Bidirectional LLC Power Converter for Wide DC Voltage Range
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Solution Overview
Problem
Existing resonant DC/DC converters have a narrow voltage operating range due to zero voltage switching (ZVS) constraints, limiting their ability to handle wide voltage ranges required for electric vehicle charging systems.
Innovation Solution
A bidirectional isolated LLC resonant circuit with a controller that adjusts switching patterns based on duty ratio and phase shift, allowing for efficient voltage conversion across a wider range, including both charging and discharging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If resonant DC/DC converter is used to improve efficiency, then conversion efficiency is improved, but voltage operating range becomes narrow due to ZVS constraints
Solution Approach 1:
The patent applies dynamics by making the switching pattern adjustable based on operating conditions. The controller dynamically selects between different switching patterns (first pattern for charging operation, second pattern for discharging operation) depending on the direction of power flow and voltage levels, allowing the system to adapt to different operating states while maintaining ZVS and expanding the voltage operating range
Solution Approach 2:
The patent changes the switching pattern parameters (duty ratio, phase shift) based on the operating mode. By adjusting the duty ratio and phase shift between primary and secondary switching elements, the system can maintain resonance conditions across a wider voltage range while preserving ZVS characteristics, thus resolving the contradiction between efficiency and operating range
2Device complexity
If fixed duty ratio control is used, then control simplicity is maintained, but output voltage control range becomes narrow
Solution Approach 1:
The controller dynamically adjusts the duty ratio and phase shift based on the operating mode (charging/discharging) and voltage levels. This dynamic control allows the system to achieve a wider output voltage control range while maintaining relatively simple control logic through pattern selection rather than complex continuous adjustment
3Power
If asymmetric half-bridge method is used, then voltage magnitude conversion is achieved, but only half of input voltage can be utilized for large power applications
Solution Approach 1:
The patent implements a bidirectional converter that can operate in both charging mode (power flow from primary to secondary) and discharging mode (power flow from secondary to primary). This multi-functionality allows the system to utilize the full input voltage range for both charging and discharging operations, doubling the effective power conversion capability compared to unidirectional asymmetric half-bridge methods
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 a significant expansion of the power conversion range, achieving highly efficient and accurate control for both charging and discharging operations, thereby supporting a broader range of electric vehicle battery voltages.
Implementation Method 1
resonant DC/DC converters have a disadvantage in that the voltage operating range is narrow due to the constraints of zero voltage switching (ZVS)
Implementation Method 2
The bidirectional isolated LLC resonant circuit includes a transformer having a primary coil and a secondary coil
Data Source
AI summary
A power converter including a converter mechanism having a bidirectional isolated LLC resonant circuit and a controller which controls the converter mechanism is provided. The bidirectional isolated LLC resonant circuit includes a transformer having primary and secondary coils, a primary circuit having a primary input/output terminal pair and six primary switching elements, a secondary circuit having a secondary input/output terminal pair and four secondary switching elements, and an LLC circuit disposed between the transformer and the primary circuit. The bidirectional isolated LLC resonant circuit performs a charging operation and a discharging operation. The controller has switching control information related to a duty ratio and a phase shift that are set according to a magnitude relationship of inputted/outputted direct current (DC) voltages, and changes a switching pattern of each of the primary and secondary switching elements in the charging operation and the discharging operation based on the switching control information.