Semiconductor Temperature Sensor Using PWM Digital Output
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Solution Overview
Problem
Existing semiconductor temperature sensors based on PN junctions suffer from low sensitivity, high power consumption, and complexity due to the need for analog-to-digital conversion and low-noise amplification, making them unsuitable for low-cost, low-power applications, especially in wearable devices.
Innovation Solution
A semiconductor temperature sensor using a reverse-biased diode, capacitor, and resistor with a digital circuit that generates a pulse-width-modulated (PWM) signal, eliminating the need for an analog-to-digital converter and low-noise amplification, and utilizing a Schottky diode for improved sensitivity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PN junction temperature sensors with analog output are used, then temperature sensing capability is achieved, but sensitivity is low and power consumption is high due to required analog-to-digital conversion and amplification
Solution Approach 1:
The patent replaces the traditional analog measurement system (requiring ADC and amplification) with a direct digital pulse output system. The temperature sensor generates PWM pulses whose duty cycle directly represents temperature, eliminating the need for analog-to-digital conversion and low-noise amplification, thereby reducing power consumption while maintaining measurement precision
Solution Approach 2:
The patent changes the output parameter form from analog voltage to digital pulse width modulation. By using a voltage comparator to generate PWM signals where the pulse width is proportional to temperature, the system achieves high sensitivity without requiring power-hungry analog processing circuits
2Measurement precision
If PN junction temperature sensors with analog output are used, then temperature sensing is achieved, but device complexity increases due to required analog-to-digital converter and amplification chain
Solution Approach 1:
The patent substitutes complex analog processing circuitry (ADC, amplifiers, filters) with a simple digital pulse generation approach. The voltage comparator directly converts temperature information into PWM pulse width, which can be easily processed by digital systems, thereby reducing device complexity while preserving temperature resolution
Solution Approach 2:
The patent extracts and eliminates the unnecessary analog processing stage from the temperature sensing system. By directly generating digital PWM output from the voltage comparator, the system removes the analog-to-digital converter and amplification chain, simplifying the overall device architecture
3Measurement precision
If PN junction temperature sensors are used, then temperature measurement is achieved, but sensitivity is limited due to process spread causing differences in reverse saturation currents
Solution Approach 1:
The patent inverts the traditional approach by using the voltage comparator to directly compare the diode voltage against a reference, generating a PWM output where the pulse width is proportional to temperature. This inversion eliminates the need for precise matching of reverse saturation currents, as the differential voltage is directly converted to pulse width, improving both sensitivity and measurement consistency
Solution Approach 2:
The patent introduces a voltage comparator as an intermediary element that converts the analog voltage difference (caused by temperature-dependent reverse saturation currents) directly into a digital PWM signal. This intermediary transformation eliminates the impact of process spread on measurement consistency, as the comparator's hysteresis provides noise immunity and stable switching thresholds
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 achieves high sensitivity and resolution with reduced power consumption, enabling accurate temperature measurement without external converters, suitable for wearable applications with improved immunity to noise and cost-effectiveness.
Implementation Method 1
a reverse biased diode a junction temperature of which is to be sensed... charged by a reverse saturation current flowing throughout said reverse biased diode
Data Source
AI summary
A temperature sensor, including a conduction path, between a line at a supply voltage and a common ground terminal of the temperature sensor, including a capacitor, a resistor and a reverse biased diode a junction temperature of which is to be sensed; a digital circuit coupled with the capacitor, the resistor and the diode, configured to compare a charge voltage of the capacitor with an upper threshold voltage and with a lower threshold voltage, and to generate in operation an output sense signal that switches to a first logic level when the charge voltage attains the lower threshold voltage and to a second logic level when the charge voltage attains the upper threshold voltage, the digital circuit being configured to connect the resistor electrically in parallel with the capacitor to discharge the capacitor when the output sense signal is at the second logic level, and to connect the capacitor so as to be charged by a reverse saturation current flowing throughout the reverse biased diode when the output sense signal is at the first logic level.