Amplifier Common-Mode Regulation for Startup Pop Noise
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Solution Overview
Problem
Class AB and class D amplifier circuitry in electronic systems generate undesirable audio disturbances due to voltage spikes during startup or idle times, resulting from unregulated common mode voltages.
Innovation Solution
Implementing common mode regulator circuitry with idle current source, feedback current source, and current sink circuitry to regulate common mode voltage by sourcing or sinking currents based on idle and feedback currents, reducing voltage spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If amplifier circuitry operates during startup or idle times, then the amplifier can begin processing signals, but unregulated common mode voltages cause voltage spikes that generate undesirable audio disturbances
Solution Approach 1:
The common mode regulator circuitry is activated before the main amplifier circuitry during startup, and remains active during idle times. This preliminary regulation of common mode voltages prevents voltage spikes from occurring when the amplifier begins operation, thereby eliminating audio disturbances while maintaining productivity.
2Device complexity
If common mode voltage is left unregulated, then the amplifier circuitry can operate with simpler design, but voltage spikes occur during startup and idle times causing audio disturbances
Solution Approach 1:
A common mode regulator circuitry is introduced as an intermediary component between the power supply and the main amplifier circuitry. This regulator circuit includes current source circuitry, current sink circuitry, and common mode voltage circuitry that work together to regulate common mode voltages, preventing voltage spikes without requiring fundamental changes to the main amplifier design.
3Object-affected harmful factors
If common mode regulator circuitry is added to regulate common mode voltage, then audio disturbances are reduced, but device complexity increases
Solution Approach 1:
The common mode regulator circuitry employs feedback mechanisms where the common mode voltage circuitry monitors the common mode voltages and adjusts the operation of current source and current sink circuitry accordingly. This feedback control automatically maintains stable common mode voltages during startup and idle times, reducing audio disturbances while managing complexity through intelligent control rather than purely passive components.
Data Source
AI summary
An example apparatus includes: current source circuitry having a first terminal, a second terminal, a third terminal, and a fourth terminal; current sink circuitry having a first terminal, a second terminal, a third terminal, and a fourth terminal; common mode voltage circuitry having a first terminal and a second terminal, the first terminal of the common mode voltage circuitry coupled to the first terminal of the current source circuitry and the first terminal of the current sink circuitry, the second terminal of the common mode voltage circuitry coupled to the second terminal of the current source circuitry and the second terminal of the current sink circuitry; idle current source circuitry having a terminal coupled to the third terminal of the current source circuitry; and feedback current source circuitry having a terminal coupled to the fourth terminal of the current source circuitry.