Vehicle Charging Circuit Relay Sequencing to Limit Leakage Current
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Solution Overview
Problem
Existing electric circuits with two batteries, an inverter circuit, and a three-phase motor suffer from relay switch deterioration during charging operations.
Innovation Solution
The electric circuit includes a control circuit that manages the switching of relay switches and reverse conducting switching elements to minimize leakage currents, ensuring they are turned off in a controlled manner to reduce switch deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the relay switch is turned OFF when charging processing ends, then the charging operation is completed, but the relay switch deteriorates due to leakage currents
Solution Approach 1:
The control circuit turns OFF the specified upper-side reverse conducting switching element before turning OFF the relay switch. This preliminary action prevents leakage current from flowing through the relay switch contacts at the moment of switching, thereby reducing arc generation and contact deterioration while ensuring safe completion of the charging operation
Solution Approach 2:
The reverse conducting switching element acts as an intermediary component between the battery and the relay switch. By controlling this switching element to turn OFF first, the system mediates the disconnection process to prevent direct leakage current flow through the relay switch, protecting the relay switch from deterioration
Data Source
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AI summary
An electric circuit (10) mounted on a vehicle includes: a first battery (11); a second battery (12); a three-phase motor (40); an inverter circuit (30); a charging port (70); a first relay switch (86); a second relay switch (85); a third relay switch (87); and a control circuit (90). The first relay switch (86) is provided between a high potential wire (31) and a high potential charging terminal. The second relay switch (85) is provided between a low potential wire (32) and a low potential charging terminal. The third relay switch (87) is provided between a positive electrode of the second battery (12) and a neutral point (46). The control circuit (90) is configured to turn OFF the third relay switch (87) and then turn OFF the first relay switch (86) and the second relay switch (85) when a charging operation is to be ended.