Effect of Shifting Gate Pulse on CCM/DCM Boundary in Coupled SIDO Boost Converter

Abstract

The single input dual output (SIDO) converters are efficient than two single input single output (SISO) converters. The SIDO converters have reduced component count, reduced losses related to each component, and increased efficiency. The coupled inductor SIDO (CI-SIDO) boost converter is the topology of focus in this paper. The converters operate in two modes - continuous condition mode (CCM) and discontinuous conduction mode (DCM). The transition between modes occurs at the CCM/DCM boundary. The converters are operated in CCM because the control of the converter is easier in CCM. As the converter enters in DCM the output voltage becomes load dependent and control becomes complex. For the converter to operate in CCM, the average value of inductor currents should be greater than the boundary values. If the boundary currents are reduced, the converter can operate in CCM for a longer range of loads. The CI-SIDO boost converter has two gate pulses, due to the presence of two MOSFETs. The shifting of one gate pulse with respect to the starting point of another gate pulse, is used to analyze the CCM/DCM boundary. The shifting of gate pulse changes the average value of inductor currents at the boundary. The average value of inductor currents at the CCM/DCM boundary is analyzed and compared for shifted and non-shifted pulses. The analytical expressions of the average value of inductor currents at the boundary are calculated for the shifted pulse. The analysis considers all possible values of duty ratios and inductor current slopes. The analysis is verified by simulations in MATLAB/Simulink.