UC San Diego

The continual increase in performance and feature densities of small form factor mobile products has driven the need for high-capacity batteries and thus battery charger solutions with higher power-delivery densities to meet the demand for reduced charging times. The USB- C power delivery specification was developed to meet these higher demands by providing a programmable VBUS voltage range of 5–20 V with up to 100 W of power delivery, which serves as the input voltage (VIN) for the battery charger. A DC-DC converter that efficiently takes advantage of this wide VIN range while providing an output voltage (VO) range suitable for battery charging (e.g. 2.8V–4.2V) is challenging but highly desirable for space constrained products.

Hybrid converters provide a path to meet these challenges by leveraging the benefits of both switched-capacitor (SC) and switched-inductor (SI) techniques to reduce inductor size and efficiently provide high VIN⁄VO voltage conversion ratios (VCRs). The former is important since inductors have substantially lower energy storage densities compared to modern capacitor technologies. Therefore, inductors tend to be the largest occupiers of board space and bill-of- material cost out of all the converter passives. Additionally, die-level or package-level integration of high quality inductors can be challenging when compared to capacitors.This work intends to address these challenges by introducing new hybrid converter topologies that reduce the energy processing required by the inductor while still achieving the VCRs needed to take advantage of the benefits offered by higher VIN charging. This reduces the reliance on large, high quality inductors to maintain high power efficiency. The first part of this dissertation provides background regarding charge-based converter analysis. The next part presents a flying inductor hybrid topology that relocates the inductor from the high output current location to lower input current location while providing multiple outputs for 1-cell and 2-cell charging. The last part presents a single inductor multi-stage hybrid converter that utilizes an inductor to couple two SC stages to provide soft-charging benefits to each stage while leveraging reconfiguration to efficiently provide a wide range of VCRs.