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WO2018186540A1 - Écouteur suppresseur de bruit actif utilisant un signal numérique à 3 niveaux - Google Patents

Écouteur suppresseur de bruit actif utilisant un signal numérique à 3 niveaux Download PDF

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Publication number
WO2018186540A1
WO2018186540A1 PCT/KR2017/009119 KR2017009119W WO2018186540A1 WO 2018186540 A1 WO2018186540 A1 WO 2018186540A1 KR 2017009119 W KR2017009119 W KR 2017009119W WO 2018186540 A1 WO2018186540 A1 WO 2018186540A1
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Prior art keywords
signal
level digital
level
analog
digital signal
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Ceased
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PCT/KR2017/009119
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English (en)
Korean (ko)
Inventor
박홍준
장영재
조성은
목임수
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POSTECH Academy Industry Foundation
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POSTECH Academy Industry Foundation
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase

Definitions

  • the present invention reduces the loop delay time using a three-level digital signal, in particular a three-level pulse width modulation (PWM) signal or a three-level pulse density modulation (PDM) signal, thereby reducing An active noise reduction earphone using a three-level digital signal capable of increasing the frequency range where active noise canceling is possible.
  • a three-level digital signal in particular a three-level pulse width modulation (PWM) signal or a three-level pulse density modulation (PDM) signal, thereby reducing An active noise reduction earphone using a three-level digital signal capable of increasing the frequency range where active noise canceling is possible.
  • PWM pulse width modulation
  • PDM three-level pulse density modulation
  • ANC Active Noise Canceling
  • FIG. 1 is a conceptual diagram of a conventional analog active noise reduction (ANC) earphone.
  • a conventional analog active noise reduction earphone 100 includes an analog subtractor 110, a first analog amplifier A1 and 120, an acoustic signal generator 130, and a second analog amplifier A2 and 140. It is provided.
  • the analog subtractor 110 subtracts the analog feedback signal A FB from the analog audio signal A IN .
  • the first analog amplifiers A1 and 120 receive the analog difference signal A ER as an input and amplify the analog difference signal A ER to output the amplified difference signal.
  • the acoustic signal generator 130 includes an earphone speaker SP, 131, an adder 132, and a microphone MIC 133, and is located in an ear canal of the user.
  • the earphone speaker SP 131 receives the difference signal amplified by the first analog amplifiers A1 and 120 and outputs a speaker output sound signal S ER .
  • the adder 132 combines the speaker output sound signal S ER and the noise sound signal N introduced from the outside into the ear and outputs the synthesized sound signal S O to the microphone MIC 133.
  • the microphone (MIC, 133) are converts the synthesized sound signal (S O) to an electrical signal.
  • the second analog amplifiers A2 and 140 amplify an electric signal converted by the microphone MIC 133 and output the amplified electrical signal as the analog feedback signal A FB .
  • the microphone MIC 133 Since the microphone MIC 133 is located in the user's ear, it is assumed that the sound signal detected by the microphone MIC 133 is substantially the same as the sound signal input to the ear drum of the user.
  • FIG. 2 is a conceptual diagram for calculating a transfer function in the conventional analog active noise reduction (ANC) earphone shown in FIG.
  • ANC active noise reduction
  • the analog difference signal A ER is an electrical signal of the speaker output sound signal S ER , which is an acoustic signal generated by sequentially passing through the first analog amplifiers A1 and 120 and the earphone speaker SP and 131.
  • a transfer function for the analog difference signal A ER is called A 11 (s)
  • the synthesized acoustic signal SO which is an acoustic signal
  • the microphone MIC and the second analog amplifier A2 Speaking 140) for the transfer function for the electrical signals of the said composite acoustic signal of the analog feedback signal (a FB) (s O) is generated through a 22 turn (s)
  • the acoustic signal delivered to the user's ear drum synthesizing a sound signal (S O) is expressed by equation 1 below.
  • Equation 1 if the product of loop gain A 11 (s) and A 22 (s) is sufficiently larger than 1, the noise acoustic signal N is 1 / ⁇ A 11 (s) * A 22 (s ) ⁇ Is multiplied and greatly attenuated to the user's eardrum.
  • the analog audio input signal (A IN ) that you want to listen to is delivered relatively multiplied by the gain of 1 / A 22 (s). do.
  • the analog audio input signal (A IN) analog subtractor 110 in FIG. 1 Prior to applying the gain attenuation phenomena (1 / A 22 (s)) is, the analog audio input signal (A IN) analog subtractor 110 in FIG. 1 with respect to the analog audio input signal (A IN) A 22 After passing through the analog amplifier having a gain of (s) or greater, the analog subtractor 110 can be compensated for. If the loop gain is much smaller than 1 ( ⁇ 0), the noise acoustic signal N is multiplied by 1 and transmitted to the user's eardrum so that the noise acoustic signal is not attenuated.
  • the conventional analog active noise reduction (ANC) earphone shown in FIG. 1 has an advantage that the loop latency is short and thus attenuates noise noise signals in a relatively high frequency band.
  • the loop delay time is a time required for a signal starting from one point of the feedback loop to reach the same point by turning around the feedback loop.
  • the analog active noise reduction (ANC) earphone has a wide frequency range capable of attenuating noise sound by keeping the loop gain (A 11 (s) * A 22 (s)) large because the loop delay time is short. There is this.
  • the gain of the microphone MIC and the earphone speaker SP is small so that the loop gain value is very small ( ⁇ 0), so that the analog active noise reduction (ANC) earphone Does not attenuate the noise sound.
  • the analog active noise reduction (ANC) earphone works well with respect to a noise acoustic signal having a frequency included in a band from 50 Hz to a maximum frequency to attenuate the noise acoustic signal.
  • the maximum frequency is determined by the loop delay time and the frequency stability of the loop.
  • FIG 3 is a conceptual diagram of a conventional digital active noise reduction (ANC) earphone.
  • the conventional digital active noise reduction earphone 300 includes a digital subtractor 310, a digital-to-analog converter DAC1 and 320, a first analog amplifier A1 and 330, and an acoustic signal generator 340. And second analog amplifiers A2 and 350 and analog to digital converters ADC 360.
  • the analog audio input signal A IN and the analog subtractor 110 are respectively the digital audio input signal D. IN ) and the digital subtractor 310
  • the first analog amplifier A1 of FIG. 1 is replaced by a series connection of the digital-to-analog converters DAC1 and 320 and the first analog amplifiers A1 and 330.
  • the second analog amplifier A2 of FIG. 1 has been replaced by a series connection of the second analog amplifiers A2 and 350 and the analog-to-digital converters ADC 360.
  • a series connection between the digital-to-analog converters DAC1 and 320 and the first analog amplifiers A1 and 330 is performed in order to increase the efficiency of converting an electrical signal into an acoustic signal. It can be replaced by a series connection of -D amplifier and LC lowpass filter.
  • the analog-to-digital converter (ADC, 360) is usually delta to convert the analog feedback signal (A FB ), which is the output signal of the second analog amplifier (A2, 350) into a pulse code modulation (PCM) two-level digital code.
  • a FB analog feedback signal
  • PCM pulse code modulation
  • the decimation filter also called a date rate converter, receives a high speed data output from the delta-sigma modulator and outputs a low speed PCM two-level digital code, from input to output.
  • the latency of the signal is about 0.5ms, which occupies most of the loop delay time of the digital ANC earphone shown in FIG.
  • a microphone MIC the second analog amplifier A2, the analog-to-digital converter ADC, the digital subtractor, the digital-to-analog converter DAC1, and the first analog amplifier A1 may be used.
  • the digital active noise reduction (ANC) earphone circuit performs a stable operation with a phase margin of 90 degrees without oscillation.
  • the loop gain value is increased only for the frequency band of 50 Hz to 500 Hz, and the loop gain value is smaller than 1 for the frequency band of 500 Hz or more to ensure frequency stability. The rash can be prevented. Therefore, in such a case, the noise noise belonging to the frequency band of 50Hz to 500Hz is generally attenuated well and transmitted to the user's eardrum, and the high frequency noise sound of 500Hz or more is not attenuated and transmitted to the user's eardrum.
  • the technical problem to be solved by the present invention is to reduce the loop delay time by using a three-level pulse width modulation (PWM) signal or a three-level pulse density modulation (PDM) signal, thereby enabling active in earphones that receive digital audio signals. It is to provide an active noise reduction earphone using a three-level digital signal that can increase the frequency range that can be active noise canceling.
  • PWM pulse width modulation
  • PDM pulse density modulation
  • the active noise reduction earphone using a three-level digital signal receives one digital audio input signal D IN and receives a first two-level digital signal P IN that is a PWM signal.
  • a digital-input PWM signal converter for outputting;
  • a three-level PWM signal generator that receives the first two-level digital signal P IN and the second two-level digital signal P FB , which are PWM signals, and outputs one single-level digital signal P ER .
  • An amplifier A3 receiving the 3-level digital signal and amplifying the 3-level digital signal;
  • a low pass filter for performing low pass filtering on the output signal of the amplifier; It is connected to the output terminal of the low pass filter and converts the output signal of the low pass filter to an acoustic signal (S ER ) and adds it with the noise acoustic signal (N) to output a synthesized acoustic signal (S O ), which is then converted into an electrical signal.
  • a synthesized sound signal generation unit for converting the signal into a signal;
  • An analog amplifier (A2) for amplifying an electrical signal output from the synthesized acoustic signal generator and outputting the analog signal as an analog feedback signal (A FB );
  • an analog-input PWM signal converter configured to receive the analog feedback signal and output the second two-level digital signal, wherein the three-level PWM signal generator, the amplifier, the low pass filter, and the synthesized sound signal.
  • the feedback loop composed of the generation unit, the analog amplifier, and the analog-input PWM signal converter may perform a negative feedback operation.
  • the active noise reduction earphone using the three-level digital signal receives one digital audio input signal D IN and receives the first two-level digital signal P IN that is a PDM signal.
  • a digital-input PDM signal converter for outputting;
  • a three-level PDM signal generator which receives the first two-level digital signal PIN and the second two-level digital signal P FB which are PDM signals and outputs one three-level digital signal P ER ;
  • An amplifier A3 receiving the 3-level digital signal and amplifying the 3-level digital signal;
  • a low pass filter for performing low pass filtering on the output signal of the amplifier;
  • a synthesized acoustic signal generation unit connected to the output terminal of the low pass filter and converting the output signal of the low pass filter into an acoustic signal and then adding the noise acoustic signal and outputting a synthesized acoustic signal to convert it into an electrical signal;
  • An analog amplifier (A2) for amplifying an electrical signal output from the synthesized acoustic
  • the synthesized sound signal generation unit is connected to an output terminal of the low pass filter and converts an output signal of the low pass filter to output a speaker output sound signal.
  • the amplifier is preferably a class-D type amplifier.
  • the class-D amplifier receives a three-level digital signal P ER and outputs two analog signals through a first output terminal OP1 and a second output terminal OM1, respectively, and the three-level amplifier.
  • the digital signal P ER has three kinds of values of +1, 0, and -1, and the first to sixth two-level digital intermediate signals GP1, from the one three-level digital signal P ER .
  • GN2, GP3, GN4, GP5, GN6 the first to sixth two-level digital intermediate signals
  • the class-D amplifier may include the first to sixth two-level digital intermediate signals GP1, GN2, GP3, GN4, GP5, and GN6 when the three-level digital signal P ER is +1. Has a value of logic levels '0', '0', '1', '1', '1', and '0', respectively, and when the three-level digital signal P ER is 0, the first To sixth two-level digital intermediate signals GP1, GN2, GP3, GN4, GP5, and GN6, respectively, of the logic levels '1', '0', '1', '0', '0', and '1'.
  • the first to sixth two-level digital intermediate signals GP1, GN2, GP3, GN4, GP5, and GN6 each have a logic level '. It has the values 1 ',' 1 ',' 0 ',' 0 ',' 1 'and' 0 '.
  • a drain, a source, a gate, and a substrate node may include the first output terminal OP1, the positive voltage supply terminal VDD, the first two-level digital intermediate signal GP1, and A first PMOS transistor MP1 connected to the positive voltage supply terminal VDD; A drain, a source, a gate, and a substrate node are respectively connected to the first output terminal OP1, the negative voltage supply terminal VSS, the second two-level digital intermediate signal GN2, and the negative voltage supply terminal VSS.
  • One fourth NMOS transistor MN4 connected; A drain, a source, a gate, and a substrate node are respectively connected to the second output terminal OM1, the first output terminal OP1, the fifth two-level digital intermediate signal GP5, and the positive voltage supply terminal VDD.
  • one sixth NMOS transistor MN6 coupled to it.
  • the speaker and the microphone are preferably located in the ear canal of the user.
  • the low pass filter LPF comprises: a first input terminal connected to a first output terminal OP1 of the class-D amplifier; A second input terminal connected to a second output terminal OM1 of the class-D amplifier; A first output terminal OP2 connected to the positive input terminal of the speaker; A second output terminal OM2 connected to a negative input terminal of the speaker; A first inductor LP connected between the first input terminal and the first output terminal OP2; A second inductor LM connected between the second input terminal and the second output terminal OM2; A first storage battery CP connected between the first output terminal OP2 and a negative voltage supply terminal VSS; And a second storage battery CM connected between the second output terminal OM2 and the negative voltage supply terminal VSS.
  • the first storage battery CP and the second storage battery CM may be replaced with one storage battery connected between the first output terminal OP2 and the second output terminal OM2.
  • the analog-input PWM signal converter converts the differential signal of the analog feedback signal A FB and the differential signal of the reference analog signal A REF . It may be configured as a comparator that receives the input and outputs the second two-level digital signal (P FB ). In this case, when the value of the analog feedback signal A FB is greater than the value of the reference analog signal A REF , the second two-level digital signal P FB becomes a logic level '1'. When the value of the analog feedback signal A FB is less than or equal to the value of the reference analog signal A REF , the second two-level digital signal P FB becomes a logic level '0'.
  • Active noise reduction earphones using a three-level digital signal according to the invention can also be used in hearing aids or personal acoustic amplifiers.
  • the loop delay time which is the time taken for the signal to travel one cycle along the feedback loop, is less than 0.0001 sec. It is preferable.
  • the three-level PWM signal generator and the three-level PDM signal generator are configured for the second two-level digital signal in the first two-level digital signal.
  • the result of subtracting the signal is output as the 3-level digital signal P ER .
  • the electrical signal output by the microphone is preferably a differential signal.
  • an active noise reduction earphone using a three-level digital signal in a digital active noise reduction earphone, a loop using a three-level pulse width modulation (PWM) signal or a three-level pulse density modulation (PDM) signal is used.
  • PWM pulse width modulation
  • PDM three-level pulse density modulation
  • FIG. 1 is a conceptual diagram of a conventional analog active noise reduction earphone.
  • FIG. 2 is a conceptual diagram for calculating a transfer function in a conventional analog active noise reduction earphone.
  • FIG. 3 is a conceptual diagram of a conventional digital active noise reduction earphone.
  • FIG. 4 is a diagram illustrating an embodiment of an active noise reduction earphone using a three-level digital signal according to the present invention.
  • FIG. 5 is a diagram illustrating another embodiment of an active noise reduction earphone using a three-level digital signal according to the present invention.
  • FIG. 6 is a diagram for describing an operation of the 3-level PWM signal generator of FIG. 4 and the PDM signal generator of FIG. 5.
  • FIG. 7 is a circuit diagram illustrating a connection relationship between a class-D type amplifier, a low pass filter, and a speaker in an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIGS. 4 and 5.
  • FIG. 8 is a circuit diagram illustrating a connection relationship between a microphone and a second analog amplifier in an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIGS. 4 and 5.
  • FIG. 9 is a diagram illustrating an analog-input PWM signal converter of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG. 4.
  • FIG. 10 is a diagram illustrating waveforms of a reference analog signal shown in FIG. 9.
  • FIG. 11 is a diagram illustrating a digital-input PWM signal converter and a reference analog signal generating circuit of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG. 4.
  • FIG. 12 is a diagram illustrating a digital-input PDM signal converter of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG.
  • FIG. 4 is a diagram illustrating an embodiment of an active noise reduction earphone using a three-level digital signal according to the present invention.
  • the active noise reduction earphone 400 using a three-level digital signal includes a digital-input PWM signal converter 410, a three-level PWM signal generator 420, an amplifier A3, 430, a low pass filter 440, an acoustic signal generator 450, analog amplifiers A2 and 460, and an analog-input PWM signal converter 470.
  • the digital-input PWM signal converter 410 receives one digital audio input signal D IN and outputs a first two-level digital signal P IN that is a PWM signal.
  • the three-level PWM signal generator 420 receives the first two-level digital signal P IN and the second two-level digital signal P FB which are PWM signals and receive one three-level digital signal P ER.
  • Amplifiers A3 and 430 receive the three-level digital signal and amplify and output the digital signal.
  • the low pass filter 440 performs low pass filtering on the output signal of the amplifier.
  • Acoustic signal generator 450 is connected to the output terminal of the low pass filter and converts the output signal of the low pass filter into an acoustic signal, and then adds it with the noise acoustic signal to output a synthetic sound signal and converts it into an electrical signal and outputs do.
  • the analog amplifiers A2 and 460 amplify the electric signals output from the synthesized acoustic signal generator 450 and output the amplified electrical signals as analog feedback signals A FB .
  • the analog-input PWM signal converter 470 receives the analog feedback signal A FB and outputs the second two-level digital signal P FB .
  • the three-level PWM signal generator 420, the amplifier 430, the low pass filter 440, the synthesized acoustic signal generator 450, the analog amplifier 460 and the analog-input PWM signal The feedback loop consisting of the transducer 470 performs a negative feedback operation.
  • PWM pulse width modulation
  • ADC analog-to-digital converter
  • DAC1 digital-to-analog converter
  • the analog-to-digital converter (ADC) is replaced with an analog-input PWM converter 470,
  • the series connection of the digital-to-analog converter DAC1 and the first analog amplifier A1 is replaced by the series connection of one class-D type amplifier A3 and 430 and one low pass filter LPF and 440. .
  • the digital subtractor 310 is replaced by one three-level PWM generator 420, and the digital audio input signal D IN is converted into one PWM signal, the first two-level digital signal P IN .
  • a digital-input PWM converter (410) was added.
  • the digital audio input signal D IN is PCM 2-level digital data, but the PWM signal is used in the subtractor for negative feedback operation, and the decimation filter constituting the ADC 360 of FIG. 3 is removed.
  • the analog-input PWM signal converter 470 By using the analog-input PWM signal converter 470, the loop delay time is drastically reduced from 0.5 ms (1 / 2,000 seconds) to 0.1 ms (1 / 10,000 seconds).
  • the maximum frequency of the noise acoustic signal that can be attenuated was increased five times from 500 Hz to 2,500 Hz.
  • the three-level PWM generator 420 receives two first two-level digital PWM signals P IN and a second two-level digital signal P FB as inputs. Outputs one 3-level digital signal P ER , which is a signal.
  • the second two-level digital signal P FB is a two-level digital PWM signal output from the analog-input PWM signal converter 470.
  • the analog-input PWM signal converter 470 is a microphone (MIC, 453).
  • the analog feedback signal A FB and sawtooth wave reference analog signal A REF generated by amplifying the electric signal converted by the second analog amplifiers A2 and 460 are received as inputs, and the analog feedback is input.
  • the second two-level digital signal P FB is output at a logic level '1'.
  • the level digital signal P FB is output at a logic level '0'.
  • FIG. 5 is a diagram illustrating another embodiment of an active noise reduction earphone using a three-level digital signal according to the present invention.
  • the PWM signal is used in FIG. 5, whereas the PWM signal is used in FIG. 5.
  • the digital-input PWM signal converter 410 of FIG. 4, the analog-input PWM signal converter 470 and the three-level PWM signal generator 420 of FIG. 5 are respectively a digital-input PDM signal converter 510, Replaced by analog-input delta-sigma modulator 570 and three-level PDM signal generator 520.
  • the loop delay time is substantially the same as the embodiment illustrated in FIG. 4, but the sawtooth waveform analog reference input to the analog-input PWM signal converter 470 of FIG. 4 is used. Since the signal A REF does not need to be generated and the analog signal is sensitive to noise, the embodiment shown in FIG. 5 has a strong advantage over noise than the embodiment shown in FIG. 4.
  • the three-level PWM signal generator 420 of FIG. 4 receives the two two-level digital PWM signals, the first two-level digital signal P IN and the second two-level digital signal P FB , as inputs. Generate one 3-level digital signal P ER that is a signal. Meanwhile, the three-level PDM signal generator 520 of FIG. 5 receives two two-level digital PDM signals, a first two-level digital signal P IN and a second two-level digital signal P FB as inputs. And generates one 3-level digital signal P ER that is a PDM signal.
  • the three-level PWM signal generator 420 of FIG. 4 and the three-level PDM signal generator 520 of FIG. 5 have two two-level digital signals, except that the modulation schemes of the signals are different from each other using PWM and PDM. It takes the same role to generate one 3-level signal as an input. Accordingly, the three-level PWM signal generator 420 and the three-level PDM signal generator 520 perform the same logic operation as shown in Equation 2, and thus, at the first two-level digital signal P IN value. The result of subtracting the second two-level digital signal P FB is output as a three-level digital signal P ER .
  • FIG. 6 is a diagram for describing an operation of the 3-level PWM signal generator of FIG. 4 and the 3-level PDM signal generator of FIG. 5.
  • the table shown in FIG. 6 is a table showing a logic operation according to equation (2).
  • one three-level (ternary) digital signal P ER is represented as three two-level digital signals PLUS, ZERO, and MINUS.
  • FIG. 7 is a circuit diagram illustrating a connection relationship between a class-D type amplifier, a low pass filter, and a speaker in an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIGS. 4 and 5.
  • the class-D type amplifier A3 receives one 3-level digital signal P ER as an input and receives two analog signals from the first output terminal OP1 and the second output terminal ( Output to OM1).
  • the three-level digital signal P ER is represented by three two-level digital signals PLUS, ZERO, and MINUS.
  • Conventional class-D amplifier is a amplifier that receives a PWM or PDM signal as an input and drives a speaker. Therefore, the class-D amplifier has a high efficiency of converting an electrical signal into an acoustic signal and is used in an output stage of an audio amplifier.
  • Conventional class-D amplifiers consist of two digital CMOS inverters and two LC lowpass filters, one CMOS inverter and one CMOS inverter with logic level values. It receives these different complementary two-level digital input signals.
  • the connection with the LC lowpass filter (LPF) is the same as that of the conventional class-D amplifier, but the conventional class-D amplifier is two-level digital complementary to each other.
  • Class-D amplifiers according to the present invention differ from each other in that they receive one 3-level digital signal (P ER ) as input.
  • the three-level digital signal P ER is a three-level digital signal having three kinds of values of +1, 0, and -1, and three two-level digital signals PLUS, ZERO, and MINUS are illustrated in FIG. Is shown.
  • CMOS complementary metal-oxide-semiconductor
  • the class-D amplifier A3 includes three two-level two-level digital digital input terminals of PLUS, ZERO, and MINUS, two of a first output terminal OP1 and a second output terminal OM1. With three analog output terminals, first to sixth two-level digital intermediate signals GP1, GN2, GP3, GN4, GP5, and GN6 are generated from the three digital input terminals.
  • the first to sixth two-level digital intermediate signals GP1 may be used.
  • GN2, GP3, GN4, GP5, GN6 have logic levels '0', '0', '1', '1', '1' and '0'.
  • the first to sixth two-level digital intermediate signals GP1 and GN2 are used.
  • GP3, GN4, GP5, and GN6 have logic levels '1', '0', '1', '0', '0', and '1'.
  • the first to sixth two-level digital intermediate signals GP1, GN2, GP3, GN4, GP5, and GN6) have logic levels '1', '1', '0', '0', '1' and '0', respectively.
  • the class-D amplifier according to the present invention includes a first PMOS transistor MP1, a second NMOS transistor MN2, a third PMOS transistor MP3, a fourth NMOS transistor MN4, and a fifth PMOS transistor MP5. And a sixth NMOS transistor MN6.
  • the first PMOS transistor MP1 has a drain, a source, a gate, and a substrate node having the first output terminal OP1, a positive supply voltage terminal VDD, and the first two-level digital intermediate signal GP1. Is connected to the VDD.
  • a drain, a source, a gate, and a substrate node may respectively include the first output terminal OP1, a negative supply voltage terminal VSS, and the second two-level digital intermediate signal GN2. And the negative supply voltage terminal VSS.
  • a drain, a source, a gate, and a substrate node may respectively supply the second output terminal OM1, the positive supply voltage terminal VDD, the third two-level digital intermediate signal GP3, and a positive supply. It is connected to the voltage terminal VDD.
  • the fourth NMOS transistor MN4 has a drain, a source, a gate, and a substrate node having the second output terminal OM1, the negative supply voltage terminal VSS, the fourth two-level digital intermediate signal GN4, and the negative node, respectively. It is connected to the supply voltage terminal VSS.
  • the fifth PMOS transistor MP5 has a drain, a source, a gate, and a substrate node having the second output terminal OM1, the first output terminal OP1, the fifth two-level digital intermediate signal GP5, and the positive node, respectively. It is connected to the supply voltage terminal VDD.
  • a drain, a source, a gate, and a substrate node may respectively have the second output terminal OM1, the first output terminal OP1, the sixth two-level digital intermediate signal GN6, and the It is connected to the negative supply voltage terminal (VSS).
  • FIGS. 4 and 5 are circuit diagrams illustrating a connection relationship between a microphone and a second analog amplifier A2 in an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIGS. 4 and 5.
  • a resistor R having the same value is connected to two terminals of the microphone MIC, and among the two terminals of each resistor, to the microphone MIC.
  • the microphone MIC outputs a differential analog signal by connecting an unconnected terminal to a positive supply voltage VDD and a negative supply voltage VSS, respectively, and through the two capacitors, the second analog amplifier A2.
  • the second analog amplifier A2 outputs an analog feedback signal A FB , which is a differential analog signal, in connection with a differential input terminal of. It is preferable that the second analog amplifier A2 is implemented as a fully differential amplifier and can vary the voltage gain.
  • FIG. 9 is a diagram illustrating an analog-input PWM signal converter of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG. 4.
  • the analog-input PWM signal converter receives two differential analog signals, an analog feedback signal (A FB ) and a reference analog signal (A REF ) as inputs, and a two two-level digital PWM signal, a second two-level digital signal (P).
  • FB is printed.
  • the analog feedback signal A FB is an output signal of the second analog amplifier A2 and the reference analog signal A REF has a triangular waveform.
  • the second two-level digital signal P FB becomes a logic level '1', otherwise the second 2- The level digital signal P FB is at logic level '0'.
  • FIG. 10 is a diagram illustrating a waveform of the reference analog signal A REF illustrated in FIG. 9.
  • the waveform of the reference analog signal A REF is a triangular waveform having the same slew rate and falling slew rate with respect to time.
  • FIG. 11 is a diagram illustrating a digital-input PWM signal converter and a reference analog signal A REF generation circuit of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG. 4.
  • the digital-input PWM signal converter 410 of an active noise reduction earphone using a three-level digital signal is a digital audio input signal D IN and an up / down counter represented by a PCM code. Compare the output of the digital audio input signal (D IN ) is greater than the output value of the up / down counter (up / down counter), the first two-level digital signal (P IN ) value of the logic level '1 Otherwise, the value of the first two-level digital signal P IN becomes a logic level '0'.
  • the reference analog signal A REF shown in FIG. 10 is generated by applying the output value of the up / down counter to the digital-to-analog converter DAC2.
  • FIG. 12 is a diagram illustrating a digital-input PDM signal converter of an active noise reduction earphone using a three-level digital signal according to the present invention shown in FIG.
  • the input digital audio input signal (D IN ) is usually 16 bit 2-level digital PCM data of 44.1kS / sec, with the first stage increasing the sampling rate, the second stage performing the digital lowpass filter operation, and the third stage.
  • the digital delta-sigma modulation operation is performed to output a first two-level digital signal P IN that is a one-bit two-level digital PDM data value.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)

Abstract

La présente invention concerne un écouteur suppresseur de bruit actif utilisant un signal numérique à 3 niveaux, l'écouteur réduisant un temps de retard de boucle à l'aide d'un signal de modulation de largeur d'impulsion (PWM) à 3 niveaux ou d'un signal de modulation de densité d'impulsion (PDM) à 3 niveaux, ce qui permet d'augmenter une plage de fréquences apte à supprimer le bruit actif dans l'écouteur recevant un signal audio numérique. L'écouteur suppresseur de bruit actif utilisant le signal numérique à 3 niveaux, selon la présente invention, permet de réduire un temps de retard de boucle dans un écouteur suppresseur de bruit actif numérique à l'aide du signal PWM à 3 niveaux ou du signal PDM à 3 niveaux, ce qui permet d'augmenter la fréquence maximale apte à l'atténuation du signal sonore de bruit à 500 Hz jusqu'à 2500 Hz.
PCT/KR2017/009119 2017-04-03 2017-08-22 Écouteur suppresseur de bruit actif utilisant un signal numérique à 3 niveaux Ceased WO2018186540A1 (fr)

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KR1020170043178A KR101758708B1 (ko) 2017-04-03 2017-04-03 3-레벨의 디지털 신호를 사용하는 액티브 노이즈 감소 이어폰

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JPH06161473A (ja) * 1992-11-16 1994-06-07 Honda Motor Co Ltd 能動振動騒音制御装置
KR20090061134A (ko) * 2007-12-11 2009-06-16 한양대학교 산학협력단 데이터 가중 평균화 알고리즘을 이용하는 디급 오디오증폭기
KR20120073103A (ko) * 2010-12-24 2012-07-04 소니 주식회사 음성 신호 출력 장치, 스피커 장치, 음성 출력 장치, 음성 신호 출력 방법
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