Shunt Resistor Current Measurement with Switch-Based Fault Checking
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Solution Overview
Problem
Existing current measurement systems for battery charging and discharging paths rely on shunt resistors, which can degrade over time and require additional sensors for reliability, increasing cost and complexity, particularly in safety-critical applications like electric vehicles.
Innovation Solution
A current measuring apparatus that includes a switching circuit, a shunt resistor, a voltage measuring unit, a temperature measuring unit, and a control unit, which determines the state of the shunt resistor by comparing current values calculated from voltage and temperature measurements, eliminating the need for an additional current sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shunt resistor is used for current measurement, then current measurement function is achieved, but reliability deteriorates due to degradation over time and damage from vibration and shock
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the shunt resistor's resistance value and comparing it against reference values. The control unit receives resistance information from the sensing unit and determines whether the shunt resistor is normal or abnormal based on this feedback, enabling real-time reliability assessment and compensation.
Solution Approach 2:
The patent introduces a sensing unit as an intermediary component that indirectly measures the shunt resistor's state by detecting its resistance value. This intermediary approach allows monitoring of the shunt resistor's condition without directly interfering with its operation, enabling reliability assessment through resistance measurement.
2Reliability
If two current sensors are used to compare measurements for reliability, then current measurement reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the shunt resistor serve multiple functions: it acts as both the current sensing element and the object of monitoring. By measuring the shunt resistor's own resistance value, the system achieves self-diagnosis capability, eliminating the need for separate monitoring sensors and reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The shunt resistor effectively monitors its own state through the sensing unit that detects its resistance value. The control unit uses this self-provided information to determine the shunt resistor's normal or abnormal state, enabling the system to service itself without requiring additional external monitoring components.
3Reliability
If two current sensors are used to compare measurements for reliability, then current measurement reliability is improved, but cost increases
Solution Approach 1:
The shunt resistor serves dual purposes: as the current sensing element and as the monitored component. The same shunt resistor provides both the measurement function and the diagnostic information, eliminating the need for additional sensors and reducing component quantity while maintaining reliability.
Solution Approach 2:
The system achieves self-monitoring by using the shunt resistor's inherent resistance property to provide diagnostic information about its own state. This self-service approach eliminates the need for redundant sensors, reducing component quantity and cost while ensuring reliable operation.
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 reliable diagnosis of the shunt resistor's state without additional sensors, improving measurement accuracy and reducing costs by integrating temperature measurements to adjust resistance calculations.
Implementation Method 1
Current measurement using the shunt resistor is based on dividing the voltage across both ends of the shunt resistor by a reference resistance
Implementation Method 2
a voltage measuring unit configured to measure a voltage across the switching circuit
Implementation Method 3
a temperature measuring unit configured to measure a temperature of the switching circuit
Data Source
Figure 1
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AI summary
Disclosed is a current measuring apparatus and method, and a battery pack including the current measuring apparatus. The current measuring apparatus includes: a switching circuit installed on the charging and discharging path; a current measuring unit having a shunt resistor installed on the charging and discharging path and configured to output a current signal corresponding to a voltage across the shunt resistor; a voltage measuring unit configured to measure the voltage across the switching circuit; a temperature measuring unit configured to measure a temperature of the switching circuit; and a control unit. The control unit determines a first current value indicating a current flowing through the shunt resistor, based on the current signal. The control unit determines a second current value indicating a current flowing through the switching circuit, based on the measured voltage and the measured temperature. The control unit determines whether the shunt resistor is in a normal state, based on the first current value and the second current value.