Single-inductor dual-output DC-DC converter with multiple flying capacitors

Abstract

Over the past years, there has been extensive research in the literature to develop more robust converter designs in terms of area and efficiency. Owing to their high efficiency operation, DC-DC converters have been an essential role in power management integrated circuits (PMICs). In the application of portable devices, the power management system supplies voltage to the different circuits therefore, the power management system requires the need to provide different output voltage levels with high efficiency. One of the most important specifications of DC-DC converters is efficiency, which is the measure of how much power is dissipated by the converter, without being delivered to the output. In the context of mass production, the cost of the components plays a massive role, considering inductors and capacitors. They should not occupy large areas in the system in order not to increase development and production costs. In the literature and in the market, converters using single power inductors to generate dual outputs have been presented. They are so-called Single-Inductor Dual-Output(SIDO) DC-DC converters. SIDO converter is able to support double output based on the application, having only one inductor which significantly relaxes the board area constraints and development costs. Therefore, SIDO converters have been seen in the market as cost-effective, taking the attention of most manufacturers with various applications in portable devices. The thesis focuses on improving SIDO DC-DC converter efficiency and relaxing coil constraints. This thesis presents a novel Single-Inductor Dual-Output (SIDO) DC-DC converter topology with two flying capacitors. The two flying capacitors are located in the same current path, targeting an enhanced voltage drop reduction on the inductor, and a decrease in the inductor current slope, aiming for improved power efficiency and relaxed coil current constraints. For the completeness of the work and to show improvements compared to previous designs that are present in the literature, conventional SIDO topology, the SIDO topology with one flying capacitor, and the proposed SIDO converter with two flying capacitors have been simulated. The efficiency results include all possible loss contributors, as well as core loss caused by the inductor. The core loss estimation method is also used in this work to model magnetic losses that are contributed by the inductor. The method estimates the B-H loop with a proper model of the inductor according to the core parameters of the coil. The core loss estimation method also considers the difference between the operation mode of the converter and gives more accurate core loss data.