Battery Contactor Diagnostic via Parallel Reference Circuit
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Solution Overview
Problem
Existing battery systems face challenges in diagnosing the state of high-voltage contactors due to sensitivity to voltage cross-couplings and impedance changes, leading to delayed and unreliable diagnosis of sticking or malfunctioning contactors, which is critical for safety in applications like hybrid and electric vehicles.
Innovation Solution
A diagnostic system with a monitoring circuit that includes a first branch with the contactor and a second parallel branch with a reference voltage source, allowing for the evaluation of diagnostic currents to determine the functional state of contactors, enabling robust and rapid diagnosis with minimal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurements are used to diagnose contactor state, then diagnosis can be implemented, but the system becomes sensitive to voltage cross-couplings and impedance changes leading to unreliable diagnosis
Solution Approach 1:
The patent introduces a monitoring circuit as an intermediary measurement path that includes a known impedance element and a reference voltage source. This intermediary circuit measures contactor state through diagnostic current rather than directly measuring voltage at the contactor terminals, thereby isolating the measurement from voltage cross-couplings and impedance changes in the main power circuit.
Solution Approach 2:
The monitoring circuit creates a simplified copy of the contactor measurement path with known parameters. Instead of measuring the complex high-voltage contactor circuit directly, the system creates a parallel monitoring path with a known impedance element and reference voltage, making the measurement immune to disturbances in the original circuit.
2Reliability
If traditional diagnostic methods are used, then contactor state can be monitored, but diagnosis is delayed due to switching frequency requirements and transient recovery processes
Solution Approach 1:
The monitoring circuit is continuously active and ready to measure contactor state at any time, rather than waiting for specific switching events or transient recovery periods. The circuit maintains a continuous diagnostic current path that can immediately detect contactor state changes without requiring preliminary switching actions or waiting for transient processes to settle.
Solution Approach 2:
The monitoring circuit provides continuous contactor state monitoring by maintaining an always-active measurement path. The diagnostic current flows continuously through the monitoring circuit regardless of the contactor's operational state, enabling real-time detection without interruption or delay for switching cycles.
3Measurement precision
If complex diagnostic circuits with multiple switching operations are used, then comprehensive diagnosis can be achieved, but device complexity increases
Solution Approach 1:
The patent extracts the diagnostic function from the main power circuit by creating a separate, independent monitoring circuit. This extracted monitoring path contains only the essential components (monitoring circuit, known impedance element, reference voltage source) needed for diagnosis, eliminating the need for complex switching operations and multiple measurement paths required by traditional methods.
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
The solution provides a cost-effective and resource-efficient method for continuous monitoring and rapid diagnosis of contactor states, reducing the risk of safety-related issues by accurately detecting open or closed states and potential malfunctions, thus enhancing the reliability of battery systems in vehicles.
Implementation Method 1
a voltage source (154, 164) for generating a reference voltage (UR1, UR2) is connected in the second branch (152, 162)
Implementation Method 2
The diagnostic device (70) is designed to evaluate a diagnostic current (ID1, ID2) which is dependent on the reference voltage (UR1, UR2) and flows in the monitoring circuit (150, 160)
Data Source
AI summary
A battery system comprises a battery including a plurality of battery cells and can be connected on an input side to a direct voltage intermediate circuit via at least one contactor, and a diagnostic device configured to diagnose a state of the at least one contactor. The battery system includes a monitoring circuit with a first branch in which the at least one contactor is arranged, and a second branch which is connected parallel thereto and in which a voltage source configured to generate a reference voltage is connected. The diagnostic device is arranged so as to evaluate a diagnostic current which is dependent on the reference voltage and flows in the monitoring circuit, and serves to determine a fault state of the at least one contactor based on a measured current value or a current profile of the diagnostic current.