Self-Oscillating Class D Amplifier Feedback for Low Distortion
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Solution Overview
Problem
Modern Class D amplifiers face challenges in maintaining high audio quality under real-world dynamic conditions and with reactive loads, particularly in balancing efficiency, distortion suppression, and control loop stability.
Innovation Solution
A self-oscillating Class D amplifier device with a multi-loop feedback system, including a first feedback path for oscillation frequency control, a second feedback path for low-frequency distortion reduction, and a third feedback path for enhanced selectivity and additional gain, utilizing a combination of passive networks and transimpedance amplifiers to correct distortion components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a self-oscillating Class D power amplifier stage is used to achieve high efficiency, then energy efficiency is improved, but distortion suppression and control loop stability deteriorate
Solution Approach 1:
The patent divides the feedback system into three distinct feedback paths: a first feedback path for oscillation frequency control, a second feedback path for low-frequency distortion reduction, and a third feedback path for enhanced selectivity and additional gain. This segmentation allows each feedback path to be optimized for its specific function, enabling the amplifier to maintain high efficiency while suppressing distortion and ensuring control loop stability.
Solution Approach 2:
The patent implements a multi-loop feedback system where output signals are fed back through different paths with specific transfer functions. The first feedback path provides oscillation frequency control, the second feedback path corrects low-frequency distortion, and the third feedback path adds selective gain enhancement. This comprehensive feedback mechanism allows the amplifier to maintain efficiency while correcting distortion and ensuring stability.
2Manufacturing precision
If multiple feedback paths are added to reduce distortion and enhance stability, then audio quality is improved, but device complexity increases
Solution Approach 1:
The patent designs the feedback network to perform multiple functions through a unified structure. The same feedback network with transfer functions H2 and H3 simultaneously provides oscillation frequency control, low-frequency distortion reduction, and selective gain enhancement. This multi-functionality approach improves audio quality while minimizing the increase in device complexity by avoiding completely separate circuits for each function.
Data Source
AI summary
The present disclosure relates to an amplifier device for amplifying an input signal Sx at a device input X to an output signal Sy at a device output Y, for driving a loudspeaker or comparable reactive load, comprises a self-oscillating Class D power amplifier stage with transfer function KA(s). The amplifier stage includes a comparator, a power stage, and a second-order low-pass output filter comprising an inductor and a capacitor. A time delay unit provides a delay determined by one or more of the comparator, the power stage, and a first feedback filter. The output signal Sy is fed back to the comparator via the first feedback path to establish oscillation and provide basic low-frequency feedback. A correction stage is provided, comprising a second feedback path that feeds the output signal Sy, via a scaling resistor, to a virtual ground input of a transimpedance amplifier.