EV Charging Circuit Isolation for AC/DC Terminal Switching
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Solution Overview
Problem
Existing charging circuits for electric vehicles are costly and do not effectively prevent dangerous contact voltages during charging, especially when switching between direct-current and alternating-current charging modes.
Innovation Solution
A charging circuit design featuring a direct-current terminal and an alternating-current terminal connected to a rectifier via a DC-to-DC converter, with a changeover switch and diode for voltage adaptation and isolation, ensuring safe and cost-effective charging by preventing direct-current potential from the rectifier from reaching the direct-current terminal during alternating-current charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a charging circuit is equipped with both direct-current and alternating-current charging terminals, then compatibility with different charging standards is improved, but device complexity and cost increase
Solution Approach 1:
The DC-DC converter is designed to perform multiple functions: it adapts voltage during direct-current charging and serves as an isolation path during alternating-current charging. The changeover switch enables a single circuit configuration to handle both charging standards, making the charging circuit universal and compatible with different charging types without requiring completely separate circuits for each standard.
2Reliability
If isolation measures are added to prevent dangerous contact voltages at unused terminals, then safety is improved, but device complexity and cost increase
Solution Approach 1:
The isolation function is merged into the existing changeover switch and DC-DC converter circuitry. During alternating-current charging, the changeover switch automatically isolates the direct-current terminal by routing power through the DC-DC converter path instead of the direct connection path. This combines the switching function with the isolation function, achieving safety without adding separate isolation components.
Solution Approach 2:
The DC-DC converter acts as an intermediary element that provides galvanic isolation between the alternating-current charging input and the direct-current terminal. By routing power through the DC-DC converter's isolated power path, dangerous contact voltages are prevented from appearing at the unused direct-current terminal, while the converter itself serves as the isolating medium.
3Adaptability or versatility
If separate components are used for direct-current and alternating-current charging, then charging functionality is improved, but cost increases
Solution Approach 1:
The DC-DC converter is designed as a universal component that serves both direct-current charging (voltage adaptation) and alternating-current charging (isolation) functions. The changeover switch enables a single circuit configuration to handle both charging standards, eliminating the need for completely separate circuits for each standard and reducing overall component count and manufacturing cost.
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 enables cost-effective and safe charging by using a single-pole changeover switch and diode for isolation, allowing for quick charging and voltage adaptation during both direct-current and alternating-current charging, while preventing dangerous potentials at unused terminals.
Implementation Method 1
The alternating-current terminal (WA) is connected to a rectifier (G1) of the charging circuit LS. The rectifier G1 also has a direct-current side GS, wherein the rectifier G1 is configured to convert an electrical current applied to an alternating-current side WS into a direct current on the direct-current side GS.
Implementation Method 2
A diode is provided in the connection between the direct-current charging terminal and the DC-to-DC converter, which diode blocks when the output of the rectifier generates a voltage for the DC-to-DC converter. As a result, the changeover switch (for changing over between alternating-current charging and direct-current charging) can also be provided with a single pole.
Data Source
AI summary
A charging circuit is equipped with a storage battery terminal, a direct-current terminal and an alternating-current terminal, which is connected to an alternating-current side of a rectifier of the charging circuit. The direct-current side of the rectifier is connected via a changeover switch to a first side of a DC-to-DC converter, wherein the changeover switch connects the first side of the DC-to-DC converter either to the direct-current terminal or to a first potential of the direct-current side of the rectifier. A second potential of the direct-current side of the rectifier is connected to the direct-current terminal via a diode. The reverse direction of the diode points toward the direct-current terminal. A second side of the DC-to-DC converter is connected to the storage battery terminal, to which the direct-current terminal is connected via an isolating switch. A vehicle electrical system having the charging circuit is also described.