Parallel MOSFET Fault Diagnosis via MUX Voltage Measurement
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Solution Overview
Problem
Current methods lack an effective way to diagnose abnormality in individual MOSFETs connected in parallel within a secondary battery pack of electric vehicles, leading to potential overheating and safety hazards due to undetected failures.
Innovation Solution
A diagnosis circuit and method utilizing a multiplexer (MUX) to individually assess MOSFETs by connecting at least two MOSFETs in series and parallel, with a switch and microcontroller to control gate voltages and measure voltages at both ends of each MOSFET, determining abnormality by comparing voltage values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple MOSFETs are connected in parallel to increase power capacity, then the power handling capability is improved, but the ability to diagnose individual MOSFET failures is worsened
Solution Approach 1:
The patent divides the parallel MOSFET system into individually addressable units by connecting gates through separate MUX channels. This segmentation allows each MOSFET to be independently controlled and diagnosed, resolving the inability to identify specific failed components in parallel configurations.
Solution Approach 2:
The patent introduces MUXes and switches as intermediary components between the control system and MOSFET gates. These intermediaries enable selective activation and measurement of individual MOSFETs, providing the necessary interface to diagnose failures without requiring physical disassembly or complex testing equipment.
2Reliability
If MUX channels are used to control individual MOSFET gates, then the diagnostic capability is improved, but the device complexity is worsened
Solution Approach 1:
The MUX components serve multiple functions: they act as diagnostic tools for identifying failed MOSFETs, as control mechanisms for selective activation, and as measurement interfaces for voltage detection. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in overall system complexity.
3Measurement precision
If voltage measurement is performed on each MOSFET individually, then the measurement precision is improved, but the time required for diagnosis is worsened
Solution Approach 1:
The patent implements periodic measurement cycles where MUX channels sequentially connect to different MOSFET gates for voltage measurement. This periodic action allows systematic diagnosis of all MOSFETs in the parallel configuration, achieving comprehensive measurement precision while managing diagnosis time through efficient sequential operation rather than requiring simultaneous measurements of all components.
Data Source
AI summary
A circuit and diagnosis method capable of individually diagnosing abnormality of a plurality of internal FETs constituting a MOSFET provided between a secondary battery pack and an electric vehicle. Voltage at both ends of each of the internal FETs is measured while individually turning ON/OFF the internal FETs, and is compared with a diagnosis table in order to determine abnormality thereof.