Onboard Charger Residual Current Detection via PFC Isolation Monitoring
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Solution Overview
Problem
Existing vehicle chargers require dedicated hardware for residual current detection and isolation resistance monitoring, leading to increased cost and weight due to the need for separate circuits and components.
Innovation Solution
A control system that utilizes an existing isolation resistance monitoring system to perform residual current detection by measuring isolation resistances at specific switching states of the power factor correction circuit, comparing them to established thresholds, and disabling operation if excessive residual current is detected, thereby eliminating the need for additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated hardware is used for residual current detection and isolation resistance monitoring, then safety and reliability are improved, but device complexity, cost, and weight increase
Solution Approach 1:
The patent combines residual current detection and isolation resistance monitoring functions into a single integrated circuit. The isolation resistance monitoring circuit is configured to measure both the isolation resistance between the DC circuit and ground and the residual current flowing through the circuit, eliminating the need for separate dedicated hardware for each safety function.
Solution Approach 2:
The monitoring circuit performs multiple safety functions simultaneously - it measures isolation resistance, detects residual current, and provides protection against both isolation failures and residual current leakage. This multi-functional approach replaces what would traditionally require separate specialized circuits for each safety mechanism.
2Measurement precision
If separate circuits are used for isolation resistance monitoring and residual current detection, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent integrates both measurement functions into a single circuit architecture, reducing the total number of components and simplifying the manufacturing process. The circuit uses shared measurement paths and processing logic for both isolation resistance and residual current detection.
Solution Approach 2:
The monitoring circuit is designed to handle multiple measurement types through a unified architecture, using the same hardware resources for different safety measurements. This approach reduces component count and manufacturing complexity while maintaining measurement capabilities for both isolation resistance and residual current.
3Measurement precision
If dedicated hardware with high-accuracy sensors and transformer cores is used, then measurement precision is improved, but weight and device complexity increase
Solution Approach 1:
The patent replaces traditional mechanical/electromagnetic measurement methods (transformer cores, windings) with electronic measurement techniques. The monitoring circuit uses electronic sensors and signal processing to detect residual current and isolation resistance, eliminating the need for heavy transformer-based detection hardware.
Solution Approach 2:
The patent extracts the essential measurement function from complex electromagnetic hardware and implements it through a simplified electronic circuit. By removing the transformer core and winding components, the design achieves accurate detection with significantly reduced weight and complexity.
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 approach allows for effective residual current detection without adding hardware costs or weight, enhancing safety and efficiency in vehicle charging operations while reducing the complexity of safety mechanisms.
Implementation Method 1
make first resistance measurements at a positive DC terminal of the PFC circuit and second resistance measurements at a negative DC terminal of the PFC circuit
Data Source
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AI summary
A control system for controlling a vehicle charger including a power factor correction (PFC) circuit includes a resistance measuring circuit configured to make first resistance measurements at a positive DC terminal of the PFC circuit and second resistance measurements at a negative DC terminal of the PFC circuit. The control system includes a controller configured to, in response to the PFC circuit being in a selected switching state, compare one of the first resistance measurements to a positive threshold. The one of the first resistance measurements is made while the PFC circuit is in the selected switching state. The positive threshold is based on a first parallel combination of one or more resistances corresponding to the selected switching state of the PFC circuit. If the one of the first resistance measurements is less than the positive threshold, the controller disables operation of the vehicle charger.