WO2007087812A1 - Audio amplifier with speaker protection against transients - Google Patents

Audio amplifier with speaker protection against transients Download PDF

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Publication number
WO2007087812A1
WO2007087812A1 PCT/DK2007/050012 DK2007050012W WO2007087812A1 WO 2007087812 A1 WO2007087812 A1 WO 2007087812A1 DK 2007050012 W DK2007050012 W DK 2007050012W WO 2007087812 A1 WO2007087812 A1 WO 2007087812A1
Authority
WO
WIPO (PCT)
Prior art keywords
power amplifier
audio
output
audio signal
state
Prior art date
Application number
PCT/DK2007/050012
Other languages
French (fr)
Inventor
Christian M. Andersen
Original Assignee
Remedan Aps
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 Remedan Aps filed Critical Remedan Aps
Publication of WO2007087812A1 publication Critical patent/WO2007087812A1/en

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/72—Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
    • 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
    • H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
    • H03F1/305—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in case of switching on or off of a power supply
    • 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
    • H03F1/52—Circuit arrangements for protecting such amplifiers
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • 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
    • H03G3/348—Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits
    • 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

Definitions

  • This invention relates to audio power amplifiers for use in connection with e.g. a digitally controlled signal source such as a computer, in particular a personal computer or a laptop computer.
  • a digitally controlled signal source such as a computer, in particular a personal computer or a laptop computer.
  • Audio signals are stored as digital signals, e.g. on CDs, hard disks, in solid state, magnetic or optical memories etc. Audio signals are processed, stored and transmitted as digital signals. Digital signal sources are widely used as signal sources for audio signals and include CD players, digital radio receivers, MP3 players etc. Digital audio signals are processed digitally prior to being output as analogue signals to loudspeakers, headphones or other electro-acoustic transducer that generate audible sound signals to be presented to one or more listeners.
  • Digital controllers in general are at risk of entering error states, in which uncontrolled signals are fed to the audio power amplifier.
  • General purpose digital computers used for such purpose have an operating system and one or more dedicated or specialised programs and hardware operating under the control of the operating system.
  • uncontrolled and undesired signals such as DC and transients on the analogue output of the sound card of the computer can cause damage to the speakers.
  • the resulting sounds are unpleasant and unwanted.
  • both the operating system and the application programs running under the operating system can become unstable or hanging. In such uncontrolled conditions, too, undesired signals may occur at the input of the power amplifier.
  • US 6 122 749 discloses an audio peripheral device with a controller for power management.
  • the signal source is idling, i.e. signal input data is absent, the power amplifier will enter a low power sleep mode.
  • an audio power amplifier with an amplifier for amplifying a received audio signal and an output for outputting the amplified audio signal.
  • the audio power amplifier is controllable to assume an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, and the audio power amplifier further comprises an input for receiving a control signal, and the audio power amplifier is adapted to assume the active state or the mute state in dependence on the received control signal.
  • the audio power amplifier can be adapted to assume the active state for a predetermined period of time after a control signal has been received, and to assume the mute state if no control signal has been received during the predetermined period of time.
  • the power amplifier in order to keep the power amplifier "alive” the power amplifier is dependent on periodically receiving the control signal as a "keep alive" signal with a repetition time that is shorter than the predetermined period of time. If no control signal is received within the predetermined period of time, the power amplifier will be muted.
  • the audio power amplifier can be adapted to assume the mute state if the control signal is received.
  • the control signal is a "mute" signal, and in the absence of a control signal the power amplifier will be kept alive in its active state.
  • FIG. 1 illustrates an audio system according to the invention
  • Figure 2 shows a flow chart for a method according to the invention.
  • FIG 1 is illustrated an audio system 10 with a controller 11 and a power amplifier 13.
  • a hardware platform 12 is between the controller 11 and the power amplifier 13.
  • One or more speakers 14 are connected to outputs of the power amplifier 13.
  • the controller 11 can be a general purpose programmable computer such as a PC (personal computer) that is or can be suitably programmed, or it can be a specialised computer.
  • the controller 11 is a signal source that outputs analogue or digital audio signals originating from an internal source such as a hard disk or a CD, or are received through a wired or wireless connection such as broadcast, or otherwise.
  • the digital or analogue audio signals are fed to the hardware platform 12 and from there to the power amplifier 13.
  • the power amplifier provides output signals to the one or more speakers 14 to drive the speakers to output appropriate sound signals.
  • the hardware platform 12 serves to monitor the state of the computer 11 and to control the state of the power amplifier 13.
  • the following three situations are foreseen.
  • a first situation is when the system is started up. As default the power amplifier 13 will assume a "mute" state in which the power amplifier outputs no amplified audio signal to the output.
  • an application such as an NT service is started and the power amplifier is controlled to assume its active state, i.e. a state in which amplified audio signal is fed to the output and to the speakers.
  • a second situation is when the system is powered down, or the computer enters suspend or power-off modes.
  • the NT service or other application will control the power amplifier to assume the mute state, and the system will then shut down or hibernate or go on standby.
  • the first and second situations are the normal and controlled situations where the operating system and applications are operating properly. However, in operation unexpected situations may arise where the operating system or an application is "hanging", which in some situations may cause the computer to reboot. During reboot uncontrolled signals (DC, transient pulses etc.) may occur in the signal chain. If such signals reach the speakers they may cause damage to the speakers and unpleasant sounds. Therefore, the computer is monitored not only during start-up and power-down but also during the entire operating period. If a state or a condition is detected in which unwanted signals occur or might occur, the hardware platform 12 will send a control signal to the power amplifier to cause the power amplifier to assume its mute state.
  • FIG. 2 illustrates one embodiment of the method of the invention, which is carried out in the power amplifier.
  • the power amplifier is "monostable", and only when "keep alive" signals are received at intervals no longer than a predetermined period will the power amplifier stay in its active state. When a "keep alive" signal is not received by the power amplifier within the predetermined period the power amplifier will immediately assume its mute state.
  • the power amplifier is "bistable" and will only change state when a control signal is received.
  • the hardware platform 12 will send a control signal to the power amplifier 13 only when the power amplifier is to be switched between its active state and its mute state.
  • the power amplifier can be an analogue or a digital amplifier adapted to receive analogue or a digital input signals, respectively, and it can have any suitable number of channels.

Abstract

An audio power amplifier with an amplifier for amplifying a received audio signal and an output for outputting the amplified audio signal. The audio power amplifier is controllable to assume an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, and the audio power amplifier further comprises an input for receiving a control signal, and the audio power amplifier is adapted to assume the active state or the mute state in dependence on the received control signal. The power amplifier will assume its mute state if no control signal is received within a predetermined period of time.

Description

AUDIO AMPLIFIER WITH SPEAKER PROTECTION AGAINST TRANSIENTS
FIELD OF THE INVENTION
This invention relates to audio power amplifiers for use in connection with e.g. a digitally controlled signal source such as a computer, in particular a personal computer or a laptop computer.
BACKGROUND OF THE INVENTION
Today most audio signals are stored as digital signals, e.g. on CDs, hard disks, in solid state, magnetic or optical memories etc. Audio signals are processed, stored and transmitted as digital signals. Digital signal sources are widely used as signal sources for audio signals and include CD players, digital radio receivers, MP3 players etc. Digital audio signals are processed digitally prior to being output as analogue signals to loudspeakers, headphones or other electro-acoustic transducer that generate audible sound signals to be presented to one or more listeners.
Digital controllers in general are at risk of entering error states, in which uncontrolled signals are fed to the audio power amplifier. General purpose digital computers used for such purpose have an operating system and one or more dedicated or specialised programs and hardware operating under the control of the operating system. In connection with turn-on or shut-down of a computer connected to an audio power amplifier via an analogue audio cable, uncontrolled and undesired signals such as DC and transients on the analogue output of the sound card of the computer can cause damage to the speakers. The resulting sounds are unpleasant and unwanted. Likewise, during operation both the operating system and the application programs running under the operating system can become unstable or hanging. In such uncontrolled conditions, too, undesired signals may occur at the input of the power amplifier.
US 6 122 749 discloses an audio peripheral device with a controller for power management. When the signal source is idling, i.e. signal input data is absent, the power amplifier will enter a low power sleep mode.
SUMMARY OF THE INVENTION
The invention addresses the above problems and provides a solution thereto. In accordance with the invention there is provided an audio power amplifier with an amplifier for amplifying a received audio signal and an output for outputting the amplified audio signal. The audio power amplifier is controllable to assume an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, and the audio power amplifier further comprises an input for receiving a control signal, and the audio power amplifier is adapted to assume the active state or the mute state in dependence on the received control signal.
The audio power amplifier according can be adapted to assume the active state for a predetermined period of time after a control signal has been received, and to assume the mute state if no control signal has been received during the predetermined period of time. Thus, in order to keep the power amplifier "alive" the power amplifier is dependent on periodically receiving the control signal as a "keep alive" signal with a repetition time that is shorter than the predetermined period of time. If no control signal is received within the predetermined period of time, the power amplifier will be muted.
In an alternative embodiment the audio power amplifier can be adapted to assume the mute state if the control signal is received. In this case the control signal is a "mute" signal, and in the absence of a control signal the power amplifier will be kept alive in its active state.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates an audio system according to the invention, and
Figure 2 shows a flow chart for a method according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
In figure 1 is illustrated an audio system 10 with a controller 11 and a power amplifier 13. A hardware platform 12 is between the controller 11 and the power amplifier 13. One or more speakers 14 are connected to outputs of the power amplifier 13.
The controller 11 can be a general purpose programmable computer such as a PC (personal computer) that is or can be suitably programmed, or it can be a specialised computer. The controller 11 is a signal source that outputs analogue or digital audio signals originating from an internal source such as a hard disk or a CD, or are received through a wired or wireless connection such as broadcast, or otherwise. The digital or analogue audio signals are fed to the hardware platform 12 and from there to the power amplifier 13. The power amplifier provides output signals to the one or more speakers 14 to drive the speakers to output appropriate sound signals.
The hardware platform 12 serves to monitor the state of the computer 11 and to control the state of the power amplifier 13. The following three situations are foreseen. A first situation is when the system is started up. As default the power amplifier 13 will assume a "mute" state in which the power amplifier outputs no amplified audio signal to the output. When it has been established that the operating system and the relevant application programs are up and running properly, an application such as an NT service is started and the power amplifier is controlled to assume its active state, i.e. a state in which amplified audio signal is fed to the output and to the speakers.
A second situation is when the system is powered down, or the computer enters suspend or power-off modes. The NT service or other application will control the power amplifier to assume the mute state, and the system will then shut down or hibernate or go on standby.
The first and second situations are the normal and controlled situations where the operating system and applications are operating properly. However, in operation unexpected situations may arise where the operating system or an application is "hanging", which in some situations may cause the computer to reboot. During reboot uncontrolled signals (DC, transient pulses etc.) may occur in the signal chain. If such signals reach the speakers they may cause damage to the speakers and unpleasant sounds. Therefore, the computer is monitored not only during start-up and power-down but also during the entire operating period. If a state or a condition is detected in which unwanted signals occur or might occur, the hardware platform 12 will send a control signal to the power amplifier to cause the power amplifier to assume its mute state.
Figure 2 illustrates one embodiment of the method of the invention, which is carried out in the power amplifier. If it has been established that the operating system and the relevant application programs are up and running properly, and the power amplifier can operate safely, the hardware platform 12 periodically sends a control signal to the power amplifier controlling the power amplifier to stay active or "alive". Such a control signal is referred to as a "keep alive" signal, and as long as "keep alive" signals are received regularly, the power amplifier is kept "alive", i.e. operating. If a risk of the operating system becoming unstable or going down has been detected, or such condition has occurred, the power amplifier should assume its mute state, and the "keep alive" signal will therefore no longer be sent to the power amplifier. The power amplifier is "monostable", and only when "keep alive" signals are received at intervals no longer than a predetermined period will the power amplifier stay in its active state. When a "keep alive" signal is not received by the power amplifier within the predetermined period the power amplifier will immediately assume its mute state.
In another embodiment of the invention the power amplifier is "bistable" and will only change state when a control signal is received. In this embodiment the hardware platform 12 will send a control signal to the power amplifier 13 only when the power amplifier is to be switched between its active state and its mute state.
The power amplifier can be an analogue or a digital amplifier adapted to receive analogue or a digital input signals, respectively, and it can have any suitable number of channels.

Claims

Claims:
1. An audio power amplifier comprising
- an input for receiving an audio signal, - an amplifier for amplifying the received audio signal,
- an output for outputting the amplified audio signal, the audio power amplifier controllable to assume an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, the audio power amplifier further comprising
- an input for receiving a control signal, and
- the audio power amplifier being adapted to assume the active state or the mute state in dependence on the received control signal.
2. An audio power amplifier according to claim 1 further adapted to assume the active state for a predetermined period of time after a control signal has been received, and to assume the mute state if no control signal has been received during the predetermined period of time.
3. An audio power amplifier according to claim 1 further adapted to assume the mute state if the control signal is received.
4. An audio power amplifier according to claim 1 further adapted to receive an analogue audio signal and to output an analogue amplified audio signal.
5. An audio power amplifier according to claim 1 further adapted to receive a digital audio signal and to output an analogue amplified audio signal.
6. A method of operating an audio power amplifier having - an input receiving an audio signal,
- an amplifier for amplifying the received audio signal,
- an output for outputting the amplified audio signal, the audio power amplifier capable of assuming an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, the audio power amplifier further having
- an input for receiving a control signal, and
- the audio power amplifier being adapted to assume the active state or the mute state in dependence on the control signal, the method comprising
- determining a desired state of the audio power amplifier selected from the active state and the mute state, and
- controlling, by means of the control signal, the audio power amplifier to assume the desired state.
7. An audio signal source comprising
- a source capable of providing an audio signal,
- an audio signal output connectable to an audio power amplifier and for outputting the audio signal to the audio power amplifier, the audio power amplifier capable of assuming an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output,
- means capable of determining a desired state of the audio power amplifier selected from the active state and the mute state, and of generating a control signal indicative of the desired state of the power amplifier,
- a control signal output connectable to the audio power amplifier and for outputting the control signal to the audio power amplifier.
8. A computer system comprising - a source capable of providing an audio signal,
- an audio signal output connectable to an audio power amplifier and for outputting the audio signal to the audio power amplifier, the audio power amplifier capable of assuming an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, - a processor capable of determining a desired state of the audio power amplifier selected from the active state and the mute state, and of generating a control signal indicative of the desired state of the power amplifier,
- a control signal output for outputting the control signal.
9. A computer system according to claim 8 wherein the desired state depends on an actual state of the computer system.
10. A computer system according to claim 8 further comprising an audio power amplifier having - an input connectable to the audio signal output for receiving the audio signal,
- an amplifier for amplifying the received audio signal,
- an output for outputting the amplified audio signal, the audio power amplifier controllable to assume an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output, the audio power amplifier further comprising - an input connectable to the control signal output for receiving a control signal, and
- the audio power amplifier being adapted to assume the active state or the mute state in dependence on the received control signal.
11. A computer program comprising instructions for a computer to - control a source to provide an audio signal, and to output the audio signal to an audio power amplifier capable of assuming an active state in which the amplified audio signal is fed to the output, and a mute state in which no amplified audio signal is fed to the output,
- determine a desired state of the audio power amplifier selected from the active state and the mute state, and to generate a control signal indicative of the desired state of the power amplifier.
12. A computer readable record carrier having stored thereon a program according to claim 11.
PCT/DK2007/050012 2006-02-03 2007-01-30 Audio amplifier with speaker protection against transients WO2007087812A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DKPA200600151 2006-02-03
DK200600151A DK200600151A (en) 2006-02-03 2006-02-03 Audio amplifier with speaker protection against transients

Publications (1)

Publication Number Publication Date
WO2007087812A1 true WO2007087812A1 (en) 2007-08-09

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PCT/DK2007/050012 WO2007087812A1 (en) 2006-02-03 2007-01-30 Audio amplifier with speaker protection against transients

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WO (1) WO2007087812A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110769353A (en) * 2018-12-04 2020-02-07 北京嘀嘀无限科技发展有限公司 Signal processing method, signal processing device, electronic equipment and storage medium

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5029005A (en) * 1990-04-25 1991-07-02 Rca Licensing Corporation Apparatus for the muting of an audio power amplifier in a standby mode
US5317470A (en) * 1991-05-06 1994-05-31 Thomson Consumer Electronics, Inc. Control system including a switching circuit for ensuring proper operation when operating power is removed from a portion of the control system
GB2307606A (en) * 1995-11-23 1997-05-28 Thomson Multimedia Sa Muting in a microprocessor-controlled audio apparatus
US5818948A (en) * 1996-10-23 1998-10-06 Advanced Micro Devices, Inc. Architecture for a universal serial bus-based PC speaker controller
US6041416A (en) * 1995-03-03 2000-03-21 Compaq Computer Corporation Circuit for reducing audio amplifier noise during powering on and off

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5029005A (en) * 1990-04-25 1991-07-02 Rca Licensing Corporation Apparatus for the muting of an audio power amplifier in a standby mode
US5317470A (en) * 1991-05-06 1994-05-31 Thomson Consumer Electronics, Inc. Control system including a switching circuit for ensuring proper operation when operating power is removed from a portion of the control system
US6041416A (en) * 1995-03-03 2000-03-21 Compaq Computer Corporation Circuit for reducing audio amplifier noise during powering on and off
GB2307606A (en) * 1995-11-23 1997-05-28 Thomson Multimedia Sa Muting in a microprocessor-controlled audio apparatus
US5818948A (en) * 1996-10-23 1998-10-06 Advanced Micro Devices, Inc. Architecture for a universal serial bus-based PC speaker controller

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110769353A (en) * 2018-12-04 2020-02-07 北京嘀嘀无限科技发展有限公司 Signal processing method, signal processing device, electronic equipment and storage medium

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Publication number Publication date
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