Vehicle DC-DC Converter Fault Detection for HV-LV Short Protection
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Solution Overview
Problem
DC-DC converters in electrified vehicles face challenges in preventing damage to electrical equipment on the low-voltage side due to short circuits between the high-voltage and low-voltage sides, with existing solutions either increasing complexity and reducing efficiency or significantly increasing costs.
Innovation Solution
A DC-DC converter system with capacitors and a power conversion circuit including switching elements, where a controller determines the failure of switching elements by comparing voltages between capacitors and controls switches to disconnect the high-voltage battery when necessary, preventing damage to low-voltage side equipment without increasing withstand voltage or converting to an isolated type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the DC-DC converter is implemented as a non-isolated type to reduce complexity and maintain efficiency, then device complexity and energy efficiency are improved, but electrical equipment on the low-voltage side may suffer damage due to short circuits between high-voltage and low-voltage sides
Solution Approach 1:
The controller performs preliminary detection of switching element failures by comparing voltages across capacitors before normal operation. When a short circuit is detected between high-voltage and low-voltage sides, the controller preemptively disconnects the high-voltage battery, preventing damage to low-voltage side equipment before it can occur.
Solution Approach 2:
The system continuously monitors voltage differences across capacitors on both high-voltage and low-voltage sides. When the voltage difference exceeds a predetermined threshold indicating a short circuit, the controller receives feedback and automatically disconnects the high-voltage battery to protect the system.
2Reliability
If the withstand voltage of electrical equipment on the low-voltage side is increased to high-voltage side specification to prevent damage, then reliability against short circuit damage is improved, but cost increases significantly
Solution Approach 1:
Instead of over-specifying equipment voltage ratings, the system performs preliminary detection of short circuit conditions by monitoring capacitor voltages. When a short circuit is detected, the controller preemptively disconnects the high-voltage battery, allowing standard voltage-rated equipment to be used without compromising safety.
Solution Approach 2:
The controller acts as an intermediary protection mechanism between the high-voltage and low-voltage sides. Rather than requiring low-voltage equipment to withstand high voltages, the controller monitors system state and interrupts the high-voltage connection when necessary, protecting standard-rated equipment from damage.
3Reliability
If the DC-DC converter is converted to an insulated type using a transformer to prevent short circuit damage, then reliability against short circuit damage is improved, but device complexity increases and efficiency is lowered
Solution Approach 1:
The invention extracts the protection function from the converter's structural design and implements it as a separate control function. Instead of using a transformer for isolation, the controller separately monitors capacitor voltages and disconnects the high-voltage battery when short circuits are detected, achieving protection without adding structural complexity.
Solution Approach 2:
The invention replaces the mechanical/structural isolation approach (transformer-based insulated converter) with an electronic control approach. The controller uses voltage comparison and switching control to achieve the same protection effect without the physical isolation components, reducing complexity while maintaining reliability.
Data Source
AI summary
A DC-DC converter may include a first capacitor connected to a first DC end, a second capacitor connected to a second DC end, a power conversion circuit connected between the first capacitor and the second capacitor and including at least one switching element, and a controller determining, when the second capacitor is charged as the battery is connected to the second DC end, whether the at least one switching element has failed based on a first voltage that is a voltage between opposite ends of the first capacitor and a second voltage that is a voltage between opposite ends of the second capacitor.