Disconnection Detection via Capacitor Voltage Ratio
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Solution Overview
Problem
Conventional disconnection detecting devices for series-connected unit cells in hybrid vehicles require additional components like bypass resistors, leading to increased complexity and potential false detection due to resistance variations, affecting accurate voltage measurement and disconnection detection.
Innovation Solution
A disconnection detecting device using resistors, switching elements, and capacitors to measure voltage changes across capacitors before and after switching, allowing for accurate detection of electric path disconnections by comparing voltage ratios within specific time frames and threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bypass resistor is arranged parallel to the unit cell for disconnection detection, then disconnection detection capability is improved, but the number of electric components increases
Solution Approach 1:
The patent combines the disconnection detection function with the existing noise filter resistor by connecting the capacitor to the node between the noise filter resistor and the unit cell. This merging eliminates the need for a separate bypass resistor while maintaining disconnection detection capability, as the same resistor serves dual purposes: filtering noise and enabling disconnection detection through capacitor voltage measurement.
Solution Approach 2:
The noise filter resistor is given multiple functions: it continues to serve as a noise filter for accurate voltage measurement and simultaneously acts as a bypass resistor for disconnection detection. The capacitor connected to its node enables the resistor to perform dual functions without requiring additional components, achieving multi-functionality in the existing circuit structure.
2Measurement precision
If the resistance value of the bypass resistor or noise filter resistor is varied, then disconnection detection sensitivity is improved, but measurement accuracy deteriorates due to false detection
Solution Approach 1:
The patent changes the parameter from resistor resistance value to capacitor capacitance value and measurement timing. Instead of varying resistance to improve detection sensitivity, the invention uses a capacitor with specific capacitance (0.1μF to 10μF) and controls the timing of voltage measurement after switching element activation. This parameter change allows sensitivity adjustment without affecting the original resistor values, thus avoiding false detection in voltage measurements.
Solution Approach 2:
The patent replaces the resistance-based detection mechanism with a capacitance-based mechanism. The disconnection detection is achieved by measuring the voltage across the capacitor after switching elements are activated, rather than by varying resistor values. This substitution of the detection mechanism allows for improved sensitivity through capacitance and timing control while maintaining measurement accuracy.
3Reliability
If additional bypass resistors are added for each unit cell, then disconnection detection coverage is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the disconnection detection function with existing circuit components (noise filter resistors and switching elements) rather than adding separate bypass resistors for each unit cell. By utilizing the node between the noise filter resistor and unit cell, the invention achieves full disconnection detection coverage across all unit cells without increasing component count or manufacturing complexity.
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 reduces the number of components needed and minimizes false detection by accurately distinguishing between normal and disconnected states, enhancing the reliability of voltage measurement and disconnection detection in hybrid vehicle batteries.
Implementation Method 1
a capacitor connected in parallel to the unit cell and the switching element via the resistor; a switch control device for turning on the switching element to discharge the capacitor
Implementation Method 2
a disconnection detecting device using resistors, switching elements, and capacitors to measure voltage changes across capacitors before and after switching
Data Source
AI summary
A control circuit turns on a switching element to discharge a capacitor, and after a voltage between both ends of the capacitor becomes zero, the control circuit turns off the switching element. The control circuit measures the voltage V1, V2 between both ends of the capacitor after the first predetermined time is passed and after the second predetermined time is passed, and calculate a change rate (V1/V2). If V1/V2 is equal to or less than 0.5, the disconnection is detected.