Thermistor PWM Temperature Sensing with Exponential Decay Linearization
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Solution Overview
Problem
Thermistors' temperature responses are highly non-linear, requiring complex analog-to-digital architectures and additional processing to convert to a digital PWM output, increasing circuit design complexity and cost.
Innovation Solution
A device incorporating a periodic exponential decay signal generating circuit and a PWM generating circuit to convert thermistor temperature responses into a PWM output signal with a duty cycle that varies linearly with temperature, eliminating the need for analog-to-digital converters and additional linearization processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an analog-to-digital converter and processing circuit are used to convert thermistor temperature response to digital PWM output, then the temperature measurement can be converted to digital format, but the circuit design complexity and production cost increase
Solution Approach 1:
The patent extracts and eliminates the complex ADC and processing circuitry from the temperature sensing system. Instead of converting the thermistor signal through multiple stages, the invention directly generates a PWM output signal whose duty cycle is proportional to temperature, removing unnecessary conversion stages and simplifying the overall circuit architecture.
Solution Approach 2:
The patent changes the output parameter format directly to PWM duty cycle representation. Rather than converting temperature to voltage then to digital values, the system directly modulates the PWM duty cycle according to temperature, achieving digital-friendly output without complex conversion circuits.
2Manufacturing precision
If an analog-to-digital converter and processing circuit are used to linearize the temperature response, then the non-linear thermistor response can be converted to linear temperature values, but the production cost increases
Solution Approach 1:
The patent removes the expensive processing circuitry required for linearization from the manufacturing bill of materials. By using a direct PWM generation approach where the duty cycle is inherently proportional to temperature, the system eliminates the need for additional processing components that increase production cost.
Solution Approach 2:
The temperature sensing circuit serves its own linearization function through the direct PWM generation mechanism. The system self-regulates the duty cycle based on temperature without requiring external processing circuits or complex calibration hardware, reducing manufacturing complexity and cost.
3Measurement precision
If complex conversion circuits are used to process thermistor output, then accurate temperature conversion can be achieved, but the system complexity increases
Solution Approach 1:
The patent merges the temperature sensing function with the PWM generation function into a single integrated process. The thermistor signal is directly fed into the PWM modulator, combining measurement and output generation in one stage, thereby maintaining accuracy while minimizing system complexity.
Solution Approach 2:
The PWM duty cycle serves as an intermediary that directly represents temperature without requiring additional conversion stages. This intermediary parameter simplifies the signal path while preserving temperature information, avoiding the need for complex intermediate processing circuits.
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 provides a simple circuit structure that generates a PWM output signal with a duty cycle that is substantially linear with temperature, reducing system complexity and cost while allowing direct temperature indication without further processing.
Implementation Method 1
The periodic exponential decay signal continuously and exponentially decays from an upper reference voltage to a lower reference voltage in each period of the periodic exponential decay signal
Implementation Method 2
The PWM generating circuit is configured to receive a temperature response of a thermistor and the periodic exponential decay signal, and to generate, according to the temperature response and the periodic exponential decay signal, a PWM output temperature sensing signal
Data Source
AI summary
A device includes a periodic exponential decay signal generating circuit and a pulse-width modulated (PWM) generating circuit. The periodic exponential decay signal generating circuit is configured to generate a periodic exponential decay signal. The periodic exponential decay signal continuously and exponentially decays from an upper reference voltage to a lower reference voltage in each period of the periodic exponential decay signal. The PWM generating circuit is configured to receive a temperature response of a thermistor and the periodic exponential decay signal, and to generate, according to the temperature response and the periodic exponential decay signal, a PWM output temperature sensing signal indicating sensed temperature of the thermistor.