Design Of A Buck DC-DC Converter With Ultra-low Power Consumption

With the development of microelectronic technology,the integration of switch mode power supply chips has been improved dramatically.DC-DC converters used in portable devices and mobile internet equipments are increasely required to have ultra-low power consumption,high efficiency and small size.Improving these characterisitcs have become the most important research issues of DC-DC converter.The purpose of this thesis is to study how to decrease the power comsumption and improve the conversion efficiency of a DC-DC converter.A Buck DC-DC converter with V_in=2.8⁶V,V_out=1.8V,the maximum output current I_max=300mA,the output voltage ripple V_ripple<3mA,and the maximum conversion efficiencyη_max≥90%is designed and verified by CAD simulation.This converter can be directly powered by button cell（3.3V）or USB（5V）.For high conversion efficiency,a power distribution module should not be included in the converter.So,each module in this chip must be adapt to the 2.8⁶V wide power supply voltage.The synchronous rectification technology is used to realize lower power dissipation of the freewheeling circuit.The static bias current of each module in the DC-DC converter is extremely low.The closed-loop compensation circuit is used to reduce the sensitivity and improve the dynamic response of the system.The DC-DC converter is designed and simulated based on a 0.18μm CMOS process.The following results are verified:The output voltage is stable at 1.8V within2.8V⁶V input voltage.The line voltage regulation is 3.75mV/V.Under 3.3V and 5V input voltage,the temperature coefficient of the output voltage is 32.13ppm and49.42ppm,respectively.The maximum conversion efficiency is 90.06%,and the output voltage ripple is less than 0.77 mV.Under 3.3V and 5V input voltage,the load regulation is 0.27μV/mA and 0.66μV/mA,respectively.The CAD simulated results verified the validity of the design.