Study On Control Method Of Single-inductor Dual-output Buck Converter

With the proliferation of battery-operated portable systems, minimizing power consumption and reducing external components have become two of the most important design demands. For this application, single-inductor dual-output(SIDO) switching converters could be adopted to support independent dual outputs while requiring only one off-chip inductor, relative to traditional multiple-output power supply with high-frequency transformer and other combinations of module output, which reduces the number of external components required for the integrated converters, thereby reducing the volume of supply and power costs. therefore, single-inductor dual-output Buck converter gets more and more attention and rapid development.First, several commonly used Buck converter control methods are briefly introduced, and the advantages and disadvantages of the methods are compared to study. On this basis, extended to multi-output switching power supply control technology, two kinds of inexact adjustment and precise adjustment of multi-output switching power supply topology are researched, the contrastive analysis to the dynamic performance of the two kinds of topological structure of the output voltage are made, and focusing on the principle and work mode of single inductor dual output switching power supply.Second, the control methods of existing SIDO buck converter are systematic analyzed. Including voltage-control method in continuous conduction mode and the method of time multiplexing control in discontinuous conduction mode. In view of the problems existed in the above two methods, a peak current control method of SIDO DCM buck converter has been proposed. The same as the time-multiplexing control method, The peak current control method has the advantage eliminating the cross-regulation of output voltage. And compared with the two previous control methods, when the load parameter changed, the output voltage ripple of the peak current control method is much lower. After that, with the help of MATLAB/Simulink platform, the simulation of cross regulation and ripple for output voltage are compared to analysis in the three kinds different of control methods when the parameter of load changes. The simulation results have important guiding significance for the SIDO buck converter to select the appropriate control method for different power supply occasions.Finally, based on the time-multiplexing voltage control methods of SIDO DCM Buck converter, we propose a suitable improved control method of SIDO DCM Buck converter—The method of feed forward voltage-mode controlled, which uses triangular carrier following the input voltage as feed-forward input, so that the fluctuation of the input voltage can be quickly reflected in the change of the sawtooth carrier. The simulation and experimental results show that the SIDO DCM Buck converter under the improved method can not only achieves two independence and stable output voltage, no cross-regulation, but also has a strong ability to inhibit the input voltage fluctuations. When the input voltage transitions, the output voltage ripple is no transient overshoot and oscillation phenomenon.