High-Performance Switched-Capacitor Boost–Buck Integrated Power Converters

This paper presents the design of integrated boost and buck switched-capacitor power converters with high efficiency and fast start-up time. An analysis method is determined to evaluate the key performance parameters of integrated power converters, and techniques are proposed to improve the energy conversion efficiency and the dynamic response. Boost and buck structures are modeled and compared in static and transient conditions, including the losses due to parasitic elements. A switch bootstrapping technique prevents short-circuit losses, improves driving capability and start-up time, and enhances the overall efficiency. Moreover, the application of a charge-reuse technique reduces the dynamic power losses of the integrated structures. Prototypes of the integrated power converters were fabricated in a 180-nm CMOS process. Measurement results based on the proposed techniques are presented, demonstrating the improvements in steady-state and transient characteristics with a good correlation between measured and predicted results.

I. Introduction

Performance improvement together with the reduction of overall system cost, size, and power have been the main force driving the integration of analog, digital, and radio-frequency functions onto a single die. Technology scaling, which is primarily driven by digital circuits, requires reducing the supply voltage to address power and reliability constraints, while other functions are implemented more efficiently using higher voltages. Moreover, modern microsystems in applications such as smart cards, mobile health care, and Internet-of-things devices are readily integrated by a system designer if they operate from a single supply. However, such supply is often fed from unsteady sources like batteries and energy harvesters. Hence, fully integrated power converters are necessary to interface sources directly while efficiently catering to the voltage requirements of the different functions.