To improve the VRM's step-up response speed

the optimal loading of a traditional buck converter was analyzed

based on that the dual-input buck converter was proposed

then its steady work process and the optimal loading operation process was described.The additional power switching conditions were given by the optimal loading threshold.Finally

the comparative simulation study was carried out for both.The simulation and experimental results show that the dual input buck converter is faster response speed and smaller output voltage drop amount than the traditional buck converter

and the simple structure

easy to design and implement

suitable as the VRM main circuit.