Integrated Very-High-Frequency Switch Mode Power Supplies: Design Considerations

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, and 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 a 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 voltage switching. The Z-parameter method is used to characterize the transistors, which is verified through simulations. The required spiral inductors were 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.