Self-Oscillating Class D Amplifier With Dual Feedback for Low-Frequency Audio
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Solution Overview
Problem
Conventional self-oscillating class D amplifiers face limitations in improving distortion characteristics and frequency characteristics, particularly in the low-frequency audio band, due to insufficient negative feedback.
Innovation Solution
Incorporating a transformer conductance amplifier (TCA) and a second feedback circuit that applies differential feedback to enhance the negative feedback amount, allowing for improved distortion and frequency characteristics by adjusting the feedback loop dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional feedback circuits are used in self-oscillating class D amplifiers, then the basic amplification function is achieved, but distortion characteristics and frequency characteristics in the low-frequency audio band are insufficient
Solution Approach 1:
The patent implements a dual feedback circuit architecture where the first feedback circuit connects the output to the inverting input terminal of the comparator, and the second feedback circuit connects the output to the inverting input terminal of the integrator. This dual feedback structure increases the negative feedback amount in the low-frequency audio band, thereby improving distortion characteristics and frequency characteristics without requiring fundamentally new circuit topologies
Solution Approach 2:
The feedback system is segmented into two independent feedback circuits with distinct functions: the first feedback circuit handles high-frequency carrier components through the comparator, while the second feedback circuit handles low-frequency audio signals through the integrator. This segmentation allows each feedback path to be optimized for its specific frequency range, improving overall audio band characteristics
2Reliability
If negative feedback amount is increased to improve distortion characteristics, then frequency characteristics improve, but the feedback circuit becomes more complex
Solution Approach 1:
The dual feedback circuit architecture serves multiple functions simultaneously: it provides negative feedback for distortion reduction, maintains frequency characteristics across the audio band, and enables self-oscillation control. By making the feedback system multi-functional, the patent achieves improved reliability without proportionally increasing complexity
Data Source
AI summary
A class D amplifier includes a self-oscillating class D amplification circuit that is driven by an output current signal; and a voltage-current converting circuit that outputs an output current signal in response to an input signal voltage and an output signal voltage from a feedback signal voltage.