Enclosure Surface Temperature Estimation via Thermal Transfer Functions
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Solution Overview
Problem
Existing methods for estimating the surface temperature of electronic device enclosures, such as smartphones and tablets, using temperature sensors on the substrate and subtracting a fixed value from the measured temperature, result in increased errors due to fluctuations in the heat source temperature, and may mar the device's appearance by requiring surface-mounted sensors.
Innovation Solution
A method involving a processor on the substrate that calculates the enclosure surface temperature using transfer functions based on thermal resistance and capacitance between the heat source, the enclosure surface, and the temperature sensor, reflecting the time heat takes to travel between these components, thereby improving accuracy and avoiding surface sensor placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is disposed on the surface of the enclosure, then the surface temperature can be directly detected, but the appearance of the electronic apparatus is marred
Solution Approach 1:
The patent uses an intermediary approach by placing the temperature sensor on the substrate inside the enclosure rather than directly on the surface. The sensor detects substrate temperature, and through thermal transfer function calculations, the enclosure surface temperature is estimated. This mediator (substrate temperature measurement) allows accurate temperature monitoring without compromising the external appearance.
Solution Approach 2:
The patent replaces direct mechanical contact measurement (surface-mounted sensor) with an indirect measurement system. Instead of physically mounting a sensor on the enclosure surface, the system uses internal substrate temperature sensors combined with thermal modeling to calculate surface temperature, substituting a complex mechanical mounting system with a computational approach.
2Device complexity
If a fixed value is subtracted from the measured temperature to estimate surface temperature, then the calculation is simple, but the error increases due to heat source temperature fluctuations
Solution Approach 1:
The patent transitions from a static fixed-value subtraction method to a dynamic calculation approach. The thermal transfer function incorporates real-time substrate temperature measurements and accounts for varying thermal conditions. The calculation adapts to heat source temperature fluctuations by using the actual measured substrate temperature as a variable input, making the system dynamic rather than static.
Solution Approach 2:
The patent changes the parameters used in temperature estimation from a constant fixed value to variable parameters including substrate temperature, thermal resistance, and thermal capacitance. By making these parameters changeable and adaptive based on actual operating conditions, the system maintains accuracy despite heat source fluctuations.
3Shape
If the temperature sensor is disposed on the substrate, then the appearance is preserved, but the error between actual and calculated surface temperature increases
Solution Approach 1:
The patent implements a feedback mechanism where the measured substrate temperature is continuously fed into the thermal transfer function calculation. The system uses this feedback to dynamically adjust the surface temperature estimation, compensating for the indirect measurement approach and maintaining accuracy despite the sensor being located on the substrate rather than the surface.
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 the accuracy of surface temperature estimation by accounting for heat travel time and reduces the risk of damaging the device's appearance by not requiring surface-mounted sensors, leading to improved followability of temperature changes and reduced calculation errors.
Implementation Method 1
a first measured value is acquired from a first temperature sensor disposed on the substrate
Implementation Method 2
a first transfer function based on a first thermal resistance and a first thermal capacitance between a heat source over the substrate and the surface of the enclosure
Data Source
AI summary
A processor disposed over a substrate of an electronic apparatus acquires a first measured value from a temperature sensor disposed on the substrate, and calculates surface temperature of a surface of an enclosure of the electronic apparatus on the basis of a transfer function G(s) based on a first thermal resistance and a first thermal capacitance between a heat source over the substrate and the surface of the enclosure, a transfer function H(s) based on a second thermal resistance and a second thermal capacitance between the heat source and the temperature sensor, and the first measured value.