Fully Integrated Wide Input V oltage Range Capacitive DC-DC Converters: The Folding

Abstract

This paper presents a modified Dickson converter to achieve wide input range capacitive DC-DC converters. Several implementations are carefully studied and compared, which shows that the folding Dickson converter is the best choice, not only for its reduced dynamic losses, but also for its very regular structure and operation. Folding is achieved by merging the terminals of two or more flying capacitors, creating one equivalent flying ca- pacitor. In this design, a four stage folding Dickson converter is implemented to achieve four diffe rent voltage conversion ratios. A Bootstrapped Gate Boost Conve rter (BGBC) is proposed which uses a bootstrapping technique to generate a floating rail for the flying switches, whose terminal voltages vary by large amounts de- pending on input voltage and VCR. The inherent operation of the Dickson topology is used by copying the voltage of the flying capac- itors on a grounded capacitor in one phase, which can then be used to generate a floating 1.2 V in the second phase. The converter has been implemented in a 90 nm technology, achieving a maximum output power of 50 mW, peak efficiency of 76.6% in the 2:1 con- version mode, and an average ef ficiency above 60% over the entire Vin and Pout range.