Fully integrated dc-dc converters with basic and double galvanic isolation

The increasing demand of low-profile power converters in modern electronic devices has pushed research towards integrated systems able to replace expensive and bulky solutions based on discrete components. Consequently, galvanically isolated interfaces are becoming an interesting research topic for both industry and academia, since integrated systems performing power and/or data transfer through a galvanic isolation barrier are largely demanded in a wide range of applications, which are growing rapidly during the last few years.Galvanic isolation can be required for several reasons, e.g. to ensure the proper function of a system, to preserve sensitive circuits from damages or to guarantee safety of human beings. In this context increasing levels of galvanic isolation have been defined by regional and international bodies. A fully integrated power transfer system with on-chip basic galvanic isolation will be presented in Chapter 1. Specifically, it is a 300-mW step-up dc-dc converter for gate driver's power supply applications, exploiting a CMOS-based circuit topology. Indeed, the design of galvanically isolated power transfer systems is not a trivial task due to the highly non-linear interactions between building blocks. It requires an accurate evaluation of on-chip and off-chip parasitics, modeling of passive devices along with a customized co-design procedure to pursue maximization of performance. To this aim, a novel lumped, scalable modelling for three-winding integrated transformers with tapped primary coils has been developed. The analysis and design of a 100-mW dc-dc converter with double galvanic isolation will be the object of Chapter 3. Currently, only data isolators performing on-chip double isolation are available in the state-of-the-art, whereas power transfer is still hindered by low efficiencies of series-connected integrated isolation transformers. A novel circuit architecture will be proposed, achieving an efficient power transfer across a double isolation barrier thanks to a resonant mode operation between system's blocks. Finally, an innovative PWM control loop performing output power/voltage regulation will be presented. At the authors' best knowledge this is the very first fully integrated and double isolated dc-dc converter with integrated output voltage regulation, among previously published works.