Class-D Power Amplifier Error Correction via Noise Shaping
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Solution Overview
Problem
Class-D power amplifiers suffer from output signal quality deterioration due to noise and imperfections in the switching power stage, leading to waveform offset issues.
Innovation Solution
A power amplifier system comprising a subtracting unit, noise shaping module, pulse adjustment unit, and power stage that generates an error signal, performs noise shaping, and adjusts the output signal using a control signal to correct errors, improving signal fidelity by shifting noise to higher frequencies and calibrating pulse widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a class-D power amplifier uses a switching power stage to achieve high efficiency, then energy efficiency is improved, but output signal quality deteriorates due to noise and waveform offset
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is fed back to the input side through a feedback resistor. A subtracting unit compares the feedback signal with the input signal to generate an error signal, which is then used to adjust the PWM duty cycle and correct output deviations, thereby maintaining signal quality while preserving high efficiency
Solution Approach 2:
The patent introduces a feedback resistor as an intermediary element that transfers a portion of the output signal back to the input side. This intermediary enables the system to monitor and self-correct output signal quality without directly interfering with the high-efficiency switching operation
2Device complexity
If the power amplifier uses a conventional design without error correction, then device complexity is reduced, but waveform offset and signal fidelity deteriorate
Solution Approach 1:
The subtracting unit continuously compares the feedback signal with the input signal and generates an error signal that represents the deviation. This error signal is added to the original input signal to adjust the PWM duty cycle, automatically correcting waveform offset and improving signal fidelity
Solution Approach 2:
The system performs preliminary error detection and correction by comparing signals and generating correction signals before the distorted output is produced. The pulse adjustment unit proactively adjusts the PWM duty cycle based on predicted errors, preventing waveform offset before it occurs
3Reliability
If noise shaping is applied to correct low-frequency noise, then audio frequency signal quality is improved, but high-frequency noise components increase
Solution Approach 1:
The noise shaping module intentionally shapes the noise spectrum by using a feedback loop that emphasizes high-frequency noise components while suppressing low-frequency noise. This converts the harmful low-frequency noise that affects audio quality into less perceptible high-frequency noise, effectively improving audio frequency signal quality
Solution Approach 2:
The noise shaping module changes the spectral distribution parameter of the noise by using integrators and feedback paths that transfer noise energy from low-frequency bands to high-frequency bands, thereby improving audio frequency performance while concentrating noise in less critical high-frequency regions
Data Source
AI summary
An amplifier includes a subtracting unit for generating an error signal according to an input signal and an output signal; a noise shaping unit for executing a noise shaping operation on the error signal to produce a noise-shaped signal; a pulse adjustment unit for generating a control signal according to the noise-shaped signal and the input signal; and a power stage for generating the output signal according to the control signal.