Fault Detection Circuit for NTC Leakage and Open-Short Diagnostics
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Solution Overview
Problem
Existing fault detection methods in electrical circuits, particularly in safety-critical battery-powered applications, fail to accurately detect leakage currents due to inherent variability in negative temperature coefficient (NTC) resistors, leading to inaccurate measurements and potential interference with circuit operation.
Innovation Solution
A fault detection circuit comprising switches, resistors, and a current source that decouples resistors from a reference potential, allowing voltage measurement at a voltage node to determine fault conditions, with features including a thermistor and a second resistor sharing a common voltage node for diagnostic measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fault detection methods are used with NTC resistors, then the circuit can operate continuously, but measurement precision deteriorates due to leakage currents and manufacturing tolerance variability
Solution Approach 1:
The patent extracts the fault detection function from the continuous operation mode by introducing a diagnostic mode that temporarily decouples resistors from the reference potential. This separation allows independent measurement of leakage currents without interfering with normal circuit operation, thereby improving measurement precision while maintaining overall system reliability.
Solution Approach 2:
The patent introduces switches as intermediary components that control the coupling and decoupling of resistors from the reference potential. These switches act as mediators between the measurement circuit and the rest of the system, enabling accurate fault detection by isolating the measurement path from leakage current paths during diagnostic measurements.
2Measurement precision
If cross-point switches and complex circuitry are used to eliminate current leakage, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes existing circuit components multi-functional by enabling them to operate in both normal measurement mode and diagnostic mode. The same resistors, switches, and measurement circuitry used for continuous operation are also used for fault detection, eliminating the need for separate complex leakage detection circuits and reducing overall device complexity.
Solution Approach 2:
The patent enables the measurement circuit to perform self-diagnostics by using its own components (resistors, switches, current source) to detect faults within itself. The diagnostic mode allows the circuit to measure its own leakage currents and detect open/short conditions without requiring external complex testing equipment or additional dedicated test circuitry.
3Reliability
If resistors remain coupled to reference potential during measurement, then circuit operation is maintained, but fault detection capability deteriorates due to undetected leakage currents
Solution Approach 1:
The patent implements periodic switching between normal operation mode and diagnostic mode. During periodic diagnostic intervals, switches decouple resistors from the reference potential to enable leakage current measurement, then return to normal operation mode. This periodic action ensures continuous circuit operation while regularly detecting faults that would otherwise remain undetected.
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
Enables real-time detection of open and short circuit conditions, as well as leakage currents, by accurately measuring voltage changes, thereby improving the reliability and accuracy of fault identification in multi-channel circuits.
Implementation Method 1
measuring the voltage at the voltage node allows to determine the presence of a fault condition
Implementation Method 2
a measurement circuit that comprises sensors that rely on current flowing through a negative temperature coefficient (NTC) resistor, i.e., a circuit element having a temperature-dependent electrical resistance
Data Source
AI summary
Described herein are systems and methods for real-time fault detection in electrical circuits. Various embodiments provide a fault detection circuit that uses a resistor network that is controlled to detect an internal current leak in multiple directions, e.g., to ground or to a power supply. The magnitude of the leakage current may be estimated from voltage measurements at voltage pins. In addition, as part of circuit diagnostics, open and short circuit fault conditions may be identified by using current sources and measuring deflections at the voltage pins.