Amplifier Reference Voltage Discharge for Click-and-Pop Suppression
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Solution Overview
Problem
Audio amplifiers experience unwanted transient signals, specifically 'click' and 'pop,' during power-down due to the discharge of the reference voltage, which is problematic in portable and non-portable applications, particularly in single supply amplifiers that charge to a defined voltage and then discharge, leading to audible issues.
Innovation Solution
An amplifier power-down apparatus and method that includes a discharge control circuit with a positive feedback path to control the current flow from the capacitor, smoothing the discharge of the reference voltage and reducing audible transient signals by creating an artificial reference voltage for comparison with the actual voltage, thereby minimizing slope discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the reference voltage generator circuit is disabled during power-down, then power consumption is reduced, but transient signals (click and pop) are generated due to voltage discharge
Solution Approach 1:
The discharge control circuit is activated before the reference voltage generator is fully disabled to preemptively control the discharge process. By preparing the discharge path in advance through the positive feedback mechanism, the circuit prevents sudden voltage changes that would cause transient signals, while still allowing power-down to occur.
Solution Approach 2:
The discharge control circuit employs a positive feedback path that monitors the reference voltage level and automatically adjusts the discharge current accordingly. As the voltage decreases, the feedback mechanism modulates the discharge rate to maintain a smooth transition, preventing the abrupt changes that generate click and pop sounds.
2Loss of time
If the reference voltage discharges quickly to ground, then power-down time is reduced, but slope discontinuities cause audible transient signals
Solution Approach 1:
The discharge control circuit dynamically adjusts the discharge characteristics based on the instantaneous voltage level. The positive feedback mechanism creates a time-varying discharge path that adapts to the changing voltage conditions, enabling the system to achieve both reasonable discharge speed and smooth voltage transition without audible transients.
Solution Approach 2:
The circuit changes the effective discharge parameters (resistance, current) as the voltage decreases. Through the positive feedback path, the discharge control circuit modifies the discharge characteristics in real-time, transforming the fixed discharge process into a variable one that maintains smooth voltage slope throughout the power-down sequence.
3Productivity
If the discharge current is increased to speed up power-down, then productivity is improved, but transient signals are amplified
Solution Approach 1:
The positive feedback path continuously monitors the voltage discharge process and automatically regulates the current magnitude. This feedback control prevents excessive current that would cause transients while maintaining sufficient discharge speed for acceptable power-down time, optimizing both productivity and signal quality.
Solution Approach 2:
The discharge current parameter is dynamically changed during the power-down process rather than remaining constant. The positive feedback mechanism ensures the current is higher when needed for speed but automatically reduced as voltage decreases, preventing transient signal amplification while maintaining overall power-down efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces or suppresses high-frequency components associated with 'click' and 'pop' effects, ensuring a smoother and more controlled discharge of the reference voltage, thereby minimizing unwanted audio signals during power-down.
Implementation Method 1
The discharge control circuit comprises an amplifier with a positive feedback path for controlling a current flow from the capacitor
Data Source
AI summary
An amplifier power-down apparatus for suppressing transient signals in a circuit, for example an audio circuit, comprising a reference voltage generator circuit for generating a reference voltage. The reference voltage generator circuit comprises a capacitor for maintaining the reference voltage at a desired level. The amplifier power-down apparatus comprises a discharge control circuit for controlling the operation of the reference voltage generator circuit during power-down. The discharge control circuit comprises an amplifier with a positive feedback path for controlling a current flow from the capacitor during power-down.