A Switched Capacitor Voltage Converter With Exponentially Sized Capacitor Banks for Wide Load Range

Abstract

Modern Internet-of-Things (IoT) applications need voltage converters to efficiently supply power with a small active period at various load conditions. The energy losses in such voltage converters during transitions between sleep-active can be significant, especially when the converters deviate from their optimum load conditions. The proposed Switched Capacitor (SC) converter, fully integrated on chip, incorporates Split-Capacitor Charging (SCC) and Energy Recycling (ER) techniques to minimize the energy losses during the transitions. The converter consists of multiple capacitor banks and their size increases in a binary exponential fashion. It employs an LDO to support a wide range of output voltage levels and reduce output voltage ripple during energy recycling and Continuous phase. In addition, we introduce an efficient test circuit structure using an on-chip digital controller and reconfigurable load circuit. This test structure can eliminate the unwanted parasitic values and varying delays, which are commonly incurred in the conventional test structures of on-chip voltage converters with off-chip loads and external control signal generation. We implemented the proposed voltage converter with a complete on-chip test structure using a 0.13 $\mu {\mathrm{ m}}$ CMOS process. Measurement results demonstrate a maximum efficiency of 86.83 % for a load current of $11~\mu \text{A}$ . It also achieved an improvement of 64.44 % in energy efficiency over conventional voltage converters for a short active period.