Research And Design On Mode Control And Segment Technology Based On Buck Converter Under Light Load

With the fast development of multimedia terminals and portal electronics in nowadays, it makes the integrated circuits more highly integrated and with lower power consumption. At the meantime, power management ICs design is faced with much more challenges. With the limitation of battery capacity, extension of battery life becomes an important issue. Among the many power management unit chips, DC-DC converters get more attractive and practical for its high efficiency. Therefore, it is quite meaningful to study the efficiency of DC-DC converter. This article aims to improve DC-DC converter’s efficiency under the wide load range and have some research on light load mode control and segment technology based on BUCK converter.Firstly, the development and trends of DC-DC converter are introduced in this article. Then the fundamental topologies of switching power supply and common modulation mode are presented. Based on analyzing two methods of improving efficiency under light load, the conducting losses and driving losses of power MOSFETs are analyzed in detail. According to the analysis above, design of an DC-DC converter with adaptive segmentation output stage operating in dual-mode is presented. It is emphasized on the design of duty detection circuit which can quantify the load current in DCM. According to the quantification result, the adaptive segmentation of power MOSFETs is achieved. Furthermore mode transition and circuit implementation of PSM modulation are described in this article. Finally, a detailed simulation of characteristic parameter of this proposed DC-DC converter is showed, and layout design is presented at last.The layout of this chip design is in area of 1.2mm×1.25mm. Under 0.13 μm CMOS process, the final simulation results show that DC-DC converter designed in this paper can improve the efficiency by mode switching and adaptive segmentation. The efficiency under full load can be maintained above 70%. Meanwhile compared with converter without segmentation, the maximum efficiency enhancement of the converter with adaptive segmentation reaches 5.3% under a 15mA load, which proves the validity of this design.