WO2002095936A1 - Audio output amplifier - Google Patents

Audio output amplifier Download PDF

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Publication number
WO2002095936A1
WO2002095936A1 PCT/JP2002/004755 JP0204755W WO02095936A1 WO 2002095936 A1 WO2002095936 A1 WO 2002095936A1 JP 0204755 W JP0204755 W JP 0204755W WO 02095936 A1 WO02095936 A1 WO 02095936A1
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WO
WIPO (PCT)
Prior art keywords
signal
voltage
audio
signal line
output
Prior art date
Application number
PCT/JP2002/004755
Other languages
French (fr)
Japanese (ja)
Inventor
Mamoru Kitamura
Original Assignee
Niigata Seimitsu Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Niigata Seimitsu Co., Ltd. filed Critical Niigata Seimitsu Co., Ltd.
Publication of WO2002095936A1 publication Critical patent/WO2002095936A1/en

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/181—Low-frequency amplifiers, e.g. audio preamplifiers
    • H03F3/183—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only
    • H03F3/187—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only in integrated circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics

Definitions

  • the present invention relates to an audio output amplifier, for example, a head mounted in a portable electronic device capable of listening to sound by connecting a headphone.
  • portable players such as CDs (Compact Discs), MDs (Mini Discs), and DV Ds (Digital Video Discs), MP3s (MP EG Audio—Layer 3), ATRAC (Adaptive Transform Acoustic Coding), etc.
  • CDs Compact Discs
  • MDs Mini Discs
  • DV Ds Digital Video Discs
  • MP3s MP EG Audio—Layer 3
  • ATRAC Adaptive Transform Acoustic Coding
  • audio is often output through headphones connected to these devices.
  • PDAs Personal Digital Assistants
  • a DA converter and a headphone amplifier are used to convert the reproduced digital audio data into an analog signal and output the analog signal to the headphone.
  • FIG. 1 is a diagram showing a configuration example of a conventional DA converter and headphone amplifier.
  • FIG. 1 shows a configuration for converting 1-bit digital audio data described below into an analog audio signal and outputting the analog audio signal.
  • the 1-bit method uses ⁇ modulation to control the distribution of quantization noise, thereby improving the resilience of digital data to the original analog signal compared to the widely used PCM method. This method has attracted particular attention recently.
  • a DA converter includes a digital interface (I / F) 1, a digital filter 2, and a demodulation processing unit 3.
  • a headphone amplifier is configured by including drynos 4 and 5, coils LI and L3, capacitors CI, C3, C4 and C5, and resistors Rl and R3.
  • the DA converter generates a modulation signal based on digital audio data reproduced from a digital recording medium such as a CD.
  • a headphone amplifier connected to the latter stage of the DA converter is driven based on this modulated signal, and obtains an amplified analog audio signal by flowing a current corresponding to the pulse width of the modulated signal. .
  • the digital IZF 1 inputs a digital 1-bit signal reproduced from a digital recording medium (not shown) or the like.
  • the digital filter 2 performs low-pass filter processing on the 1-bit signal input by the digital I / F 1, and outputs the result to the ⁇ modulation processing unit 3.
  • the ⁇ modulation processing unit 3 performs a conversion process based on the ⁇ modulation on the signal output from the digital filter 2 to generate a modulated signal.
  • the drivers 4 and 5 drive based on the modulation signal output from the ⁇ modulation processing unit 3 and output an amount of current according to the pulse width of the modulation signal.
  • One driver 4 is in charge of the left (L) channel of the stereo sound
  • the other driver 5 is in charge of the right (R) channel of the stereo sound.
  • These drivers 4 and 5 are composed of switching amplifiers (inverting amplifiers) using pM ⁇ S transistors and nMOS transistors.
  • the power supply unit 6 supplies a power supply voltage to the digital I / F 1, digital filter 2, ⁇ ⁇ modulation processing unit 3, and drivers 4 and 5.
  • the digital I / F 1, digital filter 2, and ⁇ ⁇ modulation processing unit 3 that constitute the DA converter are supplied with the digital power supply voltage (VDD, ND) and the analog power supply voltage (VCC, A GND) to the drivers 4 and 5 that constitute the headphone amplifier.
  • VDD, ND digital power supply voltage
  • VCC, A GND analog power supply voltage
  • the power supplied to these circuits from the power supply unit 6 is obtained from a battery (not shown). .
  • the coil L 1 and the capacitor C 1 constitute a single-pass filter for the L channel, and the coil L 3 and the capacitor C 3 constitute a single-pass filter for the R channel. Also, the resistor R 1 forms a bias circuit for the L channel, and the resistor R 3 forms a bias circuit for the R channel.
  • the left and right analog audio signals generated by passing through these low-pass filters are output from the output terminal 11 via the capacitors C 4 and C 5, respectively.
  • Headphones that are widely used today have three signal lines (L channel, R channel, and ground).
  • the output terminal 11 also has three terminals 11a to l1c. ing.
  • the first terminal 11a is for the L channel
  • the second terminal lib is for the ground (GND)
  • the third terminal 11c is for the R channel.
  • the ground line connected to the second terminal 1 lb is commonly used by the left headphone 12 and the right headphone 13.
  • the output voltage When outputting audio signals from the left and right headphones 12 and 13, it is necessary to swing the output voltage to the headphones 12 and 13 positively and negatively around the ground zero voltage.
  • the power supply is a single DC power supply having neither plus nor minus like a battery used in a portable device, the output voltage is swung in a form biased to one side, for example, only the plus side. In this case, the output sound will be a crisp sound without bass.
  • the DC cut capacitor may be reduced in size, but it cannot be completely eliminated. This has been a factor that has hindered the reduction in size, weight, and cost of portable devices.
  • the present invention has been made to solve such a problem, and enables the output voltage to a headphone to swing positive and negative without using a capacitor for DC cut.
  • the aim is to reduce the size, weight, and cost of electronic devices. Disclosure of the invention
  • An audio output amplifier includes: a first signal line to which an audio signal is supplied; and a second signal to which a reference signal used to output a difference between the first signal line and the audio signal to an audio output unit is supplied. And an intermediate voltage generating circuit for generating an intermediate voltage of a power supply voltage used for amplifying the audio signal of the first signal line, and applying the intermediate voltage as the reference signal of the second signal line. It is characterized by having.
  • a driver for amplifying an audio signal based on a power supply voltage and supplying the amplified signal to a first signal line, generating an intermediate voltage of the power supply voltage, and supplying a reference signal for the audio signal
  • an intermediate voltage generating circuit for applying the intermediate voltage to a second signal line for the second signal line.
  • the first signal line includes two signal lines for supplying at least two channels of audio signals, and a reference signal supplied to the second signal line. Is commonly used for the audio signals of the two channels supplied to the two signal lines.
  • the intermediate voltage generation circuit is configured using an operational amplifier.
  • the intermediate voltage generating circuit includes a voltage dividing circuit that divides the power supply voltage by approximately /, and an operational amplifier that operates using the divided voltage as an input.
  • the difference between the audio signal output to the first signal line and the reference signal output to the second signal line is obtained, for example, the sound of a headphone or the like. Sound is emitted from the output unit.
  • the output from (one power supply voltage / 2) to (+ power supply voltage / 2) is seen from the audio output unit. It operates as if the voltage swings positively or negatively. Therefore, the output voltage to the audio output unit can be positively and negatively varied without providing a DC cut capacitor on the first signal line to which the audio signal is supplied.
  • the impedance of the second signal line viewed from the audio output unit can be reduced to a negligible level. For this reason, it is possible to suppress the voltage fluctuation of the second signal line and always maintain the potential at the intermediate voltage.
  • FIG. 1 is a diagram showing a configuration of a conventional headphone amplifier.
  • FIG. 2 is a circuit diagram of a first embodiment implementing the audio output amplifier of the present invention.
  • FIG. 3 is a diagram illustrating a configuration example of a headphone amplifier.
  • FIG. 3 is a diagram showing the behavior of the output voltage as viewed from the headphones in the present embodiment.
  • FIG. 4 is a diagram illustrating a configuration example of a headphone amplifier according to a second embodiment that implements the audio output amplifier of the present invention.
  • FIG. 5 is a diagram illustrating a configuration example of a headphone amplifier according to a third embodiment that implements the audio output amplifier of the present invention.
  • FIG. 2 is a diagram showing a configuration example of a headphone amplifier according to the first embodiment in which the audio output amplifier of the present invention is implemented.
  • the configuration of the DA converter is also shown.
  • components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.
  • reference numeral 10 denotes an IC chip, which includes a digital I / F 1, a digital filter 2, a ⁇ modulation processing unit 3, drivers 4 and 5, which operate as a class D amplifier, a power supply unit 6, and a reference. It has a voltage generation circuit 7 and an operational amplifier 8 that operates as a class B amplifier.
  • the digital I / F 1 inputs a digital 1-bit signal reproduced from a digital recording medium (not shown) into the IC chip 10. At this time, the digital I / F 1 alternately inputs digital data for the L channel and digital data for the R channel in the form of serial data DIN.
  • a clock LRCK for distinguishing between L channel digital data and R channel digital data—evening, and L channel digital data. Also input clock BCK, etc., to synchronize overnight and digital data of the R channel.
  • the digital filter 2 performs low-pass filtering on the 1-bit signal input by the digital I / F 1 and outputs the result to the ⁇ modulation processing unit 3.
  • the ⁇ modulation processing unit 3 performs conversion processing based on ⁇ modulation on the signal output from the digital filter 2 and generates modulated signals.
  • the drivers 4 and 5 use the analog power supply voltage VCC to generate ⁇ Amplifies the L-channel and R-channel modulation signals output from the modulation processing unit 3 and outputs them to the first signal lines ⁇ UT L and ⁇ UTR, respectively.
  • One driver 4 is responsible for L channel audio
  • the other driver 5 is responsible for R channel audio.
  • These drivers 4 and 5 are composed of switching amplifiers using pMOS transistors and nMOS transistors.
  • the power supply unit 6 supplies a power supply voltage to the above-described digital IF 1, digital filter 2, ⁇ modulation processing unit 3, drivers 4 and 5, a reference voltage generation circuit 7 and an operational amplifier 8 described below.
  • the digital power supply voltage VDD, DGND
  • VCC, A GND analog power supply voltage
  • the battery 14 has the digital power supply voltage VDD and the analog power supply voltage VCC both set to 3.3 V.
  • Battery 15 has a digital power supply voltage VDD set to 3.3 V and an analog power supply voltage VCC set to 5 V. These two batteries 14 15 can be arbitrarily replaced and used. When a battery 15 having a large analog power supply voltage VCC is used, a higher output can be obtained because the amplitude of the amplified audio signal becomes larger.
  • the reference voltage generation circuit 7 consists of two resistors R, which are connected in series between the analog power supply voltage VCC and the analog ground AGND, and have the same resistance value, and one resistor R, It consists of a capacitor C connected in parallel with R. With such a configuration, the reference voltage generation circuit 7 generates an intermediate voltage (V CCZ 2), which is 12 potentials of the analog power supply voltage V CC, and outputs it to the plus terminal of the operational amplifier 8.
  • V CCZ 2 intermediate voltage
  • the operational amplifier 8 performs an amplifying operation based on the intermediate voltage generated by the reference voltage generating circuit 7, and operates as the reference signal for the audio signals of the L and R channels supplied to the first signal lines OUTL and OUTR. Is supplied to the second signal line COM. Since the output of the operational amplifier 8 is fed back to its own negative terminal, a constant intermediate voltage (V CC / 2) is always applied to the second signal line COM.
  • the reference voltage generating circuit 7 and the operational amplifier 8 constitute an intermediate voltage generating circuit of the present invention.
  • Coil L 1 and capacitor C 1 constitute a single-pass filter for L-channel audio signals
  • coil L 3 and capacitor C 3 constitute a low-pass filter for R-channel audio signals.
  • the resistors Rl, R2, and R3 constitute a bias circuit for an L-channel audio signal, a bias circuit for a reference signal, and a bias circuit for an R-channel audio signal, respectively.
  • the pulse signals output from the drivers 4 and 5 pass through the respective low-pass filters to become analog audio signals of the left and right channels, and are output to the left headphone 1 via the output terminals 11a and 11c. Output to 2 and right headphones 13.
  • the intermediate voltage signal for the reference signal is connected to the output terminal lib.
  • Output to both left and right headphones 12 and 13 The left headphone 12 outputs the difference between the L channel audio signal supplied from the output terminal 11a and the intermediate voltage reference signal supplied from the output terminal 1lb.
  • the right headphone 13 outputs the difference between the R channel audio signal supplied from the output terminal 11 c and the intermediate voltage reference signal supplied from the output terminal 1 lb.
  • VDD 2 VCC ⁇ VCC / 2
  • the left and right signals can be provided without providing a DC cut capacitor on the first signal lines OUT L and OUT R to which the audio signals of the L and R channels are supplied.
  • the output voltage to the headphones 12 and 13 can be changed to positive or negative. As a result, it is possible to omit a very large capacitor, which is required in the past, and to reduce the size, weight, and cost of a portable device.
  • the intermediate voltage (VCC / 2) of the reference signal used when outputting to the left and right headphones 12 and 13 based on the difference from the audio signals of the L and R channels is determined by the driver 4. Instead of the same switching amplifier as in Figs.
  • the operational amplifier 8 In this case, the impedance of the second signal line C ⁇ M can be made so small that it can be ignored when viewed from the left and right headphones 12 and 13.
  • a method of generating an intermediate voltage (VC CZ 2) by smoothing a 50% duty pulse output from the switching amplifier with an LC filter may be considered.
  • the IC chip 1 is connected from the second signal line COM. Since the impedance when looking at the 0 side becomes large, the output voltage to the second signal line COM fluctuates greatly due to the flowing current.
  • the separation between the L channel and the R channel is deteriorated, and there is a problem that one of the L and R channel audio signals is mixed into the other. Further, since the switching amplifier outputs a pulse, even if the signal is smoothed, a certain amount of noise is generated, and the inconvenience of deteriorating the SN also occurs.
  • the voltage fluctuation of the second signal line COM is suppressed, and the potential is always maintained at VCC / 2. be able to.
  • the separation between the L channel and the R channel and the SN can be kept good, and the output voltages to the left and right headphones 12 and 13 can be positively and negatively changed.
  • the operational amplifier 8 when used, much higher performance can be realized as compared with the case where the intermediate voltage is generated using a smoothing circuit such as an LC filter. Therefore, the configuration of the operational amplifier 8 is simple and good, and the operational amplifier 8 can be built in without increasing the chip area.
  • the output voltages to the left and right headphones 12 and 13 were varied positively and negatively in the range of —VC CZ 2 to + VCC / 2, and were varied in the range of —VCC to -10 VCC.
  • the output power is lower than before.
  • the sound that can be heard from the left and right headphones 12 and 13 with mobile phones such as C DZMD / D VD players, MP3 and ATRAC compatible mobile devices, mobile phones and PDAs It is enough if the output power is as good as the form. If desired, a higher output can be obtained by using the battery 15.
  • the second embodiment shows an example in which an amplifier used for a headphone amplifier is constituted only by a class B amplifier.
  • This second embodiment is applicable to both the PCM system and the 1-bit system.
  • FIG. 4 is a diagram illustrating a configuration example of a headphone amplifier according to the second embodiment.
  • 12 V is used as the analog power supply voltage V CC.
  • R 11 and R 12 are resistors for voltage division and have the same resistance value.
  • a capacitor C 21 is connected in parallel with the resistor R 12.
  • the operational amplifier 21 operates with the intermediate voltage V C C 2 generated by this voltage division as an input to the plus terminal.
  • the output of the operational amplifier 21 is fed back to its own negative terminal.
  • the operational amplifier 21 stably supplies the voltage of V CC 2-6 V.
  • the L-channel audio signal and the R-channel audio signal input from the signal lines INL and INR are input to the positive terminals of the operational amplifiers 22 and 23 via the DC cut capacitors CI 1 and C 12. Is done.
  • the input stages of the operational amplifiers 22 and 23 are provided with biasing resistors R 15 and R 16, respectively, so that the output signal of the operational amplifier 21 can be supplied to them. Has become.
  • bias resistors R15 and R16 have large resistance values (for example, 100 ( ⁇ ).
  • the positive terminals of the operational amplifiers 22 and 23 are set to high impedance. In this way, low-frequency audio signals can be passed without increasing the capacitance of the DC cut capacitors C 11 and C 12. In other words, the capacitances of the capacitors C 11 and C 12 need to be at most (eg, 0.1 // F).
  • the audio signals of the L and R channels amplified by the operational amplifiers 22 and 23 are input to the negative terminals of the operational amplifiers 24 and 26 of the next stage via the resistors R25 and R26.
  • These operational amplifiers 24 and 26 operate as inverting amplifiers, and output the amplified signals to the first signal lines OUT L and OUT R.
  • the audio signal output from each of the operational amplifiers 24 and 26 varies between 0 and 12 V according to the power supply voltage V CC supplied to the control terminal of each of the operational amplifiers 24 and 26.
  • the operational amplifier 25 operates using the intermediate voltage V C CZ 2 supplied from the operational amplifier 21 as an input to the plus terminal.
  • the headphone operates such that the output voltage varies between one VC CZ2 and ten VC CZ2 in the positive and negative directions. Therefore, the output voltage to the headphones can be changed to positive or negative without providing a DC cut capacitor on the first signal lines OUT L and OUT R to which the audio signals of the L and R channels are supplied. it can. This eliminates the need for very large capacitors that were previously required. This makes it possible to reduce the size, weight, and cost of portable devices.
  • the impedance of the second signal line COM can be made small enough to be ignored when viewed from the headphone.
  • the voltage fluctuation of the second signal line COM is suppressed, the separation between the L channel and the R channel can be maintained well, and the output voltage to the headphone can be properly adjusted. Can be shaken.
  • FIG. 5 is a diagram illustrating a configuration example of a headphone amplifier according to the third embodiment.
  • components having the same functions as the components shown in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.
  • two operational amplifiers 31 and 32 are used instead of the operational amplifier 25 shown in FIG.
  • the operational amplifier 31 operates with the output signal of the L-channel operational amplifier 24 as an input to the minus terminal.
  • the operational amplifier 32 operates using the output signal of the operational amplifier 26 for the R channel as an input to the minus terminal. That is, these operational amplifiers 31 and 32 also operate as inverting amplifiers.
  • the operational amplifier 24 outputs the L-channel audio signal fluctuated between 0 and 12 V to the signal line OUT L—, and the operational amplifier 31 outputs a signal having a phase equal to that of the output signal to the signal line OUT L—. Outputs the inverted L channel audio signal to signal line UTL +. In the present embodiment, the difference between the audio signals output to these signal lines OUTL— and OU TL + is calculated and output to the left headphone.
  • the operational amplifier 26 outputs the audio signal of the R channel fluctuated between 0 and 12 V to the signal line ⁇ UTR—, and the operational amplifier 32 has the same phase as the output signal to the signal line 0 UTR—. Outputs the inverted R channel audio signal to signal line 0 UTR +.
  • the difference between the audio signals output to these signal lines ⁇ UTR— and OUT R + is output to the right headphone.
  • the output voltage of one of the L-channel signal lines OUT L— Is the maximum of 12 V
  • the output voltage of the other signal line OU TL + is 0 V
  • the difference voltage applied to the left headphone is 12 V.
  • the output voltage of one signal line OUTL— is the minimum 0 V
  • the output voltage of the other signal line 0 UTL + is 12 V
  • the difference voltage applied to the left headphone is 112 V. Therefore, when viewed from the left headphone, it operates as if the output voltage fluctuates between 11 and 12 V (1 VCC to 10 VCC). This is the same for the right headphone.
  • the reference voltage generation circuit 7 or the voltage dividing resistors R 11 and R 12 are used as a configuration for generating the intermediate voltage of the power supply voltage VCC. It is not limited to this. That is, the present invention can be applied to any configuration capable of generating an intermediate voltage.
  • the voltage supplied to the second signal line COM is 1 Z2 like the analog power supply voltage VCC, but it is not exactly 1 Z 2. Is also good.
  • the voltage may be slightly offset to the GND side or the VCC side.
  • the headphone for stereo sound having two channels of L and R channels has been described.
  • the present invention is similarly applied to a headphone or earphone for monaural. It is possible to apply in the above-described embodiment, an example in which the left and right headphones 12 and 13 are provided has been described as an example. However, the present invention can be applied to an earphone having only one audio output unit.
  • the first to third embodiments are particularly preferable when applied to a portable electronic device which is desired to be small and light, but may be applied to a stationary electronic device. Needless to say.
  • the power supply voltage can be viewed from (one power supply voltage / 2) to (+ power supply voltage 2) ) Can be operated as if the output voltage was positive or negative.
  • the output voltage to the audio output unit can be changed to positive or negative without providing a DC cut capacitor on the first signal line to which the audio signal is supplied. Therefore, it is possible to omit a very large capacitor, which is conventionally required for outputting low-frequency sound, and to reduce the size, weight, and cost of electronic devices.
  • the impedance of the second signal line can be reduced to a negligible level as viewed from the audio output unit. This allows Voltage fluctuation of the second signal line can be suppressed, and the potential can be constantly maintained at the intermediate voltage. Therefore, when the present invention is applied to stereo sound having two channels, the left channel and the right channel, the separation and S / N of the left and right channels can be kept good, and the output of the left and right channels can be maintained. The voltage can be changed positively and negatively.
  • the present invention enables the output voltage to a headphone to swing positive and negative without using a DC cut capacitor, thereby reducing the size, weight, and cost of electronic devices.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Multimedia (AREA)
  • Amplifiers (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Headphones And Earphones (AREA)
  • Stereophonic Arrangements (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

An intermediate voltage of a power supply voltage used for amplification of an audio signal of a first signal line OUTL and OUTR is generated and this intermediate voltage is applied as a reference signal voltage to a second signal line COM. Thus, it is possible to operate the output voltage to swing between -VCC/2 and VCC/2. That is, without providing a capacitor for cutting off DC current on the first signal line OUTL and OUTR, it is possible to swing the output voltage to the headphones (12, 13) accurately to positive and negative values.

Description

音声出力アンプ Audio output amplifier
技術分野 Technical field
本発明は音声出力アンプに関し、 例えば、 ヘッ ドホンを接続して音声 を聞く ことができるようになされた携帯型の電子機器に備えられるへッ 明  The present invention relates to an audio output amplifier, for example, a head mounted in a portable electronic device capable of listening to sound by connecting a headphone.
ドホンアンプ等に用いて好適なものである。  It is suitable for use in a phone amplifier or the like.
細 l 書  Detailed book
背景技術 Background art
一般に、 CD (コンパク トディスク） 、 MD (ミニディスク） 、 DV D (デジタルビデオディスク） 等のポータブルプレーヤ、 M P 3 (MP E Gオーディオ—レイヤ 3 ) や AT RA C (Adaptive Transform Acoust ic Coding) などの圧縮方式に対応した携帯オーディオ機器、 携帯電話や P D A (Personal Digital Assistants) などのモパイル機器等において は、 これらの機器に接続したへッ ドホンを通して音声を出力するように なされていることが多い。 この場合、 再生されたデジタルのオーディオ データをアナログ信号に変換してへッ ドホンに出力するために、 D Aコ ンバ一夕およぴへッ ドホンアンプが用いられる。  Generally, portable players such as CDs (Compact Discs), MDs (Mini Discs), and DV Ds (Digital Video Discs), MP3s (MP EG Audio—Layer 3), ATRAC (Adaptive Transform Acoustic Coding), etc. In portable audio devices, mobile phones and mobile devices such as PDAs (Personal Digital Assistants) that support the compression method, audio is often output through headphones connected to these devices. In this case, a DA converter and a headphone amplifier are used to convert the reproduced digital audio data into an analog signal and output the analog signal to the headphone.
図 1 は、 従来の D Aコンバータおよびへッ ドホンアンプの構成例を示 す図である。 この図 1 は、 以下に述べる 1 ビッ ト方式のデジタルオーデ ィォデータをアナログオーディオ信号に変換して出力するための構成を 示したものである。 1 ビッ ト方式は、 Δ Σ変調を用いて量子化ノイズの 分布を制御することにより、 現在広範に用いられている P C M方式に比 ベて、 デジタルデータから元のアナログ信号への復元性を向上させた方 式であり、 特に最近注目を集めている。 図 1 において、 デジタルインタフェース ( I / F ) 1、 デジタルフィ ルタ 2および△ ∑変調処理部 3を備えて D Aコンパ一夕が構成される。 また、 ドライノ 4 , 5、 コイル L I , L 3、 コンデンサ C I , C 3 , C 4 , C 5、 抵抗 R l , R 3を備えてヘッ ドホンアンプが構成される。 FIG. 1 is a diagram showing a configuration example of a conventional DA converter and headphone amplifier. FIG. 1 shows a configuration for converting 1-bit digital audio data described below into an analog audio signal and outputting the analog audio signal. The 1-bit method uses ΔΣ modulation to control the distribution of quantization noise, thereby improving the resilience of digital data to the original analog signal compared to the widely used PCM method. This method has attracted particular attention recently. In FIG. 1, a DA converter includes a digital interface (I / F) 1, a digital filter 2, and a demodulation processing unit 3. Further, a headphone amplifier is configured by including drynos 4 and 5, coils LI and L3, capacitors CI, C3, C4 and C5, and resistors Rl and R3.
D Aコンバータは、 C Dなどのデジタル記録メディアから再生された デジタルオーディオデータをもとに変調信号を生成する。 D Aコンバー 夕の後段に接続されるへッ ドホンアンプは、 この変調信号に基づいて駆 動し、 当該変調信号のパルス幅に応じた量の電流を流すことにより、 増 幅されたアナログオーディオ信号を得る。  The DA converter generates a modulation signal based on digital audio data reproduced from a digital recording medium such as a CD. A headphone amplifier connected to the latter stage of the DA converter is driven based on this modulated signal, and obtains an amplified analog audio signal by flowing a current corresponding to the pulse width of the modulated signal. .
デジタル I Z F 1 は、 図示しないデジタル記録メディアなどから再生 されたデジタルの 1 ビッ ト信号を入力するものである。 デジタルフィル タ 2は、 デジタル I / F 1 により入力された 1 ビッ ト信号に対してロー パスフィルタ処理を行い、 その結果を Δ Σ変調処理部 3に出力する。 Δ ∑変調処理部 3は、 デジタルフィルタ 2より出力された信号に対して△ ∑変調に基づく変換処理を行い、 変調信号を生成する。  The digital IZF 1 inputs a digital 1-bit signal reproduced from a digital recording medium (not shown) or the like. The digital filter 2 performs low-pass filter processing on the 1-bit signal input by the digital I / F 1, and outputs the result to the ΔΣ modulation processing unit 3. The Δ∑ modulation processing unit 3 performs a conversion process based on the Δ∑ modulation on the signal output from the digital filter 2 to generate a modulated signal.
ドライバ 4 , 5 は、 Δ∑変調処理部 3より出力される変調信号に基づ いて駆動し、 当該変調信号のパルス幅に応じた量の電流を出力する。 一 方のドライバ 4は、 ステレオ音声の左 （L) チャンネルを担当するもの であり、 もう一方の ドライバ 5は、 ステレオ音声の右 （R) チャンネル を担当するものである。 これらの ドライバ 4 , 5は、 p M〇 S トランジ スタと n MO S トランジスタとを用いたスイ ッチングアンプ （反転アン プ） から構成される。  The drivers 4 and 5 drive based on the modulation signal output from the Δ∑ modulation processing unit 3 and output an amount of current according to the pulse width of the modulation signal. One driver 4 is in charge of the left (L) channel of the stereo sound, and the other driver 5 is in charge of the right (R) channel of the stereo sound. These drivers 4 and 5 are composed of switching amplifiers (inverting amplifiers) using pM〇S transistors and nMOS transistors.
電源供給部 6 は、 上述のデジタル I ノ F 1、 デジタルフィルタ 2、 Δ ∑変調処理部 3およびドライバ 4 , 5 に電源電圧を供給するものである 。 このとき、 D Aコンバータを構成するデジタル I /F 1 、 デジタルフ ィルタ 2および Δ∑変調処理部 3 にはデジタル電源電圧 （ V D D， D G N D ) を供給し、 ヘッ ドホンアンプを構成する ドライバ 4 , 5にはアナ ログ電 ¾電圧 （V C C , A GND) を供給する。 携帯型の電子機器の場 合、 電源供給部 6からこれらの各回路に供給する電源は、 図示しない電 池などから得る。 . The power supply unit 6 supplies a power supply voltage to the digital I / F 1, digital filter 2, Δ 処理 modulation processing unit 3, and drivers 4 and 5. At this time, the digital I / F 1, digital filter 2, and Δ 処理 modulation processing unit 3 that constitute the DA converter are supplied with the digital power supply voltage (VDD, ND) and the analog power supply voltage (VCC, A GND) to the drivers 4 and 5 that constitute the headphone amplifier. In the case of a portable electronic device, the power supplied to these circuits from the power supply unit 6 is obtained from a battery (not shown). .
コイル L 1およびコンデンサ C 1 は Lチャンネル用の口一パスフィル 夕を構成し、 コイル L 3およびコンデンサ C 3 は Rチャンネル用の口一 パスフィルタを構成する。 また、 抵抗 R 1 は Lチャンネル用のバイアス 回路を構成し、 抵抗 R 3は Rチャンネル用のバイアス回路を構成する。 これらのローパスフィルタを通過して生成された左右のアナログオーデ ィォ信号は、 それぞれコンデンサ C 4 , C 5 を介して出力端子 1 1から 出力される。  The coil L 1 and the capacitor C 1 constitute a single-pass filter for the L channel, and the coil L 3 and the capacitor C 3 constitute a single-pass filter for the R channel. Also, the resistor R 1 forms a bias circuit for the L channel, and the resistor R 3 forms a bias circuit for the R channel. The left and right analog audio signals generated by passing through these low-pass filters are output from the output terminal 11 via the capacitors C 4 and C 5, respectively.
現在広く使われているヘッ ドホンは、 3つの信号線 （ Lチャンネル、 Rチャンネル、 グランド） を備えており、 これに対応して出力端子 1 1 も 3つの端子 1 1 a〜 l 1 c を備えている。 第 1 の端子 1 1 aは Lチヤ ンネル用、 第 2の端子 l i bはグランド （G N D) 用、 第 3の端子 1 1 c は Rチャンネル用である。 第 2の端子 1 l bに接続されるグランド線 は、 左ヘッ ドホン 1 2 と右ヘッ ドホン 1 3 とに共通に用いられる。  Headphones that are widely used today have three signal lines (L channel, R channel, and ground). Correspondingly, the output terminal 11 also has three terminals 11a to l1c. ing. The first terminal 11a is for the L channel, the second terminal lib is for the ground (GND), and the third terminal 11c is for the R channel. The ground line connected to the second terminal 1 lb is commonly used by the left headphone 12 and the right headphone 13.
オーディオ信号を左右のへッ ドホン 1 2 , 1 3から出力する際には、 ヘッ ドホン 1 2， 1 3への出力電圧を、 グラン ドのゼロ電圧を中心とし て正負に振る必要がある。 ところが、 携帯型機器に用いる電池のように 、 電源がプラスマイナスを持たない直流のシングル電源の場合には、 出 力電圧は例えばプラス側だけの片側にバイアスされた形で振られてしま う。 この場合の出力音声は、 低音が出ず、 キンキンした音になってしま う。  When outputting audio signals from the left and right headphones 12 and 13, it is necessary to swing the output voltage to the headphones 12 and 13 positively and negatively around the ground zero voltage. However, when the power supply is a single DC power supply having neither plus nor minus like a battery used in a portable device, the output voltage is swung in a form biased to one side, for example, only the plus side. In this case, the output sound will be a crisp sound without bass.
これを防ぐためには、 直流カッ ト用のコンデンサ C 4， C 5を設ける ことが必須となる。 しかしながら、 携帯型の電子機器に用いられるへッ ドホンのインピ一ダンスは一般的に十数 Ω〜数十 Ωと小さいため、 低い 周波数の低音をまともに出力するためには、 直流カツ ト用コンデンサ C 4， C 5の容量を数百 と大きく とらなければならない。 この場合、 コンデンサの外形は非常に大きなものとなってしまう。 To prevent this, it is essential to provide DC cut capacitors C4 and C5. However, the heads used in portable electronic devices Since the impedance of a phone is generally as small as several tens to several tens of ohms, the capacitance of the DC cut capacitors C4 and C5 must be increased to several hundreds in order to output a low-frequency low tone properly. Must take. In this case, the external shape of the capacitor becomes very large.
これを回避するために、 低い周波数の低音を増幅して直流カツ ト用コ ンデンザの容量を小さくする方法が一般的であるが、 この場合は周波数 特性を変化させるため、 音質の劣化はまぬがれない。 また、 この方法で は、 直流カッ ト用コンデンサも小型化の可能性はあるが、 完全に無くせ る訳ではない。 これにより、 携帯型機器の小型 ， 軽量化や低コス ト化等 を妨げる要因となっていた。  In order to avoid this, it is common to amplify low-frequency bass to reduce the capacity of the DC cut capacitor, but in this case, the frequency characteristics are changed, so the sound quality is inevitable . In this method, the DC cut capacitor may be reduced in size, but it cannot be completely eliminated. This has been a factor that has hindered the reduction in size, weight, and cost of portable devices.
本発明は、 このような問題を解決するために成されたものであり、 直 流カツ ト用のコンデンサを用いることなく、 へッ ドホンへの出力電圧を 正負に振ることができるようにし、 これによつて電子機器の小型 · 軽量 化および低コス ト化を図ることを目的としている。 発明の開示  The present invention has been made to solve such a problem, and enables the output voltage to a headphone to swing positive and negative without using a capacitor for DC cut. The aim is to reduce the size, weight, and cost of electronic devices. Disclosure of the invention
本発明の音声出力アンプは、 音声信号が供給される第 1の信号線と、 上記音声信号との差をとつて音声出力部に出力するために使用する基準 信号が供給される第 2の信号線とを有し、 上記第 1 の信号線の上記音声 信号の増幅に使用される電源電圧の中間電庄を生成し、 上記第 2の信号 線の上記基準信号として印加する中間電圧生成回路を備えたことを特徴 とする。  An audio output amplifier according to the present invention includes: a first signal line to which an audio signal is supplied; and a second signal to which a reference signal used to output a difference between the first signal line and the audio signal to an audio output unit is supplied. And an intermediate voltage generating circuit for generating an intermediate voltage of a power supply voltage used for amplifying the audio signal of the first signal line, and applying the intermediate voltage as the reference signal of the second signal line. It is characterized by having.
本発明の他の態様では、 電源電圧に基づき音声信号を増幅して第 1 の 信号線に供給するための ドライバと、 上記電源電圧の中間電圧を生成し 、 上記音声信号に対する基準信号を供給するための第 2の信号線に上記 中間電圧を印加する中間電圧生成回路とを備えたことを特徴とする。 本発明のその他の態様では、 上記第 1 の信号線は、 少なく とも 2チヤ ンネル分の音声信号を供給するための 2本の信号線を含み、 上記第 2の 信号線に供給される基準信号は、 上記 2本の信号線に供給される上記 2 チャンネル分の音声信号に対して共通に用いられることを特徴とする。 本発明のその他の態様では、 上記中間電圧生成回路は、 オペアンプを 用いて構成されることを特徴とする。 In another aspect of the present invention, a driver for amplifying an audio signal based on a power supply voltage and supplying the amplified signal to a first signal line, generating an intermediate voltage of the power supply voltage, and supplying a reference signal for the audio signal And an intermediate voltage generating circuit for applying the intermediate voltage to a second signal line for the second signal line. According to another aspect of the present invention, the first signal line includes two signal lines for supplying at least two channels of audio signals, and a reference signal supplied to the second signal line. Is commonly used for the audio signals of the two channels supplied to the two signal lines. In another aspect of the present invention, the intermediate voltage generation circuit is configured using an operational amplifier.
例えば、 上記中間電圧生成回路は、 上記電源電圧を略 1 / 2に分圧す る分圧回路と、 上記分圧された電圧を入力として動作するオペアンプと を備える。  For example, the intermediate voltage generating circuit includes a voltage dividing circuit that divides the power supply voltage by approximately /, and an operational amplifier that operates using the divided voltage as an input.
上記のように構成した本発明によれば、 第 1 の信号線に出力された音 声信号は、 第 2の信号線に出力された基準信号との差がとられて例えば ヘッ ドホン等の音声出力部から放音される。 このとき、 第 2の信号線上 には電源電圧の中間電圧が常に印加されているので、 音声出力部から見 れば、 （一電源電圧 / 2 ) 〜 （+電源電圧 / 2 ) の間で出力電圧が正負 に振れているように動作する。 したがって、 音声信号が供給される第 1 の信号線上に直流カツ ト用のコンデンサを設けなくても、 音声出力部へ の出力電圧をきちんと正負に振ることが可能となる。  According to the present invention configured as described above, the difference between the audio signal output to the first signal line and the reference signal output to the second signal line is obtained, for example, the sound of a headphone or the like. Sound is emitted from the output unit. At this time, since the intermediate voltage of the power supply voltage is always applied to the second signal line, the output from (one power supply voltage / 2) to (+ power supply voltage / 2) is seen from the audio output unit. It operates as if the voltage swings positively or negatively. Therefore, the output voltage to the audio output unit can be positively and negatively varied without providing a DC cut capacitor on the first signal line to which the audio signal is supplied.
また、 基準信号の中間電圧をオペアンプにより生成するようにした本 発明の他の特徴によれば、 音声出力部から見た第 2の信号線のインピー ダンスを無視できるほど小さくすることができる。 そのため、 第 2の信 号線の電圧変動を抑制し、 その電位を常に中間電圧に維持することが可 能となる。 図面の簡単な説明  Further, according to another feature of the present invention in which the intermediate voltage of the reference signal is generated by the operational amplifier, the impedance of the second signal line viewed from the audio output unit can be reduced to a negligible level. For this reason, it is possible to suppress the voltage fluctuation of the second signal line and always maintain the potential at the intermediate voltage. BRIEF DESCRIPTION OF THE FIGURES
図 1 は、 従来のへッ ドホンアンプの構成を示す図である。  FIG. 1 is a diagram showing a configuration of a conventional headphone amplifier.
図 2は、 本発明の音声出力アンプを実施した第 1 の実施形態によるへ ッ ドホンアンプの構成例を示す図である。 FIG. 2 is a circuit diagram of a first embodiment implementing the audio output amplifier of the present invention. FIG. 3 is a diagram illustrating a configuration example of a headphone amplifier.
図 3は、 本実施形態において、 ヘッ ドホンから見た出力電圧の動きを 示す図である。  FIG. 3 is a diagram showing the behavior of the output voltage as viewed from the headphones in the present embodiment.
図 4は、 本発明の音声出力アンプを実施した第 2の実施形態によるへ ッ ドホンアンプの構成例を示す図である。  FIG. 4 is a diagram illustrating a configuration example of a headphone amplifier according to a second embodiment that implements the audio output amplifier of the present invention.
図 5は、 本発明の音声出力アンプを実施した第 3の実施形態によるへ ッ ドホンアンプの構成例を示す図である。 発明を実施するための最良の形態  FIG. 5 is a diagram illustrating a configuration example of a headphone amplifier according to a third embodiment that implements the audio output amplifier of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
(第 1 の実施形態）  (First Embodiment)
まず、 本発明の第 1の実施形態を図面に基づいて説明する。  First, a first embodiment of the present invention will be described with reference to the drawings.
図 2は、 本発明の音声出力アンプを実施した第 1の実施形態によるへ ッ ドホンアンプの構成例を示す図である。 ここでは、 ヘッ ドホンアンプ 以外に、 D Aコンバータの構成も示している。 なお、 図 2 において、 図 1 に示した構成要素と同一の機能を有する構成要素には同一の符号を付 している。  FIG. 2 is a diagram showing a configuration example of a headphone amplifier according to the first embodiment in which the audio output amplifier of the present invention is implemented. Here, in addition to the headphone amplifier, the configuration of the DA converter is also shown. In FIG. 2, components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals.
図 2 ( a ) において、 1 0は I Cチップであり、 デジタル I / F 1 、 デジタルフィルタ 2 、 Δ Σ変調処理部 3 、 D級アンプとして動作する ド ライバ 4 , 5、 電源供給部 6、 基準電圧発生回路 7、 および B級アンプ として動作するオペアンプ 8を備えている。  In FIG. 2A, reference numeral 10 denotes an IC chip, which includes a digital I / F 1, a digital filter 2, a ΔΣ modulation processing unit 3, drivers 4 and 5, which operate as a class D amplifier, a power supply unit 6, and a reference. It has a voltage generation circuit 7 and an operational amplifier 8 that operates as a class B amplifier.
デジタル I ノ F 1は、 図示しないデジタル記録メディアなどから再生 されたデジタルの 1 ビッ ト信号を I Cチップ 1 0内に入力する。 このと き、 デジタル I / F 1 は、 Lチャンネル用のデジタルデータと Rチャン ネル用のデジタルデータとをシリアルデータ D I Nの形で交互に入力す る。 また、 Lチャンネルのデジタルデータと Rチャンネルのデジタルデ —夕とを見分けるためのクロック L R C K、 Lチャンネルのデジタルデ 一夕と Rチャンネルのデジタルデータとを同期させるためのクロック B C Kなども入力する。 The digital I / F 1 inputs a digital 1-bit signal reproduced from a digital recording medium (not shown) into the IC chip 10. At this time, the digital I / F 1 alternately inputs digital data for the L channel and digital data for the R channel in the form of serial data DIN. A clock LRCK for distinguishing between L channel digital data and R channel digital data—evening, and L channel digital data. Also input clock BCK, etc., to synchronize overnight and digital data of the R channel.
デジタルフィルタ 2は、 デジタル I / F 1 により入力された 1 ビッ ト 信号に対してローパスフィルタ処理を行い、 その結果を Δ∑変調処理部 3に出力する。 Δ Σ変調処理部 3は、 デジタルフィルタ 2より出力され た信号に対して Δ∑変調に基づく変換処理を行い、 変調信号を生成する ドライバ 4 , 5は、 アナログ電源電圧 V C Cを用いて、 △∑変調処理 部 3より出力される Lチャンネル用および Rチャンネル用の変調信号を 増幅し、 それぞれを第 1の信号線〇UT L， 〇U T Rに出力する。 一方 の ドライバ 4は、 Lチャンネルの音声を担当するものであり、 もう一方 の ドライゾ 5は、 Rチャンネルの音声を担当するものである。 これらの ドライバ 4 , 5は、 p MO S トランジスタと n M O S トランジスタとを 用いたスィ ツチングアンプから構成される。  The digital filter 2 performs low-pass filtering on the 1-bit signal input by the digital I / F 1 and outputs the result to the Δ∑ modulation processing unit 3. The ΔΣ modulation processing unit 3 performs conversion processing based on Δ∑ modulation on the signal output from the digital filter 2 and generates modulated signals. The drivers 4 and 5 use the analog power supply voltage VCC to generate Δ∑ Amplifies the L-channel and R-channel modulation signals output from the modulation processing unit 3 and outputs them to the first signal lines 〇UT L and 〇UTR, respectively. One driver 4 is responsible for L channel audio, and the other driver 5 is responsible for R channel audio. These drivers 4 and 5 are composed of switching amplifiers using pMOS transistors and nMOS transistors.
電源供給部 6は、 上述のデジタル I F 1、 デジタルフィルタ 2、 Δ ∑変調処理部 3およびドライバ 4 , 5 と、 以下に述べる基準電圧発生回 路 7およびオペアンプ 8に電源電圧を供給する。 このとき、 D Aコンパ —夕を構成するデジタル I /F 1、 デジタルフィルタ 2および Δ Σ変調 処理部 3 にはデジタル電源電圧 （VD D， D GN D) を供給し、 ヘッ ド ホンアンプを構成する ドライバ 4 , 5、 基準電圧発生回路 7およびオペ アンプ 8 にはアナログ電源電圧 （V C C , A GND) を供給する。  The power supply unit 6 supplies a power supply voltage to the above-described digital IF 1, digital filter 2, Δ∑ modulation processing unit 3, drivers 4 and 5, a reference voltage generation circuit 7 and an operational amplifier 8 described below. At this time, the digital power supply voltage (VDD, DGND) is supplied to the digital I / F 1, digital filter 2 and Δ 処理 modulation processing unit 3 that constitute the DA converter, and the driver that constitutes the headphone amplifier The analog power supply voltage (VCC, A GND) is supplied to 4, 5, the reference voltage generator 7 and the operational amplifier 8.
携帯型の電子機器の場合、 電源供給部 6から各回路に供給する電源は 、 電池 1 4あるいは 1 5から得る。 電池 1 4は、 デジタル電源電圧 VD Dとアナ口グ電源電圧 V C Cとが共に 3. 3 Vに設定されたものである 。 また、 電池 1 5は、 デジタル電源電圧 VD Dが 3. 3 V、 アナログ電 源電圧 V C Cが 5 Vに設定されたものである。 これら 2つの電池 1 4， 1 5は任意に交換して使用することが可能である。 アナログ電源電圧 V C Cが大きい電池 1 5 を用いた場合は、 増幅される音声信号の振幅が大 きくなるので、 より高出力を得ることが可能である。 In the case of a portable electronic device, power supplied to each circuit from the power supply unit 6 is obtained from the battery 14 or 15. The battery 14 has the digital power supply voltage VDD and the analog power supply voltage VCC both set to 3.3 V. Battery 15 has a digital power supply voltage VDD set to 3.3 V and an analog power supply voltage VCC set to 5 V. These two batteries 14 15 can be arbitrarily replaced and used. When a battery 15 having a large analog power supply voltage VCC is used, a higher output can be obtained because the amplitude of the amplified audio signal becomes larger.
基準電圧発生回路 7は、 図 2 ( b ) に示すように、 アナログ電源電圧 V C Cとアナログ用グランド A G N Dとの間に直列に接続された同じ抵 抗値の 2つの抵抗 R， と、 一方の抵抗 Rに並列に接続されたコンデン サ Cとから構成される。 基準電圧発生回路 7はこのような構成により、 アナログ電源電圧 V C Cの 1 2の電位である中間電圧 （V C C Z 2 ) を生成してオペアンプ 8のプラス端子に出力する。  As shown in Fig. 2 (b), the reference voltage generation circuit 7 consists of two resistors R, which are connected in series between the analog power supply voltage VCC and the analog ground AGND, and have the same resistance value, and one resistor R, It consists of a capacitor C connected in parallel with R. With such a configuration, the reference voltage generation circuit 7 generates an intermediate voltage (V CCZ 2), which is 12 potentials of the analog power supply voltage V CC, and outputs it to the plus terminal of the operational amplifier 8.
オペアンプ 8は、 上記基準電圧発生回路 7 により生成された中間電圧 に基づいて増幅動作し、 第 1 の信号線 O U T L , O U T Rに供給される L , Rチャンネルの音声信号に対する基準信号として、 上記中間電圧の 信号を第 2の信号線 C O Mに供給する。 オペアンプ 8の出力は自身のマ ィナス端子へとフィー ドバック入力されているので、 第 2の信号線 C O Mには、 常に一定の中間電圧 （ V C C / 2 ) が印加される。 上記基準電 圧発生回路 7およびオペアンプ 8 により本発明の中間電圧生成回路が構 成される。  The operational amplifier 8 performs an amplifying operation based on the intermediate voltage generated by the reference voltage generating circuit 7, and operates as the reference signal for the audio signals of the L and R channels supplied to the first signal lines OUTL and OUTR. Is supplied to the second signal line COM. Since the output of the operational amplifier 8 is fed back to its own negative terminal, a constant intermediate voltage (V CC / 2) is always applied to the second signal line COM. The reference voltage generating circuit 7 and the operational amplifier 8 constitute an intermediate voltage generating circuit of the present invention.
コイル L 1 およびコンデンサ C 1 は Lチャンネル音声信号用の口一パ スフィルタ、 コイル L 3およびコンデンサ C 3は Rチャンネル音声信号 用のローパスフィルタを構成する。 また、 抵抗 R l , R 2 , R 3はそれ ぞれ、 Lチャンネル音声信号用のバイアス回路、 基準信号用のバイアス 回路、 Rチャンネル音声信号用のバイアス回路を構成する。  Coil L 1 and capacitor C 1 constitute a single-pass filter for L-channel audio signals, and coil L 3 and capacitor C 3 constitute a low-pass filter for R-channel audio signals. The resistors Rl, R2, and R3 constitute a bias circuit for an L-channel audio signal, a bias circuit for a reference signal, and a bias circuit for an R-channel audio signal, respectively.
ドライバ 4 , 5より出力されたパルス信号は、 それぞれのローパスフ ィル夕を通過して L , Rチャンネルのアナログ音声信号となり、 出力端 子 1 1 a， 1 1 c を介して左へッ ドホン 1 2および右へッ ドホン 1 3 に 出力される。 また、 基準信号用の中間電圧の信号は、 出力端子 l i bを 介して左へッ ドホン 1 2および右へッ ドホン 1 3の双方に出力される。 左へッ ドホン 1 2は、 出力端子 1 1 aより供給される Lチャンネルの 音声信号と、 出力端子 1 l bより供給される中間電圧の基準信号との差 をとつて出力する。 また、 右ヘッ ドホン 1 3は、 出力端子 1 1 c より供 給される Rチャンネルの音声信号と、 出力端子 1 l bより供給される中 間電圧の基準信号との差をとつて出力する。 The pulse signals output from the drivers 4 and 5 pass through the respective low-pass filters to become analog audio signals of the left and right channels, and are output to the left headphone 1 via the output terminals 11a and 11c. Output to 2 and right headphones 13. The intermediate voltage signal for the reference signal is connected to the output terminal lib. Output to both left and right headphones 12 and 13 The left headphone 12 outputs the difference between the L channel audio signal supplied from the output terminal 11a and the intermediate voltage reference signal supplied from the output terminal 1lb. The right headphone 13 outputs the difference between the R channel audio signal supplied from the output terminal 11 c and the intermediate voltage reference signal supplied from the output terminal 1 lb.
以上のようにへッ ドホンアンプを構成した場合、 第 2の信号線 C〇 M には常に中間電圧 V C Cノ 2が印加されているので、 例えば Lチャンネ ルに最大の電圧 V C Cが印加されたときには、 左ヘッ ドホン 1 2から見 れば、 出力電圧が + V D Dノ 2 ( = V C C - V C C/ 2 ) だけプラス側 に振られたことになる。 また、 例えば Lチャンネルに最小のゼロポルト が印加されたときには、 左ヘッ ドホン 1 2から見れば、 出力電圧が— V D D / 2 (= 0 - V C C/ 2 ) だけマイナス側に振られたことになる。 すなわち、 図 3 に示すように、 左ヘッ ドホン 1 2からすれば、 一 V C C/ 2〜十 V C CZ 2の間で出力電圧が正負に振られているように動作 する。 このことは、 右ヘッ ドホン 1 3 についても同様である。 したがつ て、 本実施形態によれば、 L, Rチャンネルの音声信号が供給される第 1の信号線 O UT L , OUT R上に直流カツ ト用のコンデンサを設けな くても、 左右へッ ドホン 1 2 , 1 3への出力電圧を正負に振ることがで きる。 これにより、 従来は必須であった非常に大きなコンデンサを省略 することができ、 携帯型機器の小型 · 軽量化および低コス ト化を図るこ とができる。  When the headphone amplifier is configured as described above, since the intermediate voltage VCC 2 is always applied to the second signal line C 、 M, for example, when the maximum voltage VCC is applied to the L channel, From the viewpoint of the left headphone 12, the output voltage has been shifted to the positive side by + VDD 2 (= VCC−VCC / 2). For example, when the minimum zero port is applied to the L channel, when viewed from the left headphone 12, the output voltage is shifted by −V DD / 2 (= 0 −V C C / 2) to the minus side. That is, as shown in FIG. 3, from the left headphone 12, the operation is performed such that the output voltage varies between 1 Vcc / 2 and 10 Vccz 2. This is the same for the right headphone 13. Therefore, according to the present embodiment, the left and right signals can be provided without providing a DC cut capacitor on the first signal lines OUT L and OUT R to which the audio signals of the L and R channels are supplied. The output voltage to the headphones 12 and 13 can be changed to positive or negative. As a result, it is possible to omit a very large capacitor, which is required in the past, and to reduce the size, weight, and cost of a portable device.
また、 本実施形態では、 L， Rチャンネルの音声信号との差をとつて 左右へッ ドホン 1 2 , 1 3に出力する際に使用する基準信号の中間電圧 ( V C C / 2 ) を、 ドライバ 4， 5 と同様のスイッチングアンプではな く、 オペアンプ 8 により生成している。 このようにオペアンプ 8 を用い た場合は、 第 2の信号線 C〇 Mのインピーダンスを左右ヘッ ドホン 1 2 , 1 3から見て無視できるほど小さくすることができる。 In the present embodiment, the intermediate voltage (VCC / 2) of the reference signal used when outputting to the left and right headphones 12 and 13 based on the difference from the audio signals of the L and R channels is determined by the driver 4. Instead of the same switching amplifier as in Figs. Thus, using the operational amplifier 8 In this case, the impedance of the second signal line C〇M can be made so small that it can be ignored when viewed from the left and right headphones 12 and 13.
スィ ツチングアンプから出力されるデューティ 5 0 %のパルスを L C フィルタにより平滑化して中間電圧 （V C CZ 2 ) を生成する方法も考 えられるが、 この場合は、 第 2の信号線 C O Mから I Cチップ 1 0側を 見たときのインピ一ダンスが大きくなるため、 第 2の信号線 C O Mへの 出力電圧が、 流れる電流によって大きく変動してしまう。  A method of generating an intermediate voltage (VC CZ 2) by smoothing a 50% duty pulse output from the switching amplifier with an LC filter may be considered. In this case, the IC chip 1 is connected from the second signal line COM. Since the impedance when looking at the 0 side becomes large, the output voltage to the second signal line COM fluctuates greatly due to the flowing current.
そのため、 Lチャンネルと Rチャンネルとのセパレーショ ンが悪くな り、 L , Rチャンネルの音声信号の一方が他方に混入してしまう不都合 が生じる。 また、 スイ ッチングアンプではパルスを出力するので、 平滑 化したとしてもノイズがある程度は生じ、 S Nが悪くなつてしまうと いう不都合も生じる。  For this reason, the separation between the L channel and the R channel is deteriorated, and there is a problem that one of the L and R channel audio signals is mixed into the other. Further, since the switching amplifier outputs a pulse, even if the signal is smoothed, a certain amount of noise is generated, and the inconvenience of deteriorating the SN also occurs.
これに対して、 本実施形態のようにオペアンプ 8 を用いてリニアに増 幅動作を行う ことにより、 第 2の信号線 C O Mの電圧変動を抑制し、 そ の電位を常に V C C/ 2に維持することができる。 これにより、 Lチヤ ンネルと Rチャンネルとのセパレーシヨンや S Nを良好に保つことが できるとともに、 左右ヘッ ドホン 1 2， 1 3への出力電圧をきちんと正 負に振ることができる。  On the other hand, by performing the linear amplification operation using the operational amplifier 8 as in the present embodiment, the voltage fluctuation of the second signal line COM is suppressed, and the potential is always maintained at VCC / 2. be able to. As a result, the separation between the L channel and the R channel and the SN can be kept good, and the output voltages to the left and right headphones 12 and 13 can be positively and negatively changed.
このように、 オペアンプ 8を用いた場合は、 L Cフィルタ等の平滑化 回路を用いて中間電圧を生成する場合に比べて、 はるかに高い性能を実 現することができる。 したがって、 オペアンプ 8の構成は簡易で良く、 チップ面積を大きくすることなくオペアンプ 8 を内蔵することが可能で ある。  As described above, when the operational amplifier 8 is used, much higher performance can be realized as compared with the case where the intermediate voltage is generated using a smoothing circuit such as an LC filter. Therefore, the configuration of the operational amplifier 8 is simple and good, and the operational amplifier 8 can be built in without increasing the chip area.
なお、 本実施形態の場合、 左右ヘッ ドホン 1 2 , 1 3への出力電圧が — V C CZ 2〜 + V C C/ 2の範囲で正負に振られ、 — V C C〜十 V C Cの範囲で振られていた従来と比べると出力パワーが低下している。 し かし、 C DZMD/D VDプレーヤ、 M P 3や AT RA C対応の携帯ォ —ディォ機器、 携帯電話や P D Aなどのモパイル機器で左右へッ ドホン 1 2 , 1 3から聞く音に関しては、 本実施形態ほどの出力パワーがあれ ば十分である。 また、 希望する場合は、 電池 1 5 を用いることにより、 より大きな出力を得ることができる。 In the case of the present embodiment, the output voltages to the left and right headphones 12 and 13 were varied positively and negatively in the range of —VC CZ 2 to + VCC / 2, and were varied in the range of —VCC to -10 VCC. The output power is lower than before. I However, the sound that can be heard from the left and right headphones 12 and 13 with mobile phones such as C DZMD / D VD players, MP3 and ATRAC compatible mobile devices, mobile phones and PDAs It is enough if the output power is as good as the form. If desired, a higher output can be obtained by using the battery 15.
(第 2の実施形態） (Second embodiment)
次に、 本発明の第 2の実施形態について説明する。 第 2の実施形態は 、 へッ ドホンアンプに使用するアンプを B級アンプのみで構成した例を 示すものである。 この第 2の実施形態は、 P C M方式および 1 ビッ ト方 式の何れにも適用可能である。  Next, a second embodiment of the present invention will be described. The second embodiment shows an example in which an amplifier used for a headphone amplifier is constituted only by a class B amplifier. This second embodiment is applicable to both the PCM system and the 1-bit system.
図 4は、 第 2の実施形態によるへッ ドホンアンプの構成例を示す図で ある。 図 4では、 アナログ電源電圧 V C Cとして 1 2 Vを用いている。 R l l , R 1 2は分圧用の抵抗であり、 互いに等しい抵抗値を有してい る。 また、 抵抗 R 1 2 と並列にコンデンサ C 2 1が接続されている。 こ れにより、 抵抗 R 1 1， R 1 2の中間ノードには、 アナログ電源電圧 V C Cが 1 Z 2に分圧された中間電圧 V C C Z 2が現れる。  FIG. 4 is a diagram illustrating a configuration example of a headphone amplifier according to the second embodiment. In FIG. 4, 12 V is used as the analog power supply voltage V CC. R 11 and R 12 are resistors for voltage division and have the same resistance value. Also, a capacitor C 21 is connected in parallel with the resistor R 12. As a result, an intermediate voltage V CCZ 2 obtained by dividing the analog power supply voltage V CC into 1 Z 2 appears at an intermediate node between the resistors R 11 and R 12.
オペアンプ 2 1は、 この分圧により生成された中間電圧 V C C 2を プラス端子への入力として動作する。 このオペアンプ 2 1 の出力は自身 のマイナス端子へとフィードバック入力されている。 これにより、 オペ アンプ 2 1 は、 V C C 2 - 6 Vの電圧を安定して供給する。  The operational amplifier 21 operates with the intermediate voltage V C C 2 generated by this voltage division as an input to the plus terminal. The output of the operational amplifier 21 is fed back to its own negative terminal. As a result, the operational amplifier 21 stably supplies the voltage of V CC 2-6 V.
一方、 信号線 I N L , I N Rより入力された Lチャンネルの音声信号 および Rチャンネルの音声信号は、 直流カッ ト用のコンデンサ C I 1 , C 1 2 を介してオペアンプ 2 2 , 2 3のプラス端子に入力される。 各ォ ペアンプ 2 2 , 2 3の入力段には、 バイアス用の抵抗 R 1 5， R 1 6が 設けられており、 ここにオペアンプ 2 1の出力信号が供給されるように なっている。 On the other hand, the L-channel audio signal and the R-channel audio signal input from the signal lines INL and INR are input to the positive terminals of the operational amplifiers 22 and 23 via the DC cut capacitors CI 1 and C 12. Is done. The input stages of the operational amplifiers 22 and 23 are provided with biasing resistors R 15 and R 16, respectively, so that the output signal of the operational amplifier 21 can be supplied to them. Has become.
これらのバイアス抵抗 R l 5 , R 1 6 には、 大きな抵抗値のものを用 いる （例えば 1 0 0 Κ Ω) 。 このように、 各オペアンプ 2 2 , 2 3の入 力段に高抵抗のバイアス回路を設けることで、 オペアンプ 2 2 , 2 3の プラス端子をハイインピーダンスにする。 このようにすれば、 直流カツ ト用のコンデンサ C 1 1 , C 1 2 を大容量にしなくても、 低周波の音声 信号を通すことができる。 すなわち、 コンデンサ C 1 1， C 1 2の容量 は大きく とも (例えば 0. 1 // F) で済む。  These bias resistors R15 and R16 have large resistance values (for example, 100 （Ω). Thus, by providing a high-resistance bias circuit at the input stage of each of the operational amplifiers 22 and 23, the positive terminals of the operational amplifiers 22 and 23 are set to high impedance. In this way, low-frequency audio signals can be passed without increasing the capacitance of the DC cut capacitors C 11 and C 12. In other words, the capacitances of the capacitors C 11 and C 12 need to be at most (eg, 0.1 // F).
上記オペアンプ 2 2 , 2 3で増幅された L , Rチャンネルの音声信号 は、 抵抗 R 2 5， R 2 6 を介して次段のオペアンプ 2 4 , 2 6のマイナ ス端子に入力される。 これらのオペアンプ 2 4 , 2 6は反転アンプとし て動作し、 その増幅信号を第 1の信号線 OUT L , OUT Rに出力する 。 このとき、 各オペアンプ 2 4， 2 6 より出力される音声信号は、 各ォ ペアンプ 2 4， 2 6の制御端に供給される電源電圧 V C Cに従って 0〜 1 2 Vの間で振られる。  The audio signals of the L and R channels amplified by the operational amplifiers 22 and 23 are input to the negative terminals of the operational amplifiers 24 and 26 of the next stage via the resistors R25 and R26. These operational amplifiers 24 and 26 operate as inverting amplifiers, and output the amplified signals to the first signal lines OUT L and OUT R. At this time, the audio signal output from each of the operational amplifiers 24 and 26 varies between 0 and 12 V according to the power supply voltage V CC supplied to the control terminal of each of the operational amplifiers 24 and 26.
オペアンプ 2 5は、 上記オペアンプ 2 1 より供給される中間電圧 V C CZ 2 をプラス端子への入力として動作する。 このオペアンプ 2 5の出 力も自身のマイナス端子へとフィー ドバック入力されている。 これによ り、 オペアンプ 2 5は、 V C CZ 2 = 6 Vの中間電圧を第 2の信号線 C 0 Mに安定して供給する。  The operational amplifier 25 operates using the intermediate voltage V C CZ 2 supplied from the operational amplifier 21 as an input to the plus terminal. The output of the operational amplifier 25 is also fed back to its own minus terminal. Thereby, the operational amplifier 25 stably supplies an intermediate voltage of V C CZ 2 = 6 V to the second signal line C 0 M.
このように構成した場合、 第 1 の実施形態と同様に、 ヘッ ドホンから すれば、 一 V C CZ 2〜十 V C CZ 2 の間で出力電圧が正負に振られて いるように動作する。 したがって、 L， Rチャンネルの音声信号が供給 される第 1 の信号線 OUT L , OUT R上に直流カツ ト用のコンデンサ を設けなくても、 へッ ドホンへの出力電圧を正負に振ることができる。 これにより、 従来は必須であった非常に大きなコンデンサを省略するこ とができ、 携帯型機器の小型 · 軽量化および低コス ト化を図ることがで きる。 With this configuration, as in the first embodiment, the headphone operates such that the output voltage varies between one VC CZ2 and ten VC CZ2 in the positive and negative directions. Therefore, the output voltage to the headphones can be changed to positive or negative without providing a DC cut capacitor on the first signal lines OUT L and OUT R to which the audio signals of the L and R channels are supplied. it can. This eliminates the need for very large capacitors that were previously required. This makes it possible to reduce the size, weight, and cost of portable devices.
また、 本実施形態では、 オペアンプのみを用いているので、 第 2の信 号線 C O Mのィンピ一ダンスをへッ ドホンから見て無視できるほど小さ くすることができる。 これにより、 第 2の信号線 C OMの電圧変動を抑 制し、 Lチャンネルと Rチャンネルとのセパレーショ ンゃ S /Nを良好 に保つことができるとともに、 へッ ドホンへの出力電圧をきちんと正負 に振ることができる。  Further, in this embodiment, since only the operational amplifier is used, the impedance of the second signal line COM can be made small enough to be ignored when viewed from the headphone. As a result, the voltage fluctuation of the second signal line COM is suppressed, the separation between the L channel and the R channel can be maintained well, and the output voltage to the headphone can be properly adjusted. Can be shaken.
(第 3の実施形態） (Third embodiment)
次に、 本発明の第 3の実施形態について説明する。 この第 3の実施形 態も、 P C M方式および 1 ビッ ト方式の何れにも適用可能である。 図 5は、 第 3の実施形態によるへッ ドホンアンプの構成例を示す図で ある。 なお、 図 5において、 図 4に示した構成要素と同一の機能を有す る構成要素には同一の符号を付し、 重複する説明は省略する。  Next, a third embodiment of the present invention will be described. This third embodiment is also applicable to both the PCM system and the 1-bit system. FIG. 5 is a diagram illustrating a configuration example of a headphone amplifier according to the third embodiment. In FIG. 5, components having the same functions as the components shown in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.
図 5に示す第 3の実施形態では、 図 4に示したオペアンプ 2 5の代わ りに、 2つのオペアンプ 3 1， 3 2 を用いている。 オペアンプ 3 1は、 Lチャンネル用のオペアンプ 2 4の出力信号をマイナス端子への入力と して動作する。 また、 オペアンプ 3 2は、 Rチャンネル用のオペアンプ 2 6の出力信号をマイナス端子への入力として動作する。 つまり、 これ らのオペアンプ 3 1 , 3 2 も反転アンプとして動作する。  In the third embodiment shown in FIG. 5, two operational amplifiers 31 and 32 are used instead of the operational amplifier 25 shown in FIG. The operational amplifier 31 operates with the output signal of the L-channel operational amplifier 24 as an input to the minus terminal. The operational amplifier 32 operates using the output signal of the operational amplifier 26 for the R channel as an input to the minus terminal. That is, these operational amplifiers 31 and 32 also operate as inverting amplifiers.
オペアンプ 2 4は、 0〜 1 2 Vの間で振られた Lチャンネルの音声信 号を信号線 O UT L—に出力し、 オペアンプ 3 1 は、 信号線 OUT L— への出力信号と位相が反転した Lチャンネルの音声信号を信号線〇 U T L +に出力する。 本実施形態では、 これらの信号線 O U T L—， OU T L +に出力された音声信号の差をとつて左ヘッ ドホンに出力する。 また、 オペアンプ 2 6は、 0〜 1 2 Vの間で振られた Rチャンネルの 音声信号を信号線〇 U T R—に出力し、 オペアンプ 3 2は、 信号線 0 U T R—への出力信号と位相が反転した Rチャンネルの音声信号を信号線 0 U T R +に出力する。 本実施形態では、 これらの信号線〇 U T R—， OUT R +に出力された音声信号の差をとつて右ヘッ ドホンに出力する この場合、 例えば Lチャンネルの一方の信号線 OUT L—の出力電圧 が最大の 1 2 Vのときには他方の信号線 OU T L +の出力電圧は 0 Vと なり、 左ヘッ ドホンに与えられる差電圧は 1 2 Vとなる。 また、 一方の 信号線 O U T L—の出力電圧が最小の 0 Vのときには他方の信号線 0 U T L +の出力電圧は 1 2 Vとなり、 左ヘッ ドホンに与えられる差電圧は 一 1 2 Vとなる。 したがって、 左ヘッ ドホンからすれば、 一 1 2〜十 1 2 V (一 V C C〜十 V C C) の間で出力電圧が正負に振られているよう に動作する。 これは右へッ ドホンについても同様である。 The operational amplifier 24 outputs the L-channel audio signal fluctuated between 0 and 12 V to the signal line OUT L—, and the operational amplifier 31 outputs a signal having a phase equal to that of the output signal to the signal line OUT L—. Outputs the inverted L channel audio signal to signal line UTL +. In the present embodiment, the difference between the audio signals output to these signal lines OUTL— and OU TL + is calculated and output to the left headphone. The operational amplifier 26 outputs the audio signal of the R channel fluctuated between 0 and 12 V to the signal line 〇 UTR—, and the operational amplifier 32 has the same phase as the output signal to the signal line 0 UTR—. Outputs the inverted R channel audio signal to signal line 0 UTR +. In this embodiment, the difference between the audio signals output to these signal lines 〇 UTR— and OUT R + is output to the right headphone. In this case, for example, the output voltage of one of the L-channel signal lines OUT L— Is the maximum of 12 V, the output voltage of the other signal line OU TL + is 0 V, and the difference voltage applied to the left headphone is 12 V. Also, when the output voltage of one signal line OUTL— is the minimum 0 V, the output voltage of the other signal line 0 UTL + is 12 V, and the difference voltage applied to the left headphone is 112 V. Therefore, when viewed from the left headphone, it operates as if the output voltage fluctuates between 11 and 12 V (1 VCC to 10 VCC). This is the same for the right headphone.
以上のように、 第 3の実施形態によれば、 ヘッ ドホンへの出力端子が 4つ必要になって汎用性には欠けるが、 第 2の実施形態と比べて 2倍程 度の大きな出力パワーを得ることができるというメリ ッ トを有する。 なお、 上記第 1〜第 3の実施形態では、 電源電圧 V C Cの中間電圧を 発生するための構成として基準電圧発生回路 7 あるいは分圧用抵抗 R 1 1 , R 1 2 を用いたが、 本発明はこれに限定されるものではない。 すな わち、 中間電圧を発生できる構成であれば何れにも適用可能である。 また、 上記第 1および第 2の実施形態では、 第 2の信号線 C OMに供 給する電圧がアナログ電源電圧 V C Cのちよう ど 1 Z2の電圧としてい るが、 厳密に 1 Z 2でなくても良い。 すなわち、 所望の最大振幅電圧以 上を得ることができれば、 G N D側あるいは V C C側に多少片寄ってい ても良い。 また、 上記第 1 〜第 3の実施形態では、 L , Rチャンネルの 2チャン ネルを持つステレオ音声対応のへッ ドホンについて説明したが、 モノラ ル対応のヘッ ドホンあるいはイヤホン等にも同様に本発明を適用するこ とが可能である。 また、 上記実施形態では左右のヘッ ドホン 1 2 , 1 3 を備えるものを例として説明したが、 1 つの音声出力部のみを持つィャ ホンに適用することも可能である。 As described above, according to the third embodiment, four output terminals to the headphone are required, which lacks versatility, but the output power is about twice as large as that of the second embodiment. Has the advantage of being able to obtain In the first to third embodiments, the reference voltage generation circuit 7 or the voltage dividing resistors R 11 and R 12 are used as a configuration for generating the intermediate voltage of the power supply voltage VCC. It is not limited to this. That is, the present invention can be applied to any configuration capable of generating an intermediate voltage. In the first and second embodiments, the voltage supplied to the second signal line COM is 1 Z2 like the analog power supply voltage VCC, but it is not exactly 1 Z 2. Is also good. That is, as long as a desired maximum amplitude voltage or more can be obtained, the voltage may be slightly offset to the GND side or the VCC side. Further, in the first to third embodiments, the headphone for stereo sound having two channels of L and R channels has been described. However, the present invention is similarly applied to a headphone or earphone for monaural. It is possible to apply In the above-described embodiment, an example in which the left and right headphones 12 and 13 are provided has been described as an example. However, the present invention can be applied to an earphone having only one audio output unit.
また、 上記第 1〜第 3の実施形態は、 特に小型 · 軽量化が望まれるポ —夕ブル型の電子機器に適用した場合に好ましいが、 据置型の電子機器 に適用しても良いことは言うまでもない。  The first to third embodiments are particularly preferable when applied to a portable electronic device which is desired to be small and light, but may be applied to a stationary electronic device. Needless to say.
その他、 上記説明した各実施形態は、 本発明を実施するにあたっての 具体化の一例を示したものに過ぎず、 これらによつて本発明の技術的範 囲が限定的に解釈されてはならないものである。 すなわち、 本発明はそ の精神、 またはその主要な特徴から逸脱することなく、 様々な形で実施 することができる。  In addition, each of the above-described embodiments is merely an example of the embodiment of the present invention, and the technical scope of the present invention should not be interpreted in a limited manner. It is. That is, the present invention can be implemented in various forms without departing from the spirit or the main features thereof.
以上詳しく説明したように、 本発明によれば、 第 2の信号線上に電源 電圧の中間電圧を印加することにより、 音声出力部から見て （一電源電 圧 / 2 ) 〜 （+電源電圧 2 ) の間で出力電圧が正負に振られているよ うに動作させることができる。 これにより、 音声信号が供給される第 1 の信号線上に直流カツ ト用のコンデンサを設けなくても、 音声出力部へ の出力電圧を正負に振ることができる。 したがって、 従来は低周波の音 声を出力するために必須であった非常に大きなコンデンサを省略するこ とができ、 電子機器の小型 · 軽量化および低コスト化を図ることができ る。  As described above in detail, according to the present invention, by applying the intermediate voltage of the power supply voltage to the second signal line, the power supply voltage can be viewed from (one power supply voltage / 2) to (+ power supply voltage 2) ) Can be operated as if the output voltage was positive or negative. Thus, the output voltage to the audio output unit can be changed to positive or negative without providing a DC cut capacitor on the first signal line to which the audio signal is supplied. Therefore, it is possible to omit a very large capacitor, which is conventionally required for outputting low-frequency sound, and to reduce the size, weight, and cost of electronic devices.
また、 本発明の他の特徵によれば、 基準信号の中間電圧をオペアンプ により生成するようにしたので、 第 2の信号線のインピーダンスを音声 出力部から見て無視できるほど小さくすることができる。 これにより、 第 2の信号線の電圧変動を抑制し、 その電位を常に中間電圧に維持する ことが可能となる。 したがって、 左チャンネルおよび右チャンネルの 2 チャンネルを有するステレオ音声に本発明を適用した場合に、 その左右 チャンネルのセパレ一シヨ ンや S / Nを良好に保つことができるととも に、 左右チャンネルの出力電圧をきちんと正負に振ることができるよう になる。 産業上の利用可能性 Further, according to another feature of the present invention, since the intermediate voltage of the reference signal is generated by the operational amplifier, the impedance of the second signal line can be reduced to a negligible level as viewed from the audio output unit. This allows Voltage fluctuation of the second signal line can be suppressed, and the potential can be constantly maintained at the intermediate voltage. Therefore, when the present invention is applied to stereo sound having two channels, the left channel and the right channel, the separation and S / N of the left and right channels can be kept good, and the output of the left and right channels can be maintained. The voltage can be changed positively and negatively. Industrial applicability
本発明は、 直流カッ ト用のコンデンサを用いることなく、 ヘッ ドホン への出力電圧を正負に振ることができるようにし、 これによつて電子機 器の小型 · 軽量化および低コス ト化を図るのに有用である。  The present invention enables the output voltage to a headphone to swing positive and negative without using a DC cut capacitor, thereby reducing the size, weight, and cost of electronic devices. Useful for

Claims

請 求 の 範 囲 The scope of the claims
1 . 音声信号が供給される第 1 の信号線と、 上記音声信号との差をとつ て音声出力部に出力するために使用する基準信号が供給される第 2の信 号線とを有し、 1. It has a first signal line to which an audio signal is supplied, and a second signal line to which a reference signal used to output a difference from the audio signal to an audio output unit is supplied. ,
上記第 1 の信号線の上記音声信号の増幅に使用される電源電圧の中間 電圧を生成し、 上記第 2の信号線の上記基準信号として印加する中間電 圧生成回路を備えたことを特徴とする音声出力アンプ。  An intermediate voltage generating circuit for generating an intermediate voltage of a power supply voltage used for amplifying the audio signal of the first signal line, and applying the intermediate voltage as the reference signal of the second signal line. Audio output amplifier.
2 . 電源電圧に基づき音声信号を増幅して第 1 の信号線に供給するため のドライバと、  2. A driver for amplifying the audio signal based on the power supply voltage and supplying the amplified signal to the first signal line;
上記電源電圧の中間電圧を生成し、 上記音声信号に対する基準信号を 供給するための第 2の信号線に上記中間電圧を印加する中間電圧生成回 路とを備えたことを特徴とする音声出力アンプ。  An audio output amplifier that generates an intermediate voltage of the power supply voltage and applies an intermediate voltage to a second signal line for supplying a reference signal for the audio signal. .
3 . 上記第 1 の信号線は、 少なく とも 2チャンネル分の音声信号を供給 するための 2本の信号線を含み、  3. The first signal line includes at least two signal lines for supplying audio signals for at least two channels,
上記第 2の信号線に供給される基準信号は、 上記 2本の信号線に供給 される上記 2チャンネル分の音声信号に対して共通に用いられることを 特徴とする請求の範囲第 1項に記載の音声出力アンプ。  The method according to claim 1, wherein the reference signal supplied to the second signal line is commonly used for the audio signals of the two channels supplied to the two signal lines. The described audio output amplifier.
4 . 上記第 1 の信号線は、 少なく とも 2チャンネル分の音声信号を供給 するための 2本の信号線を含み、  4. The first signal line includes at least two signal lines for supplying audio signals of at least two channels,
上記第 2 の信号線に供給される基準信号は、 上記 2本の信号線に供給 される上記 2チャンネル分の音声信号に対して共通に用いられることを 特徴とする請求の範囲第 2項に記載の音声出力アンプ。  3. The method according to claim 2, wherein the reference signal supplied to the second signal line is commonly used for the audio signals of the two channels supplied to the two signal lines. The described audio output amplifier.
5 . 上記中間電圧生成回路は、 オペアンプを用いて構成されることを特 徴とする請求の範囲第 1項に記載の音声出力アンプ。  5. The audio output amplifier according to claim 1, wherein the intermediate voltage generation circuit is configured using an operational amplifier.
6 . 上記中間電圧生成回路は、 オペアンプを用いて構成されることを特 徴とする請求の範囲第 2項に記載の音声出力アンプ。 6. The intermediate voltage generation circuit is configured using an operational amplifier. 3. The audio output amplifier according to claim 2, wherein:
7 . 上記中間電圧生成回路は、 上記電源電圧を略 1 Z 2 に分圧する分圧 回路と、  7. The intermediate voltage generating circuit includes a voltage dividing circuit that divides the power supply voltage into approximately 1 Z 2,
上記分圧された電圧を入力として動作するオペアンプとを備えたこと を特徴とする請求の範囲第 1項に記載の音声出力アンプ。  2. The audio output amplifier according to claim 1, further comprising: an operational amplifier that operates using the divided voltage as an input.
8 . 上記中間電圧生成回路は、 上記電源電圧を略 1 2 に分圧する分圧 回路と、  8. The intermediate voltage generating circuit includes a voltage dividing circuit that divides the power supply voltage to approximately 12;
上記分圧された電圧を入力として動作するオペアンプとを備えたこと を特徴とする請求の範囲第 2項に記載の音声出力アンプ。  3. The audio output amplifier according to claim 2, further comprising: an operational amplifier that operates by using the divided voltage as an input.
PCT/JP2002/004755 2001-05-21 2002-05-16 Audio output amplifier WO2002095936A1 (en)

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