Digital controller design for buck converter with the reduction of phase transition and output voltage oscillation under transient state

The main theme of this paper is to present a new digital controller design method for buck converter. The presented digital controller is aimed at reducing the phase transition in frequency domain and output voltage oscillation under transient state. These special features can be achieved by taking both transfer function of control to output and output impedance into consideration. The zeros of controller are selected neither real nor pole-zero cancellation. As compared to previous approaches which determine the zeros of controller based upon pole-zero cancellation or simple real zeros, the presented method selects these zeros according to the quality factor of plant. As the quality factor of compensator zeros are in the range of 0.3 to 0.5 times of quality factor, the phase transition and the oscillation of output voltage under transient state can be reduced significantly. Experimental results derived from an FPGA experimental digital-controlled buck converter with switching frequency up to 200 kHz are presented for confirmation.