Predictive Supply Switching in Audio Amplifiers to Avoid Pops

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Solution Overview

Problem

Audio artifacts such as 'pops' and 'clicks' are audible in audio devices using Class G, Class DG, and Class H amplifiers when modifying output voltage, unless measures are taken to reduce or eliminate these artifacts.

Innovation Solution

An audio amplifier circuit with a power amplifier and control circuit that predicts, based on signal characteristics, when to change the power supply voltage at an approximate zero crossing of the signal, thereby minimizing audible artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the power supply voltage is modified in Class G, Class DG, and Class H amplifiers to improve power efficiency, then power efficiency is improved, but audible audio artifacts (pops and clicks) are generated

Engineering Contradiction:

Improvepower efficiencyVSAvoidaudible audio artifacts

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The control circuit predicts future signal characteristics and preemptively switches the power supply voltage at approximate zero crossings before the actual signal level change occurs. This preliminary action ensures the voltage switch happens at the optimal moment (zero crossing) to minimize audible artifacts while maintaining power efficiency benefits.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors the output signal characteristics and uses this feedback to predict when voltage switching should occur. The control circuit adjusts the power supply voltage based on real-time signal analysis, creating a closed-loop system that optimizes both power efficiency and audio quality.

Inventive Principle:

Principle #23Feedback

2Use of energy by moving object

If the power supply voltage is switched immediately when signal level changes occur, then power efficiency is optimized, but audio artifacts become audible

Engineering Contradiction:

Improvepower efficiencyVSAvoidaudio quality

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

Instead of switching voltage immediately at signal level changes, the control circuit predicts upcoming signal characteristics and switches the power supply voltage in advance at approximate zero crossings. This preliminary switching action occurs before the actual signal change, ensuring optimal timing that prevents audible artifacts while maintaining power efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system prepares for potential signal level changes by monitoring signal characteristics and predicting when voltage switching will be needed. By switching at zero crossings before the actual signal change occurs, the system cushions against the potential generation of audible artifacts, ensuring smooth transitions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Use of energy by moving object

If the power supply voltage is switched at arbitrary points, then power efficiency improvements are achieved, but audible pops and clicks are generated

Engineering Contradiction:

Improvepower efficiencyVSAvoidaudio output quality

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The control circuit predicts signal characteristics and switches the power supply voltage at approximate zero crossings before the actual signal level change occurs. This preliminary action ensures voltage switching happens at the most favorable moment (zero crossing) to eliminate audible artifacts while maintaining power efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the timing parameter of voltage switching from immediate response to predictive timing based on signal characteristics. By changing when the voltage switch occurs (at zero crossings rather than at signal level changes), the system maintains power efficiency while ensuring reliable audio output quality.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10128803B2Systems and methods for predictive switching in audio amplifiers

Publication Date: 2018.11.13 CIRRUS LOGIC INC

AI summary

An audio amplifier circuit for providing an output signal to an audio transducer may include a power amplifier and a control circuit. The power amplifier may include an audio input for receiving an audio input signal, an audio output for generating the output signal based on the audio input signal, and a power supply input for receiving a power supply voltage, wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage. The control circuit may be configured to predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage, and responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage.