Theoretical and Experimental Investigation of the Voltage Ripple across Flying Capacitors in the Interleaved Buck Converter with Extended Duty Cycle

Resumen

The interleaved buck converter with an extended duty cycle is analyzed in terms of unexplored parasitic switching states that diminish the switch utilization and its safety due to high-magnitude charging and discharging currents. The analysis explains the origin of the states and their effects and demonstrates their correlation with the existing voltage ripple on flying capacitors. The article further demonstrates that the voltage ripple can no longer be arbitrarily chosen as parasitic states emerge whenever the ripple exceeds an identified critical value being equal to the twofold voltage drop on the diode. A simple design criterion for flying capacitance is proposed. For a limited set of battery-powered DC–DC converters, a solution permitting the use of smaller capacitance by adding an extra switch is proposed. The derived findings are verified using experimental and simulation results.