11.8 A 5A 94.5% Peak Efficiency 9~16V-to-1V Dual-Path Series-Capacitor Converter with Full Duty Range and Low V.A Metric

As the power demand of computing cores grows explosively, large conversion ratio, high efficiency and compact 12V-to-1V DC-DC converters become increasingly important. Double step-down (DSD) converters [1]–[2], also known as series-capacitor converters, offer a promising solution using the capacitors to reduce the high voltage stress and to extend the duty cycles, however, at the cost of multiple inductors and limited duty cycle range (D
$<$
50%). To break the duty cycle limit, some previous work employs extra power switches or capacitor cross-connected (CCC) design for D>50% operation during a short transient period [3]–[4]. The steady-state operation, however, is still not allowed and limits the transient response and output voltage range. Besides, DSD converters suffer from limited efficiency since the switch voltage stress is still high. To quantify the switch losses of the DSD and the proposed work, the popular V.A metric is adopted here [5], which identifies the overall converter conduction and switching losses with the lower V.A value indicating lower losses. In this work, we propose a dual-path series-capacitor converter which shows inherent full duty cycle range, low V.A metric and excellent efficiency even with only one inductor. Compared with the conventional DSD converters, the capacitors in this work not only reduces the switch voltage stress, but also form a capacitive current path. Therefore, both the switch voltage and the current stresses are alleviated, leading to competitive converter V.A metric and efficiency over wide output voltage and load ranges. In addition, the capacitor charge balance is easily achieved and, hence, inherent full duty cycle operation is obtained.