Audio Amplifier Pre-Charging Circuit for Faster Pop-Noise Suppression
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Solution Overview
Problem
Conventional audio amplification systems experience significant time delays and inefficiencies in charging decoupling capacitors, leading to prolonged pre-charge times and incomplete reduction of 'pop noise' due to high capacitance values and complex circuit requirements.
Innovation Solution
An amplification circuit that employs a combination of pulse density modulation and pulse width modulation signals, alternately generated and selected to rapidly charge the decoupling capacitor, utilizing a ramp generator and noise shaper to minimize noise and reduce pre-charge time, allowing the same audio amplifier to perform both pre-charging and amplification tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a decoupling capacitor with high capacitance value (100 μF to 220 μF) is used to prevent audio frequency removal, then the capacitor can maintain audio signal integrity, but the pre-charge time becomes too long (order of seconds)
Solution Approach 1:
The patent applies preliminary action by pre-charging the decoupling capacitor before the audio amplifier begins normal operation. A dedicated pre-charge circuit charges the capacitor to the supply voltage level in advance, so that when the amplifier starts driving the diffuser, the capacitor is already at the correct voltage level, preventing pop noise without requiring a long gradual charge time that would delay system activation.
Solution Approach 2:
The patent segments the capacitor charging process into two distinct phases: a pre-charge phase using a dedicated circuit that operates before audio signal processing, and a normal operation phase where the capacitor maintains its charge. This segmentation allows the capacitor to be charged rapidly in advance rather than attempting to charge it gradually during audio signal processing, resolving the contradiction between maintaining audio integrity and reducing pre-charge time.
2Object-affected harmful factors
If a resistive voltage divider is used to generate an increasing voltage signal for pre-charging the decoupling capacitor, then pop noise is reduced, but the pre-charge time becomes excessively long and the circuit complexity increases
Solution Approach 1:
The patent extracts the pre-charge function from the main audio amplifier circuit by implementing a dedicated pre-charge circuit. This separate circuit is specifically designed to charge the decoupling capacitor rapidly before audio processing begins, eliminating the need for the audio amplifier to gradually charge the capacitor through voltage dividers during signal processing, thus reducing both time and complexity.
Solution Approach 2:
The dedicated pre-charge circuit performs the capacitor charging action in advance, before the audio amplifier begins normal operation. This preliminary charging action ensures the capacitor is ready immediately when audio processing starts, preventing pop noise without requiring the audio amplifier to spend extended time charging the capacitor during signal processing.
3Object-affected harmful factors
If a dedicated pre-charge circuit with integrator is used to generate a linearly increasing voltage signal, then the decoupling capacitor can be pre-charged, but the circuit complexity and component count increase
Solution Approach 1:
The patent extracts the pre-charge function into a dedicated, simplified circuit that operates independently from the main audio amplifier. This pre-charge circuit uses basic components (switch, resistor, capacitor) to rapidly charge the decoupling capacitor, eliminating the need for complex integrators and width modulators that would be required to generate linearly increasing voltage signals during audio processing.
Solution Approach 2:
The decoupling capacitor serves its own pre-charge needs through a dedicated pre-charge circuit that directly charges it to the required voltage level. This self-service approach eliminates the need for the audio amplifier to perform dual functions of both audio processing and gradual capacitor charging, reducing overall system complexity while effectively preventing pop noise.
4Adaptability or versatility
If the audio amplifier is used to gradually charge the decoupling capacitor during audio signal processing, then the same amplifier performs both pre-charging and amplification, but the pre-charge time becomes too long and audio signal processing is delayed
Solution Approach 1:
The patent segments the amplifier's operations into two distinct time phases: a pre-charge phase where a dedicated circuit charges the capacitor, and a normal operation phase where the amplifier processes audio signals. This segmentation allows the capacitor to be charged rapidly in advance without interfering with audio processing, enabling the amplifier to begin audio amplification immediately without being delayed by gradual capacitor charging.
Solution Approach 2:
The dedicated pre-charge circuit performs the capacitor charging action in advance, before the audio amplifier begins normal operation. This preliminary charging action ensures the capacitor is ready immediately when audio processing starts, preventing pop noise without requiring the audio amplifier to spend extended time charging the capacitor during signal processing, thus improving system activation speed.
Data Source
AI summary
An amplification circuit for driving an audio signal diffuser that includes a generation circuit of a first pre-charging signal, the generation circuit including an amplifier provided with an input terminal for receiving the first pre-charging signal and provided with an output terminal for providing a second pre-charging signal as a function of the first pre-charging signal, and a decoupling capacitor of the amplifier from the diffuser, the capacitor connected to the output terminal for charging by the second pre-charging signal.