Audio Switch On-Resistance Compensation for Lower THD
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Solution Overview
Problem
Audio switch circuits experience on-resistance variations with changing input voltages, which negatively impact audio signal fidelity and introduce total harmonic distortion (THD).
Innovation Solution
An audio switch circuit with an on-resistance compensation circuit that adjusts its on-resistance in response to input voltage changes, offsetting the positive changes in the audio switch's on-resistance to maintain a relatively constant overall on-resistance, thereby reducing Rflatness and improving THD. The compensation circuit can be configured in parallel or series with the audio switch and utilizes CMOS switches with gate voltage generators to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an audio switch is used to transfer audio signals, then signal routing functionality is achieved, but on-resistance variation occurs with changing input voltages causing audio fidelity degradation
Solution Approach 1:
The patent implements a feedback mechanism where the changing on-resistance of the audio switch is detected and compensated by an opposing change in the on-resistance compensation circuit. The compensation circuit monitors the input voltage changes and adjusts its own resistance characteristics to counteract the variations in the audio switch, thereby maintaining stable overall on-resistance and improving audio signal fidelity.
Solution Approach 2:
The patent changes the resistance parameter of the compensation circuit dynamically in response to input voltage changes. By adjusting the on-resistance of the compensation circuit to vary in opposition to the audio switch's resistance changes, the system maintains a relatively constant total on-resistance. This parameter adjustment approach directly addresses the on-resistance stability issue while preserving signal routing functionality.
2Adaptability or versatility
If the on-resistance of the audio switch changes with input voltage, then the switch operates across different voltage levels, but total harmonic distortion increases and audio fidelity deteriorates
Solution Approach 1:
The compensation circuit uses feedback to detect input voltage changes and their effect on the audio switch's on-resistance. By continuously monitoring and responding to these changes, the compensation circuit adjusts its resistance to offset the variations, thereby reducing total harmonic distortion and maintaining audio fidelity across different voltage levels.
Solution Approach 2:
The patent converts the harmful effect of on-resistance variation into a beneficial outcome by using the same voltage-dependent resistance characteristic in the compensation circuit to counteract the audio switch's resistance changes. The harmful resistance variation is transformed into a compensating mechanism that improves audio signal quality and reduces distortion.
3Manufacturing precision
If an on-resistance compensation circuit is added to offset resistance variations, then audio fidelity is improved, but circuit complexity increases
Solution Approach 1:
The patent achieves on-resistance stability by changing the resistance parameter of the compensation circuit in response to input voltage variations. This parameter-based approach allows the system to maintain stable overall on-resistance without requiring complex structural modifications, thereby improving audio fidelity while limiting the increase in circuit complexity to functional rather than structural complexity.
Data Source
AI summary
According to an implementation, an audio switch circuit includes an audio switch configured to selectively couple an input node to an output node to transfer an audio signal across the audio switch. The audio switch has an on-resistance in response to the input node being coupled to the output node. The on-resistance of the audio switch changes by a first value in response to an input voltage of the audio signal increasing from a first level to a second level. The audio switch circuit includes an on-resistance compensation circuit configured to have an on-resistance that changes by a second value in response to the input voltage of the audio signal increasing from the first level to the second level. The on-resistance compensation circuit is coupled to the audio switch such that the second value at least partially offsets the first value.