當設計電源轉換器朝著降低成本與面積的目標邁進，切換模式的電源轉換器可以增加功率密度，但是切換式電源的面積限制於被動元件的尺寸，而被動元件的面積與切換頻率有關係。當切換頻率越高，被動元件的尺寸越小，所以可以藉由增加頻率以降低切換式電源轉換器的面積。
本論文中，完成三個Class Phi直流電源轉換器，其切換頻率為240MHz，總面積小於60 mm2，體積約為51.75mm2，最大量測轉換效率為52.5%，量測輸出最大功率為2.08W，實現了用覆晶植金球的去做異質晶片整合，其為CMOS閘級驅動電路、GaN功率元件與IPD被動元件利用覆晶技術組合在一起，不同於一般諧振式最常見的傳統Class E架構，一種新的Class Phi架構被實做積體化出來，Class Phi架構比Class E在高頻且電感積體化的條件下，可以達到更低的損耗與更高的效率，最主要的原因是Class Phi汲極與源極的跨壓小於Class E，所以電感損耗可以大幅降低，同時，此電源轉換器會使用到的切換開關電晶體和二極體等主動元件的使用皆為新穎的氮化鎵材料，原因為氮化鎵元件有較高的電子遷移率，其特性適合拿來當作開關，第二個為有較高的耐壓，其特性適合拿來當作解決諧振式轉換器需跨壓高的難題。
第二章介紹的氮化鎵元件的特性與適用於高頻與高壓的原因。第三章介紹三種諧振式電源轉換器的電路原理與比較。在第四章中，三種Class Phi電源轉換器的設計概念與量測結果被呈現。

The research in power electronic for reducing size and improving efficiency is the trend in recent years. Higher frequency can reduce the size of passive components and increase the switching loss. However, a trade-off in general exists between chip size and efficiency. The switch loss will increase and also become significant at high frequencies. Therefore, there is a demand for the resonant inverter type of dc-dc power converter. The resonant inverter is very similar to RF switched type PA using the concept of soft switch.
In this thesis, we demonstrate a 240MHz resonant Class Phi GaN DC-DC converter. The total maximum efficiency of the circuit is 52.5%, total chip size is 51.76 mm2, the maximum output power is 2.08W, and the switching frequency is 240MHz. The largest inductor employed is only 12.9nH owing to the class Phi topology. The inverter chain is used for the gate driver by TSMC 0.18-μm CMOS. The power switch and rectifier are fabricated in WIN GaN 0.25-μm HEMT technology. All the passive devices are fabricated by the IPD (Integrated Passive Device) process. We combine CMOS and GaN chips by flip-chip bonding technology in IPD substrate including inductors and capacitances.
In chapter 2, the characteristics of GaN device and the suitability for high frequency and high voltage stress are discussed. In Chapter 3, three resonant inverters are presented and compared. In Chapter 4, the principle of class phi converter and measurement results are presented. Chapter 5 shows the future work and conclusions.

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