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
  • 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.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Multimedia (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37891935

Family Applications (1)

Country Status (2)

Cited By (1)

Citations (5)

• 2006
  • 2006-02-03 DK DK200600151A patent/DK200600151A/da not_active Application Discontinuation
• 2007
  • 2007-01-30 WO PCT/DK2007/050012 patent/WO2007087812A1/en active Application Filing

Patent Citations (5)

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