LLC Resonant Converter With Series-Parallel Secondary Reconfiguration
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Solution Overview
Problem
Conventional electric vehicle (EV) charging systems face challenges such as long charging times, limited range per charge, and the need for a wide voltage range to accommodate next-generation EVs, with existing LLC resonant converters experiencing high circulating currents and complex designs.
Innovation Solution
An improved LLC resonant converter with a wide output voltage range of 200-1000V, capable of transitioning between series and parallel modes, utilizing a primary sub-circuit with a resonant tank and transformers, and secondary sub-circuits with diode rectifiers, to provide efficient and flexible charging solutions for various EV applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional LLC resonant converters are used, then charging function is provided, but circulating currents are high and design becomes complex
Solution Approach 1:
The converter is divided into two identical modular units, each with its own resonant tank and transformer. The secondary windings are connected in series or parallel configuration, allowing the system to be segmented into manageable modules that reduce circulating currents while maintaining design simplicity through repetition of standardized components.
Solution Approach 2:
The system dynamically switches between series and parallel configurations of the secondary windings based on operating conditions. The series connection provides higher voltage for reduced current operation, while parallel connection provides higher current capability, allowing the converter to adapt its impedance characteristics to minimize circulating currents across different operating points.
2Adaptability or versatility
If output voltage range is extended to accommodate next-generation EVs, then versatility is improved, but maintaining performance across wide voltage range becomes challenging
Solution Approach 1:
The converter employs dynamic reconfiguration of the secondary windings between series and parallel connections, enabling the output voltage to be adjusted across a wide range. The series connection doubles the output voltage compared to parallel connection, allowing the same hardware to serve both 400V and 800V EV platforms while maintaining optimal operating conditions and performance consistency through controlled impedance.
Solution Approach 2:
The dual-unit modular design with switchable series/parallel configuration provides universal compatibility with different EV voltage platforms. The same converter module can serve 400V vehicles in parallel mode and 800V vehicles in series mode, eliminating the need for different hardware designs and ensuring consistent performance across diverse applications.
3Stress or pressure
If series mode is used for high output voltage operations, then voltage sharing is achieved, but current capability is limited
Solution Approach 1:
The system dynamically switches between series and parallel configurations based on the required operating point. In series mode, the voltage is doubled and voltage stress is distributed, suitable for high-voltage applications. In parallel mode, the current capability is doubled while voltage remains at base level, suitable for high-current applications. This dynamic reconfiguration allows optimal performance across the entire operating range.
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 improved LLC resonant converter achieves high efficiency and modular design, maintaining performance across a wide voltage range, reducing circulating currents, and enabling ultra-fast charging capabilities for a variety of EVs, including those with 800V battery systems.
Implementation Method 1
the primary sub-circuit comprising a resonant tank, the resonant tank comprising a combination of a resonant inductor, a resonant capacitor and a magnetizing inductor
Implementation Method 2
a first transformer isolating the primary sub-circuit from the first secondary sub-circuit and comprising a corresponding predetermined number of turns; a second transformer isolating the primary sub-circuit from the second secondary sub-circuit
Implementation Method 3
The first and the second secondary sub-circuits provide an output charging voltage and an output charging current
Data Source
AI summary
An LLC resonant converter is provided. The LLC resonant converter includes a primary sub-circuit coupled to a direct-current (DC) input voltage and a first secondary sub-circuit and a second secondary sub-circuit. The primary sub-circuit includes a resonant tank, that includes a combination of a resonant inductor, a resonant capacitor and a magnetizing inductor. The LLC resonant converter also includes a first transformer isolating the primary sub-circuit from the first secondary sub-circuit and a second transformer isolating the primary sub-circuit from the second secondary sub-circuit. The first and the second secondary sub-circuits are configurable in a series mode and a parallel mode by switching configurations of a plurality of transition switches, and the first and the second secondary sub-circuits provide an output charging voltage and an output charging current for charging an external device. A charging station comprising one or more charging poles, with each charging pole comprising one of more LLC resonant converter modules is also disclosed.