Design of Inductor-Based High-Switching Frequency Step-Down DC-DC Power Converters
Date Issued
2016
Date
2016
Author(s)
Wu, Cheng-Hui
Abstract
Power management IC (PMIC) is a critical building block in integrated circuits for providing stable supply voltages, which ideally don’t change with the battery voltage and the output load current. However, due to the limited area, large inductors and capacitors used in the PMICs are not preferred in modern portable devices. In this thesis, two compact dc-dc power converters are proposed to minimize the off-chip component sizes with different controller types. In the first work, an inductor-based high-switching frequency current-controlled step-down dc-dc power converter is proposed to reduce the off-chip component sizes. With the inherent one pole characteristic, only one additional off-chip capacitor is used. The slew-rate enhanced g_m stage is designed to improve the transient response by 30X faster while the soft-start circuit is employed to prevent ambiguity when circuit turns on. Operating at 20 MHz switching frequency, a compact dc-dc power converter is realized with 240 nH inductor and 220 nF capacitor and the power conversion efficiency is as high as 73.5 %. In the second work, an inductor-based high-switching frequency digital-controlled step-down dc-dc power converter with weighted delay-line DPWM is proposed to further reduce the off-chip component sizes. A 4-bit window-flash ADC is employed to save 87.5 % of the power and area and minimize the ADC latency. Meanwhile, the proposed weighted delay-line DPWM successfully converts the digital code into time-domain duty cycle information without the redundant 64-to-1 MUX. Operating at 50 MHz switching frequency, a compact dc-dc power converter is realized with 100 nH inductor and 100 nF capacitor and the power conversion efficiency is over 80 % for load current ranges from 350 mA to 550 mA.
Subjects
high-switching frequency
DC-DC
power converter
buck
Type
thesis