Ground Fault Detection Using Optocoupler and Current Sink
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ground fault detection systems in battery-operated electrical systems, such as those in electric vehicles, are complex and costly due to their reliance on multiple components like voltage dividers and comparators, making them inefficient for manufacturing and operation.
Innovation Solution
A ground fault detection system utilizing an optocoupler and current sink connected in series with a voltage source to the negative terminal of a battery unit, which outputs a logic high signal when any terminal of the battery unit contacts a node at a zero-voltage reference level, such as an electric vehicle's chassis, indicating a ground fault.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex circuits with voltage dividers and comparators are used for ground fault detection, then detection reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the essential detection function from the complex voltage divider and comparator circuitry, isolating only the critical components needed for ground fault detection. By removing unnecessary components and focusing on the core detection mechanism, the system achieves reliable ground fault detection with significantly reduced circuit complexity.
Solution Approach 2:
The simplified circuit design uses universal components that can detect ground faults across different battery configurations and voltage levels. The detection mechanism is designed to be adaptable to various electrical system architectures, making the solution broadly applicable without requiring complex, application-specific circuitry for each scenario.
2Measurement precision
If multiple components like voltage dividers and comparators are used, then detection accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs cost-effective components that can be manufactured at low cost, accepting that individual components may have limited lifespans but are replaced easily. The design uses inexpensive detection elements that maintain sufficient accuracy for ground fault detection while dramatically reducing the bill of materials cost compared to precision comparator-based solutions.
Solution Approach 2:
The detection system achieves accurate ground fault detection by optimizing operational parameters such as current thresholds and timing characteristics rather than relying on expensive high-precision components. By carefully selecting and tuning parameters like the current threshold for LED activation and the response time of the detection circuit, the system achieves reliable detection accuracy with low-cost components.
3Ease of manufacture
If simple circuits are used for ground fault detection, then manufacturing cost is reduced, but detection reliability may worsen
Solution Approach 1:
The patent introduces an optocoupler as an intermediary component that provides electrical isolation between the high-voltage battery system and the low-voltage detection circuitry. This intermediary element enables the use of simple, low-cost detection electronics while maintaining reliable ground fault detection through optical coupling, which inherently provides noise immunity and electrical isolation to ensure detection reliability.
Solution Approach 2:
The patent replaces traditional electrical measurement mechanisms (voltage dividers and comparators) with an optical detection mechanism using an LED and photodetector in the optocoupler. This substitution eliminates the need for complex electrical signal conditioning circuits while providing robust ground fault detection through optical signal generation and detection, achieving both simplicity and reliability.
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 solution provides an efficient and cost-effective method for detecting ground faults, reducing manufacturing costs and improving operational stability by using a simpler circuit configuration that effectively alerts personnel to potential electric shock hazards.
Implementation Method 1
current flows through a light emitting diode, LED, of the optocoupler and activates a transistor of the optocoupler
Data Source
AI summary
The present application describes, among other things, a ground fault detection system. The system includes an optocoupler, a current sink, and a first voltage source connected in series. The first voltage source can connect to a negative terminal of a battery unit. Upon connection between a positive terminal of the battery unit and a first node at a ground zero reference level, current can flow through the optocoupler and the current sink to cause the optocoupler to output a ground fault detection signal.