AC-Coupled Stacked Dual-Active-Bridge DC–DC Converter for Integrated Lithium-Ion Battery Power Delivery

Abstract

Mobile, wearable, and Internet-of-Things (IOT) electronic systems are typically powered by a single-cell lithium-ion (Li-ion) battery. Increasing demand for battery life and the constraint of the overall platform size impose an emerging desire for an efficient and compact power conversion stage that can directly deliver power from the battery, which ranges from 3.2 to 4.2 V, to the supplies of application/communication processors in the range of 1 V. The switched capacitor (SC) converter, though promising in some ways for this application, is inefficient at voltage regulation and is limited in capacitor utilization. This paper presents a hybrid dc–dc converter topology that eliminates charge sharing losses with a small inductor. The necessary inductance can be realized by PCB traces, which shows the potential for a compact system-in-package (SiP) solution. The designed converter is implemented in Texas Instruments’ 0.15- $\mu \text{m}$ CMOS process with a nominal 3:1 conversion ratio. It supports a 3.2–4.2-V input voltage with a continuous output regulation of 0.8–1.5 V. The peak efficiency is 87.2% with 83.4% efficiency at a power density of 0.46 W/mm2. This paper also presents an effective methodology of developing the large-signal model and small-signal dynamics for the generalized N:1 converter topology. A tight load line-based controller is integrated into the designed chip and experimentally verified with a transient performance of 50-mV voltage overshoot/undershoot under 400-mA on-die load step.