LLC Resonant Converter Wide Voltage Range Control
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Solution Overview
Problem
Conventional LLC resonant converters face challenges in achieving a wide output voltage range while maintaining efficiency, as they often require high input voltages, leading to increased costs and complexity, and existing solutions fail to provide a sufficiently wide range without compromising efficiency or increasing part count.
Innovation Solution
The implementation of a serial half-bridge LLC resonant converter using a combination of symmetrical and asymmetrical modulation schemes, along with closed-loop control, allows for efficient regulation of output voltage over a wide range by adjusting switching frequency and modulation schemes in response to control signals, reducing the need for high input voltages and minimizing device stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the LLC resonant converter operates at a very wide frequency range to achieve wide output voltage range, then the output voltage range is improved, but the efficiency deteriorates
Solution Approach 1:
The patent employs dynamic switching between full-bridge and half-bridge topologies based on the required output voltage level. The controller dynamically selects the appropriate topology mode to maintain operation near resonant frequency while achieving wide output voltage range, thus resolving the contradiction between adaptability and efficiency.
Solution Approach 2:
The patent divides the operating range into two segments: full-bridge mode for high output voltage requirements and half-bridge mode for lower output voltage requirements. This segmentation allows each mode to operate optimally within its range, maintaining efficiency while providing wide overall voltage coverage.
2Adaptability or versatility
If high input voltage is used to achieve wide output voltage range, then the output voltage range is improved, but the device complexity and cost increase
Solution Approach 1:
The patent uses dynamic topology switching to achieve wide output voltage range without requiring high input voltage. By dynamically transitioning between full-bridge and half-bridge configurations, the system can generate high output voltages from moderate input voltages, reducing the need for high-voltage rated components and simplifying the overall device complexity.
3Adaptability or versatility
If the LLC resonant converter is designed for wide output voltage range, then the adaptability is improved, but the efficiency at resonant frequency deteriorates
Solution Approach 1:
The patent dynamically adjusts the operating frequency and topology based on the desired output voltage. When operating in full-bridge mode, the converter can maintain resonance for high efficiency. When transitioning to half-bridge mode for lower output voltages, the controller adjusts frequency to maintain optimal efficiency, thus preserving resonant operation benefits across the wide voltage range.
Solution Approach 2:
The patent changes operating parameters (switching frequency, topology configuration) dynamically based on output voltage requirements. This allows the converter to maintain efficient resonant operation across different output voltage levels by adjusting parameters to keep the resonant tank operating near its resonant frequency.
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
This approach enables efficient operation over a very wide output voltage range with reduced switching frequency, balancing current stress and extending device life, while maintaining high efficiency and flexibility across different load conditions.
Implementation Method 1
The LLC resonant converter operates at a very wide frequency range
Implementation Method 2
an isolation transformer TR having a primary-side winding connected in parallel with the magnetizing inductor Lm
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An efficient control method for an isolated multilevel DC/DC resonant converter (700, 800, 1000, 1400, 1600. 1650, 1700, 1750) achieves a wide output voltage range with a narrow device switching frequency range, relative to the output voltage range and the device switching frequency range of the prior art. At any given time, a control circuit (801, 1401, 1601, 1651, 1701, 1751) selects one of two different modulation schemes to operate the primary-side switching devices of the resonant converter (700, 800, 1000, 1400, 1600. 1650, 1700, 1750) based on at least one of output voltage (Vo), output current, input signal, and one or more external control signals. Together with a selected device switching frequency, the two modulation schemes generate different voltage waveforms to a primary-side transformer, which are coupled to the secondary-side to provide different output voltages (Vo).