DC–DC Converter With Digital Adaptive Slope Control in Auxiliary Phase for Optimal Transient Response and Improved Efficiency

In this paper, a digital adaptive slope control technique is presented to improve the dynamic response of a current-programmed mode (CPM) buck converter employing a low-cost auxiliary phase. The advantages and drawbacks of the existing analog and digital nonlinear control techniques are discussed in detail. The benefits of the proposed control scheme include superior voltage drop and settling time, adaptive slope control to accommodate a range of auxiliary phase inductor values, and on-line calibration to compensate for tolerance in the main phase and auxiliary phase inductance. The proposed technique is experimentally verified on a 500-kHz, 10-2.5 V CPM buck converter prototype. Charge balancing and optimal transient response are achieved for a range of positive and negative load steps. Operating the auxiliary phase under light-load condition is also demonstrated to further justify the use of the auxiliary phase. Compared to a representative single-phase converter, the proposed system not only has over two times improvement on the voltage drop and three times lower steady-state voltage ripple but also achieves approximately 2% heavy-load and 10% light-load efficiency improvement. The impact of the auxiliary phase operation on the converter's dynamic efficiency is also evaluated at different load step amplitudes and frequencies.