Battery Precharge Circuit Using a Thermistor Current Limiter
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Solution Overview
Problem
Conventional battery management systems for electric vehicles require a precharge resistor for precharging smoothing capacitors, which occupies valuable space and does not serve any additional purpose during charging/discharging cycles.
Innovation Solution
The system uses a thermistor from a temperature sensing circuit as a current limiter for precharging the smoothing capacitor, eliminating the need for a precharge resistor and optimizing space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precharge resistor is used for precharging the smoothing capacitor, then the precharging function is achieved, but the space utilization is reduced and the device complexity increases
Solution Approach 1:
The thermistor in the temperature sensing circuit is made to serve dual purposes: temperature sensing and precharging current limiting. By utilizing the inherent resistance characteristics of the thermistor during cold conditions, the system eliminates the need for a separate precharge resistor, thereby improving space utilization while maintaining the precharging function.
Solution Approach 2:
The patent combines the temperature sensing function and precharging function into a single component (the thermistor). The thermistor's resistance at low temperatures naturally limits the precharge current, merging two previously separate functions into one integrated solution, reducing device complexity and space requirements.
2Reliability
If a precharge resistor is used for precharging the smoothing capacitor, then the precharging function is achieved, but the device complexity increases
Solution Approach 1:
The thermistor is designed to perform multiple functions: temperature sensing and precharging current limiting. This multi-functionality reduces the total number of components in the battery management system, simplifying the overall device structure while ensuring reliable precharging operation.
Solution Approach 2:
The patent merges the temperature sensing circuit and precharging circuit into a single integrated solution using the thermistor. By combining these functions, the system reduces component count and interconnections, thereby lowering device complexity and potential failure points.
3Reliability
If a precharge resistor is used, then the precharging function is achieved, but the component redundancy increases
Solution Approach 1:
The thermistor serves as both a temperature sensor and a precharge current limiter, eliminating the need for redundant components. This approach reduces the component count in the battery management system while maintaining all necessary functions, including precharging and temperature monitoring.
Solution Approach 2:
The patent extracts the precharging function from the temperature sensing circuit's auxiliary role and makes it a primary function of the thermistor itself. By doing so, the system removes the need for separate precharge resistors and related control circuitry, reducing overall component quantity.
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 allows for effective precharging of smoothing capacitors using the thermistor as a current limiter, reducing the need for additional components and enhancing space efficiency in the battery management system.
Implementation Method 1
a current flowing through the precharge power line toward the second terminal of the thermistor
Implementation Method 2
a temperature sensing circuit including a thermistor
Data Source
AI summary
A battery management system according to the present disclosure is for a battery connected in parallel to a smoothing capacitor through a high side power line and a low side power line. The battery management system includes a discharge control switch connected between a first node and a second node of the low side power line, a temperature sensing circuit including a thermistor, wherein a first terminal of the thermistor is connected to the first node, a precharge switch connected to a precharge power line between a second terminal of the thermistor to the second node, and a control unit. The control unit is configured to turn off the discharge control switch and turn on the precharge switch, for precharging of the smoothing capacitor, when the control unit receives a key-on signal.