Transformer Guard Ring Diagnostics for Insulation Leakage Detection
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Solution Overview
Problem
In circuits with transformers, particularly in automotive applications, there is a need to detect leakage currents across insulation barriers between high and low voltage domains, which is critical for safety but challenging due to the existing transformer designs that lack effective diagnostic mechanisms.
Innovation Solution
A circuit and method involving a transformer with a guard ring, where the guard ring is grounded in normal operation and a measurement voltage or current is tapped off at a measurement impedance in a diagnostic mode to detect leakage currents, ensuring the insulation barrier's integrity without impairing its function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer with a guard ring is used to provide an insulation barrier between voltage domains, then the insulation barrier prevents leakage currents, but there is no mechanism to detect whether the insulation barrier is intact
Solution Approach 1:
The guard ring serves dual functions: it provides the insulation barrier during normal operation and serves as the measurement path for detecting insulation failures. The same structural element (guard ring) that prevents leakage currents also enables the detection of insulation barrier integrity through the diagnostic circuit.
Solution Approach 2:
The guard ring is designed to perform multiple functions: electrical insulation during normal operation and leakage current detection during diagnostic mode. This multi-functionality eliminates the need for separate diagnostic structures, maintaining reliability while avoiding additional complexity.
2Measurement precision
If the guard ring is connected to ground potential, then it provides a reference for measurement, but leakage currents cannot be detected
Solution Approach 1:
The connection of the guard ring to ground potential is made dynamic through a switchable connection. In normal operation mode, the guard ring is connected to ground for stable reference. In diagnostic mode, the switch changes the connection state to enable leakage current measurement, allowing the system to adapt its behavior based on operational requirements.
Solution Approach 2:
The diagnostic circuit periodically switches between normal operation mode and diagnostic mode. During periodic diagnostic intervals, the guard ring connection is changed to detect leakage currents, while during normal operation, it maintains ground connection for stable signal transmission. This periodic switching enables both functions without permanent compromise.
3Reliability
If a diagnostic circuit is added to detect leakage currents, then insulation barrier integrity can be monitored, but the circuit complexity increases
Solution Approach 1:
The diagnostic circuit is merged with the existing transformer and guard ring structure. The measurement impedance is integrated into the guard ring path, and the switchable connection combines the normal operation and diagnostic functions in a single integrated circuit architecture, minimizing additional complexity.
Solution Approach 2:
A measurement impedance is introduced as an intermediary element between the guard ring and ground potential. This intermediary enables the detection of leakage currents by creating a measurable voltage drop or current path without significantly altering the overall circuit structure or requiring complex measurement equipment.
4Reliability
If the guard ring is used for signal transmission, then voltage domain isolation is achieved, but leakage current detection interferes with signal transmission
Solution Approach 1:
The operational modes are segmented into distinct time periods: normal operation mode for signal transmission and diagnostic mode for leakage current detection. The switchable connection separates these functions temporally, ensuring that signal transmission and diagnostic measurement do not occur simultaneously, thus avoiding interference while maintaining both functions.
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 approach allows for reliable detection of leakage currents, enhancing safety by maintaining the insulation barrier's integrity and enabling timely diagnostics during product testing, system startup, and regular operation.
Implementation Method 1
Transformers in this case represent one option for transmitting signals between the voltage domains. One specific type of such transformers are what are known as careless transformers in which coils of the transformer are arranged in different metal layers on a substrate
Implementation Method 2
a dielectric between the first coil and the second coil... this insulation, barrier to be intact and for example for no leakage currents to flow across the insulation barrier
Implementation Method 3
tapping off a measurement voltage or a measurement current at a measurement impedance between the guard ring and the ground potential in a diagnostic operating mode in order thereby to be able to detect a leakage current
Data Source
AI summary
A circuit is provided, comprising a transformer having a first coil that is arranged on a substrate and a second coil that is arranged on the substrate above the first coil, and a dielectric between the first coil and the second coil. The circuit furthermore comprises a guard ring around the transformer. The circuit furthermore comprises a diagnostic circuit (55) that is configured so as to ground the guard ring in a normal operating mode and to measure a measurement voltage or a measurement current at a measurement impedance between the guard ring and the ground potential in a diagnostic operating mode.