MS student Benjamin Macy with advisor R. Pilawa-Podgurski
There has been a renewed interest in switched-capacitor converters (SCC) because they can achieve high-voltage conversion ratios, small size, and IC integration. SCCs can have high power densities through the elimination or reduction of magnetic components and the relatively high energy density of capacitors compared to inductors. However, efficiency can be poor if voltage sources or capacitors charge other capacitors (resulting in slow switching losses) or if the converter is operating at high frequency (resulting in switching losses). Our work over the past year and a half utilizes resonant structures to achieve zero current switching and soft charging in SC converters. The techniques employed can be utilized to mitigate slow switching losses and switching losses in a Dickson SC converter. Moreover, the split-phase control scheme is used to further reduce slow switching losses by ensuring zero voltage switching. The converter shown in Figure 26 has attained 1.47 kW/ in3 power density. The 1:4 fixed conversion ratio accepts up to a 25 V input and has a nominal output voltage of 100 V at up to 105 W. It is very small due to the high energy density of capacitors and the high switching frequency enabled by using a SC topology. This work was made possible due to funding through the Grainger Foundation and Google.

Figure 26: Converter with 1.47 kW/ in3 power density

Figure 26: Converter with 1.47 kW/ in3 power density