A High Efficiency Δ-Lr-Y Type Three-Phase Interleaved <i>LLC</i> Converter With Less Transformer Loss
Jiajia Guan, Zongheng Wu, Teng Liu, Jin Wen, Wenzhe Xu, Cai Chen, Yong Kang
Abstract
Y-type three-phase interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> has advantages in high-power applications with small output current ripple. However, the traditional Y-type three-phase interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> has large winding current under low output voltage and high-power applications, which affects the efficiency and power density. In this article, a high-efficiency delta-type three-phase interleaved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> topology with less transformer losses was proposed. This article verifies that the transformer loss of the proposed topology is lower than that of the traditional Y-type topology based on the loss model and simulation. Furthermore, considering the coupling between three-phase transformers, a more accurate soft-switching analysis method and the first harmonic gain formula of the proposed topology are given. According to the analysis results, compared with the traditional Y-type topology, only half of the magnetizing current was needed to achieve soft switching. Meanwhile, the length of the transformer air gap is one-third of the traditional Y-type topology, which can reduce the fringing loss. Finally, a 3-kW prototype was designed and verified. Compared with the Y-type, this article achieves 19.2% loss reduction.