Stacked switched capacitor energy buffer architecture

Electrolytic capacitors are often used for energy buffering applications, including buffering between single-phase ac and dc. While these capacitors have high energy density compared to film and ceramic capacitors, their life is limited and their reliability is a major concern. This paper presents a stacked switched capacitor (SSC) energy buffer architecture and some of its topological embodiments which overcome this limitation while achieving comparable effective energy density without electrolytic capacitors. The architectural approach is introduced along with design and control techniques. A prototype SSC energy buffer using film capacitors, designed for a 320 V dc bus and able to support a 135 W load has been built and tested with a power factor correction circuit. It demonstrates the effectiveness of the approach.