Overheat Protection Circuit for Accurate Low-Power Temperature Detection
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Solution Overview
Problem
Conventional overheat protection circuits in ICs suffer from reduced accuracy in overheat detection due to voltage drops in thermosensitive elements during intermittent operation, leading to erroneous detection of overheat states even when the IC is not in an overheat condition.
Innovation Solution
An overheat protection circuit is designed with a first transistor and a first NPN transistor, where the NPN transistor has a temperature coefficient of zero or more, allowing it to switch states based on a reference voltage, improving detection accuracy by filtering noise and preventing erroneous transitions to overheat detection states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If current supply to the thermosensitive element is cut during intermittent operation to suppress power consumption, then power consumption is reduced, but voltage drop causes erroneous overheat detection
Solution Approach 1:
The overheat protection circuit is segmented into multiple functional blocks: a thermosensitive element for temperature detection, a reference voltage generation circuit for providing stable reference, a comparison circuit for accurate temperature judgment, and a control circuit for intermittent operation management. This segmentation allows each block to be optimized independently, maintaining detection accuracy while reducing power consumption during non-critical periods.
Solution Approach 2:
The circuit changes operational parameters dynamically based on system state. During active operation, the thermosensitive element operates at full voltage for accurate detection. During intermittent operation, the circuit transitions to a low-power mode where current to the thermosensitive element is reduced or stopped, but the reference voltage and comparison circuits remain active to maintain detection capability when needed.
2Use of energy by stationary object
If voltage is reduced during intermittent operation to save power, then power consumption decreases, but detection accuracy deteriorates due to voltage drop
Solution Approach 1:
A reference voltage circuit acts as an intermediary between the thermosensitive element and the comparison circuit. This reference voltage provides a stable baseline that compensates for voltage drops during intermittent operation, allowing the comparison circuit to accurately determine temperature thresholds even when operating voltage is reduced, thereby maintaining detection reliability while enabling power savings.
3Loss of energy
If the thermosensitive element operates at low voltage during non-operation, then power consumption is minimized, but false overheat detection occurs
Solution Approach 1:
The comparison circuit continuously monitors the voltage from the thermosensitive element and compares it against a stable reference voltage. This feedback mechanism allows the system to distinguish between legitimate temperature-induced voltage changes and voltage drops caused by reduced operating voltage during intermittent periods, preventing false overheat detection while maintaining low power consumption.
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 enhances the accuracy of overheat detection and reduces power consumption by accurately distinguishing between overheat and non-overheat states, minimizing false alarms and maintaining low current consumption during non-operating states.
Implementation Method 1
the first NPN transistor having a temperature coefficient of zero or more, and being switchable between an on state and an off state in accordance with a voltage level of a reference voltage to be supplied to the base
Data Source
AI summary
Provided is an overheat protection circuit with improved accuracy of overheat detection. The overheat protection circuit includes: an input terminal; an output terminal; a first transistor containing a first terminal, a second terminal, and a control terminal, the first transistor being switchable between ON and OFF; and a first NPN transistor containing a base to be connected to a node between the second terminal of the first transistor and the ground terminal, an emitter to be connected to the ground terminal, and a collector to be supplied with a constant current and connected to the output terminal, the first NPN transistor being switchable between ON and OFF in accordance with a voltage level of a reference voltage to be supplied to the base, the reference voltage having a temperature characteristic of having a temperature coefficient of zero or more.