Audio Amplifier Feedback Circuit for Dynamic Speaker Impedance
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Solution Overview
Problem
Conventional audio amplifiers face issues with output power distortion and quality due to varying impedance of loudspeakers, leading to insufficient power bearing capacity and playback distortion, especially in the audio range of 20 Hz to 20 KHz.
Innovation Solution
An audio amplifier structure with dynamic impedance adjustment, comprising a power amplifying unit, current sensing unit, and subtraction unit, which senses output current, converts it into a control voltage signal matched with loudspeaker impedance, and feeds back the difference between audio and control voltage signals to adjust output power and reduce impedance fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional power amplifier is used with fixed closed loop gain, then the amplifier structure is simple, but the output power varies with loudspeaker impedance causing distortion and poor output quality
Solution Approach 1:
The patent introduces a feedback mechanism where the output current is sensed and converted to a control voltage signal that is subtracted from the input audio voltage. This feedback loop dynamically adjusts the amplifier output to compensate for impedance variations, resolving the contradiction between simple structure and high output quality by adding only essential feedback components rather than completely redesigning the amplifier architecture
Solution Approach 2:
The patent dynamically changes the effective gain parameter of the amplifier by subtracting a control voltage (derived from output current) from the input voltage. This parameter adjustment compensates for impedance variations without requiring multiple fixed-gain amplifier stages, thus improving output quality while maintaining relatively simple structure
2Reliability
If high-quality loudspeaker is used, then the natural uneven impedance is inherent, but the playback music distortion still occurs due to impedance variation
Solution Approach 1:
The patent converts the harmful effect of impedance variation into a useful signal by sensing the output current (which reflects impedance changes) and using it to generate a control voltage that compensates for the distortion. The very current that indicates the problem becomes the key to solving it, allowing the amplifier to adapt to the loudspeaker's natural impedance characteristics
Solution Approach 2:
The amplifier system performs self-adjustment by automatically sensing its own output current and using that information to modify its input signal. This self-service mechanism allows the system to compensate for impedance variations without external intervention, maintaining reliable operation and extending service life
3Power
If no feedback control is implemented, then the amplifier operation is simple, but the maximum power bearing capacity is insufficient and amplifier damage may occur
Solution Approach 1:
The patent implements a feedback control circuit that senses output current and adjusts the input signal accordingly, enabling the amplifier to operate safely at higher power levels by preventing overload conditions. The feedback mechanism provides real-time monitoring and adjustment, allowing the system to utilize maximum power bearing capacity without risking damage
Data Source
AI summary
The present invention generally relates to a structure and method of audio amplifier by dynamic impedance adjustment, including a power amplifying unit, a loud-speaker, a current sensing unit and a subtraction unit. The power amplifying unit has a fixed closed loop gain, with an input side and an output side; the loud-speaker is electrically connected to the output side of the power amplifying unit; the current sensing unit senses the output current of the power amplifying unit, and the sensed output current is converted into a current control voltage signal; the subtraction unit inputs the audio voltage signal and the feedback current control voltage signal, and outputs the difference of the audio voltage signal minus the current control voltage signal, and inputs it to the input side of the power amplifying unit. The output sound quality of the loud-speaker is improved by dynamic impedance adjustment.