TW201521356A - Audio amplifier and electronic apparatus and method for restricting transition noise using the same - Google Patents
Audio amplifier and electronic apparatus and method for restricting transition noise using the same Download PDFInfo
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- 230000007704 transition Effects 0.000 title abstract 2
- 230000004044 response Effects 0.000 claims abstract description 19
- 230000003321 amplification Effects 0.000 claims description 46
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 46
- 230000001052 transient effect Effects 0.000 claims description 34
- 238000002955 isolation Methods 0.000 claims description 29
- 239000003990 capacitor Substances 0.000 claims description 15
- 230000001629 suppression Effects 0.000 claims description 8
- 230000001360 synchronised effect Effects 0.000 claims description 8
- 230000004913 activation Effects 0.000 claims 2
- 230000003213 activating effect Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 description 8
- 230000008859 change Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 230000007246 mechanism Effects 0.000 description 3
- 230000003111 delayed effect Effects 0.000 description 2
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
- H03F3/217—Class D power amplifiers; Switching amplifiers
- H03F3/2171—Class D power amplifiers; Switching amplifiers with field-effect devices
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
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- 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
- H03F3/185—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only with field-effect devices
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/03—Indexing scheme relating to amplifiers the amplifier being designed for audio applications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/372—Noise reduction and elimination in amplifier
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
- H03F2203/20—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers
- H03F2203/21—Indexing scheme relating to power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
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Abstract
Description
本發明是有關於一種音訊放大技術,且特別是有關於一種音訊放大器及應用其之電子裝置與暫態雜訊抑制方法。 The present invention relates to an audio amplification technique, and more particularly to an audio amplifier and an electronic device and transient noise suppression method using the same.
一般電子裝置在開關機過程中,其揚聲器常常會因為音訊放大器的雜訊影響而發出尖銳的噪音,從而令使用者視聽感受不佳。究其原因,一般是因為用以驅動揚聲器的音訊放大器的輸出端電壓突然發生激烈變化,而造成揚聲器將所述電壓變化轉換為尖銳刺耳的聲音輸出。除了造成使用者在使用上的不舒適外,有時過大的突波電流更會破壞揚聲器中高敏感度的元件,所以很多音頻放大裝置都將如何消除爆音雜訊作為主要的設計目標。 In the process of switching on and off the electronic device, the speaker often makes a sharp noise due to the noise of the audio amplifier, which makes the user feel bad. The reason is generally because the voltage at the output of the audio amplifier used to drive the speaker suddenly changes drastically, causing the speaker to convert the voltage change into a sharp and harsh sound output. In addition to causing user discomfort in use, sometimes excessive surge currents can damage high-sensitivity components in the speaker, so many audio amplifiers will eliminate pop noise as the main design goal.
更具體地說,一般音訊放大器的雜訊產生因素主要有二:一是因音訊放大器的輸出端電壓發生快速的準位變動所造成;二是因音訊放大器電路本身的暫態雜訊(transition noise)效 應所造成。 More specifically, the noise of the general audio amplifier has two main factors: one is due to the rapid level change of the output voltage of the audio amplifier; the other is due to the transient noise of the audio amplifier circuit itself. )effect Should be caused.
其中,上述因第一項因素所造成的雜訊,在現行的應用中,通常會採用具有預充電機制的音訊放大器架構來解決。其係藉由在音訊放大器致能之前,預先對音訊放大器的輸出端進行緩慢的充電,以令音訊放大器的輸出端不會有大幅地準位變動。 Among them, the above-mentioned noise caused by the first factor is usually solved by an audio amplifier architecture with a pre-charging mechanism in current applications. By slowly charging the output of the audio amplifier before the audio amplifier is enabled, the output of the audio amplifier does not have a large level change.
然而,對於上述因第二項因素所造成的雜訊而言,由於其係肇因於音訊放大器的內部電路之既有電路特性,因此在現有技術下,僅能透過降低電路頻寬的方式來加以抑制。否則即必須大幅更動音訊放大器的電路設計。 However, for the above-mentioned noise caused by the second factor, since the system is due to the existing circuit characteristics of the internal circuit of the audio amplifier, in the prior art, only by reducing the circuit bandwidth. Suppress it. Otherwise, the circuit design of the audio amplifier must be greatly changed.
本發明提供一種音訊放大器及應用其之電子裝置與暫態雜訊抑制方法,其可在不須降低電路頻寬的前提下,有效地抑制暫態雜訊的效應。 The invention provides an audio amplifier and an electronic device and a transient noise suppression method thereof, which can effectively suppress the effect of transient noise without reducing the circuit bandwidth.
本發明的音訊放大器包括前置放大電路、輸出級電路以及延遲開關電路。前置放大電路接收音訊輸入訊號,並且反應於前級控制訊號而致能或禁能,其中前置放大電路於致能時放大音訊輸入訊號以產生音訊放大訊號。輸出級電路反應於後級控制訊號而致能或禁能,其中輸出級電路於致能時將所接收的訊號轉換為音訊輸出訊號。延遲開關電路耦接於前置放大電路與輸出級電路之間,用以依據電源啟動訊號提供前級控制訊號與後級控制訊號,從而令前置放大電路與輸出級電路間隔延遲期間依序致能或 禁能,並且基於後級控制訊號而決定是否將音訊放大訊號提供至輸出級電路。 The audio amplifier of the present invention includes a preamplifier circuit, an output stage circuit, and a delay switch circuit. The preamplifier circuit receives the audio input signal and is enabled or disabled in response to the preamplifier signal, wherein the preamplifier circuit amplifies the audio input signal to generate the audio amplifying signal when enabled. The output stage circuit is enabled or disabled in response to the subsequent stage control signal, wherein the output stage circuit converts the received signal into an audio output signal when enabled. The delay switch circuit is coupled between the preamplifier circuit and the output stage circuit, and is configured to provide the pre-control signal and the post-level control signal according to the power-on signal, thereby sequentially delaying the interval between the preamplifier circuit and the output stage circuit Can or Disabled, and based on the subsequent control signals, decide whether to provide the audio amplification signal to the output stage circuit.
在本發明一實施例中,延遲開關電路包括隔離開關以及延遲單元。隔離開關耦接於前置放大電路與輸出級電路之間,其中隔離開關受控於後級控制訊號而導通或截止,從而決定是否將音訊放大訊號提供至輸出級電路。延遲單元耦接前置放大電路、隔離開關以及輸出級電路,用以產生與電源啟動訊號同步的第一訊號,並且根據延遲期間延遲第一訊號以產生第二訊號。其中,延遲單元依據電源啟動訊號的準位切換而以第一訊號與第二訊號其中之一者為前級控制訊號,並且以地依訊號與第二訊號其中之另一者為後級控制訊號。 In an embodiment of the invention, the delay switch circuit includes an isolation switch and a delay unit. The isolation switch is coupled between the preamplifier circuit and the output stage circuit, wherein the isolation switch is controlled to be turned on or off by the subsequent control signal to determine whether to provide the audio amplification signal to the output stage circuit. The delay unit is coupled to the preamplifier circuit, the isolating switch and the output stage circuit for generating a first signal synchronized with the power start signal, and delaying the first signal according to the delay period to generate the second signal. The delay unit uses one of the first signal and the second signal as the pre-control signal according to the level switching of the power-on signal, and the other one of the signal-based signal and the second signal is the subsequent-level control signal. .
在本發明一實施例中,當電源啟動訊號從禁能準位切換至致能準位時,延遲單元以第一訊號為前級控制訊號並且以第二訊號為後級控制訊號,從而令前置放大電路先反應於前級控制訊號而致能,再於延遲期間後令輸出級電路反應於後級控制訊號而致能並同時導通隔離開關。 In an embodiment of the invention, when the power-on signal is switched from the disable level to the enable level, the delay unit controls the signal with the first signal and the second signal with the second signal, thereby The amplifier circuit is first activated in response to the pre-stage control signal, and then the output stage circuit is enabled to react to the subsequent stage control signal and simultaneously turn on the isolation switch after the delay period.
在本發明一實施例中,當電源啟動訊號從致能準位切換至禁能準位時,延遲單元以第二訊號為前級控制訊號並且以第一訊號為後級控制訊號,從而令輸出級電路先反應於後級控制訊號而禁能並同時截止隔離開關,再於延遲期間後令前置放大電路反應於後級控制訊號而禁能。 In an embodiment of the invention, when the power-on signal is switched from the enable level to the disable level, the delay unit uses the second signal as the pre-control signal and the first signal as the latter control signal, thereby outputting the signal. The stage circuit is first disabled in response to the subsequent stage control signal and simultaneously cuts off the isolating switch, and then disables the preamplifier circuit in response to the subsequent stage control signal after the delay period.
在本發明一實施例中,前置放大電路包括前置放大器、 輸出控制級以及偏壓單元。前置放大器具有負輸入端、正輸入端以及輸出端。前置放大器的負輸入端接收音訊輸入訊號,且前置放大器的正輸入端接收參考電壓。輸出控制級耦接前置放大器的輸出端,並依據前置放大器的輸出而產生音訊放大訊號。偏壓單元用以提供前置放大器與輸出控制級運作所需的工作電壓。 In an embodiment of the invention, the preamplifier circuit includes a preamplifier, Output control stage and bias unit. The preamplifier has a negative input, a positive input, and an output. The negative input of the preamplifier receives the audio input signal, and the positive input of the preamplifier receives the reference voltage. The output control stage is coupled to the output of the preamplifier and generates an audio amplification signal according to the output of the preamplifier. The bias unit is used to provide the operating voltage required to operate the preamplifier and output control stage.
在本發明一實施例中,輸出控制級係以浮接電流源組態(floating current source configuration)所構成。 In an embodiment of the invention, the output control stage is constructed in a floating current source configuration.
在本發明一實施例中,輸出級係以推挽式組態(push-pull configuration)所構成。 In an embodiment of the invention, the output stage is constructed in a push-pull configuration.
本發明的電子裝置,包括如前所述的音訊放大器、回授電路、隔離電容以及揚聲器。回授電路耦接於音訊放大器的輸入端與輸出端之間,用以將音訊輸出訊號回授至前置放大電路。揚聲器經由隔離電容耦接音訊放大器,用以將音訊輸出訊號轉換為聲音輸出。 The electronic device of the present invention includes an audio amplifier, a feedback circuit, an isolation capacitor, and a speaker as described above. The feedback circuit is coupled between the input end and the output end of the audio amplifier for feeding back the audio output signal to the preamplifier circuit. The speaker is coupled to the audio amplifier via an isolating capacitor for converting the audio output signal into a sound output.
本發明的音訊放大器的暫態雜訊抑制方法包括以下步驟:依據電源啟動訊號而提供用以控制前置放大電路的前級控制訊號與用以控制輸出級電路的後級控制訊號,從而令前置放大電路與輸出級電路間隔延遲期間依序致能或禁能;以及基於後級控制訊號而決定是否將前置放大電路所產生的音訊放大訊號提供至輸出級電路。 The method for suppressing transient noise of the audio amplifier of the present invention comprises the steps of: providing a pre-control signal for controlling the pre-amplifier circuit and a post-level control signal for controlling the output stage circuit according to the power-on signal, thereby The amplification circuit and the output stage circuit are sequentially enabled or disabled during the interval delay period; and determining whether to provide the audio amplification signal generated by the preamplifier circuit to the output stage circuit based on the subsequent stage control signal.
在本發明一實施例中,所述暫態雜訊抑制方法更包括:當電源啟動訊號從禁能準位切換至致能準位時,提供與電源啟動 訊號同步的前級控制訊號,以先致能前置放大電路;以及提供基於延遲前級控制訊號所產生的後級控制訊號,以於延遲期間後再致能輸出級電路並同時將音訊放大訊號提供至輸出級電路。 In an embodiment of the invention, the transient noise suppression method further includes: providing a power start when the power start signal is switched from the disable level to the enable level. a pre-stage control signal for synchronizing the signal to enable the preamplifier circuit; and providing a post-stage control signal generated based on the delay pre-stage control signal to enable the output stage circuit and simultaneously amplify the audio signal after the delay period Provide to the output stage circuit.
在本發明一實施例中,所述暫態雜訊抑制方法更包括:當電源啟動訊號從致能準位切換至禁能準位時,提供與電源啟動訊號同步的後級控制訊號,以先禁能輸出級電路並同時停止將音訊放大訊號提供至輸出級電路;以及提供基於延遲後級控制訊號所產生的前級控制訊號,以於延遲期間後再禁能前置放大電路。 In an embodiment of the invention, the method for suppressing transient noise further includes: providing a subsequent control signal synchronized with the power-on signal when the power-on signal is switched from the enable level to the disable level. The output stage circuit is disabled and the audio amplification signal is simultaneously supplied to the output stage circuit; and the pre-stage control signal generated based on the delayed post-stage control signal is provided to disable the preamplifier circuit after the delay period.
基於上述,本發明實施例提出一種音訊放大器及應用其之電子裝置與暫態雜訊抑制方法。所述音訊放大器可藉由具順序性且有間隔地致/禁能方式來控制前級的前置放大電路與後級的輸出級電路,並且同步地配合輸出級電路的致能時序而將前置放大電路所輸出的音訊放大訊號提供至輸出級電路。基此,無論在電源啟動或電源關閉時,前置放大電路的切換皆不會對輸出級電路所輸出的音訊輸出訊號造成影響,故音訊放大器的暫態雜訊可在無須降低電路頻寬的前提下而有效地降低/抑制,進而提高使用者收聽的品質與舒適度。 Based on the above, an embodiment of the present invention provides an audio amplifier, an electronic device using the same, and a transient noise suppression method. The audio amplifier can control the preamplifier circuit of the preamplifier and the output stage circuit of the subsequent stage by a sequential and interval inducing/disabling manner, and synchronously cooperate with the enable timing of the output stage circuit to The audio amplification signal outputted by the amplifier circuit is supplied to the output stage circuit. Therefore, the switching of the preamplifier circuit does not affect the audio output signal outputted by the output stage circuit when the power is turned on or the power is turned off, so the transient noise of the audio amplifier can be reduced without reducing the circuit bandwidth. Under the premise, it is effectively reduced/suppressed, thereby improving the quality and comfort of the user.
為讓本發明的上述特徵和優點能更明顯易懂,下文特舉實施例,並配合所附圖式作詳細說明如下。 The above described features and advantages of the invention will be apparent from the following description.
10、10’、20‧‧‧電子裝置 10, 10', 20‧‧‧ electronic devices
100、200、400‧‧‧音訊放大器 100, 200, 400‧‧‧ audio amplifier
110‧‧‧偏壓電路 110‧‧‧Bias circuit
120‧‧‧開關 120‧‧‧ switch
210、410‧‧‧前置放大電路 210, 410‧‧‧ preamplifier circuit
212、412‧‧‧前置放大器 212, 412‧‧‧ preamplifier
214、414‧‧‧輸出控制級 214, 414‧‧‧ output control level
216、416‧‧‧偏壓單元 216, 416‧‧ ‧ bias unit
220、420‧‧‧輸出級電路 220, 420‧‧‧ output stage circuit
230、430‧‧‧延遲開關電路 230, 430‧‧‧ delay switch circuit
232、432_1、432_2‧‧‧隔離開關 232, 432_1, 432_2‧‧‧ isolation switch
234、434‧‧‧延遲單元 234, 434‧‧‧ delay unit
C1、C2‧‧‧電容 C1, C2‧‧‧ capacitor
Cc‧‧‧隔離電容 Cc‧‧‧Isolation Capacitor
CL1~CL4‧‧‧特性曲線 CL1~CL4‧‧‧ characteristic curve
CS1、CS2‧‧‧電流源 CS1, CS2‧‧‧ current source
FB‧‧‧回授電路 FB‧‧‧ feedback circuit
GND‧‧‧接地準位 GND‧‧‧ Grounding level
H‧‧‧致能準位 H‧‧‧Enable level
L‧‧‧禁能準位 L‧‧‧ disable level
M1~M6、Mp1、Mp2、Mn1、Mn2‧‧‧電晶體 M1~M6, Mp1, Mp2, Mn1, Mn2‧‧‧O crystal
LD‧‧‧揚聲器 LD‧‧‧ Speaker
PU‧‧‧電源啟動訊號 PU‧‧‧Power start signal
PUF‧‧‧前級控制訊號 PUF‧‧‧pre-control signal
PUFb‧‧‧反相前級控制訊號 PUFb‧‧‧Inverted pre-control signal
PUO‧‧‧後級控制訊號 PUO‧‧‧After control signal
PUOb‧‧‧反相後級控制訊號 PUOb‧‧‧ reverse phase control signal
Ri、Rf‧‧‧電阻 Ri, Rf‧‧‧ resistance
S1‧‧‧第一訊號 S1‧‧‧ first signal
S2‧‧‧第二訊號 S2‧‧‧ second signal
S_A、S_Ab‧‧‧差動放大訊號 S_A, S_Ab‧‧‧Differential amplification signal
S_AI‧‧‧音訊輸入訊號 S_AI‧‧‧ audio input signal
S_AMP、S_AMP’‧‧‧音訊放大訊號 S_AMP, S_AMP’‧‧‧ audio amplification signal
S_AMPb‧‧‧反相音訊放大訊號 S_AMPb‧‧‧Inverted audio amplification signal
S_AO、S_AO’‧‧‧音訊輸出訊號 S_AO, S_AO’‧‧‧ audio output signals
TD、TF‧‧‧延遲期間 T D , T F ‧‧‧delay period
VB1、VB2‧‧‧工作電壓 VB1, VB2‧‧‧ working voltage
VCM‧‧‧參考電壓 VCM‧‧‧ reference voltage
Vcm‧‧‧參考電壓準位 Vcm‧‧‧reference voltage level
VDD‧‧‧偏壓 VDD‧‧‧ bias
Vdd‧‧‧偏壓準位 Vdd‧‧‧ bias level
Vn‧‧‧工作電壓準位 Vn‧‧‧ working voltage level
S610、S620‧‧‧步驟 S610, S620‧‧‧ steps
圖1A與1B為一種電子裝置的示意圖。 1A and 1B are schematic views of an electronic device.
圖2為本發明一實施例的電子裝置的示意圖。 2 is a schematic diagram of an electronic device according to an embodiment of the invention.
圖3為依照圖2實施例的音訊放大器的訊號時序示意圖。 3 is a timing diagram of signal timing of an audio amplifier in accordance with the embodiment of FIG.
圖4為本發明一實施例的音訊放大器的電路架構示意圖。 4 is a schematic diagram showing the circuit architecture of an audio amplifier according to an embodiment of the present invention.
圖5A與5B為依照圖4實施例的音訊放大器與傳統音訊放大器的特性比較示意圖。 5A and 5B are schematic diagrams showing the comparison of characteristics of an audio amplifier and a conventional audio amplifier in accordance with the embodiment of Fig. 4.
圖6為本發明一實施例的音訊放大器的暫態雜訊抑制方法的步驟流程圖。 FIG. 6 is a flow chart showing the steps of a method for suppressing transient noise of an audio amplifier according to an embodiment of the present invention.
圖1A與1B為一種電子裝置的示意圖。請先參照圖1A,電子裝置10包括音訊放大器(audio amplifier)100以及揚聲器LD,其中音訊放大器100經由隔離電容Cc耦接至揚聲器LD。 1A and 1B are schematic views of an electronic device. Referring first to FIG. 1A , the electronic device 10 includes an audio amplifier 100 and a speaker LD , wherein the audio amplifier 100 is coupled to the speaker LD via an isolation capacitor Cc .
具體而言,音訊放大器100可用以將所接收的音訊輸入訊號S_AI轉換為音訊輸出訊號S_AO。隔離電容Cc可用以隔絕音訊輸出訊號S_AO的直流成分,並且將隔絕直流成分後的音訊輸出訊號S_AO’提供給揚聲器LD,從而令揚聲器LD反應於音訊輸出訊號S_AO’而轉換出相應的聲音輸出。於此架構下,在電子裝置10啟動/關閉的瞬間,由於音訊輸出訊號S_AO會發生快速的準位切換(例如啟動時從接地準位GND快速提升至參考電壓準位Vcm),使得音訊輸出訊號S_AO’會因隔離電容Cc的突波電流(spike current)而發生瞬間的準位變動,從而令揚聲器LD發 出尖銳的噪音。其中,所述因電壓準位快速切換而造成的雜訊,一般稱之為爆音雜訊(pop-noise)。 Specifically, the audio amplifier 100 can be used to convert the received audio input signal S_AI into an audio output signal S_AO. The isolation capacitor Cc can be used to isolate the DC component of the audio output signal S_AO, and provide the audio output signal S_AO' after the DC component is isolated to the speaker LD, so that the speaker LD reacts to the audio output signal S_AO' to convert the corresponding sound output. In this architecture, at the instant when the electronic device 10 is turned on/off, the audio output signal S_AO will be rapidly switched (for example, rapidly rising from the grounding level GND to the reference voltage level Vcm at startup), so that the audio output signal is output. S_AO' will instantaneously change the position due to the spike current of the isolation capacitor Cc, thus making the speaker LD Sharp noise. Among them, the noise caused by the rapid switching of the voltage level is generally called pop-noise.
在現行的應用中,通常會採用軟啟動(soft-start)或無電容(Capless)的架構來消除所述爆音雜訊的現象。以圖1B的具軟啟動機制的電子裝置10’為例,電子裝置10’除了包括音訊放大器100以及揚聲器LD外,還包括偏壓電路110以及開關120。於圖1B所繪示的架構下,當電子裝置10’啟動時,偏壓電路110會先被致能並且開關120會先被導通,以使偏壓電路110經由開關120而將音訊放大器100的輸出端逐漸的充電至參考電壓準位Vcm,而後音訊放大器100才會被致能以輸出音訊輸出訊號S_AO。如此一來,由於在音訊放大器100致能時,其輸出端的電壓已經被穩定地維持在參考電壓準位Vcm,因此可消除所述之爆音雜訊的現象。 In current applications, a soft-start or capless architecture is often used to eliminate the phenomenon of pop noise. Taking the electronic device 10' having the soft start mechanism of FIG. 1B as an example, the electronic device 10' includes a bias circuit 110 and a switch 120 in addition to the audio amplifier 100 and the speaker LD. In the architecture illustrated in FIG. 1B, when the electronic device 10' is activated, the bias circuit 110 is first enabled and the switch 120 is first turned on to cause the bias circuit 110 to turn the audio amplifier via the switch 120. The output of 100 is gradually charged to the reference voltage level Vcm, and then the audio amplifier 100 is enabled to output the audio output signal S_AO. In this way, since the voltage at the output terminal of the audio amplifier 100 is stably maintained at the reference voltage level Vcm, the phenomenon of the popping noise can be eliminated.
然而,於圖1B的架構下雖可解決因電壓準位快速變動而產生的爆音雜訊問題,但是卻無助於改善音訊放大器100本身的暫態雜訊(transition noise)。更具體地說,雖然在音訊放大器100致能時,其輸出端已經維持在參考電壓準位Vcm,但是在音訊放大器100致能的瞬間,音訊輸出訊號S_AO還是會因為內部電路的回授效應而在參考電壓準位Vcm上發生瞬間的準位變動(即所謂之暫態雜訊)。而此現象同樣會造成揚聲器LD發出尖銳的噪音。 However, in the architecture of FIG. 1B, the pop noise problem caused by the rapid change of the voltage level can be solved, but it does not help to improve the transient noise of the audio amplifier 100 itself. More specifically, although the output terminal has been maintained at the reference voltage level Vcm when the audio amplifier 100 is enabled, the audio output signal S_AO is still due to the feedback effect of the internal circuit at the instant when the audio amplifier 100 is enabled. An instantaneous level change (so-called transient noise) occurs at the reference voltage level Vcm. This phenomenon also causes the speaker LD to make a sharp noise.
換言之,所述可解決爆音雜訊現象的音訊放大器架構,並無法抑制音訊放大器100本身的暫態雜訊。在現有技術下,所 述音訊放大器100的暫態雜訊現象通常僅能藉由設計者在暫態雜訊與頻寬特性之間做出設計取捨(trade-off)來進一步抑制。 In other words, the audio amplifier architecture that solves the pop noise phenomenon cannot suppress the transient noise of the audio amplifier 100 itself. Under the prior art, The transient noise of the audio amplifier 100 is typically only further suppressed by the designer's trade-off between transient noise and bandwidth characteristics.
有鑑於此,本發明實施例提出一種音訊放大器及應用其之電子裝置與暫態雜訊抑制方法。所述音訊放大器可在無須犧牲電路頻寬特性的前提下,藉由特定的電路組態與控制時序來降低/抑制音訊放大器的暫態雜訊,進而提高使用者收聽的品質與舒適度。為了使本揭露之內容可以被更容易明瞭,以下特舉實施例做為本揭露確實能夠據以實施的範例。另外,凡可能之處,在圖式及實施方式中使用相同標號的元件/構件/步驟,係代表相同或類似部件。 In view of this, an embodiment of the present invention provides an audio amplifier and an electronic device and a transient noise suppression method using the same. The audio amplifier can reduce/suppress the transient noise of the audio amplifier by using specific circuit configuration and control timing without sacrificing the bandwidth characteristics of the circuit, thereby improving the quality and comfort of the user. In order to make the disclosure of the present disclosure easier to understand, the following specific embodiments are examples of the disclosure that can be implemented. In addition, wherever possible, the same elements, components, and steps in the drawings and embodiments are used to represent the same or similar components.
圖2為本發明一實施例的電子裝置的示意圖。請參照圖2,電子裝置20包括音訊放大器200、回授電路FB、隔離電容Cc以及揚聲器LD。其中,音訊放大器200包括前置放大電路210、輸出級電路220、延遲開關電路230。前置放大電路210的輸入端接收音訊輸入訊號S_AI。延遲開關電路230耦接於前置放大電路210的輸出端與輸出級電路220的輸入端之間。輸出級電路220的輸出端經由隔離電容Cc耦接至揚聲器LD,其中揚聲器LD會將輸出級電路220所輸出的音訊輸出訊號S_AO轉換為聲音輸出。回授電路FB耦接於前置放大電路210的輸入端與輸出級電路220的輸出端之間(即,音訊放大器200的輸入端與輸出端之間),其係用以將輸出級電路220所輸出的音訊輸出訊號S_AO回授給前置放大電路210。於本實施例中,回授電路FB係以電阻Rf為 例來實現,但本發明不僅限於此。 2 is a schematic diagram of an electronic device according to an embodiment of the invention. Referring to FIG. 2, the electronic device 20 includes an audio amplifier 200, a feedback circuit FB, an isolation capacitor Cc, and a speaker LD. The audio amplifier 200 includes a preamplifier circuit 210, an output stage circuit 220, and a delay switch circuit 230. The input terminal of the preamplifier circuit 210 receives the audio input signal S_AI. The delay switch circuit 230 is coupled between the output of the preamplifier circuit 210 and the input of the output stage circuit 220. The output end of the output stage circuit 220 is coupled to the speaker LD via an isolation capacitor Cc, wherein the speaker LD converts the audio output signal S_AO output by the output stage circuit 220 into a sound output. The feedback circuit FB is coupled between the input end of the preamplifier circuit 210 and the output end of the output stage circuit 220 (ie, between the input end and the output end of the audio amplifier 200) for connecting the output stage circuit 220. The output audio output signal S_AO is fed back to the preamplifier circuit 210. In this embodiment, the feedback circuit FB is based on the resistor Rf. This is achieved by way of example, but the invention is not limited thereto.
具體而言,前置放大電路210會反應於延遲開關電路230所提供的前級控制訊號PUF而致能(enable)或禁能(disable)。其中,當前置放大電路210反應於前級控制訊號PUF而致能時,其會對所接收之音訊輸入訊號S_AI進行訊號放大的動作,並據以產生音訊放大訊號S_AMP;反之,當前置放大電路210反應於前級控制訊號PUF而禁能時,則其會停止訊號放大的動作。 Specifically, the preamplifier circuit 210 is enabled or disabled in response to the pre-stage control signal PUF provided by the delay switch circuit 230. Wherein, when the current amplifier circuit 210 is enabled in response to the pre-stage control signal PUF, it will perform signal amplification on the received audio input signal S_AI, and accordingly generate an audio amplification signal S_AMP; otherwise, the current amplifier circuit When 210 is disabled in the pre-stage control signal PUF, it will stop the signal amplification.
輸出級電路220會反應於延遲開關電路230所提供的後級控制訊號PUO而致能或禁能。其中,當輸出級電路220反應於後級控制訊號PUO而致能時,其會將從延遲開關電路230所接收的訊號S_AMP’轉換為音訊輸出訊號S_AO;反之,當輸出級電路220反應於後級控制訊號PUO而禁能時,則其會停止輸出音訊輸出訊號S_AO。 The output stage circuit 220 is enabled or disabled in response to the post-stage control signal PUO provided by the delay switch circuit 230. Wherein, when the output stage circuit 220 is enabled in response to the subsequent stage control signal PUO, it converts the signal S_AMP' received from the delay switch circuit 230 into the audio output signal S_AO; otherwise, when the output stage circuit 220 reacts When the level control signal PUO is disabled, it will stop outputting the audio output signal S_AO.
延遲開關電路230會依據所接收的電源啟動訊號PU而提供相應的前級控制訊號PUF與後級控制訊號PUO以控制前置放大電路210與輸出級電路220的運作,從而令前置放大電路210與輸出級電路220間隔一特定的延遲期間(例如1微秒(μs),但不以此為限,可由設計者自行設計)而依序致能或禁能。此外,延遲開關電路230還會基於後級控制訊號PUO而決定是否將音訊放大訊號S_AMP提供至輸出級電路220。 The delay switch circuit 230 provides a corresponding pre-stage control signal PUF and a post-stage control signal PUO according to the received power-on signal PU to control the operation of the preamplifier circuit 210 and the output stage circuit 220, thereby causing the preamplifier circuit 210. The output stage circuit 220 is sequentially enabled or disabled by a specific delay period (for example, 1 microsecond (μs), but not limited thereto, which can be designed by the designer). In addition, the delay switch circuit 230 also determines whether to provide the audio amplification signal S_AMP to the output stage circuit 220 based on the subsequent stage control signal PUO.
換言之,延遲開關電路230係以同一控制訊號來控制是否致能輸出級電路220以及是否將音訊放大訊號S_AMP提供給輸 出級電路220。亦即,音訊放大訊號S_AMP會在輸出級電路220致能的同時經由延遲開關電路230而被提供至輸出級電路220;反之,當輸出級電路220從致能狀態被切換至禁能狀態時,延遲開關電路230會同時將前置放大電路210與輸出級電路220之間的訊號傳輸路徑斷開,使得音訊放大訊號S_AMP不會被提供至輸出級電路220的輸入端。 In other words, the delay switch circuit 230 controls whether the output stage circuit 220 is enabled and whether the audio amplification signal S_AMP is supplied to the input by the same control signal. The step circuit 220 is output. That is, the audio amplification signal S_AMP is supplied to the output stage circuit 220 via the delay switch circuit 230 while the output stage circuit 220 is enabled; conversely, when the output stage circuit 220 is switched from the enabled state to the disabled state, The delay switch circuit 230 simultaneously disconnects the signal transmission path between the preamplifier circuit 210 and the output stage circuit 220 such that the audio amplification signal S_AMP is not supplied to the input terminal of the output stage circuit 220.
在本實施例中,延遲開關電路230可利用包括隔離開關232以及延遲單元234的電路架構來實現:1)提供前級控制訊號PUF與後級控制訊號PUO以及2)決定是否將音訊放大訊號S_AMP提供給輸出級電路220的功能。 In this embodiment, the delay switch circuit 230 can be implemented by using a circuit structure including the isolation switch 232 and the delay unit 234: 1) providing the pre-stage control signal PUF and the post-stage control signal PUO and 2) determining whether to amplify the signal S_AMP The function provided to the output stage circuit 220.
詳細而言,隔離開關232耦接於前置放大電路210的輸出端與輸出級電路220的輸入端之間,其中隔離開關232係受控於後級控制訊號PUO而導通或截止,從而決定是否將音訊放大訊號S_AMP提供至輸出級電路220。延遲單元234耦接前置放大電路210、隔離開關232以及輸出級電路220,其係用以產生與電源啟動訊號PU同步的第一訊號S1,並且根據設計者所設定之延遲期間來延遲第一訊號S1以第二訊號S2。其中,延遲單元234會依據電源啟動訊號PU的準位切換(也就是電子裝置20是從開啟狀態進入關閉狀態還是從關閉狀態進入開啟狀態)而選擇性地以第一訊號S1與第二訊號S2其中之一做為前級控制訊號PUF,並且以第一訊號S1與第二訊號S其中之另一做為後級控制訊號PUO。 In detail, the isolation switch 232 is coupled between the output end of the preamplifier circuit 210 and the input end of the output stage circuit 220, wherein the isolation switch 232 is controlled to be turned on or off by the post-stage control signal PUO, thereby determining whether The audio amplification signal S_AMP is supplied to the output stage circuit 220. The delay unit 234 is coupled to the preamplifier circuit 210, the isolating switch 232, and the output stage circuit 220 for generating the first signal S1 synchronized with the power start signal PU, and delaying the first according to a delay period set by the designer. Signal S1 is with a second signal S2. The delay unit 234 selectively switches between the first signal S1 and the second signal S2 according to the level switching of the power-on signal PU (that is, whether the electronic device 20 enters the off state from the on state or the off state). One of them is used as the pre-stage control signal PUF, and the other one of the first signal S1 and the second signal S is used as the post-stage control signal PUO.
底下搭配圖3實施例的訊號時序來進一步說明本發明實施例之音訊放大器200的具體運作。在圖3中,左側部分的時序係表示電子裝置20從關閉狀態被啟動的訊號時序(於此標示為“電源啟動”);而右側部分的時序則係表示電子裝置20從啟動狀態被關閉的訊號時序(於此標示為“電源關閉”)。此外,圖3所繪示之訊號時序係為音訊輸入訊號S_AI尚未輸入時之訊號時序。 The specific operation of the audio amplifier 200 of the embodiment of the present invention will be further described below with the signal timing of the embodiment of FIG. 3. In FIG. 3, the timing of the left portion indicates the timing of the signal that the electronic device 20 is activated from the off state (herein indicated as "power on"); and the timing of the right portion indicates that the electronic device 20 is turned off from the startup state. Signal timing (here marked "Power Off"). In addition, the signal timing shown in FIG. 3 is the signal timing when the audio input signal S_AI has not been input.
請先同時參照圖2以及圖3有關於電源啟動部分的時序,當電子裝置20從關閉狀態被啟動時,電源啟動訊號PU會從禁能準位L切換至致能準位H。此時,延遲單元234會反應於電源啟動訊號PU的準位切換而產生與電源啟動訊號PU同步的第一訊號S1並且基於第一訊號S1產生與第一訊號S1間隔一段延遲期間TD的第二訊號S2,於此,延遲單元234會以第一訊號S1做為前級控制訊號PUF以控制前置放大電路210,並且以第二訊號S2做為後級控制訊號PUO以控制輸出級電路220。 Please refer to FIG. 2 and FIG. 3 simultaneously for the timing of the power-on portion. When the electronic device 20 is activated from the off state, the power-on signal PU will be switched from the disable level L to the enable level H. At this time, the delay unit 234 generates a first signal S1 synchronized with the power-on signal PU in response to the level switching of the power-on signal PU, and generates a delay period T D from the first signal S1 based on the first signal S1. The second signal S2, here, the delay unit 234 uses the first signal S1 as the pre-stage control signal PUF to control the preamplifier circuit 210, and the second signal S2 as the post-stage control signal PUO to control the output stage circuit 220. .
基於前級控制訊號PUF與後級控制訊號PUO的訊號時序,前置放大電路210會先反應於前級控制訊號PUF而致能,並據以令音訊放大訊號S_AMP於延遲期間TD內從偏壓準位Vdd降至工作電壓準位Vn。於延遲期間TD內,前置放大電路210會因為前級控制訊號PUF的切換而產生雜訊突波(如音訊放大訊號S_AMP的突波部分),但由於後級控制訊號PUO尚未切換為致能準位H,因此輸出級電路220尚未被致能且隔離開關232亦處於 截止的狀態,故音訊放大訊號S_AMP的雜訊突波並不會反應在音訊輸出訊號S_AO上。 Based on the signal timing of the pre-stage control signal PUF and the post-stage control signal PUO, the preamplifier circuit 210 is first enabled in response to the pre-stage control signal PUF, and accordingly, the audio amplification signal S_AMP is biased in the delay period T D . The pressure level Vdd is lowered to the operating voltage level Vn. During the delay period T D , the preamplifier circuit 210 generates a noise spurt (such as the spur portion of the audio amplification signal S_AMP) due to the switching of the pre-stage control signal PUF, but since the post-stage control signal PUO has not been switched The level H can be leveled, so the output stage circuit 220 has not been enabled and the isolation switch 232 is also in the off state, so the noise surge of the audio amplification signal S_AMP does not reflect on the audio output signal S_AO.
接著,在經過延遲期間TD後,後級控制訊號PUO從禁能準位L切換為致能準位H,使得輸出級電路220被致能並且同時使隔離開關232被導通。此時,由於在前置放大電路210的輸出端的音訊放大訊號S_AMP已經趨於穩定,因此通過隔離開關232而提供至輸出級電路220的輸入端的音訊放大訊號S_AMP’已經幾乎沒有暫態雜訊的成分。基此,輸出級電路220所輸出之音訊輸出訊號S_AO可穩定地維持在參考電壓準位Vcm上,而幾乎不會產生暫態雜訊。其中,如圖3所示,本發明實施例的音訊輸出訊號S_AO的暫態雜訊的脈波強度僅約3mV。 Then, after the delay period T D has elapsed, the subsequent stage control signal PUO is switched from the disable level L to the enable level H, so that the output stage circuit 220 is enabled and the isolation switch 232 is turned on at the same time. At this time, since the audio amplification signal S_AMP at the output end of the preamplifier circuit 210 has stabilized, the audio amplification signal S_AMP' supplied to the input end of the output stage circuit 220 through the isolation switch 232 has almost no transient noise. ingredient. Therefore, the audio output signal S_AO outputted by the output stage circuit 220 can be stably maintained at the reference voltage level Vcm with almost no transient noise. As shown in FIG. 3, the pulse wave intensity of the transient noise of the audio output signal S_AO according to the embodiment of the present invention is only about 3 mV.
請同時參照圖2以及圖3有關於電源關閉部分的時序,當電子裝置20從啟動狀態被關閉時,電源啟動訊號PU會從致能準位H切換為禁能準位L。此時,延遲單元234會反應於電源啟動訊號PU的準位切換而產生與電源啟動訊號PU同步的第一訊號S1並且基於第一訊號S1產生與第一訊號S1間隔一段延遲期間TF的第二訊號S2,於此,延遲單元234會以第一訊號S1做為後級控制訊號PUO以控制輸出級電路220,並且以第二訊號S2做為前級控制訊號PUF以控制前置放大電路210。 Please refer to FIG. 2 and FIG. 3 simultaneously for the timing of the power-off portion. When the electronic device 20 is turned off from the startup state, the power-on signal PU will be switched from the enable level H to the disable level L. At this time, the delay unit 234 generates a first signal S1 synchronized with the power-on signal PU in response to the level switching of the power-on signal PU and generates a delay period T F from the first signal S1 based on the first signal S1. The second signal S2, here, the delay unit 234 uses the first signal S1 as the subsequent control signal PUO to control the output stage circuit 220, and the second signal S2 as the pre-control signal PUF to control the preamplifier circuit 210. .
基於前級控制訊號PUF與後級控制訊號PUO的訊號時序,輸出級電路220會先反應於後級控制訊號PUO而禁能並且隔離開關232會同時被截止,使得輸出級電路220先行停止進行訊 號轉換的運作。在後級控制訊號PUO切換的瞬間,由於前級的前置放大電路210仍保持在穩定運作的狀態,因此音訊輸出訊號S_AO僅會因為電容負載效應而發生微幅的變動(約1mV)。 Based on the signal timing of the pre-stage control signal PUF and the post-stage control signal PUO, the output stage circuit 220 is first disabled in response to the post-stage control signal PUO and the isolation switch 232 is simultaneously turned off, so that the output stage circuit 220 stops transmitting for the first time. The operation of the number conversion. At the moment when the post-stage control signal PUO is switched, since the preamplifier circuit 210 of the previous stage is still in a stable operation state, the audio output signal S_AO only slightly changes (about 1 mV) due to the capacitive load effect.
接著,在經過延遲期間TF後,前級控制訊號PUF從致能準位H切換為禁能準位L,使得前置放大電路210被禁能。此時,由於後級的輸出級電路220已經被禁能,且隔離開關232亦已被截止,因此前置放大電路210切換時所造成的暫態雜訊不會反應在音訊輸出訊號S_AO上。 Then, after the delay period T F has elapsed, the pre-stage control signal PUF is switched from the enable level H to the disable level L, so that the preamplifier circuit 210 is disabled. At this time, since the output stage circuit 220 of the subsequent stage has been disabled and the isolation switch 232 has also been turned off, the transient noise caused by the switching of the preamplifier circuit 210 does not reflect on the audio output signal S_AO.
根據上述的訊號時序,由於前級的前置放大電路210與後級的輸出級電路220係以具順序性且有間隔地致/禁能,並且前置放大電路210所輸出的音訊放大訊號S_AMP會同步地配合輸出級電路220的致能時序而被提供至輸出級電路220(透過控制隔離開關232的導通狀態來實現),因此無論在電源啟動或電源關閉時,前置放大電路210的切換皆不會對音訊輸出訊號S_AO造成影響。換言之,音訊放大器200並不會因為回授至輸入端的音訊輸出訊號S_AO而發生前後級電路相互拉扯的回授效應,從而令音訊輸出訊號S_AO的暫態雜訊可被有效地抑制。 According to the above signal timing, since the preamplifier circuit 210 of the preceding stage and the output stage circuit 220 of the subsequent stage are sequentially/disabled/disabled, and the audio amplification signal S_AMP output by the preamplifier circuit 210 The timing of the enable of the output stage circuit 220 is synchronously provided to the output stage circuit 220 (implemented by controlling the conduction state of the isolation switch 232), so that the switching of the preamplifier circuit 210 is performed whether the power is turned on or the power is turned off. No impact on the audio output signal S_AO. In other words, the audio amplifier 200 does not cause a feedback effect of the front and rear circuits pulling each other due to the audio output signal S_AO being fed back to the input terminal, so that the transient noise of the audio output signal S_AO can be effectively suppressed.
於此值得一提的是,所述禁能準位L與致能準位H可分別為接地準位GND與偏壓準位Vdd,惟其係可由設計者依據電路設計需求而自行設計,本發明對此不加以限制。 It is worth mentioning that the disable level L and the enable level H can be the ground level GND and the bias level Vdd, respectively, but the design can be designed by the designer according to the circuit design requirements. There is no restriction on this.
底下以圖4來進一步說明所述音訊放大器的具體實施範例,其中,圖4為本發明一實施例的音訊放大器的電路架構示意 圖。在本實施例中,音訊放大器400同樣會透過電阻Rf而將音訊輸出訊號S_AO回授至輸入端,藉以保持音訊輸出訊號S_AO的穩定。此外,音訊放大器400會接收音訊輸入訊號S_AI(經由輸入電阻Ri)、參考電壓VCM以及電源啟動訊號PU,並且基於上述訊號進行音訊放大的動作。 A specific implementation example of the audio amplifier is further illustrated in FIG. 4, wherein FIG. 4 is a schematic diagram of a circuit architecture of an audio amplifier according to an embodiment of the present invention. Figure. In this embodiment, the audio amplifier 400 also feeds the audio output signal S_AO to the input terminal through the resistor Rf, thereby maintaining the stability of the audio output signal S_AO. In addition, the audio amplifier 400 receives the audio input signal S_AI (via the input resistor Ri), the reference voltage VCM, and the power-on signal PU, and performs an audio amplification operation based on the above signal.
請參照圖4,本實施例的音訊放大器400包括前置放大電路410、輸出級電路420以及延遲開關電路430。其中,前置放大電路410包括前置放大器412、輸出控制級414以及偏壓單元416。延遲開關電路430包括隔離開關432_1、432_2以及延遲單元434。在本實施例中,前置放大電路410以及輸出級電路420係以差動電路的架構做為範例(前置放大電路410會輸出差動的音訊放大訊號S_AMP與S_AMPb(即,S_AMP與S_AMPb互為反相),而輸出級電路420會基於差動的音訊放大訊號S_AMP與S_AMPb轉換出音訊輸出訊號S_AO),因此延遲開關電路430中設置有兩個分別對應於前置放大電路410的差動輸出的隔離開關432_1與432_2,以對應地接收差動的音訊放大訊號S_AMP、S_AMPb,但本發明不僅限於此。在單端輸出的實施例中,延遲開關電路430僅需設置單一隔離開關即可(如前述圖2實施例)。 Referring to FIG. 4, the audio amplifier 400 of the present embodiment includes a preamplifier circuit 410, an output stage circuit 420, and a delay switch circuit 430. The preamplifier circuit 410 includes a preamplifier 412, an output control stage 414, and a biasing unit 416. The delay switch circuit 430 includes isolation switches 432_1, 432_2 and a delay unit 434. In the present embodiment, the preamplifier circuit 410 and the output stage circuit 420 are exemplified by the architecture of the differential circuit (the preamplifier circuit 410 outputs the differential audio amplification signals S_AMP and S_AMPb (ie, S_AMP and S_AMPb are mutually exclusive). In order to invert), the output stage circuit 420 converts the audio output signal S_AO based on the differential audio amplification signals S_AMP and S_AMPb, so that the delay switch circuit 430 is provided with two differentials respectively corresponding to the preamplifier circuit 410. The output isolation switches 432_1 and 432_2 are correspondingly received to receive the differential audio amplification signals S_AMP, S_AMPb, but the present invention is not limited thereto. In the single-ended output embodiment, the delay switch circuit 430 only needs to provide a single isolation switch (as in the previous embodiment of Figure 2).
詳細而言,在前置放大電路410中,前置放大器412從其負輸入端接收音訊輸入訊號S_AI以及經由電阻Rf回授的音訊輸出訊號S_AO並從其正輸入端接收參考電壓VCM,並據以於其輸出端產生差動放大訊號S_A與S_Ab(訊號S_A與S_Ab互為反 相)。輸出控制級414耦接前置放大器412的輸出端,用以依據前置放大器412所輸出的差動放大訊號S_A與S_Ab而產生差動的音訊放大訊號S_AMP與S_AMPb。偏壓單元416則係用以提供前置放大器412與輸出控制級414運作所需的工作電壓VB1與VB2。 In detail, in the preamplifier circuit 410, the preamplifier 412 receives the audio input signal S_AI from its negative input terminal and the audio output signal S_AO fed back via the resistor Rf and receives the reference voltage VCM from its positive input terminal, and according to The differential amplification signals S_A and S_Ab are generated at the output end (the signals S_A and S_Ab are opposite each other) phase). The output control stage 414 is coupled to the output of the preamplifier 412 for generating differential audio amplification signals S_AMP and S_AMPb according to the differential amplification signals S_A and S_Ab output by the preamplifier 412. The biasing unit 416 is used to provide the operating voltages VB1 and VB2 required for the operation of the preamplifier 412 and the output control stage 414.
另一方面,延遲單元434會以如圖3實施例的訊號時序來提供前級控制訊號PUF與後級控制訊號PUO以控制前置放大器412、輸出控制級414、輸出級電路420以及隔離開關432_1、432_2的運作,藉以依序且有間隔地致/禁能前置放大電路410與輸出級電路420,並且同步地導通/截止隔離開關432_1、432_2,從而令輸出級電路420所產生的音訊輸出訊號S_AO的暫態雜訊可被有效地抑制。 On the other hand, the delay unit 434 provides the pre-control signal PUF and the post-control signal PUO to control the preamplifier 412, the output control stage 414, the output stage circuit 420, and the isolation switch 432_1 in the signal timing of the embodiment of FIG. The operation of the 432_2, in order to enable/disable the preamplifier circuit 410 and the output stage circuit 420, and synchronously turn on/off the isolating switches 432_1, 432_2, thereby causing the audio output generated by the output stage circuit 420 The transient noise of the signal S_AO can be effectively suppressed.
更詳細地說,在本實施例中,輸出控制級414是以浮接電流源組態(floating current source configuration)所構成的電路架構為例,而輸出級電路420則是以推挽式組態(push-pull configuration)所構成的電路架構為例。以下就輸出控制級414以及輸出級電路420的具體電路架構做進一步的描述。 In more detail, in the present embodiment, the output control stage 414 is a circuit architecture composed of a floating current source configuration, and the output stage circuit 420 is a push-pull configuration. (push-pull configuration) The circuit architecture is taken as an example. The specific circuit architecture of the output control stage 414 and the output stage circuit 420 is further described below.
以浮接電流源組態所構成的輸出控制器414包括電晶體M1~M4、Mp1、Mn1以及電流源CS1、CS2。其中,電晶體Mp1(以p型電晶體為例)的源極耦接電晶體Mn1(以n型電晶體為例)的汲極,電晶體Mp1的汲極耦接電晶體Mn1的源極,且電晶體Mp1與Mn1的閘極分別接收偏壓單元416所提供的工作電壓VB1與VB2。 The output controller 414, which is constructed in a floating current source configuration, includes transistors M1 to M4, Mp1, Mn1, and current sources CS1, CS2. Wherein, the source of the transistor Mp1 (taking a p-type transistor as an example) is coupled to the drain of the transistor Mn1 (taking an n-type transistor as an example), and the drain of the transistor Mp1 is coupled to the source of the transistor Mn1, And the gates of the transistors Mp1 and Mn1 receive the operating voltages VB1 and VB2 provided by the biasing unit 416, respectively.
電流源CS1耦接於偏壓VDD與電晶體Mp1的源極和電晶體Mn1的汲極之間,並且受控於前置放大器412所輸出的訊號S_A。電流源CS2耦接於電晶體Mp1的汲極和電晶體Mn1的源極與接地準位GND之間,並且受控於前置放大器412所輸出的訊號S_Ab。 The current source CS1 is coupled between the bias voltage VDD and the source of the transistor Mp1 and the drain of the transistor Mn1, and is controlled by the signal S_A output by the preamplifier 412. The current source CS2 is coupled between the drain of the transistor Mp1 and the source of the transistor Mn1 and the ground level GND, and is controlled by the signal S_Ab output by the preamplifier 412.
電晶體M1~M4係以n型電晶體為例,其中電晶體M1的汲極耦接偏壓VDD,電晶體M1的源極耦接電流源CS1的控制端,並且電晶體M1的閘極接收前級控制訊號PUF。電晶體M2的汲極耦接偏壓VDD,電晶體M2的源極耦接電晶體Mp1的閘極,並且電晶體M2的閘極接收前級控制訊號PUF。電晶體M3的汲極耦接電晶體Mn1的閘極,電晶體M3的源極耦接接地準位GND,並且電晶體M3的閘極接收與前級控制訊號PUF互為反相的訊號PUFb(於此稱之為反相前級控制訊號PUFb)。電晶體M4的汲極耦接電流源CS2的控制端,電晶體M4的源極耦接接地準位GND,並且電晶體M4的閘極接收反相前級控制訊號PUFb。於此值得一提的是,本實施例的電晶體M1~M4的架構可用以防止斷電漏電流(power-down leakage current)的發生。 The transistor M1~M4 is exemplified by an n-type transistor, wherein the gate of the transistor M1 is coupled to the bias voltage VDD, the source of the transistor M1 is coupled to the control terminal of the current source CS1, and the gate of the transistor M1 is received. The pre-control signal PUF. The drain of the transistor M2 is coupled to the bias voltage VDD, the source of the transistor M2 is coupled to the gate of the transistor Mp1, and the gate of the transistor M2 receives the previous stage control signal PUF. The gate of the transistor M3 is coupled to the gate of the transistor Mn1, the source of the transistor M3 is coupled to the grounding level GND, and the gate of the transistor M3 receives the signal PUFb which is opposite to the pre-stage control signal PUF ( This is referred to herein as the inverted pre-stage control signal PUFb). The gate of the transistor M4 is coupled to the control terminal of the current source CS2, the source of the transistor M4 is coupled to the ground level GND, and the gate of the transistor M4 receives the inverted pre-stage control signal PUFb. It is worth mentioning here that the architecture of the transistors M1 to M4 of the present embodiment can be used to prevent the occurrence of a power-down leakage current.
以推挽式組態所構成的輸出級電路420包括電晶體M5、M6、Mp2、Mn2以及電容C1、C2。其中,電晶體Mp2(以p型電晶體為例)的源極耦接偏壓VDD,並且電晶體Mp2的汲極耦接電晶體Mn1(以n型電晶體為例)的汲極。電晶體Mn2的源極耦接接地準位GND,並且電晶體Mp2與Mn2的閘極分別經由隔離 開關432_1與432_2接收音訊放大訊號S_AMP以及與音訊放大訊號S_AMP互為反相的訊號S_AMPb(於此稱之為反相音訊放大訊號S_AMPb) The output stage circuit 420 constructed in a push-pull configuration includes transistors M5, M6, Mp2, Mn2 and capacitors C1, C2. The source of the transistor Mp2 (taking a p-type transistor as an example) is coupled to the bias voltage VDD, and the drain of the transistor Mp2 is coupled to the drain of the transistor Mn1 (exemplified by an n-type transistor). The source of the transistor Mn2 is coupled to the grounding level GND, and the gates of the transistors Mp2 and Mn2 are respectively isolated. The switches 432_1 and 432_2 receive the audio amplification signal S_AMP and the signal S_AMPb which is mutually inverted with the audio amplification signal S_AMP (referred to herein as the inverted audio amplification signal S_AMPb)
電晶體M5(以p型電晶體為例)的源極耦接偏壓VDD,電晶體M5的源極耦接偏壓VDD,並且電晶體M5的汲極耦接電晶體Mp2的閘極。電晶體M6(以n型電晶體為例)的汲極耦接電晶體Mn2的閘極,電晶體M6的源極耦接接地準位GND,並且電晶體M5與M6的閘極分別接收後級控制訊號PUO以及與後級控制訊號PUO互為反相的訊號PUOb(於此稱之為反相後級控制訊號PUOb)。 The source of the transistor M5 (for example, a p-type transistor) is coupled to the bias voltage VDD, the source of the transistor M5 is coupled to the bias voltage VDD, and the drain of the transistor M5 is coupled to the gate of the transistor Mp2. The gate of the transistor M6 (for example, an n-type transistor) is coupled to the gate of the transistor Mn2, the source of the transistor M6 is coupled to the grounding level GND, and the gates of the transistors M5 and M6 are respectively received by the subsequent stage. The control signal PUO and the signal PUOb (referred to herein as the inverted post-stage control signal PUOb) which are mutually inverted with the subsequent control signal PUO.
電容C1與C2分別耦接於電晶體Mp2與Mn2的閘極與汲極之間,以補償輸出級電路420的電容效應。應注意的是,利用電容C1與C2來補償輸出級電路420的電容效應僅為本發明之一實施範例。於其他實施例中,輸出級電路420亦可採用疊接電路補償(cascode)、遲滯電流補償(HCC)或其他補償機制來補償輸出級電路420的電容效應,本發明不僅限於此。 The capacitors C1 and C2 are respectively coupled between the gates and the drains of the transistors Mp2 and Mn2 to compensate for the capacitance effect of the output stage circuit 420. It should be noted that utilizing capacitors C1 and C2 to compensate for the capacitive effects of output stage circuit 420 is only one embodiment of the present invention. In other embodiments, the output stage circuit 420 can also compensate for the capacitive effect of the output stage circuit 420 by using cascode, hysteresis current compensation (HCC), or other compensation mechanisms, and the present invention is not limited thereto.
基於圖4的電路架構下,音訊放大器400的輸出特性可如圖5A與5B所示。其中,圖5A係繪示本發明實施例的音訊放大器400與傳統音訊放大器(不包含延遲開關模組430)的頻寬與雜訊強度的相對關係,而圖5B係繪示本發明實施例的音訊放大器400與傳統音訊放大器的頻寬與總諧波加雜訊特性(THD+N)的相對關係。請先參照圖5A,特性曲線CL1表示本發明實施例的音 訊放大器400所輸出的音訊輸出訊號S_AO的頻寬與雜訊強度的相對關係,而特性曲線CL2則係表示傳統音訊放大器的頻寬與雜訊強度的相對關係。 Based on the circuit architecture of Figure 4, the output characteristics of the audio amplifier 400 can be as shown in Figures 5A and 5B. 5A illustrates the relative relationship between the bandwidth and the noise strength of the audio amplifier 400 and the conventional audio amplifier (excluding the delay switch module 430), and FIG. 5B illustrates the embodiment of the present invention. The relationship between the bandwidth of the audio amplifier 400 and the conventional audio amplifier and the total harmonic plus noise characteristic (THD+N). Referring first to FIG. 5A, the characteristic curve CL1 represents the sound of the embodiment of the present invention. The relationship between the bandwidth of the audio output signal S_AO outputted by the amplifier 400 and the noise intensity, and the characteristic curve CL2 indicates the relative relationship between the bandwidth of the conventional audio amplifier and the noise intensity.
詳細而言,在傳統音訊放大器中,其僅能藉由降低電路頻寬的方式來抑制音訊輸出訊號的暫態雜訊。由特性曲線CL2可知,當傳統音訊放大器維持在高頻寬時(例如72.17MHz),其音訊輸出訊號的雜訊強度會高達88.5mV。而藉由降低約64%的頻寬可使音訊輸出訊號的雜訊強度降低約75%(從88.5mV降至22.48mV),但此時傳統音訊放大器的頻寬僅剩20.49MHz。 In detail, in a conventional audio amplifier, it can only suppress transient noise of an audio output signal by reducing the bandwidth of the circuit. It can be seen from the characteristic curve CL2 that when the conventional audio amplifier is maintained at a high frequency (for example, 72.17 MHz), the noise intensity of the audio output signal is as high as 88.5 mV. By reducing the bandwidth by about 64%, the noise intensity of the audio output signal can be reduced by about 75% (from 88.5mV to 22.48mV), but the bandwidth of the conventional audio amplifier is only 20.49MHz.
相較之下,由特性曲線CL1可知,在音訊放大器400的架構下,其於高頻寬時(例如77.21MHz)時的雜訊強度僅約43.23mV,較之傳統音訊放大器在相近頻寬時低約45.27mV。換言之,相較於傳統音訊放大器而言,本發明實施例的音訊放大器400可在無須降低頻寬的情況下減少約50%的雜訊強度。此外,當音訊放大器400降低約64%的頻寬時,可使音訊輸出訊號S_AO的雜訊強度降低約82%(從43.23mV降至7.794mV)。 In comparison, the characteristic curve CL1 shows that under the structure of the audio amplifier 400, the noise intensity at a high frequency width (for example, 77.21 MHz) is only about 43.23 mV, which is lower than that of a conventional audio amplifier. 45.27mV. In other words, the audio amplifier 400 of the embodiment of the present invention can reduce the noise intensity by about 50% without reducing the bandwidth compared to the conventional audio amplifier. In addition, when the audio amplifier 400 is reduced by about 64% of the bandwidth, the noise intensity of the audio output signal S_AO can be reduced by about 82% (from 43.23 mV to 7.794 mV).
另一方面,以總諧波加雜訊特性(於此以THD+N特性稱之)來看,如圖5B所示,其中特性曲線CL3表示本發明實施例的音訊放大器400所輸出的音訊輸出訊號S_AO的頻寬與THD+N特性的相對關係,而特性曲線CL4則係表示傳統音訊放大器的頻寬與THD+N的相對關係。 On the other hand, in terms of total harmonics plus noise characteristics (referred to herein as THD+N characteristics), as shown in FIG. 5B, the characteristic curve CL3 represents the audio output output by the audio amplifier 400 of the embodiment of the present invention. The relationship between the bandwidth of the signal S_AO and the THD+N characteristic, and the characteristic curve CL4 represents the relative relationship between the bandwidth of the conventional audio amplifier and THD+N.
在圖5B中,可發現特性曲線CL3與CL4兩者大致重合, 意即,音訊放大器400與傳統音訊放大器的THD+N特性相近。換言之,即使增加了延遲開關電路430也不會造成整體音訊放大器400的線性度(linearity)發生顯著的劣化。 In FIG. 5B, it can be found that the characteristic curves CL3 and CL4 substantially coincide, That is, the audio amplifier 400 is similar to the THD+N characteristic of the conventional audio amplifier. In other words, even if the delay switch circuit 430 is added, the linearity of the overall audio amplifier 400 is not significantly deteriorated.
於此應注的是,雖然本實施例係以浮接電流源組態所構成的輸出控制級414以及以推挽式組態所構成的輸出級電路420做為實施範例,但本發明不僅限於此。更具體地說,只要是任何兩級式的音訊放大器架構(例如A類放大器、B類放大器或AB類放大器)皆可藉由圖2實施例的配置與圖3實施例的控制時序而獲得類似於圖5A與圖5B之特性曲線。 It should be noted that although the present embodiment is an output control stage 414 composed of a floating current source configuration and an output stage circuit 420 constructed by a push-pull configuration, the present invention is not limited to the embodiment. this. More specifically, any two-stage audio amplifier architecture (such as a class A amplifier, a class B amplifier, or a class AB amplifier) can be similarly obtained by the configuration of the embodiment of FIG. 2 and the control timing of the embodiment of FIG. The characteristic curves of Fig. 5A and Fig. 5B.
圖6為本發明一實施例的音訊放大器的暫態雜訊抑制方法的步驟流程圖。本實施例的暫態雜訊抑制方法適用於如圖2或圖4所示之包括前置放大電路(如210、410)以及輸出級電路(如220、420)的音訊放大器(如200、400)。所述暫態雜訊抑制方法包括以下步驟:依據電源啟動訊號而提供用以控制前置放大電路的前級控制訊號與用以控制輸出級電路的後級控制訊號,從而令前置放大電路與輸出級電路間隔延遲期間依序致能或禁能(步驟S610);以及基於後級控制訊號而決定是否將前置放大電路所產生的音訊放大訊號提供至輸出級電路(步驟S620)。 FIG. 6 is a flow chart showing the steps of a method for suppressing transient noise of an audio amplifier according to an embodiment of the present invention. The transient noise suppression method of this embodiment is applicable to an audio amplifier (such as 200, 400) including a preamplifier circuit (such as 210, 410) and an output stage circuit (such as 220, 420) as shown in FIG. 2 or FIG. ). The method for suppressing transient noise includes the following steps: providing a pre-control signal for controlling a preamplifier circuit and a post-level control signal for controlling an output stage circuit according to a power-on signal, thereby preamplifying the circuit and The output stage circuit interval delay period is sequentially enabled or disabled (step S610); and determining whether to provide the audio amplification signal generated by the preamplifier circuit to the output stage circuit based on the subsequent stage control signal (step S620).
更具體地說,當電源啟動訊號從禁能準位切換至致能準位時(即,電子裝置從關閉狀態啟動),在上述步驟S610與S620中,會提供與電源啟動訊號同步的前級控制訊號,以先致能前置放大電路,並且提供基於延遲前級控制訊號所產生的後級控制訊 號,以於延遲期間後再致能輸出級電路並同時將音訊放大訊號提供至輸出級電路(如圖2實施例,可利用導通隔離開關232的方式來實現)。 More specifically, when the power-on signal is switched from the disable level to the enable level (ie, the electronic device is activated from the off state), in the above steps S610 and S620, a pre-stage synchronized with the power-on signal is provided. Controlling the signal to enable the preamplifier circuit and providing a post-control signal based on the delayed pre-control signal No., after the delay period, the output stage circuit is enabled and the audio amplification signal is simultaneously supplied to the output stage circuit (as shown in the embodiment of FIG. 2, the conduction switch 232 can be used).
另一方面,當電源啟動訊號從一致能準位切換至一禁能準位時,在上述步驟S610與S620中,會提供與電源啟動訊號同步的後級控制訊號,以先禁能輸出級電路並同時停止將音訊放大訊號提供至輸出級電路(如圖2實施例,可利用截止隔離開關232的方式來實現),並且提供基於延遲後級控制訊號所產生的前級控制訊號,以於延遲期間後再禁能前置放大電路。 On the other hand, when the power-on signal is switched from the consistent level to a disable level, in the above steps S610 and S620, a subsequent control signal synchronized with the power-on signal is provided to disable the output stage circuit. At the same time, the audio amplification signal is stopped from being supplied to the output stage circuit (as shown in the embodiment of FIG. 2, which can be implemented by means of the cut-off isolation switch 232), and the pre-control signal generated based on the delayed-stage control signal is provided to delay The preamplifier circuit is disabled after the period.
其中,圖6實施例所述之暫態雜訊抑制方法可根據前述圖2至圖5的說明而獲得充足的支持與教示,故相似或重複之處於此不再贅述。 The method for suppressing the transient noise according to the embodiment of FIG. 6 can obtain sufficient support and teaching according to the foregoing description of FIG. 2 to FIG. 5, and thus similarities or repetitions are not described herein again.
綜上所述,本發明實施例提出一種音訊放大器及應用其之電子裝置與暫態雜訊抑制方法。所述音訊放大器可藉由具順序性且有間隔地致/禁能方式來控制前級的前置放大電路與後級的輸出級電路,並且同步地配合輸出級電路的致能時序而將前置放大電路所輸出的音訊放大訊號提供至輸出級電路。基此,無論在電源啟動或電源關閉時,前置放大電路的切換皆不會對輸出級電路所輸出的音訊輸出訊號造成影響,故音訊放大器的暫態雜訊可在無須降低電路頻寬的前提下而有效地降低/抑制,進而提高使用者收聽的品質與舒適度。 In summary, the embodiments of the present invention provide an audio amplifier and an electronic device and a transient noise suppression method using the same. The audio amplifier can control the preamplifier circuit of the preamplifier and the output stage circuit of the subsequent stage by a sequential and interval inducing/disabling manner, and synchronously cooperate with the enable timing of the output stage circuit to The audio amplification signal outputted by the amplifier circuit is supplied to the output stage circuit. Therefore, the switching of the preamplifier circuit does not affect the audio output signal outputted by the output stage circuit when the power is turned on or the power is turned off, so the transient noise of the audio amplifier can be reduced without reducing the circuit bandwidth. Under the premise, it is effectively reduced/suppressed, thereby improving the quality and comfort of the user.
雖然本發明已以實施例揭露如上,然其並非用以限定本 發明,任何所屬技術領域中具有通常知識者,在不脫離本發明的精神和範圍內,當可作些許的更動與潤飾,故本發明的保護範圍當視後附的申請專利範圍所界定者為準。 Although the present invention has been disclosed above by way of example, it is not intended to limit the present invention. The scope of the present invention is defined by the scope of the appended claims, which are defined by the scope of the appended claims, without departing from the spirit and scope of the invention. quasi.
20‧‧‧電子裝置 20‧‧‧Electronic devices
200‧‧‧音訊放大器 200‧‧‧Audio Amplifier
210‧‧‧前置放大電路 210‧‧‧Preamplifier circuit
212‧‧‧前置放大器 212‧‧‧Preamplifier
214‧‧‧輸出控制級 214‧‧‧Output control level
216‧‧‧偏壓單元 216‧‧‧bias unit
220‧‧‧輸出級電路 220‧‧‧Output stage circuit
230‧‧‧延遲開關電路 230‧‧‧Delay switch circuit
232‧‧‧隔離開關 232‧‧‧Isolation switch
234‧‧‧延遲單元 234‧‧‧Delay unit
Cc‧‧‧隔離電容 Cc‧‧‧Isolation Capacitor
FB‧‧‧回授電路 FB‧‧‧ feedback circuit
LD‧‧‧揚聲器 LD‧‧‧ Speaker
PU‧‧‧電源啟動訊號 PU‧‧‧Power start signal
PUF‧‧‧前級控制訊號 PUF‧‧‧pre-control signal
PUO‧‧‧後級控制訊號 PUO‧‧‧After control signal
Rf‧‧‧電阻 Rf‧‧‧resistance
S1‧‧‧第一訊號 S1‧‧‧ first signal
S2‧‧‧第二訊號 S2‧‧‧ second signal
S_AI‧‧‧音訊輸入訊號 S_AI‧‧‧ audio input signal
S_AMP、S_AMP’‧‧‧音訊放大訊號 S_AMP, S_AMP’‧‧‧ audio amplification signal
S_AO‧‧‧音訊輸出訊號 S_AO‧‧‧ audio output signal
VCM‧‧‧參考電壓 VCM‧‧‧ reference voltage
Claims (11)
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