A Study of Light-Load Efficiency Improvement on Series-Resonant Converter by Applying Integrated Transformer

• Main Authors: Wen-Hsin Wang, 王雯欣
• Other Authors: Huang-Jen Chiu
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/z34mnr

碩士 === 國立臺灣科技大學 === 電子工程系 === 106 === The purpose of this thesis is to develop the research and implementation on the light-load efficiency improvement of series-resonant converters using integrated transformers. For a series-resonant converter, zero-voltage-switching on power switching devices is a common technique; besides, the power devices are increasingly improved on their operation losses. Therefore, further loss reduction on series-resonant converters has reached a bottleneck. In addition to the device losses, the major loss is resulted from the magnetic components. As a result, in order to pursue high efficiency and high power density on this kind of converters, it is an important issue to improve the magnetic components. The integrated transformer integrates multiple magnetic cores to form a single one. By using an integrated core structure, the input voltage can be shared by the multiple cores to reduce the magnetic flux density on the individual cores, thereby reducing core loss. Furthermore, by elegantly arranging the core placement, the flux cancellation is achieved to reduce the effective magnetic circuit length of the integrated transformer and also the magnetic reluctance. Not only the core loss is further reduced, the integrated transformer can possess a lower magnetizing inductance without increasing the cross-sectional area of the transformer and turns number. This feature increases the magnetizing current, making it easier for the circuit to achieve zero-voltage switching under light-load conditions. Another advantageous feature to mention is that the distributively placed windings gain more space to dissipate the generated heat and lower the transformer temperature. A series-resonant converter with a switching frequency of 325 kHz, 800 V on both input and output, and maximum load of 7.2 kW is implemented.