Vehicle Charging Circuit Relay Sequencing to Reduce Switch Wear
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Solution Overview
Problem
Existing electric circuits with two batteries, an inverter circuit, and a three-phase motor face challenges in reducing the deterioration of relay switches during charging operations.
Innovation Solution
The electric circuit incorporates a control circuit that manages the operation of three relay switches and upper-side reverse conducting switching elements to optimize charging and reduce relay switch deterioration. This includes turning OFF the third relay switch and then the first and second relay switches when the charging operation ends, and optionally detecting and managing leakage currents to further reduce relay switch wear.
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
Solution Approach 1:
The control circuit performs preliminary actions by turning OFF the upper-side reverse conducting switching element before turning OFF the third relay switch. This preliminary action ensures that any leakage current path is eliminated before the relay switch is opened, preventing arc formation and reducing relay switch deterioration while still completing the charging operation.
2Productivity
If the upper-side reverse conducting switching element is turned ON during charging, then the second battery can be charged, but leakage current may flow after switching element is turned OFF
Solution Approach 1:
The patent converts the potentially harmful leakage current into a beneficial charging path. By controlling the upper-side reverse conducting switching element to be ON during charging, the circuit allows current to flow through the second battery for charging. The same switching element, when properly timed, prevents harmful leakage by eliminating alternative current paths before relay switches are opened.
Data Source
AI summary
An electric circuit mounted on a vehicle includes: a first battery; a second battery; a three-phase motor; an inverter circuit; a charging port; a first relay switch; a second relay switch; a third relay switch; and a control circuit. The first relay switch is provided between a high potential wire and a high potential charging terminal. The second relay switch is provided between a low potential wire and a low potential charging terminal. The third relay switch is provided between a positive electrode of the second battery and a neutral point. The control circuit is configured to turn OFF the third relay switch and then turn OFF the first relay switch and the second relay switch when a charging operation is to be ended.