Power MOSFET Overheat Detection Using an RC Thermal Model
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Solution Overview
Problem
Existing semiconductor devices for power management, such as those used in automobiles, face challenges in accurately detecting overheating due to insufficient precision in temperature detection methods, particularly in first-order and second-order approximations, and reliance on diodes for overtemperature detection.
Innovation Solution
A semiconductor device incorporating a current generation circuit, a temperature sensor, and a resistor-capacitor network that models thermal resistance and capacitance between the transistor and the temperature sensor, enhancing overheating detection accuracy by incorporating a Cauer or Foster equivalent circuit to account for heat transfer dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If first-order or second-order approximation methods are used for temperature detection, then the detection process is simple, but the temperature detection accuracy is insufficient
Solution Approach 1:
The patent introduces an RC network as an intermediary element between the temperature sensor and the detection circuit. This network models the thermal characteristics (thermal resistance and thermal capacitance) of the physical system, allowing the electrical circuit to accurately represent thermal behavior without requiring complex calculation algorithms. The RC network acts as a mediator that transforms the thermal measurement problem into an equivalent electrical measurement problem that can be solved with simple voltage detection.
Solution Approach 2:
The patent replaces the mechanical/mathematical approximation methods (first-order and second-order calculations) with an equivalent electrical circuit model. By substituting the thermal system with an analogous electrical RC circuit, the patent achieves accurate temperature detection through simple voltage measurement rather than complex computational approximation, effectively replacing mathematical mechanics with electrical analogies.
2Measurement precision
If diodes are used for overtemperature detection, then the device structure is simple, but the detection accuracy is not high
Solution Approach 1:
The patent uses the RC network as an intermediary that captures the dynamic thermal behavior between the power MOSFET and the temperature sensor. This intermediary circuit element allows the system to account for thermal mass and thermal resistance effects, providing accurate detection of overtemperature conditions without requiring multiple diodes or complex sensor arrays. The RC network mediates between the physical thermal system and the electrical detection circuit.
3Measurement precision
If the temperature sensor is placed close to the power MOSFET to improve detection accuracy, then thermal interference increases
Solution Approach 1:
The RC network serves as a thermal model intermediary that allows the temperature sensor to be positioned optimally without direct thermal contact with the power MOSFET. By modeling the thermal path through equivalent electrical components, the system can accurately represent thermal conditions even when the sensor is physically separated from the heat-generating device, thus reducing thermal interference while maintaining detection accuracy.
Solution Approach 2:
The patent replaces the direct physical thermal coupling (mechanical thermal contact) with an electrical analog model. Instead of relying on direct thermal conduction between the MOSFET and sensor, the system uses an RC circuit to model the thermal relationship, substituting physical thermal interaction with electrical signal processing that replicates thermal behavior.
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 configuration allows for high-accuracy overheating detection, preventing thermal destruction of power MOSFETs while minimizing performance degradation and chip area increase, effectively addressing the limitations of prior art in temperature detection precision.
Implementation Method 1
a resistor-capacitor network coupled between the current generation circuit and the temperature sensor... the resistor-capacitor network comprises a resistor and a capacitor corresponding to a thermal resistance and a thermal capacitance between the first transistor and the temperature sensor
Implementation Method 2
the resistor-capacitor network comprises a resistor and a capacitor corresponding to a thermal resistance and a thermal capacitance between the first transistor and the temperature sensor
Data Source
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AI summary
A semiconductor device includes a first transistor that flows a current to a load, a current generation circuit that outputs a current corresponding to a power consumption of the first transistor, a temperature sensor, a resistor-capacitor network coupled between the current generation circuit and the temperature sensor and an overheat detection circuit coupled to a connection point of the current generation circuit and the resistor-capacitor network, wherein the resistor-capacitor network comprises a resistor and a capacitor corresponding to a thermal resistance and a thermal capacitance between the first transistor and the temperature sensor.