Thermopile Array ADC Reference Chopping for Low-Noise Readout
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Solution Overview
Problem
Existing thermopile infrared sensors face challenges with high noise floor requirements, especially in large-scale arrays, leading to increased power consumption, self-heating, and reduced thermal resolution due to insufficient space for signal processing channels and high noise bandwidth.
Innovation Solution
A thermopile array with a delta-sigma ADC and reference voltage generation circuit that includes a chopping modulation unit and low-pass filter to reduce noise, combined with a large number of parallel signal processing channels and a low-power pre-amplifier structure, effectively reducing noise bandwidth and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of signal processing channels is increased to process more sensor pixels, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent divides the thermopile array into multiple groups, with each group processed by a dedicated signal processing channel. This segmentation allows efficient handling of large-scale arrays (e.g., 256+ pixels) by distributing the processing load across multiple channels, thereby improving measurement precision without overwhelming the device complexity with a single monolithic processing structure.
Solution Approach 2:
Multiple sensor pixels are combined and processed by shared signal processing channels. The patent implements a many-to-many mapping relationship where i sensor pixels (with i ≤ number of pixels/4) are processed by each channel, merging processing tasks to reduce the total number of channels needed while maintaining adequate measurement precision.
2Measurement precision
If conventional reference voltage generation is used, then the device complexity is low, but the noise floor is high which deteriorates measurement precision
Solution Approach 1:
The patent applies preliminary noise suppression action by introducing a chopping modulation unit before the reference voltage is used in the ADC. This unit modulates low-frequency noise (including 1/f noise) into high-frequency components, which are then filtered out, thereby improving the signal-to-noise ratio before the critical conversion stage.
Solution Approach 2:
A chopping modulation unit is introduced as an intermediary between the voltage generation unit and the ADC. This intermediary component transforms the noise characteristics of the reference voltage, converting problematic low-frequency noise into high-frequency noise that can be easily removed by a low-pass filter, thereby improving measurement precision without significantly increasing overall circuit complexity.
3Object-generated harmful factors
If power consumption is reduced to minimize self-heating, then the harmful factors are reduced, but the productivity may be affected
Solution Approach 1:
The patent employs parameter changes in the pre-amplifier design, using a single-stage amplifier structure with optimized gain distribution. This approach reduces the power consumption of each individual channel while maintaining adequate signal processing capability. The parameter optimization allows the system to process signals from multiple pixels per channel without excessive power draw, thereby reducing self-heating while preserving productivity.
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
Improves signal-to-noise ratio and thermal temperature resolution, reduces power consumption and design complexity, enabling efficient integration of large-scale thermopile arrays by minimizing noise and self-heating issues.
Implementation Method 1
a chopping modulation unit configured to perform chopping modulation on a voltage signal generated by the voltage generation unit, and modulate low-frequency noise of the voltage signal into high-frequency noise
Implementation Method 2
a low-pass filter configured to eliminate the high-frequency noise to obtain a reference voltage
Implementation Method 3
a pre-amplifier configured to amplify a sensor signal, the pre-amplifier being a single-stage amplifier
Data Source
AI summary
An analog-to-digital converter and a thermopile array. The analog-to-digital converter comprises: a reference voltage generation circuit comprising a voltage generation unit; a chopping modulation unit used to perform chopping modulation on a voltage signal generated by the voltage generation unit, and to modulate low frequency noise of the voltage signal into high frequency noise; and a low-pass filter used to eliminate the high frequency noise to obtain a reference voltage. The invention employs a simple structure to obtain a low noise reference voltage at low costs.