Audio Amplifier Supply Voltage Tracking for Low Distortion
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Solution Overview
Problem
Conventional amplifying devices face issues with distortion of output signals due to rapid changes in input signals when fixed headroom is underestimated, and degradation of power efficiency when it is overestimated, while voltage variable power supplies struggle to respond to load fluctuations, leading to distorted output signals.
Innovation Solution
An amplifying device with a signal delay processor, a voltage variable power supply, and a supply voltage controller that calculates the envelope of the input audio signal to generate a supply voltage control signal, allowing the supply voltage to follow the input signal waveform without considering fixed headroom, and adjusts the read-ahead width to handle slew rate fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed headroom is added to the supply voltage control to prevent distortion during rapid signal changes, then the output signal distortion is reduced, but the power efficiency of the power supply deteriorates
Solution Approach 1:
The patent applies dynamics by making the supply voltage control signal adaptive rather than fixed. The envelope follower dynamically adjusts the supply voltage based on the actual input signal characteristics, allowing the system to optimize between distortion prevention and power efficiency in real-time based on signal conditions
Solution Approach 2:
The patent changes the parameter of supply voltage dynamically by using an envelope follower to generate a time-varying control signal. This allows the supply voltage to be adjusted according to the instantaneous envelope of the input signal, resolving the contradiction between maintaining fixed headroom for distortion prevention and reducing power consumption
2Loss of energy
If the slew rate of the voltage variable power supply is decreased to improve power efficiency, then the power consumption is reduced, but the voltage variable power supply cannot respond to rapid changes in the supply voltage signal, causing output signal distortion
Solution Approach 1:
The patent applies preliminary action by having the envelope follower predict and prepare the supply voltage control signal in advance. By following the envelope of the input signal, the control signal is prepared beforehand to match the upcoming signal requirements, allowing the power supply to respond accurately without requiring high slew rate
Solution Approach 2:
The patent uses feedback by continuously monitoring the input signal envelope and adjusting the supply voltage control signal accordingly. The envelope follower provides real-time feedback about signal characteristics, enabling the power supply to maintain optimal performance without excessive power consumption
Data Source
AI summary
A supply voltage controller 11 includes a simplified envelope creating unit 111 that calculates an envelope of an input audio signal according to an input audio signal from an external device, creates a supply voltage control signal so that a waveform of the supply voltage control signal follows a waveform of the envelope, and outputs the supply voltage control signal to a voltage variable power supply 12 a constant time before the input audio signal is amplified by the amplifier 14. Accordingly, an amplifying device can be provided which can reduce the distortion of the output signal not depending on a change in the slew rate of the voltage variable power supply 12 and suppress the deterioration of power efficiency.