Thermopile Temperature Sensing for Accurate Skin and Ambient Estimation

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Solution Overview

Problem

Existing temperature sensing systems in electronic devices face challenges in accurately measuring internal and external temperatures due to interference from thermal aggressors and space constraints, leading to inaccuracies and drift in temperature estimates.

Innovation Solution

The integration of thermopile temperature sensors and multiple absolute temperature sensors within electronic devices, allowing for temperature differential measurements to estimate internal and external temperatures, while minimizing the impact of thermal aggressors and reducing space requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple absolute temperature sensors are integrated within electronic devices to measure internal and external temperatures, then temperature estimation accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvetemperature estimation accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent divides the temperature sensing function into multiple segments by using separate absolute temperature sensors positioned at different locations (e.g., on PCBs at different positions) to measure temperatures at different points. This segmentation allows the system to estimate both internal and external temperatures using multiple measurement points, improving overall temperature estimation accuracy while maintaining manageable complexity through modular sensor placement

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces thermal resistance values as an intermediary parameter that relates temperature measurements from multiple sensors to estimate temperatures at locations where direct measurement is difficult. By using thermal resistance models as intermediaries between sensor readings and target temperature values, the system achieves accurate temperature estimation without requiring direct sensor contact with all measurement points, thus reducing the complexity increase

Inventive Principle:

Principle #24Intermediary (Mediator)

2Volume of moving object

If thermopile temperature sensors are embedded within rigid PCBs or FPCs to measure temperature differentials, then space requirements are reduced, but measurement precision may be affected by thermal interference from the embedding structure

Engineering Contradiction:

Improvespace requirementsVSAvoidtemperature differential measurement accuracy

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by positioning thermopile sensors at specific locations on PCBs where they can measure temperature differentials relevant to the device's thermal characteristics. The sensors are strategically placed to measure differentials across components or structures of interest, allowing accurate local temperature gradient measurements while the embedding structure provides mechanical support and electrical connectivity without significantly interfering with the measurement function

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent replaces direct mechanical temperature sensing contact with an electrical measurement approach using thermopiles that convert temperature differentials into voltage signals. This substitution allows temperature differential measurement through the PCB or FPC structure without requiring direct thermal contact with the target locations, reducing the impact of thermal interference from the embedding structure while maintaining compact integration

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach enhances temperature estimation accuracy by reducing the influence of thermal aggressors and space constraints, enabling continuous and precise measurement of ambient and body temperatures, even under varying conditions.

Implementation Method 1

A temperature differential measurement (temperature gradient measurement) of the thermopile temperature sensor can be used for inferring heat flux (e.g., through the electronic device)

Methodology Applied

Scientific EffectThermopile: Thermopile

Implementation Method 2

one or more absolute temperature sensors within the electronic device can be disposed on or otherwise integrated with one or more printed circuit board (PCB)

Methodology Applied

Scientific EffectTemperature sensing:

Data Source

PatentUS12474223B2Temperature sensing systems and methods including multiple temperature sensors

Publication Date: 2025.11.18 APPLE INC

AI summary

Robust estimation of temperatures inside and outside a device can be achieved using one or more absolute temperature sensors optionally in conjunction with thermopile heat flux sensors. Thermopile temperature sensing systems can measure a temperature gradient across two locations within the device, to estimate absolute temperature at locations that are impractical to measure using absolute temperature sensors. Using heat flux models associated with the device, the thermopile temperature sensing system can be used to estimate temperature associated with objects that contact an outer surface of the device, such as a user's skin temperature. Additionally, the thermopile temperature sensing system can be used to estimate ambient air temperature. Within a device, temperature measurements from the thermopile temperature sensors can be used to compensate sensor measurements, such as when the accuracy or reliability of a sensor varies with temperature.