Development of High-Frequency DC-DC Converters for Advanced Post-Regulation Automotive Applications

In many application scenarios, including IoT and automotive, there is a steadily growing trend toward integrating switch-mode power supplies (SMPS) to enhance overall system power efficiency, improve dynamic response while achieving higher compactness, and ultimately reduce cost. In this context, recent research has devoted particular attention both to topological investigations — seeking promising structural solutions that favor compactness and high performance — and to design techniques that enable high operating frequencies, which are known to allow the miniaturization of otherwise bulky and costly passive components, often representing the primary barrier to the integration of these systems. This thesis focuses on an automotive post-regulation domain application, in which a dc-dc step-down conversion is required to cover a wide input range (2.7-4.3 V) and provide an output voltage in the range (0.7-1.2 V), while handling considerable load currents values, from 1 to 3 A. The application analysis, combined with a topological investigation, leads to the selection of a dual-path step-down topology, which is particularly promising thanks to several benefits: reduced voltage stress on the power switches; reduced reliance on the inductor, which can be miniaturized; and the use of a self-balancing flying capacitor that does not require dedicated control schemes, thereby enabling high circuit simplicity. A detailed analysis of this converter is presented, covering both steady-state behavior — with an analytical description of the various loss contributions — and dynamic behavior, which are exploited for the design of the power stage and the controller, respectively. Finally, the benefits of the topology are demonstrated experimentally through a highly integrated prototype fabricated in 130 nm CMOS technology, capable of converting an input voltage in the range 3.3 – 4.3 V down to an output voltage in the range 0.7 – 1.2 V, at a maximum power of 1.8 W. The prototype, operating at a switching frequency of 2.5 MHz, achieves a peak efficiency of 89.7 % at a load current of 500 mA, in a compact solution featuring a power density of 2.14W/mm2.