Adaptive Pre-Distortion Audio Amplifier for Low-Impedance Loads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional audio amplifiers face challenges in maintaining low distortion, especially when driving low impedance loads, which often requires increased power consumption and circuit complexity, making them unsuitable for battery-powered devices that prioritize size and cost efficiency.
Innovation Solution
An audio driving circuit with a pre-distortion module that applies a non-linear distortion function based on distortion settings, controlled by an error block that determines the difference between input and output signals, and an adaptive linear transfer function to mitigate distortion, while maintaining low power consumption and compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the output stage quiescent current is increased to maintain low distortion into low impedance load, then distortion performance is improved, but power consumption increases
Solution Approach 1:
The pre-distortion module applies a predetermined inverse distortion characteristic to the audio signal before amplification, pre-compensating for the amplifier's non-linearities. This allows the amplifier to operate with lower quiescent current while still achieving low distortion performance, resolving the contradiction between distortion performance and power consumption
Solution Approach 2:
The error block continuously monitors the difference between the input signal and the actual output signal, and feeds this error information back to adjust the pre-distortion settings. This closed-loop feedback mechanism enables the system to maintain optimal distortion performance with minimized power consumption by dynamically adapting to operating conditions
2Manufacturing precision
If larger output driving devices and higher current pre-driver stages are used to maintain low distortion, then distortion performance is improved, but circuit size and complexity increase
Solution Approach 1:
By applying pre-distortion to the signal before amplification, the system compensates for amplifier non-linearities through signal processing rather than requiring oversized physical components. This reduces circuit size and complexity while maintaining distortion performance
Solution Approach 2:
The invention replaces the traditional mechanical/approach of using larger physical components (bigger transistors, higher current stages) with a digital/signal-processing approach (pre-distortion algorithms). This substitution reduces circuit size and complexity while achieving the same distortion performance goals
3Manufacturing precision
If multiple amplifier stages with high open-loop gain are used to suppress output distortion, then distortion performance is improved, but power consumption and circuit complexity increase
Solution Approach 1:
The pre-distortion module performs distortion compensation in advance, before the signal enters the amplifier stages. This eliminates the need for multiple high-gain amplifier stages and complex feedback networks, reducing circuit complexity while maintaining distortion performance
Solution Approach 2:
The invention extracts the distortion compensation function from the main amplifier signal path and places it in a separate pre-processing stage. This allows the amplifier itself to be simpler with fewer stages, as the distortion correction is handled independently by the pre-distortion module
Data Source
AI summary
This application relates to methods and apparatus for amplification of audio signals with improved audio performance. An audio driving circuit has an amplifier module in a forward signal path between an input for receiving an input audio signal (SIN) and an output for outputting an audio driving signal (VOUT). A pre-distortion module is operable to apply a first transfer function to the signal in the forward signal path upstream of the amplifier module, wherein the first transfer function comprises a non-linear distortion function based on at least one distortion setting. An error block is arranged to receive a first signal (SFF) derived from the input signal and a second signal (SFB) indicative of the voltage of the audio driving signal and determine a first error signal (ε1) indicative of a difference between the first and second signals. The pre-distortion module is operable to control the distortion setting(s) based on the first error signal.