Audio Amplifier Soft Switching for Noise-Free Volume Changes
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Solution Overview
Problem
Existing signal amplifier circuits generate noise when rapidly switching resistance values to adjust sound volume, causing audible noise due to rapid changes in audio signal voltage.
Innovation Solution
A signal amplifier circuit design featuring multiple main amplifiers with adjustable gains, a soft switching circuit, and a controller that gradually transitions between input terminals to independently and smoothly adjust signal amplitudes, reducing noise and circuit area by sharing an auxiliary amplifier and soft switching circuit across multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If resistance value of variable resistor is rapidly switched to adjust volume, then volume control speed is improved, but noise is generated due to rapid voltage changes
Solution Approach 1:
The circuit prepares two parallel signal paths: one through the main amplifier with initial gain, and another through the auxiliary amplifier that will achieve target gain. The soft switching circuit gradually transitions between these pre-prepared paths, allowing the system to move from initial state to target state without rapid changes, thus preventing noise while maintaining fast overall response.
Solution Approach 2:
The soft switching circuit acts as an intermediary between the main amplifier output and the final output. It gradually mixes signals from both the main amplifier and auxiliary amplifier, smoothing the transition and preventing rapid voltage changes that would generate noise, while still enabling relatively fast volume adjustment.
2Adaptability or versatility
If separate auxiliary amplifiers and soft switching circuits are provided for each main amplifier, then independent amplitude control is improved, but circuit area increases
Solution Approach 1:
The patent merges multiple auxiliary amplifiers into a single shared auxiliary amplifier that receives inputs from multiple main amplifiers through a selector. Similarly, multiple soft switching circuits are consolidated into one shared circuit. This combining approach maintains independent control capability while significantly reducing the total number of components and circuit area.
Solution Approach 2:
The auxiliary amplifier and soft switching circuit are designed as universal components that can serve multiple main amplifiers. The selector switches allow the auxiliary amplifier to receive signals from different main amplifiers, and the soft switching circuit to manage transitions for any channel, making these components multi-functional and reducing overall circuit complexity.
Data Source
AI summary
A plurality of main amplifiers amplifies input audio signals with an adjustable gain. A first selector selects any of the input audio signals. An auxiliary amplifier receives an output of the first selector and amplifies this output with an adjustable gain. A second selector receives n outputs from the main amplifiers and selects any of the outputs. A soft switching circuit receives an output of the second selector at a first input terminal, receives an output of the auxiliary amplifier at a second input terminal, and makes the output transition gradually from one of the input terminals to the other of the input terminals. Output switches are respectively provided for the main amplifiers, an output of a corresponding main amplifier is received at a first input terminal, an output of the soft switching circuit is received at a second input terminal, and one of the outputs is selected to be outputted.