Relay Status Monitor Circuit for Welded Contact Detection
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Solution Overview
Problem
Relays in electric vehicle chargers can weld together due to high grid voltage, leading to arcing and potential failure to open at the end of the charging cycle, which complicates the monitoring and control of relay states.
Innovation Solution
A relay status monitor circuit is introduced, comprising a capacitor, clamp circuit, and comparator, which detects the state of the relay by generating a signal indicative of whether the relay is open or closed, allowing for corrective control actions to ensure proper operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relays are used to control power lines in EV chargers, then current flow control is achieved, but relay welding and arcing occur due to high grid voltage
Solution Approach 1:
The patent applies preliminary action by monitoring the relay status before actual switching operations. The monitor circuit detects potential welding conditions and arcing risks in advance, allowing the controller to take preventive measures before the relay fails, thus improving reliability while preventing harmful effects.
Solution Approach 2:
The patent implements feedback by continuously monitoring relay status through the monitor circuit and providing real-time information to the controller. This feedback mechanism enables the system to detect relay welding and arcing conditions and respond appropriately, resolving the contradiction between maintaining relay operation and preventing harmful effects.
2Measurement precision
If relay status monitoring is implemented, then relay state detection is achieved, but device complexity increases
Solution Approach 1:
The patent uses an intermediary approach by introducing a dedicated monitor circuit that acts as a mediator between the relay and the controller. This separate monitoring subsystem provides accurate relay state detection without requiring the main controller to directly interface with the relay, thus improving measurement precision while managing device complexity through functional separation.
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
The relay status monitor circuit effectively detects the state of relays in electric vehicle chargers, preventing welding and ensuring reliable opening and closing, thereby enhancing safety and efficiency in charging operations.
Implementation Method 1
The relay status monitor circuit includes a capacitor coupled to the first terminal of the relay status monitor circuit
Implementation Method 2
A comparator has a first comparator input terminal coupled to the second terminal of the capacitor and has a second comparator input terminal coupled to the output terminal of the reference voltage circuit
Data Source
AI summary
A battery charger includes a relay having a first terminal and a second terminal. A capacitor has a first terminal and a second terminal. The first terminal is coupled to the second terminal of the relay. A clamp circuit is coupled to the second terminal of the capacitor. A reference voltage circuit has an output terminal. A comparator has a first comparator input terminal coupled to the second terminal of the capacitor and has a second comparator input terminal coupled to the output terminal of the reference voltage circuit.