microphone B7001 output, and the both positive and negative polarity of described false differential signal is pulled to same road bias supply, the bias supply VMSM_MICBIAS of for example main microphone, and then utilize differential amplifier to realize the effective filtering to conducted interference, shown in Figure 4.
Specifically, can be by the positive pole of main microphone B7001+be connected to the positive polarity input terminal MSM_MIC1P of differential amplifier by magnetic bead L7013 and the capacitance C7023 of series connection, and by the intermediate node of magnetic bead L7013 and capacitance C7023 by filter capacitor C7028 ground connection.Regulate the resonance point frequency of the resonant circuit of described magnetic bead L7013 and filter capacitor C7028 composition, make it consistent with the carrier frequency of antenna for mobile phone, for example, for GSM antenna, can regulate the parameter value of described magnetic bead L7013 and filter capacitor C7028, make the resonance point frequency of resonant circuit equal 900MHz, thereby realize antenna energy by filter capacitor C7028 rapid release over the ground with minimum impedance, solved because aerial radiation disturbs the voice-grade channel that passes through main microphone causing and transmitted the problem of GSM current sound.
The intermediate node of described magnetic bead L7013 and capacitance C7023 is connected to the bias supply VMSM_MICBIAS of main microphone by pull-up resistor R7001, utilize bias supply VMSM_MICBIAS to power to main microphone MIC1+, and the negative polarity input terminal MSM_MIC1N of differential amplifier is connected to described bias supply VMSM_MICBIAS by capacitance C7026 and the pull-up resistor R7002 of series connection, make the conducted interference of introducing by bias supply VMSM_MICBIAS be carried in the both positive and negative polarity input terminal MSM_MIC1P of differential amplifier simultaneously, on MSM_MIC1N, form common mode disturbances, and then the common mode disturbances suppression characteristic that utilizes differential amplifier itself to have, realize the effective filtering to conducted interference in main microphone audio passage, solve the problem that the voice-grade channel that passes through main microphone causing because of conducted interference sends GSM current sound.
In the present embodiment, described differential amplifier can independently arrange, and also can select the differential amplifier that is integrated in audio processing chip inside to carry out differential amplification processing to the audio signal of main microphone B7001 output, and the present embodiment does not specifically limit this.
As a kind of preferred design of the present embodiment, described pull-up resistor R7001 and R7002 preferably adopt two resistance devices that resistance is equal.For near the antenna space radiated interference to bias supply VMSM_MICBIAS is carried out effective filtering, can also in the circuit of described bias supply VMSM_MICBIAS connection pull-up resistor R7001 and R7002, further set up the resonant circuit being formed by connecting by magnetic bead C7015 and filter capacitor C7027, shown in Figure 4, further to eliminate radiated interference.Specifically, described magnetic bead C7015 can be connected between bias supply VMSM_MICBIAS and pull-up resistor R7001, R7002, the intermediate node of bias supply VMSM_MICBIAS and pull-up resistor R7001, R7002 is by filter capacitor C7027 ground connection.The earth terminal of all ground capacities in main microphone audio path (for example filter capacitor C7027, C7028) is connected directly to the main stratum of pcb board by being opened in via hole on pcb board, with the interference signal that prevents that ground bounce noise from being brought.
In like manner, in order to suppress electrostatic impact, the present embodiment is at the positive pole of main microphone B7001+be also connected with anti-static circuit, for example, by the positive pole of main microphone B7001+by piezo-resistance RV7001 ground connection, with surge current suppression.
The present embodiment suppresses the characteristic of radiated interference, difference channel inhibition common mode disturbances based on resonant circuit, in conjunction with the optimal design of PCB cabling, reached the purpose of design of eliminating mobile microphone transmission current sound.Certainly, current sound that the present embodiment proposes suppresses that circuit is equally applicable to the mobile phone products of other communication standards or other except mobile phone have in the mobile terminal product of voice communication function, and the present embodiment is not limited in above giving an example.
It should be noted that; the above is only a kind of preferred implementation of the present utility model; for those skilled in the art; do not departing under the prerequisite of the utility model principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection range of the present utility model.
Claims (10)
1. the current sound of a mobile terminal suppresses circuit, comprise microphone and differential amplifier, it is characterized in that: described microphone is exported single-ended audio signal, transfer to the positive polarity input terminal of differential amplifier via first magnetic bead of connecting and the first capacitance, the intermediate node of described the first magnetic bead and the first capacitance passes through the first filter capacitor ground connection, and connects bias supply by the first pull-up resistor; The negative polarity input terminal of described differential amplifier is connected described bias supply by the second capacitance of series connection with the second pull-up resistor.
2. the current sound of mobile terminal according to claim 1 suppresses circuit, it is characterized in that: described the first magnetic bead and the first filter capacitor form resonant circuit, and the resonance point frequency of described resonant circuit is consistent with the antenna carrier frequency of described mobile terminal.
3. the current sound of mobile terminal according to claim 2 suppresses circuit, it is characterized in that: the antenna of described mobile terminal is GSM antenna, and the carrier frequency of described GSM antenna is 900MHz.
4. the current sound of mobile terminal according to claim 3 suppresses circuit, it is characterized in that: the capacitance of described the first filter capacitor is 33pF, and the impedance under the frequency of 100MHz of described the first magnetic bead is 600 Ω.
5. suppress circuit according to the current sound of the mobile terminal described in any one in claim 1 to 4, it is characterized in that: described bias supply passes through the second magnetic bead one tunnel of series connection via the second filter capacitor ground connection, and another road connects respectively described the first pull-up resistor and the second pull-up resistor.
6. the current sound of mobile terminal according to claim 5 suppresses circuit, it is characterized in that: described the first filter capacitor and the second filter capacitor are connected to the main stratum of pcb board by being opened in via hole on pcb board.
7. the current sound of mobile terminal according to claim 6 suppresses circuit, it is characterized in that: described microphone is the main microphone being arranged on terminal body, and described main microphone is by the described single-ended audio signal of its anodal output; The amplitude of described bias supply equals the required power supply amplitude of main microphone work; Described differential amplifier is integrated in the audio processing chip of mobile terminal.
8. the current sound of mobile terminal according to claim 6 suppresses circuit, it is characterized in that: described microphone is the ear microphone being arranged on earphone, in the time that earphone is inserted on the earphone socket of mobile terminal, described ear microphone is communicated with the microphone terminal in earphone socket, the single-ended audio signal that transmission is described; The amplitude of described bias supply equals the required power supply amplitude of ear microphone work; Described differential amplifier is integrated in the audio processing chip of mobile terminal.
9. the current sound of mobile terminal according to claim 8 suppresses circuit, it is characterized in that: in described earphone socket, be provided with left and right sound channels audio frequency terminal, the left and right sound channels audio signal of exporting by audio processing chip transfers to the left and right sound channels audio frequency terminal of earphone socket separately by a voice-grade channel correspondence, in the voice-grade channel described in each, be in series with respectively an independently magnetic bead, the voice-grade channel described in each passes through respectively independently filter capacitor ground connection.
10. a mobile terminal, is characterized in that: the current sound that is provided with the mobile terminal as described in any one claim in claim 1 to 9 suppresses circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201420189837.0U CN203788450U (en) | 2014-04-18 | 2014-04-18 | Current hum restraining circuit of mobile terminal and mobile terminal |
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| CN201420189837.0U CN203788450U (en) | 2014-04-18 | 2014-04-18 | Current hum restraining circuit of mobile terminal and mobile terminal |
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| CN201420189837.0U Expired - Fee Related CN203788450U (en) | 2014-04-18 | 2014-04-18 | Current hum restraining circuit of mobile terminal and mobile terminal |
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| CN105376675A (en) * | 2015-12-11 | 2016-03-02 | 小米科技有限责任公司 | Microphone circuit |
| CN105992098A (en) * | 2015-01-30 | 2016-10-05 | 中兴通讯股份有限公司 | Audio input circuit and electronic terminal |
| CN107172540A (en) * | 2017-06-26 | 2017-09-15 | 上海与德科技有限公司 | A kind of Dolby circuit, filter circuit and the equipment of earphone Mike signal |
| CN107592591A (en) * | 2017-07-21 | 2018-01-16 | 深圳天珑无线科技有限公司 | Filter circuit and its application process, the device and electronic installation with store function |
| CN107809702A (en) * | 2017-09-30 | 2018-03-16 | 深圳市艾特智能科技有限公司 | Signal output apparatus |
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