Leakage Current Detection Using Voltage Dividers in Hybrid Vehicles
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Solution Overview
Problem
Hybrid motor vehicles face challenges in detecting and quantifying leakage currents between isolated high-voltage and low-voltage batteries, which can occur due to physical damage or shorted connections, and existing solutions are either incomplete or overly complex.
Innovation Solution
The method involves using voltage dividers connected across both batteries to measure the center node voltage, comparing the voltages to detect any leakage current, and employing a microcontroller and switches to determine the magnitude of the leakage current, with optional use of optical isolators to minimize power wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an isolation monitor unit is used to detect leakage current between high voltage battery and chassis ground, then detection capability is improved, but device complexity increases significantly
Solution Approach 1:
The system is divided into two separate voltage divider circuits: one connected to the high voltage battery and another to the low voltage battery. Each divider independently measures voltage at its center node, and the microcontroller compares these voltages to detect leakage current. This segmentation avoids the need for a complex isolation monitor unit while maintaining detection capability.
Solution Approach 2:
The patent uses voltage dividers as intermediary components to indirectly detect leakage current. Instead of directly measuring current or using complex isolation monitoring, the system measures voltage at the center nodes of the dividers and infers leakage current from voltage differences. This intermediary approach simplifies the overall system while preserving measurement precision.
2Measurement precision
If voltage dividers are connected continuously across both batteries to enable leakage detection, then detection accuracy is improved, but power consumption increases
Solution Approach 1:
The voltage dividers are not continuously connected but are instead connected periodically or on-demand when leakage current detection is required. The microcontroller can selectively connect the dividers to the batteries only when measurement is needed, reducing continuous power consumption while maintaining measurement accuracy when required.
Solution Approach 2:
The system dynamically connects and disconnects the voltage dividers based on operational requirements. The microcontroller controls the timing and duration of divider connections, adapting the measurement process to actual needs rather than maintaining continuous connections. This dynamic approach balances measurement accuracy with power conservation.
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 effectively detects and quantifies leakage currents between isolated batteries, allowing for corrective action and reducing unnecessary power consumption, while being simpler than existing systems.
Implementation Method 1
connecting voltage dividers across the two sources. The center node voltage of the first voltage divider, connected across a first battery, is measured.
Implementation Method 2
the center nodes of both dividers are connected to each other and the center node voltage of both dividers is measured and compared to the first voltage obtained from the first divider. A difference between the two voltages indicates a leakage current from the second battery to ground.
Data Source
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AI summary
Leakage current between two electrical energy sources in a vehicle, one of which is normally isolated from ground, can be detected and measured by connecting voltage dividers across the two sources. The center node voltage of the first voltage divider, connected across a first battery, is measured. Thereafter, the center nodes of both dividers are connected to each other and the center node voltage of both dividers is measured and compared to the first voltage obtained from the first divider. A difference between the two voltages indicates a leakage current from the second battery to ground.