Class D Amplifier Feedback for PWM Peak Imbalance Noise
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Solution Overview
Problem
Class D amplifiers that change the peak value of PWM signals often produce unintended sounds, such as clicking noise or pop noise, due to imbalances between positive and negative peak values.
Innovation Solution
Incorporating a feedback circuit that compares and adjusts the positive and negative amplitudes of the PWM signal, generated by separate amplitude generating circuits, to minimize the difference and prevent unwanted sound output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the peak value of PWM signal is changed to control output level, then noise level can be reduced, but imbalance between positive and negative peak values causes clicking noise or pop noise
Solution Approach 1:
The patent employs a feedback circuit that detects the output signal and feeds it back to the amplitude generating circuits. This feedback mechanism continuously monitors the actual output and adjusts the positive and negative peak values to maintain balance, thereby preventing clicking noise and pop noise while allowing dynamic peak value adjustment for noise control
Solution Approach 2:
The patent introduces separate positive-side and negative-side amplitude generating circuits with independent control capabilities. This asymmetric structure allows differential adjustment of positive and negative peak values to compensate for imbalances, preventing the generation of unwanted sounds while maintaining the ability to reduce overall noise levels
2Reliability
If separate positive and negative amplitude generating circuits are used, then imbalance can be corrected, but device complexity increases
Solution Approach 1:
The feedback circuit serves multiple functions simultaneously: it monitors the output signal, detects imbalances between positive and negative peaks, generates correction signals, and adjusts both amplitude generating circuits. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while maintaining high reliability
Data Source
AI summary
The present technology relates to an amplifier, an audio signal output method, and an electronic device that can inhibit unintended sound output in a class D amplifier that changes a peak value of a PWM signal. The amplifier includes: a positive-side amplitude generating circuit configured to generate positive-side amplitude of an output PWM signal that is a PWM signal to be output outside an apparatus; a negative-side amplitude generating circuit configured to generate negative-side amplitude of the output PWM signal; and a feedback circuit configured to feed back a difference between the amplitude generated by the positive-side amplitude generating circuit and the amplitude generated by the negative-side amplitude generating circuit to the positive-side amplitude generating circuit and the negative-side amplitude generating circuit. The present technology is applicable, for example, to an amplifier or the like of an electronic device such as an audio player.