A charge recycling method for step-down SC converter in energy harvesting systems

Energy harvesting systems stimulate the development of power management for low power consumption applications. Intermittent operation mode, as a low power working mode for such kinds of applications, plays a very important role. Switching capacitors are widely used in this kind of operation mode due to its less external components, easily integrated capacitors, less electromagnetic interference (EMI), etc. There are two kinds of power loss in the working process of switching capacitor (SC) DC-DC converter, conduction loss and switching loss. Due to special application backgrounds in low power application, output power of SC DC-DC converter becomes smaller, so switching loss accounts an increasing proportion. A lot of papers focusing on energy recycling have been published in the past recent years. In order to increase the converter efficiency of step-down DC-DC converter, a novel gate charge recycle method is proposed, clock generator and bandgap reference circuits have also been presented. Comparing to the traditional circuit topology, several switching transistors are added and die area will be increased, but converter efficiency will be improved more than 20% according to the simulation results.