Temperature Sensor Signal Circuit With Single-Converter Compensation
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Solution Overview
Problem
Existing contactless temperature sensor circuits are complex and consume significant silicon area and current, particularly due to the need for two separate analog-to-digital converters to measure object and ambient temperatures simultaneously, which can lead to errors and increased power consumption.
Innovation Solution
A signal processing circuit that combines three input signals using summation nodes, a selector, integrator, and comparator to produce a binary bit-stream with an average value indicative of object temperature, allowing for single conversion and reduced complexity, area, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two separate analog-to-digital converters are used to measure object and ambient temperatures simultaneously, then measurement accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines the functions of measuring object temperature and ambient temperature into a single analog-to-digital converter by using a thermopile with separate hot and cold junctions. The hot junction measures object temperature while the cold junction measures ambient temperature, and both measurements are obtained through one converter rather than two separate converters, thereby reducing circuit complexity while maintaining measurement accuracy.
Solution Approach 2:
The single analog-to-digital converter is designed to perform multiple functions: it converts both the object temperature signal from the hot junction and the ambient temperature signal from the cold junction into digital values. This multi-functional approach eliminates the need for separate converters and reduces overall device complexity.
2Measurement precision
If two separate analog-to-digital converters are used to measure object and ambient temperatures simultaneously, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The patent merges the power consumption of two separate analog-to-digital converters into a single converter, thereby halving the power consumption associated with temperature-to-digital conversion while maintaining the capability to measure both object and ambient temperatures simultaneously through the thermopile's dual junction design.
3Device complexity
If ambient temperature is measured separately between object temperature measurements, then device complexity is reduced, but measurement accuracy deteriorates due to temperature changes
Solution Approach 1:
The patent implements preliminary action by continuously maintaining both hot and cold junction measurements simultaneously through the thermopile structure. The cold junction (ambient temperature) is continuously monitored alongside the hot junction (object temperature), ensuring that ambient temperature data is always current and accurate when used for compensation calculations, rather than being measured separately at a later time.
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 solution enables compact, efficient temperature sensing with reduced current consumption and area usage, avoiding errors from ambient temperature changes between measurements, while directly providing object temperature readings.
Implementation Method 1
Generation of a voltage in a thermopile may occur as a result of the physical effect known as the Seebeck effect. With heating concentrated on a surface corresponding to a 'hot' junction of a thermopile and a 'cold' junction designed in order to be insensitive to such a temperature increase, a thermopile will produce, due to the Seebeck effect, a voltage difference which is a function of such heating, namely a voltage difference indicative of (for example, proportional to) the temperature of the object.
Data Source
AI summary
A circuit includes a first input terminal, a second input terminal, a third input terminal and an output terminal. A first summation node adds signals at the first and third input terminals. A second summation node subtracts signals at the second and third input terminals. A selector selects between the added signals and subtracted signals in response to a selection signal. The output of the selector is integrated to generate an integrated signal. The integrated signal is compared by a comparator to a threshold, the comparator generating an output signal at the output terminal having a first level and a second level. Feedback of the output signal produces the selection signal causing the selector to select the added signals in response to the first level of the output signal and causing the selector to select the subtracted signals in response to the second level of the output signal.