Modulated Resistor Trimming for Audio Feedback Network Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mismatches between resistor networks in audio systems introduce unwanted signals, such as common mode harmonics and errors in reference currents/voltages, degrading system performance.
Innovation Solution
Incorporation of trimmable resistor networks and a trim control circuit to adjust resistor network resistances using modulated signals, ensuring precise matching and minimizing voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistor networks are used in audio systems, then the system provides negative feedback and sets amplification gain, but resistor mismatches introduce unwanted signals such as common mode harmonics and errors in reference currents/voltages
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the resistance values of trimmable resistors using modulated signals. The trim control circuit varies resistance parameters in response to detected harmonic distortion levels, thereby optimizing the matching between resistor networks and minimizing unwanted signals while maintaining system reliability
Solution Approach 2:
The patent implements feedback mechanisms where the trim control circuit continuously monitors the output signals for harmonic distortion and common mode errors. Based on this feedback, the circuit automatically adjusts the trimmable resistor values to eliminate mismatches, creating a closed-loop system that maintains signal integrity while reducing harmful distortions
2Reliability
If trimmable resistor networks are added to match resistor values, then harmonic distortion is reduced and signal integrity is enhanced, but device complexity increases
Solution Approach 1:
The trim control circuit serves multiple functions: it detects harmonic distortion, measures mismatch levels, generates modulated trim signals, and controls the trimmable resistors. By consolidating these functions into a single multi-functional circuit, the patent achieves precise resistor matching without proportionally increasing overall device complexity
Solution Approach 2:
The system performs self-trimming automatically without requiring external intervention. The trim control circuit autonomously detects mismatches, generates appropriate trim signals, and adjusts the resistor values to achieve optimal matching, thereby reducing the need for manual calibration and simplifying the overall system operation despite the added circuitry
3Manufacturing precision
If modulated signals are used to trim resistors, then precise resistance matching is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces traditional mechanical trimming methods (such as physical resistor adjustment or laser trimming) with electronic modulation techniques. By using modulated signals to control the effective resistance of trimmable resistors, the system achieves precise matching without requiring complex mechanical fabrication processes, thereby improving manufacturing precision while maintaining ease of manufacture through standard electronic fabrication techniques
Data Source
AI summary
In one example, an apparatus comprise: a first power stage having a first power stage input and a first power stage output; a second power stage having a second power stage input and a second power stage output; a driver circuit having a first driver input, a second driver input, a first driver output, and a second driver output, the first driver output coupled to the first power stage input, and the second driver output coupled to the second power stage input; a first resistor network coupled between a first input of a pair of differential inputs and the first power stage output, the first resistor network including a trimmable resistor network and a trim input; a second resistor network coupled between a second input of the pair of differential inputs and the second power stage output; and a control circuit having a trim output coupled to the trim input.