Innovation of Switched-Capacitor Voltage Multiplier: Part 1: A Brief History

The switched-capacitor (SC) voltage multiplier is becoming one of the most critical IC blocks for energy harvesting in wireless sensor nodes to generate a voltage high enough for microwatt sensing and computing ICs in a nanometer complementary metal?oxide?semiconductor (CMOS) from environmental energy sources such as mechanical vibration, electromagnetic wave, and temperature gradient. However, its origin was a 10 m-scale particle accelerator generating 1 MV back to 1920s. There have been several innovative design techniques to realize integrated SC voltage multipliers since the original one. This article overviews such innovations for the last century and describes how 10 m-scale SC voltage multipliers have been integrated in microwatt ICs and what technical considerations are critical for area- and power-efficient design. It also summarizes how device parameters determine circuit performance such as output voltage current and power efficiency. There have been also several design innovations in switching circuits to enable to work at extremely low voltages. This article shows state of the art for switching circuits for both dc-dc and ac-dc voltage multipliers and their applications as well.