Shared-Feedback Audio Amplifier for Click and Pop Reduction
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Solution Overview
Problem
Audio power amplifiers in multimedia devices often produce unwanted 'click and pop' sounds when headphones are connected or disconnected, due to voltage transitions and offset mismatches between main and auxiliary amplifier paths, which degrade the user experience.
Innovation Solution
A power amplifier design featuring a first amplifier and an auxiliary amplifier with a shared feedback loop, where the output is ramped from ground to an offset voltage to minimize these sounds, using switches and resistors to reduce resistor mismatch and attenuate transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an auxiliary amplifier is used to reduce voltage transition, then click and pop sounds are reduced, but offset mismatch between main path and auxiliary path resistors causes large DC offsets and audible clicks
Solution Approach 1:
The patent implements a feedback mechanism where the output of the auxiliary amplifier is fed back to its input through a feedback resistor. This feedback loop automatically adjusts the auxiliary amplifier's output to match the main amplifier's output voltage, eliminating offset mismatches and preventing audible clicks during switching transitions.
Solution Approach 2:
The auxiliary amplifier serves as an intermediary device between the ground and the main amplifier output. It provides a controlled voltage transition path that ramps the output voltage gradually during power-up and power-down, preventing direct ground-to-output transitions that cause clicks and pops.
2Adaptability or versatility
If switches are used to switch between main and auxiliary amplifier paths, then the amplifier can operate in different modes, but switching between paths with different DC offsets produces audible click sounds
Solution Approach 1:
Before switching from the auxiliary amplifier path to the main amplifier path, the auxiliary amplifier's output is ramped to match the main amplifier's output voltage level. This preliminary voltage matching ensures that when the switch transitions between paths, there is no sudden voltage change or offset mismatch, thereby preventing audible click sounds.
Solution Approach 2:
The patent dynamically changes the DC offset parameter of the auxiliary amplifier's output voltage to match the main amplifier's output voltage. By adjusting this voltage parameter in real-time before switching, the system eliminates the conditions that would otherwise produce audible clicks during path transitions.
3Speed
If the power amplifier output transitions directly from ground to offset voltage, then the amplifier responds quickly to power changes, but audible popping sounds are generated
Solution Approach 1:
The auxiliary amplifier generates a periodic ramp waveform that gradually transitions the output voltage from ground to the offset voltage level during power-up, and vice versa during power-down. This periodic ramping action replaces the direct instantaneous transition, eliminating the sudden voltage change that causes popping sounds while maintaining acceptable response speed.
Solution Approach 2:
Before the main amplifier output transitions to the offset voltage, the auxiliary amplifier preliminarily ramps the output voltage to the target level. This preliminary voltage establishment prevents the direct ground-to-offset transition, thereby eliminating audible pops while maintaining quick response through controlled voltage ramping.
Data Source
AI summary
A power amplifier provides reduction of click and pop in audio applications. The power amplifier includes a first amplifier and an auxiliary amplifier. The auxiliary amplifier is used to ramp the power amplifier output from ground to an offset voltage to reduce the “click and pop” sound. The first amplifier and the auxiliary amplifier having a shared feedback loop. An output of the first amplifier and an output of the auxiliary amplifier may be switchably coupled to the shared feedback loop. A wave generator controls a switch to couple the first amplifier output or the auxiliary amplifier output to the shared feedback loop.