Decoupled Voltage-Mode Control of Coupled Inductor Single-Input Dual-Output Buck Converter

The coupled inductor single-input dual-output (CI-SIDO) dc-dc converter is an alternative to multiple parallel dc-dc converters for applications requiring multiple regulated supplies. CI-SIDO exhibits the merits of reduced ripple, small volume, and high efficiency. However, the coupling of inductor currents results in coupled outputs leading to cross-coupling and cross-regulation problems. Due to cross-coupling of the output voltages, the compensator design becomes complex. This article proposes a decoupled voltage-mode control to address the issue of cross-coupling of output voltages. It also demonstrates the stability boundary for controller design. The proposed controller is designed using simple analog Type-II compensator. A systematic compensator design procedure is also developed. The proposed controller decouples the output voltages, ensures good stability margin as well as good load regulations and audio-susceptibility. The design is verified through simulation and experiments. The experimental results shows that the decoupled control significantly suppresses the cross-regulation with fast transient response speed for the load, input, and reference variation. A transient performance comparison of proposed decoupled voltage-mode control for the CI-SIDO buck converter with state-of-art control methods for the single-inductor SIDO buck converter is also presented.