DC/DC Converter Isolating Circuit for Reverse Current Protection
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Solution Overview
Problem
In DC-DC converters for vehicle electrical systems, synchronous rectifier circuits can experience overvoltages leading to permanent damage and reverse currents, which can discharge electrical energy and cause failures in safety-critical components, and existing solutions do not effectively prevent these issues without increasing costs or reducing efficiency.
Innovation Solution
An on-board power supply isolating circuit that detects reverse currents by measuring the blocking voltage of semiconductor elements, allowing the system to isolate the power supply from the DC-DC converter if a defect is detected, thereby preventing reverse currents without the need for additional sensors and maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectifier circuits are used to increase efficiency, then power efficiency is improved, but overvoltages can occur causing permanent damage and reverse currents
Solution Approach 1:
The patent applies preliminary action by continuously monitoring the blocking voltage of semiconductor switches before overvoltages can cause damage. The control unit detects voltage drops below a threshold value in advance, enabling preventive isolation of the power supply before reverse currents can discharge electrical energy stores and cause permanent damage to the synchronous rectifier circuit.
Solution Approach 2:
The patent implements feedback by using the control unit to continuously monitor the blocking voltage of semiconductor switches and automatically adjust the isolating switch state based on detected voltage conditions. When the blocking voltage drops below a threshold indicating a fault condition, the control unit activates the isolating switch to prevent further damage, creating a closed-loop protection mechanism that maintains system reliability while preserving efficiency.
2Reliability
If blocking voltage is monitored to detect defects, then reverse currents are prevented, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the control unit to perform multiple functions: it not only controls the isolating switch for protection but also monitors blocking voltage, detects fault conditions, and manages the overall rectifier circuit operation. This multi-functional approach prevents reverse currents and protects the system without requiring separate dedicated protection circuits, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent implements self-service by enabling the semiconductor switches to monitor their own blocking voltage conditions and trigger protective isolation automatically when defects are detected. The system uses its existing control infrastructure to detect faults and activate protection, eliminating the need for additional external protection devices or complex external monitoring circuits.
3Measurement precision
If additional sensors are used to measure reverse current, then detection accuracy is improved, but manufacturing costs increase
Solution Approach 1:
The patent uses blocking voltage as an intermediary parameter to indirectly detect reverse current conditions. Instead of directly measuring reverse current with additional sensors, the control unit monitors the blocking voltage of semiconductor switches, which serves as a reliable indicator of reverse current flow. This intermediary approach provides sufficient detection accuracy to prevent reverse currents while avoiding the manufacturing costs and complexity of direct current measurement sensors.
Solution Approach 2:
The patent replaces physical current measurement sensors with an electrical voltage monitoring system. By substituting direct current measurement (which would require Hall sensors, shunt resistors, or other physical sensors) with blocking voltage monitoring using existing control electronics, the system achieves equivalent or superior detection capability while significantly reducing manufacturing costs and simplifying the bill of materials.
Data Source
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AI summary
The invention relates to an on-board electrical system supply system (1), having a DC/DC converter (11) with at least one semiconductor rectifier element (4), having two supply connections (9a, 9b) for an on-board electrical system, which supply connections are connected at the output end to the DC/DC converter (11), having an isolating switch (5) which is coupled between one of the supply connections (9a, 9b) and the DC/DC converter (11), and having an on-board electrical system isolating circuit (10) which is designed to determine a reverse voltage (U, Ua, Ub) across at least one of the semiconductor rectifier elements (4), and to actuate the isolating switch (5), in order to decouple the on-board electrical system from the DC/DC converter (11), depending on a value of the determined reverse voltage (U, Ua, Ub).