EV Charging Relay Coil Discharge for Back-EMF and EMI Control
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Solution Overview
Problem
Existing relay devices in electric vehicles face challenges with accurate on-off control due to back electromotive force generated in the relay coil, leading to difficulties in managing inrush currents and electromagnetic interference (EMI) noise during charging.
Innovation Solution
A relay device with a switch that operates based on the magnitude of applied voltage, incorporating a first and second discharge unit and control units to manage back electromotive force through pulse width modulation (PWM) signals, allowing selective discharge through diodes and switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relay device is used to control charging current, then charging operations can be performed, but back electromotive force generated in the relay coil causes inaccurate on-off control
Solution Approach 1:
The patent extracts the harmful back electromotive force from the relay coil by introducing separate discharge units (first and second discharge units) that provide dedicated pathways for the back EMF to dissipate. This isolates the harmful effect from the main control circuit, allowing accurate on-off control to be achieved despite the presence of back electromotive force in the relay coil.
Solution Approach 2:
The patent introduces discharge units with diodes as intermediary components between the relay coil and the control circuit. These intermediaries provide a controlled path for back electromotive force discharge, preventing it from interfering with the accurate on-off control of the relay while still allowing the relay to function properly.
2Reliability
If a relay discharge circuit is added to solve back electromotive force issues, then on-off control accuracy improves, but device complexity increases
Solution Approach 1:
The patent segments the discharge function into multiple independent discharge units (first discharge unit with first diode, second discharge unit with second diode). Each discharge unit handles specific aspects of back electromotive force discharge, allowing the system to achieve reliable control while distributing the complexity across modular, manageable components rather than requiring a single complex circuit.
3Speed
If fast charging is performed with high voltage applied to EVSE, then charging speed increases, but inrush current is generated in the battery
Solution Approach 1:
The patent applies preliminary action by using the relay device to pre-control the voltage application to the battery before fast charging begins. The relay's controlled switching, combined with the discharge units that manage back electromotive force, prevents inrush current from occurring in the first place, allowing fast charging to proceed safely without the harmful effects of current surges.
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 solution provides enhanced adaptability to various environments by minimizing EMI noise and ensuring fast or controlled discharge of back electromotive force, depending on the specific requirements.
Implementation Method 1
a first discharge unit and a second discharge unit configured to discharge a back electromotive force generated in the coil when the relay unit is turned off
Data Source
AI summary
A relay device according to an embodiment of the present invention comprises: a relay unit in which a switch operates according to a voltage applied to a coil; a first control unit that controls a voltage applied to the coil by turning on and off a first switching element according to a first control signal; a first discharge unit and a second discharge unit that discharge a back electromotive force generated in the coil when the relay unit is turned off; and a second control unit including a second switching element, and controlling the back electromotive force to be discharged through the first discharge unit or the second discharge unit by turning on and off the switching element according to a second control signal.