Relay Welding Diagnosis Circuit for Grounded Battery Relays
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Solution Overview
Problem
Diagnosing the welding status of relays in a battery system, particularly the negative terminal relay, is challenging due to its connection to the ground level, affecting battery performance and reliability.
Innovation Solution
A relay welding diagnosing circuit and method that utilize a battery management system (BMS) to measure battery pack voltage and derive voltage differences across relays, using photocouplers and resistors to determine if relays are welded by comparing these voltages to the battery pack voltage, ensuring safe battery pack management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the relay for a negative terminal is connected to a ground level, then the circuit structure is simplified, but the difficulty in diagnosing welding of the relay increases
Solution Approach 1:
The patent introduces a diagnosing circuit as an intermediary component that includes a resistor connected between the negative terminal of the inverter and the negative terminal of the battery pack, and a photocoupler that converts the voltage signal to an isolated electrical signal. This intermediary structure enables welding diagnosis of the negative terminal relay by creating a measurable voltage difference without complicating the main circuit architecture.
2Reliability
If welding diagnosis is implemented for all relays, then the reliability of the battery system is improved, but the device complexity increases
Solution Approach 1:
The patent divides the relay welding diagnosis into separate segments: the positive terminal relay diagnosis and the negative terminal relay diagnosis. Each relay has its own dedicated diagnosing circuit path. This segmentation allows welding diagnosis for all relays to be implemented while managing complexity by treating each relay independently with dedicated diagnostic components.
Solution Approach 2:
The diagnosing circuit uses a universal approach where the BMS controls multiple photocouplers (first photocoupler for positive terminal relay, second photocoupler for negative terminal relay) through a unified control mechanism. The same basic circuit topology and diagnosis logic are applied to both relays, reducing overall system complexity through standardized multi-functional design.
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
Effectively diagnoses the welding status of relays, preventing current flow when relays are open and ensuring safe battery pack management, thereby enhancing battery system reliability and performance.
Implementation Method 1
a first photocoupler and a second photocoupler, and a battery management system (BMS) for driving the first and second photocouplers
Data Source
AI summary
A battery system can include a battery pack; a first main relay connected to a positive terminal of the battery pack and a. second main relay connected to a negative terminal of the battery pack; a first control relay connected between the first main relay and a positive terminal of an inverter and a second control relay connected between the second main relay and a negative terminal of the inverter; a welding diagnosing circuit including a first resistor and a first photocoupler connected between the positive terminal of the battery pack and the negative terminal of the inverter and a second resistor, and a second photocoupler connected between the negative terminal of the inverter and the negative terminal of the battery pack; and a battery management system (BMS) configured to drive the first and second photocoupiers to diagnose welding of the second control relay.