US 9,559,648 B2Granted

Amplifier with reduced idle power loss using single-ended loops

AssigneeTexas Instruments Incorporated

InventorLawrence Christopher Cotton

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Abstract

A method of audio signal processing includes receiving a first audio input signal (first input signal) at an input of a first integrating amplifier of a first single-ended (SE) closed loop channel, and second input signal with a polarity reversed relative to the first input signal at an input of a second integrating amplifier configured of a second SE closed loop channel. During audio signal processing a common-mode (CM) reference voltage level applied to a current source coupled to an input of the first and second integrating amplifiers is dynamically changed including whenever a level of the input signals is below a predetermined low level, reducing the CM reference voltage level for implementing low duty cycle (LDC) PWM operation, and whenever the level is above a level that corresponds to an onset of clipping, increasing the CM reference voltage level for at least reducing the clipping to lower crossover distortion.

Claims15

Dependent claims

A method of audio signal processing, comprising:

a first single ended (SE) closed loop channel receiving a first audio input signal (first input signal) at an inverting or non-inverting input of a first amplifier, said first amplifier configured as an integrating amplifier that is coupled in sequence to a first comparator, a first pulse width modulation (PWM) logic and pulse inject block, gate driver block, and output stage, wherein a first signal output of said first output stage is fed back to said inverting input of said first amplifier, and
a second SE closed loop channel receiving a second audio input signal (second input signal) with a polarity reversed relative to said first input signal at an inverting or non-inverting input of at least a second amplifier, said second amplifier configured as an integrating amplifier that is coupled in sequence with a second comparator, a second PWM logic and pulse inject block, gate driver block, and output stage, wherein a second signal output of said second output stage is fed back to said inverting input of said second amplifier;
during said audio signal processing dynamically changing a common-mode (CM) reference voltage level applied to a first current source which is coupled to pull current from said inverting or non-inverting input of said first amplifier and a second current source which is coupled to pull current from said inverting or non-inverting input of said second amplifier including:
wherein whenever a level of said first or second input signal is below a predetermined low level, reducing said CM reference voltage level for implementing low duty cycle (LDC) PWM operation, and
wherein whenever said level is above a level that corresponds to an onset of clipping, increasing said CM reference voltage level for at least reducing said clipping to lower crossover distortion.

2 more elements

A power amplifier, comprising:

a first single ended (SE) closed loop channel receiving a first audio input signal (first input signal) at an inverting or non-inverting input of a first amplifier, said first amplifier configured as an integrating amplifier coupled in sequence to a first comparator, a first pulse width modulation (PWM) logic and pulse inject block, gate driver block, and output stage, wherein a first signal output of said first output stage is fed back to said inverting input of said first amplifier;
a second SE closed loop channel receiving a second audio input signal (second input signal) with a polarity reversed relative to said first input signal at an inverting or non-inverting input of at least a second amplifier, said second amplifier configured as an integrating amplifier that is coupled in sequence with a second comparator, a second PWM logic and pulse inject block, gate driver block, and output stage, wherein a second signal output of said second output stage is fed back to said inverting input of said second amplifier;
a common-mode control (CMC) block having an input coupled to receive an output from said first PWM logic and pulse inject block;
a startup and shutdown control (SSC) block having an input coupled to an output of said CMC block, wherein an output of said SSC block is coupled to dynamically modulate a common mode (CM) reference voltage level applied to a first current source which is coupled to pull current from said inverting or non-inverting input of said first amplifier and a second current source which is coupled to pull current from said inverting or non-inverting input of said second amplifier during audio signal processing, including:
wherein whenever a level of said first or second input signal is below a predetermined low level, reducing said CM reference voltage level for implementing low duty cycle (LDC) PWM operation, and
wherein whenever said level is above a level that corresponds to an onset of clipping, increasing said CM reference voltage level for at least reducing said clipping to lower crossover distortion.

3 more elements

A power amplifier, comprising:

a first single ended (SE) closed loop channel receiving a first audio input signal (first input signal) at an inverting or non-inverting input of a first amplifier, said first amplifier configured as an integrating amplifier coupled in sequence to a first comparator, a first pulse width modulation (PWM) logic and pulse inject block, gate driver block, and output stage, wherein a first signal output of said first output stage is fed back to said inverting input of said first amplifier;
a second SE closed loop channel receiving a second audio input signal (second input signal) with a polarity reversed relative to said first input signal at an inverting or non-inverting input of at least a second amplifier, said second amplifier configured as an integrating amplifier that is coupled in sequence with a second comparator, a second PWM logic and pulse inject block, gate driver block, and output stage, wherein a second signal output of said second output stage is fed back to said inverting input of said second amplifier;
a common-mode control (CMC) block having an input coupled to receive an output from said first PWM logic and pulse inject block;
a startup and shutdown control (SSC) block having an input coupled to an output of said CMC block, wherein an output of said SSC block is coupled to dynamically modulate a common-mode (CM) reference voltage level applied to a first current source which is coupled to pull current from said inverting input of said first amplifier and a second current source which is coupled to pull current from said inverting input of said second amplifier during audio signal processing, including:
wherein whenever a level of said first or second input signal is below a predetermined low level, reducing said CM reference voltage level for implementing low duty cycle (LDC) PWM operation;
wherein whenever said level is above a level that corresponds to an onset of clipping, increasing said CM reference voltage level for at least reducing said clipping to lower crossover distortion, and
a substrate having a semiconductor surface, wherein said power amplifier is formed on said semiconductor surface.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/573,556Filed 17 Dec 2014 · us provisional application
Priority: 6 Feb 2014
Published: US 2015/0222237 A16 Aug 2015
Granted: 31 Jan 2017
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

H03F 3/45479
With semiconductor devices only: characterised by the way of common mode signal rejection
H03F 3/183
Low-frequency amplifiers, e.g. audio preamplifiers: with semiconductor devices only
H03F 3/2173
Class D power amplifiers; Switching amplifiers: of the bridge type
H03F 3/45475
Characterised by the way of implementation of the active amplifying circuit in the differential amplifier: using IC blocks as the active…