Capacitor Backup Power for HV Battery Disconnect Activation
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Solution Overview
Problem
In electric or hybrid vehicles, the disconnecting device used to safely disconnect the high voltage battery from the motor and other electric parts during accidents often fails due to abrupt disconnection of the primary power source, leading to potential fires and explosions, as the pyrotechnic ignition element may not be triggered reliably in such scenarios.
Innovation Solution
A power source system comprising a capacitor-based redundant power source and a diagnostic system that monitors the health of the pyrotechnic ignition element, providing alternative paths for generating an activating current to ensure reliable disconnection of the high voltage battery, even if the primary power source is unavailable, using a combination of charging circuits, electronic switching circuits, and test circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single power source is used to activate the disconnecting device, then the device complexity is low, but the reliability of disconnection is insufficient under abrupt power loss conditions
Solution Approach 1:
The capacitor is pre-charged to a predetermined voltage level during normal operation through the charging circuit. This preliminary energy storage ensures that when an abrupt power loss occurs, the capacitor can immediately provide the necessary activating current to trigger the disconnecting device without delay, resolving the reliability issue while maintaining a manageable system structure.
Solution Approach 2:
The capacitor serves as a buffer or cushion against abrupt power loss events. By storing energy in advance, it compensates for sudden power disruptions, ensuring the disconnecting device can still be activated reliably. This cushioning mechanism addresses the reliability concern without significantly increasing system complexity.
2Reliability
If a capacitor-based redundant power source is added to provide alternative activating current, then the reliability of disconnection is improved, but the device complexity increases
Solution Approach 1:
The capacitor serves multiple functions: it acts as a buffer during normal operation, provides backup power during abrupt power loss, and can be charged through the existing charging circuit. This multi-functionality reduces the need for separate dedicated backup power components, thereby limiting the increase in system complexity while maintaining improved reliability.
Solution Approach 2:
The capacitor acts as an intermediary energy storage element between the power source and the disconnecting device. It mediates the power transfer, smoothing out abrupt power losses and ensuring continuous capability to activate the disconnecting device. This intermediary approach provides reliability improvement with minimal additional circuit complexity.
3Reliability
If the capacitor voltage is increased to ensure sufficient activating current under all conditions, then the reliability is improved, but the energy storage requirements and potential safety risks increase
Solution Approach 1:
The system dynamically adjusts the capacitor voltage threshold for triggering based on the actual power source status and load conditions. Instead of maintaining a constantly high voltage, the control circuit monitors parameters and adjusts the threshold accordingly, ensuring sufficient activating current is available while minimizing unnecessary energy storage and associated safety risks.
Solution Approach 2:
The control circuit continuously monitors the capacitor voltage and power source status, providing feedback to adjust the charging rate and discharge threshold. This feedback mechanism ensures the capacitor maintains just enough voltage to provide reliable activating current without excessive energy accumulation, balancing reliability with energy efficiency and safety.
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 enhances the reliability and safety of disconnecting the high voltage battery by providing a redundant power source and health monitoring system, ensuring consistent operation and reducing the risk of accidents and fires during vehicle crashes.
Implementation Method 1
a capacitor (16) which is coupled via an input to an output of the charging circuit (15)
Implementation Method 2
the disconnecting device (11) may comprise a pyrotechnic ignition element (12)
Data Source
Figure 1
Figure 2
AI summary
Power source and method for providing an activating current A power source (10) comprises an input terminal (14), a charging circuit (15) having an input (22) coupled to the input terminal (14) of the power source (10), a capacitor (16) having a first electrode coupled to an output (20) of the charging circuit (15), an electronic switching circuit (31), a discharge protection circuit (50), a control switch (32) and a disconnecting device (11). An input (38) of the electronic switching circuit (31) is coupled to the first electrode of the capacitor (16). The control switch (32) includes a first terminal (33) which is coupled via the discharge protection circuit (50) to the input terminal (14) of the power source (10) and is coupled to an output of the electronic switching circuit (31). The disconnecting device (11) comprises a first terminal (36) coupled to a second terminal (34) of the control switch (32).