Bidirectional Isolated DC-DC Converter with Parallel Topologies
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Solution Overview
Problem
Conventional DC-DC converters in vehicles are unidirectional, limiting their ability to handle increasing electric loads and requiring bidirectional capabilities for efficient power transfer between high and low voltage stages, which is necessary for advanced vehicle functions like charging and self-diagnosis.
Innovation Solution
A large-capacity bidirectional isolated DC-DC converter system utilizing a parallel operation of phase-shift full bridge converters with full bridge synchronous rectification and active-clamp forward converters, allowing both buck and boost modes, which reduces semiconductor power loss and minimizes output ripple by controlling switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bidirectional LDC with boost function is added to handle increasing vehicle electrical loads, then power transfer capability from low voltage to high voltage is improved, but device complexity increases due to requiring two converters with different power circuit topologies operating in parallel
Solution Approach 1:
The system divides the power conversion function into two separate converters: a phase-shift full bridge converter for high voltage to low voltage conversion, and an active-clamp forward converter for low voltage to high voltage conversion. Each converter is optimized for its specific direction, allowing independent design and control while working together to provide bidirectional capability.
Solution Approach 2:
The controller unit manages both converters and can operate in different modes (buck mode using phase-shift full bridge converter, boost mode using active-clamp forward converter) to provide universal power transfer capability in both directions, making the system adaptable to various operating conditions.
2Strength
If phase-shift full bridge converter with full bridge synchronous rectification is used, then voltage rating specifications of power semiconductor devices are reduced by half, but a greater number of power semiconductors are required
Solution Approach 1:
The full bridge configuration divides the voltage handling into two series-connected switches per leg, where each switch only needs to block half the total voltage. This segmentation of voltage stress allows using lower voltage-rated, more efficient power semiconductors while maintaining the required voltage blocking capability.
3Quantity of substance
If active-clamp forward converter is used, then the number of power semiconductors is minimized, but semiconductor power loss increases when output capacity is increased
Solution Approach 1:
The active-clamp forward converter uses a clamp circuit with capacitor and diode to control the voltage across the main switch, allowing the switch to operate at optimized voltage and current parameters that reduce conduction losses while maintaining a simpler semiconductor count compared to full bridge topologies.
4Adaptability or versatility
If parallel operation of two converters is implemented, then both buck and boost modes are enabled, but output ripple increases due to switching frequency differences
Solution Approach 1:
The two converters operate at different switching frequencies and with different duty cycles optimized for their respective directions. The phase-shift full bridge converter operates at a frequency and phase relationship optimized for buck mode, while the active-clamp forward converter operates at a different frequency optimized for boost mode, allowing each to perform its function efficiently.
Solution Approach 2:
The controller alternates between buck mode and boost mode operation based on system requirements, activating the appropriate converter for each direction. This periodic switching between operational modes allows the system to provide bidirectional power transfer while managing output ripple through controlled operation cycles.
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
Enables efficient bidirectional power transfer, improving power quality and reducing electromagnetic interference while optimizing semiconductor usage and efficiency across varying input voltage fluctuations.
Implementation Method 1
a magnetic component responsible for power transfers and electrical insulation between a high voltage and a low voltage
Implementation Method 2
The phase-shift full bridge converter with full bridge synchronous rectification applied may reduce (with a low cost) the voltage rating specifications of power semiconductor devices used in high and low voltage stages by half
Data Source
AI summary
A Low-voltage DC-DC Converter (LDC) includes a new bidirectional isolated LDC, in which two converters with different power circuit topologies operate in parallel in order to enable both buck mode and boost mode. The two applied converters are a phase-shift full-bridge converter with full-bridge synchronous rectification and an active-clamp forward converter. According to the present invention, it is possible to achieve the advantages of both a phase-shifted full-bridge converter with full-bridge synchronous rectification applied and an active clamping forward converter. Thus, it is possible to minimize output voltage and current ripples, thereby improving the quality of the LDC output power while minimizing electromagnetic waves generated while a product is operating.