HV Contactor Welding Detection Circuit
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Solution Overview
Problem
Existing methods for detecting welded or stuck closed high voltage (HV) contactors in electric vehicle battery circuits are time-consuming and unable to determine if the first HV contactor is closed during system start-up, posing safety risks and inefficiencies, especially with lithium-ion batteries which increase the welding problem.
Innovation Solution
A detection circuit that generates a short duration pulse signal to determine if HV contactors are welded or stuck closed by comparing the voltage to a stored representative voltage of the coil current, using a controller and sensor to assess the contactor status, allowing for early identification and prevention of potential issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequencing of switches is used to detect welded contactors, then detection capability is improved, but detection time increases and first contactor cannot be detected
Solution Approach 1:
The patent applies preliminary action by performing a resistance check on the first HV contactor before the main control unit activates it. The auxiliary control unit measures the resistance of the first contactor's coil in advance, and if the resistance is below a threshold (indicating welding), the contactor is prevented from closing. This early detection eliminates the time delay associated with post-closing detection sequences.
Solution Approach 2:
The patent introduces an auxiliary control unit as an intermediary between the main control unit and the HV contactors. This auxiliary unit independently monitors the resistance of contactor coils and can prevent closing of suspicious contactors, thereby enabling fast detection without interfering with the main control sequence and reducing overall detection time.
2Power
If high current is passed through HV contactor, then battery power requirements are met, but contact welding increases
Solution Approach 1:
The patent applies preliminary action by measuring the resistance of the HV contactor coil before closing the contactor. If the resistance is below a predetermined threshold (indicating possible welding), the contactor is prevented from closing, thereby avoiding the harmful effect of welded contacts under high current conditions while still allowing normal high-power operation when contacts are healthy.
Solution Approach 2:
The patent implements feedback by continuously monitoring the resistance of contactor coils and using this information to control whether contactors should close. The main control unit receives resistance measurements from the auxiliary control unit and adjusts its closing commands accordingly, creating a feedback loop that prevents welding-related failures while maintaining high current capability.
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
Enables rapid and accurate detection of welded or stuck closed HV contactors, improving safety and efficiency by identifying potential issues before system start-up and reducing the risk of high resistance across the contactors.
Implementation Method 1
A detection circuit is coupled to a coil in the HV contactor. The detection circuit generates a pulse signal that closes a switch and allows current flow through the coil.
Implementation Method 2
The current flow is converted to a voltage by a sensor, where the voltage is received by the controller.
Data Source
AI summary
A circuit that detects if contacts in an HV contactor have been welded or stuck closed. The circuit includes a controller that generates a short duration pulse signal that closes a driver switch and allows current flow through a coil in the HV contactor. The current flow is converted to a voltage by a sensor, where the voltage is received by the controller. The controller uses the voltage, such as by comparing the voltage to a stored representative voltage of the coil current for when the HV contactor is open, to determine whether the HV contactor is closed, and possibly welded or stuck closed, or partially closed. The sensor can be the driver switch or another device, such as a resistor.