Abstract
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.