Variable-Gain ADC Control for Fast Switching Without Sound Degradation
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Solution Overview
Problem
Existing A/D conversion devices face issues with delayed gain switching in response to input level changes, complex circuit configurations, and frequent gain switching leading to sound degradation, particularly in floating-point A/D conversion systems.
Innovation Solution
An A/D conversion device with a variable-gain amplifier that uses a combination of analog and digital comparators, an FPGA, and a state counter to rapidly adjust gain based on predefined reference levels, reducing the need for complex analog circuits and minimizing frequent gain switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gain switching is controlled based on ADC output digital sample, then gain can be adjusted according to signal level, but gain switching is delayed due to ADC processing time
Solution Approach 1:
The patent performs gain control based on the analog signal level before A/D conversion, rather than waiting for the ADC output. By detecting the analog signal level in advance and adjusting the gain accordingly, the system eliminates the delay caused by ADC processing time and achieves immediate gain switching response.
2Speed
If analog circuits are used to compare signal levels and control gain switching, then gain can be adjusted in real-time, but the circuit configuration becomes complex and large
Solution Approach 1:
The patent replaces complex analog comparison circuits with a simplified analog-to-digital conversion followed by digital comparison. The analog signal is converted to digital by the ADC, and then digital logic circuits compare the digital value with reference levels to control gain switching. This substitution reduces circuit complexity while maintaining real-time response capability.
3Speed
If gain is determined by analog signal voltage during sampling period, then gain can be quickly adjusted, but frequent gain switching occurs when signal is close to zero causing sound degradation
Solution Approach 1:
The patent performs gain control based on the analog signal level before A/D conversion, rather than waiting for the ADC output. By detecting the analog signal level in advance and adjusting the gain accordingly, the system eliminates the delay caused by ADC processing time and achieves immediate gain switching response.
Solution Approach 2:
The patent uses a predetermined period threshold for gain increase decisions, requiring the signal to remain within the lower level range for a sustained period before triggering gain increase. This prevents premature or excessive gain switching that would occur with immediate response to transient low-level signals, thereby avoiding sound degradation.
Data Source
AI summary
An amplifier performs analog amplification on a signal I_A with a gain corresponding to a state GS and outputs the amplified signal as a signal M_A. An ADC converts the signal M_A to a digital signal and outputs the digital signal as a signal M_D. Analog comparators and a down-determination unit detect that the signal M_A exceeds a first level, and cause the state GS to transition to a state of gain of the next lower stage. Digital comparators and an up-determination unit detect that the signal M_D has been continuously lower than a second level for a predetermined period, and cause the state GS to transition to a state of gain of the next higher stage. The restoration circuit performs digital amplification on the signal M_D with a gain corresponding to the gain of the amplifier and outputs the amplified signal as a signal O_D.