Semiconductor Device Dynamic Current Limiting for Overheating
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Solution Overview
Problem
Existing load driving devices for semiconductor devices, such as those used in automotive systems, face challenges in maintaining efficient load driving capabilities while preventing overheating, particularly when ambient temperatures fluctuate near the boundary temperature, leading to a sharp decrease in driving capacity.
Innovation Solution
A semiconductor device with a temperature detector that sets detection signals to limit current flowing through an output transistor based on temperature differences and ambient conditions, using a first and second current limiter to adjust current flow and ensure the transistor turns off regardless of external input signals when overheating is detected, and resets when temperatures decrease below reference thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting is applied to prevent overheating of the output transistor, then reliability is improved, but load driving capability deteriorates
Solution Approach 1:
The patent implements dynamic current limiting by adjusting the current limit threshold based on ambient temperature conditions. When ambient temperature is below a reference temperature, current limiting is applied; when ambient temperature exceeds the reference temperature, current limiting is released. This dynamic adjustment resolves the contradiction by adapting the protection level to environmental conditions, maintaining reliability when needed while preserving load driving capability when ambient temperature already prevents overheating.
2Reliability
If current limiting is applied when ambient temperature is near boundary temperature, then reliability is improved, but load driving capability sharply decreases
Solution Approach 1:
The patent changes the operational parameters of the current limiter based on ambient temperature. Specifically, the current limit threshold is dynamically adjusted: when ambient temperature is below the reference temperature, current limiting is active; when ambient temperature exceeds the reference temperature, the current limit threshold is raised to release limiting. This parameter change approach resolves the contradiction by ensuring current limiting is only applied when ambient conditions actually pose a risk, avoiding unnecessary productivity loss at boundary temperatures.
3Stability of the object's composition
If temperature detection with hysteresis is used, then stability is improved, but response time increases
Solution Approach 1:
The patent implements hysteresis by using different temperature thresholds for activating and deactivating current limiting. The activation threshold (first reference temperature) is lower than the deactivation threshold (second reference temperature). This creates a hysteresis band that prevents rapid switching at boundary temperatures, improving stability. The response time increase is acceptable because the hysteresis band is designed to be small, and the overall response remains timely while avoiding oscillation.
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 solution effectively prevents overheating and maintains stable load driving capacity by consistently limiting current flow through the output transistor, ensuring reliable operation across varying ambient temperatures.
Implementation Method 1
a first diode connected in series to the first constant current source and placed in a peripheral circuit region away from the output transistor, a second diode connected in series to the second constant current source and placed in the output transistor or its proximity
Data Source
AI summary
A semiconductor integrated power device including: an output transistor configured to drive an external load element; a temperature detection circuit configured to: output a first detection signal in reference to a temperature difference between a temperature of the output transistor and an ambient temperature; and output a second detection signal in reference to a temperature difference between a temperature of the output transistor and a first reference temperature; and a current limiter circuit configured to limit a current flowing through the output transistor according to the first detection signal and the second detection signal. The temperature detection circuit activates and inactivates the first detection signal or the second detection signal based on an output of a first hysteresis circuit.