METHOD AND APPARATUS FOR CONTROLLING A SELECTABLE VOLTAGE AUDIO POWER OUTPUT STAGE
First Claim
1. An audio amplifier circuit for providing an output signal to an audio transducer, said audio amplifier circuit comprising:
- a power amplifier having an audio input for receiving an audio input signal, an audio output for providing said output signal, and a pair of power supply rail connections;
a power supply for providing a power supply voltage across said pair of power supply rail connections of said power amplifier, wherein said power supply has a selectable power supply voltage level, whereby power consumption of said power amplifier is reduced when said magnitude of said audio signal is reduced; and
a control circuit for controlling said level of said audio signal and said selectable power supply voltage level in conformity with said indication of magnitude, so that clipping is prevented when said selectable power supply voltage level is increased and has not yet reached a full power supply voltage level.
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Accused Products
Abstract
A method and apparatus for controlling a selectable voltage audio power output stage provides a mechanism for raising the selected power amplifier output voltage in time for the arrival of signal peaks to avoid clipping. Signal peaks may either be delayed by delaying an increase in volume control level or enabling signal compression for a predetermined time period, so that sufficient time is provided for the amplifier power supply to stabilize at a higher operating voltage when an increase of power supply voltage is selected. Alternatively, a signal level may be determined at an upstream source, such as a decoder or filter that provides information in sufficient advance of the arrival of the peaks, and used to control the power supply selection, so that the higher power supply voltage level is selected in advance of arrival of the signal peaks that would otherwise cause clipping at the power amplifier output.
261 Citations
24 Claims
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1. An audio amplifier circuit for providing an output signal to an audio transducer, said audio amplifier circuit comprising:
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a power amplifier having an audio input for receiving an audio input signal, an audio output for providing said output signal, and a pair of power supply rail connections; a power supply for providing a power supply voltage across said pair of power supply rail connections of said power amplifier, wherein said power supply has a selectable power supply voltage level, whereby power consumption of said power amplifier is reduced when said magnitude of said audio signal is reduced; and a control circuit for controlling said level of said audio signal and said selectable power supply voltage level in conformity with said indication of magnitude, so that clipping is prevented when said selectable power supply voltage level is increased and has not yet reached a full power supply voltage level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of improving efficiency of an amplifier for providing a power output to an audio transducer, said method comprising:
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receiving an indication of a magnitude of a signal to be amplified by said amplifier; supplying a power supply voltage to said amplifier from a power supply having a selectable power supply voltage level; and controlling a level of said signal and selecting said power supply voltage level in conformity with said indication of magnitude. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An audio circuit for providing an output signal to an audio transducer, said audio amplifier circuit comprising:
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a signal processing circuit for providing a source audio signal and an early indication of magnitude of said source audio signal; a power amplifier having an audio input for receiving said source audio input signal, an audio output for providing said output signal, and a pair of power supply rail connections; a power supply for providing a power supply voltage across said pair of power supply rail connections of said power amplifier, wherein said power supply has a selectable power supply voltage level, whereby power consumption of said power amplifier is reduced when said magnitude of said audio signal is reduced; and a control circuit for controlling said selectable power supply voltage level in conformity with said early indication of magnitude, wherein said early indication of magnitude provides indications of peaks in said source audio signal so that clipping is prevented when said selectable power supply voltage level is increased and has not yet reached a full power supply voltage level. - View Dependent Claims (18, 19, 20)
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21. A method of improving efficiency of an amplifier for providing a power output to an audio transducer, said method comprising:
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receiving an early indication of a magnitude of a signal to be amplified by said amplifier; supplying a power supply voltage to said amplifier from a power supply having a selectable power supply voltage level; and selecting said power supply voltage level in conformity with said early indication of magnitude, so that a selected increase in power supply voltage level will have stabilized in advance of arrival of peaks in said signal at said amplifier. - View Dependent Claims (22, 23, 24)
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Specification