Current-Based Anti-Chatter Latch for Automotive Relay Control
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Solution Overview
Problem
Relays in automotive power systems may inaccurately open due to rapidly changing electrical events, leading to non-requested detachments, particularly caused by inductive nature and loss of voltage, which can result in inappropriate relay operation.
Innovation Solution
A controller commands the relay to open based on specific voltage and current thresholds, including a voltage across the coil remaining below a threshold for a predetermined period and current through the coil being below a certain value, ensuring accurate relay operation by considering dynamic electrical current differentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay opens upon detection of voltage loss, then the relay protects against electrical faults, but the relay may open inappropriately due to transient voltage losses and inductive effects
Solution Approach 1:
The controller monitors voltage and current parameters before commanding the relay to open, performing preliminary checks to distinguish between transient drops and genuine fault conditions. This preliminary action prevents premature relay opening due to transient voltage losses while maintaining protection against actual faults.
Solution Approach 2:
The controller acts as an intermediary between the voltage loss detection and relay opening action. It introduces intermediate processing by evaluating multiple parameters (voltage threshold duration, current threshold) before triggering the relay opening, thereby filtering out false signals from inductive effects and transient losses.
2Speed
If the relay opens immediately upon voltage threshold detection, then the response time is fast, but false openings occur due to transient electrical events
Solution Approach 1:
The controller performs preliminary monitoring of voltage and current parameters before commanding relay opening. By checking whether voltage remains below the threshold for a predetermined period and verifying current is below the current threshold, it distinguishes genuine faults from transient events, ensuring accurate relay operation without sacrificing response time to actual faults.
3Device complexity
If the relay considers only voltage threshold for opening, then the control logic is simple, but the relay opens inappropriately during transient electrical events
Solution Approach 1:
The control logic transitions from monitoring a single voltage parameter to monitoring multiple parameters (voltage threshold duration and current threshold). This parameter expansion, while increasing complexity, provides more robust fault detection by considering the dynamic electrical current differential, thereby improving relay operation stability and preventing inappropriate openings during transient events.
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
This approach prevents unnecessary relay detachments by accurately determining when to open the relay, enhancing the reliability of electrical communication between the traction battery and vehicle load by accounting for inductive effects and transient voltage losses.
Implementation Method 1
a relay including a coil
Data Source
AI summary
A vehicle includes a traction battery, an electric machine, a relay electrically between the traction battery and electric machine, and a controller. When closed, the relay completes an electrical circuit including the traction battery and electric machine. The controller selectively commands the relay to open based on a voltage across a coil of the relay and a current through the coil.