Multi-Path Audio Amplifier Gain Calibration for Click-Free Mode Switching
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Solution Overview
Problem
Existing audio amplifier systems, particularly those using single PWM amplifier circuits, experience perceptible audio artifacts such as 'pops' and 'clicks' when switching between open-loop and closed-loop operations, due to gain mismatches caused by changes in load transducer impedance and temperature effects.
Innovation Solution
A multi-path subsystem with a calibration engine that estimates and cancels DC offsets, phase differences, and gain variations between processing paths, ensuring equal gains for open-loop and closed-loop paths to minimize switching artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single PWM amplifier circuit is used to drive loads in either open-loop or closed-loop mode, then power efficiency is improved, but perceptible audio artifacts occur when switching between modes
Solution Approach 1:
The amplifier system is divided into two separate processing paths: an open-loop path and a closed-loop path. Each path has its own PWM amplifier circuit, allowing independent optimization and calibration of each mode without interference, thereby eliminating audio artifacts during mode switching while maintaining power efficiency benefits
Solution Approach 2:
The system dynamically changes operating parameters (gain settings, modulation characteristics) based on the selected mode. A calibration engine adjusts the gain of the open-loop path to match the closed-loop path, ensuring seamless transitions without perceptible artifacts while maintaining optimal power efficiency for each operating condition
2Object-generated harmful factors
If gain calibration is performed to equalize open-loop and closed-loop paths, then audio artifact reduction is improved, but system complexity increases
Solution Approach 1:
A calibration engine implements feedback control by measuring the gain difference between open-loop and closed-loop paths and automatically adjusting the open-loop gain to match the closed-loop gain. This closed-loop calibration process eliminates the need for complex manual adjustment while reducing audio artifacts
Solution Approach 2:
The calibration engine performs self-calibration of the system by automatically detecting and correcting gain mismatches between the two processing paths. This self-service approach simplifies the overall system architecture by eliminating the need for external calibration equipment or complex manual adjustment mechanisms
Data Source
AI summary
A multi-path subsystem may include a first processing path, a second processing path, a mixed signal return path, and a calibration engine configured to: estimate and cancel a direct current (DC) offset of the mixed signal return path, estimate and cancel a DC offset between the first processing path and the second processing path, estimate and cancel a phase difference between the first processing path and a sum of the second processing path and the mixed signal return path, estimate and cancel a return path gain of the mixed signal return path, and track and correct for a gain difference between the first processing path and the second processing path.