LLC Resonant Converter Control Across Wide Input Voltage Ranges
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Solution Overview
Problem
Existing LLC resonant converters face efficiency issues due to a narrow input voltage range and large frequency variation, which limits their miniaturization potential and operational efficiency, especially when operating in wide voltage ranges.
Innovation Solution
A control method for LLC resonant converters that divides the input voltage range into low, medium-low, medium-high, and high voltage ranges, adopting full-bridge PFM, full-bridge PWM, half-bridge PFM, and half-bridge PWM control modes respectively, to maintain high efficiency and reduce frequency variation across the voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional control solutions are used for LLC resonant converter, then the converter can operate at resonant frequency, but the input voltage range is narrow
Solution Approach 1:
The patent applies dynamics by making the switching topology adjustable between full-bridge and half-bridge modes based on input voltage levels. The controller dynamically selects the appropriate topology and control mode (PFM or PWM) to adapt to varying input voltage conditions, thereby expanding the input voltage range while maintaining operational efficiency across different operating points
Solution Approach 2:
The patent changes key operating parameters including switching topology (full-bridge/half-bridge), control mode (PFM/PWM), and switching frequency based on input voltage levels. By adjusting these parameters according to the input voltage range, the converter maintains high efficiency across a wide input voltage range while avoiding operation far from resonant frequency
2Adaptability or versatility
If the switch frequency deviates from resonant frequency to handle higher input voltage, then the input voltage range is extended, but the efficiency decreases
Solution Approach 1:
The patent dynamically switches between full-bridge and half-bridge topologies based on input voltage levels. At high input voltages, it transitions to half-bridge mode which naturally operates at lower frequencies closer to resonance, thereby maintaining efficiency while handling higher input voltages. This dynamic adaptation prevents large frequency deviations from resonant frequency
Solution Approach 2:
The patent changes the switching topology and control mode based on input voltage ranges. By switching to half-bridge mode and PFM control at high voltages, the system maintains operation near resonant frequency, avoiding the efficiency loss that would occur with large frequency deviations required by fixed topology designs
3Adaptability or versatility
If large frequency variation is used to cover wide voltage range, then the input voltage adaptability is improved, but the miniaturization potential is reduced
Solution Approach 1:
The patent uses dynamic topology switching to maintain a relatively narrow and stable frequency range across wide input voltage variations. By adapting the switching topology (full-bridge/half-bridge) and control mode (PFM/PWM) to input voltage levels, the system avoids large frequency excursions, enabling the use of smaller magnetic components and capacitors for miniaturization
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 achieves high energy transmission efficiency and reduced frequency variation, ensuring efficient operation across a wider input voltage range with improved miniaturization potential by optimizing control modes based on voltage levels.
Implementation Method 1
an LLC resonant circuit can implement zero-voltage switching (ZVS) and quasi-zero current switching (ZCS) of a switch tube
Data Source
AI summary
A control method for an LLC resonant converter includes: dividing an input voltage into four voltage segments: a low voltage, a medium-low voltage, a medium-high voltage, and a high voltage, and correspondingly adopting a full-bridge PFM control mode, a full-bridge PWM control mode, a half-bridge PFM control mode, and a half-bridge PWM control mode respectively. This control method is applicable to a wide input voltage range to achieve steady-state control over an LLC resonant converter, and can maintain a high efficiency of the LLC resonant converter within the whole input voltage range and can also be used in scenarios where a wide output voltage occurs.