Design and Analysis of Integrated Planar Transformer for LLC Converter

Planar Magnetics is replacing conventional magnetic structures in many applications. Especially Planar transformers are good choice for applications requiring integrated magnetics. LLC converter takes advantage of the features of planar magnetics resulting in power density improvement of the converter system. This thesis deals with design of one such integrated planar transformer for LLC converter. Design flow of integrated planar magnetics is discussed in detail. The major issue of high frequency eddy current loss and achieving required leakage inductance are highlighted. The reason behind the high frequency eddy current losses due to proximity effect and skin effect are discussed and solution to address the high frequency loss are provide. It is shown that the solutions to reduce eddy current losses reduces leakage inductance which is good for converter systems where only magnetizing inductance of transformer plays vital role and the leakage inductance, a parasitic parameter causes undesired effects. For integrated transformer where we need significant leakage inductance, modifying design to include a leakage layer is shown to improve leakage without compromising losses.