Class-D Audio Output Stage Switching for Low Noise and Small ADC
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Class-D power amplifiers in audio processing circuits require a large analog-to-digital converter (ADC) for feedback, limiting the reduction of chip area and performance improvement due to their closed-loop structure, especially when digital modulation circuits are implemented, which hinders the benefits of advanced semiconductor processes.
Innovation Solution
An audio processing circuit with a digital signal processing circuit, digital modulation circuit, output stage, voltage regulator, and signal detection circuit that dynamically switches between open-loop and closed-loop structures based on signal strength, using a voltage regulator to reduce noise in low-volume signals and enabling a smaller ADC in high-volume signals, thus optimizing chip area and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed-loop structure is used in the class-D power amplifier to eliminate nonlinear phenomena and noise, then performance indicators such as THD+N, IMD, and PSRR are improved, but a large area ADC is required in the feedback path, preventing further reduction of chip area
Solution Approach 1:
The patent implements dynamic switching between open-loop and closed-loop structures based on signal strength detection. When the input signal exceeds a threshold, the system switches to open-loop mode to disable the feedback path and ADC, thereby reducing chip area utilization and power consumption while maintaining performance for strong signals.
Solution Approach 2:
The patent applies different operational modes to different signal conditions: closed-loop mode is used for weak signals to maintain high performance indicators, while open-loop mode is used for strong signals to reduce chip area and power consumption requirements.
2Area of stationary object
If digital circuits are used to implement the modulation circuit to benefit from advanced semiconductor processes, then chip area is reduced, but an ADC must be positioned in the feedback path which requires analog circuits and cannot enjoy the benefits of advanced semiconductor processes
Solution Approach 1:
The patent dynamically configures the feedback path based on signal strength. For strong signals, the feedback path is disabled, allowing the modulation circuit to be fully digital and benefit from advanced semiconductor processes. For weak signals, the feedback path is enabled to maintain performance.
3Reliability
If a larger area ADC is designed to maintain the performance of the class-D power amplifier, then performance indicators are improved, but the chip area of the audio processing circuit cannot be further reduced
Solution Approach 1:
The patent applies closed-loop feedback with ADC only when necessary (for weak signals below the threshold), and disables it for strong signals. This partial application of the feedback mechanism maintains performance where needed while minimizing chip area usage.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention discloses an audio processing circuit (100), wherein when the audio processing circuit (100) determines that a signal being processed is a small signal, an output stage (160) uses a regulated supply voltage provided by a voltage regulator (190), and the output stage (160) uses an open-loop structure to reduce noise of an output audio signal; and when the audio processing circuit (100) determines that the signal being processed is a large signal, the output stage (160) directly uses the supply voltage without using the regulated supply voltage, and the output stage (160) uses a closed-loop structure to reduce the total harmonic distortion of the output audio signal. By using the present invention, the audio processing circuit (100) can have a good performance indicator with a small chip area design.