Ground-Line Relay Monitoring in Load Drivers for Reverse Battery Faults
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Solution Overview
Problem
Existing load driving devices struggle to detect abnormalities in reverse connection protection relays provided in a ground line, especially when the battery voltage exceeds the voltage tolerance of conventional drive circuits.
Innovation Solution
A load driving device is designed with a power converter and a control circuit that includes a reverse connection protection relay on the ground line. This relay is configured with a transistor and parasitic diode, allowing the control circuit to detect abnormalities based on monitor voltage and voltage drop in the parasitic diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse connection protection relay is provided in a ground line, then protection against reverse connection is improved, but abnormality detection capability deteriorates
Solution Approach 1:
A monitor circuit is introduced as an intermediary component to detect abnormalities in the reverse connection protection relay. The monitor circuit measures the voltage between the source and drain of the transistor, and compares it with a reference voltage to determine relay status. This intermediary detection mechanism enables abnormality detection without interfering with the relay's primary protection function.
Solution Approach 2:
The control circuit implements feedback by continuously monitoring the voltage across the reverse connection protection relay and comparing it with predetermined thresholds. When the monitored voltage exceeds the threshold, the control circuit identifies this as an abnormality signal and takes appropriate action. This feedback mechanism enables real-time detection and response to relay abnormalities.
2Power
If battery voltage is increased to exceed voltage tolerance of conventional drive circuits, then power capability is improved, but compatibility with conventional circuits deteriorates
Solution Approach 1:
The system is segmented into distinct functional blocks: the power converter section that handles high voltage from the battery, and the control circuit section that operates at lower voltages. The reverse connection protection relay acts as an interface between these segments, allowing the high-voltage power section to be upgraded independently while maintaining compatibility with conventional control circuits through standardized low-voltage signaling.
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 enables effective detection of abnormalities in the reverse connection protection relay during initial checks and normal operation, improving the reliability of the load driving device even at higher battery voltages.
Implementation Method 1
The reverse connection protection relay is configured with a transistor whose drain is connected to a battery side of the ground line and whose source is connected to a power converter side, and which has a parasitic diode that conducts current from the source to the drain
Data Source
AI summary
A power converter is provided between a power supply line connected to the battery and a ground line and converts a direct current power of the battery and supplies it to a load. A control circuit controls an operation of the power converter. A reverse connection protection relay is provided on the ground line and, when turned off, cuts off the current flowing from the ground line through the power converter to the power supply line when the battery is reverse connected. The reverse connection protection relay is a transistor having a parasitic diode that conducts current from source to drain. The control circuit detects an abnormality in the reverse connection protection relay based on a monitor voltage corresponding to a voltage drop from the source to the drain of the reverse connection protection relay and a voltage drop of the parasitic diode.