Integrated Very High Frequency Switch Mode Power Supplies: Design Considerations

Abstract

This paper presents a power supply using an increased switching frequency to minimize the size of energy storing components, thereby addressing the demands for increased power densities in power supplies. 100 MHz and higher switching frequencies have been used in resonant power converters, which along with the possible integration of passive components on silicon wafer, present a beneficial solution in applications such as mobile phones. This paper presents a design for a 9 W class E resonant power converter in an 0.18 µm CMOS process. The converter is driven by a self oscillating gate drive, which is presented in an in-depth mathematical analysis. The gate resistance of the designed transistors is of critical importance in order to achieve the correct phase shift required for zero-voltageswitching. The Z-parameter method is used to characterize the transistors which is verified through simulations. The required spiral inductors was modeled, and simulations show Q values of as high as 14 at a switching frequency of 250 MHz. Simulations of the converter show an efficiency of 55 % with a self oscillating gate drive. However the modeled inductor was not adequate for operating with the self oscillating gate drive, presenting a future challenge for power supplies on chip