Negative Contactor Status Detection Using Constant Current Injection
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Solution Overview
Problem
Conventional high voltage battery management systems for electric and hybrid vehicles face challenges in accurately and cost-effectively determining the status of negative contactors due to high voltage interference and the need for numerous expensive isolation components, leading to potential inaccuracies and increased complexity.
Innovation Solution
A battery control module that applies a constant current through a bipolar transistor and diode to a negative contactor, using resistors and an analog-to-digital converter to determine the resistance across the contactor, thereby simplifying the detection process without additional hardware or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high voltage battery management systems use optical photomos or digital isolators to transport signals from high voltage side to low voltage side, then signal isolation and safety are improved, but system complexity and cost increase significantly due to requiring 14 isolation components
Solution Approach 1:
The patent extracts the signal measurement function from the high voltage side and performs it directly on the low voltage side using the battery control module's existing ADC and processing resources. This eliminates the need for multiple isolation components while maintaining safety, as the measurement is performed where the control logic already resides.
Solution Approach 2:
The battery control module is designed to perform multiple functions including negative contactor status detection, battery monitoring, and control operations. By making the control module multi-functional, the patent eliminates the need for separate isolation components dedicated solely to contactor status signal transmission.
2Measurement precision
If voltage drop measurement method is used to determine negative contactor status, then contact resistance measurement is achieved, but measurement accuracy deteriorates at low load currents due to difficult-to-measure small voltage drops
Solution Approach 1:
The patent applies preliminary action by proactively driving the negative contactor with a known current from the battery control module before measurement. This active driving ensures sufficient current flow to generate measurable voltage drops, eliminating the reliability issues associated with passive low-current measurements.
Solution Approach 2:
The patent changes the measurement parameter from passive voltage drop detection to active current-driven measurement. By controlling the current through the contactor and measuring the resulting voltage, the system achieves accurate measurements across all current conditions, not just high current scenarios.
3Ease of operation
If voltage injection method is used to determine contactor status, then status detection is achieved, but measurement accuracy deteriorates and additional protection components are required due to high voltage sourcing from HV Battery Pack
Solution Approach 1:
The patent uses the battery control module as an intermediary between the low voltage control logic and the high voltage contactor. The control module safely interfaces with the contactor using its internal protection circuits and measurement capabilities, eliminating the need for external high-voltage injection and associated protection components.
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 method provides a cost-effective and accurate means to determine the negative contactor status in high voltage battery systems, reducing complexity and the need for expensive components while improving measurement accuracy.
Implementation Method 1
determining a resistance across the negative contactor of the battery
Implementation Method 2
applying a constant current to a bipolar transistor element... determining a resistance across the negative contactor
Data Source
AI summary
A system, method, and battery control module for detecting negative contactor status of a battery, such as a high voltage vehicle battery, is disclosed. The method includes applying a constant current to a bipolar transistor element having a base, an emitter, and a collector, wherein the base is electrically connected to a first resistor and an analog-to-digital converter, the collector being electrically connected to a second resistor and a diode. A collected current is delivered by the collector, and the method includes injecting the collected current through the second resistor and the diode and into a negative contactor of a battery. The method also includes determining a resistance across the negative contactor of the battery. The system may include a battery having a negative contactor, the negative contactor having a switch side, and a battery control module in communication with the battery.