1．目的及意义
The power supply unit (PSU) is an essential part of any electronic device as no electronic circuit can function without some sort of power. The ever increasing demand for slim and portable consumer electronic appliances such as laptop adapters, palmtop computers, LCD monitors, mobile and iPad chargers highlight the significance of the low profile low power converters [1]. In this regard, power electronics researchers and engineers are continuously striving to design small size, lightweight, low profile, small foot print and energy efficient converters [2], [3]. In order to achieve this task, the switching frequency of the converters has to be increased so that the size of the passive elements such as inductors, transformers and capacitors [4] - [10] gets reduced as it is required to store a lesser amount of energy in each cycle. In addition to this, by integrating the passive elements in the converter circuit, it is feasible to realize the high power density converters [9]. The majority of power electronic converter circuits employ the inductors and transformers, which are defined by their electromagnetic behavior. One of the design challenges in relation to achieving the high power density converters is the design and development of high power density magnetics (either inductor or transformers), which are usually considered as the bulkiest [10] and most expensive components in switch mode power supplies (SMPS). In a typical SMPS, the magnetics together with the heat sinks are considered to be occupying more than 80% of the total volume [11] when compared to other elements. However, the most irreplaceable components in the SMPS are considered as the magnetic elements i.e., the inductors and transformers. For example, if the non-isolated converters such as buck, boost, buck-boost and cuk converters are considered, then the inductor is one of the essential parts, in addition to the other elements of the circuit. Similarly, in the case of single/double ended isolated converter topologies such as forward, flyback, half-bridge and full-bridge converters, transformer becomes the backbone as it provides the galvanic isolation, large step down/step up conversion ratios and multiple outputs [12]. On the other hand, these are considered as complex components in terms of design, but at the same time, these have become the heart of the modern SMPS. From the semiconductor point of view, the state-of-the-art ‘Si’ material switching devices are reaching the theoretical limits in terms of performance and reliability [13], in order to meet the current industrial demands of achieving energy efficient high power density converters [14]. In this regard, the new semiconductor material devices such as silicon carbide (SiC) schottky diodes/transistors [15] and gallium nitride high electron mobility transistors (GaN HEMTs) [16] have been introduced into the market, which makes it feasible to increase the switching
frequency of converters from a few hundred kHz to the MHz frequency region
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2. 研究的基本内容与方案

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This thesis discusses a new design of acompact planar transformer. Symmetrically adjusted primary and secondary coilsare fit into the engraved surface of ferrite plate and covered with anotherferrite plate. Such a compact design decreases the thickness of a transformerin comparison with transformers which use E-cores or transformers where twoferrite plates wedge PCB with printed windings.

This project goals are to design and constructa Low-voltage large-current planar transformer ，Can effectively solve that problem of volume and high frequency, andis an important component of switch power supply and lithium battery charger.，with input 200v , output 25 v and with power 2kw

3. 参考文献

[1] Lee, C.K.; Su, Y.P.; Hui, S.Y.R., "Printed Spiral Winding Inductor with Wide Frequency Bandwidth," Power Electronics, IEEE Transactions on, vol.26, no.10, pp.2936, 2945, Oct. 2011.

[2] Erkmen, B.; Demirel, I., "A Very Low Profile Dual Output LLC Resonant Converter for LCD/LED TV Applications," Power Electronics, IEEE Transactions on, vol.PP, no.99, pp.1, 1, 0.

[3] Oeder, C., "Analysis and design of a low-profile LLC converter," Industrial Electronics (ISIE), 2010 IEEE International Symposium on, vol., no., pp.3859, 3864, 4-7 July 2010.

[4] Wong, Fu Keung, “High Frequency transformers for switch mode power supplies’’, PhD thesis, Griffith University, 2004.

[5] Glaser, J.S.; Rivas, J.M.; , "A 500 W push-pull dc-dc power converter with a 30 MHz switching frequency," Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE , vol., no., pp.654–661, 21– 25 Feb. 2010.

[6] Quinn, C.; Rinne, K.; O'Donnell, T.; Duffy, M.; Mathuna, C.O.;, "A review of planar magnetic techniques and technologies," Applied Power Electronics Conference and Exposition, 2001. APEC 2001. Sixteenth Annual IEEE, vol.2, no., pp.1175-1183 vol.2, 2001.

[7] Katayama, Y.; Sugahara, S.; Nakazawa, H.; Edo, M.; "High-power-density MHz-switching monolithic DC-DC converter with thin-film inductor," Power Electronics Specialists Conference 2000. PESC 00. 2000 IEEE 31st Annual, vol.3, no., pp.1485–1490.

[8] Perreault, D.J.; Jingying Hu; Rivas, J.M.; Yehui Han; Leitermann, O.; PilawaPodgurski, R.C.N.; Sagneri, A.; Sullivan, C.R., "Opportunities and Challenges in Very High Frequency Power Conversion," Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE, vol., no., pp.1, 14, 15-19 Feb. 2009.