Floating Capacitor Battery Leakage Current Sensing Circuit
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Solution Overview
Problem
Existing battery power supply systems, particularly in electric vehicles, face challenges in accurately detecting leakage currents, which can lead to unexpected discharge, malfunctions, and potential electric shocks due to poor insulation, necessitating a simple and effective sensing method.
Innovation Solution
A battery leakage current sensing apparatus using a floating capacitor to detect voltage variations between terminals, with a DC voltage applying unit, terminal selection switching, charge switching, voltage sensing, and a leakage current determining unit to calculate resistance and compare it against a criterion, providing early detection and alarming capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a leakage current sensing circuit is implemented in a battery power supply system, then leakage current detection capability is improved, but device complexity increases
Solution Approach 1:
The sensing circuit is divided into modular functional units: a floating capacitor for voltage sampling, a voltage sensing unit for detection, and a determining unit for analysis. This segmentation allows each component to perform a specific function, simplifying the overall circuit design while maintaining detection accuracy.
Solution Approach 2:
A floating capacitor is introduced as an intermediary element to sample the battery terminal voltage. The capacitor isolates the sensing circuit from direct connection to the high-voltage battery terminals, enabling safe and accurate voltage detection without requiring complex high-voltage handling circuitry.
2Reliability
If the floating capacitor remains connected to the voltage detection path during sensing, then continuous monitoring is improved, but noise interference increases
Solution Approach 1:
The voltage sensing unit operates periodically by sequentially connecting to different battery terminals through switching elements. During each sensing interval, the floating capacitor is disconnected from the detection path, eliminating noise interference while maintaining continuous monitoring capability through rapid sequential measurements.
Solution Approach 2:
The floating capacitor pre-charges to the battery terminal voltage before sensing operations. This preliminary charging allows the capacitor to store the voltage information, enabling the sensing circuit to measure the voltage after disconnection without being affected by noise from the detection path.
3Measurement precision
If DC voltage is applied to the anode terminal during anode voltage detection, then detection accuracy is improved, but energy consumption increases
Solution Approach 1:
DC voltage is applied to the anode terminal only during the specific time interval when anode voltage detection is performed. The voltage application is periodic and synchronized with the sensing cycle, allowing accurate detection while minimizing energy consumption by keeping the voltage off during other operations.
Solution Approach 2:
The DC voltage application is dynamically controlled based on the detection requirements. The voltage is switched on only when needed for anode detection and switched off otherwise, creating a dynamic energy consumption pattern that balances detection accuracy with energy efficiency.
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 enables accurate and early detection of leakage currents, preventing battery discharge, protecting against device malfunctions and human injury, while minimizing noise interference for improved detection accuracy.
Implementation Method 1
a floating capacitor for storing a detection voltage of one of the cathode and anode terminals
Implementation Method 2
a voltage sensing unit for sensing the detection voltage of the cathode or anode terminal, charged to the separated floating capacitor
Implementation Method 3
a leakage current determining unit for calculating a leakage resistance based on the detection voltages of the cathode and anode terminals of the battery, sensed by the voltage sensing unit, and then comparing the calculated leakage resistance with a criterion insulation resistance
Data Source
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AI summary
An apparatus for sensing a leakage current of a battery includes a floating capacitor charged with a voltage detected from a cathode or anode terminal of a battery; a DC voltage applying unit for applying a DC voltage to the anode terminal when measuring a detection voltage of the anode terminal; a terminal selection switching unit for selecting a voltage detection path for the cathode or anode terminal; a charge switching unit for charging the floating capacitor with the detection voltage detected from the selected voltage detection path, and separating the floating capacitor from the voltage detection path; a voltage sensing unit for sensing the detection voltage charged to the floating capacitor; and a leakage current determining unit for calculating a leakage resistance based on the detection voltages, and comparing the leakage resistance with a criterion insulation resistance to determine whether a leakage current occurs.