Research And Design Of Low Ripple Dual Output Switched-Capacitor DC-DC Converter

With the advent of the information age,various portable mobile terminals have come into people's sight,such as tablet PCs,electronic paper books,multifunctional handheld computers.Mobile terminals usually require a low and very clean power supply voltage,therefore,high performance power converters are needed to power them.At the same time,due to the miniaturization of mobile terminals,power converters have gradually developed from the board level to the chip level,in line with the development trend of miniaturization of portable mobile terminals.Mobile terminals usually use DC-DC power converter.Switching capacitance type DC-DC converters uses capacitors instead of inductors as intermediate energy storage elements to realize energy transfer in contrast to the inductive type DC-DC converters,the area of PCB board can be greatly reduced,and the effect of electromagnetic interference is significantly reduced,which is more suitable for the application of noise sensitive electronic products.However,the output ripple of capacitive dc-dc converter is large,and the overall system efficiency is not high.How to solve these two problems is the key to improve the performance of capacitive dc-dc converter.In this thesis,based on the SMIC 0.18 um CMOS process,a low output ripple switching capacitor type DC-DC converter with dual output has been designed.At first,through theoretical analysis and modeling,the factors affecting the output ripple and system efficiency were analyzed.Then,in the system design and the most appropriate parameter size is found through the compromise of various factors.At the same time,by combining use of two kinds of ripple suppression technology,the magnitude of output ripple voltage has been controlled within the acceptable range.Also based on the pulse skipping modulation strategy,an additional output has been added to enable the system to independently control the circuit.The composing modules of the system,including reference voltage source?switching capacitor array?feedback module?digital module etc.,have been designed in transistor level.,and the module simulation and optimization has been carried out.After completing the module design,the system has been set up for simulation.The output ripple is less than 2mV in the post-layout simulation,and the maximum system efficiency is higher than 90%,meeting the expected design requirements.