Design of an integrated magnetics structure for LLC resonant converter

Abstract

This paper, we propose IM (Integrated Magnetics) structure for LLC resonant converter. The IM technique can combine several components into one magnetic core, plus, utilizing a planar magnetic core is a suitable device to achieve high power density. Therefore, it can achieve high power density in Switch Mode Power Supply (SMPS) because the total volume is almost determined by the magnetic components. However, when adopting a planar magnetic core in LLC resonant converter, it is difficult to attain enough resonant inductance due to high coupling characteristics. This leads to using an additional inductor as a resonant inductor, thus, the total power density is decreased. To overcome this limitation, the proposed structure uses magnetizing inductances as resonant inductor so that all resonant parameters can be made equally in one magnetic core. Therefore, high power density can be achieved. Moreover, optimal design can be achieved easily because all of the resonant parameters are controllable. To verify the validity of the proposed structure, a magnetic analysis and an efficiency comparison are discussed, then, experimental results of 350W half bridge prototype are presented.