Audio Amplifier Gain Control Under Voltage Limiting
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Solution Overview
Problem
Existing audio signal amplification technologies experience changes in maximum output power due to variations in load impedance, leading to waveform deformation and increased power when the input signal's voltage amplitude increases, resulting in inefficiencies and potential excessive heat generation.
Innovation Solution
An amplifying device comprising a first amplifier, a voltage-limiting circuit, a second amplifier, a first controller to adjust the limit range based on load current, and a second controller to decrease the first amplifier's amplification factor when the voltage-limiting circuit is active, thereby controlling the limit range and maintaining a consistent waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage-limiting circuit limits the voltage of the output signal, then the voltage is controlled within a limit range, but the waveform of the output signal is deformed and the maximum output power increases
Solution Approach 1:
The patent applies preliminary action by detecting the input signal level before voltage limiting occurs and adjusting the amplification factor of the first amplifier in advance. When the input signal level is detected to be high, the amplification factor is reduced before the voltage-limiting circuit clips the waveform, thereby preventing waveform deformation and avoiding the increase in maximum output power that would otherwise occur due to square-wave-like distortion.
2Power
If the amplification factor of the first amplifier is increased, then the output signal amplitude increases, but the waveform deformation increases when voltage limiting is active
Solution Approach 1:
The patent implements feedback by continuously detecting the input signal level and using this information to dynamically adjust the amplification factor of the first amplifier. The detection unit monitors the input signal, and when high signal levels are detected that would cause waveform clipping, the control unit reduces the amplification factor accordingly. This closed-loop feedback mechanism ensures that the output signal maintains adequate amplitude while preventing waveform deformation during voltage limiting.
Data Source
AI summary
An amplifying device includes a first amplifier, a voltage-limiting circuit, a second amplifier, a first controller, and a second controller. The first amplifier is configured to amplify an input signal. The voltage-limiting circuit is configured to limit a voltage of an output signal from the first amplifier to within a limit range. The second amplifier is configured to amplify an output signal from the voltage-limiting circuit. The first controller is configured to control the limit range in accordance with a current supplied to a load from the second amplifier. The second controller is configured to decrease an amplification factor of the first amplifier in a state in which the voltage-limiting circuit limits the voltage of the output signal from the first amplifier.