Variable-Frequency LLC Resonant Converter for Wide Input Voltage
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Solution Overview
Problem
LLC resonant converters have a limited input voltage range due to their fixed resonant frequency, making it difficult to regulate output voltage over a wide range of input voltages.
Innovation Solution
An LLC resonant converter with an adjustable impedance is introduced, allowing for an adjustable resonant frequency. This is achieved by incorporating a variable impedance circuit in parallel with the resonant inductor, enabling the adjustment of the resonant frequency and voltage regulation across a wide input voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed resonant frequency is used in the resonant circuit, then the converter achieves simple circuit design and easy operation, but the input voltage range is limited and output voltage regulation over wide input voltage variations becomes difficult
Solution Approach 1:
The patent applies the dynamics principle by making the resonant frequency adjustable rather than fixed. A variable impedance circuit is introduced in parallel with the resonant inductor, allowing the resonant frequency to be dynamically changed based on input voltage conditions. This enables the converter to adapt to wide input voltage ranges while maintaining proper regulation, resolving the contradiction between adaptability and circuit complexity.
Solution Approach 2:
The patent implements parameter changes by varying the impedance of the parallel circuit connected to the resonant inductor. By changing the impedance parameter of this parallel circuit, the overall resonant frequency of the LLC resonant circuit can be adjusted. This allows the converter to maintain optimal performance across different input voltage conditions without requiring a completely different circuit topology.
2Reliability
If the resonant frequency is adjusted to regulate output voltage over load variations, then voltage regulation is improved, but the circuit requires additional components and control mechanisms
Solution Approach 1:
The variable impedance circuit serves multiple functions: it adjusts the resonant frequency for voltage regulation, maintains zero-voltage switching operation, and adapts to both light-load and heavy-load conditions. By making this single circuit element multi-functional, the patent achieves improved voltage regulation without proportionally increasing overall circuit complexity.
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 adjustable impedance LLC resonant converter effectively regulates output voltage over a wide range of input voltages while maintaining efficient operation, achieving zero-voltage switching across the entire operating range.
Implementation Method 1
An LLC resonant circuit resonates at a specific frequency, called the resonant frequency
Implementation Method 2
the impedance of a parallel circuit connected to the resonant inductor may be modified to change the resonant frequency of the resonant circuit
Implementation Method 3
achieving zero-voltage switching (ZVS) over the entire operating range
Data Source
AI summary
A resonant converter includes a high-side switch and a low-side switch, both coupled to a common node and driven by a complementary input signal. The common node drives a coupled inductor, the coupled inductor connected in parallel with a variable impedance. The coupled inductor may be coupled in series with a capacitor and a transformer. The variable impedance may be adjusted to modify the resonant frequency of the resonant converter.