Time-Continuous Sigma-Delta Sensor Readout for Low-Power Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor systems, particularly those using capacitive sensors, face high power consumption issues, which is a significant challenge especially in mobile applications where prolonged operation without external energy supply is crucial.
Innovation Solution
The use of a time-continuous sigma-delta converter with a suitable evaluation interface between the sensor and loop filter, along with a digital-to-analog converter for feedback, reduces power consumption by up to a factor of 10 compared to time-discrete converters, and incorporates a bandpass sigma-delta converter for further power reduction through sub-Nyquist sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a time-discrete sigma-delta converter is used, then the signal processing capability is improved, but the power consumption increases significantly
Solution Approach 1:
The patent changes the fundamental operating parameter from time-discrete to time-continuous signal processing. This parameter change enables the system to achieve comparable signal processing capability while reducing power consumption by eliminating the need for high-speed switching operations and associated high-frequency clock signals that characterize time-discrete converters.
Solution Approach 2:
The patent substitutes the mechanical/electronic switching mechanism of time-discrete converters with a continuous analog integration mechanism. The time-continuous sigma-delta converter uses continuous integration in the loop filter rather than discrete-time switching and summation, fundamentally replacing the operational mechanism to reduce dynamic power consumption while maintaining measurement precision.
2Measurement precision
If additional electrical components are added for evaluation interface, then the sensor reading capability is improved, but the power consumption increases
Solution Approach 1:
The patent merges the evaluation interface functions directly into the sigma-delta converter structure. The capacitive sensor is integrated into the feedback branch of the converter, eliminating the need for separate evaluation electronics. This consolidation achieves accurate sensor reading while minimizing additional power consumption by sharing the continuous integration resource.
Solution Approach 2:
The time-continuous sigma-delta converter is designed to perform multiple functions: it acts as both the signal processing converter and the evaluation interface for the capacitive sensor. The loop filter serves dual purposes as both the integration element for conversion and the readout mechanism for the sensor, reducing the need for additional dedicated components and their associated power consumption.
3Use of energy by moving object
If a bandpass sigma-delta converter is used with sub-Nyquist sampling, then the power consumption is reduced, but the circuit complexity increases
Solution Approach 1:
The bandpass sigma-delta converter employs periodic sampling at a sub-Nyquist rate, utilizing the periodic nature of the modulated sensor signal. By sampling below the Nyquist frequency and relying on the periodic modulation to preserve signal information, the system reduces the sampling rate and associated power consumption while managing complexity through the regular periodic structure of the sampling process.
Data Source
Figure 1~2
Figure 3~4b
Figure 5a~7
AI summary
The invention relates to a circuit and method for sensor readings, wherein said sensor is mounted between the feedback branch and loop-filter of a sigma-delta converter in such a way that feedback signals thereof compensate, in a temporal mean, the action of a measuring quantity on the sensor, the inventive circuit and method are characterised in that the used converter is embodied in the form of a time-continuous sigma-delta converter. Said circuit and method make it possible to substantially reduce the energy consumed by the sensor system.