Sigma-Delta ADC Decimation Filter Adaptation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing analog-to-digital conversion systems in motor control applications face challenges in adapting to varying operating conditions, particularly in three-phase motor systems, where measurement windows change with torque demands, affecting the precision and bit resolution of phase current measurements.
Innovation Solution
A method using a sigma-delta analog-to-digital converter (ADC) with a reconfigurable decimation filter that adjusts its filter order and decimation rate in response to changes in the measurement window, maintaining a consistent gain and achieving predetermined bit precision by synchronizing sampling times and using low-pass filtering to optimize bit resolution based on current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed configuration decimation filter is used in the sigma-delta ADC, then the device complexity is reduced, but the measurement precision deteriorates under varying torque conditions
Solution Approach 1:
The decimation filter is made reconfigurable with dynamically adjustable filter order and decimation rate based on measurement window conditions. The filter transitions from a fixed configuration to a dynamic one that adapts its parameters according to the actual measurement requirements, thereby maintaining high bit resolution across varying torque conditions without requiring multiple dedicated filter circuits.
Solution Approach 2:
The filter order and decimation rate parameters of the decimation filter are changed according to the measurement window size. When the measurement window is large (low-torque conditions), a higher filter order and decimation rate are applied to maximize bit resolution. When the measurement window is small (high-torque conditions), the filter order and decimation rate are reduced to accommodate the limited measurement time, thus optimizing measurement precision for each operating condition.
2Measurement precision
If the filter order and decimation rate are increased to improve bit resolution, then the measurement precision is improved, but the processing time increases
Solution Approach 1:
The filter order and decimation rate are dynamically adjusted based on the measurement window size rather than being fixed at high values. This dynamic adjustment allows the system to use higher processing complexity only when time permits (large measurement windows), and reduce processing complexity when time is constrained (small measurement windows), thereby resolving the trade-off between precision and processing time.
Solution Approach 2:
The decimation rate parameter is changed according to measurement conditions: higher decimation rates are applied when the measurement window is large to achieve high bit resolution, while lower decimation rates are used when the measurement window is small to complete processing within the available time. This parameter adaptation optimizes the balance between measurement precision and processing speed for each operating condition.
Data Source
AI summary
In some embodiments, a method of operating a sigma-delta analog-to-digital converter (ADC) includes converting an analog input signal into a sequence of digital data using a sigma-delta modulator of the sigma-delta ADC, setting a first configuration for a decimation filter of the sigma-delta ADC according to a first condition of a measurement window, filtering the sequence of digital data using a low-pass filter (LPF) of the decimation filter, and in response to a change in the measurement window, setting a second configuration for the decimation filter according to a second condition of the measurement window.