Intermediate bus architecture employing 48-V bus converters is widely used in power supply applications. With the rapid increase of demanded power by these loads, higher efficiency and power density are driving better performance power management solutions. In this article, a Gallium Nitride (GaN) based design of a two-stage solution is proposed. The first stage is a multi-phase Buck for regulation. The second stage is an LLC converter with a fixed switching frequency for isolation. The detailed design and optimization of the LLC converter are studied. To achieve high power density and high efficiency, the transformer design becomes critical at megahertz frequency. The matrix transformer concept is applied and a merged winding structure is used for flux cancellation, which effectively reduces the ac winding losses. A novel primary termination and via structure is proposed, resulting in a great loss reduction. In addition, to study the current sharing of parallel winding layers, a 1-D analytic model is proposed, and a symmetrical winding layer scheme is used to balance the current distribution. Finally, the prototype for the two-stage bus converter is developed, with a peak efficiency of 96% and a power density of 615 W/in ³ .

中文翻译：

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兆赫兹的优化设计 $ LLC $ 适用于48V总线转换器应用的转换器

采用48V总线转换器的中间总线架构已广泛用于电源应用中。随着这些负载对所需功率的快速增加，更高的效率和功率密度正在推动性能更好的电源管理解决方案。在本文中，提出了基于氮化镓（GaN）的两阶段解决方案的设计。第一级是用于调节的多相降压。第二级是具有固定隔离开关频率的LLC转换器。研究了LLC转换器的详细设计和优化。为了实现高功率密度和高效率，变压器设计在兆赫兹频率下变得至关重要。应用矩阵变压器的概念，并使用合并的绕组结构来消除磁通，从而有效地减少了交流绕组损耗。提出了一种新颖的初级端接和通孔结构，从而大大降低了损耗。此外，为了研究并联绕组层的电流共享，提出了一种一维解析模型，并使用对称绕组层方案来平衡电流分布。最后，开发出了两级总线转换器的原型，其峰值效率为96％，功率密度为615 W / in ³ 。