Nonlinear variable frequency control of high power switched-capacitor converter

Switched-capacitor (SC) converters are a type of variable structure systems. In the past, most of the SC converters were initially introduced for the low power applications and monolithic integration. Recently, SC converters have been used in high power area with the open-loop control and some other simple linear voltage feedback controls. However, the simplicity of such approaches sacrifice performance with the slow dynamic response, narrow operation region and large voltage ripple. Some new nonlinear control methods have been proposed, however, such control methods are only useful for applications involving low power SC converter. This paper proposed a new nonlinear constant on time variable frequency control (COTVF) based on the capacitor ampere-second balance principle. The proposed variable frequency control method successfully addresses the regulation issue in high power SC converters. The control concept is straightforward yet with excellent performance. In combination with the high power 2X two-switch boosting switched-capacitor (TBSC) converter, simulation results demonstrate that the proposed control method highly improve the dynamic response speed with good line and load regulation in wide operation range.