High-Frequency LLC Resonant Converter with GaN Devices and Integrated Magnetics

Yu-Chen Liu,Yong-Long Syu,Chen Chen,Meng-Chi Tsai,Kai-De Chen

doi:10.3390/en12091781

Abstract

In this study, a light emitting diode (LED) driver containing an integrated transformer with adjustable leakage inductance in a high-frequency isolated LLC resonant converter was proposed as an LED lighting power converter. The primary- and secondary-side topological structures were analyzed from the perspectives of component loss and component stress, and a full-bridge structure was selected for both the primary- and secondary-side circuit architecture of the LLC resonant converter. Additionally, to achieve high power density and high efficiency, adjustable leakage inductance was achieved through an additional reluctance length, and the added resonant inductor was replaced with the transformer leakage inductance without increasing the amount of loss caused by the proximity effect. To optimize the transformer, the number of primary- and secondary-side windings that resulted in the lowest core loss and copper loss was selected, and the feasibility of the new core design was verified using ANSYS Maxwell software. Finally, this paper proposes an integrated transformer without any additional resonant inductor in the LLC resonant converter. Transformer loss is optimized by adjusting parameters of the core structure and the winding arrangement. An LLC resonant converter with a 400 V input voltage, 300 V output voltage, 1 kW output power, and 500 kHz switching frequency was created, and a maximum efficiency of 97.03% was achieved. The component with the highest temperature was the transformer winding, which reached 78.6 °C at full load.

Highlights

Light emitting diode (LED) lighting has become more popular in recent years, as product energy efficiency has become more important to consumers [1,2,3]
This study study determined determined the the primary-side primary-side topology topology and and secondary-side secondary-side rectification rectification topology topology suitable for an resonant converter under a switching frequency, input voltage, and output suitable for an LLC resonant converter under a switching frequency, input voltage, and voltage output of
After loss and determining the rated current thecurrent components, the full-bridgethe topology was topology selected for both the primary and secondary voltage of and of the components, full-bridge was selected for both the primary sides

Summary

Introduction

Light emitting diode (LED) lighting has become more popular in recent years, as product energy efficiency has become more important to consumers [1,2,3]. LEDs have been used in various lighting scenarios, such as street lighting, indoor lighting, and backlighting They have been used for lighting equipment with high power requirements, like baseball field or basketball court lights. Most of these LED driver circuits have a two-stage architecture consisting of a power factor correction converter in the first stage and an isolated buck converter in the second stage, with an LLC resonant converter usually employed as the second-stage circuit [4,5]. Unlike other common isolated buck converters, an LLC resonant converter is characterized by power components with zero voltage switching (ZVS) and zero current switching at the high—and low—voltage ends, respectively, in a full load range. Unlike phase-shifted full-bridge converters, an LLC converter has no output inductance at the low-voltage end and has higher

Methods

Results

Conclusion