Voltage Threshold Detection Circuit Resilient to MOSFET Vth Shift
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Solution Overview
Problem
Conventional voltage change detection devices fail to accurately detect power supply voltage changes due to deviations in threshold voltages of field effect transistors, leading to malfunctions in voltage detection target circuits, as the detection potential deviates beyond desired limits, either stopping operation when power is available or providing insufficient voltage.
Innovation Solution
A voltage change detection device comprising a reference potential generator, a comparison potential generator, and a detection signal generator, utilizing constant current sources or resistors connected to field effect transistors, ensures that the detection potential remains within desired limits by adjusting the reference and comparison potentials in response to threshold voltage deviations, thereby reducing deviations and maintaining accurate voltage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage change detection devices use field effect transistors to generate reference and comparison potentials, then the detection function is provided, but the detection potential deviates beyond desired limits due to threshold voltage variations
Solution Approach 1:
The patent changes the configuration parameters of the voltage generation circuit by replacing the conventional single field effect transistor with a composite structure involving constant current sources and resistors. This parameter change in the circuit topology makes the reference and comparison potentials independent of field effect transistor threshold voltages, thereby resolving the detection potential deviation issue while maintaining detection accuracy and circuit reliability
Solution Approach 2:
The patent introduces constant current sources and resistors as intermediary elements between the power supply and the potential generation nodes. These intermediary components serve as mediators that decouple the reference and comparison potentials from direct dependence on field effect transistor characteristics, allowing accurate voltage detection without threshold voltage interference
2Reliability
If the detection potential deviates due to threshold voltage variations, then the circuit may stop operation when power is available or provide insufficient voltage, but using conventional designs provides a simple detection structure
Solution Approach 1:
By changing the circuit parameters from direct field effect transistor-based potential generation to constant current source and resistor-based generation, the patent improves circuit operation reliability. The constant current sources ensure stable current flow regardless of voltage variations, and the resistors provide precise voltage division, together eliminating detection failures while maintaining reasonable structural complexity
3Measurement precision
If conventional voltage detection circuits are used, then the circuit size and current consumption are larger, but the detection accuracy is compromised due to threshold voltage deviations
Solution Approach 1:
The patent changes the operational parameters of the detection circuit by using constant current sources that consume fixed, predictable current regardless of voltage fluctuations. This parameter change in the power supply mode ensures accurate detection potential generation while stabilizing current consumption, avoiding the excessive current draw of conventional designs that compensate for threshold voltage variations
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 device effectively reduces detection potential deviations and ensures voltage changes are detected within desired limits, preventing malfunctions and ensuring proper circuit operation even with threshold voltage deviations, while also reducing current consumption and circuit size.
Implementation Method 1
a first field effect transistor having a drain connected to the power supply potential, a source connected to the first constant current source or the first resistor at a first node, and a gate connected to a fixed voltage
Implementation Method 2
a second field effect transistor having a drain and a gate connected to the power supply potential and a source connected to the second constant current source or the second resistor at a second node
Implementation Method 3
a detection signal generator that generates a detection signal indicating that the power supply potential has changed to cross a predetermined detection potential according to a comparison between the reference potential and the comparison potential
Data Source
AI summary
A voltage change detection device is provided, which can reduce a deviation of a detection potential and can detect a voltage change within a predetermined detection potential even when the threshold voltage of a field effect transistor is deviated. The voltage change detection device includes a first field effect transistor, a second field effect transistor, and a detection signal generator. The first field effect transistor has a drain connected to a power supply potential, a source connected to a first constant current source or a first resistor at a first node, and a gate connected to a fixed voltage. The second field effect transistor has a drain and a gate connected to the power supply potential and a source connected to a second constant current source or a second resistor at a second node. The detection signal generator generates a detection signal indicating that the power supply potential has crossed a predetermined detection potential according to a comparison between a voltage at the first node and a voltage at the second node.