Insulation Resistance Measuring Circuit for High Voltage Batteries
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Solution Overview
Problem
Existing insulation resistance measurement methods for high voltage batteries in hybrid vehicles are either invasive, causing insulation breakdown during measurement or face design limitations due to currents passing through the same circuit, necessitating a simpler and more precise method.
Innovation Solution
An insulation resistance measuring circuit utilizing a source resistor unit and operational amplifiers to sense and amplify voltages, then subtract a reference voltage, allowing for precise insulation resistance measurement without requiring battery voltage information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC current is forcedly applied to measure insulation resistance, then measurement can be performed, but insulation breakdown occurs during measurement
Solution Approach 1:
The patent introduces a coupling capacitor as an intermediary component between the DC current source and the battery system. The capacitor blocks the DC current from directly passing through the insulation path, preventing insulation breakdown while still enabling measurement of insulation resistance through the charging/discharging current of the capacitor.
Solution Approach 2:
The measurement process utilizes periodic charging and discharging of the coupling capacitor. By applying DC current in periodic cycles and measuring the transient current during capacitor charging, the system achieves insulation resistance measurement without continuous current flow that would cause insulation breakdown.
2Reliability
If coupling capacitor is used to measure insulation resistance with AC signal, then insulation breakdown is avoided, but circuit design is limited due to current passing through same circuit
Solution Approach 1:
The patent segments the measurement circuit into distinct functional blocks: a DC current source unit, a coupling capacitor unit, and a current measurement unit. This segmentation allows the DC current source to be isolated from the measurement circuit, eliminating the constraint that currents must pass through the same circuit while maintaining the benefits of capacitor-based measurement.
Solution Approach 2:
The coupling capacitor serves as an intermediary that decouples the DC current source from the measurement circuit. This intermediary component enables independent design of the current source and measurement circuit, removing the limitation where both must share the same current path.
3Measurement precision
If battery voltage information is required for insulation resistance measurement, then accurate measurement can be achieved, but measurement becomes more complex
Solution Approach 1:
The measurement circuit measures the current flowing through the coupling capacitor and uses this current information alone to calculate insulation resistance. The system serves itself by deriving all necessary measurement data from the capacitor charging current, eliminating the need for external battery voltage information and simplifying the measurement approach.
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
Enables simple and precise measurement of insulation resistance by amplifying sensed voltages and subtracting a reference, effectively addressing the limitations of existing methods and ensuring accurate detection during cathode and anode insulation breakdowns.
Implementation Method 1
capable of more precisely measuring the insulation resistance by amplifying a voltage
Data Source
Figure 1~2
AI summary
Provided is an insulation resistance measuring circuit including: a source resistor unit including a first source resistor connected between a positive terminal of a battery and a second source resistor and the second source resistor connected between a negative terminal of the battery and the first source resistor; a voltage sensing unit sensing a voltage of the first source resistor as a first voltage and sensing a voltage of the second source resistor as a second voltage; and an insulation resistance measuring unit measuring an insulation resistance of the battery through a value obtained by dividing a difference between the first and second voltages by a sum between the first and second voltages.