Design Analysis And Research On Planar Transformer With Bulk Metallic-Glass-Alloyed Core

In view of the two problems in designing planar transformers:one is that people mostly focus on the special winding structures and ignore transformer cores when they design planar transformer; the other problem is that it is difficult to standardize planar transformer because planar transformers have special structure and small unit capacity. Therefore, this paper proposes to solve the problems by means of manufacturing bulk amorphous alloy cores to optimize the planar transformer design.First, the author introduces the technology of computing the value of an electric field, and creates the formula that express the dynamic capacitance, the leakage inductance, the optimum winding-layer spacing and the window-filling factor for planar transformer as well as the winding-layer structure with low energy loss for planar transformer. This has effectively solved the problem of how to achieve the low energy loss when designing the winding-layer structure of planar transformer. Thus, from the perspective of optimizing the design and manufacture of high-frequency planar transformer, the findings have significant value in theory and in practice.Secondly, the key to the design of planar transformer is to minimize the total loss of the planar transformer, and thus it requires effective suppression of the planar transformer leakage inductance and distributed capacitance, the effect of which is to reduce the leakage inductance energy and distributed capacitance energy. Low loss single-layer radial winding structure makes the dynamic distributed capacitance of the transformer reach approximately zero. Because the leakage inductance of the transformer is conducted by winding itself only, the leakage inductance can be decreased by increasing the winding width and decreasing the winding height. The BMG planar transformer with mono-layer radial winding structure has a good performance, but its power capacity is small, so it is difficult to use as a large power transformer. Therefore, by means of the multi-layer circuit board (PCB) with low loss single-layer radial winding structure, a new parallel connection way is adopted to single planar radial winding as a new BMG planar transformer module to solve the problems with the small power capacity and large current of the transformer.Third, considering the best winding structure is acquired by designing the planar transformer structure, a modular design method is presented to fix the problems concerning the complicated topology structure, the small unit transformer capacity, the highly product cost and the difficulty in standardizing planar transformer. In this way, the bottlenecks of planar transformer designing are resolved and the prospects of the planar transformer application are broadened.Finally, in order to meet the requirements of the parallel radial winding planar transformer module performance and structural features, study and explore how to design the core to optimal the the radial winding planar transformer module performance and structure, the conclusion can be drawn:For the parallel radial winding planar transformer module, increasing operating frequency and decreasing core loss is an effective way to improve power transmit efficiency of the parallel radial winding planar transformer module, besides, increasing the resistivity of the core material is an effective way to reduce parallel radial winding eddy current loss. From the material microstructure, the resistivity of the core material can be increased with the uniform small grains, the grain boundary and the grain in the same resistance, while conventional magnetic core material such as silicon steel can not meet the requirements of parallel radial winding planar transformer, therefore, this paper attempts to find a core material with high resistivity and low eddy current losses to meet the requirements of parallel radial winding planar transformer module, the study found that Fe-base bulk metallic glasses alloy have not only high resistivity but also low eddy current losses, it is very suitable as the core material of parallel radial winding planar transformer module as it have excellent soft magnetic properties. Meanwhile, by’using the raw materials include industrial pure Fe and industrial Fe-B alloy, BMG alloys with a maximum diameter of5mm are synthesized with Zr substitution for Nb and Co substitution for Fe. Thus demonstrated the soft magnetic properties and the glass forming ability enhanced for the(Fe71.2B24Y4.8)96Nb4. Meanwhile, amorphous alloy series [(Fe1-xCox)71.2B24Y4.8]96Nb4(x=0-0.4) and (Fe71.2B24Y4.8)96Nb4-xZrx (x=0-4) are developed as transformer core material. In addition, the design methods are analyses for the conventional planar transformers and parallel radial winding planar transformer modules, including the core material, the core structure, the core parameters, the coil parameters, assembled structure and the temperature rise checking, etc.