Battery Protection Circuit for Welded Switch Detection
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Solution Overview
Problem
High-voltage switches in environmentally-friendly vehicles can become welded due to excessive currents, increased resistance, and deterioration, leading to instability and potential damage to the high-voltage circuit and electric field system, making it difficult to control the opening of the switch and posing safety risks.
Innovation Solution
A battery protective circuit and pack that includes a resistor, drivers, a negative temperature coefficient element, a short-circuit device, a mechanical switch, and a controller to detect welding of the high-voltage switch and forcibly open the high-current path between the battery and load by supplying specific currents and controlling the circuit components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-voltage switch is used to control the high-current path, then the ability to manage high voltage stability is improved, but the risk of welding and permanent damage due to excessive currents increases
Solution Approach 1:
The protection circuit performs preliminary detection of the high-voltage switch state before excessive current causes welding. The controller detects whether the switch is in a closed or welded state proactively, and prepares the mechanical switch and fuse in advance to forcibly open the high-current path if welding is detected, preventing permanent damage
Solution Approach 2:
A mechanical switch with fuse acts as an intermediary between the high-voltage switch and the high-current path. When the high-voltage switch welds, the mechanical switch can be forcibly opened to interrupt the current, serving as a safety mediator that prevents direct damage to the welded switch and surrounding components
2Stability of the object's composition
If the high-voltage switch welds due to excessive current, then the circuit continuity is maintained, but the control ability to open the switch is lost and safety risks increase
Solution Approach 1:
The protection circuit enables the system to self-diagnose and self-protect when welding occurs. The controller automatically detects the welded state through current sensing, and the mechanical switch with fuse automatically opens the high-current path without requiring manual intervention, making the system self-service in responding to welding failures
3Reliability
If a protection circuit with mechanical switch and fuse is added to forcibly open the high-current path, then the safety against welded switches is improved, but the device complexity increases
Solution Approach 1:
The protection function is extracted as a separate, dedicated circuit module with mechanical switch and fuse, independent from the main high-voltage switch control circuit. This modular extraction allows the safety function to operate autonomously while keeping the main control system simple and unchanged
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 detection of welded high-voltage switches and safe, forced opening of the high-current path, ensuring high voltage safety and preventing damage to the vehicle's electrical system.
Implementation Method 1
a negative temperature coefficient element configured to have resistance that varies in response to heat generation of the resistor
Implementation Method 2
a short-circuit device that is configured to be mechanically deformed by a current
Data Source
AI summary
A battery protective circuit including a resistor connected to a switch between a battery and a load through which a first current flows, a first driver to supply the first current to the switch and the resistor, a negative temperature coefficient element having resistance that varies in response to heat of the resistor, a second driver to supply a second current to the negative temperature coefficient element, a short-circuit device to be mechanically deformed by a current, a mechanical switch including a plurality of terminals connected with the battery, the terminals electrically connected with each other by deformation of the short-circuit device, a fuse connected in series between the battery and the mechanical switch, a circuit-changing switch configured to supply the second current to the short-circuit device or to block supply thereof, and a controller to control operations of the first driver, the second driver, and the circuit-changing switch.