Amplifiers
First Claim
1. An amplifier circuit for amplifying an audio signal, comprising:
- a voltage regulator having an input node for receiving an input voltage and an output node for outputting an output voltage, the voltage regulator comprising an output capacitor coupled to the output node;
an amplifier connected to receive the output voltage from said output node of the voltage regulator as a supply voltage;
the voltage regulator being operable in a voltage-control mode to maintain the output voltage at a nominal output voltage and in current-control mode to apply current limiting so as to limit an input current drawn by the voltage regulator via the input node so as not to exceed a defined input current limit; and
a controller for defining the nominal output voltage;
wherein the controller is operable in a first mode to define the nominal output voltage so as not to exceed a first voltage magnitude and is operable in a second mode to define the nominal output voltage to be equal to a second voltage magnitude, the second voltage magnitude being greater than the first voltage magnitude;
wherein the controller is configured to monitor an indication of the level of the audio signal for a high-amplitude part of the audio signal that could result in the voltage regulator operating in the current-control mode to apply current limiting; and
wherein the controller is configured to operate in said first mode until such a high-amplitude part of the audio signal is detected and, on such detection to operate in the second mode of operation until such a high-amplitude part of the audio signal has been amplified;
wherein the second voltage magnitude is greater than required for voltage headroom for amplifying the high-amplitude part of the audio signal so as to allow for a voltage droop of the output voltage over a plurality of switching cycles of the voltage regulator when operating in the current-control mode.
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Accused Products
Abstract
This application relates to amplifier circuits for amplifying an audio signal. An amplifier circuit (100) has a voltage regulator (201) for outputting a supply voltage to an amplifier (104). An output capacitor (103) coupled to an output node of the voltage regulator. The voltage regulator is operable in a voltage-control mode to maintain the output voltage (VS) at a nominal output voltage and in current-control mode to limit the input current drawn to exceed a defined limit. A controller (301) is operable in a first mode to define the nominal output voltage so as not to exceed a first voltage magnitude and in a second mode to define the nominal output voltage to be equal to a second, higher, voltage magnitude. The controller (301) monitors the audio signal for a high-amplitude part of the audio signal, that could result in the voltage regulator operating in the current-control mode to apply current limiting and, on such detection swaps from the first to the second mode until such a high-amplitude part of the audio signal has been amplified. The second voltage magnitude is greater than required for voltage headroom for amplifying the high-amplitude part of the audio signal so as to allow for a voltage droop of the output voltage over a plurality of switching cycles of the voltage regulator when operating in the current-control mode.
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Citations
20 Claims
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1. An amplifier circuit for amplifying an audio signal, comprising:
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a voltage regulator having an input node for receiving an input voltage and an output node for outputting an output voltage, the voltage regulator comprising an output capacitor coupled to the output node; an amplifier connected to receive the output voltage from said output node of the voltage regulator as a supply voltage; the voltage regulator being operable in a voltage-control mode to maintain the output voltage at a nominal output voltage and in current-control mode to apply current limiting so as to limit an input current drawn by the voltage regulator via the input node so as not to exceed a defined input current limit; and a controller for defining the nominal output voltage; wherein the controller is operable in a first mode to define the nominal output voltage so as not to exceed a first voltage magnitude and is operable in a second mode to define the nominal output voltage to be equal to a second voltage magnitude, the second voltage magnitude being greater than the first voltage magnitude; wherein the controller is configured to monitor an indication of the level of the audio signal for a high-amplitude part of the audio signal that could result in the voltage regulator operating in the current-control mode to apply current limiting; and wherein the controller is configured to operate in said first mode until such a high-amplitude part of the audio signal is detected and, on such detection to operate in the second mode of operation until such a high-amplitude part of the audio signal has been amplified; wherein the second voltage magnitude is greater than required for voltage headroom for amplifying the high-amplitude part of the audio signal so as to allow for a voltage droop of the output voltage over a plurality of switching cycles of the voltage regulator when operating in the current-control mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An amplifier circuit for amplifying an audio signal, comprising:
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an amplifier; a voltage regulator having an input node for receiving an input voltage and an output node for outputting a supply voltage to said amplifier, the voltage regulator comprising an output capacitor coupled to the output node; the voltage regulator comprising a voltage control loop for controlling the voltage at the output node to a nominal output voltage and a current control loop for, when activated, limiting an input current drawn by the voltage regulator via the input node so as not to exceed a defined input current limit, wherein the voltage regulator operates according to the voltage control loop unless the current control loop is activated; and a controller for defining the nominal output voltage; wherein the controller is operable in a first mode to define the nominal output voltage so as not to exceed a first voltage magnitude and is operable in a second mode to define the nominal output voltage to be equal to a second voltage magnitude, the second voltage magnitude being greater than the first voltage magnitude; wherein the controller is configured to monitor an indication of the level of the audio signal for a high-amplitude part of the audio signal that could result in the current control loop of the voltage regulator being activated; and wherein the controller is configured to operate in said first mode until such a high-amplitude part of the audio signal is detected and, on such detection to operate in the second mode of operation until such a high-amplitude part of the audio signal has been amplified; wherein the second voltage magnitude is greater than required for voltage headroom for amplifying the high-amplitude part of the audio signal so as to allow for a voltage droop of the supply voltage over a plurality of switching cycles of the current control loop dominating the voltage control loop.
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20. An amplifier circuit for amplifying an audio signal, comprising:
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an amplifier; a voltage regulator having an input node for receiving an input voltage and an output node for outputting a supply voltage to said amplifier, the voltage regulator comprising an output capacitor coupled to the output node; the voltage regulator being operable to apply current limiting so as to limit an input current drawn by the voltage regulator via the input node so as not to exceed a defined input current limit; a controller for defining a nominal output voltage generated by the voltage regulator; wherein the controller is operable to compare an indication of the level of the audio signal to a first threshold, wherein the first threshold is indicative of the input signal that, if amplified by the amplifier, would be expected to lead to the voltage regulator experiencing current limiting; and in the event that the indication of the level of the audio signal exceeds said first threshold to increase the magnitude of the nominal output voltage of the voltage regulator from a first operating range to a second higher voltage level.
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Specification