Power Transistor Junction Temperature Estimation
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Solution Overview
Problem
Existing temperature detection methods for power transistors in inverters face challenges in achieving high accuracy due to manufacturing variations and distance-related estimation errors, leading to increased costs and thermal design margins.
Innovation Solution
A power conversion device that estimates junction temperature using correlation information between inter-terminal voltage and current, stored in a memory unit, allowing for precise temperature estimation without additional parts or processes, thereby reducing costs and thermal design margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature detecting diode is integrated on the power transistor chip, then temperature detection is achieved, but manufacturing variation is large which disturbs getting good estimated accuracy of junction temperature
Solution Approach 1:
The patent uses the power transistor's own electrical characteristics (on-resistance and forward voltage) as natural temperature sensors instead of adding separate temperature detecting diodes. By copying the temperature sensitivity property from dedicated temperature sensors to the power transistor itself, the method avoids manufacturing variations of additional components while achieving accurate junction temperature estimation through electrical parameter measurements.
Solution Approach 2:
The power transistor serves its own temperature detection function by utilizing its inherent electrical characteristics that change with temperature. The on-resistance and forward voltage of the power transistor itself are used as temperature indicators, eliminating the need for separate temperature detecting diodes and their associated manufacturing variations. This self-service approach directly improves measurement precision by using the device's own properties.
2Measurement precision
If a thermister is mounted outside the chip, then temperature detection is achieved, but there is a distance between the thermister and the power transistor which disturbs getting good estimation accuracy of junction temperature
Solution Approach 1:
Instead of using a physically separate thermister that requires mounting distance, the patent copies the temperature sensing function directly into the power transistor's electrical characteristics. The on-resistance and forward voltage measurements are taken directly from the power transistor terminals, eliminating any physical distance between the sensor and the heat source, thereby achieving accurate junction temperature estimation.
Solution Approach 2:
The patent uses electrical measurements (on-resistance and forward voltage) as intermediaries to indirectly measure the junction temperature without physical contact or distance. These electrical parameters serve as mediators that translate thermal state into measurable electrical signals, allowing temperature estimation without the distance problems associated with external thermistors.
3Measurement precision
If additional temperature detecting circuits or parts are added to improve temperature detection accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the power transistor multi-functional by having it perform both its primary power switching function and temperature sensing function simultaneously. The same power transistor that handles power conversion also provides temperature information through its on-resistance and forward voltage characteristics, eliminating the need for separate temperature detecting circuits and reducing overall device complexity while maintaining measurement precision.
Solution Approach 2:
The patent merges the temperature detection function with the power transistor's existing electrical characteristics. Instead of combining separate temperature detecting diodes or thermistors with the power transistor, the method integrates temperature sensing capability directly into the power transistor's operational parameters, combining multiple functions into a single component and reducing system complexity.
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 high-precision junction temperature estimation, reducing thermal design margins and costs by utilizing electrical characteristics directly from the power transistor, improving accuracy and efficiency.
Implementation Method 1
the control device previously holds correlation information between an inter-terminal voltage Vds and an inter-terminal current Ids... the control device estimates a junction temperature TJ
Data Source
Figure 1
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Figure 3A~3B
AI summary
There is to provide a power conversion device capable of estimating a junction temperature of a power transistor at a high accuracy. The control device includes a temperature estimation unit and controls the on and off of the power transistor through a driver. The voltage detection circuit detects the inter-terminal voltage of a source and drain terminals during the on-period of the power transistor. The temperature estimation unit previously holds the correlation information between the inter-terminal voltage and inter-terminal current of the source and drain terminals and the junction temperature, and estimates the junction temperature, based on the inter-terminal voltage detected by the voltage detection circuit, the known inter-terminal current, and the correlation information.