HV Battery Charging Protection Using Voltage Slope Contact Detection
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Solution Overview
Problem
Existing high voltage on-board power supplies in vehicles face challenges in ensuring safe operation during charging, particularly when a galvanically coupled DC-DC converter is present, as physical contact between the converter and a charging station can lead to dangerous electric shocks due to incorrect operation of protective circuits.
Innovation Solution
A method that determines the slope of the voltage between the DC-DC converter and the reference potential to identify contact location, allowing the protective circuit to respond correctly by either not closing or adjusting circuit breakers to prevent dangerous discharges, ensuring safe operation even when contact occurs at critical positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a galvanically coupled DC-DC converter is used to enable charging from a charging station with lower voltage than the high voltage battery nominal voltage, then the adaptability of the power supply system is improved, but the risk of electric shock to humans increases due to potential physical contact between the converter and charging station
Solution Approach 1:
The protective circuit is activated before charging begins by detecting voltage slope changes that indicate physical contact between the DC-DC converter and charging station. This preliminary detection and protection mechanism prevents electric shock before it can occur, allowing the system to safely accommodate charging from stations with different voltage levels.
Solution Approach 2:
The voltage slope detection mechanism acts as an intermediary between the DC-DC converter and the protective circuit. By monitoring the rate of change of voltage rather than just voltage levels, the system can distinguish between normal operation and dangerous physical contact conditions, enabling selective activation of protection only when necessary.
2Reliability
If the protective circuit is designed to close circuit breakers upon detecting physical contact with high voltage potential, then the safety protection is improved, but the system may incorrectly close circuit breakers when contact occurs at non-critical positions, causing unnecessary charging interruptions
Solution Approach 1:
The protective circuit applies different responses based on the location of physical contact. By detecting the voltage slope characteristics specific to each contact position (P1, P2, P3), the system determines whether protection is needed. Contact at P1 or P3 triggers circuit breaker closure, while contact at P2 does not, as it occurs at a non-critical position where the charging station provides inherent protection.
Solution Approach 2:
The protective circuit uses dynamic voltage slope detection to adapt its response to different contact scenarios. Rather than a static protection mechanism, the system continuously monitors the rate of voltage change and adjusts its behavior accordingly, closing circuit breakers only when the slope indicates a dangerous contact position.
3Measurement precision
If the voltage measuring device continuously monitors voltage to detect physical contact, then the detection capability is improved, but the complexity of the measurement and control system increases
Solution Approach 1:
Instead of monitoring multiple voltage parameters simultaneously, the system focuses on a single critical parameter: the slope (rate of change) of the voltage between the high voltage potential and reference potential. This parameter change approach simplifies the measurement system while maintaining high detection accuracy for different contact positions.
Data Source
AI summary
A method for operating a high voltage on-board power supply of a vehicle having a protective device for when physical contact with the high voltage potentials and a reference potential when charging a high voltage battery by a direct current charging station is provided. The protective device has a voltage measuring device and a protective switch. In one of the high voltage potentials, between the protective device and a direct current charging connection, a galvanically coupled DC/DC converter is arranged and the direct current charging station provides a charging voltage, which is lower than a nominal voltage of the high voltage battery. It is determined whether physical contact with the high volage potential, in which the DC/DC converter is arranged, occurs between the DC/DC converter and the direct current charging station, and this is used as a triggering criterion for controlling the protective circuit and/or a further protective circuit.