WO2007110556A1 - Commande de puissance d'amplificateur - Google Patents

Commande de puissance d'amplificateur Download PDF

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Publication number
WO2007110556A1
WO2007110556A1 PCT/GB2006/001131 GB2006001131W WO2007110556A1 WO 2007110556 A1 WO2007110556 A1 WO 2007110556A1 GB 2006001131 W GB2006001131 W GB 2006001131W WO 2007110556 A1 WO2007110556 A1 WO 2007110556A1
Authority
WO
WIPO (PCT)
Prior art keywords
amplifier
gain
input
amplification stage
signal
Prior art date
Application number
PCT/GB2006/001131
Other languages
English (en)
Inventor
Richard Peter Apsey
Original Assignee
Agere Systems Uk 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 Agere Systems Uk Ltd. filed Critical Agere Systems Uk Ltd.
Priority to PCT/GB2006/001131 priority Critical patent/WO2007110556A1/fr
Publication of WO2007110556A1 publication Critical patent/WO2007110556A1/fr
Priority to GB0818986A priority patent/GB2450063A/en

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0088—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using discontinuously variable devices, e.g. switch-operated
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3005—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers
    • H03G3/3026—Automatic control in amplifiers having semiconductor devices in amplifiers suitable for low-frequencies, e.g. audio amplifiers the gain being discontinuously variable, e.g. controlled by switching
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H03G3/342—Muting when some special characteristic of the signal is sensed which distinguishes it from noise, e.g. using speech detector

Definitions

  • the invention relates to variable gain amplifiers, and particularly to controlling the adjustment of the gain in such amplifiers.
  • Variable gain amplifiers are used, for example, in order to drive a loudspeaker in apparatus such as telephone handsets.
  • the gain of an amplifier driving a loudspeaker may be adjusted, for example, responsive to a user of a telephone handset adjusting the speaker volume.
  • variable gain amplifiers for driving loudspeakers, are typically analogue amplifiers, the gain of which is typically coarse resulting in a step-wise change for any adjustment in gain.
  • Such a step-wise change results in an abrupt change in the volume of an audio signal produced by the driven speaker, which causes an audible ⁇ click' or ⁇ pop' . This is undesirable from a user perspective.
  • a digital signal processor is used to ramp the volume in small steps over a period of time.
  • a method of controlling gain adjustment in an amplification stage including an amplifier comprising the steps of: muting the amplifier; and whilst the amplifier is muted, adjusting the amplifier gain.
  • an input to the amplifier is muted.
  • the output of the amplifier is muted.
  • the muted input to the amplifier is the input providing a signal to be amplified.
  • the step of muting thus preferably comprises muting the signal to be amplified by the amplifier.
  • the step of adjusting the gain of the amplifier preferably comprises a step adjustment.
  • the size of the step may be implementation dependent.
  • the gain is preferably adjustable up or down in such step size.
  • the step of muting the input to the amplifier preferably comprises ramping down the input to the amplifier.
  • the input to the amplifier is thus not adjusted in a stepwise manner, but in a smooth transition.
  • the step of muting the output of the amplifier preferably comprises ramping down the output provided by the amplifier.
  • the output of the amplifier is thus not adjusted in a step-wise manner, but in a smooth ⁇ transition.
  • the ramping down is preferably achieved in a post-amplification stage.
  • the method may further include the step of ramping up the input to the amplifier.
  • the method may further include the step of ramping up the output of the amplifier.
  • the ramping up is preferably achieved in a post-amplification stage.
  • the input to the amplifier may be ramped up to its original level .
  • the input to the amplifier may be ramped up to a level different to its original level . That level may be above or below the original level .
  • the input to the amplifier may be provided by a preamplifier, the method additionally comprising controlling the gain of the pre-amplifier in order to mute the input to the amplifier.
  • the method may comprise the step of adjusting the gain of the pre-amplifier input to the amplifier in order that the input to the amplifier may be ramped up to a level different to its original level.
  • the step of adjusting the gain of the pre-amplifier is preferably dependent on a gain adjustment step allowable for the amplifier, to achieve an overall desired gain for the amplification stage.
  • the gain of the preamplifier is adjusted in combination with an adjustment of the gain of the amplifier, to achieve a desired gain for the amplification stage.
  • a controller is preferably provided to determine the gain adjustment for the amplifier and the pre-amplifier in dependence on a desired gain adjustment for the amplification stage and the step gain adjustment allowable for the amplifier. If the overall gain adjustment of the amplification stage is divisible by the gain step adjustment of the amplifier, then preferably the gain of the pre-amplifier is not adjusted.
  • an amplification stage comprising: an amplifier having an adjustable gain and having an input for receiving an input signal to be amplified; a controller for muting the amplifier whilst adjusting the gain of the amplifier.
  • the controller is adapted to mute the input to the amplifier.
  • the gain of the amplifier is preferably adjustable in steps.
  • the controller is preferably arranged to mute the input to the amplifier by ramping down the input to the amplifier.
  • the controller is preferably arranged to restore the input to the amplifier by ramping up the input to the amplifier.
  • the controller is preferably arranged to restore the input to the amplifier to its original level.
  • the controller is preferably arranged to restore the input to the amplifier to a level different to its original level.
  • the amplification stage preferably comprises a pre- amplifier, the pre-amplifier being connected to provide the input to the amplifier under the control of the controller.
  • the controller is preferably further arranged to adjust the gain of the pre-amplifier in order to achieve an overall gain for the amplification stage.
  • the gain of the pre-amplifier preferably determines the level to which the ramped up signal returns.
  • the controller ' is preferably arranged to adjust the gain of the pre-amplifier only if the overall gain adjustment of the amplification stage is not divisible by the gain step adjustment available for the amplifier. If the result of the division of the overall gain adjustment of the amplification stage by the gain step adjustment available for the amplifier is not an integer, then the gain of the pre-amplifier is preferably adjusted by the remainder.
  • the amplifier is an analogue amplifier.
  • the pre-amplifier is a digital amplifier.
  • Figure 1 illustrates an amplification stage in which embodiments of the invention may be implemented
  • Figures 2 (a) to 2 (c) illustrate signal levels in the amplification stage of Figure 1 in accordance with an embodiment of the invention.
  • Figure 3 illustrates an example implementation of a controller in accordance with an embodiment of the invention.
  • Figure 1 illustrates an amplification stage 102 including a digital amplifier 106, an analogue amplifier 110, a digital to analogue converter 108 and a control means, control circuit, or controller 104. Also shown is a loudspeaker 124 which is driven by the amplification stage 102.
  • the amplification stage 102 receives an input signal on line 112 which forms a digital amplifier input signal for the digital amplifier 106.
  • the digital amplifier ' 106 generates a digital amplifier output signal on line 114.
  • the digital amplifier output signal on line 114 forms an input to the digital to analogue converter 108.
  • the digital to analogue converter 108 converts the digital amplifier output signal into an analogue signal on line 116.
  • the analogue signal on line 116 forms an analogue amplifier input signal for the analogue amplifier 110.
  • the analogue amplifier 110 generates an analogue amplifier output signal on line 118.
  • the analogue amplifier output signal on line 118 drives the speaker 124 to generate an audio signal.
  • the speaker may be a speaker of any device, for example a speaker in a telephone handset.
  • the amplification stage 102 of Figure 1 is further shown to include a controller 104.
  • the controller may in fact be a controller provided for control of the device or apparatus of which the amplification stage 102 forms a part, and is not necessarily a dedicated controller for the amplification stage.
  • the controller may, for example, be a digital signal processor of the apparatus of which the amplification stage forms a part.
  • the digital amplifier 106 and the analogue amplifier 110 both have adjustable gain.
  • the gain of each of the amplifiers 106 and 110 is controlled by the controller 104.
  • the controller 104 generates a control signal on line 120 for controlling the digital amplifier 106, and a control signal on line 122 for controlling the analogue amplifier 110.
  • the control signals 120 and 122 control the gain of the respective amplifiers.
  • the gain of the digital amplifier 106 is finely adjustable under the control of the control circuit 104.
  • the gain of the analogue amplifier 110 is coarsely adjustable under the control of the control circuit 104.
  • the control circuit 104 controls the gain of each of the amplifiers 106 and 110 in accordance with the techniques of the invention and embodiments thereof, to improve performance of the amplification stage 102 when the gain of the analogue amplifier 110 is adjusted.
  • the control circuit 104 receives information - or determines information - relating to the amplification to be applied to the signal for driving the speaker 124 in the amplification stage 102.
  • the control circuit controls the gain of each of the amplifiers 106 and 110 in order to adjust the gain of the amplification stage, in accordance with the invention and embodiments thereof.
  • the amplifier 106 preferably is a pre-amplifier stage for the amplifier 110.
  • Figure 2 (a) shows an example of the digital amplifier output signal on line 114 in a given scenario.
  • Figure 2 (b) shows an example, in the corresponding scenario, of the adjustment of the gain of the analogue amplifier 110.
  • Figure 2 (c) shows an example, in the_ corresponding scenario, of the analogue amplifier output signal on line 118.
  • each of the digital amplifier 106 and the analogue amplifier 110 are set with particular gain values to achieve an overall desired gain for the amplification stage 102.
  • the control circuit determines, or is informed, that the overall gain of the amplification stage 102 is to be reduced by a certain amount, for which it is required to reduce the gain of the analogue amplifier 110 by 6dB.
  • the control circuit 104 therefore controls the amplifier 106 via line 120 to reduce the gain thereof toward zero, such that the digital amplifier output signal on line 114 reduces down toward zero.
  • the gain level of the amplifier 106 is not shown in Figure 2. However the amplifier is a digital amplifier having fine gain control, and the gain is reduced by ramping down the gain toward zero.
  • a ⁇ s ⁇ the analogue amplifier output signal on line 11 ⁇ is zero at time ti, at time ti the speaker 124 is muted. The speaker is muted when the input signal to the amplifier
  • the audible signal 110 is brought to a sufficiently low level (which is then reflected in its output) , that the audible signal does not contain the click or pop.
  • This does not necessarily means that the input signal to the amplifier is brought to zero: it may be brought close to zero. In general it is brought low relative to its original level, such that some form of muting of the audible signal is achieved.
  • control circuit 104 then controls the analogue amplifier via control signal 122 to adjust the gain of the analogue amplifier 110 to the desired level.
  • the gain level of the analogue amplifier 110 is dropped by 6dB at time ti.
  • the digital amplifier output signal is reduced to a zero level at the time instant t Xr following a ramp-down from time t 0
  • the signal may be held at a zero level for a time sufficient to achieve the step-change in the analogue amplifier gain.
  • the digital amplifier output signal is preferably held at a zero level for a short time, e.g. 60ms.
  • the control circuit controls the digital amplifier 106 via control signal 120 to ramp-up the gain thereof, in this described embodiment, to its previous level.
  • the digital amplifier output signal on line 114 is ramped up until at time t 2 it reaches the previous value it held at time to. .
  • the digital amplifier gain may be ramped up to a different level than that which it previously held.
  • the muting of the input signal to the analogue amplifier whilst the gain of the analogue amplifier is adjusted means that no ⁇ click' or such like is heard on the speaker when the analogue amplifier gain is adjusted.
  • the gain of the stage it is preferable for the gain of the stage to be adjusted in the analogue amplifier 110 rather than the digital amplifier 106, which is preferably a pre-amplifier .
  • the gain of the digital amplifier is preferably maintained whilst the gain of the analogue amplifier is adjusted.
  • the digital amplifier output signal on line 114 is returned at time t 2 to its level at time t 0 , as the gain of the digital amplifier 106 has not been adjusted.
  • the digital amplifier output signal from the pre-amplifier is desirable to make the digital amplifier output signal from the pre-amplifier as large (i.e. loud) as possible, and then control the actual size (i.e. volume) of the output of the amplification stage 102 in the analogue amplifier 110.
  • a characteristic of the analogue amplifier 110 is that the gain can only be adjusted coarsely, in a step-wise manner. There will therefore be associated a resolution with the gain adjustment of the analogue amplifier 110.
  • the gain of the analogue amplifier may be adjustable only in 3dB steps.
  • the gain of the digital amplifier must be adjusted as well as the gain of the analogue amplifier. This would mean that at time t 2 the digital amplifier output signal on line 114, as shown in Figure 2 (a) , would not return to its level at time to, but would return to the appropriate level necessary to achieve the overall gain adjustment of the amplification stage 102. For example if it was required to reduce the gain of the amplification stage 102 by 5dB, then the gain of the analogue amplifier could be reduced by 3dB, and the gain of the digital amplifier reduced by 2dB, to provide the overall require gain reduction.
  • the controller 104 is adapted to adjust the gains of the digital and analogue amplifiers as appropriate, in order to achieve a desired overall gain for the amplification stage, whilst ensuring that where possible the gain control is achieved in the analogue amplifier.
  • the controller 104 includes a divider circuit or block 302, a processor 308, a pre-amplifier gain control block 310 and an amplifier gain control block 312.
  • the controller receives an ⁇ adjust gain' control signal ADJ GAIN on line 316. This signal is received at an input of the processor 316. There is also provided to the controller 104 a ⁇ gain adjustment value' signal GAIN ADJ on line 314.
  • the gain adjustment value signal identifies, in the embodiment, the adjustment to be made to the gain of the amplification stage 102.
  • the controller may determine """ the adjustment to the gain to be made based on a subtraction from a current gain value. The adjustment may require an increase or decrease in gain.
  • the gain adjustment value on line 314 is provided to the divider block 302.
  • the divider block divides the gain adjustment value by the step gain available in the amplifier 110.
  • the step gain of the amplifier 110 is, for example 3dB, if the gain thereof can only be adjusted in 3dB steps.
  • the integer part of the division result is provided on line 318 to the processor 308, and the fractional part of the division result is provided on line 320 to the processor 308.
  • the values on lines 318 and 320 provide the information as to the adjustments to be made to the gains of the preamplifier 106 and the amplifier 110.
  • the value on line 318 will be 1 (denoting a requirement for a change in gain of one step, ⁇ equivalent to 3 dB) and the value on line 320 will be 2 (denoting a requirement for a change in gain of 2dB) .
  • the direction in which the gain is to be changes may Be contained in the signal on line 316 or the signal on line 314. Where this information is in the signal on line 314 this signal may also be provided directly to the processor 308.
  • the processor 308 sends an instruction on line 326 to the pre-amplifier gain control block 310 to ramp down the gain of the preamplifier.
  • the preamplifier gain control block provides fine gain control for the preamplifier 106, and responsive to the signal on line 326 ramps the gain of the preamplifier down toward zero.
  • the processor 308 sends an instruction on line 332 to the amplifier gain control block 312 to adjust the gain of the amplifier 110. This signal may identify the number of steps by which the gain should be adjusted, and whether the adjustment is up or down.
  • the amplifier gain block 312 implements the step change in gain by applying the appropriate signal on line 122 to the amplifier 110.
  • the processor also sends a control signal on line 330 to the pre-amplifier gain block 310 to set the new gain value for the pre-amplifier 330.
  • the processor sends a control signal on line 328 to the preamplifier gain control block 310 to ramp-up the gain for the pre-amplifier 106.
  • the pre-amplifier gain control block 310 then ramps up the gain of the preamplifier using the control signal on line 120, until the gain value corresponding to the value on line 330 is reached.
  • the invention provides an improvement in an amplifier by muting the input thereto whilst the gain level is adjusted.
  • the muting is preferably achieved by control in the digital domain.
  • the invention is applicable to any amplifier where the gain control in the amplifier is coarse or step-wise, resulting in a sudden change in the gain of the amplifier in order to achieve any adjustment in gain.
  • the invention is described, in embodiments, as muting the input to the amplifier.
  • the output of the amplifier may be muted.
  • the pre-amplifier stage described herein is provided as a post-amplifier stage.
  • the post-amplifier would be required to have a fine-gain control in order to mute the output of the amplifier in a ramped, rather than stepped, manner.
  • a fine gain control amplifier is provided as the final stage of the amplification stage, then the problems discussed in the background section of the application would not necessarily arise, since the final amplification stage does not have the step change characteristic which gives rise to the problem addressed by the invention.
  • the invention is applied to an analogue amplifier, the input of which is muted whilst the gain thereof is adjusted.
  • the invention is also applicable to a digital amplifier, with the input to the digital amplifier being muted whilst the gain thereof is adjusted.
  • An example of a digital amplifier to which the invention may be applied is a so-called Class-D amplifier which drives a speaker with a PCM pulse code modulated) signal .
  • an analogue amplifier is provided by a digital amplifier, it may in fact be provided by an analogue amplifier having a fine gain control.
  • the amplification stage comprises an amplifier with adjustable gain, the input to which is controlled to be muted when the amplifier gain is adjusted.
  • an amplification stage including an amplifier with adjustable gain by using a pre- amplification stage to drive the amplifier, the gain of the pre-amplification stage being adjustable such that the signal at the input of the amplifier can be ramped down to achieve the muting.
  • the invention has application in any amplification scenario, but especially where an amplified analogue signal is used to drive a speaker and thereby generates an audio signal.
  • an amplified analogue signal is used to drive a speaker and thereby generates an audio signal.
  • no audible ''click' ' results as a result of a gain change.
  • the muting of the input signal to the amplifier results in a ⁇ soft/ interruption in the audio signal, rather than the ⁇ harsh' click.
  • the audio source ' digital volume is ramped down to zero, the system analogue gain stage (or stages) is then configured by switching between different fixed settings, to the new target level, and then the source volume is ramped up to the appropriate level.
  • the instantaneous analogue gain switches which result in the ⁇ click' or ⁇ pop' , thus occur when there is no signal present, and are thus eliminated. The best electrical noise performance is maintained.
  • the invention overcomes the prior art problems .
  • the source digital signal can be kept at a large amplitude, significantly reducing the effects of quantisation noise, whilst the analogue system gain stages after the digital to analogue converter attenuate or amplify the signal to the required level. During the analogue gain transition the signal level is continuously zero, and hence no zero- crossing detection mechanism is required.
  • the invention has been described herein by way of reference to particular example embodiments . The invention may be more generally applied than is described herein, and modification to any embodiment described is possible within the scope of the invention as defined by the appended claims .

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Control Of Amplification And Gain Control (AREA)

Abstract

La présente invention concerne un procédé et un appareil pour la commande de l'ajustement de puissance dans un étage d'amplification avec un amplificateur comprenant les étapes consistant à : bloquer automatiquement une entrée pour l'amplificateur, et pendant que l'entrée est bloquée, ajuster la puissance d'amplificateur. L'étape d'ajustement de la puissance de l'amplificateur comprend un ajustement progressif. L'étape de blocage automatique de l'entrée pour l'amplificateur comprend la décélération de l'entrée pour l'amplificateur.
PCT/GB2006/001131 2006-03-28 2006-03-28 Commande de puissance d'amplificateur WO2007110556A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/GB2006/001131 WO2007110556A1 (fr) 2006-03-28 2006-03-28 Commande de puissance d'amplificateur
GB0818986A GB2450063A (en) 2006-03-28 2008-10-16 Amplified gain control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/GB2006/001131 WO2007110556A1 (fr) 2006-03-28 2006-03-28 Commande de puissance d'amplificateur

Publications (1)

Publication Number Publication Date
WO2007110556A1 true WO2007110556A1 (fr) 2007-10-04

Family

ID=37102412

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2006/001131 WO2007110556A1 (fr) 2006-03-28 2006-03-28 Commande de puissance d'amplificateur

Country Status (2)

Country Link
GB (1) GB2450063A (fr)
WO (1) WO2007110556A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2507096A (en) * 2012-10-19 2014-04-23 Wolfson Microelectronics Plc Digital to analogue conversion
CN107666295A (zh) * 2016-07-27 2018-02-06 恩智浦有限公司 增益校准控制器

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5757940A (en) * 1994-01-24 1998-05-26 Fujitsu Limited Electric volume controller
US5915030A (en) * 1996-07-26 1999-06-22 Stmicroelectronics, Gmbh Electric muting circuit
EP0932253A2 (fr) * 1998-01-15 1999-07-28 Texas Instruments Incorporated Procédé et dispositif de modification progressive du gain
WO2001052409A1 (fr) * 2000-01-13 2001-07-19 Acoustic Technologies, Inc. Circuit silencieux doux

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5757940A (en) * 1994-01-24 1998-05-26 Fujitsu Limited Electric volume controller
US5915030A (en) * 1996-07-26 1999-06-22 Stmicroelectronics, Gmbh Electric muting circuit
EP0932253A2 (fr) * 1998-01-15 1999-07-28 Texas Instruments Incorporated Procédé et dispositif de modification progressive du gain
WO2001052409A1 (fr) * 2000-01-13 2001-07-19 Acoustic Technologies, Inc. Circuit silencieux doux

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"13. TONMEISTERTAGUNG MÜNCHEN 1984", November 1984, BILDUNGSWERK DES VERBANDS DEUTSCHER TONMEISTER, BERLIN, XP002406394 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2507096A (en) * 2012-10-19 2014-04-23 Wolfson Microelectronics Plc Digital to analogue conversion
GB2507096B (en) * 2012-10-19 2016-03-23 Cirrus Logic Int Semiconductor Ltd Digital/analogue conversion
US9515626B2 (en) 2012-10-19 2016-12-06 Cirrus Logic International Semiconductor Ltd. Digital/analogue conversion
CN107666295A (zh) * 2016-07-27 2018-02-06 恩智浦有限公司 增益校准控制器
CN107666295B (zh) * 2016-07-27 2023-10-24 恩智浦有限公司 增益校准控制器

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Publication number Publication date
GB2450063A (en) 2008-12-10
GB0818986D0 (en) 2008-11-26

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