Comparative Effects of Gate Pulse Shifting on CCM/DCM Boundary Current in CI-SIDO Converters

The demand for various DC voltage levels has neces-sitated single-input multiple-output (SIMO) systems, efficiently replacing various single-input single-output (SISO) converters. Among these, single-input dual-output (SIDO) converters are notable. This paper focuses on coupled inductor single-input dual-output (CI-SIDO) buck, boost, and buck-boost converters. There are two distinct operating modes of DC-DC convert-ers: continuous conduction mode (CCM), where the inductor current stays above zero for the entire switching period, and discontinuous conduction mode (DCM), where the current falls to zero before the switching period concludes. Converters are typically designed for CCM, simplifying control by making the input-output voltage relationship load-independent. However, converters may enter DCM at light loads, making the voltage relationship load-dependent. Analyzing the CCM/DCM boundary is crucial for maintaining CCM operation. Existing methods for determining boundary conditions for SISO DC-DC converters focus on calculating CCM/DCM boundary conditions, where the average inductor current at this boundary determines the critical inductance needed for CCM operation. Lowering the boundary current value broadens the load range for CCM and reduces the required critical inductance. Relative gate-pulse shifting is introduced to minimize inductor current ripples in CI-SIDO converters by time-shifting gate pulses without additional circuitry. However, its effect on CCM/DCM boundary currents has not been explored. This paper investigates boundary inductor currents in CI-SIDO converters by relatively time-shifting gate pulses. The impact of gate pulse shifting on CCM/DCM boundaries in CI-SIDO buck and buck-boost converters is examined, and a comparison of critical inductances for the same boundary currents is presented for all three converters. The analysis is verified with MATLAB/Simulink simulation results.