Parallel ADC Signal Chains for Chopping Ripple Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Analog to digital converter (ADC) circuits face challenges in removing ripples caused by chopping, which are errors related to input voltage offset, leading to increased complexity and power consumption, and higher input bias currents when higher chopping frequencies are used.
Innovation Solution
The approach involves using two parallel signal chains to process the same analog input signal, generating a difference signal to expose errors, modulating these errors with uncorrelated patterns, and demodulating them to recover and correct the errors in either the analog or digital domain, allowing the chopping frequency to be placed within the signal band, thereby simplifying the ADC system and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopping frequency is increased to place ripple outside signal band, then ripple can be filtered out more easily, but input bias currents increase and circuit complexity increases
Solution Approach 1:
The patent extracts the error signal (including ripple) from the main signal path by using a separate error detection path that processes the same input signal independently. The difference between the main path output and error path output isolates the error components, allowing targeted correction without requiring high chopping frequencies that increase bias current.
Solution Approach 2:
The patent introduces an intermediary error correction mechanism that operates in the digital domain after ADC conversion. By detecting errors through differential processing and applying corrections digitally, the system avoids the need for high-frequency chopping that would generate excessive bias currents, thus resolving the contradiction between ripple filtering effectiveness and power consumption.
2Measurement precision
If chopping frequency is increased to place ripple outside signal band, then ripple can be filtered out more easily, but circuit complexity and size increase
Solution Approach 1:
The patent extracts error components from the signal path by creating a parallel error detection path. This allows the main signal path to remain simple while the error path handles the complex task of error detection and correction, effectively reducing overall circuit complexity compared to high-frequency chopping approaches.
Solution Approach 2:
The patent replaces the mechanical/analog approach of high-frequency chopping with a digital signal processing approach. By using digital error detection, demodulation, and correction mechanisms, the system achieves effective ripple filtering without the circuit complexity and power consumption associated with high-frequency analog chopping circuits.
3Measurement precision
If chopping is used to remove voltage offset, then offset errors are reduced, but ripples are introduced in the output signal
Solution Approach 1:
The patent converts the harmful ripple effect into a detectable error signal. By using the same chopping mechanism in a parallel path and comparing outputs, the ripple and other errors are extracted as a separate signal that can be measured and corrected, transforming the harmful artifact into useful error information for compensation.
Solution Approach 2:
The patent implements a feedback mechanism where detected errors are fed back to correct the output signal. The error detection path monitors the chopping-induced ripples and offset errors, and the correction mechanism applies compensating signals to eliminate these harmful effects, maintaining the benefits of chopping while removing its detrimental consequences.
Data Source
AI summary
An analog to digital converter (ADC) system includes two signal paths in parallel with each other, where the signal paths include separate ADC circuits to separately operate on a same input signal and output separate digital signals. A difference signal is calculated as a difference of the digital signals output from the two signal paths to determine an error present in one or both of the signal paths. The error may be modulated in one or both of the signal paths and demodulated from the difference signal according to a same digital modulation pattern to compute an error compensation signal to compensate for at least one of the modulated error and a secondary error resulting from the modulation of the error.