RMS-to-DC Converter High-Order Filter Ripple Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RMS-to-DC converters suffer from output ripple errors due to incomplete suppression of alternating waveforms, which are not adequately reduced by existing post-filters, especially in high-resolution applications, leading to increased settling time and additional errors from dynamic range limitations.
Innovation Solution
Incorporating a high-order low-pass filter, such as a two-pole filter connected in series, to cooperatively reduce output ripple and DC errors, while maintaining the dynamic range and settling time, by adjusting the separation of cutoff frequencies to optimize ripple suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long time constant low-pass filter is used to reduce output ripple, then ripple reduction is improved, but settling time increases
Solution Approach 1:
The patent divides the filtering function into two separate stages: a first low-pass filter with a longer time constant for ripple reduction, and a second low-pass filter with a shorter time constant for maintaining fast settling. This segmentation allows each filter to be optimized for its specific function, resolving the contradiction between ripple reduction and settling time.
2Measurement precision
If a multipole post-filter is used to reduce output ripple, then ripple reduction is improved, but circuit complexity increases
Solution Approach 1:
Instead of using a single complex multipole post-filter, the patent segments the filtering into two simpler low-pass filters placed at different locations in the circuit. This achieves equivalent or superior ripple reduction while maintaining lower circuit complexity and easier implementation.
3Measurement precision
If two RMS-to-DC converters are connected in series or parallel to reduce ripple, then ripple reduction is improved, but cost and circuit complexity increase
Solution Approach 1:
The patent applies segmentation by placing two low-pass filters at different stages (one in the feedback path and one as post-filter) rather than using two complete RMS-to-DC converter units. This achieves the desired ripple reduction effect while significantly reducing circuit complexity and cost compared to cascading multiple converters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The high-order filter effectively reduces output ripple from 4.2% to 0.5% and minimizes additional errors introduced by low duty cycles, without significantly increasing settling time, thus providing a more accurate and efficient RMS-to-DC conversion.
Implementation Method 1
a first low-pass filter having a first time constant and a second low-pass filter having a second time constant, the first low-pass filter and the second low-pass filter being connected in series
Data Source
AI summary
A circuit for providing a DC output equal to the RMS value of a time-varying input signal, the circuit including: (i) an RMS-to-DC converter for producing the DC output and (ii) a high-order low-pass filter comprising at least first and second low-pass filters connected in series to cooperatively reduce at least one of ripple in the DC output, ripple in an denominator feedback loop, or DC error in the DC output.