DC Voltage Analysis of a Single Switch Split DC-Rail Boost Converter Operated under Steady-State Unbalanced Load Conditions in Discontinuous Conduction

The 1-switch split dc-rail boost converter topology examined uses a symmetrical mutually coupled two winding inductor to balance the voltage drop across both of its capacitor smoothed input and output dc voltage terminals. The converter can regulate its two input and output voltages even under extreme unbalanced load conditions. Analysis of the converter current waveforms is presented to determine how the steady state dc voltage drops across the capacitors changes as a function of the output load imbalance. The analysis identifies that the inductor winding leakage inductance, diode reverse recovery currents and device voltage drops are key factors in determining the range of dc voltage fluctuations experienced. Theoretical predictions are confirmed using simulation and experimental results. This analysis also demonstrates how a simple diode RC snubber can be used to lower the dc voltage changes with the load imbalance.