Variable Gain Amplifier Attenuator Stepwise Control
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Solution Overview
Problem
Conventional audio signal amplifiers experience signal distortion and increased microcomputer load when switching gain levels, leading to unpleasant noise such as click sounds during volume adjustments.
Innovation Solution
A variable gain amplifier system incorporating an attenuator with a comparison determination circuit and up-down counter to stepwise adjust the attenuation factor, minimizing signal distortion and reducing microcomputer load by allowing gradual gain changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gain of the audio signal amplifier is switched all at once from the largest gain to the smallest gain, then the gain switching speed is improved, but signal distortion occurs and unpleasant noise is emitted
Solution Approach 1:
The gain switching process is segmented into multiple discrete steps rather than a single abrupt change. The up-down counter divides the gain adjustment into incremental steps, where each step changes the gain by a small amount. This segmentation allows the gain to transition smoothly from maximum to minimum (or vice versa) through intermediate states, preventing signal distortion and click sounds while maintaining relatively fast switching speed.
2Object-generated harmful factors
If the gain is switched in a stepwise manner to prevent distortion, then signal quality is improved, but the microcomputer load increases due to software control requirements
Solution Approach 1:
The gain control system is designed to be self-service by implementing the stepwise gain switching logic directly in the circuit hardware rather than requiring software control. The comparison determination circuit automatically compares the current gain state with the target gain state and generates appropriate up/down signals to drive the up-down counter. This hardware-based automatic control eliminates the need for microcomputer intervention in the gain switching process, reducing microcomputer load while maintaining signal quality.
3Object-generated harmful factors
If a time constant circuit including a capacitor is used to gradually change the gain, then click sound is reduced, but the gain cannot be switched to a large degree quickly
Solution Approach 1:
The system employs dynamic control where the gain switching behavior adapts based on the relationship between current and target gain states. The comparison determination circuit dynamically generates up signals or down signals depending on whether the current gain is below or above the target gain. This dynamic hardware control enables both gradual transitions (reducing click sounds) and large-degree switching (when needed), overcoming the limitations of fixed time constant circuits.
Data Source
AI summary
An attenuator attenuates input signals and outputs the signals to an amplifier arranged to amplify signals applied to two input terminals. The attenuator includes first and second output terminals to be respectively connected to the two input terminals of the amplifier, a comparison determination circuit arranged to compare a data variable corresponding to a current attenuation factor with target data corresponding to an attenuation factor as a target value, to output an up signal or a down signal, and an up-down counter arranged to increase or decrease the data variable based upon the up signal or the down signal which is outputted from the comparison determination circuit. The input signals respectively attenuated by different attenuation factors are outputted to the first and second output terminals based upon the data variable outputted from the up-down counter. Since the attenuation factor changes in a stepwise manner by the provision of target data alone from the outside which corresponds to the attenuation factor as the target value, signal distortion is minimized.