Audio Output Amplifier Startup Circuit for Pop Noise Reduction
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Solution Overview
Problem
Existing audio player devices generate startup noise due to instantaneous voltage rises, degrading user experience.
Innovation Solution
An audio player device with a slow startup mechanism, featuring a digital-to-analog converter (DAC), a startup circuit, a multiplexer, and an output amplifier, which gradually increases the startup voltage according to a reference voltage during a predetermined period, preventing sudden voltage jumps and noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the amplifier is instantaneously powered on, then the startup speed is fast, but the internal voltage rises suddenly causing noise generation
Solution Approach 1:
The startup circuit is activated before the main power switch to pre-charge the internal voltage to a safe level. This preliminary action prevents sudden voltage spikes when the amplifier starts, thereby eliminating startup noise while maintaining fast startup performance.
Solution Approach 2:
A startup circuit is introduced as an intermediary component between the power source and the amplifier. This intermediate circuit gradually increases the internal voltage through controlled charging, acting as a buffer that prevents direct instantaneous voltage application to the amplifier, thus avoiding noise generation.
2Object-generated harmful factors
If the internal voltage is gradually increased, then the startup noise is reduced, but the startup time is extended
Solution Approach 1:
The startup circuit performs the voltage ramping operation in advance before the amplifier begins normal operation. By completing the gradual voltage increase during a predetermined interval before the main power switch activates, the system achieves both noise reduction and minimal impact on perceived startup time.
Solution Approach 2:
The startup circuit dynamically adjusts the voltage increase rate based on the predetermined time interval. The circuit transitions from a gradual charging phase to a rapid stabilization phase, optimizing the balance between noise reduction and startup speed by adapting the charging rate to different operational stages.
Data Source
AI summary
An audio player device includes a digital-to-analog converter (DAC), a startup circuit, a multiplexer and an output amplifier. The DAC converts audio data into a first signal and a second signal. The startup circuit gradually increases a level of a startup voltage according to a reference voltage during a predetermined period. The multiplexer outputs the startup voltage as a control voltage during the predetermined period, and switches to output the reference voltage as the control voltage after the predetermined period has elapsed. The output amplifier generates an audio signal according to the control voltage, the first signal and the second signal. The control voltage is used to set a common mode voltage of the output amplifier.