Overheat Protection Circuit With Extraction Path
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional overheat protection circuits tend to erroneously detect overheated states when a negative current is applied to the output terminal of a monitoring-target power device, leading to malfunctions and low immunity to noise.
Innovation Solution
An overheat protection circuit is designed with an NPN transistor, a power terminal, and an output voltage generator that prevents voltage drops at the collector of the NPN transistor, using a transmission path for the supply voltage that bypasses the current source, and incorporates a voltage divider and operational amplifier to accurately detect temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional overheat protection circuit uses a current source connected to the collector of the NPN transistor, then the circuit can detect temperature changes through the base-emitter voltage, but the circuit becomes vulnerable to negative currents causing voltage drops and erroneous overheated state detection
Solution Approach 1:
The patent extracts the current source from the transmission path of the supply voltage to the collector. By separating the current source function from the voltage transmission path, negative currents applied to the output terminal can no longer cause voltage drops at the collector that would lead to erroneous overheated state detection. The current source is removed from the critical voltage path while temperature detection functionality is preserved through alternative means.
Solution Approach 2:
The patent introduces an intermediary transmission path that directly connects the supply voltage to the collector without passing through the current source. This intermediary path acts as a protective conduit that prevents negative currents from causing voltage drops at the collector, while still allowing the temperature detection mechanism to function through the base-emitter voltage of the NPN transistor.
2Stability of the object's composition
If the supply voltage transmission path includes a current source, then the NPN transistor can operate with stable bias current, but negative currents cause voltage drops leading to malfunction
Solution Approach 1:
The current source is extracted from the supply voltage transmission path to the collector. This removal eliminates the mechanism by which negative currents cause voltage drops, while the NPN transistor maintains stable operation through alternative biasing arrangements that do not involve the current source in the critical voltage path.
Solution Approach 2:
The patent converts the potential harm of negative currents into a benefit by redesigning the transmission path. The harmful effect of negative currents causing voltage drops is eliminated by removing the current source from the path, and the same structural change simultaneously provides the benefit of stable bias current through alternative means, thus turning a vulnerability into a robust design feature.
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 effectively prevents erroneous overheated state detection and enhances immunity to negative currents and noise, ensuring reliable operation even when a negative current is applied to the output terminal.
Implementation Method 1
the temperature response of the base-emitter voltage of an NPN transistor
Data Source
AI summary
An overheat protection circuit has an NPN transistor, a power terminal to which a supply voltage is applied, a transmission path by which the supply voltage is transmitted from the power terminal to the collector of the NPN transistor without passing through a current source, and an output voltage generator that generates an output voltage commensurate with the base-emitter voltage of the NPN transistor.