LLC Resonant Converter Design and Applications

LLC resonant converters represent a class of soft-switching DC-DC converters that employ two inductive elements (magnetising and leakage) in series with a resonant capacitor to shape voltage and current waveforms. By operating around the resonant frequency, these converters achieve zero-voltage switching (ZVS), minimise switching losses and electromagnetic interference, and permit high power density through elevated switching frequencies. Their inherent isolation, wide output range and low device stress have led to widespread deployment in applications such as electric-vehicle chargers, photovoltaic inverters, data-centre power supplies, LED drivers and consumer electronics. Recent design efforts have concentrated on optimising magnetic integration, extending frequency modulation range for voltage regulation, and leveraging wide-bandgap semiconductors to push performance limits. Control methods have evolved to manage load transients, maintain power factor and balance currents in multi-phase configurations. Together, these advances underpin the converter’s global significance in low-loss, high-efficiency power conversion across industrial and consumer contexts.

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LLC Resonant Converter Design and Applications publication trend

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Technical terms

LLC resonant converter: A DC-DC converter topology using two inductors (leakage and magnetising) and a capacitor in series to achieve soft-switching and voltage regulation around a resonant frequency.

Zero-Voltage Switching (ZVS): A switching technique in which power transistors switch at or near zero voltage, substantially reducing switching losses and stress on devices.

Resonant tank: The combination of inductor(s) and capacitor that defines the resonant frequency and energy exchange characteristics within the converter.

Magnetic integration: The design strategy of combining transformer and resonant inductor functions into one magnetic component to reduce size, weight and parasitic losses.

References

1. LLC resonant converter topologies and industrial applications — A review. Chinese Journal of Electrical Engineering (2020).
2. Control Design and Performance Analysis of a Double-Switched LLC Resonant Rectifier for Unity Power Factor and Soft-Switching. IEEE Access (2020).
3. Analysis and Design of an Integrated Magnetics Planar Transformer for High Power Density LLC Resonant Converter. IEEE Access (2021).
4. High Frequency, High Efficiency, and High Power Density GaN-Based LLC Resonant Converter: State-of-the-Art and Perspectives. Applied Sciences (2021).
5. A Magnetic Integration Half-Turn Planar Transformer and its Analysis for LLC Resonant DC-DC Converters. IEEE Access (2019).
6. Optimal Design of a High Efficiency LLC Resonant Converter with a Narrow Frequency Range for Voltage Regulation. Energies (2018).
7. Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters. IEEE Access (2021).