A switched-capacitor based embedded DC-DC buck converter for high power efficiency and high power density

Abstract

In this paper we propose a controlled cross-coupled switched-capacitor based embedded DC-DC buck converter based on non-overlapping rotational time interleaving switching scheme and frequency control regulation. Proposed converter uses low swing internal signals to control half of the switches. In addition to reduction of switching power loss, the low swing control signals help to use smaller switches and reduce power loss in the converter. The non-overlapping rotational time interleaving switching scheme helps to eliminate shoot through loss during switching transition and improve power efficiency further. In addition, output ripple noise is reduced by this switching scheme. On the other hand frequency control regulation helps to maintain high power efficiency over a wide range of load current. Proposed converter is implemented in 0.18 μm CMOS process to get 1.3 V-1.6 V regulated output from 3.3 V input supply. Peak power efficiency of the converter is 87% while power density is 0.5Watt/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for 79% power efficiency. Output ripple is 8 mV for 25 mA load current for 1.35 V regulated output.