LLC Resonant Converter With Variable Turns Ratio for Wide Output Range
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Solution Overview
Problem
Existing LLC resonant converters face limitations in adjusting the range of output voltage and current due to limited fine-tuning capabilities of magnetic components and resonant tank parameters, especially at high switching frequencies.
Innovation Solution
The proposed LLC resonant converter incorporates a transformer circuit with variable turns ratio and dynamically adjustable resonant tank parameters, including inductance and capacitance, to enhance the range of output voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency of the switching power supply is increased to reduce the size of magnetic elements, then the size, weight and cost of the power supply device are reduced, but the switching loss of the switching device increases
Solution Approach 1:
The patent implements dynamic adjustment of the transformer turns ratio through a switching network that can reconfigure the primary winding connections. This allows the system to adapt the transformation ratio in real-time based on operating conditions, enabling optimal performance across different load scenarios and frequency ranges, thereby reducing switching losses while maintaining compact magnetic element sizes
Solution Approach 2:
The patent changes the electrical parameters of the transformer by dynamically reconfiguring the winding connections. By altering the effective turns ratio through switching different winding configurations, the system can optimize the impedance matching and voltage transformation characteristics, which helps reduce switching losses while maintaining small magnetic component sizes
2Loss of energy
If soft-switching technology is used to achieve zero-voltage switching and zero-current switching, then switching loss is reduced to zero, but the circuit complexity increases due to the need for resonance technology
Solution Approach 1:
The patent integrates multiple functions into the transformer structure by combining the transformation function with the resonance function. The transformer windings are configured to serve both as coupling elements and as part of the resonant circuit, eliminating the need for separate resonance components and reducing overall circuit complexity while maintaining soft-switching capabilities
Solution Approach 2:
The patent merges the transformer and resonant circuit into a single integrated structure. The primary and secondary windings are designed to simultaneously perform voltage transformation and provide the necessary reactance for soft-switching, thereby reducing the number of discrete components and simplifying the overall circuit topology
3Loss of energy
If the turns ratio of the transformer is fixed, then the magnetic components can be optimized for a specific operating point, but the adjustment range of output voltage and current is limited
Solution Approach 1:
The patent implements dynamic adjustment of the transformer turns ratio through a switching network that can reconfigure the primary winding connections. This allows the system to adapt the transformation ratio in real-time based on load conditions, enabling wide adjustment range of output voltage and current while maintaining high efficiency across different operating points
Solution Approach 2:
The patent divides the transformer primary winding into multiple sections that can be independently switched. By selectively connecting different sections in series or parallel, the system can achieve multiple discrete turns ratio settings, providing both optimization for specific operating points and wide adjustment range for different load conditions
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 solution allows for increased power density and improved efficiency of the LLC resonant converter by dynamically adjusting the transformer turns ratio and resonant tank parameters, enabling operation beyond MegaHz frequencies.
Implementation Method 1
The LLC resonant converter is a resonant inverter with three reactive elements where the DC input voltage is turned into a square wave by a switch network arranged as either a half- or full-bridge to feed the resonant LLC tank that effectively filters out harmonics providing a sinusoidal like voltage and current waveform
Implementation Method 2
This in turn feeds a transformer that provides voltage scaling and primary-secondary isolation
Data Source
AI summary
An LLC resonant converter with variable turns ratio includes a switching circuit coupled to a DC input voltage for converting the DC voltage into switching signal, a resonant tank coupled to the switching circuit and configured to receive the switching signal to provide a primary current, a transformer circuit coupled to the resonant tank. The transformer circuit includes a plurality of separated transformers, each has a primary side winding and a side secondary side winding, where individual transformer has different turns of primary side winding, which can be dynamically selected to couple with the primary side winding of other transformers in series or in parallel to form a dynamically changing equivalent primary side winding, so that the turns ratio in the transformer circuit can be dynamically changed accordingly.